HAMAMATSU IMAGE INTENSIFIER PDF

An InGaAs photocathode Image Intensifier is used to pass an amplified signal from a screen The InGaAs image intensification tube is optically coupled to an imaging device for passing output light. The output light from the InGaAs tube is transformed by an electronic circuit producing a desired signal output The signal output from the electronic circuit may be further enhanced into an enhanced signal output

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A shell of soft iron is disposed surrounding the magnet of the appendage pump for shielding the image intensifier tube from the stray magnetic field of the appendage pump. A coating of magnetic material on the envelope of the intensifier tube, in the region facing the pump, provides additional magnetic shielding for shielding the interior of the tube from the stray magnetic field of the pump to further improve the resolution of the image intensifier tube.

A clam shell shaped shield of soft iron was disposed surrounding the magnet of the appendage pump to shield the interior of the intensifier tube from the stray magnetic field produced by the magnet of the pump.

However, it was found that the shell of soft iron surrounding the pump was inadequate to reduce the stray magnetic field within the interior of the intensifier tube to an acceptable level. In a typical example, the magnet of the appendage pump produces a magnetic field of gauss within the pump. With the soft iron shielding shell in place, the stray field within the intensifier tube is reduced to a level of approximately five gauss. However, five gauss is generally an unacceptable level.

However, due to the relatively complex compound curves of the envelope in the region of the pump it was exceedingly difficult to form the sheet metal shielding material to the required configuration. As a result, imperfect shielding was obtained. Therefore, it is desired to obtain an improved method and apparatus for shielding image intensifier tubes which will allow the magnetic shielding material to conform exactly to the complex curves found on the exterior of the intensifier tube in the region of the appendage pump.

In another feature of the present invention, the exte- 1 rior of an evacuated electron tube is painted with a material which bonds to the envelope and which will form a particle binder coating. A quantity of magnetic particles are sprinkled onto the coating of binder material while the binder material is still wet to embed the magnetic particles in the coating to form a magnetic shield conforming exactly to the shape of the exterior surface of the tube.

In another feature of the present invention, a magnetic shielding coating is formed on the exterior of an evacuated electron tube by painting the exterior portion of the tube with a rubber based paint and embedding a quantity of magnetic particles in the rubber based paint while wet. The x-ray image converter screen 4 comprises an x-ray sensitive phosphor layer which converts the x-ray image into a photon image.

A photocathode layer is also includedin the screen 4 to receive the photon image and to convert same into an electron image which is emitter from the surface of the photocathode layer into the evacuated tube 2. The electron images are embodied in the stream of electrons emitted from the x-ray converter screen 4.

The stream of electrons is accelerated and focused by means of a series of convergent electrostatic focusing lens structures 5 through a hollow cylindrical anode electrode 6 onto a cathode illuminescent intensifier screen 7 which converts the electron image into an intensified photon image for viewing by an operator or for use by photodetector equipment, not shown. The evelope 2 is evacuated to a relatively low pressure, as of 10" torr, by means of an appendage magnetically confined glow discharge getter-ion vacuum pump 9 FIG.

The appendage vacuum pump9 is connected in gas communication with the envelope 2 via a pump tubulation 11, as of glass, see FIG. The pump tubulation 11 is generally of cylindrical configuration and closed at its outer end via a transverse end wall A collar 13 of magnetic material such as iron is bonded around the pump tubulation 11 to form one pole piece of the magnet structure of the appendage pump 9.

A hollow cylindrical magnet 14 see FIG. A disc of magnetic material, not shown, is disposed across the outer end of the magnet for fonn the second pole piece of the magnet. Anode and cathode pump electrodes are disposed within the exhaust tube The magnet structure produces an axial magnetic field of approximately gauss within the appendagepump for confining the glow discharge therein. A clamshell shield 15 of mild steel approximately 0.

A five gauss stray magnetic field within the image intensifier tube allows only a resolution in the intensified image of approximately 40 lines or wires per inch. This is generally unacceptable for high resolution applications and it is desired to reduce the stray magnetic field to values which are substantially lower than five gauss.

Accordingly, a coating of magnetic material 16, shown by cross hatching in FIG. The coating 16 extends part way up the exhaust tubulation The coating further shields the interior of the envelope 2 from the stray magnetic field of the appendage pump 9.

In a preferred embodiment, the coating of magnetic permeable material 16 is applied by painting the cross hatched portion of the envelope 2 with a first layer of a rubber based paint, such as Dow Corning type rubber paint dispersion coating. While the paint is still wet, iron particles of approximately 60 mesh or smaller are sprinkled onto the layer of rubber paint to embed the iron powder in the rubber coating.

Upon drying, the excess iron particles are dusted from the coating. Two additional layers of exactly the same configuration are successively painted onto the coated area 16 to an overall thickness of approximately 0. A final overcoat of rubber base paint is applied to improve the appearance of the coating.

The resultant magnetic shield coating 16 greatly reduces the intensity of the stray magnetic field within the tube. More particularly, the aforedescribed coating 16 reduced the stray magnetic field within the envelope 2 from five gauss to approximately 0.

The magnetic coating 16 of the present invention greatly facilitates magnetic shielding of the image intensifier tube as the coating exactly matches the compound curves of the glass surface of the envelope 2, thereby minimizing the possiblity of leakage of magnetic field around or through the shield. What is claimed is: 1. An evacuated electron tube comprising a nonmagnetic envelope containing anode and cathode electrode structures and a magnetically-permeable coating on at least a portion of said envelope for shielding an adjacent interior portion of said envelope from external magnetic fields, characterized in that said coating comprises a layer of a binder material on said portion of said envelope and a layer of magnetically-permeable particles embedded in the surface of said layer of binder material wherein said portion of said envelope has a plurality of said coatings formed thereover in successive layers, each coating comprising a layer of said binder material and a layer of said magnetically-permeable particles embedded in the surface of said layer of binder material, thereby to provide increased shielding for said tube.

The tube of claim 1 wherein each layer of binder material is a rubber-based paint and each layer of magnetically-permeable particles is iron. The tube of claim 1 further including a coating of binder material over said plurality of said coating. Q In claim 1, change lines 7 to 17 to read as follows: --characterized in that said covering comprises a plurality of coatings formed in succession over said portion of said envelope, each coating comprising a layer of a binder material and a layer of magneticallypermeable particles embedded in the surface of said layer of binder material, whereby said plurality of coatings provide increased shielding for said tube.

An evacuated electron tube comprising a non-magnetic envelope containing anode and cathode electrode structures and a magnetically-permeable coating on at least a portion of said envelope for shielding an adjacent interior portion of said envelope from external magnetic fields, characterized in that said covering comprises a plurality of coatings formed in succession over said portion of said envelope, each coating comprising a layer of a binder material and a layer of magnetically-permeable particles embedded in the surface of said layer of binder material, whereby said plurality of coatings provide increased shielding for said tube.

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Nirn We will not use cookies for any purpose other than the ones stated, but please note that we reserve the right to update our cookies. Proximity-focused intensifiers are free from geometrical distortion or shading because intenifier photoelectrons follow short, direct paths between the cathode, output screen, and the MCP rather than being focused by electrodes. Much, though not all, of the data collected is anonymous, though some of it is designed to detect browsing patterns and approximate geographical location to improve the visitor experience. If this is not your location, please select the correct region and country below.

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A shell of soft iron is disposed surrounding the magnet of the appendage pump for shielding the image intensifier tube from the stray magnetic field of the appendage pump. A coating of magnetic material on the envelope of the intensifier tube, in the region facing the pump, provides additional magnetic shielding for shielding the interior of the tube from the stray magnetic field of the pump to further improve the resolution of the image intensifier tube. A clam shell shaped shield of soft iron was disposed surrounding the magnet of the appendage pump to shield the interior of the intensifier tube from the stray magnetic field produced by the magnet of the pump. However, it was found that the shell of soft iron surrounding the pump was inadequate to reduce the stray magnetic field within the interior of the intensifier tube to an acceptable level.

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