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Publication numberUS3912962 A
Publication typeGrant
Publication dateOct 14, 1975
Filing dateMar 6, 1974
Priority dateApr 11, 1973
Also published asDE2411583A1, DE2411583B2
Publication numberUS 3912962 A, US 3912962A, US-A-3912962, US3912962 A, US3912962A
InventorsNobutoki Samuro
Original AssigneeHitachi Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Colour pickup tube having a false signal preventing film
US 3912962 A
Images(6)
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Description  (OCR text may contain errors)

United States Patent Nobutoki 3,772,552 11/1973 Kubota ..3l3/390X [75] lnventor: Samuro Nobutoki, Mobara, Japan Primary Examiner siegfried Grimm 73 Assignee; Hitachi Ltd Tokyo, japan Attorney, Agent, or Firm-Charles E. Pfund, Esq.

[22] Filed: Mar. 6, 1974 [21] Appl. No.: 448,460

[57] ABSTRACT [30] Foreign Application Priority Data In a vidicon type pickup tube for use in single tube Apr. 11, 1973 Japan 48-40456 type or two tube type 01 ur television camera tems comprising a transparent glass window, an opti- [52] US. Cl. 313/371; 313/388; 313/390 cal colour analyzing stripe filter formed on one sur- [51] Int. C1. H01J 29/36 face of the glass window, and a false signal preventing Field of Seal'dl film made of a layer of transparent solid substance and 390 formed on the surface of the stripe filter, the false signal preventing film extends to a given extent beyond [56] References Cited or terminates short of the periphery of the stripe filter.

UNITED STATES PATENTS 3,026,416 3/ 1962 Weimer 313/371 X 12 Claims, 23 Drawing Figures 6 5 7 3 E31 I 2 1 4 I I l l| t l I: v 1 1 U l Sheet 1 of 6 US. Patent Oct. 14, 1975 Fla/- Sheet 2 of 6 3,912,962

U.S. Patent Oct. 14, 1975 F/G.3 m BAR am am US. Patent Oc't." 14, 1975 Sheet 3 of6 3,912,962

)oma 5 14a- (C) 5 mimw (d) ma; 5 BBB 15a BAR EBB U.S. Patent Oct.14,1975 Sheet4of6 3,912,962

F/G.8A F7683 U .S. Patent Got. 14, 1975 Sheet 5 of6 3,912,962

F/G./0B

F/G./0c

U.S. Patent Oct. 14,1975 Sheet6of6 3,912,962

F/G.//A

F/G.//B

COLOUR PICKUP TUBE HAVING A FALSE SIGNAL PREVENTING FILM BACKGROUND OF THE INVENTION This invention relates to a pickup tube for use in single tube type or two tube type colour television camera systems (hereinafter merely referred to as a filter encoded pickup tube) and more particularly to a vidicon type pickup tube in which an optical colour analyzing stripe filter is provided on one side surface of a transparent glass window.

Among pickup tubes of the type including an optical colour analyzing stripe filter may be mentioned the filter encoded pickup tubes. The filter encoded pickup tube is provided with an optical colour analyzing stripe filter on the rear surface of a transparent glass window directed to an object, and a transparent electroconductive film and a photoconductive film which are laminated on the stripe filter. In this case, the optical colour analyzing stripe filter comprises two filter components, one of them including an alternate arrangement of a filter element provided with fine stripes transmitting light of substantially all colours from the object and a filter element provided with fine stripes essentially preventing transmission of red light among light of various colours from the object. The other filter component includes an alternate arrangement of a filter element provided with fine stripes transmitting light of substantially of all colours from the object and a stripe element provided with fine stripes essentially preventing transmission of blue light among light of various colours from the object. These two filter components are superposed one upon the other such that respective filter elements of the former filter component intersect at an angle with the respective filter elements of the latter filter component so as to decrease beats caused by these two fine stripe filters.

With this construction, the light image of the object projected upon the photoconductive film through the transparent glass window is sampled at a spatial frequency of the optical colour analyzing stripe filter so that when the light image is scanned with an electron beam, a multiplex colour signal is produced having two carrier waves caused by the difference in the spacing between the filter element that blocks the red light and the filter element that blocks the blue light of said two filter components. By separating the colour signal by means of one lowpass filter and two bandpass filters it is possible to produce green, red and blue signals corresponding to the three primary colours of light.

Where such optical colour analyzing strip filter comprises a dichroic filter generally formed by vapour desposition technique, for example, since the thickness of the dichroic filter is of the order of 1 micron the thickness of the portion where two filters are superposed one upon another amounts to a maximum of about 3 microns with the result that the surface of the glass plate on which the optical colour analyzing stripe filter is formed becomes irregular. If the transparent electroconductive film and the photoconductive film were formed directly on such an irregular surface these films would also be irregular. When such an irregular photoconductive film is incorporated into a colour pickup tube an abnormal condition of the signal current will result due to an abnormal surface electric field corresponding to the irregularity of the pickup surface. Consequently, foreign substances deposited on the dichroic filter of delicate construction and on the irregular surface impair the photoconductive film thereby degrading its photoelectric conversion characteristic with the result that false image signal will be produced corresponding to the irregularity of the image pickup surface. Thus, various troubles such as the false colour signal are caused in the operation of the image pickup tube.

For the purpose of eliminating or decreasing the defects described we have already proposed an improved construction in which the optical colour analyzing stripe filter is coated with a false signal preventing film consisting of a layer of transparent solid substance such as a glass layer or a Si0 layer so as to eliminate the irregularity on the surface of the optical colour analyzing stripe filter. If desired, the surface of the filter is made more flat by polishing, chemical etching, or the polishing and chemical etching in combination. By this means, it was possible to make substantially fiat and smooth the transparent conductive film and the photoconductive film which are formed on the coated layer.

However, where a pickup tube is provided with an image pickup plate coated with such a false signal preventing film, it was found that in certain cases it is impossible to read out the signal current, and that such fault is caused by the exfoliation of the false signal preventing film or the cracking thereof which are caused by the heat treatment at the time of forming the NESA film.

More particularly, in the vidicon type colour pickup tube it is necessary to form a transparent conductive film on the inner surface of the transparent glass window so as to derive out the signal produced in the photoconductive film and to permit the incident rays to reach the photoconductive surface. Usually, a so-called NESA film is used as the transparent conductive film.

The NESA film consists essentially and mainly of tin oxide prepared by spraying onto a glass substrate a fine spray of a solution containing a solute consisting essentially of stannic chloride and then decomposing and oxidizing the stannic chloride. To form the film it is essential to heat the glass substrate at a temperature of about 500C so that due to the difference in the coefficient of thermal expansion of a structure formed on the glass substrate and the false signal preventing film applied onto the structure there is a tendency of peeling off the false signal preventing film or cracking thereof. For this reason, the NESA film also tends to peel off or crack.

SUMMARY OF THE INVENTION It is an object of this invention to eliminate such defects.

The formation of the peel off and cracks of the false signal preventing film on the substrate which are caused by the difference in the coefficient of thermal expansion depends upon the state of two dimensional spreading of the film on the surface of the glass substrate. More particularly, when the film is formed on the portion of the face plate of the pickup tube where the optical colour analyzing stripe filter is disposed or extends in a predetermined area of the mirror surface of the transparent glass window of the pickup tube, it was confirmed that there is no peeling off and cracking of the false signal preventing film caused by the heat treatment of the NESA film. It is believed that the coarse or irregular surface of the optical colour analyzing stripe filter functions to prevent the peeling off of the false signal prevenang film. It is also believed that the peeling off and cracking of the false signal preventing film can be precluded by decreasing the area in which the film extends on the glass mirror surface, thereby correspondingly decreasing the adhering area by a small bonding force between the film and the mirror surface.

Accordingly, the vidicon type colour pickup tube of this invention is characterized in that it comprises an optical colour analyzing stripe filter formed on the rear surface of a transparent glass window, and a false signal preventing film of a transparent solid substance and formed on the rear surface of the optical colour analyzing stripe filter and that the false signal preventing film is formed to extend to a mirror surface in a predetermined area of the transparent glass window or not to extend to the mirror surface of the transparent glass window.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the invention will become apparent from the following detailed description taken in conjunction with accompanying drawings in which:

FIG. 1 is a diagrammatic representation of one example of a vidicon type pickup tube;

FIG. 2 is a perspective view of an optical colour analyzing stripe filter;

FIG. 3. is a diagram showing an actual construction of the optical colour analyzing stripe filter;

FIG. 4 is a perspective view of the optical colour analyzing stripe filter shown in FIG. 3;

' FIGS. 5a and 5b are partial sectional views showing certain steps of preparing the colour analyzing stripe filter;

FIGS. 6a through 6d show examples of the relationship between the optical colour analyzing stripe filter and the false signal preventing film;

FIGS. 7a, 7b and 7c are partial sectional views showing different types of the combinations of the optical colour analyzing stripe filter and the false signal preventing film;

FIG. 8A shows a plan view of one embodiment of the pickup tube of this invention;

FIG. 8B is a sectional view of the pickup tube shown in FIG. 8A taken along a line VIIIB-VIIIB;

FIG. 9A shows a plane view of another embodiment of the pickup tube of this invention;

FIG. 9B is a sectional view of the pickup tube shown in FIG. 9A taken along a line IXB-IXB;

FIG. 10A shows a plan view of still another embodiment of the pickup tube of this invention;

FIGS. 10B and 10C are sectional views of the pickup tube shown in FIGS. 10A taken along lines XBXB and XCXC, respectively;

FIG. 11A shows a plan view of yet another embodiment of the pickup tube embodying the invention and FIGS. 11B and 11C are sectional views of the pickup tube shown in FIG. 11A taken along lines XIBXIB and XICXIC, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a filter encoded pickup tube will firstly be described with reference to FIG. 1 of the accompanying drawing. The pickup tube 1 illustrated therein comprises an electron gun 2, a focusing coil 3,

a deflection coil 4, a transparent glass window 5, an optical colour analyzing stripe filter 5, a transparent electroconductive film 7, a photoconductive film 8, anda signal take out terminal 9 connected to the transparent conductive film 7. An optical system is designated by a lens 10 and the locus of the electron beam emitted by the electron gun 2 is designated by 11. The optical colour analyzing stripe filter 6 comprises a dichroic filter including an alternate lamination of the layers of titanium dioxide TiO and silicon dioxide SiO for example, and includes two filter components 6A and 68, as shown in FIG. 2. One component 6A includes an alternate arrangement of stripe filter elements 6AW transmitting light of substantially all colours from an object, not shown, and stripe filter elements 6AR blocking the red light. Filter elements 6AW and 6AR have the same width DR. The other stripe filter component 63 includes a similar alternate arrangement of stripe filter elements 6BW transmitting light of substantially all colours and stripe filter elements 688 blocking blue light. Again, stripe filter elements 6BW and 6B8 have the same width DB. Widths DR and DB should be different, and in FIG. 2, DB is shown narrower than DR.

While in FIG. 2, the stripe filter elements 6AR, 6AW and 6BB, 6BW,of two filter components 6A and 6B are shown parallel with each other, actually, however, these two groups of the stripe filter elements intersect each other at a certain angle as shown in FIG. 3 so as to decrease the beats caused by these two groups.

One example of the actual construction of the optical colour analyzing stripe filter 6 is shown in FIGS. 4 and 5. More particularly, only stripe filter elements 6AR of the filter element 6A which substantially block red light are formed on the glass window 5 (see FIG. 5b) and thereafter the stripe filter elements 688 of the other filter component 68 which substantially block the blue light are formed on the stripe filter elements 6AR without forming the stripe filter elements 6AW and 6BW of the filter components 6A and 63, respectively, which transmit the light of all colours, as shown in FIG. 5a. According to this invention, for the purpose of eliminating or alleviating the surface irregularity of the optical colour analyzing stripe filter as shown in FIGS. 4 and 5a, thus eliminating the generation of the false signals, false signal preventing films consisting of a glass layer or a SiO layer are applied as shown by 12 in FIG. 6a, and polished or etched to form a smooth surface 12a in FIG. 6b. A similar film 13 applied as shown in FIG. 6c is polished or etched as shown at 13a in FIG. 6d. In particular after forming one type of the stripe filter element 6AR on the glass substrate 5, the false sig nal preventing film 13 is applied thereon as shown in FIG. 6c and polished or etched as shown in FIG. 6d. Thereafter alternate layers of the stripe filter element 633 as shown in FIG. 7c and the false signal preventing film 15 as shown in FIG. 7a, are repeatedly formed on the resulting assembly and finished products having substantially flat and smooth surfaces 14a, and 15 a as shown in FIGS. 7b and 7c are produced by polishing or chemically etching the surfaces, or the polishing and chemical etching in combination.

FIGS. 8 through 11 show different constructions of the false signal preventing films embodying the invention. Thus, in the construction shown in FIGS. 8A and 88, one or more types of the groups of the optical colour analyzing stripe filters are arranged in parallel or cross superposition relationship on one side surface of the transparent glass window 5 whose peripheral edge is vacuum sealed to the tube. A circular area 16 where the optical colour analyzing stripe filter 6 is coated (hereinafter referred to as a filter coated area 16) is provided, which of course contains the effective image pickup region 29 of the rectangular configuration of the pickup tube, and a false signal preventing film 18 of a layer of transparent solid substance such as a glass layer or a SiO layer is applied in concentric with the filter coated area 16, an area 17 of the film 18 (hereinafter referred to as a film coated area 17) having larger diameter than the filter coated area 16. It was found that if the length of the extension I of the film coated area 17 beyond the filter coated area 16 is limited to be equal to or less than about 5 mm, the false signal preventing film 18 would never peel off and/or crack. With the length of the extension I larger than 5 mm, the peel ing off and/or cracking is encountered. In other words, when the bonding surface between the false signal preventing film 18 and the mirror surface of the transparent glass window 5 is limited to an annular surface having a maximum width of about 5 mm it is possible to prevent the peeling off and/or the cracking of the false signal preventing film, owing to the bonding force between the film and the irregular surface of the optical colour analyzing stripe filter.

FIGS. 9A and 9B show another example of the pickup tube embodying the invention. In this embodiment, the film coated area 17 is made smaller than the filter coated area 16 on which the optical colour anacoated area 17 is made to be equal to or a little larger than the effective image pickup region 19, thus leaving exposed the annular portion of the filter coated area 16 about the film 18. It was confirmed that this construction also effectively prevents peeling off and/or cracking of the false signal preventing film 18. Again, it is preferable to limit the width of the annular portion to be equal to or less than 5 mm.

In FIGS. 8A and 88, an embodiment has been described wherein the film coated area l7 extends beyond the periphery of the filter coated area 16 and in FIGS. 9A and 98 another embodiment has been described wherein the film coated area 17 is contained within the filter coated area 16. It should be understood, however, that the film coated area 17 may be so formed as to irregularly intersect the periphery of the filter coated area 16. In other words, the periphery of the film coated area 17 may be confined in a region defined by the outward extension of 5 mm from the periphery of the filter coated area 16 and the inward spacing of 5 mm from the periphery of the filter coated area 16, the region having the width equal to 10 mm.

FIGS. 10A, 10B and 10C illustrate still another embodiment of the novel pickup tube of this invention. In this modification, a peripheral coating layer made of a different or same material as the stripe filter 6 which is formed in a rectangular filter coated area 16 and of a material different from that of the false signal preventing film 18 is formedto surround the area 16. The area of the peripheral coating layer 20 is hereinafter referred to a layer area 21. In this example, the effective image pickup region 29 is also rectangular and contained in the area 16. In this manner, the peripheral coating layer 20 is formed independently of the optical colour analyzing stripe filter 6 to surround the same such that the film coated area 17 covers the filter lyzing stripe filter is formed. For example, the film coated area 16 and extends beyond the layer area 21 with an extension I. The extension I is of a maximum width of less than about 5 mm.

FIGS. 11A, 11B and 11C show another embodiment of this invention, wherein the film coated area 17 covers filter coated area 16 and is contained within the layer area 21, leaving exposed an extension I of the same. In this case too, it is advantageous to limit the extension l to be less than about 5 mm. In FIGS. 10A, 10B and 10C, still another embodiment has been described wherein the film coated area 17 extends beyond the periphery of the layer area 21 and in FIGS. 11A, 11B and 11C further embodiment has been described wherein the periphery of the film coated area 17 is contained within the layer area 21. However, it should be understood that the film coated area 17 may be so formed as to irregularly intersect the periphery of the layer area 21. In other words, the periphery of the film coated area 17 may be confined in a region defined by the outward extension of 5 mm from the periphery of the layer area 21 and the inward spacing of 5 mm from the periphery of the layer area 21, the region having the width equal to 10 mm. In the embodiments shown in FIGS. 8 through 11, the filter coated area 16 shows a region in which two types of the optical colour analyzing stripe filters are arranged in crossed and superposed relationship as shown in FIG. 4 or only one type of the optical colour analyzing stripe filter is arranged as shown in FIG. 5b, and only the effective pickup region 19, in this area 16, is used to prevent the generation of the false signals, so that the configuration of the area 16 is not necessarily be limited to circular or rectangular as illustrated in these figures. The same is true for the peripheral coating layer 20.

' As has been described hereinabove, in accordance with this invention, in order to prevent peeling off and- /or cracking of the false signal preventing film 18, an optical colour analyzing stripe filter in the form of the interference filter coating is formed on a glass substrate, and the false signal preventing film 18 having a diameter larger or smaller by less than 5 mm than that of the filter is formed. However, it should be understood that the film firstly formed on the glass substrate should not always be constituted by a dichroic filter but may be formed of a substance different from the false signal preventing film and that the filter film should not always be constituted by parallel stripes. It was found that any other configurations of the filter such as a wire net or spots can also effectively prevent the peeling off and/or cracking of the false signal preventing film provided that the filter has a suitable percentage surface area, with respect to the area of false signal preventing film arrangement, configuration and dimension equivalent to those of 6AR and 6BB shown in FIG. 4.

Thus, according to this invention, by specifying the area in which the false signal preventing film is formed it is possible to prevent the peeling off and/or cracking of the film and hence the peeling off and/or cracking of the transparent conductive film caused by such peeling off and/or cracking of the false signal preventing film, as well as the decrease in the conductivity of the transparent conductive film.

What is claimed is:

1. In a colour vidicon type pickup tube for use in single tube type or two tube type colour television camera systems comprising a transparent glass window, an optical colour analyzing stripe filter formed on the rear surface of said glass window, and a false signal preventing film made of a layer of transparent solid substance and formed on the surface of said filter, the improvement wherein said false signal preventing film is formed in such a manner that the periphery of said false signal preventing film is confined in a region defined by an outward extension of mm from the periphery of said optical colour analyzing stripe filter and an inward spacing of 5 mm from the periphery of the same, said outward extension not touching the vacuum sealed portion of said glass window.

2. The pickup tube according to claim 1 wherein said false signal preventing film extends beyond the periphery of said optical colour analyzing stripe filter by a length of less than 5 mm.

3. The pickup tube according to claim 1 wherein said false signal preventing film covers a portion of an area in which said optical colour analyzing stripe filter is formed, said portion being spaced from the outer periphery of said area by a length of less than about 5 mm.

4. In a colour vidicon type pickup tube for use in single tube type or two tube type colour television camera systems comprising a transparent glass window, an optical colour analyzing stripe filter formed on the rear surface of said glass window, a false signal preventing film made of a layer of transparent solid substance and formed on the surface of said filter, and a peripheral coating layer formed to surround the periphery of said optical colour analyzing stripe filter, the improvement wherein said false signal preventing film is formed in such a manner that it covers said optical colour analyzing stripe filter and said peripheral coating layer and that the periphery of said false signal preventing film is confined in a region defined by an outward extension of 5 mm from the periphery of said peripheral coating layer and an inward spacing of 5 mm from the periphery of the same, said outward extension not touching the vacuum sealed portion of said glass window.

5. The pickup tube according to claim 4 wherein said false signal preventing film extends beyond the periphery of said peripheral coating layer by a length of less than 5 mm.

6. The pickup tube according to claim 4 wherein said peripheral coating layer is made of a substance which is the same as that comprising at least a portion of said optical colour analyzing stripe filter.

7. The pickup tube according to claim 4 wherein said peripheral coating layer is made of a material containing a substance from which at least a portion of said optical colour analyzing stripe filter is made of.

8. The pickup tube according to claim 4 wherein said peripheral coating layer is made of a substance different from that of said false signal preventing film.

9. The pickup tube according to claim 4 wherein said false signal preventing film covers a portion of said peripheral coating layer and terminates less than 5 mm short of the outer periphery of said peripheral coating layer.

10. The pickup tube according to claim 1 wherein the surface of said false signal preventing film is treated by a step selected from the group consisting of being polished, chemically etched or subjected to polishing and chemical etching in combination to form a flat and smooth surface.

1 1. The pickup tube according to claim 4 wherein the surface of said false signal preventing film is treated by a step selected from the group consisting of being polished, chemically etched or subjected to polishing and chemical etching in combination to form a flat and smooth surface.

12. The pickup tube according to claim 8 wherein the surface of said false signal preventing film is treated by a step selected from the group consisting of being polished, chemically etched or subjected to polishing and chemical etching in combination to form a flat and smooth surface.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. I 3,912,962 DATED October 14, 1975 lN\ ENTOR(S) Saburo Nobutoki It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 2, "filter 5" should read filter 6 Colunm 5, line 6, "region 29" should read region 19 Column 5, line 63, "region 29" should read region 19 Signed and Sealed this Ninth Day Of November 1976 [SEAL] Arrest:

RUTH C. MA SON C. MARSHALL DANN Amsrmx ()j/rcer (ummissmm'r ufPalenls and Trademarks

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3026416 *Jul 23, 1957Mar 20, 1962Rca CorpPhotoconductive devices
US3772552 *May 26, 1972Nov 13, 1973Sony CorpImage pickup tube
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3986069 *Mar 19, 1975Oct 12, 1976Tokyo Shibaura Electric Co., Ltd.Color stripe filter with two protective layers
US4029394 *May 15, 1975Jun 14, 1977Minolta Camera Kabushiki KaishaColor encoding filter and method for making the same
US4107568 *Nov 15, 1974Aug 15, 1978Hitachi, Ltd.Face plate for color pick-up tube
US5730766 *Nov 5, 1996Mar 24, 1998Bha Group, Inc.Non-round unitary filter cartridge
Classifications
U.S. Classification313/371, 313/390
International ClassificationH04N9/07, H01J29/45, H01J29/89, H01J29/10
Cooperative ClassificationH01J29/898, H01J2229/8916
European ClassificationH01J29/89H