US2416918A - Color television system - Google Patents

Description

March 4, 1947. A, N, GOLDSMlTH 2,416,918

COLOR TELEVIS ION SYSTEM Filed Nov. 29, 1943 5 Sheets-Sheet 2 aqred/ 6,0 INy/v TOR.

/4 TTOP/VE )f Mardi 4, 1947, A. N. GoLDsMm-l 2,416,918

COLOR TELEVISION SYSTEM Filed Nov. 29, 1943 3 Sheets-Sheet 3 A TTORNE Y Patented Mar. 4, 1947 olv-rice COLOR TELEVISION SYSTEM Alfred N. Goldsmith, New York, N. Y., assigner to Radio Corporation of America, New York, N.' Y., a corporation of Delaware application Noyembe 29, rara-serialNogsiairs (ci. 17a-5.2)

Claims.

This invention is directed to television systems; and particularly is concerned with methods and systems for individually controlling the current balance or primary color gain for either the socalled cyclic or sequential color television 'systems on the one hand, or for simultaneous color television systems on the other hand. Also, the invention is directed, with equal applicability, to cyclic or simultaneous color photography. A

In the past, various systems for accomplishing such results have been provided primarily through the useof various forms of electric circuits and controls therefor. In some oi' these forms of arrangements, particularly in the. case of threecolor sequential television systems, provision has been made for varying the gain of the amplifiers responding in such a manner as to transmit signais representative of the several selected primary or component colors.

The prior art has accordingly suggested that suitable controls for variation of amplifier gain to accomplish a color balance may be achieved through the use of systems utilizing but a single amplifier where the gain of a variable mu type amplifier unit is varied, preferably in sequence, in accordance with a primary or component color instantaneously being transmitted. Again, it has been proposed to provide independent amplifiers for amplifying the different selected primary r v component colors, which amplifiers are operated in sequence to coincide with the transmission color instantaneously being utilized, -and provision'is y then made for switching the amplifier control from the light sensitive translating element to the amplifier by way of suitable vsignal attenuating networks caused sequentially to become operative through the use of appropriate commutation systems, for instance.

Other means for accomplishing and achieving a color balance according to purely electrical methods have already been provided. However, it has beenrfound that many advantages are to be obtained through the avoidance, as far as possible, of electrical controls, in that such electrical controls frequently tend to introduce into the composite system electrical noise which tends to distort or otherwise objectionably ailect the transmission. Further than this, it has been found that such electrical systems require, for their eiilcient operation, extremely delicate adjustment of the switching equipment and its operation, and require a, high degree of accuracy in the phasing between the switching or commutating devices and the corresponding' primary color picture transmission sequences which requires additional electrical equipment such as would necessarily be involvedin methods of this nature.

According tothe present invention, there is set forth a system of color balance control which is primarily optical in its nature and which involves a specialized and appropriate type of color iilter irig instrumentality which will be suitably assoelated with the objective lens system of the television camera tube together with suitableA and requisite means for providing either local or remote control of the illters or filtering aggregate relative to the optical system. A system of this nature, it will be appreciated, is free from many of the inherent diillculties of a system which is purely electrical in its nature and from one wherein the individual primary color video amplifier channels are adjusted to a variable degree of gain to secure the desired color balance irrespective of all variations which can be introduced from electrical noises, changes in illumination with change in the illuminant color temperature, changes in circuit power supplies or operation, and other variations of various characters.

It is known that for satisfactory tricolor television of any type now utilized, the individual pri- .mary color or component color transmissions must be suitably balanced with respect to one another. Such requirement, of course, implies that the black lshadows shall in fact be of a neutral black when received on an appropriate colortelevision receiver in correct adjustment, and,'further, it implies that a tintless white shall similarly correspondingly be reproduced, with in termediate brightnessv grades of course being reproduced as grey, all without any color tinge or hue. the color range or. reproduction range of the system should be accurately reproduced as well.

However, generally speaking, therelis a certain limited range of color which is not correctly reproducible by any presently known additive color system of usual design, such as those colors which lie outside the triangle formed between the three points defining the primaries used in the system 'and shown by the usual-red and green chromoticity diagram. l

. It hasbeen well known that the color balance of a color television transmission can be disturbed-by numerous factors as above suggested,

and for'rep'etition purposes, these can be con sidered as changes-.in thelcolor of the illuminant ofthe objects being televised, changes in the operation oionel or; more of the primary color video ampliers, an'yincidental errors in adjustment, and, still-iurthen' changes in the color sensitivity of thecamera tube (usually a mosaic stor-l age' tubeijwhiclr may* occur as'these tubes are used over a periodici time and progressively alter.

Generally speakingfthe restoration of the cor- Correspondingly, any other colors within rect color balance of the image transmission, as above described, is most conveniently accomplished with the aid of visual observation on a monitoring assembly, with the skilled observer or monitor adjusting the relative intensities of the transmitted primary or component color images until the desired color balance effect is achieved. In a sense, this process of monitoring becomes somewhat analogous to the process of monitoring a sound broadcasting program on a monitoring loudspeaker. However, for the purpose of achieving the results desired from monitoring or adjusting to provide the desired color balance, the present invention incorporates only optical instrumentalities, except for the controls thereof which are to be effective to make adjustments in" the'color balance set-up.

Such optical adjustments provide, according to the present invention, for the positioning of one or more suitable filter elements, which will herein be termed a diversified color fllter, in such aA position relative to the television camera that the objective of the lens system of the camera is incapable of forming any image of the objects lying in the filter plane upon the light sensitive camera tube or mosaic. Further, the invention is so contemplated that provision is Amade for locating the diversified color lter system in such relationship to the light rays of the image which is to be cast upon the light sensitive camera tube that light rays from each point of the object must pass through every point of the diversified color filter system on their way to the image forming target or screen or mosaic of the camera tube.

Accordingly, the present invention contemplates the use of suitable diversified color filter systems as have a filter area suiliciently great orthogonally to the image forming light beam to permit the entire beam to pass through the filter, irrespective of any necessary and desired range of adjustment of the position of the lter, and, further, that the diversied color lter shall be located near, or actually in, the lens system which directs the light of the image upon the camera tube of the television system and at a distance from the nearest nodal point of the lens system which is small with the comparison of the corresponding distance therefrom ofthe object or image respectively.

In connection with simultaneous color television, the system contemplates the utilization of suitable diversified color filter devices in combination with image scanning or camera apparatus, with provision being made, as before stated, to locate the planar diversied color filter in such a position relative to the 'scanning instrumentalities that the entire light beam passes through the lter and yet the filter is so placed that it is not imaged upon the camera tube target or mosaic plane.

Color photographic systems. of either the cyclic or the sequential type, embody, generally speaking, the same general forms of arrangements as the broadly related television systems. Generally speaking, for cyclic color photography processes the general arrangement of the diversified color lter and the color selective disc is substantially similar to that of the sequential or cyclic television systems, insofar` as the arrangement of each of the diversified color filters and the color selection discs, relative to the optical system and the light responsive target or film surface, are concerned. In this connection, however, Special provisions are made for monitoring which are slight departures from the de vices normally used in conlleftioli With 4 television systems, in that, for any photographic system, visual monitoring devices are desirable.

Simultaneous color photography systems also may be provided with the diversified color filter arrangements in the same general manner as for television systems. For simultaneous color photographic processes, use may be made of well known tricolor or bicolor or multicolor separation cam` eras, or the color separation may take place by virtue of the type of film used for recording. One

type of such film which is suitable for such purpose is that known in the art as Kodachrome." The simultaneous color photographic process is generally similar to the simultaneous color tele--A vision process, except again as to the monitoring system. The color separation disc is usually not required in simultaneous systems. Stationary separation lters are also usable in the color photographic process and these may be physically presenter they may be present, for instance, in effect, though usually to a limited extent only, by the color sensitization of the emulsion layers or components. In what is to follow, further reference will be made to the monitoring features.l

In the foregoing discussions, reference has been made to va diversified color filter and, within the meaning of these specifications, a. filter of this character will be defined as one wherein the filter area includes areas of more than one and the same color and where, accordingly, the complete illter eiect results from the composite or conjoint effects of the color filtering of all of the filter areas of diierent colors.

Various methods of accomplishing the color balance effects may be relied upon and, within the scope of the present disclosure, there are included, among the objects thereof, those of producing, by purely optical methods, suitable color balancing in color television systems of, for example, the tricolor type.

A further object of the invention is that of producing an optical mechanical method of obtaining the requisite color balance as well as, in many instances, an optical electrical control and method for achieving such color balance with the actual color balancing effect resulting from purely optical adjustments.

A further object of this invention is that of avoiding added electro-mechanical or electrical commutating equipment as a portion of the usual color television system where adequate adjustments have been made for achieving a color balancing throughout the range of transmission.

A further object of the invention is that of providing optical equipment by which color balancing effects are achieved and which equipment can readily vbe controlled and operated from a remote source to achieve instantly an adjustmentV of color balance to modify transmission effects.

A further object of the invention is that of providing a diversified color filter assembly which may be positioned relative to the television camera tube and its optical system in the manner above and blue-are usually selected in television operations for convenience. It will be understood and appreciated. however, that some variance in the selection of these colors is possible since the colors selected, generally speaking, may be any three colors which are so chosen that no one of them can be reproduced by the other two alone. Accordingly, it is possible to choose as to the primary or component colors any three colors, preferably widely spectrally separated, which would vbe represented by any three points in the I. C. I. (International Committee on Illumination) color triangle area which are as far apart as practicable so as to make possible that the gamut or range of the reproducible colors lies within the triangle formed by the primary or component colors as theapices. These colors, accordingly, should encompass as large a part of the I. C. I. color triangle area as practicable, which color triangle comprises all real colors.

A further object of the invention is that of providing a color balancing diversified color filter capable of use in combination with suitable infra-red filters in the path of the image forming beam and as a fixed adjunct in connection therewith, so that the infra-red forming beam will prevent false color effects which vfrequently result from the sensitiveness of the usual camera tube mosaic of the Iconoscope or Orthicon type to infra-red light, picture haze, or even possibly, lack of' sharpness of focus of the resulting optical image directed thereupon.

Other objects and advantages of the invention are to provide a color balance control system which functions with complete freedom of'introduction of any electrical noise into the transmission system and thus to provide a system which is capable of increasing, to a substantial extent, the accuracy and fidelity of transmission.

At the same time, it becomesa further object of the invention to provide a color balancing control system which is relatively simple in its arrangement and construction, as well as to provide a color balance control system which may readily be adjusted to compensate for varying changes in transmission characteristics.

Another object of this invention is that of providing a system of color balance control which is generally applicable to use in both television and photographic arrangements and usable in these arrangements whether or not the process is carried forward in either a sequential or simultaneous manner.

Other objects of the invention are those of providing a color balance control system of increased efficiency, relative cheapness of installation, and one which is easy and efficient to control.

-Other objects will of course suggest themselves to those skilled in the art when the following specification and the claims appended are considered in the light of the following drawings, wherein,

1 Fig. 1 shows schematically one arrangement of the system to illustrate the general relationship between the scanning or camera tube and the color filter disc and the diversified color filter;

Fig. 2a illustrates one arrangement of the diversified color filter relative to the optical system of Fig. 1;

Fig. 2b illustrates a modification of Fig. 2a;

Fig. 2c illustrates a further modification of Fig. 2a;

Fig. 3 is a schematic representation of the general arrangement of the diversified color filter through Fig. 10 looking in the direction of the Y arrows; r

Fig. 12 represents, in conventional schematic manner, one suitable form of electrical circuit for controlling the filter adjusting apparatus from a remote point;

Fig. 13 is a conventional representation of one suitable form of diversified color filter adjustment particularly suited to the adjustment of' filters of the type shown by all of Figs. 4 through '7 relative to the camera tube and the optical system thereof;

Fig. 14 is a section through Fig. 13 along the line I4-I4 thereof looking in the direction of the arrows; and,

Fig. 15 is a schematic representation of one suitable form of control for providing adjustment of the diversified color filters of the types shown by Figs. 8 and 9 relative to the scanning or camera tube and its optical system.

Now making reference to the drawings and first to Fig. 1 thereof, the light of an image II is directed through an optical system I3 of any conventional character to reach the light sensitive plate or mosaic target I5 of a television camera tube Il. The television camera tube may be of any known character such, for example, as those tubes known in the art as the Iconoscopes or Orthicons, or the tube, on the other hand, may be of the non-storage type such as that, for example, which is known in the art as the Dissector tube. In a three-color sequential type system. the light thus directed upon the mosaic or target electrode IB of the camera tube I1 is passed through a light or color filter disc I 9 which is appropriately rotated on a shaft 2i by means of a suitable drive motor 23 which rotates at any desired speed such that the driven disc rotation is appropriately related to a desired field frequency of image transmission.

In a tricolor system the filter disc I9 is usually divided into three equal-area components or sectors so as to pass or transmit light of chosen component or primary colors, such as the red, the green. and the blue. and thus, as the disc I9 is rotated, the light of the image is directed to the camera tube mosaic through successively changing different color areas to produce the three component color transmissions in sequence. It is to be understood, of course, that the rotary color component disc I9 is placed in conventional relationship to the optical system I3 and the camera tube I1 and/or its mosaic or light responsive target electrode I5, as is well known fields, which are conventionally represented as being produced by the defiecting coils 29, although it is to be understood that electrostatic deflection may be used as an alternative, or that the deflection may be under the control of a combination of electrostatic and electromagnetic means. Preferably, there is an interlock as to frequency relationship between the horizontal and vertical deflecting fields (which cause the cathode ray beam 25 to traverse the target I5) and the rate at which the filter disc I9 is rotated so that one traverse or field scanning is caused to occur for each component color of the filter disc revealed to the camera tube. The video signals from the camera tube mosaic I which result from scanning it in known manner are then applied according to Well known means to a video amplifier 3| for amplification purposes.

The output signal from the video amplier 3| is then fed to an output or load circuit 33 to be transferred to further amplifiers, modulators and transmitters, and then to be distributed to suitable receiving points Via Wire line or radio link communication channels or by combinations of such channels.

In accordance with the arrangement of the present invention, there is positioned intermediate the optical system I3, which is arranged to focus the light of the image II upon the camera tube mosaic I5, a filter assembly 3 5 which is herein to be termed, for reference purposes, a diversified color filter. As is evident from the schematic positioning of the diversified color filter element 35 in the showing of Fig. 1, this filter is located near or approximately adjacent the lens system, and at a distance from the nodal point of the lens system which is small in comparison with the distance therefrom of the object I I or the image thereof which is cast upon the mosaic I5 depending upon whether the lter 35 is on the object side or the image side of the lens respectively.

To provide for adjustment of the filter to obtain the desired color balance, suitable control arrangements have been indicated by way of the filter control cables schematically illustrated at 31. In order that the filter control cable may be so adjusted a schematic representation of one manner of control has been shown by Fig. 1 of the drawings. In this arrangement, a monitoring system is conventionally represented at 24, and this monitoring system then receives output signal energy from the video amplifier 3|, for example, so that in the monitoring system 24 a color replica of the outgoing video or image signals is reproduced. It is, of course. to be understood that the monitoring system will comprise suitable image reproducing tubes of the cathode ray type for instance, as well as a suitable filter disc assembly, forming a counterpart of the disc I9, which monitor disc, although not shown, will be understood to operate synchronously and cophasally with the disc I9 and preferably may be driven with a synchronous motor operating from the same power supply line as the motor 23. To adjust the diversified color filter assembly under such circumstances, the operator at the monitoring system may adjust various color control elements 26, 28 and 30 which are schematically illustrated, and which may then serve in appropriate manner to supply the controlling effects via the filter control cable 31 to adjust the diversified color filter assembly 35 relative to the optical system I3 and the camera tube Il, and, more specifically, relative to the optical axis of the lens I3.

These cables may be of various types and any mechanical or electrical control may be used, generally speaking, for the purpose. The main result to be accomplished by the control cable conventionally represented at 31 is that of providing control forces whichare sufficiently powerful and free from back lash to carry out the control promptly -with action sutliciently accurate so that motions of the controlling instrumentalities are capable of positioning the diversified color filter in any desired arrangement. To this end, various means may be utilized, among which may be included controlled Selsyn or Autosyn motors, controlled torque-transfer cables and the like, which are caused to drive or rotate various mechanical means serving to move and position the filters relative to the 0ptical system and the camera tube.

While it has not been shown as a specific Dart of the arrangement of Fig. 1, solely for the purpose of convenience, it is to be understood that as an inherent portion of this invention use may be made at all times of an infra-red filter as a fixed adjunct with the infra-red filter being located in the path of the image forming beam. Filters of this character are frequently desirable in order to prevent false color effects which are apt to result from the sensitiveness of the camera tube mosaic or target electrode I5 to infrared light, picture haze and possible lack of sharpness of focus of the resulting images. Filters of this type, however, per se, form no specific part of this invention and have been known in both the television and the photographic arts for a considerable time period. They are mentioned herein merely for, and primarily for, the purpose of completeness of disclosure.-

If reference is now made to the showing of Fig. 3, the image II is positioned along the optical axis 39, 4U of the schematically represented objective or lens system I3. Accordingly, it can be appreciated that the image of the object II will be formed in inverted manner between points 4I and 42 on the surface I5, which is assumed, for reference purposes, to be the camera tube mosaic. The relative dimensions of the object and image respectively may differ widely from those shown in Fig. 3 which is to be regarded as illustrative. Considering this arrangement, light from the point 43 of the object or subject II will form rays conventionally represented at 45, 41 and 49 which, in their totality, strike all points of the anterior surface of the optical system I3. The same conditions apply to the rays 46, 43 and 50 which are assumed to emanate from the point 44 of the Object. It is clear that the diversified color filter element 35 must pass the entire light bundle from each point of the object, insofar as such bundle passes through the lens or objective I3, and is effective in the formation of the final image on the mosaic or target electrode I5. Furthermore, the diversified color filter 35 must also be placed in such a location relative to the lens system or objective I3 that it cannot be, or is not focused thereby upon the image plane or mosaic surface I5.

With the arrangement as Ishown by Fig. 3. Iwherein the diversified color filter element 35. which is of sufiicient area for the purpose of suitable adjustment, is placed in close juxtaposition to the anterior surface of the lens or objective I3, these conditions will be satisfied.

If reference is made to Fig. 2, various com- 9 binations of a group of aiternativelyacceptable diversified color filter positions are shown; In the arrangements of Fig. 2, the optical system is composed of schematically represented compo- 'nents 5| and 53 with the diversified color filter element 35 placed in various positions relative to this optical system.

In the arrangement of Fig. 2a, the diversified color filter 35 is placed close to the anterior surface of the lens. As shown by Fig. 2c, the color filter 35 may be placed, with equal eectiveness, close to the posterior surface of the lens. In the arrangement of Fig. 2b, the diversified color filter 35 is placed intermediate the' components 5| and 53 of the lens, it being assumed, in each instance, that the light path through the lens system to focus an image of the object or subject Il upon the camera tube mosaic i5 is as shown in the direction of arrow. The arrangement of Fig. 2c, as above depicted, is that vwhich corresponds to -the illustrated modification in the schematic representation of Fig. 1.

If reference is made again to Fig. 1, it will be understood, of course, that the adjustment of the diversified color filter 35, which is conven- 'andere the images .may be developed through single tubes utilizing a plurality of vindependent electron beams to produce the different component color images at different sections of the tube target. An exampleof the use of independent tubes whose images are brought to registration is found in the Alexanderson Patent No. 1,988,931, granted January 22, 1935. An example of the independent color images being produced upon different sections of the'tube target and then brought lto registration is found in the Schlesinger tionally represented as being accomplished through the filter control cable 31, shall be preferably in accordance with the various arrangements of control, and particularly those forms of arrangements which are shown in the later to be described modifications of control systems as set forth particularly by Figs. 10, 11, 13, 14

and 15 of this disclosure, although it is to be understood that the illustrated forms are merely representative of various forms which the system may assume. A

Further, while not specifically illustrated in the present disclosure, the diversified colorlter system is equally applicable to simultaneous multicolor television arrangements which might be exemplified, in one sense, by applicants presently pending application. Serial No. 455,556,

filed August V21, 1942. In a system of the charform disclosed in any of the arrangements of Fig. 2 hereof, for instance), and thereafter the light may be directed to suitable independent scanning or camera tubes for the scanning of the independent component or primary color images. Under such circumstances, the light of the image is passed through or reflected from suitable halfsilvered mirror surfaces, for instance, to be directed upon independent scanningy or camera tubes through suitablyv positioned fixed filters of the selected primary or component colors, so that an image of a like size and aspect ratio is directed upon each of the independent scanning or camera tubes. The scanning pattern and scanning detail in each tube is carried on simultaneously and. in identical manner through lthe use of a plurality of separate tubes toreproduce the desired color` image signals for transmission. The images are reproduced at receiving points in known manner through the use of a plurality ofseparate tubes lWhose images are brought into registry on a viewing screen, or

the latter patent, a two-color system is specilically illustrated although the patent makes mention of the possibility of use of the system as a three-color arrangement.

Further, for simultaneous multicolor arrangements, the light path may be as above explained and the separate images, representing the chosen component colors,.may then be directed along independent channels, as exemplified, for instance, by the Hefele Patent No. 2,037,166, granted April 14, 1936, with it being understood, of course, that the diversified color filter herein disclosed makes unnecessaryA the adjustment of the amplification level in the diierent signalling channels to compensate for any differences in response of the .system due to different sensi,.- tivities of different light responsiveelements to different colors, for in applicants present disclosure the compensation is taken care of optically and without introducing electrical noise or other disturbances into the outgoing signal by is intended to .include any .form of composite color filter which, through alteration of its position in relation to the center of the image form-- ing light beam, and therefore with reference to the boundary vof the active image forming portion thereof, acts effectively as a variable color filter to enable the desired color balancing effect to be achieved.

In the schematic arrangement of Fig. 4 for instance, the diversified color filter 35 consists of three separate areas, conventionally desig.. nated at V55, 51 and` 59 and also shown, for example, by the letters R, G and B respectively, which are intended to represent the component or primary colors, red, green and blue, selected for the transmission. The sections 55, 51 and 59 of the diversified color filter 35 are respectiveLv a rather pale blue, a rather pale red and :a pale green which," for illustrative purposes,

may be assumed as being the primary colors, although this is not necessarily a limitation in the system.

The light absorption from the three areas 55, 5l and 59 should preferably be equal to their effect on the resulting brightness on the transmittedimage, so that changes in color balancing In the arrangement of d, the three separate filter sections forming the red section 55, the green section 51 and the blue section 59 function as light absorbing color filters and are used primarily for color balancing under practical conditions of normal variations from balance which can be obtained, for instance, by adjustment of the filter, so that the color balance is maintained at a moderate value. Unless there are unusually large changes in the illumination of the televised objects, or similar large changes in the color balancing which is required, the filter light absorptions can be maintained at quite moderate values and, for instance, within the range of about to 20% light absorption. However. it ls to be understood that there is no absolute limitation on the light absorption of one or more color areas of such a diversified color filter, although excessive absorption (such as in excess of about to 30%) is to be avoided. However, in the wedge type filter, it is possible to provide higher density or color absorption at the outer or peripheral portions of the color wedges, as in Fig. 8, for example.

With the arrangement of Fig. 4, when the axis of the lens is somewhere near the jointure of the red, the green, and the blue areas. the effect of the filter, as a whole, is small as far as color balancing is concerned. In fact, it is possible, with this arrangement, where, for instance, the optical axis is along the line perpendicular to the plane of the drawing and passing through the point 6i for instance, to establish such a position of the filter that its effect is substantially negligible. However. if the filter is moved to the right or left, as indicated by the bottom arrows on the drawing, the color balancing effect will be toward the yellow or toward the blue respectively. If, on the .other hand, the diversified color filter assembly is moved up or down, as indicated by the arrows adjacent to the side of Fig. 4, the color corrective or balancing effect will be toward the red or the green respectively. Thus, any desired change in the chromaticlty of the light reaching the camera tube through the diversified color filter 35 can be secured if it lies within the range of colors obtainable by a balancing lter 35 which has a specific saturation or primary color absorption for each of its color areas.

In the arrangement of Fig. 4, it is to be assumed that the red, the green, and the blue areas 55, 51 and 58 are all of substantially uniform saturation or light absorption over their entire areas, so that a lateral or horizontal motion of the filter to the left will bring more blue before the camera tube mosaic, or to the right will bring more of the red and the green and less of the blue before the camera tube mosaic. Likewise, a downward motion of the lter 35 will bring more oi the red and less of the green and an equal amount of blue before the camera tube mosaic', while an upward motion of the lter 35 will bring more of the green and less of the red, and yet retain an equal amount of the blue before the camera tube mosaic. Combinations of horizontal and vertical motions will provide for further variations of these adjustments.

In the arrangement of Fig. 5, in contrast to that shown by Fig. 4, the areas 53, 55 and 51 of the lter, which are assumed to be the red, the green, and the blue illter areas respectively, are formed according to the same shape or configuration as those assumed for Fig. 4, but are representative of the nature of color wedges, that is, the color becomes increasingly intense toward the outer edges so that there is increased absorption or saturation in the fashion indicated by the drawings, where the lightest area of the filters is over the areas of lightest shading in the figure. Such color wedges, of course, are readily made by well known methods using, for example, dyed gelatine flowed between two pieces of glass or other transparent material which forms an air wedge between their mutually inclined surfaces. A filter of the character shown by Fig. 5 has the advantage, over the arrangement of Fig. 4, that it can be nearly colorless or light absorptionless toward the center, that is, toward the jointure of the red, the green, and the blue areas, and yet have pronounced absorptions and corrective color balancing effects toward the outer portions of the areas 63, 65 and 61 for the red, the green, and the blue color lter areas. Adjustments of this filter arrangement and assembly of Fig. 5 are intended to be carried out in the manner hereinbefore explained in connection with the showing of Fig. 4 and need not be repeated in further detall.

In the arrangement of Fig. 6, the diversified color filter 35 is assumed to be formed from the red, the green, and the blue color filter areas 63', 65 and 61 which are similar to those of Fig. 5. These areas 63', 65' and 61' of Fig. 6 will also be in the nature of color wedges, but are formed in a slightly modified fashion which is indicated in such a way that the greatest absorption of light occurs at the remote corners of the red and the ' green filter areas 53 and 65 respectively, while the maximum absorption of the blue fllter section 61' corresponds substantially to that represented for the filter area 51 of Fig. 5. Again, the adjustment of the filter in the horizontal plane and in the vertical plane may be made as already explained in connection with Fig. 4, and, accordingly. is here represented again merely by the vertical and horizontal areas extending in both the up and down and the right and left directions.

The diversified color filter element shown by Fig. 7 is, in many respects, somewhat similar to that filter assembly shown by Fig. 4, for instance, except that the filter of Fig. 7 comprises four distinct areas 55', 51', 59' and 59. In this arrangement, the tllter areas 55' and 51' correspond respectively to the areas 55 and 51 comprising the red and green sections of the filter of Fig. 4. The area. identified as 59 serves as the blue lter area and corresponds to the arrangement of Fig, 4. except for the size of the blue filter area. The remaining filter area 59, also marked by the letter K on the representation of Fig. 7, is what may be considered, for example, as either being a completely clear filter area, an infra-red light absorbing area, or an orthochromatizing yellow filter or the like. Such lter areas, generally speaking, serve substantially to produce what is known in the art as a key image, in combination with tricolor systems, where the key image is also transmitted so that it later may be reproduced in a natural tint, such, for example, as black, grey, and white, and byadjustment of the filter assembly 35 of Fig. 7 in the direction shown by the arrow. it will be appreciated that various lter combinations may readily be obtained and the desired balance effects achieved. As used herein, it will be appreciated that the key image serves more or less as a black-and-whlte delineator and improves the transmission as a whole. More particular reference was made to the key image and its use in connection with additive color systems in applicant's presently pending application, Serial No. 455,556, filed August 21, 1942, and hereinabove previously mentioned.

Alternatively to the arrangements of Figs. 4 through 7, the color filter areas may be formed as sectors of circular filter elements, conventionally represented at 15 particularly in the showings of Figs. 8 and 9. In these showings the various flltersfor providing the red, the green, andthe blue transmissions are shown as sector shaped areas l120 in extent, but, for purposes of practical operation, they may be of any such angular width as is particularly suited to the color intensity absorption or saturation and other factors of the individual colors of the sectors.

As was mentioned in connection with the 'filter `arrangements of Figs. 4 through 7, and particularly Figs. 5 and 6, the color saturation of the various filter areas, such as 19 and 8| for the red, ,the green, and the blue, for instance, may

be identical over their entire area or of wedgeshaped character as indicated by Figs. 8 and 9..

The lter arrangement of Fig. 8, for example, is somewhat closely related to that of Fig. 5, in that the more dense areas are at the boundaries. The filter arrangement of Fig. l9 is, however, somewhat different from all the preceding types in that Fig. 9 discloses the most dense area at the central portion of the filter.

Motion of the filters in three directions, to provide the desired combination of filter effects in the optical path to the camera tube, may be provided, as indicated in Fig. 8, along paths desigl nated by the arrows 83, 85 and 81, while with the modification of Fig. 9, where the most dense section of the filter is toward the center, suitable adjustment of the filter is preferably obtained by moving up and down in the vertical direction, asl shown by the arrows 89, and by providing rotary motion about an axis 9| in either the clockwise and counterclockwise directions, as is indicated by the arrows 93. In this Way, provision is made for adding or subtracting from the image forming light passing through the filter assembly various amounts of the red, the green, and the blue light. With the arrangement of Fig. 9, it is apparent that the complete assembly of the filter may be movd olf-center by motion along the direction provided by the arrows 89, after which the rotation of the lcomplete assembly, as shown by the arrows 93, will emphasize absorption of one or more of the selected cornponent or primary colors.

It was explained above, in reference to Fig. 1 particularly, that the diversified color filter control cable V3'| might serve as an adjustment means whereby the diversified color filter position relative to the camera tube and the optical system is changed. This is particularly desirable in connection with arrangements whereby color balancing at the camera is Icarried forward fromv a remote control point, such as the monitor booth, whereat the observer or control operator views the images of the subject being transmitted.

With arrangements of this character, it is to be appreciated that, generally speaking, any form of mechanical or electrical controlmethod may be used for the purpose of providing the necessary or desirable adjustments of the diversified color illter 35, provided that the control force which may be applied'through the control shall be sufllciently powerful toA carry out the control those represented conventionally at 2l. II and 30 in Fig. 1, shall be precisely conveyed to the controlling devices for actuating or moving or adjusting the diversied color filter.

One example of a mechanical method of barrying out the control from the remote source to the diversified color filter, which is a representation of the control cable 31 conventionally shown in Fig. 1, has been shown in more detail as a multi-section cable in the arrangements of Figs. 10 and 11. It is to be appreciated that the dimensions shown are not in any sense to be regarded as accurate, but rather are exaggerated in the vertical direction, looking at the arrangement of Fig. 10 particularly, for the sake of clarity.

Represented by Fig. 10 is a torque-transfer cable of the triple type. This lcable is provided with three separate sections capable of transferring motion to three separate controls.v In the arrangement shown, the centralmost section |0| is arranged in such a manner as to be capable of rotation under the control of a control knob |03, forA instance, which might be regarded as being operated through any desired form of control, not show n, in accordance with the rotation of the control knob 26 (seeFlg. 1). the next outer hollow cylindrical section |05 may be assumed to be caused to rotate under the control of the control knob I 01, which is provided with a hollow centralmost opening\|09 to permit the centralmost section to pass through it. The hollow cylindrical section |05 is separated from the innermost section by a stationary low friction cylindrical member which serves as both a. bearing surface and a support for the cable elements or sections |0| and |05. The outer s'ection 3 of the torque-transfer cable element is arranged also in the form of a cylinder which is supported from the bearing surface ||5, also of low friction material, which surrounds the cylindrical torque-transfer section |05 and forms an inner bearing surface for the torque-transfer cable section ||3, and an outer bearing surface for the cylindrical torque-transfer section |05.

The hollow cylindrical torque-transfer section ||3 is arranged to be rotated relative to the stationary bearing surface ||5 by means ofthe control knob-II'I which is provided with a hollow central portion ||9 through which is arranged to pass the cable sections |0| and |05. The outer covering of the cable is provided by the outer shell |2| which forms both a low friction bearing surface for the outer surface of the hollow cylindrical torque-transfer section I3, 'and also serves as an outer shell for the cable. Y

It will be understood, from what has been stated above, that the hollow cylindrical cable section |05, for instance, may be rotated under the control of the control knob 28 of Fig. 1, and that the hollow 'cylindrical torqueftransfer section ||3 may be rotated under the control of the control promptly, and that the action transferred shall be sufliciently accurate or free from back lash that motion of control knobs or the like, such as The showings of Figs. 10 and 11 are consideredV to be purely schematic and to function in co' operation with the remaining figures of the drawings, and are particularly to exemplify the control between the monitor system 24 of Fig. l-

and the diversified colorfllter element 35 thereof. 'I'he particular controls to which the l torquetransfer cable section 31 may transfer motion are Similarly, Y

represented more particularly by the showings in all of Figs. 13, 14 and 15 of the drawings and, accordingly, for purpose of reference and illustration, it may be assumed that the different torque-transfer sections lili, and ||3 of the torque-transfer cable 3l are arranged to control the positioning of the diversified color filter element 35 through the motion thereof in the directions indicated by Figs. 13, 14 and 15, for example, relative to a suitable support frame, so that the individual filter control elements carried in the support frame about the diversified color filter section shall be capable of motion in the directions indicated, under the infiuence of some controlling medium such as the control knobs 26, 28 and 3U.

As an alternative. of course, it is apparent that any desired tele-control electric control means may be used, Various forms of such systems are known, particularly in the tele-control and the teiemetering art, and detailed description thereof is not considered to be necessary. Obviously, the control means 26, 26 and 30 may be arranged to operate or actuate suitable Selsyn or Autosyn motors for the purpose of providing the bi-directional motion or rotary motion of the light filter sections, as herein to be described.-

It is well known in the art that the amplitude, frequency or phase of the control currents, or combinations of these, may be used for control purposes in various well known manners. One particularly convenient method for carrying the control currents over considerable distances, for example, from the monitor booth of a broadcasting studio to the camera which is located in the studio, or even at a remote outdoor pickup point, has been shown by Fig. 12. In this arrangement the conductors |25 and |21 are assumed to be the usual telephone line circuits which carry the sound portion of the program from the pickup point to the transmitter. By well known methods which have herein been illustrated conventionally, these lines may be phantomed by well known and conventional circuits and, accordingly, control currents generated and selected in a control element |3| and transferred to the lines |25 and |21 by way of the transformer |29, whose secondary winding is center-tapped and connected to ground |32, as indicated, may be transmitted to be received in the control element |33 which identifies the control currents and then conveys them to well known balancing filter control means through the aid of a suitable transformer |35, one winding of which is center-tapped to ground |32, as indicated. It is, of course, to be appreciated that in such an'arrangement it is necessary that the control currents be alternating currents, but these are readily obtainable in well known manner. The illustration is merely made by way of example to show the flexibility of the particular forms of control arrangements of which the system is capable of utilizing. l y

Various ways of providing mechanical adjustments are of course to be understood'as coming fully withinthe scope of this .disclosure and,-as above stated, the arrangements of Figs. '13, 14 and are intended to represent schematically certain forms of mechanical systems for adjusting the diversiied color filter element 35 relative to both the optical system |3 and the camera tube I1 (see Fig. 1).

In kthe arrangement illustrated by Fig. 13, the diversified color filter element 35, which has been assumed to be a filter 'of the type schematically represented by Fig. 1, for instance, 'is carried in a support element |39 which is arranged to slide (looking at Fig. 13) to the right or left in guideways provided in a second support element |4I. The right or left motion of the support |39 which carries the diversified color filter element 35 is provided in one conventional form by means of the pinion |43 driving the rack element |45 which is attached to one end of the support |39. Obviously the torque-transfer cable of the type illustrated by Figs. 10 and 11 may be so arranged as to provide so that one section of the torquetransfer cable is arranged to rotate in either a clockwise or a counter-clockwise direction on the pinion |43, so that the rack is driven either to the left or to the right from the position shown. As the rack section |45 of the support |39 is moved by virtue of the rotation of the pinion |43, it will be appreciated that the stationarily positioned diversified color filter |35 moves to the left or right and, accordingly, is positioned to move within the region defined by the aperture or window |41 within the lower support element |4| so that no light which would pass through the filter 35 is masked by the lower support element, irrespective of the relative positioning of the lower support element and the upper support element |39 carrying the dversied color lter.

As is particularly indicated by the showing of Fig. 14, the lower support element |4| is arranged to be carried in guideways |49 in the frame support element |5I, so that by a rotation of the pinionelement |53, which is positioned to engage a rack element |55 carried on a. projection |51 of the support frame |4|, the support frame will be moved up and down in the direction shown by the arrows adjacent the rack section |55, and as the support frame |4| is moved in the up and down position (looking at Fig. 13) 'relative to the support |5|, it is apparent that the frame |39 carried by it, and therefore, also the diversi--l ned color filter 35, will be moved also in a like manner. For instance, the pinion |53 may be considered as being driven and rotated in either the clockwise or counter-clockwise direction under the control of another or second section of the torque-transfer' cable 31 of Fig. 1 and more particularly explained by Figs. 10 and 11; Accordingly, with the optical system so arranged relative to the supported diversified color ilter section, it is apparent that a rotation of the pinion |43 will cause the support frame |39 to be moved so that more of the red and green sections of the diversified color filter 35 and less of the blue section are beneath the optical system I3 but in the direct light path through the color filter disc I9, or more of the 'blue section 59 of the filter will be placed in the optical path and less of the red and green sections 55 and 51.

If now, the adjustment is established so that the desired amount of red and green, relative -to the blue, is established, the adjustment of the frame |39 may be considered as established for the instantaneous conditions then present. However, as was above explained in connection with the description of Figs. 4 through 9, it is not al-E ways possible that the correct filtering of the red and the green components may be obtained under such conditions, so that the red and the green sections 55 and 51 of the diversified color filter 35 may be varied and more or less of them placed in the optical path by a rotation of the pinion |53 to move the support frame |4| either up or down,- as indicated by the arrows, in which eventfthc area of the blue alter coming within the optical 17 path will remain constant while the red and the green will be varied, with more of the red filter section coming within the optical path for a downward motion of thesupport .frame and more of the green filter coming within the optical path with an upward motion of the support frame.

In a modified form of the arrangement as shown in Fig. 15, a frame support |8| which is particularly adaptable for use with thefllter section shown by Fig. 8, is schematically shown. In this connection, independent drive pinions for obtaining motion of thefllter in the directions represented by the arrows 83, 85 and 81 are provided respectively by means of driving pinions |6I, |63 and |65 which are arranged to mesh respectively with racks |61, |69 and |1| carried on the extremities of support elements |13, |15 and |11 respectively, of which the support section |11 is assumed to carry and support the filter assembly 15.

In the showing of Fig. 15 it is, of course, to be appreciated that the representation is purely schematic and that the guideways for the various frame supports have not been illustrated in detail, although it is to be understood that these follow in accordance with the general outline made in the showing of Figs. 13 and 14. The lower support frame which carries the complete assembly is represented schematically at |8|, and it is so set up that it carries, in turn, in layer formation, the lowermost movable support frame |15 upon which is supported the movable frame |13, and the frame |13, in turn, supports for motion in the direction shown by the arrows 83 the uppermost support frame |11. In this way it is apparent that adjustments or rotation of the pinions |6I, |63 and |65 may readily be carried forward by a rotation of the control knobs |03, |01 and ||1 to rotate ineither a clockwise or a counter-clockwise direction the sections |I, |05 and I3 of the torque-transfer cable 31.

It was explained, in connection with Fig. 8, that the motion of the filter relative to the optical path will regulate accordingly the amount of selective color filtering provided for theventering light. Accordingly, it is to be appreciated that the lowermost support frame |8| is provided with a window or apertured portion defined by the dotted outline |83 on Fig. 15, so that, irrespective of the position of any of the ,filter support or masking areas, the optical path will be defined and limited only by the actual position of the filter assembly 15 relative to this window area. Similarly, the lowermost adjustable support element is provided with a window or apertured area defined by the dotted outline window portion |85, while the centermost or middle adjustable member is provided with a window or apertured portion |81. In this way the extremity of motion of the filter 15, along the path indicated by the arrows 83, will be determined by the limit defined by the window |81, while a similar condition will obtain obviously for the remaining portions of the system.

It is accordingly apparent, from what has been hereinabove explained, that the adjustment of the various diversified color filter elements, such as those conventionally represented at 35 and 15, for instance, will provide a controllable variable color range toward or away from each of the group of primary colors, and provide a color balfance which establishes a color control to improve the operation of the system and to achieve the color balancing effects of presently known electrical systems without introducing into the system the need of sequential variation of the electrical system control, nor yet the need of separate signalling channels for the separate color renditions transmitted. At the same time, the adjustment of the diversied color filter, relative to the camera or scanning tube I1, is established Awithout the necessity of continually shifting from one position to another, since the adjustment, once established, has been found to be such that it will hold for a considerable time with variations required only upon substantial changes in the studio or circuit conditions taking place, all as hereinabove outlined.

Reference was hereinabove made to the use of a system of this character for color photography purposes in addition to the previously ldescribed television uses. In the general statement of the invention, reference was made to the fact that the disclosed system also found use either for cyclic or sequential photography on the one hand, or simultaneous color photography in a plurality of colors on the other hand.

Generally speaking, the cyclic color photography processes are carried forward .in broadly the same way as for cyclic or sequential television, with the exception that monitoring must be carried forward by a modified form of arrangement since the recorded image is latent and unavailable until after development, which requires an appreciable time. Similarly, for the simultaneous color photography, the process is generally similar to that of simultaneous color television, with the exception that the recording, in its final form, in each photographic instance, takes place directly upon the lm as a latent image later to be developed, and consequently unavailable for examination at the time of exposure.

Thus, in all color photographic processes, it is desirable and practically essential that vvisual monitoring be carried forward. To this end, a duplicate of the recorded image is usually observed by an operator through a suitable nder lens, known as a View finder, which is suitably matched with a camera lens and mechanically coupled therewith for matched and related adjustment. Usually it is unnecessary to make correction in such systems for parallax distortion as far as the color correction is concerned, although for color photography per se, paraiiax correction is naturally desirable to insure accurate registry of the recorded images on the film frame areas. Where this is accomplished, the parallax control and compensating arrangement may be provided, in the general form shown, for example, by Burns Patent No. 1,931,890, granted October 24, 1933. Under such circumstances. a diversied color filter is positioned in both the optical path along which the light'of the image is directed through the camera lens to the film, and also along the optical path through the view finder lens to the view finder image plane. The separate diversied color filters in such systems should be mechanically coupled and in the same relative location with respect to each optical system. For purposes of reference herein, the diversified color fllter, located in the main or primary voptical system, may be considered as being equivalent to the filter shown by any of Figs. 4 through 9 and located relative to the optical system i3 in the general arrangement shown by Fig. 1.

Accordingly, if referenceis made to Fig. 13 of thisdisclosure, it will be seen thatA the lter 35 is carried in the framework |39 so as to be in the light path to the television camera tube. It may be assumed fon-illustration purposes, that the finder optical path and it will be appreciated that any adjustments of the filter element 35, by reason of motion of either of the frameworks E39 or Mi, will produce an identical adjustment of the secondary filter relative to the view finder optical .system and its screen. Under such conditions, of

course, it will be appreciated that the operator viewing the image in the view finder will control the position of the knobs or dials 2B, 28 and 30, for instance, in the same manner as with the monitoring operator for the television system who observed the monitor image in a monitor 24. The desired color balance is thus visually monitored.

To accomplish a monitoring of a. color photographic system by another and alternative method, and to calibrate the filtersl for such conditions, it is desirable to use a color temperature meter, such as one of the type manufactured by Eastman Kodak Company, which is frequently used in con.. nection with particular types of color-sensitive films for color photography. A color temperature meter of this general character has been described, for instance, in the Journal of the Society of Motion Picture Engineers, for March, 1939, in an article entitled A color temperature meter, by E. M. Lowry and K. S. Weaver, on pages 298 to 306 inclusive, vol. 32. The neutral setting of the diversified color filter, to establish the desired color balance, will then be made to correspond to some predetermined specific color temperature for the particular film in use; and for any other color temperatures, the added color temperature scales or calibrations adjacent the control knobs 26, 28 and 3U, for instance, will indicate the proper setting or adjustment of the diversiiied color filter relative to the optical system for use of the system with an illuminant of that color temperature. Suchy conditions` of course, are to be assumed and to apply rather rigidly where the illuminant which is illuminating the subject or body Il produces black body radiation at some chosen color temperature. which type of .radiation would reasonably closely be obtained where the illumination was either by sunlight, skylight, or incandescent lamps. IBlack body radiation is, of course, well known and quite particularly explained in the text "A Treatise n Light by R. A, Houstoun, published in 1925 by Longmans-Green & Co., London, and particularly the portion of the text on pages 444 through 446 where well known curves of black body radiation are illustrated, which show that radiation from a black body is proportional to the fourth power of the absolute temperature. However, if the subject Il is illuminated by a source of the selective radiation type, such as, for example, by fluorescent lamps, mercury vapor lamps, or gas filled flash tubes utilizing neon, krypton, argon, xenon, and the like, then it is necessary that the calibra- -tion of the scales adjacent the control knobs 26,

28, and 30 be made for the chosen illuminant because the equivalent color temperature will not be strictly accurate. Conditions of selective radlation are more particularly explained in the Houstoun text hereinabove named, in the portion appearing particularly on pages 359 and 360,l

In accordance with the foregoing, it isapparent that various modifications may readily be made in the system so that it is usable interchangeably for either or both color television or color photography. I

It is, of course, to be appreciated that, in regard to the description of the color television portion of this disclosure, reference has been made primarily to the so-called additive process. It should be understood, nevertheless, that the general television technique hereinabove explained is equally adapted for; use in systems of the so-called subtractive type. The general arrangements of the diversified color filter shown herein by Fig. 7, however, would not be directly applicable to subtractive types of color television systems, insofar as the use of the section 69 of the diversified color filter 35, to produce what is herein termed the key image, is concerned. Instead, for subtractive television systems, the section 63 of the diversified color filter 35 may be of the type generally known as the black printer and described and known in the literature.

Regarding this type of system, reference has herein been made primarily to tricolor arrangements. However, it should be understood and appreciated that the general arrangement is equally as applicable to bicolor systems.

yIn the event that use is made of the bicolor system there would, generally speaking, be only two color filter areas. These would usually be an orange-red and a green-blue. Under such circumstances, it would at once be appreciated that if reference were made to the type of filter shown by Fig. 4, for instance, the combination of the red filter 55 and the green filter 5T would be embodied in but a single orange-red filter element of a size equal, generally speaking, to the combined size of the two filters, as illustrated, providing the blue filter of Fig. 4 is replaced by a green-blue filter of the same area as the filter 59, or, in any event, the filter sizes should be not widely different for ease of adjustment. Under these circumstances, of course, only one adjustment would be necessary, that being the adjustment along the back and forth paths indicated immediately below the filter diagram of Fig. 4 in either a left-to-right direction or a right-to-left direction. Further, with filters of the type shown by Fig. 5 being used, so that the filters become more dense as they depart from the abutting edges, it is likewise equally as apparent that only the lateral adjustment need be made. Such bicolor diversified color filters may have color areas meeting either along a line or at a point or along two lines. Other arrangementsare possible falling within the scope of this invention, both for bicolor and multicolor diversified color filters.

To provide'this type ofadjustment, of course only one of ythe various remote control cable arrangements,` or other similar types of devices, need be used, so that if the filters of the bicolor type are mounted in a frame support, such as that shown at |39 in Fig. 13, then the pinion |43 driving the rack |45 would be adequate to provide the filter adjustment.

In instances where a key image is used in combination with a bicolor system, thenv it will be appreciated that the key image section of the filter may occupy a. section of the complete filter 35, which might be represented by the filter area 6l in Fig. 7, with two-thirds of the remaining area of the complete filter then being occupied by the reddish-orange filter and one-third of the remaining area. being'occupied by the greenishblue filter.`or vice versa, as the case may be.

These references have been made merely for illustrative purpes and in order to show the general application of the system for two-color processes. In any event, it is apparent that, regardless of whether the system is a bicolor or a. tricolor -systemand with or without key images, or a subtractive system where a black printer is used, the filter adjustment relative to the optical axis will be such that it has a transverse or rotary component of motion with respect to the said optical axis and/ or the central portion of the light path toward the light receiving area.

From what has been stated above,v it is believed to be self-evident that the lter element, which applicant has herein termed a, diversified color filter, is of a character such as to be composed essentially of at least two areas of different colors which are introducible into the image forming light beam. Accordingly, the arrangement is of a character different indeed both as to its function and its operation from a single filter having areas of different shades of one and the same color.

Als was explained in the specification above, for atWo-color diversified color filter the color areas may meet along straight lines, curves or, at least, in a sense, at a point where the color areas are sectors of a circle or the like, as is exemplified, for instance, by the arrangements of Figs. 8 and 9. For three-color or multicolor filters, the areas may also meet at a point for circular sectors,

along lines for rectangular areas, or along curves for segmental arrangements. Thus, a jointure and intersection or common point or line, as herein specified, will be regarded as the intersection point or contiguous boundary of the respective color areas of the diversified color filter. In this way it can be appreciated that for a rectangular color area there is usually a common point; for sectorial color areas there is also, in general, a common point; but for segmental areas the common point may not exist and there may be a number of common lines between adjacent areas.

Further than this, it will be understood from what has been stated above, that a neutral or inactive point on the diversified color filter is that point which, when placed on the axis of the optical system or on the central axis of the image forming beam, as may be the case, causes the diversified color filter to produce no change in,

or from, the desired olorbalance, but causes solely a 4brightness reduction in the resulting image or video signal output. herein referred to as the common point and the neutral point in a diversified color filter may not be, and frequently are not, coincident or identical in use.

From what has been stated above, television apparatus incorporating diversified color filters of any of the aforesaid types may readily be operated in such a way that the neutral setting of the filter corresponds to a state of very little cr practically. no absorption of light. This would be the case, for instance, with the arrangement of Fig. 8, wherein the filter comprises sectorial-shaped areas 11 for red; lli` for green; and 8l for blue, where, at the centralmost point, or the meeting point, the filters would have minimum light absorption and be practically clear (assuming the wedge character of the filter), but, toward the edge of the lter, the light and color absorption would increase. Thus, there is provided an arrangement where the increases in density would, with this system, extend from the center outwardly so that the light absorption for any given amount of color balancing may be kept strictly at a minimum by providing adjustments from the center outwardly.

Thus, the terms Thus, with the use of the filter arrangements of the types herein disclosed, it is possible to provide color balance corrections according to purely nonelectrical methods which will eliminate completely the likelihood of electrical noise or the like being introduced into the circuits.

It has happened in operation of bicolor, tricolor, or multicolor television systems that where the camera tube is being operated at a level close to its sensitivity limit, as determined by the nosie in its output, it is usually not possible to secure a color balancing according to electrical methods by increasing the amplification for any one or more of the video color signals, but, on the contrary, it is necessary to decrease the amplification for one or two or more of such video color signals in order to secure the desired color balance: Accordingly, the result is a signal attenuation in any instance. However, irrespective of the conditions above suggested, it is apparent that adjustments of the diversified color filter, as herein explained, readily provide the desired form of compensation without appreciable noise introduction, or the likelihood thereof.

In the event it is desired, for instance, to provide a diversified color filter which shall be capable of compensation and, at the same time, capable of providing the proper and desired color balance or color gain control, a filter of the wedge character (such as that shown by Fig. 8, for example, where the centermost part of the filter has minimum density and the outermost parts of the filter near the edges of the circle have greatest density) may be positioned in the optical path in such a way that the centermost part of the filter (such as the point 9|, referring to Fig. 9, for instance, which would be like the center part of the filter of Fig. 8) is slightly de-centered from the center of the lens aperture. In this way, desired balancing may be effected by mere rotation of the filter arrangement. Of course, it is apparent that u nder such circumstances the desired range will be limited, but, in the event it is desired to increase the range over which the filter is effective so as to bring greater density areas nearer to the center of the lens aperture, for instance, the lter may be moved up and down along'a path, as indicated by the areas 89 in Fig. 9, to vary the range of control (e. g., to establish a decrease or increase) and then rotary motion of the filter will again provide the desired balance.

One essential feature is that by using filters of the wedge type as hereinabove explained it is possible to obtain greater compensation and greater corrections for a small or limited amount of motion or, for any predetermined amount of motion, greater or less absorptions can be obtained within the limits of motion. In all cases where a diversified filter is used, it is desirable to provide a multiplicity of color areas. Then, to provide the compensation and color balance control, the diversified filter must be moved in at least one or two fashions of which one may be considered as a translatory motion having a component orthogonal to the optical axis or the center of the image forming light beam, or the other may be considered as being the case where the lter is so arranged as to be capable of rotary motion where there is a component of such rotary motion about an axis parallel to the central axis of the image forming beam, with the motion in either case being such that it produces a change in the relative proportions of the color areas comprising the filter with reference to the cross section of the image forming light beam intersected by the filter.

Other various modifications may be eected by suitable positioning of the diversified color lter in an eccentric position relative to the optical system, as will be apparent from what has been hereinabove stated.

Any consideration of the system as it embodies the light responsive camera tube, in combination with the means by whichhe light beams (representative of the selected component colors) are directed thereupon, when used with a diversified color filter of the character hereinabove explained, will be understood as incorporating features such that the diversified color filter may itself be adjusted to create a balance in the system which will compensate not only for optical changes but also for electrical changes. It happens frequently that changes in the video amplifiers and/or modulators, due, for example, to tube changes, voltage variations and the like, may frequently be compensated in the manner hereinabove explained through the adjustment of the diversified color filter, so that a color balance is obtainable without the introduction of electrical noise or disturbance.

From the description herein set forth, various modifications naturally follow and readily may be made in the system without departing from either its spirit or scope. Therefore, the invention is to be regarded in the light of the claims hereinafter appended in which the following is claimed as the invention.

Having described the claimed is:

1. In a system which includes an image forming optical system, a light responsive image receiving area, and component-color filter mean's adapted to present light of different component colors to the light responsive image receiving area, the combination comprising a relatively fixed position color balancing filter element supported in intersecting relationship to and in a non-imaging position in the image forming light beam path of the optical system so as to include at least the complete beam cross-section, and means to adjust the said color balancing filter with a component of motion relative to the axis of the optical system and within the image forming light beam path so as to vary the proportions of the filter color areas in the optical path so as thereby to provide a controllably variable color range thereof toward and away from each .of the select-eci component colors as presented to the image receiving areas. v

2. In combination with an image forming optical system, a light responsive image receiving area whereon impinging light causes a latent image to be developed, and color filter means adapted'to move continuously and uniformly so invention, what is tnA colors so as to compensate for different color responses of the image receiving area. l

3. In combination with an image forming optical system and a light responsive light image receiving area to receive light directed through the Aoptical system, a, plurality of component-color receiving area, in each component color in seas sequentially to present rapidly changing light of different component colors to the light responsive image receiving area, a iixedly positioned color balancing filter element supported in intersecting relationship to and in a. nonimaging position in the image forming light beam path of the optical system so as to include at least the complete beam cross-section, and means to adjust the said color balancing filter .with a component of motion relative to the axis of the optical system and within the image forming light beam path so as to vary the proportions of the filter color areas thereof which are included in' the optical path so as thereby. to provide a controllably variable color range thereof toward and away from each of the selected component quence, a normally lixedly positioned color balancing filter element, said filter element having filter. areas of relatively low light absorption as compared with the absorption of the componentcolor separation filter elements, said color balancing filter element including a plurality of filter areas having colors of at least the majority of the component-color areas of the color separation filter but of lower saturation and absorption and being located to intersect and to include the complete optical beam path and in an out-offocus plane relative to the light responsive light image receiving area, and means to adjust the said color balancing filter with a transverse component of motion relative to the axis of the optical system so as thereby to vary the proportions of the several color filter areas of the color balancing filter simultaneously included in the optical path thereby providing a controllably variable color range in the light images reaching the image receiving area.

4. In combination with an image forming optical system and a light responsive light image receiving area to receive light directed through the optical system, a plurality of componentcolor light absorption separation filter elements located in intersecting relationship to and including the complete optical path, means for rapidly and uniformly moving the said filter elements at a high repetition rate relative to the optical path so that light is revealed to the light responsive image receiving area in a sequence of cyclically changing component colors, a normally iixedly supported color balancing filter element also located in the optical path and arranged for relatively slow adjustment, said filter element having filter areas of relatively low light absorption as compared with the absorption of the componentcolorseparation filter elements, said color balancing filter element including a plurality of filter areashaving colors of at least the majority of the component-color areas of the color separation filter but of lower saturation and absorption and being located to intersect and to include the complete optical beam path and in an out-offocus plane relative to the light responsive light image receiving area, and filter control means to adjust the position of said color balancing filter within the optical path with a transverse component of motion'relative to the axis of the optic al system so as thereby to vary the proportions of the several color filter areas of the color balancing filter simultaneously included in the optical path thereby providing a controllably variable color range in the light images reaching the image receiving area. I

5; In combination with an image forming optical system and a light responsive light image receiving area to receive light directed through the optical system. a plurality of componentmoving the said filter elements relative to the optical path comparatively rapidly so that light is revealed to the light responsive image receiving area in each component color only at a given time, and for the several component colors in a predetermined sequence, a color balancing fllter element also positioned in the 'optical path and relatively slowly movable relative. thereto, said color balancing filter element having filter areas of relatively low light absorption as compared with the absorption of the component-color separation filter elements, said color balancing filter element including a plurality of lter areas having colors of at least the majority of the component-color areas of the color separation filter but of lower saturation and absorption and being located to intersect and to include at least the complete optical beam path and in an out-,offocus plane relative to the light responsive light image receiving area, and means to adjust the said color balancing filter with a transverse component of motion relative to the axis of the optical system so as thereby to vary the proportions of the several color filter areas of the color balancing lter simultaneously included in the optical path thereby providing a controllably variable color range of light images directed upon the image receiving area.

6. In combination with a color television system wherein is included an electronic camera tube having a mosaic light responsive target area for receiving light images, and an image forming optical system for directing image forming light beams toward the camera tube, a componentcolor light filter element assembly having relatively high light ab-sorption in the selected component colors of an additive color system, means for comparatively rapidly and transversely moving the said filter relative to the image forming light beam path for sequentially illuminating the mosaic target of the tube in light of predetermined component colors, a relatively slowly movable color balancing filter element having filter areas of relatively low light absorption as compared with the iilter areas of the componentcolor separation filter elementwith the color balancing filter elements being adapted to absorb substantially the same color light components as the component-color filter element, said color balancing filter element being positioned in intersecting relationship to and in anout-offocus position in the image forming light beam path so as to include atleast the complete beam cross-section, and means to adjust the said color balancing filter element along at least two adjustment paths so that a controllably variable color range thereof is included within the image forming light beam path, and so that compensaltion for varying color responses of the camera tube in different color light is obtained.

7. In combination with a color television system wherein is included `an electronic camera tube having a mosaic light responsive target element for receiving light images, and an image forming optical system for directing image forming light beams toward the camera tube, a component-color light filter element assemblyhaving relatively high light absorption in the selected component colors 'of an additive color system, means for relatively rapidly and transversely moving the filter while including the optical path for illuminating the mosaic target of the camera tube in light of predetermined component colors in a cyclic manner, a relatively slowly movable color balancing filter element having filter areas 26 of relatively low light absorption as compared with the filter areas of the component-color separation filter elements with the color balancing lter elements being adapted to absorb substantially the same color light components as the component-color filter element, said color balancing filter element being positioned in intersecting relationship to and in an out-of-focus position in the image forming light beam path so as to include at least the complete beam crosssection, and means to adjust the said color balancing filter element orthogonally relative to the light beam path and along at least two adjustment paths so that a controllably variable color ran-ge thereof is included within the image forming light beam path to provide thereby compensation for varying color responses of the camera.

' tube to light of the different component colors.

A8. In a system of color television which embodies an electronic camera tube having a light responsive target element for receiving light images, an image forming optical system for directing the image forming light rays toward the said target element, and a component-color separation filter having color transmission sections corresponding to predetermined component -colors of an additive color process, and means for moving the separation iilter relatively rapidly relative tothe image forming light beam path for cyclically directing light in individual selected component colors to the tube target element, said color separation filter sections each having relatively high lght absorption, the combination comprising a relatively slowly movable color balancing filter element including a plurality of component-color filter areas of approximately the component colors of the separation filter and arranged in juxtaposition with respect to one another and havin-g light absorptions which are relatively low as compared with the sections of the color separation filter, and said color balancing filter being positioned substantially transverse to the axis of the optical system and embracing an area at least as great as the complete light beam cross-section and also being located in an out-of-focus position with respect to images formed upon the camera tube target element, and means to adjust the color balancing filter relative to the axis of the optical system and including the image forming light beam path so as to vary the portions of the color filter areas of each different component color included in the cross-section of the light beam passed to the target element so as thereby to compensate and controllably vary the color range of the color image directed upon the target element.

v9. The system claimed in claim 8 wherein the color balancing lter adjustment means comprises means for shifting the filter in one direction along a substantially straight line path and additional means for providing movement of the filter in a second path independently of the first motion.

10. In a television system which embodies an electronic camera tube having a light responsive target element for receiving light images, an image forming optical system for directing image forming light rays toward the said target element, a component-color separation filterv assembly having color transmission sections corresponding to predetermined component colors of an additive color system, and means for rapidly,

beam path for cyclically transmitting light in each of the selected component; colors to the said target element, said color separation filter sections each having relatively high light absorption, the combination comprising a color balancing filter element including a plurality of component-color filter areas of approximately the component colors of the separation filter and arranged in juxtaposition with respect to one another and having light absorptions which are relatively low as compared with that of the filter sections of the color separation filter, and said color balancing filter being positioned in the image forming light beam path of the optical system in intersecting relationship thereto and in an out-of-focus position with respect to images formed upon the camera tube mosaic element, and means to adjust the color balancing filter relative to the axis of the optical system and while encompassing the image forming light beam path so as to vary the portions of the color filter areas of the different component colors included in the optical path to the mosaic electrode so as thereby to compensate and controllably vary the color range of the color image directed upon the mosaic.

11. A multicolor television system having a light responsive image receiving target, an optical means to project light images upon the target so as thereby to cause the development of electrostatic charges thereon in accordance with the intensity of the impinging optical images, and means to scan the light responsive image receiving target to transfer to a communication channel signal wave train outputs of magnitudes proportional to the intensity of the impinging light, the combination which includes a componentcolor separation element having a plurality of filter sections of relatively high light absorption and with at least one filter section of each component color of anadditlve color system, said filter being located in the optical path so that each filter area embraces the said path, means for moving the filter relatively rapidly relative to the light beam path at a uniform rate for cyclically and sequentially passing light of each selected component 4color of the multicolor system to the light sensitive target element; a relatively slowly movable color balancing filter element comprising also a plurality of filter sections also of the said chosen component colors and of relatively low light absorption compared with the sectional areas of the color separation filter and positioned and within the image forming 1ight beam path so that all filter sections thereof may be included within said path simultaneously, said color balancing filter being positioned in a nonimage forming location relative to the image cast upon the light responsive target, and means to shift the position of the color balancing filter transversely to the optical axis so that the proportions of the different color balancing filter areas simultaneously included within the optical path may be varied to compensate therebyl for different color responses of the light responsive target.

12. In a multicolor image resolving system having a light responsive image receiving target element and an optical means to project light images upon the target so as thereby to cause the development thereon of a latent image representative of the varying intensities of light and shadow of the impinging optical images, the combination which includes a component-color separation element positioned for sequentially and relatively rapidly revealing light in a repeating sequence in said selected component color of the multicolor system to the light sensitive target element, a second filter element comprising a plurality of filter sections also of the said chosen component colors and of relatively low light absorption compared with the color separation filter positioned to include at least the complete crosssection of the image forming light beam path so that all filter sections thereof may be included within said path simultaneously, said colorbalancing filter being positioned in a non-image forming location relative to the image cast upon the light responsive target, and means to vary the position of the color balancing filter transverse to the optical axis so that the proportions of the color balancing filter areas of the different component colors simultaneously included within the optical path may be varied to compensate thereby for different color responses of the light responsive target to individual component colors.

13. A multicolor television system having a light responsive image receiving target, an optical means to project light images upon the target so as thereby to cause the development of electrostatic charges thereon in accordance with the intensity of the impinging optical images, and means to scan the light responsive image receiving target to develop signal wave train outputs of magnitudes,` proportional to the intensities of the impinglng light, which signals are adapted to be supplied to a transmission channel, the combination which includes a component-color separation element for sequentially and relatively rapidly transmitting light in each selected component color of the multicolor system to the light sensitive target element, a second lter element comprising a plurality of filter sections also of the said chosen component colors and of relatively low light absorption compared with the color f separation filter positioned to include at least the complete cross-section of the image forming light beam path so that at least portions of all filter sections thereof may be included within said path simultaneously, said color balancing filter being positioned in a non-image forming location rela tive to the image cast upon the light responsive target, and means to vary the position of the color balancing filter transverse to the optical axis so that the proportions of the color balancing filter areas of the different component colors simultaneously included within the optical path may be varied to compensate thereby for different color responses of the light sensitive target and thereby provide substantially uniform signal outputs for all color light of substantially like intensity.

14. A multicolor television system having a light responsive image receiving target, an optical means to project light images upon the target so as thereby to cause the development of electrostatic charges thereon in accordance with the intensity of the impinging optical images, and means to scan the light responsive image receiving target to develop signal wave train outputs of magnitudes proportional to the intensities of the impinging light, which signals are adapted to be supplied to a transmission channel, the combination which includes a component-color separation element supported for sequentially, cyclically-and relatively rapidly revealing light in each selected component color of the multicolor system to the light sensitive target element at a high velocity so that repetition occurs at a. frequency at least as high as that of the persistence of vision, a second filter element comprising a.

. 29 plurality of filter sections also of the said chosen component colors and of relatively low light absorption compared with the color separation filter normally fixedly positioned to include at least the complete cross-section of the image forming light beam path so that at least portions of all filter sections thereof may be included Within said path simultaneously, said color-balancing filter being positioned in a non-image forming location relative. to the image cast upon the light responsive target, and means to vary the position of the color-balancing filter transverse to the optical axis at a rate slow compared to the sequence of the several component colors of the lirst named filter so that the proportions of the color-balancing iilter areas Aof the different component colors simultaneously included Within the optical path may be varied to compensate thereby for different color responses of the light sensitive target and thereby` provide substantially uniform signal outputs for all color light of substantially like intensity.

-15.A multicolor television system having a light responsive image receiving target, an optical meansto project light images upon the target so as thereby to cause the development of electrostatic charges thereon in accordance with the intensity of the impinging optical imagesy and means to scan the light responsive image receiving target to develop signal wave train outputsof magnitudes proportional to the impinging light, which signals are adapted to be supplied to a transmission'channel, the combination which includes a component-color separation element for sequentially and relatively rapidly passing light in each selected component color of the multicolor system to the lightl sensitive target element, a second filter element comprising aplurality of filter sections also of the said chosen component colors and of relatively low light absorption compared with the color separation filter positioned to include at least the complete cross-section of the image forming light beam path so that at least portions of all iilter sections thereof may be included within said path simultaneously, said color balancing filter being positioned in a nonimage forming location relative to the image formed upon the light responsive target, and means to vary the position of the color-balancing iilter transverse to the .optical axis so that the proportions of the color balancing filter areas of the diiierent component colors simultaneously included Within the optical path may be varied to compensate thereby for dilierent color rei sponses of the light sensitive target area.

16. A system for obtaining color balance in multicolor television systems of the'type Wherein optical images are directed by an optical system tovfocus upon an image receiving element, which comprises a component color separation lter element for forming, with progressive and sequential changes in the filter color component included in the optical path ofthe system, a sequence of compo-nent color light images which are developed and directed along the optical axis of the optical system and focused upon the image receiving element, a color balance ilter element located in an out-of-focus plane remote from the image receiving element upon which the component color light images are focused for intercepting predetermined quantities' and color qualities of the light images directed along the optical axis of the system to the image receiving element, and means for controllably varying the light interception by the second filter element in the selected multicolor components to selected degrees to compensate for variance in the color of the iiluminant and the degree of chromatic response and sensitivity of the light image receiving element upon which the image is focused and the therewith associated system.

17. In television apparatus having a light responsive image receiving camera tube, an optical system to direct and focus light images upon the camera tube, and a first cyclically movable filter means for presenting as a repeating sequence a series of color images produced in sequence by light rays representative of an image passing through individual selected component color filter elements of the group of filter elements forming the complete filter so that light rays of each selected component color of the image are caused to influence the light responsive camera tube, the combination of a second movable filter means for balancing the color response of the light responsive camera tube to each of the color components, and means for controllably moving the second filter relative to the first filter and to the camera tube for intercepting controllably variable quantities and color qualities of the said component color images which arey focused upon the light responsive camera tube.

18. In a system of sequential color` television in a plurality of selected component colors wherein light images in the said selected component colors of the image are caused te iniiuence a light responsive camera tube which is adapted to be scanned at a selected field repetition rate to produce signal outputs representative of the said component color images, a first component color separation filter unit positioned relative to the camera tube to expose the camera tube, with a cyclic and progressively sequential change in the color component of the iilter instantaneously included in the light path, to a sequence of light images of the selected component colors at a rate coinciding with the selected field scanning rate, a color balancing filter for separately modifying the light image rays directed upon the camera tube by the component color separation lter so as to compensate for changes in color` of the illuminant and chromatic response of the said camera tube and the output system associated therewith in each of the color components, and means to move the color balancing filter relative to the component color separation filter and to the camera tube for intercepting predetermined quantities and color qualities of the light of the said component color images as focused upon the camera tube and also for controllably varying the light interception in each of the color components to preselected varying degrees.

19. The method of obtaining color balance in multicolor television systems including a camera tube having a light responsive storage electrode element having 4different responses to different selected component colors which comprises forming a multicolor image in a selected number of component colors while directing the light rays from an object along a predetermined light beam path, focusing the component color images upon the light responsive storage electrode of the camera tube to produce thereby electrostatic charge representations of magnitudes proportional to thegbrilliance of the focused images', scanning the light responsive electrode to produce output image signals therefrom to be applied to a transmission channel, intercepting predetermined quantities and color qualities of thelight of the component colors along the light beam path in a plane remote from the focal plane of the light images, and 'controllably varying the color interception of each of the selected color components' to predetermined degrees to compensate for response variations of the camera tube to the different component colors.

20. The method of obtaining color balance in multicolor television systems including a camera tube having a light responsive storage electrode element having different responses to different selected component colors which comprises forming a sequence. of color images in a predetermined selected number of component colors at a predetermined rate while directing the light rays from an object along a predetermined light beam path, focusing the component color images upon the light responsive storage electrode of the camera tube to produce thereby electrostatic charge representations of magnitudes proportional to the brilliance of the focused images, scanning the light responsive electrode at a scanning rate corresponding to the rate of component color image formation to produce output image signals therefrom to be applied to a transmission channel, intercepting predetermined quantities and color qualities of the light of the component colors along the light beam path in a plane remote from the focal plane of the light images, and controllably varying, at a rate slow relative to the scanning rate,

the color interception of each of the selected color components to predetermined degrees to compensate for response variations of the camera tube to-the different component colors.

21. The method of obtaining color balance in multicolor light responsive systems including a light image receiving element having a light response characteristic of a different nature for each of a plurality of selected component colors which comprises forming a multicolor image in a selected number of component colors while directing the light rays from an object along a predetermined light beam path, focusing the component color images upon the light image receiving element to produce thereby image representations proportional to the brilliance of the focused images, intercepting predetermined quantities and color qualities of the light of the component colors along the light beam path in a plane remote from the focal plane of the light images, and controllably varying the color interception of each of the selected color components to predetermined degrees to compensate for response variations of the light image receiving element in the different component colors.

22. An optical system comprising a lens element for focusing an optical image directed thereupon at a remotely spaced image plane, a relatively rapidly movable color separation unit located in the optical path for producing a plurality of component color images of the optical image directed into the optical system in a predetermined sequence at the spaced image plane, and a color balancing filter element having a plurality of color filter areas of relatively low light absorption of colors substantially corresponding to the component colors into which the optical image is formed, said color balancing filter element being positioned in the light path of the optical image so that predetermined areas of all separate areas thereof are simultaneously included in the optical path to provide predetermined color balancing.

23. The optical system claimed in claim 22 comprising, in addition, means for adjusting the position of the color balancing filter element relative to the said optical path to vary thereby the relative areas of the selected component colors which are simultaneously .included in the optical path.

24. In combination with an image forming optical system and a light responsive image receiving element the field of which is arranged to be bi-dimensionally scanned at al substantially uniform field repetition rate, a component color separation filter element arranged sequentially to present, at a repetition rate which is synchronous with the field scanning repetition rate, light images in different component colors to the light responsive image receiving element, a relatively stably located color balancing filter element located in intersecting relationship to and in a non-imaging position in the image forming light beam path of the optical system so as to include at least the complete light beam cross-section as projected through component color separation iilter and the optical system, and means to adjust the said color balancing filter with a component of motion relative to the'axis ofthe optical system and within the image forming light beam path so as to vary the proportions of the lter color areas in the optica1 path so as thereby to provide a controllably variable color range thereof toward and away from each of the selected component colors.

25. A system for obtaining color balance in multicolor television systems which comprises light image receiving means having light re sponse characteristics 4which are different in nature for each of a plurality of selected component colors into which an optical image is analyzed for transmission, an optical device to direct and focus component color light images into the light image receiving means to produce image representations proportional to the brilliance of the focused light image, and a controilably movable color balancing filter element having low color selectivity characteristics as compared to the color selectivity of the overall system in each component color of the light directed through the optical device, which color selectivities due to the color balance filter element are determined in accordance with the positioning of the color balance filter relative to the optical device so as to compensate for response variations of the light image receiving means in the different component colors.

ALFRED N. GOLDSMITH.

REFERENCES CITED The following references are of record in the i'lle of this patent:

UNITED STATES PATENTS Number Name Date 2,010,307 Lieshman Aug. 6, 1935 562,642 McDonough June 23, 1896 2,285,262 Fess et al. June 2, 1942 740,484 Stocoum Oct. 6, 1903 1,154,607 Brasseur 1 Sept. 28, 1915 1,598,956 Capstafl Sept. 7, 1926 OTHER REFERENCES Proceedings ofv Panel No.. 8, National Television System Committee Description of CBS Color Television (Doc. 139B), pages 4- and 5.

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