Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1990-12-11
1992-11-17
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
313532, H01J 3150
Patent
active
051645823
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for operating an image intensifier tube provided with a channel plate, which image intensifier tube has a cathode window which transmits the radiation to be intensified, a cathode fitted inside the tube which is capable of emitting electrons when exposed to radiation transmitted through the cathode window; an anode fitted opposite the cathode which is capable of forming a light image when exposed to incident electrons, an electric field being generated between the cathode and the anode such that electrons emitted by the cathode travel towards the anode, and a channel plate being placed between the cathode and the anode which exhibits secondary emission when exposed to incident electrons.
The invention furthermore relates to an image intensifier tube device provided with a channel plate.
An image intensifier tube having a channel plate is generally known, as is the manner in which such an image intensifier tube can be operated in practice. The channel plate is often denoted by the abbreviation MCP (Multi-Channel Plate).
A problem which has already been known for a very long time and which arises in the case of image intensifier tubes is that ions are produced in the tubes during operation, for example as a result of collisions between electrons and gas molecules which are still left behind in the tube and/or diffused out of materials present in the tube. Ions may also sometimes be produced by collisions between electrons and solid material in an image intensifier tube.
Such ions are positively charged and therefore travel towards the cathode under the influence of the electric field present between cathode and anode. The incidence of such ions on the cathode has an unfavourable effect on the operation of the cathode. It is in fact said that the cathode undergoes damage.
In an image intensifier tube provided with a channel plate, the undesirable ions are essentially produced in the channel plate. In order to prevent said ions reaching the cathode, according to a known technique the channel plate is equipped with a very thin membrane of a suitable material on the side facing the cathode. The membrane has a thickness such that electrons emitted by the cathode are able to penetrate through the membrane, but ions are held back by the membrane. In practice, the membrane has a thickness of the order of a few tens of .ANG.Angstroms.
The fitting of an ion-repelling membrane on a channel plate is fairly complicated and consequently considerably increases the cost price. Furthermore, such a membrane is very vulnerable and has a negative effect on the signal
oise ratio of the image intensifier tube.
The object of the invention is to provide a method which renders the use of an ion-repelling membrane superfluous and also an image intensifier tube device in which a channel plate not having an ion-repelling membrane is used without there being a risk of the cathode being poisoned.
To this end, according to the invention, a method of the type described is characterized in that a high-frequency alternating electric field is generated in the space between the cathode and the channel plate.
An image intensifier tube device comprising at least one image intensifier tube provided with a channel plate situated between a cathode and an anode, and also a high-voltage supply device for providing the supply voltages needed for operating the image intensifier tube is characterized, according to the invention, in that the high-voltage supply device comprises a high-frequency alternating voltage source which is connected between a point carrying a reference potential and the cathode.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a schematic illustration of the present invention.
The invention is explained in more detail below with reference to the accompanying drawing.
The sole figure shows diagrammatically an image intensifier tube device comprising a housing 1 and a high-voltage supply device 2. The housing 1 has a cathode window 3 which, in this example, supports, on the inside, a cathode 4 whi
REFERENCES:
patent: 3564260 (1971-02-01), Tanaka et al.
patent: 3675028 (1972-07-01), Grant
patent: 3870917 (1975-03-01), Cuny
patent: 4134009 (1979-01-01), Dippold
patent: 4691099 (1987-09-01), Johnson
patent: 4882481 (1989-11-01), Gilligan et al.
patent: 4891581 (1990-01-01), Takiguchi
patent: 4926039 (1990-05-01), Garfield et al.
patent: 4948952 (1990-08-01), Guyot
Soviet Inventions Illustrated, vol. 84, No. 2, Abstract No. 84-125809/20, SU 1035-680-A, Jun. 1964.
B.V. Optische Industrie "De Oude Delft"
Marn Louis E.
Messinger Michael
Nelms David C.
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