US3619685A

US3619685A - Photoconductive pickup tube with unitized electrode structure having the photoconductive target electrode spaced from the tube faceplate

Info

Publication number: US3619685A
Application number: US11616A
Authority: US
Inventors: John J Miller; Carl W Penird
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-02-16
Filing date: 1970-02-16
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

A photoconductive pickup tube utilizes a one-piece envelope, with a closed-end faceplate portion, wherein a unitized mount structure is positioned. The integrated mount includes a beam forming portion with a mesh electrode oriented relative to the frontal end thereof. The unitized array continues whereof a target substrate, having a photoconductive target electrode formed thereon, is insulatively spaced from the mesh electrode. Resilient means are terminally employed to space the target substrate from the interior surface of the envelope faceplate, and a connective means for the target electrode is extended in an insulated manner along the mount to emerge from the base portion of the envelope.

Description

United fitates Fate [72] Inventors JohnJ.Miller 5/1966 Shallcross 313/65 A lv=: w I N 3,256,455 6/l966 Saldi 313/65 A at enlrd, ater 00, both of .Y. Pri Examiner Roy Lake [21] Appl. No. 11,616 3 Assistant Exammer-V. Lafranchi [22] Filed Feb. 16,1970 A l D d C [45] Patented Nov. 9, 1971 lt0rneys -Norman J. Mal ey, onal R. astle and Frederick H. Rinn [54] PHOTOCONDUCTIVE PICKUP TUBE WITH UNITIZED ELECTRODE STRUCTURE HAVING THE PHOTOCONDUCTIV E TARGET ELECTRODE SPACE!) FROM THE TUBE FACEPLATE 9 Claims 5 Drawing Figs. A BSTRACT: A photoconductive pickup tube utilizes a onepiece envelope, with a closed-end faceplate portion, wherein a [52] US. Cl 313/65 A, iti d mount Structure i iti d Th i t t d mount 313/268, 313/269, 31.3/285 includes a beam forming portion with a mesh electrode [5 l 1 Int. T. oriented relative to the frontal end thereof The uniflzgd array 1/92, 19/46, 31/26 continues whereof a target substrate, having a photoconduc- Fleld of Search five tar et electrode formed thereon is insulatiyely spaced 65 65 282, 234, 285, 268 from the mesh electrode. Resilient means are terminally employed to space the target substrate from the interior surface [56] References cued of the envelope faceplate, and a connective means for the tar- UNITED STATES PATENTS get electrode is extended in an insulated manner along the 3,202,857 8/1965 Antoniades 313 /65 A mount to emerge from the base portion of the envelope 17' l 4 2 f l 3 3 2 a /V I I/r 3 3 47 4- m/ 6| 5 1 '1 32 39 l 27 114mm II 65 r '1 26 65 '-l i I l 65 l I I I5 PATENTEU 9 3,6193 8 5 SHEET 1 OF 2 INVENTORS. JOHN J. MILLER 8. By CARL W. PENIRD jD O E- ATTORNEY PATENTEDuuv 9 I97] SHEET 2 BF 2 INVENTORS. JOHN J.M|LLER 8.

CARL W. PENIRD ATTORNEY PHOTOCONDUCTIVE PICKUP TUBE WITH UN ITIZED ELECTRODE STRUCTURE HAVING THE PHOTOCONDUCTIVE TARGET ELECTRODE SPACED FROM THE TUBE FACEPLATE BACKGROUND OF THE INVENTION This invention relates to cathode-ray tubes and more particularly to a photoconductive pickup tube of the type utilized in television camera applications and a method of fabricating the same.

Many of the photoconductive tubes conventionally utilized in television applications are normally relatively complicated structures, and as such are not readily conducive to expeditious methods of fabrication. It was found extremely difficult to consistently form photoconductive target electrodes on the face areas of closed end tubes and make satisfactory electrical connections thereto. In view of this difficulty, it has been common practice to construct pickup tubes having the photoconductive target electrode disposed on the inner surface of a separate glass faceplate which is then usually indium-sealed to an open envelope portion. It has been conventional practice to utilize the indium seal as a means for effecting an external connection for the target electrode. Such seals were found to be expensive, first, in view of the cost of the indium material seal, and second, because of the special treatment that must be given the glass to insure hennetic tightness.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide a photoconductive pickup tube of a structure that can be expeditiously and inexpensively fabricated.

Another object is to provide a pickup tube wherein the target electrode is not directly associated with the faceplate of the tube.

A further object is to provide a method of fabricating a pickup tube by considering the internal tube structure as a wholly separate construction.

The foregoing objects are achieved in one aspect of the invention by providing a pickup tube employing a one-piece envelope having a closed end faceplate wherein a stacked array of related elements is positioned as a unitized mount structure. The integrated array in the unitized mount includes a basic multielectrode beam forming structure, upon which a mesh electrode is oriented relative to the frontal open end thereof. Spaced from the mesh electrode, by insulative spacer means, is a transparent target substrate having a photoconductive target electrode formed on the rear surface facing the mesh electrode. Relative to the front surface of the target substrate are terminal spacing means peripherally and longitudinally oriented to provide resilient spacing between the target substrate and the interior surface of the envelope faceplate. Target electrode connective means are extended longitudinally in an insulated manner along the mount structure to emerge from base portion of the envelope. The aforedescribed photoconductive pickup tube utilizing the unitized mount construction and one-piece envelope concepts can be expeditiously and economically fabricated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a photoconductive tube incorporating the concepts of the invention;

FIG. 2 is an enlarged cross section of the forward portion of the tube detailing aspects of the invention as viewed relative to the line 2-2 of FIG. 3;

FIG. 3 is a plan view showing the end of the mount structure taken along the line 3-3 of FIG. 2;

FIG. 4 is an enlarged cross section of the forward portion of the tube illustrating another embodiment of the invention; and

F IG. 5 is a perspective illustrating an alternate embodiment of the terminal spacing means.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings.

The term one-piece envelope" as used herein is intended to include a bulb structure wherein the closed end or faceplate portion is:

l. a continuation of the same glass comprising the envelope sidewall; or

2. of different glass than that of the envelope sidewall but expansively compatible therewith.

With reference to the drawings, there is shown in FIG. 1 a photoconductive pickup tube 11 having a one-piece evacuated envelope 13 which comprises a wall portion 15, an integral closed end faceplate portion 17, and an opposed base closure portion 19. Positioned therein is a unitized internal mount construction 21 which is supported by the base portion 19 and comprises a multielectrode electron beam forming structure of which only a substantially tubular control electrode 23 is shown. A plurality of electrical connective means 22 are arranged to extend exteriorly from the internal mount structure 21 through the base portion 19. A substantially planar mesh electrode 25 is supported relative to and parallel with the open frontal end of the control electrode 23. Spaced from the mesh electrode 25, by spacer means 27, is a substantially transparent planar target substrate 29 which is supported by an annular support means 33. A photoconductive signal or target electrode 41 is suitably formed on the rear surface of the substrate 29 facing the mesh electrode 25. An electrical connection 45 for the target electrode 41 is formed and disposed to extend longitudinally in an insulated manner along the mount structure 21, in the space between the control electrode 23 and the envelope wall portion 15, to emerge from the base portion 19 as an external connection 45'. Extending longitudinally beyond the target substrate 29 are terminal spacing means 49 which are disposed in a peripheral manner to provide substantially resilient spacing between the target substrate and the interior surface of the envelope faceplate 17. A longitudinal axis 55 extends through the one-piece envelope l3 and the encompassed internal unitized mount structure 21. At least three resilient spaced-apart positioners 56 are employed to effect lateral support and positioning of the mount structure 21 within the envelope 13.

In operation, light rays 57 from external imagery are focused on the photoconductive target electrode 41 by camera lens means 59. In the pickup tube 11 of this invention, the light rays 57', that have passed through the lens 59, are directed to traverse the tube faceplate portion 17 in an unfocused condition. As such, the optical quality of the glass comprising at least the central portion 17' of the faceplate 17 should be substantially free of optical distortion but need not be as critical as the quality of the glass of the target substrate 29 which is contiguous to the plane of focus on the target electrode 41. Utilization of the foregoing optical considerations plus the orientation of the target electrode connection through the base portion makes the one-piece envelope concept a feasible and advantageous construction.

With reference to FIGS. 1, 2, and 3, the structure and fabrication of one embodiment of the pickup tube 11 of the invention will be described in greater detail.

The substantially transparent planar target substrate 29 is of distortion free glass, such as one of the clear borosilieates, having smooth front and rear surfaces, 30 and 31 respectively. On the rear surface 31, a substantially uniform and transparent electrically conductive coating 32 is formed in a conventional manner, such as by heating the substrate and spraying substantially the whole of the rear surface 31 with stannic chloride to form conductive tin oxide. The conductively coated substrate 29 is then positioned in the female section 35 of the substrate annular support means 33 in a manner that the electrically conductive coating 32 makes contact with an instanding ledge or shelf 37 of the female support section 35. With the substrate so positioned, a photoconductive material 39, such as for example antimony trisulfide, is suitably vaporized over the exposed coating of tin oxide 32 to form the target electrode 41. A metallic male section 42 of the annular support means 33, having resilient terminal spacing means 49 positioned and attached thereto, is then inserted into the female support section 35 to substantially peripherally seat upon the uncoated front surface of the substrate. The male section 42 has a peripheral wall 43 which makes engagement with the peripheral wall 36 of the female section 35. The two sections and 42 of the annular support means 33 are then bonded together such as by welding the peripheral wall 36 to the wall 43 to form an electrically conductive and supported target electrode structure 47.

The mesh electrode 25 is a planar foraminous screen which, depending upon the resolution desired in the tube, may have from 500 to 1,000 apertures per inch. This mesh screen is supported by a flanged support ring 26 which, as shown in FIG. 2, is positioned on and bonded to the open frontal end of the control electrode 23 of the electron beam forming structure.

Target spacer means 27, in the form of an insulative ring circumferentially dimensioned to have an opening at least substantially equaling the functional area of the mesh electrode 25, is peripherally positioned between the mesh electrode 25 and the target or signal electrode structure 47 to provide a stacked array of cooperating elements. it has been found that the target spacer 27 can be suitably formed from ceramic or glass. A target electrode connective lead 45 is terminally formed to facilitate bonding attachment to the target electrode structure 47 in a manner to function as both an electrical connection and support means therefor. The connective lead 45 extends along the control electrode 23 encased in an insulator or standoff 24 which is attached to the mount structure by clamping means 65. At least one target electrode structure support 61, spaced from the connective lead 45, is also bonded to the target electrode structure 47. As shown in FIGS. 2 and 3, three of such structure supports 61 are insulativel'y attached to the exterior wall of the control electrode 23 by insulators 63 and welded clamping means 65. Thus, by the bonded electrode connective lead 45 and one or more of the structure supports 61, a stacked unitized mount structure 21 is provided.

Reference is again made to the terminal spacing means 49. As shown in FIGS. 2 and 3, three substantially S-shaped resilient metallic elements or snubbers, referenced as 49, are spacedly positioned and bonded to an instanding ledge or shelf 51 of the male support section 42. These snubbers 49 are formed to extend beyond the target electrode structure 47 in a manner to contact the periphery of the envelope faceplate portion 17. The S-shaped resilient elements are not to be considered limiting as other configurations can function in a similar manner. For example, a metailic wiggle-washer 49 as shown in FIG. 5, is vertically formed to seat on the instanding ledge 51 and provide the required terminal resilient spacing. This washer 49 may or may not be bonded to the ledge 51 and is circumferentially dimensioned to have an opening at least substantially equaling the functional area of the target photoconductive material 39.

Another embodiment of the forward end of the unitized mount structure 21 is shown in FIG. 4 wherein the mesh electrode 25' is electrically isolated from both the control electrode 23 and the target electrode 41. In certain types of pickup tubes such isolation is desired. This is accomplished by positioning the mesh electrode 25 between the aforedescribed annular target spacer means 27 and a control electrode annuiar insulative spacer 71, which is formed in a manner similar to target spacer means 27 and seated on the open end of the beam control electrode 23. The insulated mesh electrode 25 may have a separate electrical connection 73 attached thereto and formed to extend longitudinally, encased in an insulator 75 attached to the control electrode 23, within the envelope in a manner to emerge outwardly through the base portion 19.

As in the first embodiment, the second embodiment is likewise supported and unitized by the target electrode connective lead 45' and at least two target electrode structure supports 61.

Upon being unitized, either mount structure is then inserted within the one-piece glass envelope in a manner that the resilient terminal spacing means 49, 49' makes seated peripheral engagement with the inner surface of the closed end faceplate portion 17. It has been found that a clear soft lime glass is satisfactory material for the one-piece envelope construction.

White the terminal spacing means 49 of the unitized amount structure 21 are maintained in resilient engagement with the faceplate portion 17, base closure portion 19 is joined to the envelope 13 as by a conventional drop-seal technique to provide a glass enclosed structure. Subsequent gas evacuation, hermetic sealing, and tube processing of the glass enclosed structure provides the completed photoconductive pickup tube 11.

It is within the scope of the invention to rearrange certain of the fabrication steps as may be deemed conducive to efficient manufacturing procedure.

Thus, a pickup tube structure is provided that can be expeditiously and inexpensively fabricated. By utilizing unitized mount construction, separate faceplate seals are eliminated, and all electrical connections are feasibly effected through the base. By removing the target electrode from the faceplate, the optical quality of the faceplate is less critical to the application. Therefore, less expensive envelopes are employed, and the number of fabrication steps are reduced.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

We claim:

1. A photoconductive pickup tube formed of a glass envelope having a wall portion, a closed end faceplate portion of similar material and an opposed base closure portion providing a hermetic enclosure having a longitudinal axis wherein the internal tube construction is a stacked unit comprising:

a multielectrode beam forming structure having an extending substantially tubular control electrode with a mesh electrode member supported relative to and parallel with the open frontal end of said tubular control electrode, said multielectrode beam forming structure having an axis substantially coincidental with said longitudinal axis of said envelope;

a substantially transparent planar target substrate having front and rear surfaces positioned within said glass envelope in a manner spaced from said faceplate and adjacent to said mesh electrode;

a photoconductive target electrode disposed on the rear surface of said substrate facing said mesh electrode;

a target connection for said photoconductive target electrode formed to extend longitudinally in an insulative manner within said envelope;

target spacer means positioned between said mesh electrode and said target substrate;

provisions for Supporting said target substrate relative to said control electrode;

terminal spacing means extending longitudinally beyond said substrate and peripheraily contiguous thereto in a manner to provide substantially resilient spacing between said substrate and the interior surface of said envelope faceplate, and

a plurality of electrical connective means including said target connection arranged to extend from said internal tube structure through the base portion of said envelope.

2. A photoconductive pickup tube according to claim 1 wherein said target connection is formed as an insulated lead oriented in the space between said control electrode and said envelope wall portion in a manner to extend therealong from said target to said base portion.

3. A photoconductive pickup tube according to claim 1 wherein said target spacer is in the form of an insulative ring circumferentially dimensioned to have an opening at least substantially equaling the functional area of said mesh electrode.

4. A photoconductive pickup tube according to claim 3 wherein said target spacer is formed of glass.

5. A photoconductive pickup tube according to claim 1 wherein said terminal spacing means is in the fonn of a resilient ring circumferentially dimensioned to have an opening at least substantially equaling the functional area of said target photoconductive material.

6. A photoconductive pickup tube according to claim 1 wherein said terminal spacing means is in the form of at least three spaced-apart substantially resilient snubbers extending beyond said target substrate in a manner to contact the periphery of said envelope faceplate portion.

7. A photoconductive pickup tube according to claim 1 wherein the glass envelope is of soft glass material whereof at least the central area of the closed end portion is substantially free of optical distortion.

8. A photoconductive pickup tube according to claim 1 wherein said mesh electrode is insulated from said tubular control electrode.

9. A photoconductive pickup tube according to claim 8 wherein said insulated mesh electrode has a separate electrical connection formed to extend longitudinally within said envelope and through said base portion.

Claims

1. A photoconductive pickup tube formed of a glass envelope having a wall portion, a closed end faceplate portion of similar material and an opposed base closure portion providing a hermetic enclosure having a longitudinal axis wherein the internal tube construction is a stacked unit comprising: a multielectrode beam forming structure having an extending substantially tubular control electrode with a mesh electrode member supported relative to and parallel with the open frontal end of saId tubular control electrode, said multielectrode beam forming structure having an axis substantially coincidental with said longitudinal axis of said envelope; a substantially transparent planar target substrate having front and rear surfaces positioned within said glass envelope in a manner spaced from said faceplate and adjacent to said mesh electrode; a photoconductive target electrode disposed on the rear surface of said substrate facing said mesh electrode; a target connection for said photoconductive target electrode formed to extend longitudinally in an insulative manner within said envelope; target spacer means positioned between said mesh electrode and said target substrate; provisions for supporting said target substrate relative to said control electrode; terminal spacing means extending longitudinally beyond said substrate and peripherally contiguous thereto in a manner to provide substantially resilient spacing between said substrate and the interior surface of said envelope faceplate, and a plurality of electrical connective means including said target connection arranged to extend from said internal tube structure through the base portion of said envelope.

5. A photoconductive pickup tube according to claim 1 wherein said terminal spacing means is in the form of a resilient ring circumferentially dimensioned to have an opening at least substantially equalling the functional area of said target photoconductive material.