US2220181A - Cathode ray tube - Google Patents

Description

NOV. 5, 1940. I SITEUDEL ET AL 2,220,181

CATHODE- RAY TUBE Filed June 22, 1957 INVENTORS PEER/MRO srzuoa .4026 4/. JOIlANNESSO/V A'l'TRNEY Patented Nov. 5, 1940 PATENT OFFICE 2,220,181 GATHODE RAY TUBE Eberhard Steudel and Jurg Johannesson, Berlin, Germany, assignors to Allgemeine Elektricitats Gesellschaft, Berlin, Germany, a'corporation of Germany Application June 22, 1937, Serial No. 149,576 In Germany June 26, 1936 1 Claim.

The invention relates broadly to apparatus embodying the use of a cathode ray, and more particularly to a cathode ray tube structure which is particularly adaptable to use in television.

The life of a Braun or cathode ray tube depends largely upon the life of the filament of the cathode. Once the latter has blown or has been burned through, the entire tube becomes unserviceabie. Braun tube having a long life is created by using a photo-cathode for the cathode. The spot, as known in the art, may be produced by imaging the cathode or a stopper or diaphragm mounted anteriorly thereof. Illumination of the photocathode may be produced either by means of naural light or else by an artificial light source. For this purpose will sufiice an ordinary glowlamp, say, a pocket lamp which may be readily replaced in case it blows, and with which, under certain circumstances, the photo-cathodes of several Braun tubes may be illuminated simultaneously.

One exemplified embodiment of the Braun tube here disclosed is shown in the appended drawing. The Braun tube I is furnished with a photoelectric cathode 2 which is illuminated by the aid of a light source 3 and, optionally, an interposed lens 4. If the photocathode is of the transparent or translucent kind, illumination could be also posterior. The electrons which are released from 2 are projected by means of an accelerator cylinder 5 upon a fluorescent screen 6. The potential field between 2 and 5 is in the shape of an electric lens. If desired, additional electric or magnetic lenses could be provided. I and 8 are pairs of deflector plates known in the earlier art, and of these or both may be replaced by pairs of deflector coils. In addition, diaphragms, stops and electron lenses may be provided for the purpose of insuring limitation or stopper (focusing) eliects upon the beam or pencil and for intensity modulation.

Another embodiment of the basic idea of this invention consists in disposing between light source 3 and photo-cathode 2 a replaceable or removable pattern or vignette 9 by the aid. of which a spot of special shape may be projected According to the present invention, a

upon the photo-cathode, say a line, which, when the cathode is imaged upon the luminescent screen will produce a spot upon the screen of corresponding form. This may prove advantageous for certain purposes, say, for sound-film work. It is thus feasible to render one and the same tube useful for several kinds of work, whereas in the past special ways and means had to be adopted in the interior of the tube for the purpose of producing a luminous line of the sort required for sound-film work (cylinder lenses or equivalent means).

According to this invention also an intensity modulated source of light could be employed. It is thus possible, for instance, in television equip- 15 ment, to insure intensity modulation and line modulation (or line scan) in two distinct tubes so that mutual interference of the two control or modulation actions will be eliminated to a large extent. Moreover, each of these tubes may 20 be designed in a way so that it will give greatest satisfaction in the particular kind of Work for which it is intended. The light source, in this instance, may consist either of another cathoderay tube (and if desired, the latter could also be 25 furnished with a photo-electric cathode and distinct light source just like the tube of the invention), or else a glow-tube, Kerr cell or any other intensity controlled source of light.

What is claimed is:

A cathode ray system comprising a cathode ray tube having an envelope including photo-electric cathode means for releasing electrons, means for concentrating said electrons into a beam formation, means for accelerating said electron beam formation, and a screen adapted to give ofi' light in response to the impingement of said cathode ray beam thereon, a source of light positioned external to said tube envelope, and removable pattern means positioned between said source of light and said photo-electric cathode whereby the light from said light source passing through said removable means and impinging on said photoelectric cathode has a definite predeterminable pattern.

EBE-RHARD STEUDEL. J URG J OHANNESSON.

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