US2172726A - Electronic image transmission - Google Patents

Description

Sept, l2, E939. E. BRUCHE ErAl.

ELECTRONI C IMAGE TRANSMI SSION Filed Nov. 9, 1955 ELECTRO tiny condensers.

Patented Sept. 12, 1939 UNITED STATES PATENT OFFICE 2,172,126 ELECTRONIC IMAGE 'mANsMrssIoN Application 4 Claims.

This invention relates to an image transmission system, and, in particular, to an electronic device for converting Ioptical images into electrical signalling representations of the opticalimage.

It is known from the prior art to scan a simple electron-optic pattern or image of the kind nowadays used, for instance, in television work, in the following manner:

In the plane of the electron image (fluorescent screen) is formed a small aperture equal in size to the desired scan element, that is; about 1 square millimeter. Posteriorly thereof is mounted the electron-collector. The electron-optic image, by the use of electric or magnetic deection means known in the art, is caused to move past the opening of the cage. What results therefrom are current impulses which are transmitted in the usual Way and may be used for re-creating the image.

One serious demerit of this method resides in the fact that only an extremely small fraction of the electron intensity is capable of being utiliZed (Ca. ]0,000)

According to this invention a more effective scanning of the electron-optic picture is obtained by that in the plane of the electron-optic image a grated layer (photo-layer) is arranged, in the rear of which is provided a plate consisting of material of low conductivity which, in turn, is placed upon a metallic plate. The constituent surface elements of the grate in this manner form The electron-optic image produces different charges on the individual grate elements in the plane of the image. Superposed upon the electron-optic picture is an intermittent scanning action by a concentrated beam of light. By the scanning action of the latter, the constituent elements of the grate or mosaic surface are positively charged to a certain limiting value, and this results in the production of current impulses which are carried off by way of the condenser coat and may be used, for instance, for th'e transmission of a television picture.

An' arrangement adapted to practice the said method is schematically shown in .the annexed drawing.

Inside a high-vacuum tube I of the kind for practicing electron-optic methods is mounted a photo-active cathode 2. Opposite the latter is disposed a grate or mosaic surface 3 (photo layer or coat) in the rear of which is arranged a coat consisting of poorly conducting material and which, in turn, is placed upon a metal plate 5. 6

November 9, 1935, Serial No. 48,984 Germany November 9, 1934 (Cl. P18-7.2)

designates the anode, while 1 denotes the electron-optic image element, say, a magnetic lens.

In operation the picture, Whosev image is desired to be transmitted, is projected upon the photo-layer 2, which layer ejects electrons in ac- 5 cordance with the intensity of illumination on the elemental areas of the layer. The electrons are then focused upon the mosaic 3 and serve to charge the elemental areas of the mosaic in accordance with the density of the electrons repre- 10 sentative of the optical image. A highly concentrated beam of light then scans the mosaic and elevates each of the mosaic elements to a fixed positive voltage, the diierence between the initial charge and the final positive charge serving to produce a flow of current through the back plate 5 which is then suitably amphi-led and transmitted.

What we claim is:

1. An electronic image transmitter comprising an evacuated cylindrical envelope, a mosaic electrode positioned at one end of said envelope, said electrode comprising a conductive plate supporting a layer of poorly conducting material upon which is supported a plurality of elemental photoelectric particles, a continuous layer photoelectric cathode opposite said electrode, said cathode having an area commensurate with the area of said electrode, means to project an optical image on said cathode to release electrons to 30 produce an electron image of the optical image, means to direct and focus the electron image upon the photoelectric particles of said electrode to produce a charge image of the electron image, and means to scan the photoelectric particles by a beam of light to release electrons therefrom to charge the said particles to a predetermined positive potential.-

2. An electronic image transmitter comprising a mosaic electrode having a metal plate, a poorly 40 conducting material coating one side of said plate, and a plurality of photosensitized particles positioned on said poorly conducting material, a continuous layer photoelectric cathode parallel to 5 and in register with said electrode, means to project an optical image of an object to be transmitted upon said cathode to release electrons therefrom to provide an electron image of the optical image, means to direct the electron image 50 upon the photosensitive particles to charge them to produce a charge image of the electron image, means to scan the mosaic electrode by a beam of light point by point to produce electrical signals representative of the charge image and to simul- 55 Cil taneously charge the photosensitive particles to a predetermined positive potential.

3. An electronic image device comprising an evacuated cylindrical envelope, a mosaic of elemental photosensitized particles supported on a layer of poorly conducting material which layer is in turn supported on a metallic plate to provide a plurality of elemental condensers, a continuous photoelectric emissive surface parallel to and in register with said mosaic, means to project an optical image of an object upon said photoelectric emissive surface to produce an electron image of the optical image, means to focus the electron image upon the mosaic of the photosensitized particles to produce a charge image of the electron image, and means to scan said mosaic point by point by a concentrated light ray, to eject electrons therefrom to charge the said particles to a predetermined positive potential.

4. An electronic image device comprisingan evacuated cylindrical envelope, a mosaic of elemental photosensitized particles supported on a layer of poorly conducting material which. layer is in turn supported on a metallic plate to provide a plurality of elemental condensers, a continuous photoelectric emissive surface parallel to and in register with said mosaic, means to project an optical image of an object upon said photoelectric emissive surface to produce an electron image of the optical image, means to focus the electron image upon the mosaic of the photosensitized particles to produce a charge image of the electron image, means to scan said mosaic point by point by a concentrated light ray, to eject electrons therefrom to charge the said particles to a predetermined positive potential, and means to produceI electrical signals representative of the diierence 'between Vthe charge produced by the electron image and the predetermined positive potential produced by the light ray.

' WALTER SCHAFFERNICHT.

ERNST BRCHE.

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