US2175033A - Picture transmission - Google Patents

Description

Get. 3, 1939. K. SCHLESINGER El AL 2,175,033

I PICTURE TRANSMISSION Filed May 18, 1938 VoJfage 'F7T TI M J/ L Fig.1

Patented Get. 3, 1939 EYE i ii PIGTURE TRANSMIS SEGN Application May 18, 1938, Serial No. 208,528

4 Glaims. (Cl. 178-75) This application is a continuation-in-part of through the medium of a control Voltage radiated Ser. No. 532,462, filed April 24, 1931. at the edge of the picture. The transmitter ac- Among the considerable advantages which have cordingly transmits all three bands simultaneled to an ever increasing use of Braun tubes to ously. The transmitter and receiver must ac- 5 television reception purposes is the fact that eX- cordingly include three filter chains and three 5 tremely small controlling power inputs are reindependent amplifiers which the invention quired for the operation of such tubes. On the avoids. other hand this advantage is capable of being The change of the potential from maximum utilized in its full scope only if in the case of negative to maximum positive value upon change television reception apparatus of this description of picture or frame occurs, according to the in- 10 those parts which heretofore have been driven vention, automatically in the receiver by means by a motor may be omitted entirely, and replaced of a snap-initiated oscillation system and is by stationary devices operating purely electrically. merely maintained in pace from the transmitter. The problem is as follows: There are three volt- This mere control of the picture-changing may ages to be supplied to the tube: Light intensity be performed without the assistance of a special 15 voltage (for controlling the quantity or intensity control frequency, for example by the line-deflecof light at the picture elements), line-deflection tion frequency, if the latter is coupled with the of the light beam in line direction and framepicture-changing frequency automatically in the changing or picture-changing voltage (1. e. the necessary frequency ratio, for example 50:1.

voltage controlling the deflection of the light Electrical systems of this nature which maintain 20 beam in a direction perpendicular or at least a given frequency ratio with extreme reliability, transversal to the line direction. For reasons of are known per se. An example is the frequency a practical nature the simultaneous transmission reduction connection employing gaseous conducof all three frequency bands on the same carrier tion lamps, possibly in an arrangement of tubes Wave is absolutely essential. according to Fig. 2. 25

Reference is to be had to the accompanying Fig. 2 shows a two-stage reduction system of drawing, in which Fig. 1 is a diagram illustrating this kind, for use in those cases in which a single the relation of voltage to time, while Fig. 2 is a stage does not provide a frequency division of a circuit diagram of a frequency reduction device sufiiciently steady kind. The connection system such as may be used in connection with our inmay operate, for example, in such manner that 30 vention, and Fig. 3 is a circuit diagram of a by reason of a periodical voltage applied to the typical embodiment of our invention. first grid there occurs a charge of the condenser The present invention relates to the generation and, corresponding to this charge, a variation in of the line deflection voltage and the picturethe voltage of the anode up to the instant when changing voltage, and comprises the use of a the gaseous conduction lamp is caused to light. 35 snap-initiated oscillation, especially an oscillation This instant occ r re ul rly af er a cer ain numof saw-tooth or so called relaxation oscillations ber of cycles on the input side, for example after and especially to the synchronisation of the pic- 10 cycles. A. similar operation occurs in the secture-changing voltage, on the one hand with the ond stage so that the total resulting change is line-deflection voltage and on the other hand to a period or req y w h is qu to the 40 with the change of picture in the transmitter. p oduct Of the Variation in both Stages. In m- Assuming in the first place that there is a moving i s. according to the invention, a f q n y roll of film on the transmitter the verti al reduction device of this or a similar kind with'a progress of the line-deflection the receiver must e ev s o Sy having Brawl tubes, y rooccur evenly from the upper to the lower edge of nous scanning o the picture is p o ed, or eX 45 the picture, and then spring back with a jerk to mp e, as ol ows: the upper edge when the picture is changed. Th In connection with the transmitter it is ascorresponding time curve of the voltage at the sumed that there is a horizontally oscillating picdefiecting plates (vertical plates of the Braun tum-decomposi Scanning means and a tube) is shown in Fig. 1. steadily moved film. The advance of the film and 50 In one known arrangement the picture ohangthe line-Scanning Operation may be Coupled m ing voltage is produced by charging a condenser chanically in very simple fashion, so that there over a saturated electronic tube. The initiation are for instance exactly 100 lines to each picture of the condenser discharge upon the change of or frame. The line frequency is, in the known the picture is efiected from the transmitter manner, conjointly transmitted to the receiver by 55 "up on means of a longitudinal edge, or possibly a double edge, is there filtered, amplified, and employed in direct manner for transverse deflection, i. e. in the line direction of the cathode ray. The same frequency is simultaneously passed to the frequency divider (1:50 for scanning to and fro, or 1:100 for scanning only in one direction), and emerges from the same in the form of the frame-changing voltage in correct frequency and characteristic as saw-tooth line voltage. If in addition there is also a tone selection for filtering out the line tone from the reception band, an arrangement is arrived at in accordance with Fig. 3.

Fig. 3 shows a receiving apparatus according to the invention in diagrammatical form. The receiver E picks up simultaneously: on the one hand the current for subsequent amplification purposes for the picture or frame amplitudes by means of a device N which, in connection with the present invention, does not require to be described in detail, and on the other hand the line frequency, which is preferably transmitted conjointly by the transmitter, for example a frequency of 750 cycles. The line frequency, according to Fig. 3, is passed to a device T for selection of the tone. This tone-selecting device-which in contradistinction to the three filter chains hitherto required may, in the case of our invention, be the only oscillation selector employedcan consist of a tuning fork arrangement or a similar electro-mechanical vibration device, by means of which the whole of the middle and the high frequency oscillations of the frame amplitude are eliminated and merely the one frequency (the line deflection-frequency amounting, for example, to 750 cycles is transmitted with practically constant amplitude to the amplifier V, which permits the amplification of this frequency. It is important that the output power of this amplifier should maintain a constant value, as it is only under this condition that frequency reduction to certain constant amounts will be successful. Variations in the output power might occur upon fluctuations of the line-frequency, upon variations in the degree of amplification on the part of the tone amplifier etc. In order to preclude these disturbing influences the input amplifying and end stages of the tone amplifier area according to our invention, so dimensioned that from the end stage the maximum power pertaining thereto is always transmitted to the remaining parts of the television apparatus.

From the tone amplifier V the line frequency is for the one part conducted in direct fashion to the one pair of plates P1, P2 of the Braun tube for the purpose of line deflection (the oscillations transmited thereto may be for instance of sine form). Furthermore, the oscillations are passed by the amplifier V to a frequency dividing system A, which in Fig. 3 represented diagrammatically in single stage form by a gaseous conduction lamp G, battery B, movable plate condenser C" and resistance W. If, for example, there is a frequency reduction down to the one-fiftieth part, there results at the ends of the resistance W a periodical fluctuation in voltage of the frequency [5. This is conducted to the pair of plates Q1, Q2 of the Braun tube. To enable the same to be utilized as a vertical deflection for the sudden change of the frame or picture, a fluctuation in potential is required approximately in the form according to Fig. 1. And this in particular may be achieved in reliable and simple manner through the medium of the frequency reduction circuits employing gaseous conduction lamps.

In those cases in which a synchronized main supply of electric current is available, the picture-changing frequency may be taken therefrom by way of a frequency reduction or of a synchronously controlled relaxation or saw-tooth oscillation. Vice versa, it is possible to utilize; the picture-changing frequency, which is produced by a synchronited main supply or by a tuning fork generator with the assistance of frequency reduction, or is taken in any other suitable manner from a low frequency generator without frequency reduction for the production of the line deflection frequency by taking the latter from the picture-changing frequency in the form of a higher harmonic, for example by way of a tone selection device, or by means of any suitable apparatus for raising the frequency in reliable manner, for instance an apparatus of that particular type which is based on the curvature of a characteristic.

Controlled saw-tooth or relaxation oscillations are also useful in other instances. in connection with the television apparatus employing Braun tubes; quite generally, they effect the transformation of a sine voltage into a snap-initiated line voltage of a frequency reduced in any degree desired. This, for example, is absolutely essential when transmitters performing the scanning operations by means of a Nipkow disc are employed in conjunction with receivers using Braun tubes. The line-tone in this case is not conducted in direct fashion to the transverse deflection elements of the Braun tube, but is first employed for controlling a saw-tooth oscillation of the same frequency, and only the voltage at the condenser, which is the desired line-voltage, is passed to the tube.

Our invention is not particularly confined to television. The same may also be employed for other picture transmission purposes for example for film transmission.

We claim:

1. A television receiving system comprising a receiver adapted to pick up intensity controlling oscillations and synchronizing oscillations of a frequency emitted by a television transmitter, a selector for separating the synchronizing oscillations from the intensity controlling oscillations, a Braun tube having two ray deflecting systems, means to couple one of said systems to the output of said selector so that the beam is deflected in one direction at the received frequency, and frequency demultiplying means also coupled to the output of said selector, the other system being operated by said synchronizing oscillations through said demultiplying means whereby to deflect said ray in another direction.

2. A television receiving system. comprising a receiver adapted to pick up intensity controlling oscillations and synchronizing oscillations of a frequency emitted by a television transmitter, a selector for separating the synchronizing oscillations from the intensity controlling oscillations, a Braun tube having two ray deflecting systems, the first of said systems including deflecting means for deflecting a ray horizontally, means to couple the first of said systems to the output of said selector so that the beam is deflecting horizontally at the received frequency, the second of said systems including means for deflecting said ray vertically, and frequency demultiplying means also coupled to the output of said selector, thev said second system being operated by said synchrcnizing oscillations through said demultiplying means whereby to deflect said ray vertically.

3. A television receiving system comprising a receiver adapted to pick up intensity controlling oscillations and synchronizing oscillations of a frequency emitted by a television transmitter, a selector for separating the synchronizing oscillations from the intensity controlling oscillations, a Braun tube having line scanning means and frame scanning means, means to couple said line scanning means to the output of said selector so that the beam is deflected in a line scanning direction at the received frequency, and frequency demultiplying means also coupled to the output of said selector, said frame scanning means being operated by said synchronizing oscillations through said demultiplying means.

4. A television receiving system comprising a receiver adapted to pick up intensity controlling oscillations and synchronizing oscillations of a line scanning frequency emitted by a television transmitter, a selector for separating the synchronizing oscillations from the intensity controlling oscillations, a Braun tube having line scanning means and frame scanning means, means to couple said line scanning means to the output of said selector so that the beam is deflected in a line scanning direction at the received frequency, and frequency demultiplying means also coupled to theoutput of said selector, the frame scanning means being operated by said synchronizing oscillations through said demultiplying means whereby to deflect said ray in another direction.

KURT SCHLESINGER.

MANFRED VON ARDENNE.

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