US2200166A - Image analyzing and dissecting tube - Google Patents

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Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
  • H01J29/023—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof secondary-electron emitting electrode arrangements

Definitions

• My invention relates to image analyzing and dissecting tubes, and more particularly to such a device embodying an electron multiplier in order that the output from the device may be 'increased.
• My invention embodies, with the exception of the multiplier, the general structure of the Farnsworth image analysis tube, as describedfL-by him in United States Patent No. 1,773,980, issued August 26, 1930, and also embodies the same general type of multiplier as described and claimed by Snyder in his application, Serial No. 149,654, filed June 22, 1937, for a Box element multiplier, now Patent No. 2,163,966, issued June 27, 1939.
• an image analysis tube suitable for television or like purposes, wherein an electron image may be analyzed into elementary components and the components thereafter amplified within the tube by the use of an electron multiplier; to provide an image analysis tube having embodied therein an electron multiplier of smallv size; to provide an image analysis tube having a photoelectric cathode and an electron multiplier together with means whereby the cathode and the multiplier may be separately sensitized; to provide an image analysis tube embodying a direct-current electron multiplier of small size; to provide an image analysis tube wherein a direct-current multiplier is utilized, and wherein the direct-'current multiplier is of such small sizel that it can be placed in the path of the optical image to be analyzed without obstructing sufficient light to destroy the efficient action of the device; to provide a target finger for a dissector tube containing an electron multiplier of small size; and to provide a highly efficient and highgain image analysis tube.
• an optical image is focused by proper lens system through a transparent envelope Wall onto a solid photoelectric cathode. Electrons are emitted from the photoelectric surface of this cathode in proportion to the light intensity falling upon each elementary area thereof.
• a hollow tubular anode is provided to Withdraw the emitted photoelectrons from the vicinity of the cathode as an electron image, and this anode is usually provided with an aperture through which only one elementary area of the electron image can pass through the anode.
• any collecting device placed bacli of the anode aperture will receive thereon electrons varying in number with respect to time, and representing, after a complete scansion, a train of television signals, each signal representing the light intensity of the area from whence they came.
• the photoelectric cathode be covered with a material of high work function such as, for example, metallic caesium distilled upon silver oxide, the number of electrons per elementary area will be relatively few, and that unless precautions are 'taken to multiply the electrons, the signal current will be relatively weak as it emerges from the analysis tube envelope. If it-is weak, then a sensitive and powerful external amplifier will be necessary to increase the strength of the train before it can be utilized for transmission and reception to a distant point.
• a material of high work function such as, for example, metallic caesium distilled upon silver oxide
• the photoelectric cathode in the tube of my invention is open to the main chamber of the tube, whereas the electron multiplier is contained within the anode finger.
• FIG. 1 is a longitudinal sectional view of a tube of my invention, with certain auxiliary apparatus shown diagrammatically;
• Fig. 2 is an enlarged longitudinal sectional view of the anode nger embodying -a preferred electron multiplier
• Fig. 3 is a diagram showing how the various electrodes may be energized for operation.
• Fig. 4 is a cross-sectional view of the anode finger taken in the plane of the scanning aperture.
• Fig. l which represents schematically a television dissector tube
• an envelope I is provided With a cathode 2 at one end thereof, the opposite end 3 being transparent and preferably in the form of a planar window so that an optical image, as represented by the optical path lines 4, may be projected on cathode 2 :by an outside lens or equivalent optical system 5.
• an anode finger assembly comprising a hollow conductive tube 6, preferably having a square section. This tube is made sufficiently small in diameter so that it does not appreciably distort the optical image. Inasmuch as it is not in the focus of the lens system, its only action is to reduce the over-all light on cathode 2.
• the tube 6 is maintained in position by having one open end thereof slipped over a reentrant stem 'I carrying the multiplier leads, as will be explained later, and the other open end is fixed by entering an envelope side arm 9, this latter side arm being provided with a tubulation I0.
• This latter side arm being provided with a tubulation I0.
• the main envelope I is provided with a second tubulation II, this being positioned at one side of tube I0 and opening directly toward cathode 2 without obstruction.
• the anode tube 6 is provided with a primary scanning aperture
• a secondary scanning aperture I5 also axially positioned with respect to envelope and cathode.
• first multiplier element 20 in the form of a box having a flat side facing secondary aperture I5, and provided with a tertiary scanning aperture 2
• the primary, secondary, and tertiary apertures are concentric and in alignment, and diminish in size, tertiary aperture 2
• ! is curved, and the side at right angles to the one carrying aperture 2
• the open side oi' second element 22 opens to the screened side 25 of multiplier element 26, and the same construction and position holds with the fourth multiplier element 21 and the fifth multiplier element 29.
• Parallel to the open side of the fifth multiplier element 29 is an output screen 30 backed by iinal multiplier element 3
• the tube After the tube has been assembled it is preferably exhausted through an exhaust-tubulation 32, and inasmuch as it is advantageous in many instances to process the multiplier elements for maximum secondary emission, and the cathode 2 for kmaximum photoelectric emission, tubulations II) and II are therefore connected to different sources of metallic vapor.
• the most sensitive photoelectric surfaces are produced by evaporating caesium vapor onto an oxidized silver surface.
• the cathode 2 is preferably made of silver; the surface facing the anode finger is etched and oxidized, and then caesium vapor is admitted through tubulation so that the vapor may have an unrestricted path to settle and condense upon cathode 2.
• the optical image falling on cathode 2 produces an electron image which is drawn toward anode finger 6, and the electrons are maintained in electron image array by means of a longitudinal magnetic field provided by focusing coil 49.
• This focusing coil is energized, preferably, by a source of direct current 4I.
• the electron image is moved in two directions across aperture I2, and, consequently, across apertures I5 and 2
• the secondaries produced by impacting the nal multiplier element 3l are collected by collection screen 3U, which is at the highest positive potential, and which is connected to source 50 through an output resistor 5I, andthe output may be then taxen directly from the output electrode 30 through output condenser 52.
• Multiplications of several thousand are readily obtained with this type of structure, and it is obvious that the multiplication taking place within the tube greatly enhances the sensitivity and the final output of the dissector tube itself, and thus allows a reduction in sensitivity of the outside ampliiiers usually necessary in order to bring the train of television signals up to a usable amplitude.
• An image dissector tube having an envelope including a transparent window through which an optical image may be projected onto a photoelectric cathode positioned within said envelope image, and means for collecting and amplifying photo-electrons emitted from said cathode comprising a hollow conductive tube extending across the projection path of said opticalv image and positioned at a point between said window and said cathode, said tube having a recess therein facing said cathode and the bottom of said recess having an aperture therein, a hollow body positioned in said tube back of said aperture and having therein a second aperture registering with but apart from said rst aperture, a surface capable of emitting secondary electrons upon electron impact therewith at a ratio greater than unity carried by said body and in line with said apertures, and a plurality of additional and similar surfaces within said tube and located to be serially impacted by electrons leaving said rst surface and passing Athrough said aperture, said conductive tube shielding said additional secondary electron emitting surfaces from all other electrons leaving said photo
• An image dissector tube having an envelope including a transparent window through which an optical image may be projected onto a photoelectric cathode positioned within said envelope, and means for collecting and amplifying photo electrons emitted from said cathode comprising a hollow conductive tube extending across the projection path of said optical image and positioned at a point between said window and said cathode, said tube having a recess therein facing said cathode and the bottom of said recess having an aperture therein, an electron multiplier within said tube having a plurality of surfaces located to be serially impacted by electrons passing through said aperture, an envelope tubulation positioned to direct vapor of a photoelectric material toward said cathode.

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• Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)

Description

Priority Applications (1)

Applications Claiming Priority (1)

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Cited By (4)

• 1937
  • 1937-08-17 US US159492A patent/US2200166A/en not_active Expired - Lifetime

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