US2022450A - Television system - Google Patents

Television system Download PDF

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US2022450A
US2022450A US57648531A US2022450A US 2022450 A US2022450 A US 2022450A US 57648531 A US57648531 A US 57648531A US 2022450 A US2022450 A US 2022450A
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cathode
current
means
screen
circuit
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Vladimir K Zworykin
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Westinghouse Electric Co LLC
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Westinghouse Electric Co LLC
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Priority to US683337A priority Critical patent/US2141059A/en
Application filed by Westinghouse Electric Co LLC filed Critical Westinghouse Electric Co LLC
Priority to US57648531 priority patent/US2022450A/en
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00Cathode ray tubes; Electron beam tubes
    • H01J31/08Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/26Image pick-up tubes having an input of visible light and electric output
    • H01J31/28Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen
    • H01J31/30Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen having regulation of screen potential at anode potential, e.g. iconoscope

Description

v. K. zwoRYklN v2,022,450

TELEVISION SYSTEM Nov. l 26, 1935..

original Filed Deo. 29, 192s s s hee'ts-sheet 1 a hllh Q 3 I lulllllllllllfw a un F-IPHP ATTORNEY BMM Nov. 26, 1935. Y v. K. zwoRYKl'N A2,022,450

TELEVISION SYSTEM original Filed Dec. 29, 1923 s sheets-sheet 2 l l I@ l El. w l l Q. $3 l a f l E G Y* *Ew-ummm n m ',gji i l. T 3%,

wlTNEssi-:s: A lNv-ENoR l Vlad'm z'r l. Zworg/rm.

. BY M Y l l i l ATToRN Y Nov. 26, 1935. v. K. zwoRYKlN 2,022,450

TELEVISION SYSTEM SShets-Sheet 5 Original Filed Dec. 29, 1923 INVENTOR Vladimir if. Z wary/772.

@g/ggf; i BY Uw 'ATTORNEY WITNESSES:

Patented Nov..

UNITED sTATEsr PATENT ori-*TCE 'y signor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporasystems, and

tion of Pennsylvania original application December 29, 1923, sei-lai No;

Divided and this application November 21, 1931, Serial No. 576,485

'5 Claims. (Cl. 118-6) My invention relates, in general, to television comprises a division of the invention embodied in an application on television systems, Serial No. 683,337, filed by me on De- 8 cember 29, 1923 and relates particularly to the modification disclosed in Figure 3 of the abovenoted application.

One of the objects vide a system for enabling a person or views by radio. Another object of my invention is to eliminate synchronizing devices heretofore employed in telemoving objects vision systems.

Still another object of vide a system for broadcasting, from a central of my invention is to proto see distant my invention is to propoint, moving pictures, scenes from plays, or similar entertainments.

The above and other objects of my invention will be explained more fully hereinafter with reference to the accompanying drawings forming a part of this specification.

pictures or other visual considered the televi station for to the drawings, Figure 1 is a broadcasting motion indications, and may be sion transmitter.

Fig. 2 is a diagram of a receiving station for receiving the scenes broadcasted -from the transmitting station.

Fig. 3 is a fragmentary view arrangement for the of an alternative transmitting station.

Fig. 4 shows an arrangement whereby the control of the transmitting and the receiving stations may be exercised from a central station;

and

Fig. 5 shows station when a Both of these stati conventional circuit the circuitsof the transmitting central station is used.

are shown by means of apparatus diagrams in ons and sufcient detail to enable the invention to be readily explained and understood.

Any, visual indications may be broadcasted by the transmitting set I consisting of apparatus and circuits and be received by the receiving set 2 consisting of apparatus and circuits.

The apparatus of prises an antenna sys the transmitting set I comtem 3 which Is so tuned that a transformer i to the er triode 5. The grid of the amplifier 5 is connected through a transformer 6 to the plate Acir-- cuits of modulator triodes 'l and 8. An oscillator triode 9 is connected through a" transformer I0 to the grid circuit of the modulator triodes 1 and plate circuit of an ampli- The grid circuit of the amplier I4 is connected, 10-

by means of a transformer I5, to the plate circuits of modulator triodes I6 and I1. AAn oscillatortriode I8 is connected, by means of a transformer I9, to the grid circuits of the modulator means of transformers l? H triodes I6 and vI1. By 20 and 2I, alternating-current generators 22 and 23 are also connected to the grid circuits of the modulator triodes I6 and I1.

The generator 22 is so constructed as to generate high-frequency alternating current of a. 20 frequency of about 1000 cycles, while the alternating-current generator 23 is adaptd to generate an alternating current of av ir'giuency at about 16 cycles.

It is, of course, obvious in oscillating circuits may be used in place of the alternating-current generators 22 and 23.

The plates 25 and 26 in a cathode-ray tube 21 are connected in the circuit through a series transformer 24. Coils 20 andv29 are associated with the vcathode-ray tube 21 in such position that the magnetic eld which may be produced Joy said coils is parallel to the electrostatic eld which may be generated by the plates 25 and 26, and these coils areconnected in circuit with the 35 alternating-current generator 23. v 'Y `The cathode-ray' tube 21 is similar in some respects to the ordinary cathode-ray oscillograph and has a hot cathode 29', a diaphragm 30 and tubular anode 3|. .The diaphragm 30 has a small hole so'cut therein as to form the cathode ray into a thin beam.

In place/'of the ordinary uorescent screen is substituted a composite plate 32 having layers of 45 different material. p

A lens 31 or system of lenses is secured in place by means of a frame 38 disposed at the end of the cathode-ray tube. The lens 31 is'arranged -to focus the image or scene to be observed upon 50 the photoelectrlc material of the composite plate 32. A grid 39 is placed at some distance infront of the composite plate 32 and is connected to the grid of the ampliiier triode I2. A high potential is applied to the anode 3I by a rectier 40 which 55 that triodes connected 25 is supplied with current from current source 4|.

In the receiving device 2, 50, including an antenna 5|, is adapted to be resonant to current of two distinct frequencies, these frequencies being the frequencies generated by the oscillating circuits that include the triodes 9 and I8 of the transmitting set. An amplifier triode 53 is connected to the oscillating circuit. 50. 'I'he plate circuit of the amplifier triode 53 is connected to a grid 54 in a cathode-ray tube 55.

'I'he cathode-ray tube 55 is constructed in a manner similar to the ordinary cathode-ray oscillograph and comprises a hot cathode 56, the grid 54, a tubular anode 51, plates 58 and 59 that are used to set up an electrostatic field and a fluorescent screen 60. 'I'he anode 51 of the cathoderay tube 55 is supplied with high voltage by the operation of-a rectifier 6 l, that rectifles the alternating current supplied by a source of alternating current 62.

The oscillating circuit 50 is also connected by means of a transformer 63 with a circuit 64. The circuit 64 is, in turn, lconnected by means of transformers 65 and 66 with the grid circuit of the amplifier triodes 61 and 68. The plate circuit of the amplifier triode 61 is connected with the plates 58 and 59 of the cathode-ray tube 55, while the circuit of the amplifier triode 68 is connected to the coils 69 and 10 that are associated with the cathode-ray tube 55 and so disposed with respect thereto that the magnetic ields generated by the coils are parallel to the electrostatic field generated by the plates 58 and 59.

The transformer an alternatingan oscillating circuit the transmitting station so as to eliminate this frequency from the circuit 64. In a like manner, the transformer 66 acts as a-wave trap for the particular frequency generated by the generator 23 by the transmitting station.

'I'he alternative arrangement of the apparatus in the transmitting station, shown in Fig. 3, is adapted to transmit pictures. 'I'his system differs from the one shown in Fig. 1 in thatan ordinary cathode-ray oscillograph is'employed. One end only of the oscillograph has been shown. This oscillograph has the usual iiuorescent screen 15. There is a photoelectric cell 16 situated close to the oscillograph. A lens 11 is disposed between the photoelectric cell and the cathode-ray tube arranged to focus the light from the uorescent screen on the cell. A diapositive or ordinary photographic negative 18, that has the image on it that it is desired to transmit, is placed between the lens and the cathode-ray tube. 'Ihe circuit connections of this arrangement are similar to those shown in Fig. 1.

'I'he apparatus shown in Fig. 4 is practically identical with the apparatus shown at the right in Fig. 1, with the exception that there is provided a separate antenna |03 and includes means whereby the synchronizing frequencies generated by the'generators |22 and |23 may be radiated from a central station.

Fig. 5 is very similar to Fig. 1, with the exception that the coils |09 and I I0 for creating the electromagnetic field for controlling the cathode beam and the plates III and II2 for creating the electrostatic eld are controlled by detector triodes |01 and I 08 which are connected to the receiving antenna through the oscillatory circuit I I.

Having brieiiy described the apparatus shown in the drawings, I will now explain its detailed operation. For this purpose, it will `be assumed that it is desired to broadcast the image of some object which is in front of the lens 31- associated with the transmitting cathode-ray tube 21.

Ordinarily, the oscillations generated by the oscillator 9 are not radiated by the antenna 3. This is because of the fact that these oscillations are neutralized by the action of the modulator triodes 1 and 8, and, consequently, there is no transfer of energy into the secondary of transformer 6. The only manner in which the antenna can be set in oscillation by the operation of the triode 9 is by a change in condition in the primary of the transformer II which is connected to the grid 39 and to the aluminum foil 34 of the composite plate 32.

The light from the image placed before the lens 31 is so varied that, upon the focusing of this light upon the photoelectric globules 36 of the composite plate 32, electron emission of varying intensity by these particles takes place in accordance with the light from the object placed before the lens 31. This electron emission may be considered a species of conduction between the photoelectric globules 36 and the grid 39. This phenomena is intensified by the argon vapor that fills the container 33 as a result of the ionization of the vapor.

In view of the fact that the aluminum oxide plate 35 is an insulator, there is no connection existing between the grid 39 and the aluminum plate 34, even though the photoelectric globules emit electrons. When the cathode beam strikes a particular point upon the aluminum fou, 1f; is 35 of suiiicient intensity to penetrate it, as well as the aluminum oxide. The action of the cathode ray on the aluminum oxide in its path, particularly in the presence of the gas, is to produce a conductive connection between the aluminum 40 plate 34 and the particular globule or globules of potassium hydride in the path of the cathode ray. 'I'he electrons emitted by these globules are therefore subjected to the eld produced by the battery 42 acting across the conductive part of 45 the aluminum oxide. The amount of the emission will depend upon the degree of illumination of these globules. The current iiowing in the circuit is dependent upon the electron emission from the globule or globules covered by the cathode beam. This current is amplified by means of the amplifier triode I2. 'Ihe current from .the grid 39 to the grid of the tube I2 is so small that no grid leak is necessary for the tube I2 although one may be supplied if desired. The output of the amplifier I2 now causes the modulator triodes 1 and 8 to transmit, through the transformer 6, the high-frequency oscillations, generated by the oscillator triode 9, modulated in accordance with the current m the amplifier mode l2 which, m 60 turn, is governed by the intensity of the light focused upon the particular spot at which the cathode ray is located. The intensity of this electron stream is. of course, governed by the intensity .of the light from the object. 8

As previously mentioned, the alternatingecurrent generators 22 and 23 are producing alternating current of a high and low frequency, respectively. By the operation of the modulator triodes I6 and I1. the oscillations produced bv the oscillator triode I8 are modulated in accordance with both the frequency of the alternatingcurrent generated by the generator 22 and the alternating current generated by the generator 23. This modulated high frequency current is 75 lli Nio.

amplified by the amplifier triode I4 and radiated by the antenna 3.

As the output of the alternating-current generator 22 is also connected to the plates 25 and 26 in the cathode-ray tube 21, an electrostatic field is set up by these plates which varies in accordance with the frequency'of the currentl generated by the generator 22. As this electrostatic field varies, the electrostatic action upon the electrode beam causes it to be swung from one edge of the composite plate 32 to the other.

A portion of the alternating current generated by the generator 23 also traverses the coilsA 28 and 28 which, as before mentioned, are so positioned with respect to the cathode tube 21 that the magnetic eld generated by these coils is parallel to the electrostatic field generated by plates 25 and 25. The varying magnetic iield set up by these coils tends to cause the cathoderay beam to traverse the plate 35 in a direction at right angles to that before described.

The resultant action between the magnetic fields and the electrostatic fields upon the cathode beam is such that the beam covers every point in the whole area of the composite plate 32 in nl; of a second, that is, in 1/2 cycle of the frequency generated by the alternating-current generator 23. Thus, in 11g of a second, the cathode beam traverses the surface of the composite plate twice.

As the cathode beam traverses the surface of the composite plate 32 point by point in a definite sequence, there is a current flowing from the grid 39 and the aluminum foil 35 at each particular point, and this current is directly proportional to the intensity of light from the object to be observed. Thus, the oscillatory current generated by the oscillator triode 9 is modulated in accordance with the light from each portion of the image. i

At the receiving station, the modulated oscillatory currents generated by the oscillator 5 of the transmitter are received by the antenna 5i and transferred to the detector triode 53 through the transformer 52. The detector triode 53 then operates to detect the modulations and then these are transferred through its plate circuit to the grid 5d of the cathode-ray tube 55.

By means of the transformer t3, associated with the oscillatig circuit 50,- the modulated radio-frequency current generated yby oscillator i8 is received and transferred by transformers 55 and 66 in the detector triodes 61 and 58. By the operation of the transformer 65, only the radio frequency that is modulated by the generator 22 is detected. In a like manner, by the operation of the transformer 66," only the radio frequency modulated by the generator 23 is received by the detector triode 58. A

As the plate circuit of the 4detector triode 61 is connected to the plates 58 and 59 the cathode-ray oscillograph 55, an electrostatic field is set up by these plates which varies in identically the same manner as theV electrostatic field generated by the plates 25 and-26m the transmitting cathode-ray tube. Likewise, thplate circuit of the triode 68 is connected to the coils-69 and 10 which generate a. magnetic iield parallel to'the electrostatic field generated by the plates 58 and 59 and that varies in exactly the same manner as the magnetic field set up by the coils 28 and 29 at the transmittingstation. Thus, when the cathode-ray beam passes through the grid 54 and the anode 51 to the iiuorescent screen-Gbit is caused to traverse a path in accordance with the resultant magnetic and electrostatic fields 'appear thereupon as a moving image.

s'et up.' Therefore, the cathode-ray beam traverses the whole area of the fluorescent screen once in nl, of a second, or twice in 11; of a second, in the same manner as the cathode beam in the cathode-ray tube 21 at the transmitting station. 5 Whenthe cathode beam in the cathode-ray tube ot the transmitter is in a certain particular position, the oscillatory current generated by the oscillator 9 is modulated in accordance with the intensity ofthe light falling upon that parl0 'ticular point. This modulated current is radiated by the antenna 3 and received by the antenna 5I at the receiving station. at this particular point, the cathode beam in the cathode-ray tube 55 will be in the same relative position as the l5 cathode beam at the sending station. By the action of the grid 54, the intensity of the cathode ray reaching the fluorescent screen at this particular point is varied in accordance with lthe light from the image at the transmitting station. 50 Thus, for every particular point on the image, the carrier current radiated by the antenna 3 is modulated whereby the potential on the grid 54 of the receiving cathode-ray tube 55 is varied, as is, also, the intensity of fluorescence of the 2l particular point upon the fluorescent screen 50. As the whole area of the composite plate 32 at the transmitting station and the fiuorescent screen 60 at the receiving station is covered by the cathode beams in El, of a second, the image 30 of the object will be displayed on the screen t0 during nl; of a second. However,'.as the frequency. of the oscillation of the generator 23 is it cycles per second, the picture will be transmitted twice and will remain on the screen 60 during of a 35 second. Thus, due to the persistency of vision A phenomena, any movement of the object before the lens 31 will be properly transmitted and recorded' upon the uorescent screen 5D and will d0 Of course, in place of transmitting the image of actual objects, it is entirely possible to send moving pictures, as all that is necessary is to pass the pictures before the lens 3l at the required rate and a replica of them will appear on the 45 screen 60. 'In order to place these pictures before a large audience, it is, of course, possible to intensify and focus them upon an ordinary screen by means of any well known optical system.

The operation of the system when the appara- 50 tus used in Fig. 3 is employed at the transmitting station is very similar to that already described. The cathode beam covers the area of .the fluorescent screen 15 under the influence of the malgnetic and electrostatic fields. When the'beam is 55 atJ one particular point, the light from that spot will traverse the film 13, lens 11 and photoelectric cell 16.

The variation of current of the photoelectric cell 16 causes the carrier frequency to be modulated in accordance with the current ilow which lis directly proportional to the intensity of light from the fluorescent spot that reaches the photoelectric cell. As this condition occurs for each o5 particular point on the picture, the whole picture will be transmitted in the manner described. The method of reproduction is the same as has been explained in conjunction with Figs. 1 and 2.

Inasmuch as a particular portion of the image is transmitted by means of a modulated alternating current, the potential upon the grid 54 of the receiving cathode-ray tube 55 will be varied to some extent in accordance with the carrier frequency. The grid 54 will thus influence the 75 cathode beam. 'I'he cathode beam falling at a particular point on the fluorescent screen will vary in intensity, thus producing a phenomenon somewhat similar to that occasioned were the cathode beam to be fully cut off. This impulsing action of the cathode beams in the cathode-ray tubes at both the transmitting and receiving stations ls intensified, by reason of the fact that the potential applied between the cathode and the anode in each case is uctuating, being supplied from a direct current derived from a rectified alternating current. By reason of these actions, the tendency of the fluorescent spot on the screen 60 to spread is minimized. The intensity of the cathode beam may be regulated by regulating the voltage of the alternating-current sources 4| or 62 in a well known manner.

Attention is drawn to the fact that any change in the frequency of operation of the alternatingcurrent generators 22 and 23 at the transmitting station causes a corresponding change in the frequency of oscillations in the current eiecting the cathode ray at the receiving station, and, consequently, the cathode-ray beams will remain in synchronism at both the transmitting and receiving stations and there will be no distortion in the picture transmitted.

It is obvious that it is entirely possible to have the alternators 22 and 23 generate a synchronizing frequency at a station separate from the transmitting station. In this case, the central synchronizing station would be arranged in the manner shown in Fig. 4. The alternators |22 and |23 correspond to the alternators 22 and 23. These alternators serve to modulate a frequency generated by the oscillating circuit including the oscillator triode ||8, and this modulated frequency is radiated from the antenna |03 in the usual manner.

At the transmitting station in Fig. 5, the operation is the same as has been before described, with the exception that the'oscillatory circuit |0| is resonant to the synchronizing carrier frequency, and this frequency is transferred to the trans- .formers |05 and |06 of the detector triodes |01 and |08. By the operation of these detectors, the synchronizing frequencies are applied to the coils |09 and ||0 and to the plates and ||2. 'I'he further operation of the system takes place in the same manner as has been described before.

It will be seen that this arrangement permits a number of transmitting stations to transmit pictures or visual indications with only one central station for generating the synchronizing frequency.

It is, of course, apparent, that any number of receiving stations may receive the image broadcasted in a manner similar to that described.

My invention is not limited to the particular arrangement of apparatus illustrated but may be variously modified without departing from the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention: 1. Scanning means for television systems or the like comprising a screen, a scanning medium v directed against said screen, means for moving the scanning medium so as to subject each ele- 5 mental area of the screen to the scanning medium to cause a source of light tobe developed at each elementalI area of contact of said scanning medium and said screen, means employing a reection of said source of light to scan an element 10 of a subject to be scanned, and means for translating the various light values on each elemental area of the scanned subject .into electric current impulses.

2. Scanning means for television systems or l5 the like comprising a screen, a scanning medium, means for causing said scanning medium to traverse said screen in a predetermined manner, means for causing a point source of light to develop at successive elemental areas of contact 4 of said scanning medium and said screen, means for causing said pointsources of light to scan coordinated elemental areas of a s'ubject to be scanned, and means to convert the varying light values determined by each elemental area illuminated into proportionately varied electric current impulses.

3. Scanning means for television systems or the like comprising a cathode ray, a screen adapted to fluoresce under the action of a cathode ray, means for causing said ray to traverse predetermined paths on said screen to produce a series ofv successive point sources of light, a subject to be scanned, means for causing the successive point sources of light to scan correspondl ing successive elemental areas of said subject, and light translating means for converting the light values represented by each elemental area illuminated into proportionately varied electric current impulses.

4. Scanning means for television systems or the like comprising means for continuously developing a series of sequentially produced sources of light according to pre-established patterns over successive elemental sections of a predetermined area, a subject to be scanned and means for causing the successive point sources of light to scan corresponding successive elementary areas of said subject.

5. Means for producing an electric current modulated to adapt it for image reproduction comprising a fluorescent screen, means for producing an electron stream focusing upon said uorescent screen, means for causing.4 said electron stream to traverse said fluorescent screen point by point, a light-responsive electrical circuit element positif-.ined to intercept a portion only of the radiant eirgy generated at the focus of said electron streamwon, said screen, and means for interposing the image to be reproduced between said uorescent screen and said lightresponsive electrical circuit element.

\ VLADIMIR K. ZWORYKIN.

US57648531 1923-12-29 1931-11-21 Television system Expired - Lifetime US2022450A (en)

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US57648531 US2022450A (en) 1923-12-29 1931-11-21 Television system

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