EP0248426A2 - Fernsehkameraröhre - Google Patents

Fernsehkameraröhre Download PDF

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Publication number
EP0248426A2
EP0248426A2 EP87108095A EP87108095A EP0248426A2 EP 0248426 A2 EP0248426 A2 EP 0248426A2 EP 87108095 A EP87108095 A EP 87108095A EP 87108095 A EP87108095 A EP 87108095A EP 0248426 A2 EP0248426 A2 EP 0248426A2
Authority
EP
European Patent Office
Prior art keywords
photo
pick
tube
conductive film
conductive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP87108095A
Other languages
English (en)
French (fr)
Other versions
EP0248426A3 (en
EP0248426B1 (de
Inventor
Yukio Takasaki
Tadaaki Hirai
Masanori Maruyama
Yasuhiko Nonaka
Eisuke Inoue
Shinichi Kato
Keiichi Shidara
Mitsuhiro Kurashige
Kenkichi Tanioka
Saburo Okazaki
Junichi Yamazaki
Norifumi Egami
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Japan Broadcasting Corp
Original Assignee
Hitachi Ltd
Nippon Hoso Kyokai NHK
Japan Broadcasting Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd, Nippon Hoso Kyokai NHK, Japan Broadcasting Corp filed Critical Hitachi Ltd
Publication of EP0248426A2 publication Critical patent/EP0248426A2/de
Publication of EP0248426A3 publication Critical patent/EP0248426A3/en
Application granted granted Critical
Publication of EP0248426B1 publication Critical patent/EP0248426B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/26—Image pick-up tubes having an input of visible light and electric output
    • H01J31/28—Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen
    • H01J31/34—Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen having regulation of screen potential at cathode potential, e.g. orthicon
    • H01J31/38—Tubes with photoconductive screen, e.g. vidicon
    • 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
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/39—Charge-storage screens
    • H01J29/45—Charge-storage screens exhibiting internal electric effects caused by electromagnetic radiation, e.g. photoconductive screen, photodielectric screen, photovoltaic screen

Definitions

  • the present invention relates to a photo-conductive TV pick-up tube which is far higher in resolution than conventional ones.
  • the photo-conductive pick-up tube is usually made up of a photo-conductive target for converting an optical image into an electric signal, an electron gun for emitting a scanning electron beam to detect the electric signal, and an electron beam control section for focusing and deflecting the electron beam.
  • image pick-up tube for high definition television In order to improve the resolution of a photo-conductive pick-up tube by increasing the number of scanning lines, various methods have been used, that is, the scanning electron beam has been made thin, or a photo-conductive film having a high resolving power has been used for forming the photo-conductive target.
  • the photo-conductive pick-up tube having such a construction will be hereinafter referred to as "image pick-up tube for high definition television.”
  • a 1-in (2,54 cm-) image pick-up tube for high definition television using 1125 scanning lines and including a photo-conductive film which has a thickness of 4 to 6 /..I.m and is made of an amorphous photo-conductive material containing selenium as main component, can produce an amplitude response of about 45 % at 800 TV lines (cf. the Journal of the Institute of Television Engineers of Japan, Vol. 39, No. 8, August 1985, pages 663 to 674).
  • the conventional image pick-up tube for high definition television has high resolution as mentioned above, but the resolution of the image pick-up tube is much less than that of a 35 mm or 75 mm video film. Accordingly, it is ardently desired to further improve the resolution of the image pick-up tube for high definition television.
  • the present invention is based on the finding that when a conventional image pick-up tube for high definition television is operated, the variation in the surface potential at the surface of the photo-conductive film due to incident light is great, which makes it impossible for the image pick-up tube to have the desired high resolution.
  • the scanning electron beam is made thin to attain high resolution, it is deflected due to the avobe-mentioned great variation in the surface potential. This effect is remarkable in the vicinity of the edge of an optical image, and thus a reconstructed pattern will become fuzzy.
  • the photo-conductive pick-up tube shall be small-sized and include a photo-conductive film which is low in manufacturing costs, particularly concerning a reduction of the deposition time of the photo-conductive film to enhance the manufacturing productivity.
  • the variation in surface potential at the surface of the photo-conductive film is made small by increasing the capacity of the photo-conductive film.
  • the photo-conductive film preferably has a capacity of 15 to 150 u.F/m 2 , which leads to a marked reduction of the surface potential variation.
  • the thickness of the photo-conductive film is made small which further reduces the variation of the surface potential of the photo-conductive film.
  • the diameter of the scanning electron beam is made small.
  • Fig. 1 shows a schematic cross-section of a photo-conductive pick-up tube, to which the present invention is applied. It comprises a cathode 1, a scanning electron beam 2, an electrode 3 for controlling the electron beam 2, a beam limiting aperture 4, a photo-conductive film 5, a mesh electrode 6, a transparent electrode 7, a face plate 8 made of glass, and a glass bulb 9.
  • an external power source 10 is connected between the cathode 1 and the transparent electrode 7 as shown in Fig. 1, and further the photo-conductive film 5 is scanned with the focused electron beam 2, the surface of the photo-conductive film 5 on the scanning side is negatively charged, and the potential of this surface becomes nearly equal to the cathode potential.
  • the photo-conductive film 5 is charged up to a level substantially equal to the output level of the external power source 10.
  • the resistance thereof decreases, and thus the negative charges on the surface of the photo-conductive film 5 are decreased by discharge. Accordingly, a charge pattern corresponding to the intensity distribution of the incident light is formed on the surface of the photo-conductive film 5 on the scanning side, that is, a variation in the surface potential is caused by the intensity distribution of the incident light.
  • the photo-conductive film 5 is scanned with the electron beam 2, the electron beam 2 lands on the photo-conductive film 5 in accordance with the above variation in the surface potential, and hence a charging current corresponding to the discharged electric quantity flows through an amperemeter 11.
  • the optical image formed on the photo-conductive layer 5 is time-sequentially converted into a signal current.
  • Fig. 2 shows an example of the relation between the capacity per unit area of photo-conductive film and the amplitude response for a 2/3-in. (1,7 cm-) photo-conductive pick-up tube provided with a beam limiting aperture having a diameter of 10 um which is operated with 1125 scanning lines.
  • Fig. 2 shows that the amplitude response, that is, the resolution of the pick-up tube, can be greatly improved by making the capacity per unit area (hereinafter referred to as "normalized capacity") of the photo-conductive film a 15 aF/m2.
  • the resolution becomes higher the larger the normalized capacity is made.
  • the lag namely, the delay of the photo-response, becomes remarkable.
  • the normalized capacity of the photo-conductive film ⁇ 150 ⁇ F/m 2 it is desirable from the practical point of view to make the normalized capacity of the photo-conductive film ⁇ 150 ⁇ F/m 2 ; the upper limit of the normalized capacity should be determined in accordance with the specific purpose, for which the pick-up tube is used.
  • the photo-conductive film is made of an amorphous photo-conductive material which contains selenium having a high resolving power as a main component
  • the normalized capacity of the film can be made greater than 15 uF/m 2 , and the resolution of the pick-up tube can be markedly improved thereby.
  • the improvement in resolution by increasing the normalized capacity of the photo-conductive film is remarkable in a case where the diameter of the beam limiting aperture 4 is made small, and a large number of scanning lines is used.
  • the diameter of the beam limiting aperture is large, it is impossible to greatly improve the resolution by increasing the normalized capacity of the photo-conductive film , since the resolution is restricted by the beam diameter determined by the aperture 4.
  • the diameter of the beam limiting aperture 4 is made smaller than 15 ⁇ m for a 2/3-in. (1,7 cm-) pick-up tube, and smaller than 25 ⁇ m for a 1-in. (2,54cm-) pick-up tube.
  • the electric quantity carried by the electron beam 2 decreases as the diameter of the beam limiting aperture 4 is smaller. It is desirable from the practical point of view to make the diameter of the aperture 4 greater than 5 ⁇ m as a lower limit.
  • Fig. 4a and 4b show examples of the beam limiting aperture 4.
  • the cross section profile of the (enlarged) portion of the beam limiting aperture 4 which is parallel to its center axis is defined by a polygon-like plurality of straight lines or a curved line on each side of the center axis, as shown in Figs. 4a or 4b, respectively.
  • Fig. 3 shows an example of the relation between the resolution of a 2/3-in (1,7 cm-) photo-conductive pick-up tube having the above-mentioned construction, and the distance between the mesh electrode and the photo-conductive film.
  • the distance between the mesh electrode 6 and the photo-conductive film 5 must be in a range from 1 to 3 mm, and preferably in the range from 1 to 2 mm.
  • a 1-in. (2,54 cm-) photo-conductive pick-up tube and a 2/3-in. (1,7 cm-) photo-conductive pick-up tube according to the present invention were operated so as to have 1125 scanning lines, and produced an amplitude response of more than 80 % and of about 40 %, respectively, at 800 TV lines, while conventional photo-conductive pick-up tubes of the same size gave an amplitude response of about 45 % and of about 30 %, respectively.
  • the resolution of photo-conductive pick-up tubes can be markedly improved on the basis of the present invention.
  • a transparent electrode containing Sn0 2 as its main component is deposited on a 1-in. (2,54 cm-) diameter glass substracte by a chemical vapor deposition method, and an amorphous photo-conductive film made of selenium, arsenic and tellurium and containing more than 50 % by mass of selenium is deposited on the transparent electrode by a vacuum deposition method in a vacuum of less than 1,3 mPa (10- 5 Torr).
  • the thickness of the photo-conductive film is made such to be in the range from 0,35 to 3,5 um.
  • a porous Sb 2 S 3 film is deposited on the photo-conductive film in an atmosphere of argon kept at a pressure of 1,3 Pa (10- 2 Torr) so that the tickness of the Sb 2 S 3 film lies in a range from 40 to 100 nm (400 to 1000 A), to be used as an electron beam landing layer.
  • a photo-conductive target having a normalized capacity of more than 15 ⁇ F/m 2 is formed.
  • the above photo-conductive target, an electron gun, a mesh electrode an an electrode structure for focusing and deflecting the electron beam are mounted in a glass bulb, which is then evacuated.
  • the diameter of the beam limiting aperture is made equal to 15 ⁇ m.
  • a transparent electrode containing Sn0 2 or ln 2 0 3 as its main component is deposited on a 2/3- in. (1,7 cm-) diameter glass substrate by a chemical vapor deposition method or by sputtering, and a Ce0 2 film is deposited on the transparent electrode to a thickness of 15 nm (150 A) by a vacuum deposition method, to be used as a hole blocking layer.
  • first, second and third photo-conductive layers are successively deposited by a vacuum deposition method so that a photo-conductive film having a thickness of 0,35 to 3,5 ⁇ m is formed on the Ce0 5 film.
  • the first photo-conductive layer is an amorphous Se-As layer which has a thickness of 10 to 100 nm (100 to 1000A ), and in which the mean arsenic content is less than 15 % by mass.
  • the second photo-conductive layer serves as a sensitizing layer and is an amorphous Se-Te-As layer which has a thickness of 20 to 150 nm (200 to 1500 A), and in which the mean tellurium content lies within a range from 20 to 50 % by mass and the mean arsenic content is less than 5 % by mass.
  • the third photo-conductive layer is an amophous Se-As layer, in which the mean arsenic content is less than 15 % by mass.
  • a porous Sb 2 S 3 film is deposited on the photo-conductive film to a thickness of 40 to 100 nm (400 to 1000 A) in an inert atmosphere kept at a pressure of 1,3 Pa (10- 2 Torr), to be used as an electron beam landing layer.
  • a photo-conductive target having a normalized capacity of more than 15 ⁇ F/m 2 is obtained.
  • the third photo-conductive layer is made thin to increase the normalized capacity thereof, the sensitivity of the photo-conductive film is not decreased.
  • the electron gun is of a diode type
  • the beam limiting aperture has a cross-section such as (enlarged) shown in Fig. 4a, that is, the cross-section profile of the portion of the aperture which is parallel to its center axis, is shaped polygon-like and defined by two straight lines on both sides of the center axis, the minimum diameter of the beam limiting aperture being 10 um
  • the mesh electrode is formed of a 1500 to 2000-mesh copper screen, and the distance between the mesh electrode and the photo-conductive target lies in a range from 1 to 2 mm.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
EP87108095A 1986-06-04 1987-06-04 Fernsehkameraröhre Expired - Lifetime EP0248426B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP12797886A JPH0789473B2 (ja) 1986-06-04 1986-06-04 撮像管
JP127978/86 1986-06-04

Publications (3)

Publication Number Publication Date
EP0248426A2 true EP0248426A2 (de) 1987-12-09
EP0248426A3 EP0248426A3 (en) 1989-05-03
EP0248426B1 EP0248426B1 (de) 1994-09-07

Family

ID=14973402

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87108095A Expired - Lifetime EP0248426B1 (de) 1986-06-04 1987-06-04 Fernsehkameraröhre

Country Status (3)

Country Link
EP (1) EP0248426B1 (de)
JP (1) JPH0789473B2 (de)
DE (1) DE3750491T2 (de)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3426235A (en) * 1966-12-20 1969-02-04 Rca Corp Pickup device
DE2129176A1 (de) * 1971-06-11 1973-01-04 Siemens Ag Lichtempfindliches target fuer eine vidikon-bildaufnahmeroehre

Also Published As

Publication number Publication date
JPH0789473B2 (ja) 1995-09-27
DE3750491D1 (de) 1994-10-13
DE3750491T2 (de) 1995-01-19
EP0248426A3 (en) 1989-05-03
EP0248426B1 (de) 1994-09-07
JPS62285350A (ja) 1987-12-11

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