US2293899A - Television system - Google Patents

Description

Aug. 25,` E942.

O. B. HANSON TELEVIS ION SYSTEM Filed Aug.

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Patented Aug. 25, 1942 wir 2,293,899 'rELEvrsxoN SYSTEM Oscar B. Hanson, Westport, Conn., assigner to Radio Corporation of America, a corporation of Delaware Application August 23, 1940, Serial No. 353,796

Ii Claims. (Cl. Tis- 6.8)

This invention relates to television transmission systems and more particularly to means for translating television images of one degree of resolution to an image of another degree of resolution.

When it is desired to transmit television signals wherein images having dierent degrees of resolution are provided over different transmission channels ln order to insure service for television receivers designed to receive the transmission of images of the selected degrees of resolution, or, in some instances, to record photographically the image in one degree of resolution and then to broadcast or rebroadcast the image at another degree of resolution,.it is impractical to have a battery of cameras for developing the signals to be utilized, for each system from a single production. A number of objections to the use oi a plurality oicameras are at once evident. Among these are the necessity of providing equipment for the correction of parallax due to viewing the scene or object from diierent angles. Still further, a plurality of cameras in a studio ci limited space is bulky and crowds the studio so as to make impossible satisfactory mobility and thus the desirable shift of camera location for diierent scenes of action.

Throughout this specification, reference is made to images having one degree of resolution and those having a second degree of resolution. Any one degree of resolution may herein be understood as relating to a scanning operation having any assumed degree of resolution by reason of a certain number of lines per frame, elds per frame, and repetition rate of frames per second.

It frequently becomes desirable to record a televised program made up of images having one predetermined degree of resolution as, for example, for syndication, and then to convert the program to images having a second degree of resolution for radio transmission.

It is sometimes desirable to change the range of the broadcast transmitter by lowering the frequency. This necessarily requires a narrower representing the same image at a greater number of lines per frame.

One of the objects of this invention is to provide means for converting television images having one degree of resolution to images of another degree of resolution.

Another object of this invention is to provide means for transmitting separate trains of image signals from a single television camera, each train of image signals being adapted to form an image having a diiferent degree of resolution.

Another object of this invention is to provide means for recording photographically the tele` vised program at a degree of resolution diierent from the degree of resolution used for radio v transmission,

band width because of limited space in the lower Y and broadcast or rebroadcast a train of signals Another object is to provide an electronic means for changing between television images of diierent selected degrees of detail.

Still another object is to provide an electrooptical means for changing between diierent television images having different degrees of resolution.

Other and incidental objects of the invention will be apparent to those skilled in the art from a reading of the following speciiication and an inspection of the accompanying drawing in which Figure 1 shows, in block diagram, an electrooptical system for converting television images from one degree of resolution to another;

Figure 2 shows, in .block diagram, means for transmitting a plurality of trains of image signals, each train having a different degree of resolution, from a single television camera;

Figure 3 shows means for recording photographically images having one degree of resolution and converting the same train of image signals to a train of image signal having another degree of resolution for radio broadcasting; and fFigures 4, 5 and 6 show diierent forms o1' double mosaic cathode structures. y

Referring to Fig. 1, the television camera and associated apparatus i supplies the ampliiier and transmitter 2 with a trainA of image signals having a first predetermined degree of resolution, Such a system is described in an varticle by R. R. Beal in RCA Review of January, 1937. The television camera and associated apparatus I also supplies the same train of image signals to picture tube 3 which forms an optical image on surface t. The lens system shown at 5 is used to focus this image on a second television camera inconoscope 6, whose cathode 'I furnishes a second amplifier and transmitter 8 with a train of image signals representing the original picture image in a second degree of resolution.

The proposed electro-optical method of trans` ci' a device of this general type are herein de` scribed.

Fig. 2 shows one embodiment of my invention in which a single television camera is used to provide trains of image signals representing images having different degrees of resolution. A modified form of scanning tube is shown at 9 in which the mosaic electrode element il is scanned by electron beams i and i2 applied to the same side of the mosaic element Il. An image from the subject i1 is focused on the mosaic element it through lens system I8. The mosaic element may be of any suitable form such as that described in Essig Patent 2,065,570, issued December 29, 1936, and assigned to Radio Corporation of America. The mosaic element i i comprises an insulating supporting base member to which are applied, or which carries, individual, minute, photosensitive, electrically conductive elements insulated from each other.

Electron beam I0 is modulated by the voltage of modulator 21 at a high frequency, for example, mc., and, likewise, electron beam i2 is modulated by the voltage of modulator 26 at a frequency different from that of modulator 21, for example, l0 mc. These modulators may take the form of any of the well known ultra high frequency oscillators. The electrical representations or signal resulting from scanning the optical image focused on the mosaic element II are then transmitted through band pass filters i9 and 24, each of which is designed to select a band of frequencies covered by each of the modulators 26 and 21 and their associated side bands so that the train of image signals caused to flow from the mosaic element I I, by the modulated electron beam I0, are passed by band pass filter S9 to its amplifier and transmitter 20. Likewise, the train of image signals, or signal resulting from scanning the image upon the mosaic electrode Il by the modulated electron beam I2 is passed by band pass filter 24 to the amplifier and transmitter 25. The horizontal synchronizing pulse generator 22 suppliespulses at two predetermined rates which are coordinated with the selected degrees of resolutions. One series of pulses is supplied to the horizontal deflection coils I4 associated with scanning tube 9. This same series oi' pulses also furnishes amplifier and transmitter 20. The other series of pulses are supplied to the horizontal deflection coils I6 yof the scanning device. 'I'his same series of pulses also furnishes amplier and transmitter 25.

In one form of this invention a vertical synchronizing pulse generator 23 is arranged to develop a single form of synchronizing pulses at a selected rate of repetition. These pulses are then transmitted directly to amplifier and transmitter 25 and the vertical deflecting coils I 5, which are associated with the scanning tube 9. Amplifier and transmitter 25 combines the horizontal synchronizing pulses, the vertical synchronizing pulses and the picture signals, and transmits them to the associated television channel. The same character of pulses is also supplied to a delay circuit or delay network 2| (which may be of any known form) so as to be delayed in phase by or other selected phase angle. The delayed pulses are then transmitted to amplifier and transmitter 20 and are utilized to energize the vertical deiiecting coils I3 of the scanning tube 8. Thus, the vertical deflection of the electron beam I0 across the mosaic element I I follows the electron beam I2 by 180 or one-half a picture frame, or by any other degree selected. This delay is essentially to provide adequate time for the optical image which is cast upon the photosensitive mosaic II to cause the development of an electrical representation (e. g., an electrostatic change) upon the mosaic so that when that element is scanned by each of the electron beams I0 and I2, there will result an output signal energy train which characterizes the optical image in two forms of resolution or standards. This delay also prevents interfering eiiects between scanning lines. Amplifier and transmitter 20 combines this second series of horizontal synchronizing pulses, vertical synchronizing pulses and picture signals, and transmits them to a second television channel.

An alternative method of generating carriers would be by the use of a line grating in front o! the mosaic. The different scanning rates for the two beams would give different carrier frequencies with the same grating.

Fig. 3 shows an arrangement in which the electrical representation of an image received from the television camera and its associated apparatus is utilized to furnish a train of image signals, a portion of the energy of which is fed directly to a transmitter. Another portion of energy from the same train of image signals is reconstructed as an optical image on surface 32 of picture tube 3l and focused by optical system 33 to a photographic iilm 35 of a photographic camera 34. Another portion of the energy of the same train of image signals is also utilized to form an optical image on the image cathode 38 of a tube 36. This tube 36 includes a double sided mosaic indicated at 38 and shown-in more detail in Fig. 4. Tube 36 is of a double ended construction in which a highly evacuated envelope contains oppositely disposed electron guns, each of which may be of conventional construction, including the usual cathode, control electrode, first anode and second anode. One side of the envelope contains an auxiliary collecting ring 40 maintained at a positive potential with respect to its associated cathode and designed to collect secondary electrons emitted from the mosaic 38 by reason of the electronic bombardment of electron gun beam 39. It is preferably designed so that it will not be struck by electron beam 39 and so that none of the secondary electrons caused by the beam 31 on the opposite side of the mosaic are collected. The amount of secondary electrons present will depend upon the electrical image on the mosaic 38. Therefore, a train of picture signals may be taken oif from the collector 40 and amplified in amplifier 4I. A second collector 40a is positioned adjacent the electrode 38 on the same side as electron gun 31. The rates upon which the deflection of the electron beam 31 is based is the same as those rates of deflection used for the television camera and associated apparatus 30. A second predetermined rate or rates of deflection is chosen to control the electron beam 39 so that the amplifier and transmitter 4I will produce a train of image signais whose optical image has a degree of resoluaaaasee tion diierent from that produced by television camera and associated apparatus 30.

A discharge device such as that shown at 9 in Fig. 2, that is a converter tube having two electron guns on the same side of a single sided -mcsaic, may be used in the system shown in Fig. 3.

Fig. 4 shows one ty-pe of image cathode suitable for the tube 36 of Fig. 3. This cathode mosaic is of the type in which the elements 43 are contained in the interstices of mesh t2 and are exposed on' both sides of the mesh so that they will come in contact with both the electron beams operating from opposite sides of the cathode. For example, it may be constructed in accordance with the teachings of Patent No.

2,045,984, issued February 28,1934, in the name,

of Leslie E. Flory, and assigned to the Radio Corporation of America.

Fig. 5 shows another image cathode suitable for the tube 36 of Fig. 3. A very thin transparent material 45 supports a fluorescent screen 44 ori its one side and on its other side a mosaic of minut-e photosensitive electrically-conductive elements insulated from each other. Light produced -by fluorescent screen 44 under bombard- Fig. 6 shows still another form of double sided image cathode in which a supporting element of mica or other insulating material 4l supports small metallic particles 48 on one side and particles 49 on the other side. The particles 48 on one side of the supporting member 41 will be given an electrical charge in accordance with potential of an electron beam which is in turn controlled by a train of signal energy. The particles on the opposite side will receive .a corresponding charge by the capacitive effect of the supporting member 41 to be scanned off by a second electron beam to produce a second train of signa-l energy having a second degree of resolution and repetition rate.

In either of the proposed methods of conversion of an image from one degree of resolution to another, it would be desirable to employ the same vertical scanning frequency for the two parts of the system, but a rather large difference in phase between the two would be desirable to eliminate beats between the two rates of line scanning.

In one embodiment of this invention, the line scanning rates used in the two systems bear an integral relation to one another (such as 441 and 882 lines), and adjustment of vertical scanning in the two parts of the translating device for the most efficient translation of vertical detail is provided. t

In another embodiment of this invention, the converting devices are used in pairs in a sort of push-pull arrangement; under certain conditions, this makes possible translation between two systems having diierent vertical, as well as different horizontal, scanning rates. For example, a plurality of translating tubes may be operating such that an image is constructed in one tube while the image of another tube previously created isbeing scanned; the tubes would so alter- I rated an electronic scanning tube having therenate at a rate depending on the relative rates of repetition rates. According to this embodiment only one electron beam in each tube would be operating at ny one time so that there would be no interference between the two beams.

The receiver means may be of any suitable type such as that shown in Carlson Re: 20,700, issued April 19, 1938, or it may lbe of any other well known type. It is desirable to provide a receiver that is equipped to switch from one rate of scanning to another selected rate of scanning. This can be done by making a suitable adjustment of Such an arrangement" the blocking oscillator. is shown by Tolson et al. Patent 2,101,520, issued December '7, 1937, and assigned to /the Radio Corporation of America. Under certain condi` tions, it would be preferable to provide a. switch to change the blocking oscillator grid leak to a predetermined value so that the blocking oscillator would fall in step with any of the deflection rates sed at the broadcast transmitter.

From the foregoing, it will be apparent that various other modications may be made in this invention without departing from the spirit and scope thereof.

I claim as my invention:

1. In a television system wherein is incorporated an electronic scanning tube having therein a light-responsive mosaic electrode element, the method of intelligence transmission which includes the steps of projecting optical images upon the mosaic electrode element, scanning the mosaic electrode element with a plurality of electron beams, modulating each of said beams at different frequencies, deriving from the scanning a plurality of independent trains of signalling energy representing different degrees of resolution of the optical images and independently transmitting each of the plurality of produced trains of signalling energy.

2. In a television system wherein is incorporated an electronic scanning tube havingl therein a light-responsive mosaic electrode element, the method of intelligence transmission which includes the steps of projecting optical images upon the mosaic electrode element, scanning the mosaic electrode element with a plurality of electron beams, modulating each of said beams at a dierent frequency such that the output signal therefrpm occupies a plurality of independent bands of frequencies deriving from th'e scanning a plurality of independent trains of signalling energy representing different degrees of resolution of the optical images and independently transmitting each of the plurality of produced trains of signalling energy.

3. In a television system wherein is incorpof in a light-responsive mosaic electrode element, the method of intelligence transmission which includes the steps of projecting optical images vupon the mosaic electrode element, scanning the mosaic electrode element with a plurality of electron beams, modulating each of said beams at a predetermined frequency, deriving from the scanning a plurality of independent ytrains of signailing energy representing different degrees of resolution of the optical images and independently transmitting each of the plurality of produced trains of signalling energy.

4. In a television system wherein is incorporated an electronic scanning tube having therein a light-responsive mosaic electrode element,

the method of intelligence transmission which includes the steps of projecting optical images upon said mosaic electrode element, scanning the mosaic electrode element, deriving from the scanning a train of signal energy, utilizing one part of said energy to reconstruct said optical image in a plane parallel and closely adjacent to a second light responsive mosaic electrode element, and scanning said second light responsive mosaic electrode element to derive a train oi signal energy representing an image having ay degree of resolution diil'erent' from that of said recorded image.

5. In a television system, a photosensitive mosaic electrode element included within a cathl ode ray scanning device, means to project optical grecs of resolution of the optical images projected upon the mosaic electrode, and a plurality or transmission channels individually responsive to. .individual trains of the produced signallingenergy.

6. Ina television system, a photosensitive mosaic electrode element included within a accesos cathode ray scanningl device. lmeans to project optical images upon the mosaic element, means for repeatedly scanning the mosaic element com prising a. plurality of'electron beamsfmeans for modulating each or said electron beams with signals having dinerent frequencies and means to derive as a result of the scanning operationindependent trains oi signalling energy representative in diiferent degrees oi resolution oi the optical images projected upon the mosaic electrode. and a plurality of transmission channels individually responsive to individual trains of the produced signalling energy.

7. In a television system, an electronic tube including therein a photoelectric mosaic element, means to project optical images upon said mosaic, a plurality or independent cathode ray scanning means for deriving from the optical Y images projected upon'said mosaic element a plurality oi trains of electric signalling wave energy, means ior causing each ot said energy trains to have la dil'erent predetermined irequency band width representative of different degrees of optical resolution oi' the optical images, and means lto'transmit the derived plurality of said energy wave trains each over separate transmission channels. e

l l OSCAR B. HANBON.

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