DE1181834B - Electron image intensifier screen - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY GERMAN SjfflmS® PATENT OFFICE

EDITORIAL

Boarding school Kl .: HOIj

German KL: 21g-29/40

Number;
File number:
Registration date:
Display day:

N 16201 VIII c / 21g
3rd February 1959
November 19th. 1964

The invention relates to an electron image intensifying screen, consisting of a sequence of layers made of an electron-permeable metal film, a fluorescent luminescent layer and a Carrier layer made of metal oxide and a layer with an external photoelectric effect, as well as a method for its manufacture. Such an electronic device comprises means for generating an electron image, the electrons of which release light photons. This light is then noticed a photocathode from which electrons are released, the number of which is greater than that on the fluorescent one Layer falling electrons.

Activated zinc sulfide has long been used as phosphorus in the form of crystal powder. It has recently become known that a translucent amorphous layer of zinc sulfide can be formed. By activating it, you can give it a fluorescent effect that is comparable to that of powdered phosphorus. A process for the vapor deposition of zinc sulfide to produce a translucent amorphous layer on a support such as e.g. B. glass, and the subsequent activation of the zinc sulfide layer by heating and baking at a temperature of about 1000 ° C is by C. Feldmann and M. O ¹ Hara in the "Journal of the Optical Society of America", 47, no. 4, April 1957.

An electric discharge tube with a fluorescent photocathode has already been proposed, consisting of an electron-permeable aluminum layer, followed by a fluorescent layer, a further carrier layer made of aluminum oxide and finally a layer with an external photo effect is constructed. This known photocathode, like other known photocathodes, has the disadvantage that it must be applied to a relatively thick carrier plate which is sufficient for the cathode gives mechanical strength. However, a thick base means a decrease in image quality.

This disadvantage is avoided according to the present invention in that the fluorescent Luminous layer consists of a phosphor in an amorphous state and that the screen is partially of the amorphous fluorescent luminescent layer, the thickness of which is greater than 1 μ but smaller than 10 μ, is carried is, the carrier layer thickness about 1 μ amounts to. This amorphous fluorescent neon sign has sufficient inherent rigidity so that the actual carrier layer of metal oxide weseotiieh Electron image intensifier shield made thinner than the known photocathodes

Applicant:

National Research Development Corporation,

London

Representative:

Dr. B. Quarder, patent attorney,

Stuttgart O, Richard-Wagner-Str. 16

Named as inventor:

James Dwyer McGee, London

Claimed priority:

Great Britain 3 February 1958 (3453)

can be performed, whereby a much better image sharpness can be achieved.

A method according to the present invention for making an electron imaging device The screen comprises the following steps:

1.Preparation of a translucent layer of fluorescent material and a carrier layer,

2. the reactivation of the layer, if necessary, for the purpose of producing a fluorescent one Layer,

3. Coating one side of this layer with an electron-permeable metal layer and finally

4. To make one photocathode, apply a suitable layer on top of the other Page.

Usually the translucent layer of the fluorescent material can be deposited by deposition be prepared on a soluble film placed on a glass plate or wire mesh; this soluble "fern is then dissolved, whereby the insoluble layer applied to it becomes free> which is then applied to a suitable carrier.

The translucent © fluorescent layer can consist of, Züiksidfid, Wäkkanif,: G ^ kiumwalfrainat or other known fluorescent substances.

409 728/329

The support to which the fluorescent layer is applied must be thin, if a good one Image sharpness should be preserved. It can be made of aluminum oxide, magnesium oxide, a wire mesh or other suitable inert, heat-resistant substances. Aluminum oxide is particularly suitable for use as a carrier, since it is used to produce films with a thickness of approximately 0.1 μ that have the required heat resistance and mechanical strength.

The photocathode can be activated by depositing an antimony layer and then activating it of the antimony can be produced with cesium vapor for the purpose of producing a photocathode layer.

The aluminum and cesium layers protect the activated zinc sulfide layer against attacks the cesium vapor and in this way allow the production of a thin reinforcing screen, without the need for a glass slide.

Instead of an antimony-cesium photocathode, a photocathode comprising three alkali metals can be used be used in which the antimony alternates with each of the three alkali metals sodium, Potassium and Cesium can be activated.

For the purpose of a more detailed explanation of the invention, several embodiments are given as examples to be described in conjunction with the drawing. In detail ^ ejgt

F i g. 1 shows a partial step through an electron image intensifier screen on a much larger scale,

F i g. Figure 2 shows an electron optical device, partly in section, incorporating an electron image intensifier screen roughly in the manner of FIG. 1 contains.

According to FIG. 1, an electron image intensifier screen 10 consists of a translucent layer 1 of zinc sulfide activated with manganese and applied to a carrier 30. On the front side an electron-permeable aluminum layer 2 is applied to the layer 1. On the back of the A photoelectric layer 3 made of antimony activated by cesium is applied to the carrier 30.

In order to produce the screen 10, a glass plate with a very thin film of e.g. B. polyacrylic and polymethacrylic resin can be used. The glass plate coated in this way is placed in a vacuum chamber and placed on top of the film to form a crystalline layer Zinc sulfide vapor-deposited on the supporting side of the glass plate. One can also use the technique known per se use, according to the zinc sulfide is evaporated from a molybdenum shell, the resulting Layer has a thickness between 1 and 10 μ.

The coated glass plate is then immersed in Xylon in order to dissolve the acrylic-containing film, until the zinc sulfide layer has peeled off the surface of the glass plate. The zinc sulfide layer is now applied to a carrier 30, which consists of a held in a wire frame Wire mesh. The zinc sulfide layer on the support is then at a temperature of about 1000 ° C to reactivate the zinc sulfide, whereby a translucent Forms fluorescent layer of good effectiveness.

In place of an acrylic-containing resin according to the above-described method, ordinary ones can also be used Salt to be evaporated on a glass plate. After the zinc sulphide layer has been vapor deposited - as described above - the salt layer is made by immersing the plate in water dissolved.

In order to produce the screen 10 in F) g. _V 1, the zinc sulfide phosphor layer is covered on one side with a thin, almost opaque aluminum layer. This layer can be used before or after the layer is mounted in an electron-optical tube in which it is used In Fig. 1, the zinc sulfide phosphor layer is labeled 1 and this aluminum layer is labeled 2. The back of the zinc sulfide layer on the support 30 is covered with a thin layer of antimony, as required for activation as an antimony-cesium photocathode .

The screen is now mounted in an electron-optical tube, if this has not already been done. After evacuation and degassing - operations which are carried out in the usual way - the antimony film is activated by exposure to cesium vapor, the photoelectric compound SbCs _{3 being} formed.

^a 5 It is important to know that the zinc sulphide phosphorus would be attacked if it were exposed to the cesium vapor and that the cesium vapor would decompose the phosphorus and destroy its ability to fluoresce. Therefore, according to the method described above, the zinc sulfide layer is provided on one side with an aluminum layer and on the other side with an antimony layer. The cesium vapor cannot penetrate any of these layers and therefore cannot attack the zinc sulfide layer.

Another method of making the electron image intensifier screen 10 consists in that a film of aluminum oxide is first produced as a carrier. This film can be on a wire frame are applied and then serves as a carrier in place of the coated ones described above Glass plate on which the zinc sulfide layer can be deposited. The zinc sulfide layer is then activated by baking.

The aluminum oxide layer is electron permeable, so that the aluminum layer is on the front of the alumina film can be deposited. Optionally, the aluminum oxide film can also on a frame made of tempered glass or quartz, which also causes heating on the high Temperatures. It is conveniently about 1000 Angstrom units thick (corresponding to 0.1 μ). Such films are very transparent and tough. After evaporation of the phosphor layer on one side of such an aluminum oxide film becomes the Luminous phosphor layer reactivated by baking at a high temperature of about 1000 ° C.

Before or after mounting the aluminum oxide phosphor screen (Layers 30 and 1) in the tube in which it is to be used a layer of aluminum on the phosphor surface and a layer of antimony on the aluminum oxide layer vapor-deposited, the antimony layer then in a known manner with calcium vapor is activated.

This arrangement is more advantageous than that described above because of the incident electrons

do not have to penetrate the aluminum oxide film, with undesired energy losses occurring.

The operation of the electron image intensifier screen will now be described with reference to FIG. 1 of the To be explained in detail: In the electron optical device in which this screen is used is to be, the screen 10 with its fluorescent layer 1 is in the image plane of an electron image assembled.

The aluminum layer 2 is the impinging ι ο facing high-energy electrons that generate the electron image. The way of such an incident High-energy electron is shown by the dash-dotted line 4. The electron passes through the electron-permeable aluminum layer 2, dissolves at some point 5 within the fluorescent layer 1 from photons, which from the point 5 in all directions can go out. Possible paths of such photons are shown in FIG. 1 by the dashed lines Lines 6 and 8 shown. It can readily be seen that the lines 6 run directly to the carrier 30 and to the photoelectric layer 3, the incident photons electrons in the layer 3 make free. These electrons are removed from the surface by means of a suitable electric field of the photocathode 3 are pulled out and move along the dash-dotted lines 9 of FIG. 1.

Other photons released at point 5 run away from layer 3. These photons will reflected on the surface 7 of the aluminum layer 2, so that they are the by the dashed lines 8 follow the designated paths. After reflection, these photons also penetrate the photocathode 3 and free electrons in it - in a similar way to the photons coming along the paths 6. The electrons leave the photocathode 3 in a similar manner along the dash-dotted line Lines 9.

Photoelectrons are freed from the surface of the photocathode 3 within an area whose Diameter is approximately twice the thickness of the zinc sulfide layer 1. For the purpose of preservation a sharp electron image generated by the electrons incident along path 4, it is desirable that the zinc sulfide layer be as thin as possible.

Referring to FIG. 2, the electron optical tube 20 includes an intensifying screen 10 as described above with reference to FIG. In Fig. 2 correspond to the layers 1, 2, 3 and 30 of the screen 10 or the fluorescent layer, the aluminum layer, the photocathode and the carrier, as shown in FIG. 1 is shown. The tube 20 is an evacuated vessel 21 with transparent end faces 22. In addition to the screen 10, the tube 20 also contains a photocathode 11, which is arranged on the front side, and a fluorescent screen 17, which is arranged at the opposite end of the tube. Further electrons of the tube 20 are not shown. A magnetic field extending axially between the photocathode 11 and the screen 10 is maintained by a solenoid 12. The screen 10 is positively charged relative to the photocathode 11 by a voltage source 13. Similarly, as described above, the solenoid 18 generates an axially extending magnetic field between the screen 10 and the fluorescent screen

17. The screen 17 is kept at a positive level relative to the screen 10 by a voltage source 19. ■ ....-,

An object to be imaged is through a lens system 16 on the surface of the photoelectric Cathode 11 shown. Between the photocathode and the screen 10, the tube 20 contains a single-stage image intensifier, the resulting electron image being mapped onto the screen 10. The incident electrons that generate this electron image release photons in the fluorescent layer 1 off. These in turn liberate electrons from the photocathode layer in the manner described above 3. The number of electrons emerging from the photocathode 3 is greater than that Number of incident electrons. They are accelerated and thrown onto the fluorescent screen 17, on which an optical image is created, which is an intensified reproduction of the image that is transmitted through the lens system 17 is generated on the surface of the photocathode 11.

The arrangement of such an electron image intensifying screen is not an optical one Image enhancing device limited; Such a screen can also be used to for example to enhance the electron image generated in a television camera tube.

Claims (7)

Patent claims marriage: 1. Electron image intensifier screen, consisting of a layer sequence of an electron-permeable Metal film, a fluorescent luminescent layer and a carrier layer made of metal oxide and a layer with an external photoelectric effect, characterized in that, that the fluorescent luminescent layer (1) consists of a phosphor in an amorphous state and that the screen partially from the amorphous fluorescent luminous layer, their Thickness greater than 1 μ, but less than 10 μ, is worn, the carrier layer thickness being approximately Is 0.1 μ. 2. intensifying screen according to claim 1, characterized in that the carrier layer is a film is made of aluminum oxide. 3. intensifying screen according to claim 1, characterized in that the carrier layer is a film is made of magnesium oxide. 4. intensifying screen according to claim 2 or 3, characterized in that the carrier layer is in direct contact with the fluorescent layer. 5. intensifying screen according to claim 1, characterized in that instead of the carrier layer a is arranged in a frame held wire mesh. 6. A method for producing an intensifying screen according to one or more of the claims 1 to 5, characterized in that a translucent layer (1) is fluorescent Material is generated on a carrier (30) that the layer (1) reactivates if necessary is used to form a fluorescent layer that the fluorescent layer is on one side is provided with an electron-permeable metal layer (2) and on the other side is coated to form a photocathode. 7. The method according to claim 6, characterized in that the translucent · fraores ^ decorative layer is produced on a soluble film; which is produced beforehand on a glass plate or a wire mesh carrier - that ^; the soluble film is dissolved and the fluorescent layer is detached from the support surface and transferred to a heat-resistant inert support. Printed publications drawn in Btetrachü: Viola Patent No. 965 706 '; British Patent No. 694487; U.S. Patent No. 2,555,424. 1 sheet of drawings: 409 728/329 11.64 ι Bundesdruckerd BaUa