US2727157A

US2727157A - Fluorescent tube

Info

Publication number: US2727157A
Application number: US262937A
Authority: US
Inventors: Richard L Longini
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1951-12-22
Filing date: 1951-12-22
Publication date: 1955-12-13
Anticipated expiration: 1972-12-13

Description

Dec. 13, 1955 R. L. LONGINI FLUORESCENT TUBE Filed Dec. 22. 1951 WITNESSES:

W D%--%%MM INVENTOR Richard L. Longini BY ATTORN EY United States Patent 0 FLUORESCENT TUBE Richard L. Longini, Forest Hiils, Pa, assignor to Westinghouse Electric Corporation, East Pittsburgh, P1, a corporation of Pennsyivania Appiication December 22, 1951, Serial No. 262,937

11 Claims. (Ci. 250-217) My invention relates to electron tubes and in particular relates to image pickup devices for television and similar purposes. Such devices comprise, in general, a photoelectric screen on which the light field to be transmitted is focused, arrangements which produce an electron field which corresponds in space distribution to the light field, :I?

a scanning means which produces a current which varies in time in the same way that the electron image varies in space, and some means for amplifying this current. Several different structural arrangements meeting these general requirements have been used from time to time, and in some of these, notably the most sensitive such as that called the Image Orthicon, all of the above-mentioned components are embodied within a single evacuated tube. The individual components are delicate and complex in operation, and each one must meet precise standfa tube unit can be accepted is reduced, and the cost of any tube unit which has to be rejected as faulty is reduced.

Another object of my invention is to provide a system in which certain of the functions heretofore performed by components of special form built into the composite structure may be carried out by separate tubes of standard types already developed and marketed at low price for other uses.

Another object of my invention is to provide a novel arrangement for carry ng out the function of translating the space distribution of a radiation field into time variation of a control current.

Other objects of my invention will become apparent to those skilled in the art upon reading the following description taken in connection with the drawings in which the single figure is a schematic diagram and elevational view partly in section of a picture pickup arrangement embodying my invention.

Referring in detm to the drawings, the picture pickup tube, which is here shown as a modified image orthicon, comprises an evacuated container 1 having a photoelectric screen 2 on its inside surface at one end on which the image of the view 3 to be transmitted is focused by a suitable optical system symbolized at 4. The electron image thus generated is accelerated by a grid electrode 5 into incidence with a thin screen 6 of glass or other suitable insulating material. A focusing coil symbolized by '77 may be provided to cause the electrons of the electron image to move in parallel lines parallel to the axis of the container 1, so that they strike screen 6 with the same distribution over the cross section of the image as they had in leaving the photoelectric surface 2 at which they originated. The potential of electrode 5 is so adice justed that each electron striking screen 6 causes the expulsion of one or more secondary electrons, and thus leaves a positive charge on the point where it struck the latter. The collective effect of all electrons striking screen 6 is therefore to impart to the various points on the latter positive charge distribution which is a replica of the electron distribution in the electron image, which in turn is, of course, a replica of the light field distribution on input screen 2. In short, screen 6 quickly acquires an electric-charge image which is a replica of the picture to be transmitted.

On the reverse side of screen 6 is incident a beam of electrons emanating from an electron gun 8 of a type too well known in the art to require detailed description here. This electron beam is caused to scan the glass screen 6 by some such means as deflecting coils 9. Its electron content is made great enough so that it is able, while moving over any point on screen 6, to neutralize the entire positive charge which has accumulated thereon, in the manner described above, during the time of one scanning cycle. Thus, when the spot on which the electron beam is incident at any instant is one with a high positive charge, most of the beam electrons will be absorbed by screen 6; but at another instant of the scanning when the beam is incident on a spot of little or no positive charge, few or no electrons will be abstracted from the beam.

In either event the beam electrons which are not absorbed by screen 6 will find their way to an annular collector electrode 11 from which they expel secondary electrons, and these are attracted by a suitable voltage impressed by a source 11A to a fluorescent screen 12 which they excite to luminescence which is proportional at any instant to the number of such non-abstracted beam electrons. The light flux from fluorescent screen 12 thus varies in time in the same way that the electric charge image on screen 6 varies in space; that is to say, light from fluorescent screen 12 varies in time in the same way as the light image on input screen 2 varies in space, point by point. The number of secondary electrons expelled from collector electrode 11 exceeds the number of incident electrons; hence, an amplifying action is produced.

A photomultiplier tube 13 is positioned with its photoelectric input screen closely adjacent the fluorescent screen 12. Such tubes are standard articles of commerce and need no description other than that electrons generated from their photoelectric input screens are multiplied by secondary emission from cascaded electrodes to produce an output current or" substantial volume proportional from instant to instant to the radiation flux striking their input screens. The RCA type 5819 sold by Radio Corporation of America, Rockefeller Center, New York, is one such tube. The fluorescent material on screen 12 may for example be zinc oxide and if the 5819 tube is used it may be desirable to insert a filter 14 to screen out the long persistence rays from screen 12, since the persistence of the fluorescent light after excitation should be no greater than the time taken by the electron beam to pass over a single point on screen 6. A type of photomultiplier tube which could be used without filter 14 would be one sensitive to ultra-violet but otherwise like the RCA type 5819.

While I have described my invention in connection with a modified form of 'unage orthicon, it may also be applied as a modified structure of any tube such as the image isocon and iconoscope which embodies an electron scanning beam from which electrons are abstracted in proportion to the brightness or" the picture element on which the beam is incident at any instant as it scans the picture point by point.

I claim as my invention:

1. A single vacuum-tight container enclosing a screen to generate and form an electron-image corresponding to a space-distributed radiation field, a continuous thin sheet of insulating material, means for projecting said electron image generated on said screen by said radiation field into, incidence with one side of said sheet, means to scan said sheet with an electron beam of cross section small compared to its area, a fluorescent screen in said container and means to bombard said fluorescent screen with electrons proportional to the remnant electrons of said beam not abstracted from said beam by the charge on said sheet at the point thereof which the scanning beam strikes at any instant.

2. A single vacuum-tight container enclosing; a photoelectric screen which emits electrons when irradiated; with a space-distributed radiation field, means for storing electric charges with a, space distribution corresponding' to. they electron image generated on said screen by said radiation field, means for projecting said electron image. onto one side ofsaid storing means, means to scan'the opposite side of said storing means with an electron beam of cross section small compared to the area of said storing means, means within said container to, produce radiation in response to electron bombardmerit, means for projecting electrons onto said radiation means. proportional at any instant to the remnant electrons not required to neutralize the charge on said storing, means at the point thereof on which said scanning beam isthen incident and means for projecting saidradia'tion through a wall of; said: container.

' 3. A picture-reproducing tube enclosing a photoelectric screen which emits electrons in response to radiations and. on which; a picture is to be focused, a continuous thin sheet of glass, means for accelerating an electron image generated on said screen by and corresponding tosaid picture into incidence upon said. sheet, toscan saidsheet with an electron beam of cross section small compared to the area of saidsheet, a fluorescent screen in said container and means to bombard.

said fluorescent screen with electrons proportional to the rcmnantelectronsof said, beam. not abstracted from said-, b eam by the charge on said, sheet at the point thereof which the scanning beam, strikes at any instant 4. A picture-reproducing tube enclosing a photoelecscreen which emits electrons in response to radiations andi on which a picture is to be focused, means for storing electric charges, means for projecting an electronimage generated by said screen onto one side of saidstoring means for forming a charge distribution thereon corresponding to said electron image generated on said screen by said picture, means to scan saidstor-.

ing means with an electron beam of cross section small compared to the area, of said charge-storing means, means. within said container, to produce. radiation in response to. electron bombardment, means for projecting electrons ontosaid radiation means to produce radiatiorr proportional atany instant. to the. remnant electrons not required; to neutralize the charge onsaid storing means at the. point'thereof on which said scanning beam isthenincident andmeans for projecting said radiation through a wall of said container.

5; A single vacuum-tight. container containing means for producing an electron image. with a space distributior1 v corresponding to that of a radiation field to be graphicallyportrayed, a thin glass. sheet, means-to project said imageinto incidence. upon one side of said sheet, means tofscanthe other side of said sheet with an electron bearn of cross. section small compared to the area of saidsheet, a fluorescent screen in said container and meansto bombardtsaid fluorescent. screen with electrons propoitional-to the remnant electrons. of saidbeam notabstracted from said beam by the charge on said sheet atthepoint thereof which the scanning-.beam.strikes at any instant.

6. In combination with a single.vacuum-tightcontainer enclosinga. photoelectric screen which emits electrons in response to radiation and which is irradiated with a spacedistributed radiation field, means for storing electric charges, means for projecting an electron image with a space distribution corresponding to the radiation field generated in said screen onto said storing means, means to scan said storing means with an electron beam of cross section small compared to the area of said storing means, means for generating radiations in response to electron bombardment, means for bombarding said radiation means with electrons proportional to the remnant electrons from said beam, means to project said radiation from said container which is proportional at any instant to said remnant electrons not required to neutralize the charge on said storing means at the point thereof on which said scanning beam is then incident and a photoelectric amplifier system positioned so that its photoelectric input screen is irradiated by said radiation from said container.

7. In combination with a picture-reproducing tube enclosing a photoelectric screen which emits electrons on which a picture is to be focused, means for storing electric charges, means for projecting an electron image corresponding to said picture onto one side of; said storing means with a space distribution corresponding to said.

electron image generated on said screen by said picture, means to scan the other side of said storing means with an electron beam of cross section small compared to. the area of said charge-storing means, means generating.- radiation from said container in response to electron bombardment, means for bombarding said radiation means with electrons proportional at any instant to the remnant electrons not required to neutralize the chargev on said storing means at the point thereof on whichsaid scanning beam is then incident and a photoelectric. amplifier system positioned so. that its photoelectric input screen is irradiated by said radiation from said container.

8, Incombination with a single vacuum-tight container enclosing a photoelectric screen which emits. electrons and which is irradiated; with a space-distributed radiationf eld, means for storing electric charges, means for projecting. the electron image generated by said screen.

into incidence with one side of said storing. means to obtain a charge pattern on said storing means with a space distribution correspondingv to the electron image generated on said screen by said radiation field, means to, scan said storing means with, an. electron beam of crosssection small; compared to the area, of said storing Ineans, means, to produce radiation in: response to.electron bombardment, means to bombard said. radiation producing means with the remnant electron from saidv beam, means to project radiation. from said container which is proportional atany instant tothe remnant electrons not required to neutralizethe charge on said storing means at the point thereof on which. said scanning beam is then incident; and;. a; photomultiplier tubepositioned to have its; input. screen irradiated bysaid radiation from said nta ner- 9, In; combination with a. picture-reproducing tubeenclosinga photoelectric screen which emits electrons and on which a picture is to be focused, means for storing electric charges, means for projecting. an electron image generated by said, screen, into incidence with one side of said; storing, means, the impingement of said electron imagesetting, upacharge image having a spacedistribution, corresponding to the electron image generated on said screen by said picture, means to scan the other side of said storing; means with an electron beamof cross section small; compared to the area of said charge-storingmeans,afiuorescent-screem means for projecting the remnantelectrons on said. fluorescent screen, means to Project radiation from said: fluorescent screen which is proportional atany instantv to the remnant electrons not required: to neutralize the charge on said storing means incident and aphotomultiplier tube positioned to have its input screen irradiated by light from said fluorescent screen.

10. A single vacuum-tight container enclosing an electron emissive photoelectric screen to be irradiated with a space-distributed radiation field, means for storing electric charges, means for projecting an electron image generated by said screen into incidence with one side of said storing means to form a space distribution charge pattern thereon corresponding to the electron image generated on said screen by said radiation field, means to scan the other side of said storing means with an electron beam of cross section small compared to the area of said storing means, a fluorescent screen in said container, means to bombard said fluorescent screen with electrons proportional to the remnant electrons of said beam not abstracted from said beam by the charge on said storing means at the point thereof which the scanning beam strikes at any instant, and means to make the number of said electrons bombarding said fluorescent screen greater than the number of said remnant electrons.

11. A picture-reproducing tube enclosing an electron emissive photoelectric screen on which a picture is to be focused, means for storing electric charges, means for projecting an electron image generated by said screen into incidence with one side of said storing means to form a space distribution charge pattern thereon corresponding to the electron image generated on said screen by said picture, means to scan said storing means with an electron beam of cross section small compared to the area of said charge-storing means, a fluorescent screen in said container and means to bombard said fluorescent screen with electrons proportional to the remnant electrons of said beam not abstracted from said beam by the charge on said storing means at the point thereof which the scanning beam strikes at any instant, and means to make the number of said electrons bombarding said fluorescent screen greater than the number of said remnant electrons.

References Cited in the file of this patent UNITED STATES PATENTS 2,149,487 Zilberman et a1. Mar. 7, 1939 2,248,977 Flory et al. July 15, 1941 2,277,246 McGee et al Mar. 24, 1942 2,288,766 Wolfi July 7, 1942 2,402,058 Loughren June 11, 1946 2,460,471 Schade Feb. 1, 1949 2,582,831 Hester Jan. 15, 1952 2,618,758 Cage Nov. 18, 1952