US2172727A - Electronic image tube - Google Patents

Description

Sept. l2, 1939.. E. BRUCHE r-:r AL 2,372,727

ELECTRONIC IMAGE TUBE Filed NOV. l2, 1935 Patented Sept. 12, 1939 TED STATES PATENT FFICE Schaiernicht, Berlin, Allgemeine Elektricita Germany, assignors to Gesellschaft, Berlin,

Germany, a German corporation Application November 12, 1935, Serial No. 49,332

Germany November 9, 1934 4 Claims.

This invention relates to electronic image scanning tubes for use in television transmission.

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

In the picture plane of the electron image (iluorescent screen) is formed a tiny aperture of a size equal to that of the desired scanning element or elementary area, i. e., about 1 sq. millimeter large. In the rear thereof is the electron collector. 'I'he electron-optical picture is caused to move past the opening of the cage by the agency of deecting means of electric or magnetic nature as known in the prior art. W'hat results are current impulses which in the usual way are transmitted to a distant place and which may be employed for re-creating the image.

In this method only a very small fraction of the electron intensity is capable of being utilized (around 1Amoco).

'Ihe present invention discloses ways and means insuring a substantially more favorable scanning in that the screen is subdivided into a great num- 2 ber of minute surface elements of a metallic layer (metallic grating or screen), which, in turn, are disposed in front of a common metal plate', so that the constituent surface elements form the coats of condenser These surface elements are not completely insulated in reference to one another, in fact, a certain amount of conductivity prevails between them so that, when the electron-optic picture or pattern is impinged thereon, they are unable to acquire a charge beyond a certain limiting value.

If, then, in addition to the optical picture, a luminous spot is projected from the outside upon a photo-cathode which is swept at a rate of speed adapted to the screen, an electron spot of correspending strength will be -caused to move over the plane of the electron-optic image, and as a result the impacted surface elements will momentarily be charged to a certain limit. The charges which these surface elements are able to acquire will be a function of the charges of the same already caused by the image. In other words, the sweeping of the electron spot over the plane of the image will result in current impulses of varying intensity, and these are carried off by way of 50 the second coat of the condenser and may be utilized, as known in the art, for the transmission of a television picture.

An arrangement adapted to practice this method is schematically illustrated in the annexed drawing.

Confined inside a high-vacuum tube I is a photo-active cathode 2 (say, in the form of a layer of potassium). Opposite the same is disposed a coat of metal 3 which is divided into a great number of minute elements, these surface 5 elements conjointly with a layer 4 possessing low electric conductivity and a common metal plate 5 forming tiny condensers. 6 is the anode of the electron-optic system, and 'I the imaging element, say, a magnetic lens. lo

What We claim ls:

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 support- 1 ing a layer of poorly conducting material upon which is supported a plurality of elemental photosensitive particles, a continuous layer photoelectric cathode opposite said electrode, said cathode having an area commensurate with the area of 20 said electrode, means to project an optical image von said cathode to release electrons to 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 cathode point by point by a beam of light to release electrons therefrom to further charge the photoelectric particles of said electrode to a predetermined limiting value.

2. An electronic image transmitter comprising a mosaic electrode having a metal plate, a poorly 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 and in register with said electrode, means to project an optical image of an object to be transmitted upon said cathode to release electrons 40 therefrom to provide an electron image of the opti-cal image, means to direct the elec on image 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 simultaneously charge the photosensitive particles to a predetermined positive potential, means to scan the photoelectric cathode point by point by a beam of light to release electrons therefrom to further charge the photoelectric particles of said electrode to a predetermined limiting value, and means for producing a positive potential equal to the diierence in the charge of the parthe electron' image and the the electrons released by the evacuated cylindrical envelope, a mosaic of ele-v mental 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 scan the photoelectric cathode point -by point by a beam of light to release electrons therefrom to further charge the -photoelectric particles of said electrode to a predetermined limiting value. 4. 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, 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, means to produce electrical signals representative of the difference between the charge produced by the electron image and the predetermined positive potential produced by the light ray, and means for producing `a positive potential equal to the diierence in the charge of the particles produced by the electron image and the charge produced by the electrons released by the beam of light.

WALTER SCHAFFERNICITI. ERNST BRCHE.

Images