US2741724A - Image-reproducing device - Google Patents

Description

April 1956 w. o. REED IMAGE-REPRODUCING DEVICE Filed Nov. 27, 1951 FIG. 1

Monochrome Receiver Color- Switching Device FIG.2

INVENTOR. WILLIAM O. REED 5 HIS ATTOR EY.

United rates Patent 0 lMAGE-REPRGDUCING DEVICE William 0. Reed, Chicago, 111., assignor to The Rauiand Corporation, a corporation of Illinois Application November 27, 1951, Serial No. 258,322

6 Claims. (Cl. 313-78) image and are, of course, subject to a certain amount of unavoidable noise and other mechanical difficulties. Other systems approach the problem from an all-electronic point of view and employ a specially constructed image-reproducing device incorporating a multicolor fiuorescent screen. Some of these devices utilize complex fluorescent screens constructed of elemental triangular pyramids having different phosphors disposed on the respective faces so that the color response of the device is dependent on the angle of incidence of the electron beam at the screen surface. A similar cflect has been realized by employing a planar type of multicolor fluorescent screen in conjunction with a parallax grid or mask provided with a plurality of apertures corresponding in configuration and space distribution with the screen area coated with any one particular phosphor. In most of these arrangements, however, color switching has been achieved either by employing separate electron guns for exciting the several phosphors constituting the composite fluorescent screen or by subjecting the electron beam originating at a single electron gun to a color-switching deflection field to control the angle of approach of the electron beam with respect to the parallax mask or the pyramidal multicolor screen. The use of plural electron guns is obviously undesirable from an economic point of view, in addition to which multigun tubes generally require rather more complicated external circuitry in their application to a television receiver. If a single gun is employed in the manner known to the prior art, a convergence system such as a magnetic electron lens must be provided to insure registration of the images corresponding to the several primary colors as well as to provide proper focusing of the beam on the screen.

It is an important object of the present invention to provide a new and improved device for the reproduction of images in natural color.

Still another object of the invention is to provide a color-image reproducing device of simplified construction which does not require the use of cumbersome mechanical filter systems.

Yet another object of the invention is to provide a new and improved single-gun color-image reproducing device in which the necessity of employing a convergence system to insure proper image registration and beam focusing is obviated.

In accordance with the present invention, a new and improved color-image reproducing device comprises a fluorescent screen composed of a plurality of interspersed similar groups of similar elemental target areas, each group exhibiting a different color-radiation response char acteristic to electron bombardment than the remainder of the groups. An electron gun is provided for projecting toward the fluorescent screen an electron beam of crosssectional area small relative to the entire surface area of the screen. A mask is interposed between the electron gun and the fluorescent screen in a plane generally perpendicular to the path of the beam and is provided with a plurality of apertures corresponding in configuration and space distribution to one of the groups of elemental target areas, and a decelerating electrode is disposed between the electron gun and the mask. A deflection-control system is disposed between the mask and the fluorescent screen for subjecting electrons projected from the gun through the mask to a transverse deflection field to control the color of fluorescence of the screen.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood, however, by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference numerals indicate like elements, and in which:

Figure l is a fragmentary cross-sectional view of a color-image reproducing device constructed in accordance with the invention, together with a schematic representation of the associated receiver apparatus; and

Figure 2 is a plan view of an element of an alternative embodiment of the invention.

As illustrated in Figure l, a new and improved colorimage reproducing device constructed in accordance with the present invention comprises an evacuated envelope it at one end of which is provided a multicolor fluorescent screen 11. Fluorescent screen 11 is composed of a plurality of interspersed similar groups of similar elemental target areas, each group exhibiting a different colorradiation response characteristic to electron bombardment than the remainder of the groups. Specifically, fluorescent screen 11 may be of the tricolor variety, and the interspersed groups of elemental target areas may be formed of different screen phosphors respectively responsive in each of the three primary colors red, blue and green. While numerous phosphor materials for providing the desired spectral response are well known in the art, a screen having the desired properties may be provided by employing manganese-activated zinc silicate as the green-fluorescing phosphor, titanium-activated calcium-magnesium silicate as the blue-fluorescing phosphor, and manganese-activated cadmium borate as the redfluorescing phosphor.

An electron gun, comprising a cathode 12, an intensitycontrol electrode or grid 13, and a pair of accelerating anodes 14 and 15, is provided at the opposite end of the envolope from fluorescent screen 11 and is situated on an axis passing perpendicularly through the center of fluorescent screen 11. A mask 16, having a plurality of apertures corresponding in configuration and space dis tribution to one of the groups of elemental areas of the fluorescent screen, is disposed between the electron gun and the screen in a plane generally perpendicular to the axis of the electron gun and generally parallel to the fluorescent screen. A deflection-control system, which preferably comprises a pair of coaxial cylindrical electrodes 17 and 18 having mesh-covered complemental angular truncations 19 and 2G, is disposed between mask 16 and fluorescent screen 11. Other electrodes may also be provided, as for example an additional accelerating anode 2i and a decelerating electrode 22 in the form of 24 between deflection- control electrodes 17 and 18 and fluorescent screen 11. An electronpermeable metal bacle ing layer 25 may also be provided for fluorescent screen 11 to intercept positive ions and provide improved brightness.

Composite color-video signals are received by means oi an antenna 3.3 and impressed on the input circuits ot a conventional monochrome television receiver 31. The detected video-signal components from monochrome receiver 3.1 are applied between control grid 13 and cathode 12, to control the intensity of the electron. beam. Line-frequency and field-frequency scanning signals from mQnQQhIQmc receiver 3.1 are impressed on a deflection Yoke. 52 d sposed around the neck of envelope It to impart a scanning motion to, the. electron beam. Monochrome QQQ Ycr 31 is also. coupled to a color'switch'mg device 33 which Provides suitable, color-control signals in response to the coloresynchronizing components of the eceived composite co or-video sign l.- These color-con- O s nal r co pled to flection-control electrodes 17 a d y m n of UPl Be-QQd'bIQCKiQ nn n r .4 nd .5 r spe iv ly- S itable. operating pcientials arc pp o node 14 nd 1 by means at a p entiometer. 36 connected in parallel with a source of unidirec ional operating potential such as a battery 37. In a similar manner, electrodes 21, 22 and 12,3 and mask 1.6. are maintained at suitable unidirectional operating potentials by means of a potentiometer 38 connected in Parallel with an operating potential source such as; a battery 39. Deflection-control electrodes. 17 and 18- are. returned to a potentiometer 48 connected in parallel with a source of unidirectional operating potential, h Qre shown, as a battery 41, by. means of respective resistors 42 and 43, and accelerating electrode 24 and metal backing layer 25, are directly connected to the positive. terminal of battery 41 While the system of Figure 1 may be employed for the reception of field-sequential, line-sequentialor dotsequential composite color-video signals, or of composite color-video. Signals of the simultaneous type, it is perhaps most convenient to explain the operation of the system in connection with received cQmposite color-video signals of the ficldrscquential type. MOIEDYEE, the interra gr up of: lemental t rgetarcas. may b om P f he l ne clemen or. dot. elemen s, depending on yp o ransmi 11,, so long as m sk. 16 is prQ= 'd h p rtur W i. h correspond. in. configurationand space distribution to one of the interspersed groups e en areas; for p rposes otexnlanaticn, a. creen 11 of the line-element type will heassumjed',

in operation, received composite color-video, signals are. detected by monochrome receiver circuits31 Anelectron beam, controlled in intensity in accordance with the vid.eosignal components, isproj ected toward fluorescent screen 11, Since mask 1'6 is provided with apertures similar in configuration and space distribution to one of the interspersed groups of elemental targetareas, i, e., the redfiuorescing phosphor areas, those electrons which pass through mask 16- at any instant of time are permitifidi toimpinge only on the elemental areas of one phosphor group, regardless of the instantaneous scanning deflection to which the beam is subjected. Upon emerging from. the apertures in mask 16", the space electrons may pass undeflected to fluorescent screen 11 or may be deflected upwardly or downwardlyas-viewed in Figure 1, depending onthe potential difference between defiection-controlelec trodes 17 and 18 The'potential difference, between these twoelectrodes is determined by Color-switching device 33', which in turn is responsive to the color-synchronizingcomponents oi the received composite color-video sig; nals. By suitably arranging the interspersed phosphQii groups with respect to the direction of the deflection field established between electrodes 17 and 18, as for example by disposing the line elements of a linear tricolor screen in a direction generally perpendicular to the plane of the paper in Figure 1, it may be assured that changes of appropriate magnitude in the potential difiference between electrodes 17 and 18 will result in proper color switching with but a single phosphor energized at any given instant of time. Consequently, in the reception of colortelevision signals of the fieldssequential type, successive red, blue and green fields are reproduced on the screen and are integrated by the persistence of vision of the observer to simulate the efiect of a natural-color image reproduction.

Monochrome receiver circuits 31 may be of entirely conventional construction, and many arrangements are known for performing the function of color-switching device 33. For example, color-switching device 33 may comprise a simple stairstcp wave generator, or a commutator arrangement associated with a power supply and suitably disposed contact elements may be employed. Suitable techniques. which may be employed in manufacturing the tube. of Figure l are well known in the art and require no further explanation.

in order to avoid undesirable color contamination, parti ularly at the. edges of the reproduced image, mask 16 is so constructed. that its apertures are in substantial registraticn wih one of U36 groups of elemental target areas. with respect to the electron beam projected through the mask toward the screen. Moreover, the electron beam is passed througha decelerating field established by electrode 22 before reaching mask 16, and is strongly accelerated by electrode 23 immediately after passing through. the mask. Post-acceleration of. the beam in, this manner has a collimating effect and insures substantially perpendicular incidence. of the space electrons or fluorescent screen 11 for all deflection angles.

Alternatively, electrode 22 may be. omitted, and the mask may he so constructed that the spacing between successive apertures, proceeding radially from the: center toward the periphery, decreases in proportion to the tangent of the. angle subtended at the center of deflection. If a. tricolor screenof the dot interlace type is employed, with uniform spacing between adjacent, dots of any group across the entire screen area, the. mask element 16 is constructed inthe manner shown in, Figure 2. Moreover, the scanning circuits of receiver 31 are preferably modified to provide ascanning raster in the. plane of, mask 16 which. is slightly distorted to conform to the, modified aperture distribution; however, satisfactory color reproduction may be achieved; without so. modifying the. receiver scanning. circui ts. Of, course, in a. practical embodiment, the aper -ures are microscopicin size, and, it. should be. understood ha he. representation of Figure 2 is greatly exaggercd to, facilitate an, understanding of the. principle involved. Similar resultsv may be obtained by employing uniform spacing between, the. apertures in the mask and by increasing, the spacing of adjacent. dot elements. from the center of the. fluorescent. screen towards its. periphery in, proportion to the tangent of? the. deflection. angles, this.

arrangement is not preierred since. it is generally undesirable to add to the complexity of the. screen. forming techniques. Intermediate schemes, incorporating, bothv post-acceleration and geometric compensation. may also. be employed if desired.

The particular construction of the electrostatic deflection-control system is ofconsid'erablfc importance if, optimum results are to be achieved; When the, color-switch.- ing electrodes 17 and 18 are constructed as complementally angularly truncated cylinders in the manner. shown and described in connection with Figure 1', nonuniform fringc fi' lfisu ch s th e. cncounteredintlie use. of magnetic deflection systems and ordinary. electrostatic. deflection plates, and consequent, color, contamination are substantially avoided. The. mesh coverings 19= and. 2.0.,

while not essential, are preferred for the purpose of eliminating lens fields between electrodes 17 and 18.

In some instances, and particularly where a dot-element type of tricolor screen is employed, it may be desirable to include a second deflection-control system, in spaced quadrature with that formed by electrodes 17 and 18, between those electrodes and fluorescent screen 11 for the purpose of permitting minor adjustments of beam registration and/or to permit a more flexible control of the color-switching operation. However, a second such deflection-control system is not essential, even when a dotelement type of screen is employed, but merely constitutes a refinement of the apparatus of the present invention.

Thus the present invention provides a new and improved color-image reproducing device of the all-electronic type which is readily adaptable to use with a conventional monochrome receiver. Since the color-switching action is accomplished between the parallax mask and the fluorescent screen, no convergence system is required as in previously proposed devices. Electrical compensation for mechanical misalignment of the mask and screen may readily be effected by minor adjustment of the bias voltages supplied to the deflection-control electrodes.

Certain aspects of the tube described in connection with the present invention are disclosed and claimed in the copending application of William 0. Reed, Serial No. 255,869, filed November 10, 1951, for Color Television, and assigned the present assignee.

While a particular embodiment of the present invention has been shown and described, it is apparent that various changes and modifications may be made, and it is therefore contemplated in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

1. A color-image reproducing device comprising: a fluorescent screen composed of a plurality of interspersed similar groups of similar elemental target areas, each group exhibiting a difierent color-radiation response characteristic to electron bombardment than the remainder of said groups; a single electron gun disposed along an axis perpendicular to said screen for projecting toward said screen an electron beam of cross-sectional area small relative to the entire surface area of said screen; a mask intermediate said electron gun and said fluorescent screen in a plane generally perpendicular to the path of said beam and provided with a plurality of apertures corresponding in configuration and space distribution to one of said groups of elemental areas; an electrostatic deflectioncontrol system intermediate said mask and said fluorescent screen for subjecting electrons projected from said electron gun through said mask to a transverse deflection field to control the color of fluorescence of said screen; and an accelerating electrode between said mask and said deflection-control system.

2. A color-image reproducing device comprising: a fluorescent screen composed of a plurality of interspersed similar groups of similar elemental target areas, each group exhibiting a different color-radiation response characteristic to electron bombardment than the remainder of said groups; a single electron gun disposed along an axis perpendicular to said screen for projecting toward said screen an electron beam of cross-sectional area small relative to the entire surface area of said screen; a mask intermediate said electron gun and said fluorescent screen in a plane generally perpendicular to the path of said beam and provided with a'plurality of apertures corre sponding in configuration and space distribution to one of said groups of elemental areas; a decelerating electrode between said electron gun and said mask; an electrostatic deflection-control system intermediate said mask and said fluorescent screen for subjecting electrons projected from said electron gun through said mask to a transverse deflection field to control the color of fluores- 6 cence of said screen; and an accelerating electrode be tween said mask and said deflection-control system.

3. A color-image reproducing device comprising: a fluorescent screen composed of a plurality of interspersed similar groups of similar elemental target areas, each group exhibiting a different color-radiation response characteristic to electron bombardment than the remainder of said groups; an electron gun for projecting toward said fluorescent screen an electron beam of cross-sectional area small relative to the entire surface area of said screen; a mask intermediate said electron gun and said fluorescent screen in a plane generally perpendicular to the path of said beam and provided with a plurality of apertures corresponding in configuration and space distribution to one of said groups of elemental areas; and an electrostatic deflection-control system comprising a pair of coaxial adjacent complementally angularly truncated cylindrical electrodes intermediate said mask and said fluorescent screen for subjecting electrons projected from said electron gun through said mask to a transverse deflection field to control the color of fluorescence of said screen.

4. A color-image reproducing device comprising: a fluorescent screen composed of a plurality of interspersed similar groups of similar elemental target areas, each group exhibiting a different color-radiation response characteristic to electron bombardment than the remainder of said groups; an electron beam of cross-sectional area small relative to the entire surface area of said screen; a mask intermediate said electron gun and said fluorescent screen in a plane generally perpendicular to the path of said beam and provided with a plurality of apertures corresponding in configuration and space distribution to one of said groups of elemental areas; and an electrostatic deflection-control system comprising a pair of coaxial adjacent cylindrical electrodes provided with meshcovered complemental angular truncations intermediate said mask and said fluorescent screen for subjecting electrons projected from said electron gun through said mask to a transverse deflection field to control the color of fluorescence of said screen.

5. A color-image reproducing device comprising: a fluorescent screen composed of a plurality of interspersed similar groups of similar elemental target areas, each group exhibiting a different color-radiation response characteristic to electron bombardment than the remainder of said groups; a single electron gun disposed along an axis perpendicular to said screen for projecting toward said screen an electron beam of cross-sectional area small relative to the entire surface area of said screen; a mask intermediate said electron gun and said fluorescent screen in a plane generally perpendicular to the path of said beam and provided with a plurality of apertures in substantial registration with one of said groups of elemental areas with respect to said electron beam; a decelerating electrode between said electron gun and said mask; and an electrostatic deflection-control system comprising a pair of coaxial adjacent complementally angularly truncated cylindrical electrodes intermediate said mask and said fluorescent screen for subjecting electrons projected from said electron gun through said mask to a transverse deflection field to control the color of fluorescence of said screen.

6. A color-image reproducing device comprising: a fluorescent screen composed of a plurality of interspersed similar groups of similar elemental target areas, each group exhibiting a different color-radiation response characteristic to electron bombardment than the remainder of said groups; an electron gun for projecting toward said fluorescent screen an electron beam of cross-sectional area small relative to the entire surface area of said screen; a mask intermediate said electron gun and said fluorescent screen in a plane generally perpendicular to the path of said beam and provided with a plurality of apertures corresponding in configuration and space distribution to one of said groups of elemental areas, the spacing between l successive apertures of said mask, proceeding from the center toward the outer periphery, decreasing in proportion to the tangent of the angle subtended by the path' of said beam and said axis; and an electrostatic deflectioncontrol system comprising a pair of coaxial adjacent complementally angularly truncated cylindrical electrodes intermediate said mask and said fluorescent screen forsubjecting electrons projected from said electron gun through said mask to a transverse deflection field to control the color of fluorescence of said screen.

References Cited in the file of this patent UNITED STATES PATENTS 1,810,018 Howes June 16, 1931 8 Lubcke June 1, Parker et' al Dec. 30, Gray Sept. 15, Hansen Aug. 19, Schroeder Aug. 10, Wainwright Dec. 14, Sziklai Aug. 8, Chew Nov. 14, Okolicsanyi Dec. 5, Morton et a1. Apr; 10, szegho Aug. 21, Hansen Sept. 18, Forgue Mar. 25,

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