US3465331A - Interpolation device - Google Patents

Description

Filed Oct. 21. 1965 pt 2, 1969 o. TROTSCHER 3,465,331

' INTERPOLATION DEVICE s Sheets-Sheet 1 Sept. 2, 1969 TROTSCHER 3,465,331

' INTERPOLATION DEVICE Filed Oct. 21, 1965 5 Sheets-Sheet 2 Sept. 2, 1969 o.1-Ro1'scHr-:R

INTERPOLATION DEVICE 5 Sheets-Sheet :5

Filed Oct. 21. 1965 United States Patent m 3,465,331 INTERPOLATION DEVICE Otto Triitscher, Aalen, Wurttemberg, Germany, assignor to Carl Zeiss-Stiftung, doing business as Carl Zeiss, Wurttemberg, Germany, a corporation of Germany Filed Oct. 21, 1965, Ser. No. 499,735

Claims priority, applicatilon Germany, Nov. 6, 1964,

Int. Cl. H041 3/00; H0 3k 13/00; G06f 7/38 US. Cl. 340-347 2 Claims ABSTRACT OF THE DISCLOSURE An interpolation device for digital interpolation in which an electron beam is moved continuously in a closed circular path over a plurality of electrically conductive screen elements arranged in a circle and extending radially from a common center. The screen elements are arranged in at least three separate groups which are electrically separated from each other. The pulses produced by the screen elements are fed into a selection circuit which permits a prefix-correct counting of said pulses.

In the aforesaid patent specification are disclosed two basically different screen element arrangements which allow for counting with prefix consideration the interpolation values of a primary signal. The target of the electron beam, for example, the anticathode of a cathode ray tube, consists in both of these prior arrangements of individually insulated screen units having similar screen constants and being oifset against each other by an amount equal to one quarter of the screen constant. In one arrangement the two screen units are disposed concentrically in. a single target plane, and in the other arrangement, the two screen units are located one in rear of the other along the axis of the cathode ray tube, whereby in the last mentioned case the screen struck first by the electron beam is in the form of a grid or diaphragm screen letting through only about 50% of the total electrons in the beam.

, Both of these prior arrangements are difficult to employ in actual practice. The first arrangement requires that the electron beam oscillate at a very high frequency in radial direction of the screen units in order to scan over the inner as well as the outer unit. To obtain such action of the electron beam entails complicated circuitry. The latter arrangement necessitates measures for rendering inefiiective the secondary electrons released at the diaphragm screen, because the contrast of the original signal must be constant over the whole circular surface of the screen unit in order to obtain reliably correct counting.

It is one object of the present invention to overcome these difficulties by grouping the screen elements in cyclic Patented Sept. 2, 1969 sequence into at least three separated screen element groups and by connecting each group to an electrical selective circuit, which arrangement makes possible a prefix-correct counting of pulses occurring at the screen elements.

In case the screen elements are arranged in a single target plane, the spaces or gaps between the single screen elements are preferably made about the same width as the width of the electron beam at the point of impingement. When observing this relationship, the hysteresis will be a minimum on direction reversal of counting.

According to another object of the invention, the screen elements of adjacent groups are arranged so that the gaps left by one group are taken by the elements of the other group lying in a plane slightly in rear of the first group. Thus it is possible by a given number of screen elements to arrange them Within a smaller diameter and in turn to employ a smaller cathode ray tube.

The selective circuit connected to each screen element group includes, for instance, a bistable multivibrator or flip-flop in direct connection to the output lead for preparing trigger tubes or thyratrons associated with each channel either for forward or backward counting, and includes furthermore counting-pulse-generating monovibrators. The pulse release of the monovibrator is initiated by flipping of the appertaining bistable multivibrator in a predetermined direction. By a reversal of the counting pulses, the multivibrators are later returned to their original condition.

Fundamentally there is always a direction identification possible when information groups follow in succession which consist of at least three unrelated and independent informations. When designating the three informations, for example, with A, B and C, it is possible to arrange the circuits in such a manner that by progressive counting from A through B to C, an addition will be performed;

whereas by a response of the information in reversed di- With such arrangement, for instance, it is possible to obtain forward and backward counting of a hundreds inter-.

polation with four screen element groups of twenty-five elements each, when the element groups are insulated from one another and their elements are intermeshed in regular order so that the elements of each group are equally spaced around a common center.

In order to more fully'understand the invention, a detailed description of a few preferred embodiments will now be given with reference-to the accompanying draw-- ings, in which:

FIG. 1 is an elevation view of a screendisc carrying a four-group arrangement of screen elements;

FIG. 2 illustrates diagrammatically a circuit diagram of a selector circuit suitablefor interpolating the. pulses derived from the screen disc of FIG. 1;

FIG. 3 is a diagram indicating the relationship between screen element width, interspace width and width of the impinging electron beam; and

FIG. 4 shows a linearly stretched layout of screen elements disposed in two adjacent parallel planes whereby the rear elements are located in the spaces between the front elements.

The screen disc diagrammatically illustrated in FIG. 1 comprises several electrically conducting screen elements, the total number of which is divisible by four, but only the screen elements numbered 1 to are shown. The screen elements are insulated from one another by being arranged in spaced relation from one another and by being inserted in a nonconductive center core K. Furthermore, the screen elements are connected as shown alternately in cyclic succession each to one of the individually insulated ring conductors L1, L2, L3 and L4. In the embodiment shown, for example, the screen elements 1, 5, 9 and so forth (only the first three are shown) are connected to ring conductor L1, the screen elements 2, 6, 10

r and so forth are connected'to ring conductor L2, the

screen elements 3, 7 and so forth, to ring conductor L3, and finally the'screen elements 4, 8 and so forth, to ring conductor L4. Each one of the ring conductors L1, L2, L3 and L4 is connected to terminal contacts A, B, C and D, respectively, and these terminal contacts are grounded through resistors W1, W2, W3 and W4 respectively. An electron beam striking substantially normal the face of the screen disc and travelling to trace a substantially circular path thereon, will strike successively every screen element, and in striking will produce an electric charge in that particular element. Such charges will flow through the respective ring conductor and resistor to ground, producing thereby a voltage at the respective terminal contacts A, B, C or D.

The voltage so produced are utilized in a subsequent selector circuit of which one example is schematically illustrated in FIG. 2. Here the four voltages or informations derived from the screen arrangement of FIG. 1 are applied for forward and backward counting. For this purpose, the circuit has four input channels A, B, C and D- with provisions for connecting to the correspondingly marked terminal contacts of FIG. 1. The reference characters referring to components and elements belonging to a particular channel carry the corresponding subscript, i.e., A, B, C or D. The first stage in each channel is an amplifier marked correspondingly S S S or 8;, followed by respective Schmitt triggers T T T or T The amplifiers are so designed that each time the electron beam travels across a screen element, the output potential L at the respective trigger jumps to 0. It may be mentioned here that the triggers may be omitted when the amplifiers are controlled to render step-rise output signals. The trigger output leads are connected each to the left preparation input lead of the respective bistable flip-flop F F F or F Each flip-flop can accept at a time one of two stable potential steps L or O, and can be flipped into one or the other of these conditions by corresponding input pulses. The diagonal lines marked on the flip-flop circuit symbols are for indicating the condition of a certain flip-flop. It is'assumed that the fulllined diagonals indicate the condition under which the left bottom output lead of the respective flip-flop has the potential 0 and the right bottom output lead the potential L, while the diagonals in dash-lines indicate reversed potentials. Connected to the left top input leads of all flip-flops is a pulse generator G serving to introduce pulses of a considerably higher frequency than the actual counting frequency. The left bottom output leads of the flip-flops are connected each to the input of a forward thyratron V V V V of one adjacent channel and also to the input of a backward thyratron R R R R of the other adjacent channel. These forward and backward thyratrons are all in the form of plus-grids, i.e., they pass pulses only when both of their input connections receive a pulse simultaneously. The right bottom output connections of the flip-flops F F F and F are connected to monovibrators M M M and M respectively, and the latter again to the second input connections of both the forward and backward thyratrons belonging to the same channel as the respective monovibrator. The monovibrators produce a counting pulse of definite duration.

The output leads of all forward thyratrons V V V and V are all connected to inputs of a thyratron V forming an Or-grid or barrier, i.e., it passes each single pulse no matter on which one of the input leads it arrives; and the output leads of all backward thyratrons R R R and R are connected to inputs of another thyratron R which is also in the form of an Or-grid. The output leads of the thyratrons V and R are connected respectively to the forward counting device Z and the backward counting device Z and besides, both output leads to the inputs of a further thyratron T serving also as an Or-grid. The output lead of thyratron 'T connects through an interposed reversing stage U to all four right top inputs of the flip-flops F F The diodes 20-27, connected to the right side input leads of the prepreparation circuits of the flip-flops serve for direction-depending coupling and uncoupling of adjacent flipflop circuits.

The operation of the selector circuit illustrated in FIG. 2, when connected to a screen arrangement as shown in FIG. 1, is as follows:

Assuming that the electron beam at the beginning of its travel strikes, for example, first the screen element 3 (FIG. 1) connected to the output terminal contact C which is joined to input of channel C (FIG. 2). The potential or voltage change resulting from the beam impact on screen element 3 is thus passed through the amplifier S and, as amplified, causes trigger T to jump from potential L to potential 0. This action readies the associated flip-flop F so that pulses arriving from the pulse generator G are able to flip P into the counting condition indicated by the diagonal shown in a dash line. The resulting voltage jump from L to O at the right bottom outlet of flip-flop F acts on monovibrator M whose impulses, however, can pass neither thorugh thyratron R nor V because these thyratrons are not yet readied. By flipping of flip-flop F there are readied only the backward thyratron R and the forward thyratron V which are both connected to the left bottom outlet of this flip-flop now at potential L.

The counting position thus attained remains now temporarily in the channel connected to lead C.

When now the electron beam continues on its path and travels from screen element 3 to screen element 4 (FIG. 1), the channel connected to terminal D comes under the influence of a voltage surge caused by the striking beam, and flip-flop F is acted on to change to the condition indicated by the diagonal shown in a dash line. This change acts on monovibrator M Whose impulse can pass only through the forward thyratron V since this thyratron has previously been readied by flipflop F The counting impulse thus passed can now progress through thyratron V to the forward counter Z of the counting device causing it to move one digit in the positive counting direction. Moreover, this same impulse passes parallel to its first path also through the Orgrid T and, after reversal in the reversing stage U, as

negative impulse to the right top inlets of all four flipflops. However, only flip-flop P will be affected and returned to its original condition, because only this one is readied by the adjacent flip-flop F by way of the diode 22. This flip action from potential 0 to L causes no impulse at monovibrator M Consequently, only flip-flop F remains in counting position.

When now the electron beam, continuing in the same direction of travel, reaches screen element 5 (FIG. 1),

the channel connected to terminal A of the selector circuit becomes active. The voltage surge, resulting from the impact of the electron beam, causes in this channel similar occurrences of forward counting as described in the previous paragraph with reference to channel D. This will be clearly understood from FIG. 2.

The operations for backward counting will now be explained: Assuming for this purpose that the electron beam reverses its direction of travel and moves from screen element 4 to screen element 3 (FIG. 1). The result is a voltage surge again in channel 3. The subsequent counting impulse, leaving multivibrator M, can now pass only through thyratron R because only this one is readied by the flip-flop F which has not been returned but remained in counting position as previously stated. The impulse, after passing through R progresses through backward thyratron R to the backward counter Z of the counting device and reaches, along the same parallel path as described with reference to the forward counting cycle, the right top inlets of the flip-flops, affecting now, however, only flip-flop F in returning it to its original condition. Namely, only this flip-flop is now readied by the adjacent flip-flop P by way of the diode 21.

Analogous occurrences take place in all other screen element circuits and counting channels whenever the electron beam strikes a respective screen element. The circuits and functions of their components when passing a pulse through a particularchannel will be clear from FIGS. 1 and 2, and the detailed description above.

' When arranging the screen elements in a single plane as, for example, shown in FIG. 1, care must be taken that the width of the spaces between the individual screen elements is in proper relationship to the diameter of the electron beam at the point of impact. If, for instance, as shown in FIG. 3, the width D of the screen elements 1' and 2 is equal to the width D of the space between these elements and the diameter D of the electron beam is considerably smaller, then there is produced during a reversal of the counting direction (reversal of movement direction of the electron beam into opposite direction of travel) a hysteresis that can be equal to the width of the space D i.e., about 50% of the space between the screen elements.

Since it is conventional to allow in known counting devices operating with photoelectric emitters only a hysteresis of about to it is essential that the width of the space D between the screen elements is not considerably wider than the diameter D, of the electron beam in the plane of the face of the screen unit.

For example, if a screen unit of ten elements has an effective diameter of 20 mm. with a relationship of element width to interspace width of one to one, and the diameter of the electron beam in the plane of the screen unit is 0.5 mm., the hysteresis will be about 50%. When now, with the same electron beam diameter, the interspace width is reduced to, say, 0.6 mm., the hysteresis will drop to about 10%.

Similar considerations apply to a cathode ray interpolator with coded screen. Here it is also important that the relationship between gap and web is coordinated with the diameter of the cathode ray so that at reversal of the rotational direction in the cathode ray motion, the hysteresis amounts to not more than about 10% to 20.%

In the aforedescribed embodiment of the invention, all of the screen elements are disposed in a single plane. With a great number of screen elements, such an arrangement leads to large diameter screen discs which in turn require large cathode ray tubes because their face must include the whole disc area. It is possible, however, to reduce this screen disc diameter for a given number of elements by distributing these elements, for example, in two adjacent parallel planes one in back of the other. An example of such an arrangement is shown in FIG. 4 and includes the screen elements 1", 3", 5", 7" in the front plane toward the tube cathode and, in a parallel plane in spaced relation in rear thereof and in the interspaces between the front elements, the screen elements 2", 4", 6", 8". The width of the spaces between the screen elements of the front plane are equal to the width of the screen elements in this plane. FIG. 4 indicates the screen elements in a linear arrangement, but it will be understood that the same principle can be employed in a circular arrangement of the screen element. The screen elements of such arrangement, all insulated from one another, can be combined into four screen groups with output leads A, B, C and D, as illustrated in FIG. 1, and, in connection with a selector circuit of FIG. 2, can be used for prefix-correct counting.

With a screen disc having a total of ten screen elements, it is advisable to divide this number into five groups of two elements each, for instance, the elements 1 and 6 for one pair, the elements 2 and 7 for the second pair, 3 and 8 for the third pair, 4 and 9 for the fourth pair, 5 and 10 for the fifth pair. The five output leads of these five pair groups can then be connected to a selector circuit like the one illustrated in FIG. 2 but extended by another channel.

What I claim is:

1. An interpolation device for digital interpolation of period signal sequences employing a continuously revolving electron beam which continuously moves in a closed circular path in rhythm of the signal frequency, including a plurality of electrically conductive screen elements arranged to extend radially from a common center and spaced from each other for a successive subdivision of said closed circular path, said screen elements being combined and arranged in cyclic succession alternately in at least three separate groups of screens which are electrically insulated from each other, means forming a selection circuit, and means for connecting said groups of screen elements to said selection circuit, said selection circuit including means permitting a prefix-correct counting of the pulses produced by said screen elements, said selection circuit further including bistable multivibrators, the inputs of which are connected each with the 'output of said screen element groups and which prepare thyratrons associated with the individual channels for counting forward and in reverse, and impulse producing monovibrators which create each a counting impulse of definite duration as soon as the bistable multivibrator, which is arranged in front of said monovibrator, flips in a predetermined direction from a stable position into the other, whereby the negative counting impulses are returned to the multivibrators and the latter are returned to their initial position.

2. An interpolation device for digital interpolation of period signal sequences employing a continuously revolving electron beam which continuously moves in a closed circular path in rhythm of the signal frequency, including a plurality of electrically conductive screen elements arranged to extend radially from a common center and spaced from each other for a successive subdivision of said closed circular path, said screeen elements being combined and arranged in cyclic succession alternately in at least three separate groups of screens which are electrically insulated from each other, means forming a selection circuit, and means for connecting said groups of screen elements to said selection circuit, said selection circuit including means permitting a prefix-correct counting of the pulses produced by said screen elements, said spaced screen elements being arranged in spaced parallel planes one behind the other and perpendicular to the longitudinal axis of the electron beam, one plane having arranged therein along a circle a number of even numbered screen elements, and the next adjacent plane having arranged therein along a circle a number of oddnumbered screen elements, whereby the center portions of the screen elements in one of said planes are disposed to cover the spaces between the screen elements arranged in the next adjacent plane.

References Cited UNITED STATES PATENTS i igg l at aliii 4; MAYNARD R. WILBUR, Primary Examiner Starr 340-347 M. K. WOLENSKY, Assistant Examiner Wingate 340347 X I Barwicz et a1 3158.5 10

Rantsch et a1. 340347X

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