US2454488A - Light modulation by variable transmissivity receiver screen - Google Patents

Description

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LIGHT MODULATION BY VARIABLE TRANSMISSIVITY RECEIVER SCREEN Original Filed April 2, 1938 2 Sheets-Sheet l WOOL/17M EECZ/VEB I l M flan/M) ATTORNEY NOV. 23, 1948. w, SUKUMLYN 2,454,488

LIGHT MODULATION BY VARIABLE TRANSMISSIVITY RECEIVER SCREEN Original Filed April 2, 1938 2 Sheets-Sheet 2 l icT 3 l N VENTOR ho/270s Wfukam gm BY ATTORNEY Patented Nov. 23, 1948 LIGHT MODULATION BY VARIABLE TRANS- MISSIVITY RECEIVER SCREEN Thomas W. Sukumlyn, Los Angeles, Calif.

Original application April 2, 1938, Serial No. 199.667. Divided and this application February 2, 1942, Serial No. 429,146

14 Claims.

This invention relates to a television receiver, in which a cathode ray tube is utilized. This application is a division of an application entitled Cathode ray television receiver, filed in the name of Thomas W. Sukumlyn on April 2, 1938, under Serial No. 199,667, now Patent No. 2,281,637, dated May 5, 1942.

In television reception, the ultimate function of the receiver is to produce an image corresponding to the scene transmitted. invariably, this image is produced on a screen by illuminating elemental area-s thereof in succession at a rapid rate. This process is called scanning. The intensity of illumination is varied in accordance with the requirements of the image to be produced; and the entire screen is scanned often enough that the image produced is seen in its entirety by virtue of the phenomenon of persistence of vision.

All this is well understood. In using a cathode ray tube for television reception, it has been proposed to use a fluorescent screen as one wall of the tube, and to cause fluorescence of elemental areas in succession, by scanning the screen with an elemental beam of electrons.

The fluorescent screen is viewed by the audience. In all such devices, one of the important problems is to produce a sufficiently .brilliant image, in spite of the fact that the illuminating beam passes over the elemental areas rapidly.

It is one of the objects of this invention to prolong the period of illumination on a screen; and particularly by ensuring that elemental areas of the screen are left illuminated for a short period. even after the scanning beam has passed. For example, the scanning beam of electrons in a cathode ray device may be operative to open light valves, which remain open for a period even after the beam passes. In one form of the invention, the electron beam may be caused to alter the character in succession of elemental areas of a light reflector from a diffuse reflector to a specular reflector, and thereby to permit light to pass, through an appropriate lens system, onto a viewing screen. This change in the type of reflection can be such that the area does not immediately revert to diffuse reflection even after the electron stream has passed. Thus, the ability of the surface or member to transmit illumination is altered, and the alteration may persist for an appreciable period.

It is accordingly another object of this invention to make it possible to alter the character of reflection of elemental areas in succession.

These results can be accomplished, for example, by the heating effects of an electron beam causing a readily melting material, such as wax, to assume a transparent character. It is thus another object of my invention to produce appropriate changes in the ability to transmit light, by the aid of the heating effect of an electron stream.

It is a further object of this invention to provide a lens or projection system for use with a scanning system that improves the quality of the image on the viewing screen; this is accomplished by providing means to prevent diffused light in the system reaching the screen.

This invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of several embodiments of the invention. For this purpose there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawing:

Figure 1 is a diagrammatic representation of a system incorporating the invention, the cathode ray tube being shown in section; and

Figs. 2 and 3 are fragmentary views similar to Fig. 1 of a modified form of the invention.

The television system illustrated is arranged to provide two functions that are in general common to many television receivers. A light beam (such as 45) is caused to affect elemental portions of a receptor screen i in succession at a rapid rate to scan the screen completely; often as many as sixteen times per second. The other function is a variation of the intensity of the beam 45 which scans the screen i in accordance with the variations in the light values of the corresponding elemental portion of the scene that is being reproduced.

In the present instance, the electrical impulses corresponding to the variations in this light intensity are translated in a modulation receiver 2, shown as having an elevated collector or antenna 3, and a ground connection 4. Since the circuits and amplifiers included in such a modulation receiver are well known, further explanation thereof is unnecessary.

The output leads 5 and 6 from the receiver 2 may be connected to a device energized in accordance with the impulses received by the receiver 2. This device is illustrated as a cathode ray the preceding one.

tube I. This tube is shown in this instance as having its small end 8 made of glass or the like, appropriately sealed and joined to the metallic diverging portion 9. The glass portion 8 is provided to make it possible readily to seal therethrough the lead-in wires or connectors for the various electrodes. One of these electrodes is a filament I heated as by a battery II and serving as a source of electrons. Near this electrode I0 is the control electrode or grid I2. An anode I3 of tubular form serves to direct the cathode ray or electron stream I4 from the heating filament I 0 toward the large end of the tube I.

Since one of the leads B from the receiver 2 is connected to the control electrode or grid I2, and since the other lead 5 is connected to the filament I0, the impulses passing to these two electrodes in the form of varying potential differences produce corresponding variations in the intensity of the cathode ray I4 in a well understood manner. The tubular directing anode I3 is arranged to be kept at a positive potential with respect to the filament I0, as by the aid of the battery I5.

The directing anode I3 with its battery I5 serves to accelerate the stream of electrons passing through the anode I3. In order further to accelerate the electrons, the metallic portion 9 of the tube I is connected to the positive end of battery II, whereby this metallic portion serves also as an accelerating electrode.

The mode of operation of such tubes being well known, further description is unnecessary.

The large end of the tube I is closed tightly by a member I8 which may be in the form of a thin membrane, either of metal or of non-conducting material. It is held in gas tight relation with the end of the tube I. For example, this may be accomplished by a member 28 forming a chamber 22 on the right hand side of the member I8. This member 20 is shown as provided with a flange 2I through which the bolts or screws I9 may pass for clamping the membrane I8 tightly to the end of the tube I. The chamber 22 which is entirely or almost entirely evacuated, is utilized in a manner to be hereinafter described in connection with the transmission of illumination to the screen I.

The membrane 'IB is arranged to be scanned by the cathode ray beam I4. This can be accomplished, for example, by the aid of the scanning receiver 23, having the elevated collecting conductors or antenna 24 and a ground connection 25. This receiver 23 is caused to affect two sets of influencing devices 26 (either coils or condenser plates), for deflecting the beam I4 in a horizontal direction. Thus the elements 26 can be connected as by leads 21 to the receiver 23 by way of a high band pass filter 28. These elements 26 can-be arranged in such a way as to deflect the beam I4 in a horizontal direction. The filter 28 can be arranged to pass only high frequency impulses to elements 26, whereby a very rapid to and fro motion of the beam I4 is secured.

In order to deflect the beam I4 simultaneously at a slower rate in a vertical direction, elements such as 29 (either coils or condenser plates), are fed low frequency currents through conductors 30 and a low band pass filter 3|. These elements are disposed at right angles to the elements 26, with respect to the axis of tube I.

The combined results of the elements 26 and 29 are to cause the beam I4 to trace cyclically a series of substantially horizontal lines on the membrane I8, each line being vertically spaced from By proper arrangement of the circuits, this scanning is produced at the desired rapid rate. At the same time, the control electrode I2 of the tube I causes a variation in the intensity of the cathode ray I4.

In accordance with well understood arrangements, such a television receiver could comprise a fluorescent screen in place of the membrane I8. In that case the screen is excited by the cathode rays to luminesce the elemental areas in accordance with the intensity of the rays which strike these elemental areas.

In accordance with the present invention, however, the membrane I8 is so arranged that elemental areas affected by or receiving the beam I4 are caused to vary the capability of the membrane to transmit illumination by reflection. The variation in the light transmission qualities is such that even after the beam I4 leaves an elemental area of membrane I8, this variation is nevertheless effective for a short interval. Accordingly, the period of illumination of corresponding elemental portions of the screen I is very greatly increased, with an attendant greatly improved brilliance. In other words, the elemental areas of member I8 act only as valves for controlling a rather intense source of illumination; this source is independent of the ray I4; accordingly greatly increased light energy may be thus utilized to produce the desired image on screen I.

In the present instance, a beam from an intense source of light 32 external of the tube 7 is shown as passing through a collimating lens system 33, and through the transparent window 34 of member 20, to illumine the right hand surface of the membrane I8. Light thus falls over the whole active area of the membrane I8,

but due to the action of the stream of electrons carried by ray I4, the light reflecting qualities of that portion of the area which is subjected to the eflect of the ray, is altered.

For example, it is known that the impingement of electrons upon a member, such as I8, causes the evolution of heat. This heat could be used for example to ailect a layer 35 deposited on the right hand face of member I8 so as to expose the surface of layer [8 adjacent the ray I4, while the heating effect of ray I4 continues. This right hand surface of member I8 can be specularly reflecting, as for example by the aid of a polished surface. The layer 35 can be a thin film of parailin, wax or'the like, that may be readily melted and thereby to form a transparent layer when melted, in place of a substantially'opaque layer when solidified. Accordingly, the heat generated by the striking of the ray I4 on the left hand surface of membrane I8 produces a melting of the wax to expose the specularly reflecting surface of this member I8. Since the wax remains melted for an appreciable period, even after the ray I4 sweeps away from it, it is seen that the specular reflection persists for a much longer period than the period. of impingement of the ray I4.

The variation in the reflective qualit of the membrane I8 is illustrated in Fig. 1. areas not affected by the heat of ray I4, the reflection of light from source 32 is diffused as in dicated by the arrows 36. However, at the spot 3'! where the layer 35 is melted, there is specular reflection of the elemental light beam 38 along the path 39. This elemental light beam is directed through the transparent window 40 of the member 20 and through a converging lens system 4|. Thereafter, the ray passes through an aperture 42 in the focal plane member 43;

Thus for thence the ray may pass through another lens system 44 and finally on to the screen I All of the elemental beams such as 3-9, which are in succession reflected from membrane l8, are focused at aperture 42.

The aperture 42 in member 43 is located at the focal point of the lens system and is of such size as to pass only an elemental ray from lens 4| t lens 44. The diffused light reflected by the membrane l8 from source 32 through lens 4| is not passed to screen I since it is not focused by lens 4! on aperture 42, but an elemental beam,

change in the position of ray 45, and therefore screen I is scanned in accordance with the scanning of the diaphragm l8.

This layer of wax 35 is but one material that could be used for obscuring the surface of member l8. When it is melted by the heat produced by the electron stream of ray l4, it remains transparent. but resolidifies upon member l8 after a short period of time. In the meanwhile, of course, the melted spot is effective to pass light efilciently to screen I. Thus a brilliant source of light 32 can be properly controlled.

In the lens system shown in Fig. 1, each refiected ray 39 is caused to pass through the focal aperture 42, and thence through the lens system 44 on to the screen I. ray 14 changes, the position of the reflected ray 39 correspondin ly changes, but the lens 4! passes the reflected ray always through the aperture 42. The angular relationship. however, is varied so that the effect is a scanning of the screen I and a building up of the image. However, as illustrated in Fig. 2, it isnot essential I that there be two lens systems, such as 33 and 4!.

In the form of the invention illustrated in Fig. 2, the membrane is shown as provided witha coating 52 that is capable of being melted by the action of thecathode ray [4. In this form only a single window 53 is provided for the end member 54 of tube 1, and forming an evacuated chamber IDI. An intense light from a source 55 is passed through a focal aperture 56 in a screen I 00 and thence through a collimating lens system 51. This light illuminates the entire active area of the coating 52. That elemental area adjacent the place where ray l4 strikes the membrane 5! may be rendered s ecularly reflecting, or diffusely reflecting. The ray 5B reflected from that spot is intended to pass through the lens 51. which is so arranged as to pass all such reflected rays through another focal aperture 59 in screen I00. Thence the reflected ray is passed through the lens 60 and on to a screen, not shown. In this way the lens system 51 replaces both of the lenses 33 and 4 I. As in the first form, aperture 59 is only large enough to pass the elemental ray 58, hence screen I00 prevents the diffused light from lens 51 being passed to the screen and improves the quality of the image projected there.

In the form of the invention illustrated in Fig. 3, the membrane BI is shown as forming one boundary for a narrow space 62. The other As the position of.

boundary is formed by a thick member 63 capable of transmitting light; for example, a heavy piece of glass. Wax is placed within the narrow space 62 and upon the corresponding surface of member '63. This member is purposely made with a large exposed area to cool the surface upon which the wax is placed. The wax on the member 63 adjacent the place where ray l4 strikes the membrane BI is melted, and a change in the light transmitting quality of the surface of member ,63 occurs. In this case the wax is intended to provide specular reflection except for that area which is subjected to the heat of ray M; at that point, the light passes through the space 62 and is dif-- fused on the surface of membrane 6|.

In order to prevent the wax from running down on the surface of membrane 63, the axis of any of the tubes '1 shown may be placed vertically, so that the support for the wax coating is substantially horizontal.

What is claimed is:

1. In combination, a wax coated member, a source of illumination for the wax coating, said member having a surface beneath the coating capable of operating as a specular reflector and normally obscured by said coating, and means for successively heatingelemental areas of said coating to render said areas transparent.

2. In combination. a wax coated transparent member, a source of illumination for the member, said coating normally obscuring the member from said source, and means for successively heating elemental areas of said coating to render said areas transparent.

3. In combination, a cathode ray tube, a member having a specular reflecting surface, and in the path of the ray, means for scanning said member by the ray, a source of illumination for said surface, and areadily meltable coating on said member normally obscuring the reflecting surface, except where it is melted by the ray.

4. In combination, a cathode ray tube, a member having a reflecting surface, and in the path of the ray, 2. volatilizable coating for said mem ber to obscure the surface thereof and affected by the heat of the ray, means for scanning said member by the ray, means for modulating said ray, and means for illuminating the member.

5. In a cathode ray tube device, means forming a chamber separate from the cathode ray chamber and having a wall which the cathode ray is adapted to scan, and a wax coating on said wall in said separate chamber and adapted to be affected by the heat of the ray for altering the light transmitting qualities of the wall.

6. In a cathode ray tube device, a member capable of transmitting received light, adapted to be scanned by the cathode ray, and an opaque coating on said member adapted to be affected by the ray to successively render elemental areas of said coating transparent while the coating is on the member.

7. In a cathode ray tube device, a light transmitting member adapted to be scanned by the cathode ray, and a meltable opaque coating on said member, said coating becoming transparent when melted, said coating being adapted to be affected by the heat of the ray to successively alter the light transmitting qualities of elemental areas of the coating, said member being disposed horizontally to prevent flow of the coating when melted.

8. In a cathode ray tube device, said device having a generally vertical axis, a member having a specular reflecting surface adapted to be scanned by the ray, and a readily meltable coating on. said member normally obscuring the refleeting surface, except where it is melted by the ray.

9. A television picture reproducing device comprising a source of light, means for projecting an image of said source, control means including an element having a variable light dispersing characteristic adapted to be altered in accordance with heat applied thereto, disposed in the projection path of said. light to permit its passage therethrough, means disposed adjacent said control means for reflecting said projected light through said element, and means for heating successive points of said last-named means in accordance with a television picture signal thereby to vary said light dispersingcharacteristic.

10. A television picture reproducing device comprising a source of light, means for projecting an image of said source, control means including an element having a variable light dispersing characteristic adapted to be altered by application of heat thereto, disposed in the projection path of said light to permit its passage therethrough, means disposed adjacent said control means for reflecting said projected light through said element, said last-named means adapted to be heated by electron bombardment, and means for bombarding said last-named means point by point with a beam of electrons modulated in accordance with a television picture signal.

11. The method of reproducing a television picture which comprises projecting an image of a source of light through an element having a variable light dispersing characteristic, reflecting said projected light through said element, and heating said element thereby to alter the light dispersing characteristic thereof in accordance with a television picture signal.

12. The method of reproducing a television picture which comprises projecting an image of a source of light through an element having a variable light dispersing characteristic, reflecting said projected light through said element, and heating said element thereby to alter the light dispersing characteristic thereof in accordance with a television picture signal, and projecting only the dispersed light passing through a predetermined path to reproduce said television picture.

13. A television picture reproducing device comprising a source of light, means for projecting an image of said light source, control means including a light dispersing element disposed in the projection path of said light to permit its passage therethrough, said element being of such character that its light dispersing properties may vary from maximum dispersion to zero dispersion, means disposed adjacent said control means for reflecting said projected light through said element and means for altering the light dispersing characteristic of said element in accordance with a television picture signal.

14. A television picture reproducing device comprising a source of light, means for projecting an image of said light source, control means including a light dispersing element disposed in the projection path of said light to permit its passage therethrough, said element being of such character that its light dispersing properties may vary from maximum dispersion to zero dispersion, and means for altering the light dispersing characteristic of said element in accordance with a television picture signal.

- THOMAS W. SUKUMLYN.

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

UNITED STATES PATENTS Number Name Date 2,020,025 Gardner Nov. 5, 1935 2,121,990 Schroter et al. June 28, 1938 2,155,465 Behne et al. Apr. 25, 1939 2,156,392 Iarns May 2, 1939 2,185,379 Myers et a1 Jan. 2, 1940 2,185,439 Hinderer Jan. 2, 1940 2,281,280 'Gabor Apr. 28, 1942 2,281,637 Sukumlyn May 5, 1942 2,315,113 Farnsworth Mar. 30, 1943 FOREIGN PATENTS Number Country Date 190,201 Great Britain Dec. 18, 1922 367,300 Great Britain Feb. 18, 1932

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