US2082093A - Television system - Google Patents

Description

`une 1, 1.937. A. v. BEDFORD 2,082,093

TELEVISION SYSTEM .June 1, 1937. A. v. BEDFORU 032,993

TELEVISION SYSTEM Filed Jan. 28, 1953 2 Sheets-Sheet 2 Patented June l, '1937 mural) STATES PATENT OFFICE Application January 2B, 1933, Serial 120,653,941

20 (Halma.

My invention relates to improvements in television systems.

For the purpose of eliminating dicker of the reproduced picture in a television receiver, it has been found expedient to double the usual number of frames scanned per second and, in the scanning action, to intermesh the lines of the odd pictures, for example, with the lines oi the even pictures. A receiver of this type is disclosed in detail in the copending application by Randall C. Ballard, filed July 19, 1932 and bearing Serial No. 623,325. By following this method of socalled intermeshed or interlaced scanning, it becomes practical to make the number of frames per second as high as sixty. With the' number of frames per second at sixty, the common alternating current power circuits at 60 cycles can be used to advantage for synchronizing or control purposes. A problem arises, however, when the subject ior transmission is a standard moving-picture iilm moved intermittently at the usual rate oi twenty-four frames a second.

With the foregoing in mind, it is one oi the objects of my invention to provide an improved television system and method of operation thereof whereby all the advantages of use of common alternating current at sixty cycles and the use of a standard moving-picture lm for twentyfour frames a second, can be obtained.

Other objects and advantages will hereinafter appear.

In accordance with my invention, different views of a moving subject are exposed to the transmitting apparatus for transmission, and picture signals of each of certain complete views are developed at least twice in succession.

More particularly, in accordance with my in' vention, the scanning action at the transmitter isv made to take place at the rate of sixty frames a second, the individual views are presented for scanning at the rate of twenty-four a second, and every other view is scanned twice in succession while each of the other views is scanned three times in succession.

Further, in accordance with my invention, a cathode ray tube is caused to scan screen structure at the rate of sixty frames a second. For the purpose of developing picture signals, a moving picture film which is the subject for transmission is moved intermittently. An image of each of the odd pictures, for example, is projected twice in succession onto the screen structure, and an image of each of the even pictures is projected three times in succession onto the screen structrue, all during stationary periods of the film.

The timing is such that the cathode ray scans Athe screen structure only during the periods between those during which the illm is stationary.

My invention resides in the improved system, apparatus and method of operation of the character Ahereinafter described and claimed.

For the purpose of illustrating my invention, an embodiment thereof is shown in the drawings, wherein Figure 1 is a simplied elevational view, partly diagrammatic, of a television transmitting system constructed and operating in accordance with my invention;

Figs. 2, 3, and 4 are enlarged elevational views, looking from the rear of the apparatus shown in Fig. l, and illustrating a step in the operation;

Fig.` 5 is an elevational view of one of the parts, looking toward the left in Fig. 1;

Fig. 6 is a picture chart, illustrative of the manner of operation in Fig. 1; and

Fig. 7 is an enlarged fragmentary view, taken from Fig. 5.

With reference to Fig. 1, the reference numeral l0 designates a cathode ray tube for developing picture signals. This tube comprises a suitable photosensitive, mosaic screen structure I2 which, for example, may be made up of a great number of minute, photosensitive silver globules supported on a metallic base plate and each insulated from the latter and from each other. A suitable electron gun I4 operates to develop a ray I6 of electrons and to direct the same at the screen structure. The tube is provided with a grounded anode in the form of a silver coating l1 'on the inside surface.

The ray I6 is caused to scan the screen structure during intermittent periods. During the relatively short periods between the intermittent scanning periods, the ray is returned to the initial starting point for the next succeeding scanning action. During each scanning period, the ray scans the screen along a saw-tooth path. l Let it be assumed, for example, that there are to be 60 pictures or frames a second, each having 1211/2 lines horizontally, the horizontal lines of the odd frames being intermeshed with or falling between those of the even frames. For these conditions, the ray is deflected horizontally by coils I8 through which a saw-tooth current wave is caused to pass at a frequency of 7290 cycles.

A suitable generator 20 supplies the current wave for this purpose. Also, the ray is deiiected vertically by coils 22 through which a saw-tooth current wave is caused to pass at a frequency of 60 cycles. A suitable generator 24 supplies the 60- cycle current wave for this purpose.

The electron gun I4 is provided with a control electrode or grid 26 by which the intensity of the ray is varied in the manner and for the purpose hereinafter explained.

The object for transmission is a standard motion picture film 28 moved intermittently, at the rate of 24 pictures a second, by an intermittent feed device 88. The camshaft 32 of the intermittent device is driven directly from the shaft 34 of a motor 36. The shaft 34 rotates uniformly at the rate of 30 revolutions a second, and the driving connection to the camshaft 32 is of any suitable type having a drive ratio of 1 to 21/2. The camshaft 32, therefore, makes twelvecomplete revolutions each second.

A shutter disc 38 is fixed on the motor shaft and is provided with two diametrically opposite openings 48 and 42, each of which, at its widest point, extends along one-twentieth of the circumference. The individual pictures of the film are projected onto the screen structure I2 through these openings.

The shutter openings 48 and 42 are given the characteristic shape, as shown in Fig. 5, for the purpose of permitting the maximum amount of light to pass through to the screen I2.

'I'he intermittent device 38 is provided with two cams, 44 and 46, each of which is effective to rotate the shaft 48 of the film-driving sprocket 58 through ninety degrees. This is illustrated in Figs. 2, 3, and 4. In Fig. 2, the cam surface 52 is about to engage the pin 54 to impart counterclockwise movement to the shaft 48. As the shaft 32 continues to rotate, the cam surface 56 engages the pin 58, as shown in Fig. 3, to continue rotation of the shaft 48 to the position shown in Fig. 4. The shaft 48 is thereby moved through ninety degrees, from the position shown in Fig. 2 to that shown in Fig. 4.

An important characteristic of the intermittent device 88 resides in the fact that the axis of the cam 44 is displaced less than one-hundred and eighty degrees from the axis of the cam 46, the actual displacement being one-hundred and forty-four degrees, as shown. Considering the action for each complete revolution of the shaft 32, and with reference to Fig. 6, the pictures moved into position by the cam 44 are stationary during the two periods AB and CD, while the pictures moved into position by the cam 46 are stationary during the three periods EF, GH and IJ. In other words, we will say that for each revolution of the shaft 32, there is one odd and one even picture of the film moved into position, and that each even picture is allowed to remain stationary for a 50 per cent longer period than the stationary period for the odd picture. The reason for this will hereinafter appear.

The drive ratio of l to 21/2` between the shafts 82 and 34 provides that for every 30 revolutions of the shutter disc 38, the shaft 48 of the filmdrivlng sprocket 58 will be rotated through ninety degrees twenty-four times to impart an intermittent movement to the film 28 at the rate of 24 pictures a second.

The disposition of the shutter openings 48 and 42 and the fixed adjustment between the shafts 82 and 34 are such that the relatively short periods, during which pictures are flashed onto the screen I2, occur during the periods when the pictures are stationary. This is represented in Fig. 6. `With the disc 38 rotating at the rate of 30 revolutions a second, therefore, images of the individual nlm pictures are dashed on to the screen I2 at the rate of sixty frames a second. Also, on account of the characteristic construction of the intermittent device I8 and the timing, as explained, there will be two images of each of the odd pictures flashed onto the screen I2 in succession, and three images of each of the even pictures flashed onto the screen in succession.

For the purpose of maintaining operation of the generators 28 and 24 at the respective frequencies of 7290 cycles and 60 cycles, sharp electrical impulses 68 of a given amplitude are developed at the frequency of '7290 cycles and, after passing through a suitable amplifier 62 are supplied to the generator 28 and operate to drive the same at this frequency. Also, electrical impulses 64 are developed of greater duration than the horizontal impulses, and at the frequency of 60 cycles. These are also amplified in the amplifier 62, and are then supplied to the generator 24 to drive the same at the required frequency of 60 cycles. The adjustment of the generator 24 is such that it 'does not respond to the impulses 88 for horizontalsynchronizing.

For the purpose of developing the synchronizing impulses 68, the disc 88 is provided with 243 apertures 66, evenly spaced and disposed on the circumference of a circle concentric with the axis of the shaft 34. During each revolution of the disc 38, light from a suitable source 68 passes through these apertures to a photoelectric cell 18 connected to the input circuit of the amplifier 62, thereby developing the sharp impulses 68 for maintaining horizontal defiection of the ray I6 at the rate of 7290 deflections a second. The amplified impulses are supplied to the geneator 28 through a suitable connection, as indicated.

Several of the apertures 66 are cut through to provide two elongated apertures 12 and 14, diametrically opposite to each other, and each of the same length. With the disc 38 rotating at the rate of 30 revolutions a second, the longer apertures 12 and 14 admit light to the photocell 18 for a longer period than each of the apertures 66 to develop the framing impulses 64 at the required frequency of 60 cycles for maintaining vertical deflection of the ray I6 at this frequency. These impulses are also amplified in the amplifier 62 and then supplied to the generator 24 through a suitable connection, as shown. The disposition of the framing apertures 12 and 14 is such that the same start to admit light to the cell 18 at substantially the same instant that the respective shutter openings 48 and 42 start to admit light to the screen I2.

For the purpose of causing the ray I6 to scan the screen I2 first along spaced horizontal lines for any given odd frame and then, for the following even frame, along horizontal lines between those of the preceding odd frame, the framing aperture 12, for example, is made by removing all of the material of the disc between one of the apertures 66 and each of the adjacent apertures. This is shown more clearly in Fig. 7. Since, however, there are 243 of the apertures 66, and the framing aperture 14 is of the same length and diametrically opposite to the aperture 12, the ends of the aperture 14 will fall between adjacent apertures 66. This is also shown more clearly in Fig. 7. The action, therefore, is as follows: Looking toward the right in Fig. l, the ray I6 starts at the upper left-hand corner of the screen I2 and scans the same along 1191/2 lines for an odd frame, after which a framing impulse 64 occurs to start return deflection of the ray vertically. Assuming that return deflecpoint B. the

tion vertically occupies the period for two full deflections horizontally, when the ray starts to scan the screen for the succeeding even frame, it will have been deflected horizontally 1211/2 times and will be directed at the center of the upper horizontal edge of the screen and slightly above horizontal line #1. During the next 1191/2 horizontal deflections, for the succeeding even frame, therefore, the ray will scan the screen I2 along horizontal lines between or displaced from those of the preceding odd frame, and at the end of the 241st deflection will be directed at the lower right-hand corner of the screen. At this time, another framing impulse B4' occurs to start return deflection of the ray vertically. This return deflection, as' before, occupiesthe period for two full deflections horizontally, so that when the ray is directed at the upper left-hand corner of the screen, it will have been deflected horizontally exactly 243 times. For convenience, it has been stated previously that each frame compirses 1211/2 horizontal lines, but from the foregoing it will be understood that each frame loses two lines because it has been assumed that the period of two lines elapses during each return deflection vertically.

It will be understood that picture signals are only developed as the ray is deilected horizontally from left to right and vertically from top to bottom. During return deflection of the ray from right to left, horizontally, and also during return deflection of the ray vertically, the ray serves no useful purpose in the way of developing picture signals. It is, therefore, desirable to out off the ray during return deflection thereof in both horizontal and vertical directions, and for this purpose the synchronizing and framing impulses are taken from a suitable stage of the amplifier 62 and applied by a connection 16 to the control grid 26. The polarity and amplitude of each of these impulses is such as to impart a negative bias to the grid 26 which is effective to cut off the ray so that it will be non-effective with respect to the screen I2.

The operation of my improved system will now be further explained, with reference to Fig. 6, which is a chart representative of the entire operating action for each complete revolution of the shaft 32. From the point A clockwise to the point B, the opening 4D is in position to permit an image of an odd film picture (picture #1) to be projected onto the screen I2. During this period, also, the elongated aperture 'I4 is effective to develop a framing impulse 64 which drives the generator 24 to effect return deflection vertically of the ray, and, at the same time, to impart a negative bias to the grid 2B to cut off the ray during the return deflection thereof. At the shutter 32 cuts off all light to the screen i2. At this point, the negative bias on the grid 2B will have been removed to restore the ray to normal intensity. Also, deflection of the ray for scanning the screen begins, and occupies a period from point B clockwise to the point C. During the scanning period, therefore, the screen I2 is dark. At the point C, the opening 42 is in position to permit a second image of picture #l to be projected onto the screen I2. During this period, the elongated aperture 12 is effective to develop another framing impulse B4 which again drives the generator 24 to effect return deflection vertically of the ray, and, at the same time,

to impart a negative bias to the grid 26 to cut oi the ray during this return deflection thereof. At the point D, the shutter cuts off all light to the screen I2. At this point, the negative bias on the grid 26 will have been removed to restore the ray to normal intensity. Also, deflection of the ray for scanning picture #l the second time begins, and occupies a period from the point D clockwise to the point E. During the period D to E, therefore, the screen is dark. At the point D, the cam 46 starts to move the next and even picture (picture #2) into position, and completes this movement at the point E. At the completion of the scanning action, at the point E, the ray is again cut off by the action of the aperture 14, and the shutter opening 40 starts to admit light to the screen I2. From the point E to the point F, an image of the picture #2 is flashed onto the screen I2 through the opening l0. The operating action then continues as above with the following exception. On account of the characteristic construction of the intermittent device 30, picture #2 is permitted to remain stationary from thc point F to the point G. The screen is dark from the point F to the point G, during which period the screen is scann-ed. During the period G to H, the ray is cut 01T and a second image of picture #2 is flashed onto the screen I2 through the opening 42. During the period H to I, the screen is dark and is again scanned by the ray I6. During the period I to J, the ray is cut off and a third image of picture #2 is flashed onto the screen I2 through the opening 40. At the point J, the cam 44 starts to move the next odd picture (picture #3) into position. During the period J to the screen is dark and is scanned by the ray I6. At the point A, the cycle of one complete revolution of the shaft 32 is completed. At this point, the ray is cut off, and from the period A to B, an image of picture #3 is flashed onto the screen I2 through the opening 42. The action then continues as before.

With regard to the operating action which takes place in developing picture signals, it will be understood that when an image of a picture is flashed onto the screen during each of the relatively short periods AB', CD, EF, GH and IJ, electrostatic charges are stored on the screen, the value of the stored charge at the particular area of the screen being proportional to the value of light intensity at the corresponding elemental These signals are supplied by way of a connection 'il to a suitable amplifier 18. The amplified synchronizing impulses are also Supplied to this amplifier from the amplifier B2, as indicated, and are then passed with the amplified picture signals to a suitable radio transmitter 20.

From the foregoing, it will be seen that by my improved system and method of operation, it is possible to take advantage of the use of the common alternating current supply at 60 cycles for synchronizing or control purposes, and to accommodate the transmitter under these conditions for standard moving-picture film as the subject for transmission and which is fed intermittently through the apparatus at the rate of 24 frames a second, or, at least, at a rate different than the scanning rate in terms of frames per second.

Another important advantage in my improved system and method of operation, whereby it is feasible to use alternating current supply at 6J cycles, resides in the fact that both the respective frequencies for vertical and horizontal deflection of the ray are even multiples of the supply frequency of 60 cycles. Hence, all disturbances resulting from imperfect iiltering of the amplier voltage supplies at the transmitting and receiving stations are stationary with respect to the reproduced picture and are, therefore, less objectionable than would otherwise be the case.

I believe myself to be the iirst to provide a television transmitting system of the character described wherein the individual views are pre-` sented for transmission at a rate different than the scanning rate in terms of frames per second, and wherein, in order to allow for this, certain of the views are scanned m times, while other views. occurring between said certain views are scanned n times, m and n being whole numbers and one oi these numbers being greater than the other.

While but one embodiment of my invention has been disclosed, it is seen that modifications, within the conception of those skilled in the art, are possible without departing from the spirit of my invention or the scope of the claims.

I claim as my invention:

1. 'Ihe method of operating a television transmitter including a cathode ray transmitter tube having a light-sensitive screen which comprises projecting different succeeding views of a subject to be transmitted upon said screen, scanning each of the alternate views projected on said screen m times in succession with said cathode ray to develop picture signals, and scanning each of the other views projected on said screen n times in succession with said cathode ray to develop picture signals, wherein m and n are whole numbers and wherein one number is greater than 'the other, the time required for m plus n scannings being equal to the time required for projecting a whole number of picture frames upon said screen.

2. 'I'he method of operating a television trans- 'mitter including the cathode ray transmitter tube having a light-sensitive screen which comprises projecting different succeeding views of a subject to be transmitted upon said screen, scanning alternate views projected on said screen twice in succession with said cathode ray to develop picture signals. and scanning the other views projected on said screen three times in succession with said cathode ray to develop picture signals.

3. The method of operating a television transmitter including a cathode ray transmitter tube having'a light-sensitive screen which comprises scanning said screen with said cathode ray at the rate of 60 complete scannings per second, moving individual views into position for projection upon said screen at the rate of 24 per second, projecting the alternate views upon said screen twice in succession and in such time relation with respect to said scanning that said alternate views are scanned twice on said screen to develop plcture signals, and projecting the other views upon said screen three times in succession and in such time relation to said scanning that said other views are scanned three times each to develop picture signals.

4. The method of operating a television transmitter including an intermittent device for moving a motion picture iilm into position for scanning which comprises moving one picture frame of said film into position for scanning, scanning said picture frame m times in succession to develop picture signals, moving the next picture frame into position for scanning, and scanning said next picture frame n times in succession to develop picture signals, wherein m and n are whole numbers and wherein one number is greater than the other, the time required for m plus n scannings being equal to the time required for projecting a whole number of picture frames upon said screen, and repeating said operation for succeeding picture frames'.

5. The method of transmitting a television picture wherein a moving picture film is a subject for transmission which comprises imparting in` termittent movement to said nlm at the rate of 24 frames per second and scanning each of said picture frames at the rate of 60 frames per second in such time relation to said intermittent movement that every other frame is scanned twice in succession to develop picture signals and each of the remaining frames is scanned three times in succession -to develop picture signals.

6. The method of operating a television transmitter including a cathode ray transmitter tube having a light-sensitive screen and wherein the moving picture film is a subject for transmission which comprises moving said film intermittently at a certain average rate in terms of picture frames per second into position for projecting said picture frames upon said screen, projecting at least twice in succession upon said screen the same image of each of said picture frames. and scanning said screen with said cathode ray at a different rate in terms of frames per second than said certain average rate where said certain average rate goes into said scanning rate a whole number of times plus a fraction and in such time relation to the projection of said picture frames upon said screen that the cathode ray scans in succession complete images of said picture frames.

7. The method of operating a television transmitter including a cathode ray transmitter tube having a light-sensitive screen and wherein a moving picture Iilm is a subject for transmission which comprises moving said film intermittently at a certain rate into position for projecting each picture frame upon said screen, projecting m times in succession upon said screen the same image of each of alternate picture frames, projecting n times in succession upon said screen the same image of each of the remaining picture Yframes, wherein m and n are whole numbers and V wherein one number is greater than the other, and scanning said screen by said cathode ray at a rate in terms of picture frames per second which is different than said certain rate and in such time relation that the cathode ray scans successively images of complete picture frames whereby picture signals representative oi complete picture frames are developed for transmission.

8. The method of operating a television transmitter including a cathode ray transmitter tube having a light-sensitive screen and wherein a moving picture iilm is a. subject for transmission which comprises scanning said screen with said cathode ray during spaced periods of time and at a given rate in terms of picture frames per second, imparting the intermittent movement to said film at a different rate in terms of picture frames per second than said given rate, and projecting upon said screen images of certain of the picture frames at least twice. in succession and only during the space periods of time intervening said scanning periods and projecting images of picture frames intervening said certain picture frames upon said screen' a different number of times than said certain picture frames, and maintaining such time relation between said projections and said scanning that the cathode ray scans images of complete picture frames to produce picture signals representative of picture frames for transmission.

9. The method of operating a television transmitter including a cathode ray transmitter tube having a light-sensitive screerr and wherein a moving picture film is a subject ior transmission which comprises scanning said screen with said cathode ray during spaced periods of time and at the rate of 60 picture frames per second, moving said film intermittently at the rate of 24 picture frames per second into position for projecting each picture frame upon said screen, projecting upon said screen the image of every other picture twice in succession and only during the spaced periods of time intervening saidy scanning periods, and projecting the remaining intervening pictures three times in succession upon said screen and only during the spaced periods of time intervening said scanning periods.

10. In a television system wherein a movingpicture lm is the subject for transmission, scanning apparatus for developing picture signals, means for moving said lm intermittently into position for scanning each picture frame, means including said scanning'apparatus for scanning each of certain complete picture frames at least twice in succession, and means for maintaining said intermittent movement and said scanning action in such time relation that complete picture frames are scanned successively.

ll. In a television transmitting system, scanning means for developing picture signals comprising a cathode ray tube provided with screen structure, means for causing the ray to scan said structure at a given rate in terms of frames per second, means for supporting a moving-picture film and imparting an intermittent movement thereto at a different rate in terms of pictures per second than said given rate, means for projecting onto said structure images of the individual lm pictures and for projecting each of certain of said pictures at least twice in succession, and means for maintaining said intermittent movement and said scanning action in such time relation that complete picture frames are scanned successively.

12. In a television transmitting system, scanning means ior developing picture signals comprising a cathode ray tube provided with lightsensitive screen structure, means for causing the ray to scan said structure at the rate of sixty frames a second, means for supporting a moving-picture ilm and imparting an intermittent movement thereto at the rate of twenty-four pictures a second, means for projecting twice in succession onto said structure an image of every other picture and for projecting three times in succession onto said structure an image of each of the pictures intervening the pictures projected twice, and means for maintaining such time relation between said scannings and said projections that each picture frame image on said screen is completely scanned before the next picture frame image is projected on said screen.

13. In a television transmitting system, scanning means for developing picture signals comprising a cathode ray tubeprovidedwith light-sensitive screen structure, means for causing the ray to scan said structure during spaced periods of time at a given rate in terms of frames per sec- 75 ond, means for supporting a moving-picture nlm and imparting thereto an intermittent movement at a different rate in terms of pictures per second than said given rate, and means cooperating with said scanning means for projecting onto said structure images of certain of the pictures at least twice in succession and only during the spaced periods of time intervening said scanning periods.

14. In a television transmitting system, means for developing picture signals comprising a cathode ray tube provided with screen structure, means for defiectlng the ray to cause the same to scan said screen structure during spaced periods of time at a given rate in terms of frames per second and along different sets of parallel lines during succeeding frame periods, the lines of one set being disposed between uthe lines of another set, means Afor supporting a moving-picture lm and imparting thereto an intermittent movement at a different rate in terms of pictures per second than said given rate, and means cooperating with said scanning means for projecting images of certain of the picture frames at least twice in succession onto said structure and only during the spaced periods of time intervening the spaced scanning periods.

15. In a television transmitting system in which a moving-picture film is the subject for transmission, a cathode ray transmitter tube having a light-sensitive screen, means for moving said lm into position intermittently for projecting an image of each picture frame upon said screen with the intermittent movement such that alternate picture frames of the film remain in position for projection longer than the remaining picture frames, means for projecting images of each of said alternate picture frames upon said screen three times in succession with a period following each projection and for projecting images of each of said remaining picture frames upon said screen twice in succession with a period following each projection, and means for scanning said screen with said cathode ray during said periods to develop picture signals representative of said picture frames.

16. In a television transmitting system in which a moving-picture lm is the subject for transmission, a cathode ray transmitter tube `having a light-sensitive screen, means `for moving said film into position intermittently at the rate of 2.4 picture frames per second for projecting an image of each picture frame upon said screen with the intermittent movement such that alternate picture frames of the lrn remain in position for projection longer than the remaining picture frames, means for projecting images of each of said alternate picture frames upon said screen three times in succession with a period following each projection and for projecting images of each of said remaining picture frames upon said screen twice in succession with a period following each projection, and means for scanning said screen with said cathode ray during said periods to develop picture signals representative of said picture frames, said scanning being at the rate of 60 picture frames per second.

1'7. In a television transmitting system in which a moving picture nlm having picture frames is the subject for transmission, means for intermittently moving said film into position to be scanned at a certain rate in picture frames per second, means for scanning each of certain individual frames at said rate a predetermined number of times and developing picture signals in accordance with said scanning, and means for scanning each oi' said other individual frames located between said first-mentioned individual frames at said rate a different number of times and developing picture signals in accordance with said latter scanning.

18. In a television transmitting system in which a moving picture film having picture trames is the subject for transmission, means i'or intermittently moving said lm into position to be scanned with the intermittent movement such that certain individual frames of said iilm remain in position for scanning longer than other individual frames of said iilm located between said iirst-mentioned individual frames, means for scanning each of said rst-mentioned individual frames a certain number of times and developing picture signals, and means for scanning each of said other individual frames a smaller number of times and developing picture signals.

19. In a television transmitting system in which a moving-picture film having picture frames is the subject for transmission. means for moving said lm into position intermittently for scanning with the intermittent movement such that alternate picture frames remain in position for scanning longer than the remaining picture frames, means for scanning each of said alternate frames three times in succession and 0 developing picture signals in accordance with said scanning, means for scanning each of the remaining frames two times in succession and developing picture signals in accordance with said scanning.

20. In a television transmitting system in which a moving-picture nlm having picture frames is the subject for transmission. means for moving said film into position intermittently for scanning with the intermittent movement such that alternate picture frames remain in position for scanning for a period which is longer than the period that the remaining picture frames are in position for scanning, scanning means tor so scanning said frames and simulta neously developing picture signals that the scanning lines of each complete frame scanning i'all half way between the scanning lines o! the preceding complete frame scanning, whereby two successive complete scannings produce a full line picture, and meansior so correlating the action of said ilrst means and said scanning means that said alternate frames are scanned three times in succession and the remaining frames are scanned twice in succession, whereby each of two out of five successive full line pictures consists of one complete scanning of one frame and one complete scanning of a next adjacent frame.

ALDA V. BEDFORD.

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