US2226997A - Television transmitter - Google Patents

Description

Dec. 31, 1940.

K. SCHLESINGER TELEVISION TRANSMITTER Filed Oct. 8, lss

Jnrehfar Patented Dec. 31, 1940 "Kurt Schlesinger, Berlin, Germany, assignor, by

mesne assignments, to Loewe. Radio, Inc., a corporation of New York Application October 8, 1935. Serial No. 44,063 In Germany October 11, 1934 .22 mamas;(01.17am) In the application Ser. No. 34,390 there is described a television transmitter, whichproduces image signals andsynchronisation signals simul taneously and at the sametime manages with a single rim' of image apertures on the Nipkow disc. .The method. by which the synchronisation signals are obtained'may be referred to as optical synchronisation. Th same is based onthe use of a special light source, which projects a simultaneous auxiliary light of the size of the image field On to the Nipkow disc. The desired black impulse signals result from omission of this auxiliary lighting and also of the primary lighting at the edge of the image field.

However, the auxiliary light renders a soiling of the apertures much more disturbing than in the usual methods, of course, especially in the dark parts of the image.

To avoid this disadvantage in operation, which could only be eliminated by keeping the Nipkow disc faultlessly clean, the method set forth in the following provides a remedy.

According to the invention, the auxiliary light is not as described above projected on to the whole image field, but in the form of a white strip on to the edge of the image only.

In Fig. 1, I is the largest field of image provided by the apertures of a Nipkow disc. According to the invention, the film picture 2 is made smaller than I. The resulting edge 3, which consequently would be black, is lighted by means of a special source of light more intensely than the brightest white in the image.

According to the invention, there is employed 35 for transmission preferably a negative film, the electrical amplifier behind the photo-cell by known means being made as to invert the light intensities.

When operating with a simple spiral disc the scanning of the edges 3 of Fig. 1 produces image and line impulses. When operating, with a double spiral disc, which is set forth in the application Ser. No. 36008 and serves for overcoming flickering of the image by interlaced scanning, 45 the anisochronous image change impulses necessary therein may also be produced automatically by a second transverse strip 4, which is situated not exactly over the centre of the image but is displaced therefrom to the extent of the width of one line.

The manner in which superimposed projections of this kind may conveniently be performed in practice is shown in Fig. 2.

When employing an arc-lamp 5 for lighting 55 r the film 6 by means of a reflector I the image of carbon shadow results, as well known, at, a point 9 nearer to the lens8 than l2. If there is situated at this point a small prism l0,. practically no light at all from the arc-lamp is lost, and-the sharpness of the film reproduction, which is produced on the disc by a second lens H, is also not interfered with. On the other hand it isnow possible to project through the medium of the prism l 0 onto the Nipkow disc a sharp image of a suitably removed diaphragm l3 by means of a 10 separate light source M, e. g. an incandescent lamp and a condenser l5. For this purpose the prism H] may be provided for example on the front side with a lens I6 of suitable focal distance. In order that the light intensities of the 15 contents of the image will have no efiect on the light intensities of the synchronisation strips '3 and 4, there is filed close to the film a diaphragm I3 which permanently blocks the arc-light 5 at those points at which the auxiliary light is pro- 20 jected. In this manner the light intensity and accordingly also the potential of the synchronisation signals remain constant. In all of these methods it is desirable to use a carrier frequency amplifier or a D. C. amplifier or a resistance am- 25 plifier with automatic generation of a bias of the so-called bypass amplifier in proportion to the basic intensity.

Naturally instead of the lamp an incandescent lamp or the like of very high candle power may 30 be employed.

I claim:

1. In a television system for transmitting image signals representing the pictorial portions of a motion picture film and also for transmitting synchronizing signals for synthesizing purposes, a light source, a scanning means, means for moving a motion picture film strip from which it is desired to produce the image signals intermediate the light source and the scanner, a first masking means intermediate the light source and the film, said masking means com-prising a substantially transparent portion and a substantially opaque portion for masking the light source from predetermined areas of the film, an optical system to focus light emerging from the restricted areas of the film as defined by the masking means upon the scanning means, a second light source of an intensity greater than the first light source, a second masking means having transparent and opaque areas complementary to those of the first masking means arranged in the path of the light issuing from the second light source, an optical means to focus the light issuing through the second masking means into the optical system used for focussing the film frame image upon the scanning device in such manner that the image of the transparent areas of the second masking means is brought into contiguous relationship with and juxtaposed to the light image emerging through the transparency of the first masking means, whereby in scanning by the scanning means output signals of varying intensity result in accordance with the illumination due to the film transparency and of substantially constant intensity and greater magniture result from scanning due to the illumination resulting from light emerging through the second masking means. 4

2. In a television system for transmitting image signals representing the pictorial portions of a motion picture film and also for transmitting synchronizing signals for synthesizing purposes, alight source, a scanning means, means for moving a motion picture film strip from which it is desired to produce the image signals intermediate the light source and the scanner, a first masking means intermediate the light source and the film, said masking means comprising a substantially transparent portion and a substantially opaque portion for masking the light source from predetermined areas of the film, an

optical system comprising a prism and a lens to focus light emerging from the restricted areas of the film as defined by the masking means upon the scanning means, a second light source of an intensity greater than the first light source, a second masking means having transparent and opaque areas complementary to those of the first masking means arranged in the path of the light issuing through the second light source, an optical means to focus the light issuing through the second masking means into the prismatic member of the optical system used for focussing the film frame image upon the scanning device in such manner that the image of the transparent areas of the second masking means is brought into contiguous relationship with and juxtaposed to the light image emerging through the transparency of the first masking means, whereby in scanning by the seaming means output signals of varying intensity result in accordance with the illumination due to the film transparency and of substantially constant intensity and greater magnitude result from scanning due to the illumination resulting from light emerging through the second masking means.

KURT SCHLESINGER.

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