Cathode ray television receiver
United States Patent 2281637

This invention relates to a television receiver, in which a cathode ray tube is utilized. 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 areas...

Sukumlyn, Thomas W.
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Sukumlyn, Thomas W.
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Other Classes:
313/15, 313/36, 313/465, 347/230, 348/E5.14, 359/297
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This invention relates to a television receiver, in which a cathode ray tube is utilized.

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 areas 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 al 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.

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

Instead of a change in reflection properties, the same effect may be obtained by altering the refractive character of the member upon which the beam strikes. For example, the elemental areas may be arranged to become translucent instead of opaque. Under any circumstance, the ability of the surface or member to transmit 11lumination is altered, and the alteration may persist for an appreciable period.

These results can be accomplished, for example, by the heating effects of an electron beam causlnggead. l meltingnaaia e alpaa to assume a transparent character; or by tenpovararcvelatillzitir'aWEiad^rom reflecting surface. It Is thus another object of mytlivefti1o 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 invqntion 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 drawings: Figure 1 is a diagrammatic representation of a system incorporating the invention, the cathode ray tube being shown in section; and Figs. 2, 3, 4, 5, 6, and 7 are fragmentary views similar to Fig. 1, of modified forms 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.

50 In the present instance, the electrical impulses corresponding to the varuitions 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 tube 7. 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 1 make it possible readily to seal therethrough the leading in wires or connectors for the various electrodes. One of these electrodes is a filament 10 heated as by a battery 1 and serving as a source of electrons. Near this electrode 1 is the 1i .control electrode or grid 12. An anode 13 of tubular form serves to direct the cathode ray or electron stream 14 from the heating filament 10 toward the large end of the tube 7.

Since one of the leads 6 from the receiver 2 is 2( connected to the control electrode or grid 12, and since the other lead 5 is connected to the filament 10, the impulses passing to these two electrodes in the form of varying potential differences produce corresponding variations in the intensity of the cathode ray 14 in a well understood manner. The tubular directing anode 13 is arranged to be kept at a positive potential with respect to the filament 1C, as by the aid of the battery 15. 3C The directing anode 13 with its battery 15 serves to accelerate the stream of electrons passing through the anode 13. In order further to accelerate the electrons, the metallic portion 9 of the tube 7 is connected to the positive end of battery 17, 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 7 is closed tightly by a member 18 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 7. For example, this may be accomplished by a member 20 forming a vacuum chamber 22 on the right hand side of the member 18. This member 20 is shown as provided with a flange 21 through which the bolts or screws 19 may pass for clamping the membrane 18 tightly to the end of the tube 7. The chamber 22 formed by the member 20 is utilized in a manner to be hereinafter described in connection with the transmission of illumination to the screen I.

The membrane 18 is arranged to be scanned by the cathode ray beam II. 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 14 in a horizontal direction. Thus the elements 26 can be connected as by leads 27 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 14 in a horizontal direction. The filter 28 can be arranged to pass only high frequency impulses to elements 28, whereby a very rapid to and fro motion of thp beam 14 is secured. In order to deflect the beam 14 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 pPss filter 31. These elements are disposed at right angles to the elements 28, with respect to the axis of tube 7.

The combined results of the elements 28 and 29 are cyclically to cause the beam 14 to trace a series of substantially horizontal lines on the membrane 18, each line being vertically spaced from the preceding one. By proper arrangement of the circuits, this scanning is produced at the desired rapid rate. At the same time, the conO trol electrode 12 of the tube 1 causes a variation in the intensity of the cathode ray 14.

In accordance with well understood arrangements, such a television receiver could comprise a fluorescent screen in place of the membrane 18. 5 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, how0 ever, the membrane 18 is so arranged that elemental areas affected by or receiving the beam 14 are caused to vary the capability of the membrane to transmit illumination, either by reflection or refraction. The variation in the light Stransmission qualities is such that even after the beam 14 leaves an elemental area of membrane 18, 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 IS act only as valves for controlling a rather intense source of illumination; this source is independent of the ray 14; 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 18. Light thus falls over the whole active area of the membrane 18, but due to the action of the stream of electrons carried by ray 14, the light reflecting qualities of that portion of the area which is subjected to the effect of the ray, is altered.

For example, it is known that the impingement of electrons upon a member, such as 18, causes the evolution of heat. This heat could be used for example to affect a layer 35 deposited on the right hand face of member 18 so as to expose the surface of layer 18 adjacent the ray 14, while the heating effect of ray 14 continues.

Layer 38 is formed on membrane 18 before the membrane is placed in the tube assembly. Thus It forms in effect an integral part of membrane 18 and may be termed an integral layer. This right hand surface of member 18 can be specularly reflecting, as for example by the aid of a polished surface. The layer 35 can be a thin film of paraffin, 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 14 on the left hand surface of membrane 18 produces a melting of the wax to expose the specularly reflecting surface of this member II.

Since the wax remains melted for an appreciable period, even after the ray 14 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 14.

The variation In the reflective quality of the membrane It is illustrated in ig. 1. Thus for areas not affected by the heat of ray 14, the reflection of light from source 32 is diffused as indicated by the arrows 3I. However, at the spot S1 where the layer 35 is melted, there is specular reflection of the elemental light beam 38 along the path 31. This elemental light beam is directed through the transparent window 40 of the member 20 and through a converging lens system 41. Thereafter the ray passes through an aperture 42 in the focal plane member 43; thence the ray may pass through another lens system 44 and finally on to the screen I. All of the elemental beams such as 39, which are in succession reflected from membrane 18, are focussed 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 41 to lens 44. The diffused light reflected by the membrane 18 from source 32 through lens 41 is not passed to screen I since it is not focussed by lens 41 on aperture 42, but an elemental beam, or ray, as 39, is focused on the aperture 42 and is thus passed without hindrance. This results in an improved image on the screen, since the cutting off of this diffused light results in a darker screen.

Now as the ray 14 alters its position, the 3 specularly reflecting elemental area on membrane 18 is correspondingly altered. The result is that the direction of the reflected beam, such as 89, also alters. There is thus a corresponding change in the position of ray 45, and there- 3 fore screen I is scanned in accordance with the scanning of the diaphragm 18.

This layer of wax 35 is but one material that could be used for obscuring the surface of member IS. When it is melted by the heat produced 4 by the electron stream of ray 14, it remiains transparent, but resolidifies upon member 18 after a short period of time. In the meanwhile, of course, the melted spot is effective to pass light efficiently to screen I. Thus a brilliant 4, source of light 32 can be properly controlled.

It is not essential that the layer 35 be of wax.

Other materials operate in substantially the same manner. For example in Fig. 2 the membrane 46, corresponding to membrane 18 of Pig. 1, is 5( shown as having a thin volatile metallic layer 47 on its right hand surface. This material when deposited may form a specular reflecting surface. When it is evaporated from a spot such as 94, the corresponding surface of member 48 forms a diffuse reflector. Under any circuimstances, there is a change in the light transmission quality of the surface exposed to the light rays; accordingly, as illustrated, the image produced in this form of the invention is negative. 60 This is true because there is a reduction in 1llumination where ray 14 strikes membrane 46, the diffuse reflecting surface of the membrane serving to disperse the light instead of reflecting it. 05 In order to insure that the vaporized material will recondense upon the membrane 46 and not upon any other part of the tube 1, provisions may be made for heating the other parts of the tube; as for example by an electrical heating coil 49 70 placed upon an extension 50 of the member 48.

In this way the recondensation of the volatilized or vaporized material is confined to the right hand surface of member 46.

In the lens system shown in Fig. 1, each re- 75 flected ray 39 is caused to pass through the focal aperture 42, and thence through the lens system 44 on to the screen I. As the position of ray 14 changes, the position of the reflected ray 39 cor0 respondingly changes, but the lens 41 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 ig. 3, it is not essential that there be two lens systems, such as 33 and 41.

In the form of the invention illustrated in Fig. 3, the membrane 51 is shown as provided with a coating 52 that is either capable of being Smelted or vaporized by the action of the cathode ray 14. In this form only a single window 53 is provided for the end member 54 of tube 7. An intense light from a source 55 is passed through a focal aperture 56 in a screen 100 and thence 0 through a collimating lens system 57. This light illuminates the entire active area of the coating 52. That elemental area adjacent the place where ray 14 strikes the membrane 51 may be rendered specularly reflecting, or diffusely reflecting. The ray 53 reflected from that spot is intended to " pass through the lens 57, which is so arranged as to pass all such reflected rays through another focal aperture 59 in screen 100. Thence the reflected ray is passed through the lens 60 and 0 on to a screen, not shown. In this way the lens system 57 replaces both of the lenses 33 and 41.

As in the first form, aperture 59 is only large enough to pass the elemental ray 58, hence screen 100 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 Fg. 4, the membrane 61 is shown as forming one boundary for a narrow space 62. The other boundary is formed by a thick member 63 capable of transmitting light; for example, a heavy piece of glass. Volatilizable material is placed within the narrow space 62 which is normally condensed upon the corresponding surface of member 63. This member is purposely made with Sa large exposed area to cool the surface upon which the material is to be condensed. The material on the member 63 adjacent the place where ray 14 strikes the membrane 61 is evaporated, and a change in the light transmitting quality of the surface of member 63 is varied.

In this case the volatile material is intended to provide specular reflection except for that area which is subjected to the heat of ray 14; at that point, the light passes through the space 62 and Sis diffused on the surface of membrane 61.

In the forms of the invention thus far described, the light is caused to be reflected from a surface of a membrane. In the form of the invention illustrated in Fig. 5, a refraction arSrangement is illustrated. In this form the tube 64 is shown as having a membrane 65 held in place by a cap or cover 67. Here light from the source 68 passes through the collimating lens system 69 and the transparent window 70 formed in the extension 71 or tube 64. The light 68 thus is caused to illuminate the entire active area of the membrane 65. This membrane 65 may be made of translucent material to refract the light provided the layer 72 on the right hand side of the membrane 65 be temporarily in condition to permit such refraction. This layer 72 may be composed of volatile materials which recondense upon the membrane 65 by virtue of the heating element 73, preventing condensation on other parts of the apparatus. Or else the material may be of such a character that it melts first and then evaporates, later recondensing on the membrane 65.

The refracted ray 74 is shown as passing through a transparent window 75 formed in the member 67, and thence through a condensing lens 76 and focal aperture 77 in a screen 101 through a lens system 78 on to the screen 19.

The scanning of the screen 79 occurs as described in connection with the form of the in- 1( vention shown in Fig. 1, except that the ray illuminating the screen 19 is refracted instead of being reflected. This refraction occurs for a period corresponding to the period of volatilization of the layer 72 from the spot affected by the heat of the ray 14.

In the form of the invention illustrated in Fig. 6, the tube 04 is shown as being provided with an end cover member 60 of heavy glass, such as member 63 in the form of Fig. 4. In this form 'the membrane 81 in conjunction with the adJacent surface of the member 80 forms a confined space 82 for the volatile material. Due to the large cooling surface of the member 80, this volatile material is caused normally to condense 2~ on the adjacent surface of member 80. When the ray 14, however, volatilizes the material at a spot, a corresponding ray 83 is refracted and passed through a lens system 84 to a screen, not shown. o8 The cooling effect to insure that the volatile material will recondense upon the desired surfaces may be of the type shown in Fig. 7. In this form the tube 85 is shown as having an entering extension 86 and an exit extension 87. 3sr The source 88 passes light into the tube 35, which light is intended to be reflected from the surface of member 89, upon the left hand side of which is deposited the volatile layer 0C. In order to insure that the volatilized or vaporized 41) material will recondense upon the member 09, a cooling coil 91 in contact with the member 89 may be utilized. This may be in the form of an air or water circulating coil.

The refracting lenses in this form of the invention may be quite similar to those illustrated in Fig. 1. When ray 14 strikes any elemental area 96, the volatile layer 90 is removed and reflection is prevented because the light is dissipated at the exposed surface. Accordingly in this form a negative image is formed on the screen. If desired a protective transparent membrane or plate 97 for the volatile material 90 may be provided.

The forms of the invention illustrated in Figs. 1, 3 and 4, are made the subject matter of a di.. visional application Serial No. 429,146, filed February 2, 1942, and entitled "Cathode ray television receiver." What is claimed is: 1. 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, a volatilizable coating on said member normally obscuring the reflecting surface, and volatilized by the heat of the ray, means forming a chamber of which said member forms a wall, and in which said coating is volatilized, and means adapted to maintain said member at 0 a temperature below that of the chamber, thereby ensuring that the volatilized matter will recondense on the member.

2. The process of transmitting light in accordance with television signals and by the aid Sof a moving cathode ray, which comprises passing the ray successively over elemental areas of a light transmitting member, illuminating the surface of the member, said surface being arranged to cause dispersion of the illumination, causing the ray where it impinges on the member to vary the transmission of light by the member so that an elemental ray of light is transmitted from the point of impingement, passing the transmitted light through a converging lens system, and then through a focal aperture in a focal screen, said aperture being substantially only large enough to pass said elemental ray, whereby the dispersed light transmitted by the lens system is prevented substantially from passing the screen. 3. In a scanning system operated by transmitted light .and including a source of light emitting substantially parallel rays, a transmitting member upon which said rays impinge, said member causing dispersion of the rays, means for varying in accordance with received television signals, the light transmitting qualities of elemental areas of said member to reduce the dispersion of said areas so that elemental rays are transmitted thereby, a converging lens system adapted to receive the light from the transmitting member, and means forming a focal aperture at the point of convergence, said aperture being capable of passing substantially only said elemental rays.

4: In a cathode ray tube, means forming a chamber having a wall forming a light transmitting member and adapted to be scanned by the cathode ray, said chamber having a vapor pressure neighboring a vacuum, said wall serving to divide the chamber from the tube, material on the wall and within the chamber for varying the light transmitting qualities of said member in response to impingement of said ray on the wall, said ray being modulated in accordance with received television sgnals, and means for controlling the temperature of the chamber independently of the temperature of the tube.