US2479820A - Color television system - Google Patents

Description

Aug. 23, 1949.

H. B. DE VORE 2,479,820

COLOR TELEVISION SYSTEM Filed May 1, 1947 /5 AMPLIFIER T OUTPUT SIGNAL I TO TRANSMITTII 22 INPUT SIGNAL FROM REgEuvc-R IN V EN TOR.

Henfy B. De I bre A T TORNE Y RECEIVER Patented Aug. 23, I

UNITED STATES PATENT OFFICE COLOR TELEVISION SYSTEM Henry B. De Vere, Norwalk, Conn., assignor to Remington Rand Inc., New York, N. Y., a corporation oi Delaware Application May 1, 1947, Serial No. 745,311

1 T This invention relates broadly to color television systems. The principal object of the inventionable noise interference is eliminated.

Another object of the invention is to eliminate color trailing or fringing for moving objects and to materially reduce flicker by providing a high rate of color sequence.

Another object of the invention is to obviate the need for a plurality of electronic picture pickup tubes and/or reproducing tubes which must be exactly synchronized in operation to obtain proper color register.

Another object of the invention is to provide a new and novel system and apparatus for color separation and recombination by optical means.

Another object is to provide a color television system in which correction for the color characterist cs of pick-up tube and reproducing tube may easily be made.

Still further objects and advantages will, of course, become apparent and at once suggest themselves to those skilled in the art to which the invention is directed when the following specification and claims are read in connection with the accompanying drawing, wherein:

Fig. 1 illustrates an embodiment of the present invention as applied to a television pick-up tube for translating a color picture into corresponding electrical impulses.

Fig. 2 illustrates a highly magnified view of the lens, composite filter, and light sensitive element, the paths of the representative light. rays being indicated by dotted lines, and,

Fig. 3 illustrates one form of a television image reproducing system according to the present invention. V

As above stated, the primary purpose of this invention is to provide a system which may be applied to certain types of television pick-up and reproducingtubes, whereby a television picture in color may be transmitted. The improved system, hereinafter fully described in detail. employs a composite color filter, which is preferably placed close to or adjacent the lens used for imaging the'picture, and an array of cylindrical lens elements placed close to the sensitive surface of the pick-up tube. By this method and means, each element of the picture to be transmitted is 2 Claims. (Cl. 178-52) 2 broken up or divided into separate images, corresponding to the primary colors of which the composite sections of the color filter are made. The intensity of the illumination in these separate images Isdetermined by the brightness and color of the corresponding picturev element.

Means corresponding to those described above in connection withthe pick-up tube are used in conjunction with the picture reproducing tube.

Referring to the drawing, and for the present to Fig. 1 reference numeral i0 schematically indicates a television pick-up tube, which in this case is of the typefemploying low velocity-electron beam scanning and which is provided with an electron gun II and. a novel form of light sensitive element It, the latter being presently described in'detail. An electron beam l3, generated by the gun I l is caused to scan the photosensitive mosaic surface IQ of the light sensitive. element 1 2 by deflection means here shown in the form of conventional deflection coils ii. The signal generated by the scanning process is taken from signal plate 2! and introduced into an amplifier I 4, the output 22 of which is used as the picture signal to be transmitted.

A suitable lens i6 is used to image the scene to be transmitted'on the light sensitive element l2 and a composite color filter I! is disposed in a position closely adjacent to said lens It. The

color filter shown in the present embodiment comprises three sections, but it will be understood that a greater 'or'lesser numberof sections may be used if and when desired. The sections of color filter l1 will be hereinafter referred to as HR, (3, and "B which, for example; may

be considered the primary colors red, green, and blue respectively. The color filter I! should have substantially the same 'dimension as the lens It, in a direction perpendicular to the optical path, in order that all of the light passing through the lens should also pass through the color filter, and vice versa. If acompound lens is used, the filter should be placed as close to the center of the lens system as practicable.

Attention is now directed to Fig. 2 wherein the light sensitive element I2 is shown on a highly magnified scale. As illustrated this element comprises a transparent support i8, which in the present case is composed of two members designated I8a and Nb. On the outer surface mesh 2|, which serves as a signal plate to transmit the electrical signal to amplifier M in the usual manner well known to those skilled in the are of television. The signal plate 2| is here indicated as being placed between members [8a. and l8b of the transparent support. It is understood that the position is not limited to this, but the element 2| may, for example, be a conductive coating on the surface of the cylindrical .lens elements 20 or. may be a transparent con-' ductive film or screen placed close to the array of cylindrical lens elements 20. The cylindrical lenticular elements 20 are designed and arranged in such a manner as to focus colored images on the photosensitive mosaic surface IS. The width.

of the individual lens elements should be substantially the same as the width of the images formed by these lenses, in order that these images do not either overlap or leave gaps between successive images. These images are represented by Mr, Hg, and Hb in Fig. 2 and correspond to the sections HR, "6-, and. [1B respectively of the color filter H. The intensity of illumination of each of these three images is determined by the brightness and color of the corresponding element of the scene to be transmitted.

In the operation of this system, the image formed on the photomosaic surface I9 of pick-up tube It! may be scanned, for example, in a direction such that the horizontal scanning lines are parallel to the cylindrical lens elements 20 and so adjusted that each scanning line exactly coincides with the position of one of the images formed through the color filter sections Hr, Hg, and [1b. Thus, in the course of scanning one line, the beam will produce a signal corresponding to the blue content of a single line of the television picture. The next scanning line will give a signal corresponding to the green content of the same line of elements of the original picture and the next scanning line will give a signal containing information as to the blue content of the same line of the original picture. This process is repeated for each line of the picture. Alternatively, the scanning could be carried out at right angles to this direction such that the horizontal scanning lines are perpendicular to the cylindrical lens elements. In this case, the scanning line will contain information successively as to the red, green, and blue content of each element of the picture.

Referring now to Fig. 3, wherein the television reproducing system is schematically shown, reference numeral 24 indicates a cathode ray tube having an electron gun 25 to form an electron beam 26. This beam is scanned across a phosphorescent screen structure 21 by any suitable deflection means, for example, conventional deflection coils indicated at 28, and at the same time, the beam is modulated by control electrode 34 in accordance with the received television signal. The image formed on the phosphorescent screen is projected onto a viewing screen 29 by means of lens 30 and closely adjacent composite color filter 3|.

The phosphorescent screen structure 21 is coated on the side facing the electron beam 26 with a suitable phosphor, indicated at 32, which will be excited by said electron beam 26 in a manner to give off substantially white light. The opposite side of screen 21 is provided with an array of cylindrical lenticular elements 33,'designed to focus the phosphorescent surface through the lens and color filter assemblyjU-S l and has the same number of cylindrical lenses as the pick-up tube structure light sensitive element 1!. It will be understood that the direction of scanning, rate of scanning, and position of the scanning lines relative to the cylindrical lensarray 33 of the phosphorescent screen structure 21 of the reproducing tube must be identical with the direction, rate of scanning, and line position, relative to the light sensitive element l2 of the pick-up tube.

It may be pointed out here that, optically, the operation of the picture reproducing system (shown in Fig. 3) is similar to that of the pickup system shown in Fig. 2 with the exception that the direction of the light paths is reversed, as indicated by the arrows. The bright spot formed at position llr by beam 26 will transmit light only through section HR, of the color filter 3| and will produce a red image. Similarly, light produced by excitation of element I'lg can only pass through the green section HG of color filter 3| and will produce a green image, and light originated at position llb can only pass through the blue section [1B of color filter 3| and will produce a blue image. Since the brightness of these three elements must correspond to the illumination of the corresponding points of the pick-up tube surface, the reproduced picture element will have substantially the same color as the corresponding element of the scene viewed by the pick-up tube.

Non-uniform sensitivity of the pick-up tube mosaic surface [9 to the diiTerent primary colors of light may easily be compensated by appropriate choice of color density in the corresponding sections of color filter l1, and similarly, departure from pure white in the luminescent spot formed on the reproducing tube phosphor 32 by the scanning beam 26 may be compensated by appropriate choice of color densities in the elements of the composite color filter 3|.

While the color system above described has included a pick-up tube of the type employing a transparent signal plate and a photosensitive mosaic surface, the system is applicable to use with any form of television pick-up tube in which light is admitted to one side of a photosensitive element while the corresponding electrical signal is formed on the opposite side thereof. For example, in the type of pick-up tube which employs a semi-transparent photocathode to give an electron image which is subsequently focused and scanned, as for example, in the case of the Image Orthicon, the photosensitive element may be similar to that shown as [2 in 'Figs. 1 and 2, except that no signal plate element is required and the photosensitive mosaic surface I9 is replaced by a continuous photoemitting surface.

While I have shown and described a particular embodiment of my invention it will be apparent to those skilled in the art that numerous modifica tions and variations may be made in the form and construction thereof, without departing from the more fundamental principles of the invention. I' therefore desire, by the following claims, to include within the scope of my invention all such similar and modified forms of the apparatus disclosed, by which substantially the results of the invention may be obtained by substantially the same or equivalent means.

Having thus described my invention what I claim as new and desire to secure by Letters Patcut is:

1. A color television system for transmitting three-color pictures comprising; a camera pickup device which includes a photoelectric element auaaao for converting an optical image into an electron image, means for scanning the electron image by a cathode ray beam for producing signals which may be transmitted to a receiving station, a lens system for focussing an image on the photoelectric element, a color filter arranged in three sections for dividing the focussed light rays into three colored beams, and a lenticular array of cylindrical elements for separating said colored beams at the focal plane of the image; reproducing means for showing the transmitted signal in the form of a three-color picture at the receiving station which includes a cathode ray scanning beam, modulated by said transmitted si nal, for scanning a target of fluorescent material, a lenticular array of cylindrical elements for transmitting light beams from the fluorescent screen to a lens system, a color filter arranged in three sections for coloring the transmitted light and a projection system for showing the received picture on a screen after being focussed by the lens system.

2. A color television system for transmitting three-color pictures comprising; a camera pickup device which includes a photoelectric element for converting an optical image into an electron image, means for line scanning the electron image by a cathode ray beam for producing signals which may be transmitted to a receiving station, a lens system for focussing an image on the photoelectric element, a color filter arranged in ed parallel to the scanning lines for transmitting.

light beams from the fluorescent screen to a lens system, a color filter arranged in three sections for coloring the transmitted light and a projection system for showingthe received picture on a screen after being focussed by the lenssystem.

HENRY B. DE VORE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,296,908 Crosby Sept. 29, 1942 2,310,863 Leverenz Feb. 9, 1943 FOREIGN PATENTS Number Country Date 489,355 Great Britain Oct. 30, 1935

Images