US2200749A - Television picture reproducing apparatus - Google Patents

Description

M y 1940- R. J. KEMP TELEVISION PICTURE REPRODUCING APPARATUS Filed Sept. 8., 1936 0 Wm WM m wmgm -WKT m R w Patented May 14, 1940 TELEVISION PICTURE REPRODUCING APPARATUS Roland John Kemp, Chelmsford, England, assignor to Radio Corporation of America, a corporation of Delaware Application September 8, 1936, Serial No. 99,807 V In Great Britain September 7, 1935 5 Claims. (01. 178-75) (Granted underthe provisions of sec. 14, act of March 2, 1927; 357 0. G. 5)

This invention relates to television and like picture reproducing apparatus and has for its object to provide improved reproducing apparatus adapted to reproduce pictures of relatively large size capable of being viewed by a fairly large audience.

It has been proposed to reproduce relatively large television and like pictures by means of a reproducing screen comprising a series or chequer of lamps each representative of an elemental area of the picture and to employ a suitable commutator or similar switching means to connect each of the lamps in succession to the output end of a television receiver apparatus so that the intensity of illumination of each lamp is controlled in succession by the incoming television signals. Arrangements cf this kind have obvious disadvantages the chief practical difficulty arising by reason of the extremely elaborate commutation means required if a sufficiently large number of picture elements be employed to give a reproduced picture of reasonably fine detail.

The present invention provides an improved form of reproducer of the kind wherein the picture elements are constituted by individual light sources but, in carrying out this invention, recourse to mechanical commutating or similar switching means is entirely obviated.

According to this invention a received television picture is first reproduced on a normal scale as in the usual way and an image of this reproduced picture is optically projected upon an auxiliary screen constituted by a bank of light sensitive relay devices each corresponding to an elemental picture point or area and each permanently connected to one of a bank of separate light sources arranged in the form of a final reproducing screen. In view of the fact that each light sensitive relay device is permanently connected with its associated light source, commutation difficulties are avoided.

The invention is illustrated in the accompanying drawing which shows, purely schematically a preferred way of carrying out the invention.

Referring to the drawing the received television or like picture signals are translated into pictures on a normal scale by means of a cathode ray reproducing tube of any suitable known form and operated in any suitable known way. This tube is represented in Figure l at A the television receiver proper being not shown. The image l (represented as a diamond in Figure l) reproduced upon the fluorescent screen 2 is projected optically by means of a suitable lens system B upon an auxiliary screen C consisting of a bank of photo-electric cell elements 3 (only a few of these elements are shown) there being provided one element 3 corresponding to every picture point to be reproduced. Each photo-electric cell element 3 is connected to control one light source 4 on a second auxiliary screen D made up of a corresponding number of such light sources. Only a few light sources Q are shown and the connections between the cell elements 3 and the light elements 4 are represented in Figure 1 by single broken lines. Diamonds I and l" corresponding to the original image I are shown on the screens C and D respectively in Figure l.

The form of light sources which it is proposed to employ at 4 in carrying out this invention is represented in Figure 2 and consists of a simplified form of cathode-ray tube of small size having a fluorescent screen 5 upon which is directed a beam 6 of electrons whose intensity is controlled by the associated photo-electric cell output. Each of these cathode ray tubes however, is not provided with means for focusing the beam to a sharp point upon the fluorescent screen 5 but comprises simply a cathode i, an apertured anode 8, and a controlling electrode 9 which may be, as shown, in the form of a Wehnelt cylinder, the cathode ray or beam being arranged to fall on substantially the whole area of the fluorescent screen 5 which is made quite small. As shown each tube 4 is controlled by the corresponding cell 3 which is in series with a suitable bias source It between the cathode l and the control electrode 9.

With the above arrangement it is possible to control the brightness of each screen 5 between a maximum and zero by variation of a very small amount of light incident upon the associated photo-electric cell 3. This means that the image projected upon the bank of photo-electric cells 3 constituting the auxiliary screen C may be very considerably enlarged, thus permitting a large number of photo-electric cell elements to be employed.

The photo-electric cells 3 constituting the auxiliary screen C may take the form of individual vacuum tube elements or in a simpler form of copper oxide cells.

When a cathode ray tube A is employed as the primary reproducing means as in the arrangement illustrated it will be seen that not only are commutation difiiculties completely overcome but the further advantage is obtained that each individual light source is controlled during a period of time equal to the period of after glow of the fluorescent screen 2 of the primary rewhat manner the same is to be performed, 1 declare that what I claim is:

1. An image reproducing system comprising a plurality of light sensitive devices lying in a common plane, a cathode ray tube having a fluorescent screen, optical means for projecting a light image produced pcint-by-point sequentially and formed on the fluorescent screen upon the plurality of said light sensitivedevices to energize the same in a predetermined sequence, aplurality of cathode ray tubes each having a luminescent screen lying in a common plane, and control channels from each of said plurality of light sensitive devices to each of the plurality of cathode ray tubes to actuate the luminescent screens in said predetermined sequence in accordance with the light impinging on the plurality of said light sensitive devices whereby an enlarged image corresponding to that on the fluorescent screen is produced.

2. A reproducing system comprising a plurality of cathode ray tubes each having a luminescent screen lying in a common plane and arranged in a predetermined pattern, an equal number of light sensitive devices lying in a common plane and arranged in a pattern similar to the arrangement of said plurality of cathode ray tubes, means to produce a light image point-by-point according to a predetermined sequence, means to project the produced light image upon said light sensitive devices to energize the same in said predetermined sequence, and means to actuate the luminescent screens of said cathode ray tubes by the light sensitive devices in accordance with light from the light image impinging upon said light sensitive devices whereby an enlarged replica of the light image is produced.

3. A reproducing system comprising a plurality of cathode ray tubes each having control means contained therein and a luminescent screen, said screens lying in a common plane and arranged in a predetermined pattern, each of said screens having a predetermined area, an equal number of photo-electric cells lying in a common plane and arranged in a pattern similar to the predetermined pattern of the cathode ray tubes, each of said photo-electric: cells having a photo-sensitive area of a size smaller than the predetermined area of the luminescent screen, means to connect each of the photo-electric cells. to the control means of a similarlypositioned cathode ray tube, cathode ray means to produce a light image point-,by-point sequentially, and means to project the produced light image upon the photo-electric cells to energize the same in a predetermined "sequence" whereby there is produced an enlarged replica of the produced light image by the plurality of cathode ray tubes;

4. In an electro-optical image producing system, a plurality of electron tubes for producing light, an electronically produced source of light,

means W for moving the electronically produced source of light over an area related in dimensions to thepositioning of the plurality of electron tubes to energize said tubes sequentially according to a predetermined pattern, and light responsive connecting links intermediate the electronically produced source of light and each of the plurality of tubes for controlling the several tubes of the plurality from the electronically produced light.

5.An electro-optical producing system, comprising means for electronically producing an image point by point according to a predetermined sequence, a plurality of cathode ray tubes arranged in a predetermined pattern, each of said tubes having means to control the electronic production of light within the tube, andlight responsive connecting links intermediate the electronically image producing means and each of the control means of the plurality of cathode ray tubes for controlling the production of light with in said tubes from the electronically produced light sequentially according to the predetermined sequence.

ROLAND JOHN KEMP.

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