US1987686A - Electronic receiver for disk transmitters - Google Patents

Description

Jan. 15, 1935. B. KWARTIN' I ELECTRONIC RECEIVER FQR DISK TRANSMITTERS Fil ed May 12 19:51

llll'lll ll on: o i 0 .Tnz)en?o r Bamako KwAa-rin Y Patented Jan. 15, 1935 UNITED. STATES ssuers Emomomc income you. man

Jill. i

This invention relates to the transmission of same.

. reasonable size of image the diameter of 'bination, construction,

It is among the objects of the present invention to provide a television system in which images, in the form of pictures and the like, are transmitted by means of a mechanical transmitter, such as the type employing a perforated disk, and are received by means of a cathode ray receiver. Heretoi'ore and prior to this invention no attempt has been made'to my knowledge to combine a mechanical transmitter and an electronic receiver in. order to obtain the. advantages which are inherent in such types of transmitters and receivers.

Those skilled in the art to which this invention appertains realize that television is faced with two most imperative requirements, one of which is to increase the size of the facsimile reproduction of the transmitted image and the other to increase the detail and at the same time decrease the distortion of the reproduced image. It is known that by increasing the diameter of the disk employed in the mechanical systems of television, larger received images may be obtained. However, for a the receiving disk would necessarily be too great to be safely or conveniently used in the home. It is also known that by reducing the size of the apertures in the disk and increasing the number thereof, a greater amount of detail is obtainable in'the received image but this also requires the use of a disk the diameter of which is objectionably great.

For transmitting purposes the objections against the use of a scanning disk are more readily overcome. because in the transmitting station the size of the disk presents no real dimculty. For receiving purposes the cathode ray tube offers the desired solution and it'only remains to devise some arrangement whereby the cathode ray tube, asa receiver, may be synchronized with the revolving scanning disk, as a transmitter. This I have accomplished by means of the present in vention andas'will be set forth in greaterv detail herein'aften- V Other objects of the invention will appear more fully hereinafter.

The invention consists substantially in the comlocation .and relative arrangement of parts, all as will appear more fully hereinafter, as shown in the accompanying drawing and as finally pointed ,out in the appended claims. For the purpose of more particularly explaining the principles of the present invention, it have described-in the following specification the application of my invention to that type 01 television transmitter whioh employs a revolving apertured disk for scanning the subject to be televised. It will be understood however that this invention is not at all limited to such a specific application inasmuch as it is equally applicable to any and all of the present known types of mechemical transmitters, such as the drum scanner, the mirror drum, etc.

In the accompanying drawinez- Figure l is an elevational view of a scanning disk employed in connection was. the present invention;

Figure 2 is a diagrammatic view of a transmitter arranged for operation in accordance with. this invention; and,

Figure 3 is a diagrammatic view of a cathode ray receiver for use with, the transmitter of Fig ure 2.

to ticularly to Figures 1 and, 2 thereof, it will be seenthat the television system the principles of the present invention utilizes a mechanical transmitter of the type employing a perforated scanning disk 10. This dish is suitably mounted upon a rotatable shaft 11 to which rotation is imparted of a suitable speed by a motor (not shown) As appears most clearly in Figure l the disk iii is provided with a suitable number of apertures 12 arranged in a spiral. While the r-lumber of these apertures may be varied within certain limita l believe best average results are obtained through the use of seventy-two holes with the disk making twenty revolutions per is to 1440 scanning lines per second or a signal frequency'of mill. g

In addition to the apertures 12, the disk 10 is provided with a circle of apertures 13, the total number of which. is Eli? or the number of apertures 12. As'appears quite cleariy in Figure 1, the circle of apertures 13 is well within the spiral of the scanning apertures 12. The disk 10 is also provided with a single aperture is disposed within the inner circle of apertures 13. Preferably, the single aperture 1.4 is of larger diameter than'either the apertures 12 or 13. With the disk 10 making 20 revolutions per second, it will be apparent that the apertures 13 will provide a frequency of 20x36 or 720, while the aperture 14 will provide a frequency of 20x1 or 20.- It will be understood of course that these frequencies are merely exemplary and may be varied as deemed expedient by changing either or both the number of apertures 12: and 13 employed or the speed of revolution of the disk.

Referring now to Figure 2 it will be observed that the subject to be scanned is positioned in front of the disk 10 so that the light rays reflected therefrom are projected through the scanning apertures 12. Immediately to the rear of the dish is a light responsive element 15, such as a photoelectric cell, this element being so positioned that it is successively influenced by the light passing through each of the several apertures during the rotation of the disk. The photo-electric cell is included in a suitable amplifying circuit and converts the light fluctuations into corresponding electrical variations which are superimposed upon and so modulate the usual'carrier wave employed in the transmission of electrical signals or impulses either by wire or radio. It is the signals or impulses thus established by the photo-electric constant light 18. The cell 16 is thus influenced frequencies, respectively. The purpose oi latter frequencies and the necessity for creating them will be apparent hereinafter.

At this point it is important to note-that the disk 10 is designed to rotate in one direction only, in this instance, in a counter-clockwise direction. This means of course that each of the scanning apertures 12 scans thesubject along a. single line and always in the same direction. The uppermost line is that obtained by the aperture 12 while the lowermost is that obtained by the sper ture 12 These facts are important and must he taken into consideration when it is realized that in a cathode ray tube the electron beam oscillates from side to side.

Referring now to Figure 3, it will be observed that the receiver therein shown is of the cathode ray or electronic type. This receiver, designated generally by the reference numeral 18, comprises a pair of tube members 19 and 20 separated by a partition 21'. While I prefer to construct these members 19 and 20 as an integral unit as ShOWiil, it is to be understood that'they may be constructed as independent units the circuits only of which may be electrically connected together.

The member 19 of my receiver is a tube of the .Braun type and includes a tin 'mionic cathode 21,

- within the imperforate plate 26. It will also be observed that the plates 25 and 26 are arranged memes the signals of 720 frequency which were produced by the transmitter (by lightrays from source 18 passing through apertures 13 and so influencing photo-electric cell 16--see Figure 2).

The stream 8, being a conductor, serves a dual purpose in the receiver, first, as an electrical connection between the plates 25 and 26 and second, to complete the circuit ior the thermionic cathode of the receiver member 20. This member 20, which as stated above may be formed as an independent unit, includes a thermionic cathode 2'7, a control element 28, an anode 29, a pair of plates so and 31 for deflecting the electron stream S in a horizontal plane, and a pair of coils 32 and 33 for shifting the stream S downwardly from the position which it tends normally to maintain.

The secondary thermionic cathode 27 has one terminal. thereof connected to the plate 26 while the remaining temiinal is connected in circuit with the primary cathode 21. secondary plates 30 and 33. are respectively connected to the perforated plate or grid 25 and imperforate plate 2%. in! proportioning the plates 25 and 26 such that the subtended by planes common to the opposite edges of said plates and intersecting at.

the anode is less than the angle through which the i5 oscillates, it will be apparentthat ior each oscillation of the electronic stream 8 the electrical connection between the plates 25 and 26 will be inteimipted twice} If the number of oscillations oi the stream S; is 720, it will be apparent that the circuit in which the deflecting plates 30 and iii are included will have a frequency of 1440 which is l to the scanning or image frequency establishe in the transmitter.

The t sided h flaring walls to provide at its outer end enlarged screen or target 34 the surface of which ssitehly treated to render it fluorescent when contacted by the electronic stream'S'. It is important to note that the anode 29 of this member is inclined with respect not only to the hoi'iso l but also with respect to the vertical. in tin particular instance, the axis of the anode projects toward the upper, right hand corner t e dui'nescent screen 3 when the latter is t lfitiloili. in the direction of the arrow. It will thus he apparent that when the stream S is uniniiuenced hy the plates 30-3l or by the coils 324% it tend to assume a position extendtog between said comer of the screen and the anode.

It will be remembered that in the disk trans initter the scanning is always in one direction for each line, sa from right to left. In addition, the lines obtained successively from top to bottom and never in reverse order. The cathode ray receiver most obviously operate in similar manher if auccessiful results are to be obtained. The deflecting plates til-31 insure obtaining horizontal deflections of the electron stream 5' equal in number per second to that produced by the revolvius dish. Que of these deflections is ob- 8' disappears only to reappear again along a line coincident with the axis of the anode 29 upon subsequent energization of the cathode 27. The stream the same direction, that In order to shift the electron stream S downwardly in accordance with the corresponding scanning sequence at the transmitter, the coils 32 and 33 are employed. As appears quite clearly in- Figure 3, these coils are located at top and bottom of the tube 20 and are included in circuit with a source oi? energy 35. The coils 32-33 tend normally to depress the stream S simultaneously as the deflecting plates 30-31 cause it to shift from right to left. Included in circuit is, from right to left.

with the coils 32-33 is a normally closed switch I top of the screen. Instantly, however, under the influence of the again energized coils 32-33 the stream S is again depressed simultaneously as it horizontally traverses the screen 34.

In order to increase the strength of the vertical deflecting coils 32-32 as the stream S moves out of its uppermost or normal position, it may be desirable to include a variable resistance 38 in circuit with the source of energy 35. The mov-' able contact 39 of this resistance unit is connected in series with the co 40 and is suitably carried by the movable armature 41 of the magnet. Normally, the contact 39 is in the dotted position but when the switch 36 is closed the coil 40 is energized as are the coils 32-33 in consequence of which the contact is shifted to decrease the resistance and sopermit advisable by those skilled It will of course be understood that the carrier wave as modulated by frequency produced by the apertures 12 of the disk, the deflecting frequency produced by the apertures 13, and the framing" frequency produced by the aperture 14, is received at the receiving station either by wire or by radio. At the receiving station, the several modulating frequencies are suitably by-passed in such-manner that while the relatively high frequency signals are supplied to the horizontal deflecting plates 30-31 of the receiver and the low frequency "framing" signals are employed to control the vertical deflecting coils, the image signals are employed to variably energize the' cathode ray tube 20.

It will be understood tion is not limited to the Editing system herein the present invenparticular type of transfore-described and that I accordingly,

8' thus moves horizontally always in of an electromasnet the scanning or image 3 its general principles are applicable to other systems of and real spirit of the invention and -to' claim the same broadly as well as specifically as indicated by claims.

What is claimed as new and useful is:-

1. In a television system, in combination, a transmitting means for scanning an object by a beam of light to produce a series of light fluctuations and having operatively associated therewith light sensifor transmitting said first and second sets of signals, an electronic receiver including p and secondary thermionic cathodes for producing a facsimile image 'of said object from glow points evolved by potential impressed upon said secondary cathode, said primary or hodebeing secondary cathode, said movement being always in the same direction and at a frequency equal to male.

that of said first set 2. In a television of transmitted si system, in combination, a

transmitting apparatus including mechanical means for scanning anjobject by a beam of light to produce a series of light fluctuations and having operatively associated therewith light sensitive means for converting said light fluctuations into transmissible electrical signals of a frequency corresponding to said light fluctuations,

means for generatstream for insuring the horizontal deflection of the secondary electronic streamat a frequency equal to that of said first set of transmitted signals, said interposed means being operated to deenergize the secondary cathode at the instant when said secondary electronic stream reaches the limit of its deflection in a given direction, thereby insuring a deflection always in the same direction.

3. In a television system, in combination, a

transmittingv apparatus including mechanical means for scanning an object by a beam of light to produce a series of light fluctuations and having operatively associated therewith light sensitive means for'converting said light fluctuations into transmissible electrical signals of a frequency corresponding to said light fluctuations, said apparatus also including means for generating a second set of signals of a frequency half that of said first-mentioned signals, and means for transmitting said flrst'and second sets of signals, an electronic receiver including primary and sec-= the appended apparatus including mechanical ondarythermionic cathodes, each of said cathodes lines the limit of the deflection thereof in one being adapted to produce an electronic stream, direction, and means for eflectlng the energize.- means for eflecting the horizontal oscillation of tion of said secondary cathode only during the the primary electronic stream, means for eflectperiod that said secondary electronic stream is 5 mg the horizontal deflection oi the secondary moving away from said aforementioned deflecelectronic stream, said secondary cathode being tion limit. relatively so arranged thatthe axis of the elec- BERNARD KWARTIN. tronic stream normally emanating therefrom de-

Images