US2103312A

US2103312A - Cathode ray device

Info

Publication number: US2103312A
Application number: US687298A
Authority: US
Inventors: Maggio C Banca
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1933-08-29
Filing date: 1933-08-29
Publication date: 1937-12-28
Anticipated expiration: 1954-12-28

Description

Dec. 28, 1937, M. c. BANCA 2,103,312

CATHODE' RAY DEVICE Filed Aug. 29} 1953 INVENTOE j qa g lloflliwwm Patented bee. 28, 1937 OATHODE RAY DEVICE Mugio C. Banca, Magnolia, N. J., assignor to RadidCor-poration of America, New York, N. Y.,

.a corporation of Delaware Application August 29, 1938, Serial No. 687,298

9 Claims. My invention relates to improvements in television systems.

In television systems embodying a cathode ray tube at the transmitting station, and in which the tube comprises a photo-sensitive mosaic screen on which an image of the object is projected, and which is has been found to be advantageous to project the image on the same side of the screen which is scanned by the ray. When this is done, the axis of the optical system for projecting the image is usually made perpendicular to the screen, but the axis of the so-called gun for developing and directing the ray of electrons is, for convenience, disposed at an angle to the screen. On account of this arrangement, the outline of the area scanned by the ray has a keystone shape rather than the desired rectangular shape. This distortion of the scanned pattern is manifested by a substantial and corresponding distortion ofthe reproduced image at the receiving station, the

reproduced image being'also the shape of a keystone, with the vertical lines inclined down- I wardly toward each other.

With the foregoing in mind, it is one of the objects of my invention to provide an improved television systemof the character referred to wherein the keystone distortion is corrected.

Other objects and advantages will hereinafter appear.

In accordance with my ray at the transmitting station is deflected in such manner as to tend to spread out the scanned pattern in a keystone effect opposite to the keystone pattern which would otherwise be scanned, the effect being to substantially entirely com-. ,pensate or correct for the latter, so that the scanned pattern is rectangular in shape.

. More particularly, in accordance with my invention, complementary plates are usedto deflect the cathode ray at the higher frequency, sometimes referred to as the line frequency. These plates are tilted with respect to each other in such manner and amount to cause the amplitude of deflection to vary uniformly during each scanning period. In this way, each line is made slightly shorter by thesame amount from each end thereof than the preceding line, to cause the ray to scan a keystone area in a plane perpendicular to the tube axis, the sides of thisarea being Y inclined upwardly toward each other. when the ray strikes the inclined screen, therefore, and is deflected in the two directions at right angles invention, the cathode to each other, it is caused to scan the screen over a rectangular area.

scanned by a cathode ray, it

(c1. est-21.5)

My invention resides in the improved apparatus of the character hereinafter described and. claimed, For the purpose of illustrating my invention, an embodiment thereof is shown in the drawing, wherein Y Figure 1 is a perspective view, partly diagrammatic, ofatransmitting tube constructed and operating in accordance .with my invention;

Fig. 2 is a simplified, front elevational view, taken from Fig. '1;

Fig.3 is a plan view of Fig. 2; y

Fig. 4 is a sectional view, the section being taken on the line 4-4 in Fig. 2; and

Fig. 5 is a diagrammatic view illustrative of the principle of operation.

face l4 comprised of a great number of minute metallic elements, such as silver globules, each insulated from the electrode [2 and from each other, and each provided with a coating of photosensitive material. In operation, an image of the object, shown as being in the form of a moving picture film tivesurface by a suitable optical system H, the axis 18 of the optical system being perpendicular to the screen surface It. M r

A gun 20 of any suitable construction operates to develop and the photosensitive surface I, the axis 22 of the gun being disposed at an acute angle, for example to the photosensitive surface I4.

For the purpose of causing the ray to scan the photosensitivesurface of the screen 12, a

saw-tooth voltage wave at a frequency of 24 cycles, for example, is applied across complementary plates 26, and a saw-tooth voltage wave at a frequency of 4320 cycles, for example, is applied across complementary plates. 28. The ray, therefore, isdeflected vertically 24 times a second .by the plates 26, and is simultaneously deflected horizontally 4320 times a second by the plates 28. The

plates

26 and 28 are disposed within the tube, as represented, and may be carried by supporting elements (not shown) extending from the struc-' ture of the gun 20. r

\ Inoperation, the projection of the image on the photosensitive surface it causes discrete electrostatic charges .to'be-stored up over the surface, each elemental charge being proportionate to the light intenslty at the elementalarea. As the ray 24 scans the surface l4, these charges are neutralized to develop picture signals which are In Fig. 1, a transmitting tube I0 is provided with an electrode i2 having a photosensitive sur-v IB, is projected upon the photosensidirect a my 24 of electrons at.

supplied to a radio or tem (not shown).

Ordinarily, the ray 24 would scan the surface l4 over an area ABCD, as shown in Fig. 5. That is, the scanning pattern would be the shape of a keystone rather than the desired rectangle. This would cause, at the receiving station, the production of a distorted image on the fluorescent screen of the usual cathode ray tube, the vertical lines of the reproducedimage being so inclined to each other that the entire image would have a generally keystone configuration.

For the purpose of compensating or correcting for the keystone distortion referred to, I propose to position the plates 28 in the following manner. These plates are on opposite sides of the axis 22' of the tube, and diverge upwardly from each other, as more clearly shown in Fig. 4, the lower edges 28a being, therefore, substantially closer together than the upperedges 28b, the edges 28a being on the same side of the tube axis 22 as the lower edge |2a of the screen which is nearer to the gun 20.

For the purpose of providing clearance for full horizontal deflection of the ray between the two extreme positions W and X, the plates 28 are also made to diverge outwardly from each other in the direction looking toward the screen l2, as more clearly shown in Fig. 3. The edges 280, which are nearer to the gun 20 are, therefore, closer together than the edges 28d.

Likewise, for the purpose of providing clearance for full vertical deflection of the ray between the two extreme positions Y and Z, the plates 26 are made to diverge outwardly from each other in the direction looking toward the screen l2, as more clearly shown in Fig. 2. The edges 260 of the plates, which are nearer to the gun 20, are therefore closer together than the edges 26d.

In operation of the tube, asthe ray isdeflected horizontally and simultaneously deflected vertically downward the amplitude of any horizontal deflection is slightly greater than the amplitude of the preceding horizontal deflection. The ray 24, therefore, is caused to scan a keystone area such perpendicular to the axis 22 and which is about the same distance from the gun 20 as the screen l2. The result is that the ray scans the screen I2 over the desired rectangular area such as is represented in Fig. 5 by the area JKLM.

The action just described is attributed to the fact that, for the same conditions of voltage, the amplitude of deflection of a cathode ray by plates is inversely proportional to the average distance between the plates where the ray is. at the instant. It will, therefore, be apparent that when the ray is between the upper edge portions of the plates 28 the amplitude of horizontal deflection will be a minimum, and when the ray is between the lower edge portions of the plates the amplitude of horizontal deflection will be a maximum.

In the drawing, the center of the screen I2 is considered to be substantially eight inches from the tip of the gun 20, and to be inclined 60 to the axis 22. With regard to the respective angles of inclination of the plates 28 and 28', these are determined according to the various dimensions and requirements of any particular tube. In the particular tube shown,-satisfactory results have been obtained with the respective angles about as shown and designated.

' Fora receiving tube, the embodiment of my invention would be the same as in the transmitting tube disclosed, but the front-surface ofthe screen other transmitting sysas EFGH in Fig. 5, in a plane l2 would be coated with fluorescent material, and

the optical system I! would be one which would project onto a relatively large, external screen, the image reproduced on the fluorescent screen.

From the foregoing it will be seen that I have provided improved cathode ray apparatus wherein the screen is inclined substantially to the axis of the tube, and wherein the ray is caused to scan the screen over a substantially rectangular area by the action of at least one pair of plates which deflect the ray at the higher line-frequency. In this connection, it will be understood that electromagnetic coils can be used instead of the plates 26 for deflectingthe ray at the lower or framefrequency.

While but one embodiment of my invention has been described, it will be understood that various modifications are possible without departing from the spirit of my invention or the scope of the claims.

I claim as my invention:

1. A cathode ray device comprising, screen structure, means for scanning said structure comprising means for developing a scanning ray and directing the same at said structure, the axis of said ray-developing means being inclined at an acute angle to said structure, and means for deflecting said ray simultaneously in different directions at relatively high and relatively lowfrequencies respectively to cause the ray to scan said structure over a substantially rectangular area, said deflecting means including complementary non-parallel plates disposed on opposite sides of said axis for deflecting the ray at the relatively high frequency.

2. A cathode ray device comprising a tube provided with a substantially flat screen and with means for developing a scanning ray and directing the same at said screen, the axis of said ray- .develo'ping means being inclined at an acute angle to said screen whereby the part of the latter on one side of said axis is closer to said raydeveloping means than the other part of said screen, and means for deflecting said ray simultaneously in different directions at relatively high and relatively low frequencies respectively to cause the ray to scan said screen over a substantially rectangular area, said deflecting means including complementary non-parallel elements disposed on opposite sides of said axis for deflecting the ray at the relatively high frequency and inclined to each other in the direction to cause said elements to convergetoward each other on said one side of said axis.-

3. A cathode ray device comprising atube provided with a substantially flat screen and with means for developing a scanning my and directing the same at sa developing means. being inclined at an acute angle to said screen whereby the part of the screen, the axis of said raylatter on one side of said axis is closer to said raydeveloping means than the other part of said screen, and means for deflecting said ray simuldirections at relatively high taneously in different and relatively low cause the ray to scan tially rectangular area, said deflecting means including complementary plates for deflecting the ray at the relatively high frequency and disposed within the tube on'opposite sides of said axis, said plates being disposed in non-parallel planes frequencies respectively to and inclined to each other in directions to cause said screen over a substan-' said plates to converge toward each other on said one side of-said axis.

4. A cathode ray device comprising a'tube pro aioasia F v 1 'vided with a substantially flat screen and with means 101- developing a scanning ray and directingthe same at said developingmeans being inclined to said screen at an acute angle of the order of sixty degrees whereby the axis is closer to said ray-developing means than the other part-oi said screen, and means for deflecting said ray simultaneously in diflerent directions at relativelfhigh andrelatively low frequencies respectively to cause the ray to scan said screen over a substantially rectangular area, said deflecting means including a pair of plates for deflecting the ray atthe relatively highdrequency and disposed within the tube on opposite sides of said axis-said plates being disposed in non-parallel planes directions to' cause said plates to converge toward each other on said one side of said axisan'd to verge from each other in the direction toward said screen.

5. A cathode ray device comprising a tube provided with a substantially flat screen and with means tor-developing a scanning ray and directing the same at said screen; the axis of said ray-developing means being inclined to said screen at an acute angle or the order of sixty degrees whereby the part oi said screen on one side of said axis is closer to said ray-developing means than the other part c! said screen, means for deflecting said ray simultaneously in dinerent directions at relatively high and relatively low frequencies respectively to cause the ray to scan v said screen over a substantially rectangular area,

said-deflecting means including a pair of plates for deflecting the ray at the relativellh l irequency and disposed within the tube on opposite sides of said axis, said plates being disposed in non-parallel planes and.incli ned to each other in directions to cause said plates to converge toward each otheron said one side of said axis and to diverge from each other in the direction to'- ward said screen. and a second pair otplates 1 dis osed between said ray-developing means and .said first pair of plates for deflecting the ray at the relatively low ireduency. the plates of said second pair being disposed within said-tube on opposite sidesoi said .axisand in non-parallel planes and inclined to each other in directions to cause said plates to diverge from each the direction toward screen.

. 6. A cathode ,ray de ce I comprising screen i structure',meansiorscanningsaidstructurecomprising means for developing a scanning ray and 5; directingthesam eatsaidstructuratheaxi'sor screen. the axis of said raypart of said screen on oneside of said and inclined to each other in' r in l intersecting planes, the line oi intersection of the said ray-developing'means being inclined atwan acute angle to said structure, and means ior de-' flecting' said ray simultaneously in diflerent directions at relatively high and relatively low freduencies respectively to cause the ray to scan said structure over a substantially rectangular ,said deflecting means including complementary plates disposed in intersecting planes and on opposite sides of said axis for deflecting the ray at the relatively high frequency.

'1. A cathode ray device comprising screen structure, means for scanning said structure comprising means for developing a scanning ray and directing the same at said structure, the axis of said ray developing means being" inclined at an acute angle to said structure, and pairss'oi,

plates for deflecting said ray simultaneously in dliierent directions at relatively ,high and .reladisposed in intersecting planes 8. A cathode ray device comprising screen structure, means for scanning said structure comprising means for developing a scanning ray and directing the same at said structure, the axis of said ray-developing meansbeing inclined at an acute angle to said structure, and means for deflecting said ray-simultaneously in diflerent directions at relativelyv high and relatively low frequencies respectively to cause the ray to scan said structure over a substantially rectangular area, said deflecting means including complementary' plates disposed on opposite sides oi said axis for deflecting the ray at the relatively high frequency, said plates being disposed in intersecting planes wherein the line oi'intersection thereof intersects a line parallel to the tube axisat an angle lessthan ninety degrees. r 9. A cathode ray device comprising screenstructure,. means for scanning said structure.

comprising means for developing a scanning ray and directing the same at said structure, the axis ot ,said ray-developingmeans being inclined at'an for deflecting said ray simultaneously in different directions at relatively high and relatively low finite angle to said structure,- and pairs of plates 1 frequencies respectively to cause the my to scan said area, the platesot each pair being disposed in planes in which one pair of plates lies intersecting a line parallel to-the tube axis at an angle less than ninety degrees. f v v MAGGIO C. BANCA.

Etna-tine over a substantially rectangular