US2480571A - Color television - Google Patents

Description

Aug. 30, 1949. c. Go| D'MARK' COLOR TELEVISION Filed Sept. 7, 1940 5 Sheets-Sheet 1 Aug. 3o, 1949. Y P. c. GQuDMARK 2,480,571 y A coLoR TELEVISIN' A Filed sept. 7', 1940 y 's sheets-sheet 2 ATTORNEYS Aug. 30, 1949.` P jc.. zaoLDMARKv 2,480,571 v COLOR TELEVISION Filedsept. 7; 1940A s sheeisfsheet s ATTORNEYS Patented ug. 30, 1949 UNITED lSTATES PATENT OFFICE Peter C. Goldmark, New York, N. Y., assignor to Columbia Broadcasting System, Inc., New York, N. Y., a corporation of New York Application September 7, 1940, Serial N0. 395,840

successively red, green and blue, this sequence beingcyclically repeated. With three primary colors, either double or quadruple interlacing may be method of scanning and reproducing an image in natural colors kwhich gives good color rendition and preserves detail in the image under widely varying color conditions, Without requiring an excessive transmission band and without objectionable iiicker. The invention also contemplates the provision of apparatus for scanning areas in accordance with the method of the invention.

It has heretofore been suggested to. achieve color television by transmitting successively images correspondingto theprimary colors in the object transmitted. The three-color system,

employing red, green and blue iilters, is usuallyemployed. Inthissystem each transmitted image represents the whole of the object scene as viewed through the corresponding niter, as distinguished from an interlaced scansion. The system is therefore open to the usual objection of excessive flicker, unlessthe images are transmitted at a high speed. The required high rate of transmission, since the images are complete, requires an excessive transmission band if detail is to be preserved. To reduce iiicker, it has also been proposed to simultaneously transmit the red, green and blue images over separate channels, but such a system is undesirably complex.

A system for the interlaced scansion of images in color has also been suggested, but in this system each set of lines always represents the saine color in the object eld. With such a system, if the object neld happened to be all red, for example, or predominantly red, only the red set of lines would be transmitted, the other set or sets ofvlines being negligible. Thus a considerable amount of detail would be lost.

In accordance with the present invention, image areas are scanned in a plurality of interlaced iield scansions, successive iield scansions corresponding to dierent primary colors. However, within a complete cycle, each set of interlaced lines represents each of the primary colors. With this system, if the color of the object field is predominantly one of the primary colors, that color will be successively transmitted by different sets of interlaced lines so that no detail will be lost. To accomplish this result, the sets of interlaced lines and the number of primary colors are made non-multiples of each other, and both the sets of lines and the primary colors alternate in regular sequence. For example, if three primary colors are employed, eldI scansions are employed, or in general, any number of sets of lines which is a non-multiple of the number of primary colors. The several interlaced sets of lines are also scanned in regular cyclically recurring sequence.

By employing the system of the invention, excellent color rendition and adequate detail can be\ obtained within the present standard television band for black and white pictures without objectionable icker'. hereinafter described the theoretical resolution of the color images is somewhat less than that of black and white images, for the same band width. However, it is found that the eiect on the eye of the addition of color satisfactorily compensates for the theoretical loss of resolution.

The invention will be more readily understood by reference to the drawings and to the following detailed description thereof.

In the drawings:

Fig. 1 represents schematically a double-interlaced scanning pattern;

Fig. 2 represents a scanning sequence suitable for use in a double-interlaced, three-color system;

Fig. 3 represents schematically'a quardupleinterlaced scanning pattern;

Fig. 4 represents a scanning sequence suitable for use with a three-color, quadruple-'interlaced system;

Fig. 5 illustrates diagrammatically a television color-nlm transmitter employing a continuously moving nlm, adapted for use with the scanning sequence of Fig. 2;

Figs. 6, '7 and 8 are detail views of elements ofthe scanning apparatus of Fig. 5;

Fig. 9 is a diagram illustrating the scanning of a film-frame during successive scansion periods;

Fig. 10 illustrates diagrammatically a colornlm transmitter employing an intermittently moving nlm;

Fig. 11 illustrates a scanning sequence for the apparatus of Fig. 10 when transmitting in accordance with the system of Fig. 2; and

Fig. 12 illustrates diagrammatically a color television receiver adapted for use with the systems of the invention.

. Fig. 1 illustrates a conventional double-interlaced scanning pattern composed of one set of lines a, and a second set of lines b interlaced with the a lines. The pattern is scanned in the usual manner, one set oi lines, say thea lines, being In some specic embodiments scanned from top to bottom in a so-called fieldscansion period. The b lines a then scanned during the next neid-scansion period. The frequency with which the scanning point returns to the starting corner is referred to as the "ield frequency" and the transversal of the iield as one eld scansion. regardless of whether every second. fourth, etc. line is traced at each traversal. The frequency with which every line of the eld is scanned is referred to as the e frequency or image frame frequency. this being one-half, one-quarter, etc., of the field frequency, depending on whether double, quadruple, etc., interlacing is used. Y

Referring to Fig. 2, a scanning System is illustrated for use with a double-interlaced, threecolor system. The sawtooth wave represents the low-frequency or vertical scanning wave. Alternate scanning waves are marked a and the intervening scanning waves marked b, indicating the respective set of lines being scanned during that field scansion period. Below each wave is indicated, by way of example. the respective color being scanned at that time.` The letters R. G and B are used to denote red, green and blue, these being selected as representative of a three-color system. Of course, other primary colors may he employed, if desired, in accordance with well known principles of color reproduction. It will be noted that the interlaced sets of lines cyclically recur in regular sequence, and that the colors cyclically recur in regular sequence. However. the first red image is formed by the a lines, and the second red image formed by the b lines. Similarly` esch of the other colors is composed successively of a and b lines. After six scansion periods, each color has been reproduced by each set of lines, whereupon the cycle begins again.

For convenience, suitable legend has been placed on Fig. 2. The term "image ileld is applied to a single scansion of one set of interlaced lines. 'I'he term image frame is applied to' two iield scansion periods dining which both seis of lines are scanned, although they are scanned in different colors. The term color icld is applied to the period during which each color is reproduced once, or the period between succemive scansions of the same color, this being equal to three field scansion periods. The term "color frame is applied to the period within which each color is reproduced by each set of lines.

At the present time the standards for black and white transmission call for the reproduction of pictures by double-interlaced scansion, with a iield frequency of 60 iield scansions per second. This gives a frame frequency of 30 frames per second. In the present system, in order to improve color rendition without iiicker, it is proposed to increase the ileld frequency to. say, 120 field scansion per second, thus making the image field period $520 second. This gives an image frame period of $60 second, a color iield period of 1/40 second, and a color frame period of 1150 second, as indicated in Fig. 2. These specific values are of course given for purposes of illustration only. If the eld period were changed, the other periods would be changed accordingly.

With the speciiic values given in Fig. 2, all three colors are reproduced within 40 second, each color being reproduced by one set of lines. Assuming the most disadvantageous case in which theimageisailoneprimarycolor,sayred,a redimagewillbereproducedbyeithertheaorb lines at intervals of 340 second, and a complete redimageformedbybothsetsoflineswillbe reproduced within lo second. Thus serious difiiculties due to flicker are avoided. Also, no detail is lost since both set of lines are reproduced in this color. Of course, in most instances at least small amounts of the other primary colors will be present so as to assist in reducing flicker.

Auming a transmission band width just sufiicient to reproduce the full detail of 441 lines per frame for black and white pictures, in accordance with present standards, the equivalent resolution of the system of Fig. 2 will be 44h/72me lines per frame. Although the resolution for color is somewhat lower due to the fact that the iield frequency has been increased, the addition oi color compensates for the theoretically lower denition and yields a very satisfactory image. Of course, a wider band would permit greater deiinition.

Figs. 3 and 4 illustrate a quadruple-interlaced system. Such a system, although somewhat more complicated than the double-interlaced system of Fig. 2, has the advantage that it provides higher deiinition for the same band Width. Fig. 3 illustrates the conventional system of quadruple-interlaced scansion. Lines a are iirst scanned from upper left to lower right, then the lines b halfway between the lines a are scanned from upper left to lower right, then lines c and lines d. Of course, the present invention is not limited to the scansion of the four sets of lines in the particular order given.

Fig. 4 illustrates a scanning sequence in which successive saw-tooth waves correspond to successive sets of lines. The image field period is assumed, for example, to be M30 second. Successive sets of lines correspond to successive colors, yielding a vcolor field period of V60 second as shown. The image frame, during which each set of lines is scanned once, is Q5 second. A complete color frame, during which each color is reproduced by all of the four sets of lines, is 5&5 second. Even if the image were all red, the fact that component red images recur at V30 second intervals reduces dicker, and the fact that the red image is reproduced by all four sets of lines yields full definition.

Assuming again a band width just suicient to reproduce 441 lines per frame at a double-interlaced eld frequency of 60 deld scanslons per second, as ilxed by present standards, the equivaient denition for the color system of Fig. 4 would be 441V=360 lines per frame. This represents an increase in definition over that of Fig. 2 for the same band width. As in the case of Fig. 2, further definition could be obtained by a broader band.

In Fig. 4, in parentheses, are given the periods for an assumed iield scansion period of 1/120 second. The color iield is 1/m second, the image geld 1/ao second, and the color 'frame 1/10 second. With such values, full 441 line definition could be obtained with present standards. To reduce interline flicker, the scanning lines could be increased to 550, for example.

It will be noticed that in both Figs. 2 and 4, the number of colors, namely three, is not a multiple of the number of sets of lines. which are two and four, respectively. Also, the number of sets of lines is not a multiple of the number of colors. This non-multiple relationship yields the advantageous result that each color is repro- 'I5 duced successively by a diderent set of lines. Ii

a diderent number or ors or a diile'rent num-v ber oi sets oi lines were employed, this non-multiple relationship could be preserved and the advantagesof the present invention retained.

Fig. illustrates a nlm scanner' suitable for use with the systems of' the invention.v The apparatus is particularly ldesigned lor use with standard motion picture sound nlm requiring an average rate of reproduction of 24 iilm frames per second, and for use with the scanning system of Fig. 2. A film IB, threaded over sprockets Il, is driven with continuous uniform movement by motor I2 at the required rate of 24 ilhn frames per second. The nlm is of the color type, for example, of the Technicolor or Kodachrome type. The lm gate I3 is illuminated with light from a suitable projection source such as the arc 'Il and condenser lens I5. Other sources of light could of course be employed. The illm gate is longer than that of a single iilm frame in order to permit each film frame to be scanned a plurality of times during its travel through the gate. In the specific embodiment described, the iilm gate is designed to expose an area of the same width and 8/5 the height of a lm frame.

The system for projecting images from the iilm to the cathode I6 of the scanning tube I'I, here shown as a tube of the Farnsworth Image Dissector type, is a modification of that shown in Figs. 13 and 14 of my copending application Serial No. 210,607, filed May 28, 1938, for Method and apparatus for television," now Patent No. 2.287.033. As there described, the projection lens I8 is positioned to form an enlarged virtual image of the iilm in a plane behind the iilm, such as plane i9. Small lenses I, 2, 3, 4 and 5 operatesuccessively to project virtual images in the plane I9 to the cathode I6 of the image dissector. The small lenses I-5 are rendered successively operative by the shutter disk 2l driven by motor I2. The shutter disk is illustrated in Fig. 6, and consists of an opaque disk having slots I', 2', 3', t' and 5' cut therein. As the disk rotates, these slots successively uncover the small lenses.

In the path of light from the lm is positioned a color disk 22. This disk is illustrated as located between the plane of the lm and the projection lens i8. However, it might also be placed on the opposite side of the rllm or at any convenient location between the plane of the illm and the cathode I6 of the image dissector. The disk should be designed and located so that the cathode I6 is illuminated with light of successive primary colors during successive eld scansions. When positioned as shown, the disk may be constructed as shown in Fig. 7. 'I'he disk should be large enough so that each lter segment R. G, B successively covers the lm gate, and large enough so that the transfer from one color sector to the next takes 'place during a blanking period. If desired. the

lter segments may be constructed in the manner described in my copending application Serial No. 355,839, :tiled concurrently herewith, now Patent No. 2,304,081. An infrared lter is placed in 'amsn s ously Theheatdiskisillustrafedin It willbe that with a scanning device of the non-storage type it is necessary to illuminate a line of the film only at the time that particular line is being scanned. The heat disk therefore contains slots I", 2", 3", 4" and 5", extending through equal central angles, one for each o! the small .projection lenses I 5. For the speciilc case illustrated, slots I" and 5" are continuations of each other. For a dierent specinc.

embodiment, this might not be true. The width oi the slots is such as to expose only a fraction of a film frame to light from the projection source at any one time. In the limiting case this might be one line, but to avoid diiliculties due to curvature of the slots and the necessity of maintaining very accurate phase relationships, the slots are preferably made wide enough to cover a number o! scanning lines at a time. The construction of the slots will be explained more fully hereinafter, after consideration has been given to the manner in which the iilm is scanned.

Referring to Fig. 9, two adjacent iilm frames 25 and 26 are illustrated in the positions which they occupy in the lm gate during five successive held-scansion periods I, II, III, IV and V of film frame 25, and I' of lm frame 26. It will be understood that since the nlm-frame period is 21; second and the ield-scansion period 1/120 second, iive eld scansions will take place during one nlm-frame period. Also. the lm frame moves downwardly a distance of VSH, where H is the heighth of a nlm frame, during each iield scansion period.

At the beginning of the rst field-scansion period, the villm frame 25 is in the position shown at I. Small lens I is rendered operable by slot I' in the shutter disk and the image of film frame 25 is projected onto the cathode i6 of the image dissector. The electron image in the image dissector is deflected by suitable means (conventional and therefore not shown) to scan horizontal lines oi the ilm frame at line-scanning frequency. The electron image is also deflected by suitable means (not shown) in a vertical dlrection to scan the image in a vertical direction at eld-scanning frequency.

Since the nlm is continuously moving downwardly, the vertical deection of the electron image need be only %H, in order to scan the full heighth of the iilm frame during the scansion period. At the end ofthe first eld scansion the ilm frame 25 has reached the position shown at II. Projection lens 2 is thereupon rendered operable by slot 2' of the shutterdisk and the same illm frame rescanned from bottom to top. Since double interlacing is employed, the eld scansion I will be of one set of lines, say the a lines, and field scansion II will be of the b lines. The required interlacing may be produced in the usual manner. At the end of eld scansion II, the film frame 25 will be in position shown at III. The a lines of the same illm frame will then be rescanned from bottom to top. This procedure is repeated for the remaining field scansion periods IV and V. 'I'he cycle is then repeated and the next lm frame 26 scanned in similar manner. It will be noted that the b lines of film frame 26 will be scanned during the ilrst field scansion period I'. Successive field scansions will alternate between a lines and b lines. The dotted lines of Fig. 9 indicate diagrammatically the deilection of the scanning beam.

As explained in my copending application :filter for scansion period In. The colors are then repeated for successive field scansion periods, R and G being operable for scansion periods IV and V. The blue filter B is operable during eld scansion I of the next iilm frame 26. It will be noted that for any given nlm frame, two colors are reproduced by both sets of interlaced lines but the third color by only one set. The particular color reproduced in only one set of lines changes for successive hlm-frame periods, and the single color reproduction alternates between a and b lines. Therefore no diiiiculty arises.

Continuing the description of the heat disk of Fig. 8 in conjunction with Fig. 9, slot i" is operable during ileld scansion I. The beginning oi the slot exposes the lower lines of the lm frame 25 and as the heat disk rotates, slot I" progresses toward the top of the lm frame to expose areas as they are scanned. Since the ilm frame moves downward 1/5H during the iield scansion period, the end of the slot need be displaced' radially only %H with respect to the beginning thereof. For scansion period II, slot 2" operates and exposes iilm frame 25 in the same manner as in the previous scansion period, theslot beginning at the bottom of the lm frame and progressing toward the top as the disk rotates. The beginning and end of slot 2" is displaced lnwardly a radial distance of H with respect to the beginning and end of slot I", to compensate for the displacement of the continuously moving illm during the rst scansion period. Slots 3", 4" and 5" are positioned in a similar manner to expose film frame 25 during respective scansion periods III. IV and V. Corresponding points of successive slots will be displaced inwardly a radial distance of MSH to compensate for lm movement. At the end of the iilm frame period, slot I" again comes into operation to expose the succeeding film frame 26 during field scansion I' of that lm frame, etc.

The shutter disk 2I, the color disk 22, the hea disk 23 and the lm I0 are all driven by the same motor I2, in order to preserve proper synchronous relationships. For the speciiic embodiment disclosed, the eld frequency is 120 field scansions per second, the lm is driven at a. rate of 24 illm frames per second, shutter disk 2I rotates at 1440 R. P. M., the color disk 22 at 2400 R. P. M. and the heat disk 23 at 1440 R. P. M. Suitable coupling means are provided between the several disks, the lm drive and the motor to secure these relationships. Also, the deiiection system (e. g., a saw-tooth wave generator) and the motor are maintained in synchronous relationship.

As shown in Fig. 9, the lm gate needs to be iii-,H in height, in order that each lm frame may be scanned iive times as it passes through the apparatus.

It will be clear that the apparatus of Fig. 5, as described, operates to scan the lm in accordance with the scanning system of Fig. 2, and yields a video signal of which successive portions represent diierent color aspects and diierent sets oi lines of an object eld, as will be clear from Fig. 2. It should be pointed out that the term image frame" is not synonymous with nlm frame, nor is the term frame-scanning frequency identical with film-frame frequency. Image frame period relates to the scanning of a ileld in both a lines and b lines, and frame-scanning frequency relates to the frequency of repetition of both a lines and b lines. On the other hand, nlm-frame period relates to the period during which a single lm frame is scanned, and lmframe frequency relates to the rate at which illm frames pass through the apparatus. The difference will be clear by consideration of Figs. 2 and 9.

The heat disk 23 may be employed in other types of ilm scanners wherein it is desired to expose only a portion of the lm frame area at any one time, the particular area exposed progressing as scanning proceeds. The number of slots and shape of the slots may be altered in accordance with the particular scanning device with which it is used.

Referring to Figs. 10 and 11, apparatus is shown employing an intermittently moving film. Film I0 is drawn through gate I3 by an intermittent film moving mechanism of suitable construction, not shown. In this embodiment the film gate need expose only the area of one lm frame. The film in the gate is illuminated by a suitable projection source such as the arc I4 and condenser lenses I5. Images in the lm gate are projected by lens 3| to the mosaic 32 of the scanning device, here shown as a tube 33 of the storage type. As examples of such tubes, the Iconoscope and "Orthicon may be mentioned. Suitable scanning means (not shown) for scanning the mosaic in horizontal and vertical directions are pro vided.

Sincethe scanningv tube is a storage device, it is desirable to project the image onto the mosaic 32 only during the blanking period. Therefore a flashing shutter 34 driven by motor 35 is provided. Shutter 34 is opaque, and has openings therein at suitable intervals so that as the disk rotates, the mosaic is periodically exposed to light from the illm image. Preferably the openings are of such shape as to expose all parts of the mosaic equally, as is known in the art. A color illter disk 36, which may be of the same type as shown in Fig. '1, is also disposed in the path of light from the image to the mosaic. If desired, it could of course be placed near the plane of the film on either side thereof as shown in Fig. 5.

Fig. ll illustrates diagrammatically the scanning procedure'. At the left of the gure, V' represents the last field scansion of a given iilm frame. During the blanking period immediately preceding this scansion, the iield frame is projected through the blue lter B by a light pulse 31. The light pulse should be of suiiieient intensity to adequately eXDOse the mosaic oi the scanning tube even though the duration of the pulse is very short. The b lines of the lm frame -are scanned during this iield scansion. During the scanning, the ilm is moved to the next iilm frame.

At the end of the iield scansion V', the succeeding film frame is projected onto the mosaic through the red lter R by a light pulse 38. The a lines of the iilm frame are thereupon scanned during scansion period I. During the next blank- -ingperiod the mosaic is exposed momentarily through the green lter G and the b lines scanned f during field scansion II. scansion proceeds during periods III, IV and V in the manner indicated in Fig. 11. During scansion period V the film is moved to the next film frame, and the scanning procedure repeated beginning with I", except that the b lines are scanned first.

The scanning system of Fig. 4, when an image field period of l/iao second is used, is not as conveniently adapted for use with the usual commercial motion picture sound lm as that of Fig. 2, since the field scansion period of l/ 1an second is not as conveniently related to the iilm' frame frequency of 24 frames per second. The system may of course be used with specially re-. corded film designed for use with the Wstem.v With an image eld period of 1/120 second, the system of Fig. 4 may conveniently be used with ordinary sound motion picture film. Both the systems of Figs. 2 and 4 may be used with direct pickup devices.

Fig. 12 illustrates receiving apparatus suitable I for reproducing images in color in accordance with the systems described hereinbefore. The cathode-ray reproducing tube 4l, which may be of conventional type. is provided with the usual pair of horizontal deilecting plates 42 and vertical deiiecting plates 43. These are suitable for electrostatic scanning and may, of course, be replaced by corresponding coils for electromagnetic deflection. The horizontal deflecting plates 42 are energized by the saw-tooth generator 44 at line-scanning frequency, and the vertical deflecting plates 43 are energized by generator 45 at naald-scanning i'reouency. Conventional means may be employed for securing double, quadruple or other interlaced scanning patterns in accordance with the invention. These are known in the art and hence need not be described in detail. An electron beam generated by the electron gun 45 is deflected by the pairs of plates and scans a field'on the end of the tube. The end of the tube is covered with fluorescent material 41 to reproduce visual images.

In front of the tube. and preferably closely adjacent thereto. is positioned a color filter disk 48. This disk may be of the form shown in Fig. '7, and is rotatable about axis 49 by a motor 5|.

. The motor is synchronized with the field scanning. and the driving ratio between the motor and the disk is selected with respect to the number of color sectors so that successive interlaced images are exhibited through successive color sectors. That is. the lter sectors traverse the end of the tube at held-scanning frequency. The disk should be of large enough diameter to vobscure the scanning lines on the uorescent screen at the time they are scanned. Also. it is advantageos to have the lines obscured for a considerable interval after scanning, so that the lines are exhibited through the proper color filter during the period of afterglow. The lter disk may advantageously be constructed in the manner described in my copending application, Ser. No. 355,081. filed concurrently herewith, now Patent No. 2,304,081.

For transmitters employing storage tubes, instead of employing an intermittently moving film, a continuous film projector which projects a stationary image could be employed.

It will now be appreciated that the present invention provides scanning systems of general utility for both direct pickup and fllm scanning,

particular apparatus described herein, the apparatus being for purposes of illustration only. Modifications are of course possible which come within the spirit and scope of the invention as described and claimed herein.

What I claim is:

1. In color television. the method of scanning a eld which comprises scanning said field in a plurality of interlaced iield scansions, successive interlaced field scansions corresponding to different colors of a plurality of primary colors. said plurality of primary colors and said plurality of interlaced field scansions being non-multiples of each other.

2. In color television transmitting and receiving systems, the methodoi scanning which comprises scanning a field in a plurality of cyclically recurring interlaced field scansions, successive eld scansions corresponding to different colors of a plurality of cyclically recurring primary colors, said plurality of primary colors and said plurality of interlaced field scansions being non-multiples of each other and said field scansions recurring at the rate of at least 120 fields per second, whereby each set of interlaced scanning lines cyclically corresponds to each of said primary colors and objectionable color :dicker may be avoided.

3. In color television transmitting and receiving systems, the method of scanning which comprises successively scanning a plurality of interlaced sets of lines of a field during respective successive field scansion periods, successively scanned sets of lines corresponding to different colors of a plurality of cyclically recurring primary colors, said plurality of interlaced sets of lines and said plurality of primary colors being non-multiples of each other and said field scansions recurring at the rate of at least 120 fields per second, whereby eachset of interlaced scanning lines cyclically corresponds to each of said primariar rotors and objectionable color iiicker may be avoided.

4. In color television transmitting and receiving systems, the method of scanning which comprises cycllcally scanning a field in two interlaced sets of lines at the rate of at least 120 eld scansions per second, said sets of lines being successively scanned during respective eid scansion vperiods, to form a double interlaced scanning and at receivers. It will be understood that the transmitting said video signal to a reproducer,

scanning systems are not coniined to use with the pattern, said field scansions corresponding successively to three cyclically recurring primary colors, whereby each primary color cyclically corresponds to each set of interlaced lines and objectionable color flicker may be avoided. 5. In color television transmitting and receiving systems, the method of scanning which comprises cyclically scanning aield in four interlaced sets of lines at the rate of at least field scansions per second, said sets of lines being successively scanned during respective eld scansion periods to form a quadruple interlaced scanning pattern, said eld scansions corresponding successively to three cyclically recurring primary colors, whereby each primary color cyclically corresponds to each set of interlaced lines and objectionable color flicker may be avoided.

6. In television, the method of transmitting and reproducing images in color which comprises scanning an object field at the transmitter in a plurality of interlaced field scansions to thereby generate a video signal, successive interlaced eld scansions corresponding to dierent colors of a plurality oi' primary colors, said plurality of primary colors and said plurality of interlaced iield scansions being non-multiples of each other,

and reproducing from said video signal by said reproducer successive interlaced images corresponding to successive interlaced field scansions, successive interlaced images being reproduced in respective different colors of a plurality or primary colors, said plurality of interlaced images and said plurality of primary colors at the reproducer being non-multiples of each other.

7. In color television, a transmitting scanning device for scanning an imagefield in a plurality of interlaced eld scansions, successive interlaced iield scansions corresponding to different colors of a plurality of primary colors, said plurality of primary colors and said plurality of interlaced field scansions being non-multiples of each other, means for transmitting signals corresponding to said eld scansions to a receiver, and means at said receiver for reproducing from said signals interlaced eld scansions in colors respectively corresponding to said eld scansions,

8. In color television, means for projecting a Vlight image of an object eld to a transmitting scanning device, means associated with said scanning device for scanning said object eld in a plurality of successive interlaced eld scansions at the rate of at least 120 eld scansions per second, means for successively interposing in the path of light of said scanning device during successive field scansion periods a plurality of different color filters, said plurality of interlaced ield scansions and said plurality of color lters being non-multiples of each other, means for transmitting signals corresponding to said field scansions to a receiver, a reproducing scanning device at said receiver adapted to reproduce from said signals interlaced eld images corresponding to said interlaced field scansions, and means associated with said reproducing scanning device ior exhibiting successive iield images in colors respectively corresponding to said eld scansions, whereby improved color rendition may be obtained and objectionable color flicker avoided.

9. In a color television transmitter, the combination which comprises scanning means for scanning an image field in a plurality of interlaced iield scansions at the rate of at least 120 field scansions per second, means associated with said scanning means for successively presenting diierent color aspects of said image field to the scanning means during respective eld scansion periods, the means for presenting different color aspects being correlated with the scanning means so that each of said color aspects is cyclically scanned by different sets of interlaced lines, whereby a signal providing improved color rendition without objectionable color flicker may be obtained.

10. In a color television transmitter, the combination which comprises scanning means for scanning an image eld in a plurality of interlaced iield scansions, means associated with said scanning means for successively presenting a plurality of primary color aspects of said image iield to the scanning means during respective iield scanslon periods. said plurality of primary-colors and said plurality of interlaced eld scansions being non-multiples of each other and said eld scansions recurring at the rate of 120 per second or more, whereby each color aspect is cyclically scanned by different sets of interlaced lines to improve color rendition and objectionable color icker is avoided.

11. In a color television transmitter, the cornbination which comprises a scanning device for scanning an image eld in a plurality of cyclically v recurring interlaced lield scansions at the rate of 120 field scansions per second or more, means associated with said scanning device for successively presenting a plurality of cyclically recurring primary color aspects of said image iield to the scanning device during respective eld scanslon periods, said plurality of primary colors and said plurality of interlaced field scansions being nonmultiples of each other so that each color aspect is cyclically scanned by dilerent sets of interlaced lines, whereby a signal providing improved color rendition without objectionable color iiicker may be obtained.

12. In a color television transmitter, the combination which comprises scanning means for successively scanning a plurality of interlaced sets of lines of an image iield during respective successive eld scansion periods, means associated with said scanning means for successively presenting a plurality of cyclically recurring primary color aspects of said image field to said scanning means during respective successive lield scansion periods, said plurality of primary colors and said plurality oi interlaced sets of lines being non-multiples of each other and said field scansions recurring at the rate of 120 per second or more, whereby each set ot interlaced scanning lines cyclically corresponds to each of said primary colors to improve color rendition and objectionable color iiicker is avoided.

13. In a color television transmitter, the combination which comprises a scanning device for successively scanning a plurality of interlaced sets ci' lines of an image iield during respective successive iield scansion periods, a color lter device interposed in the path of light to said scan ning device and adapted to expose said scanning device successively to diierent colors of a plu- Cil rality of primary colors of said image field, saidl plurality of primary colors and said plurality of interlaced sets of lines being non-multiples of each other. and means for synchronizing said color iilter device and said scanning device to expose said scanning device to said different colors successively during respective successive iield scansion periods, whereby each set of interlaced scanning lines cyclically corresponds to each of said primary colors, said eld scansions recurring at the rate of 120 per second or more to avoid objectionable color flicker.

14. In a color television transmitter, the combination which' comprises a scanning device for cyclically scanning an image field in two sets of interlaced lines, said sets of lines being successively scanned during respective neld scansion periods at the rate of at least 120 eld scansions per second to form a double interlaced scanning pattern, means amociated with said scanning device for successively presenting to said scanning 50 device three cyclically recurring primary color aspects of said image field during respective successive iield scansion periods, whereby each primary color is cyclically scanned by each set of intei-laced lines to improve color rendition and obljectionable color flicker is avoided.

15. In a color television transmitter, the combination which comprises a scanning device for cyclically scanning an image eld in four sets of interlaced lines, said sets of lines being successively scanned during respective field scansion periods at the rate of at least 120 i'leld scansionv per second to form a quadruple interlaced scanning pattern, means associated with said scanning dcvice for suocsively presenting to said scanning device three cyclically recurring primary color aspects of said image field during respective successive iield scansion periods, whereby each primary color is cyclically scanned by each set of interlaced lines to improve color rendition and objectionable color flicker is avoided.

16. In a color television receiver, the combination which comprises scanning means for reproducing images in a plurality of successive interlaced field scansions at the rate of at least 120 field scansions per second, means associated with said scanning means for presenting successive field scansions in diiierent primary colors, said means for presenting different primary colors being correlated with said scanning means so that each of said primary colors is successively presented by different sets of lines of the interlaced i'leld scansions, whereby improved color rendition may be obtained and objectionable color icker avoided.

17. In a color television receiver, the combination which comprises scanning means for reproducing images in a plurality of successive interlaced eld scansions, means associated with said scanning means for presenting field scansions in a plurality of successive primary colors during respective iield scansion periods, said plurality of primary colors and said plurality of interlaced field scansions being non-multiples of each other and said field scansion recurring at the rate of at least 120 per second, whereby each color cyclically corresponds to diil'erent sets of interlaced lines to improve color rendition and objectionable color icker is avoided.

18. In a color television receiver, the combination which comprises a scanning device for reproducing images in a plurality of successive cyclically recurring interlaced field scansions, means associated with said scanning device for presenting field scansions in a plurality of cyclically recurring primary colors during respective field scansion periods, said plurality of primary colors and said plurality of interlacediield scansions being non-multiples of each other and said field scansions recurring at the rate of at least 120 per second, whereby each color cyclically corresponds to different sets of interlaced lines to improve color rendition and objectionable color flicker is avoided.

19. In a color television receiver, the combination which comprises a scanning device for successively reproducing a plurality of interlaced sets of lines of an image during respective successive field scansion periods recurring at the rate of at least 120 per second, means associated with said scanning device for successively presenting said interlaced sets of lines in a plurality of cyclically recurring primary colors during respective successive iield scansion periods, said plurality of primary colors and said plurality of interlaced sets of lines being non-multiples of each other, whereby each set of interlacedlines is-` cyclically presented in each of said lprimary colors to improve color rendition and objectionable color flicker is avoided. I

20. In a co-lor television receiver, the combination which comprises a scanning device for successively reproducing a plurality of interlaced each other, and means for synchronizing s aid color filter device and said scanning device to present said different colors successively during respective successive vfield scansion periods, said field scansion periods recurring at the rate of per second or more, whereby each set of interlaced lines is cyclically presented in each of said primary colors to improve color rendition and objectionable color ilicker is avoided.

21. In a color television receiver, the combination which comprises a scanning device for reproducing an image in two sets of interlaced lines. said sets of interlaced lines being successively reproduced during respective successive field scansion periods recurring at the rate of 120 per second or more to form a double interlaced image, means associated with said scanning device for successively presenting said sets of interlaced linesv in three cyclically recurring primary colors during respective successive field scansion periods, whereby each primary color is cyclically presented by each set of interlaced lines to improve color rendition and objectionable color flicker is avoided.

22. In a color television receiver, the combination which comprises a scanning device for reproducing an image in four sets of interlaced lines, said sets of interlaced lines being successively reproduced during respective successive eld scansion periods recurring at the rate of 120 per second or more to form a quadruple interlaced image, means associated with said scanning device for successively presenting said sets of interlaced lines in three cyclically recurring primary colors during respective successive field scansion periods, whereby each primary color is cyclically presented by each set of interlaced lines to improve color rendition and objectionable,

color flicker is avoided.

23. An interlaced multiple-color television scanning system comprising, means for periodically scanning the image to be transmitted or reconstructed in frames of n interlaced fields, and means for periodically changing the color of illumination associated with successive fields not greater than m times per ield and in a series of m colors, the ratios of n to m and of m to n both being non-integral so that corresponding fields of -successive frames are associated ywith illumination of different colors.

24. In color television, the method of scanning a field which comprises scanning said ileld in a plurality of interlaced eld scansions, successive interlaced eld scansions corresponding to difterent colors of a plurality of primary colors, said plurality of primary colors and said plurality of interlaced field scansions being non-multiples of each other and said field scansions recurring at the rate of at least 120 elds per second to avoidobjectionable color flicker.

25. In television, the method of transmitting and reproducing images in` color which comprises scanning an object field at the transmitter in a plurality of interlaced eld scansions at the rate of at least 120 field scansions per second to thereby generate a video signal, successive interlaced field scansions corresponding to diilerent colors of a plurality of primary colors, said plurality of primary colors and said plurality of interlaced field scansions being non-multiples of each other, transmitting said video signal to a reproducer. and reproducing from said video signal by said reproducer successive interlaced images corresponding to successive interlaced field scansions, successiveinterlaced images being reproduced in respective diiierent colors oi a plurality of primary colors, said plurality of interlaced images and said plurality of primary colors at the reproducer being non-multiples of each other, whereby improved color rendition may be obtained and objectionable color flicker avoided.

26. In color television, a transmitting scanning device for scanning an image field in a plurality of interlaced iield scansions at the rate of at least 120 iield scansions per second, successive interlaced field scansions corresponding to diilerent colors of a plurality of primary colors, said plurality of primary colors and said plurality of interlaced eld scansions being non-multiples of each other, means for transmitting signals corresponding to said eld scansions to a receiver, and means at said receiver for reproducing from said signals interlaced eld scansions in colors respectively corresponding to said field scansions, whereby improved color rendition may be obtained and objectionable color iiicker avoided.

REFERENCES CITED The following references are oi record in the 111e of this patent:

` UNITED sTA'ms PATENTS Great Britain Oct. 25, 1938 OTHER REFERENCES Fernseh A. G. (Fernseh Atkiengesellschaft, Berlin) 1. Band Beit 5, Aug. 1939, Pases 171 to PETER C. GOLDMARK. 25 179,

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