US2163216A - Television transmission arrangement - Google Patents

Description

June 20, K SCHL GER TELEVISION TRANSMISSION ARRANGEMENT Filed Oct. 19, 1935 2 Sheets-Sheet l Jnren/ar June 20, 1939. K. SCHLESINGER 1 TELEVISION TRANSMISSION ARRANGEMENT Filed Oct. l9, 1935 2 Sheets-Sheet 2 22 f Li r fl 25 r1 Ll Jxrren/ar Patented June 20,. 1939 UNITED STATES PATENT OFFICE TELEVISION TRANSMISSION ARRANGEMENT Steglitz, Germany Application October 19, 1935, Serial No. 45,729 In Germany October 25, 1934.

3 Claims.

The subject matter of the invention is the technical execution of an optical television transmission method, which is characterised in that, by the use of a single photo-cell and one photoamplifier, the contents of the image and also the synchronisation signals are produced by the same series of scanning apertures of a Nipkow disc. The present invention proceeds beyond the first application Ser. No. 683.735 insofar as the same operates with a double-spiral disc according to the method of interlaced groups of lines. The production of the image-change signals is also a different one.

The invention will be best understood by reference to the accompanying drawings: of which Fig. 1 shows the principal idea of composing the projection of the image on the double-spiral disc and of a white margin adjacent to one or more edges of the projection.

In Fig. 2 there is illustrated a double-spiral disc with two scanning slots for producing synchronising impulses for the respective image changes.

Fig. 3 shows a differentiation connection system for avoiding a brightening of the received images which is necessary in the case where bright edges are employed for image synchronising purposes.

Referring to Fig. 1, l is the film, which passes 30 between two guides 2 and 3 of normal spacing from the top towards the bottom through the plane of the drawings. A reflector 4 projects the lightof an arc-lamp 5 in the form of a wide,

evenly lighted cone over the film surfaces of l. 3 6 is a metal rail, by means of which the sound strip is eliminated. The lenses l0, project an image of the film onto the screen of a Nipkow disc ll provided with a double spiral of apertures. A part of the light coming from the reflector is intercepted by lens II and conducted by the two totally deflecting prisms or reflectors I and 8 and through a slitted diaphragm 9, also to the lenses Ill, l0, so that there is obtained a sharp reproduction of the diaphragm 9 in the form of a white edge 9 of the film image I. In place of the described transmitter having a common light source for image and synchronizing projection there may also be employed two different light sources for the two projections. 50 By the stated optical measures it may be accomplished that the light intensity on the marginal portion 9 is always greater than the light intensity of the reproduction I, so that the synchronizing signals, which are produced upon the passage of the apertures in the disc I! over the synchronisation edge 9' will always be much stronger than the image signals.

According to the. invention, the modulation amplifier l4 coupled with the photocell 12, on to which a reduced reproduction of the surface I is projected by the lens [3, is so adjusted that upon the arrival of the light signals of the synchronisation edge 9' its end stage I5 is just entirely currentless. The modulation of the wireless transmitter takes place in the method according to the invention in such a manner that in the case of black in the image the aerial current vanishes. In the case of white in the image the transmitter is fully utilized, and in the case of synchronisation signals the aerial current is amplified beyond the normal. In this way, ascompared With the black impulse method hitherto employed, there is obtained the advantage that the synchronisation signals overtone all interferences, as they are the loudest signals in the course of the entire television transmitter. If a screening or amplification is desired of the light impinging on the film surface, there is actuated either directly or by distant control an optical diaphragm [6, which takes effect only on that portion of the light which passes through the film l, and not on the portion assigned to the synchronization system ll, 8, 9, 1,. By reason of this purely optical adjustment of the transmitted intensity there is obtained the advantage that (1) the intensity of the synchronisation signals always remains constant.

(2) The height of the synchronisation signals remains constant independently of other fluctuations, as the same is definitely determined by the vanishing point of the current of the final stage.

(3) The amplifier I4 is able to be adjusted to a faultless linearity of all tube characteristics, and accordingly to good reproduction of the halftones of the images, and is not adversely affected by regulating operations.

The generation of the line-synchronisation signals takes place when an aperture traverses the white edge, A rotary spiral diaphragm [8 obscures alternatively one of both aperture spirals. The generation of the long impulses for the frame change takes place by means of two slots in the spirals. In Fig. 2 there is shown a plan view of the double spiral disc ll, there being recognizable the reproduction of the film I and the reproduction of the white edge 9. The two slots I9 and I9 have a tangential length corresponding to one line; they are staggered in relation to each other to the extent of a. half line period. The radial manner by the action of the slot signals with' staggered commencement a line group displacement takes place at the receiving end, in the.

earlier application Ser. No. 36,008/35.

As regards the receiving end, it now requires to be explained in what manner a brightening of the edges of the received images or a strong aocentuation of the return lines in both directions of the image may be avoided. Fig. 3 shows a par-" ticularly suitable form of embodiment of the solution to the problem using the known'method that from the scanning relaxation oscillations produced at the. receivingend negative blocking impulses are derived by electrical differentiation and conducted to a light-control element of the television tube. Thesolution set forth in Fig. 3 avoids the disadvantage which would result when mixing blocking impulses and image impulses on the same light-control electrode of the Braun tube, viz, a deterioration in the sharpness of the image by reason of capacitative loads on the light control line. A television tube of the latest construction possesses a control grid 2| as closed as possible covering the cathode 20 and shortly behind the grid a condenser electrode 22 which, by means of electrostatic lenses 23, 24, concentrates the electronic ray on to the aperture of a diaphragm 25; whereupon later, by electronoptical means, there takes place a reproduction of the aperture of 25 on the luminous screen. According to the invention the blocking of the ray does not occur at the control grid 2|, which is connected with the final tube 26 of the television receiver by a line 21, which is poor in capacity, but theline 28, which is traversed by a bias and the blocking impulse, is connected directly with the condenser 22. Certainly a more powerful potential is then required for blocking purposes, but complete independence is obtained from the occurrences in the grid circuit. The blocking'potential is furnished by the secondary of a push-pull transformer 29, which is tuned to the highest frequency component of" the particular relaxationcurves and preferably'has an iron core, and the primary coils of which are in series with resistances 3|, 32 connected to the anodes of the push-pull amplifier valve 30 and to the anode battery 35. The deflecting plates of the Braun tubev are connected to the anodes through the medium of condensers 33, 3 4. For the frame change amplifying tube 36 there is employed a similar transformer, with a somewhat lower natural oscillation. 'Its secondary coil 31 fined to the use of push-pull amplification. The same method is also capable of being performed .with simple relaxation amplifiers 30, 36 and with only one primary coil 29. It is then merely necessary to employ a transformation ratio of twice the amount. As regards the differentiation the impulse transformers are suitable for this purpose .if 'and only if theirv apparent inductive impedance at the primary winding remains substantially smaller'than the ohmic anode resistance.

'As well known, the derivation of the synchronisation signals from the image change signals requires to take place through the medium of an amplitude filter. In contradistinction to the method of black impulse signals, the anode of the diode 40. is connected to the image current line 21. A suitable bias 4| is imparted to the cathode. The two kinds of synchronisation impulses passing the valve 40 are separated one from the other one by a CR member 42 and an RC member 43 the middle terminal of which is connected to the grids of the respective relaxation oscillator and further, via amplifiers, to the grids of the tubes 30 and 36. These connections, as well known, are not designed.

I claim:

1. A'television film transmitter arrangement for interlaced scanning comprising a scanning disc having two spirals of apertures, a photo-electric cell arranged in operative relationship thereto, means for projecting an image of the film to be transmitted onto said scanning disc, means for additionally projecting a light margin of great brightness onto one edge of said image projection, a slot in each of both spirals and means for producing line synchronizing impulses and frame synchronizing impulses by the light from the White margin impinging the photo-electric cell through the scanning apertures and the slots, respectively.

2..A television. film transmitter arrangement according to claim 1, said slots having the form of an arc corresponding to the length of a line and being staggered in relation to each other to the extent of half'a line.

3. A television film transmitter arrangement according to claim 1, said slots having the form of an arc corresponding to the length of line and being staggered in relation to each other to the extent of half a line, the means for projecting the said light margin comprising a separate light source.

KURT SCHLESINGER.

Images