US2487665A - Image tube - Google Patents

Description

ET AL Nom 1949 G. A. MQRWN IMAGE TUBE Filed May 2, 19417 INVENTORS 620885 A. /Voera/v ;241/4 Eau/wa: BY

l TTORNEY Patented Nov. 8, 1949 UNITED STATES FATENT OFFICE IMAGE TUBE Application May 2, 1947, Serial No. '745,574

6 Claims. 1

This invention relates to electron devices for rendering objects visible in faintly lighted areas or in total darkness.

In prior art devices, such as disclosed in the co-pending application of Ruedy, Flory and Morton, filed October 5, 1946, Serial No. 701,588, the electrode structures have been held together inside a glass envelope by wires and glass beads. The electrodes have been made of very thin metal tubing to reduce the mass and minimize movement from the aligned positions by handling of the tubes. With this construction the points and sharp edges gave rise to cold emission when the overall voltage was around 5,000 volts. This construction also made it difiicult to maintain proper alignment and spacing between the electrodes while being mounted in the envelope, especially between the photocathode formed on the inside surface of the glass and the adjacent metal tubng electrode.

It is an object of this invention to provide a new type of image device that is free of sharp corners and edges to permit use of much higher voltages without cold emission taking place.

Another object of the invention is to mount the electrodes by a ring seal construction that gives a well aligned rigid structure of great stability.

Another object is to provide an image tube structure that uses a smaller fraction of the aperture of the electron lens near the cathode, thus reducing aberrations.

Another object of the invention is to simplify the electrode system of an image device and reduce the number of electrodes with no appreciable loss in resolution or image quality.

Other objects will appear in the following description, reference being had to the drawing in which the single figure -of the drawing is a longitudinal section of an image tube containing the invention.

Referring to the drawing, the tube comprises a transparent face plate of appropriate material such as glass for visible light and near infrared Waves or rock salt for far infra-red Waves. This lens may be somewhat conveX outwards as referred to in said co-pending application. A ring I' of metal film is formed on the inside surface of the disc near the periphery and the photosensitive coating 2 on the inside surface of the disc makes contact with this ring.

All metal parts are of substantial thickness. say tg of an inch, formed with well rounded and polished edges. One end of cathode cylinder 3 is sealed to the disc I in electrical contact with the metal film ring l' so that the potentials of this tubular electrode and the photocathode are the same. The rear half of the electrode 3 is of greater diameter than the first half. Glass tube ii is sealed to the larger end of electrode S at one of its ends and at its other end is sealed to the annular fiange 5 of the tubular electrode li which is of the same diameter as the small end of tubular electrode 3. A glass ring 'l is sealed to the fiange 5 and to a ring conductor 3, and glass ring 9 is sealed to ring 8 and to the fiange le of a shorter tubular electrode Il of lesser diameter than the tubular electrode 6. A glass tube 12 of diameter intermediate those of electrodes 5 and ll is sealed at one end to the fiange ll. The other end of glass tube 52 is sealed to the fiange 13 of tubular electrode lt which has an aperture disc ll near the end of glass tube E2 attached to the fiange ll). The electrodes ll and id are of substantially the same diameter. Glass disc lt is sealed to fiange l and its inner surface carries a fluorescent coating il. All the tubular electrodes and the tubular glass envelopes are coaxial.

One end of an arcuate conductor 25,3 is joined 7 to fiange 5 and its other end to the ring 8.

Silver material 2! on the conductor 25 is adapted to be vaporized by applying Voltage between fiange 5 and ring 8. An arcuate conductor 22, carrying caesium material 23, is joined at one end to fiange to and at the other end to ring 8,

In assembling the parts, the flat glass disc and the glass cylinder IZ are fusion sealed in a known way to the fiange |3 of anode lt. Fluorescent coating |1 is then deposited on the inside of disc 16 by settling or centrifuging it from an aqueous Suspension. This coating may be willemite or if higher efficiency is desired a phosphor such as zinc sulphoselenide may be used. When dried this is then coated with an electron permeable aluminum film (not shown) by known methods. At the high voltages used the latter phosphor even with the aluminum film is more eflicient than willemite, which would not be true if the lower voltages of prior art tubes are used. The fiange IO of anode ll is fusion sealed to the open end of glass envelope i2, a mandrel being used to secure accurate alignment and spacing of electrodes ll and M. This is important since the gap between the two electrodes forms the main electron lens of the tube. The glass ring 9, metal ring 8, glass ring l, fiange 5 and glass tube 4 are assembled in this order on fiange lt, using a mandrel to obtain accurate axial alignment and spacing of the parts after which they are fusion sealed together. Conductor 20 carrying silver bead 2| is now welded to fiange and ring 8, conductor 22 carrying caesium-bearing material 23 is welded to flange i and ring 8. The curved glass face-plate l is next fusion sealed to the small end of metal envelope 3 using a mandrel to keep the center of curvature of the face-plate accurately on the axis of the metal tube 3. The ring of metal film I' is then applied to make contact between the electrode 3 and the Sensitive photo-surface 2 applied as later referred to.

As a final step in the assembling of parts, the larger end of electrode 3 i's fusion sealed to the remaining end of glass tube 4 using an external jg to keep the parts 3 and 4 concentric and to maintain the proper gap between electrodes 3 and 6. The t'ube may now be exhausted at 24 and the silver material 2| vaporized to deposit silver at 2 on the inside of the face plate by applying voltage between fiange 5 and ring 8. The caesium material 23 is vaporized by applying voltage between flange lu and ring 8 to caesiate the silver coating in a well-known way.

Various voltages and electrode dimensions may be used but as an example the electrode 3 may be inch long with a diameter of 1% inches at the smaller end and a diameter of 1% inches at the larger end. This may 'have the voltage of the photocathode, that is, zero volts. The electrode 6 may be 1.039 inches long with a diameter of 1% inches and have a positive voltage of 2000 to 5000 above the cathode. The electrode ll may be .171 inch long and 3A in'ch in diameter. This may also 'have a positive voltage of 2000 to 5000 volts. nected to the same positive terminal. It is used only for a terminal for vaporizing the silver and caesium material and the dimensions are not important. The electrode |4 may be 21/4 inches long and its diameter inch. The voltage of this electrode may be 20,000 volts to 35,000 volts. The diaphragm ring 15 may be spa-ced .360 inch from the free end of electrode Ill and may have an opening with a diameter of 1A; inch. The distance between the free end of electrode 6 from the small end of electrode 3 may be .563 inch. The free end of electrode |4 may be spaced 1/8 inch from the plane of the flange Ill. With 20,000 volts on electrode 14, the voltage applied to electrodes 6 and Il with the above dimensions v may be varied between 2000 and 3000 in adjusting the focus of the electrons. To decrease pin cushion effect the glass face plate may be a section of a sphere of 2.375 inches radius. It will, of course, be understood that the voltages and dimensions of parts may be altered to fit particular cases.

While certain specific embodiments have been illustrated and described, it will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What we claim as new is:

l. An image device comprising a cathode cylinder, a plate transparent to radiant energy sealed across one end of said cylinder, a cathode on the inside surface of said plate in contact with said cylinder, a plurality of spaced anode cylinders each having an annular flange, said anode cylinders being place coaxially with the unflanged ends extending in the same direction, a transparent disc sealed across the end of the anode cylinder farthest from the photocathode, a fluorescent coating on said disc and an envelope of The ring 8 may be con- :z

insulating material sealed to said flanges and to the remaining end of said cathode cylinder.

2. An image device comprising a cathode cylinder, a plate transparent to radiant energy sealed across one end of said cylinder, a cathode on the inside surface of said plate in contact with said cylinder, a plurality of spaced anode cylinders each having an annular fiange at one end, the other ends extending towards said cathode, a disc transparent to light sealed across the flanged end of the anode cylinder farthest from said cathode, a fluorescent coating on the inner surface of said disc, glass tubing sealed between the flange of the anode cylinder nearest said photocathode and the remaining end of said cathode cylinder and glass tubing sealed between each flange and the succeeding flange whereby all said anode cylinders are supported by their flanges.

3. An image device comprising a cathode cylinder, a glass face plate sealed across one end of said cylinder, a cathode one the inner surface of said face plate in contact with said cylinder, a first anode having an annular flange at one end, the other end extending toward said cathode, a glass tube sealed between the remaining end of said cathode cylinder and said flange, a second anode cylinder of lesser diameter than the first anode cylinder having an annular flange at one end, the other end extending toward the first anode cylinder, two glass rings and a metal washer sealed between said flanges, a third anode cylinder of substantially the same diameter as the second anode cylinder having an annular flange at one end, the other end extending toward and adjacent to the flanged end of the second anode cylinder, a glass tube sealed between the last mentioned two flanges, a disc transparent to light sealed across the flanged end of the third anode and a fiuorescent coating on the inside of said disc.

4. An image device comprising a cathode cylinder, a plate transparent to radiant energy sealed across one end of said cylinder, a cathode on the inside surface of said plate in contact with said cylinder, a plurality of spaced anode cylinders each having an annular flange at one end, the other ends extending towards said photocathode, all said cylinders being coaxial and free of exposed sharp edges, a transparent disc sealed across the fianged end of the anode cylinder farthest from the photocathode and a fluorescent coating on said disc and an envelope of insulating material sealed to said fianges and to the remaining end of said cathode cylinder. i

5. An image device comprising a .cathode cylinder, a plate transparent to radiant energy sealed across one end of said cylinder, said plate having surfaces of revolution convex outwards of the device with Centers in the axis of said cylinder, a cathode on the inside surface of said plate in contact with said cylinder, a plurality of spaced anode cylinders coaxial with the first cylinder, each having an annular flange at one end, the other ends extending towards said cathode, a disc transparent to light sealed across the flanged end of the anode cylinder farthest from said cathode, a fiuorescent coating on the inner surface of said disc, glass tubing sealed between the end of the anode cylinder nearest said photocathode and the remaining end of said cathode cylinder and glass tubing sealed between each flange and the succeeding flange whereby all said anode cylinders are supported by their flanges.

6. An image device comprising a cathode cylinder having a portion of larger diameter than the remaining portion, said portions being joined by a flange with rounded edges, a glass face plate sealed across the smaller end of said cylinder having surfaces of revolution convex outwards of the device with centers in the axis of said cathode cylinder, a cathode on the inner surface of said face plate in contact with said cylinder, a first anode having an annular fiange at one end, the other end extending toward said 'cathode, a glass tube sealed between the remaining end of said cathode cylinder and said flange, a second anode cylinder of lesser diameter than the first anode cylinder having an annular fiange at one end, the other end extending toward the first anode cylinder, two glass rings and a metal washer sealed between said fianges, a third anode cylinder of substantially the same diameter as the second anode cylinder having an annular fiange at one end, the other end extending toward and adjacent to the flanged end of the second anode cylinder, a glass tube sealed between the last mentioned two fianges, all said anode cylinders being coaxial with said cathode cylinder and having rounded edges, a disc transparent to light sealed across the fianged end of the third anode and a fluorescent coating on the inside of said disc.

GEORGE A. MORTON.

PAUL RUDNICK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,945,979 Parker Feb. 6, 1934 2,189,320 Morton Feb. 6, 1940 Certificate of Correcton Patent No. 2,487,665 November 8, 1949 GEORGE A. MORTON ET AL.

It is hereby eertified that errors appear in the printed speeification of the above numbered patent requiring correetion as follows:

Column 3, line 71, for the word uplace read placed; column 4, line 21, for one the read on the;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 30th day of May, A. D. 1950.

[sun] THOMAS MURPHY,

A88z'8tant Oommz'esz'oner of Patents.

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