EP0182405A1 - Photoelektrische Vorrichtung zum Nachweisen leuchtender Ereignisse - Google Patents

Photoelektrische Vorrichtung zum Nachweisen leuchtender Ereignisse Download PDF

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Publication number
EP0182405A1
EP0182405A1 EP85201691A EP85201691A EP0182405A1 EP 0182405 A1 EP0182405 A1 EP 0182405A1 EP 85201691 A EP85201691 A EP 85201691A EP 85201691 A EP85201691 A EP 85201691A EP 0182405 A1 EP0182405 A1 EP 0182405A1
Authority
EP
European Patent Office
Prior art keywords
detection device
filter
wavelength
photoelectric detection
photocathode
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
EP85201691A
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English (en)
French (fr)
Other versions
EP0182405B1 (de
Inventor
Pierre Dolizy
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.)
Laboratoires dElectronique Philips SAS
Koninklijke Philips NV
Original Assignee
Electronique & Physique
Laboratoires dElectronique Philips SAS
Laboratoires dElectronique et de Physique Appliquee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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.)
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Publication date
Application filed by Electronique & Physique, Laboratoires dElectronique Philips SAS, Laboratoires dElectronique et de Physique Appliquee, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Electronique & Physique
Publication of EP0182405A1 publication Critical patent/EP0182405A1/de
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Publication of EP0182405B1 publication Critical patent/EP0182405B1/de
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Classifications

    • 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
    • H01J29/86—Vessels; Containers; Vacuum locks
    • H01J29/89—Optical or photographic arrangements structurally combined or co-operating with the vessel
    • 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
    • H01J31/42—Image pick-up tubes having an input of visible light and electric output with image screen generating a composite electron beam which is deflected as a whole past a stationary probe to simulate a scanning effect, e.g. Farnsworth pick-up tube

Definitions

  • the invention relates to a photoelectric detection device comprising a vacuum envelope provided with a window having a substrate supporting a photocathode on the internal face of the vacuum envelope, the device being sensitive to incident light radiation between a low threshold at length. of low wave X l and a high threshold at wavelength X 2 higher, the electrons emitted by the photocathode being focused, accelerated and deflected by electronic means to deliver signals or an image representative of light events projected on the photocathode.
  • the invention also relates to tubes using this type of photoelectric detection device such as image dissecting tubes, and in general all image rendering tubes for. which localized restitution errors are to be eliminated.
  • This aspect of localized errors is of great importance in image dissecting tubes.
  • These tubes are generally intended to detect point events appearing in a field of vision mainly in the form of a scan of the sky as for example in the observation clouds or particles in meteorology or in the pursuit of stars in astronomy.
  • the image detected by such a tube thus appears in the form of a fairly uniform image in which appear events to be detected of very small dimension compared to the total extent of the image.
  • this image also presents faults which can be confused with the events to be detected or disturb their detection and which thus harm the efficiency of the dissecting tube.
  • a dissector tube is generally made up a vacuum envelope provided with an entry window provided with a photocathode emitting electrons under the action of incident light radiation.
  • the scene to be analyzed is projected optically on the input window.
  • the electrons emitted by the photocathode are accelerated, focused and deflected, by appropriate electronic optics, on an electron multiplier which has at its entrance a very small opening.
  • an electronic scanning system the electrons emitted by each point of the image formed on the photocathode, penetrate into the multiplier which restores by usual electronic means an electrical signal which one can visualize on a screen or exploit to position the dissector tube.
  • the object of the invention is thus to reduce the number of image defects and the disturbances they create.
  • the window is provided with at least one light filter which determines the range of wavelengths for which the detection device is operational, by eliminating the lengths wavelength greater than a wavelength ⁇ f , such that ⁇ 1 ⁇ f ⁇ 2 .
  • This light filter can be a bandpass filter which also eliminates wavelengths less than a wavelength ⁇ ' f such that ⁇ 1 ⁇ ' f ⁇ f .
  • defects were due for the most part to a disturbance in the functioning of the photocathode, in the form of variations in its quantum efficiency.
  • These defects are usually point defects of approximately 10 ⁇ m x 10 ⁇ m or oblong defects of approximately 10 ⁇ m x 50 ⁇ m.
  • These defects can cause variations in quantum efficiency of the same order of magnitude as the variations in quantum emission which occur under the action of the events to be detected and which are of the order of 1%. It follows that it can be difficult in many cases to distinguish the useful signal from the disturbed signal.
  • thin layer antimonides tend to nucleate on the substrate and cause local variations in thickness which can reach approximately 2 nm.
  • the optical parameters n m and k m of the layers which are respectively the real and complex indices of a photocathode of thickness e m , are very sensitive to variations in thickness and composition of the layers. It follows that local variations in the photoelectric power Y T can reach values of around 4%. It appeared that the composition fluctuations were strongly linked to the nature of the substrate, the alkaline materials reacting with the substrate when it is made of glass.
  • the invention eliminates the influence of the sensitivity threshold X 2 of the detection device by filtering the incident light spectrum and removing this high threshold ⁇ 2.
  • the high sensitivity threshold of the detection device after filtering is then that of the interposed filter.
  • This filter is for example an interference filter constituted by a stack of layers of materials with high and low optical index, the thicknesses of which are determined as a function of the spectral band where transmission is desired.
  • Materials with a high optical index are for example Zr0 2 , Ce0 2 , ZnS, Ti0 2 , Ta 2 0 5 , W0 3 .
  • Materials with a low optical index are for example MgF 2 , Na Al F 2 , CaF 2 , BaF 2 .
  • a photocathode is deposited on a substrate and the photoelectric power of this photocathode is determined as a function of the wavelength.
  • the filter is then determined to eliminate the wavelengths greater than the value ⁇ f therefore eliminate the wavelengths close to the sensitivity threshold ⁇ 2 ( ⁇ 2 > ⁇ f ).
  • the layers of high and low optical index materials will be stacked on top of each other with thicknesses which will depend on the type of filter desired.
  • the stack will then be of type A: or (B) means a thickness, equal to , material (B) with low index n, and (H) means a thickness equal to , of material (H) with high index N, the number p indicating 2N that this structure is repeated p times.
  • the low sensitivity threshold of the photoelectric detection device was also responsible for the defects in the photoelectric power of the photocathode. Also an additional improvement is given to the invention by also eliminating the low sensitivity threshold of the photoelectric detection device.
  • ⁇ 0 570 nm.
  • the thickness of this will be 68 nm to have a maximum photoelectric power in the green.
  • the filter thus determined can be produced in the form of a removable structure placed in front of the entrance window of the photoelectric detector, the filter being mounted on a support integral with the vacuum envelope.
  • a second mode it is also possible to deposit the layers constituting the filter directly on the input window of the photoelectric detector outside. and / or inside the vacuum envelope. According to this second embodiment, several variant embodiments are possible.
  • the long wavelengths of the spectrum are eliminated by depositing the low-pass filter on the external face of the substrate.
  • the two ends of the spectrum are eliminated by depositing the low-pass filter on the external face of the substrate and the high-pass filter on the internal face of the substrate between the substrate and the photocathode.
  • the two ends of the spectrum are eliminated by depositing the bandpass filter on the external face of the substrate.
  • the filter is specifically adapted to this photocathode.
  • the filter is placed between the substrate and the photocathode, it is necessary to carry out a sensitivity measurement beforehand on a control photocathode deposited directly on a substrate of the same kind, to determine the extent of the spectrum where the corrections are to perform.
  • to make the filter located inside the envelope avoid using ZnS and Na Al F 2 .
  • the substrate which supports the photocathode is usually made of glass.
  • the variations in composition of the photocathode which are due to the chemical reactions of alkalis with glass can be reduced by replacing this vitreous substrate with a monocrystalline substrate such as quartz or corundum.
  • the substrate then having a better surface condition allows better nucleation of the constituent layers of the photocathode or of the filters, thus improving their respective properties.
  • This attenuation of the variations of the photoelectric power with the monocrystalline nature of the substrate is especially noticeable in the part blue spectrum.
  • Another variant of the invention correcting the red and blue parts of the spectrum consists in using a low-pass filter - for correcting the red part of the spectrum - placed on the external face of the monocrystalline substrate.
  • FIG. 1 represents an image dissecting tube comprising a vacuum envelope 10, having an entry window formed of a substrate 12 on which a photocathode 11 is deposited.
  • a vacuum envelope Inside the vacuum envelope and at the opposite the entrance window of the tube is placed an electron multiplier 13 in front of which is placed a plate 15 having a small opening 14.
  • electrodes 17 placed at suitable potentials to accelerate and focus the electrons emitted by the photocathode 11.
  • Deflection coils 16 deflect the electron beam and ensure the scanning so that the electrons emitted by each point of the photocathode are focused on the opening 14 along a path 18.
  • This electron beam is then taken up by the multiplier 13 which provides an electrical signal on an output 19 which is taken up either by a monitor tube or by an electronic signal processing device.
  • an interference filter 20 In front of the substrate 12 is arranged an interference filter 20.
  • An optical device not shown in the figure projects the scene to be analyzed onto the entry window of the dissecting tube.
  • Figure 2 is shown in more detail the entire inlet window of the dissector tube according to a non-limiting example.
  • the photocathode 11 On the face of the substrate 12, which is located on the interior side of the vacuum envelope, is arranged the photocathode 11.
  • a filter On the face of the substrate 12, which is located outside of the vacuum envelope, a filter is arranged.
  • interference 20 consisting of a stack of layers 20 1 , 20 2 , ..., 20p which according to this figure consist of layers of a low index material 20 1 , 20 3 , ..., 20p alternated with layers high index material 20 2 , 20 4 , ..., 20 p-1 .
  • This stack is representative of the type A filters already described.
  • the scene to be analyzed is projected onto the dissecting tube according to an incident beam 22 of light of wavelengths spanning a wide spectrum. It crosses the interference filter 20 to give the output a beam of light whose wavelengths are limited in the upper part and possibly in the lower part according to the characteristics given to the filter (s) in relation to the invention described previously.
  • This beam-u with filtered wavelengths crosses the substrate 12 and is absorbed in the photocathode 11 to give rise to electrons emitted over the entire surface of the photocathode.
  • the electrons emitted by each image point of the photocathode are brought to the small opening 14 located at the entrance of the electron multiplier 13.
  • the electrical signal obtained is then processed by processing means whose characteristics make it possible to discern two distant image points on the photocathode of a few microns.
  • the invention relates to image rendering tubes for which variations with very short distances from photoelectric power produce harmful effects to be eliminated.

Landscapes

  • Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
EP85201691A 1984-10-30 1985-10-16 Photoelektrische Vorrichtung zum Nachweisen leuchtender Ereignisse Expired - Lifetime EP0182405B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8416554A FR2572583B1 (fr) 1984-10-30 1984-10-30 Dispositif photoelectrique pour la detection d'evenements lumineux
FR8416554 1984-10-30

Publications (2)

Publication Number Publication Date
EP0182405A1 true EP0182405A1 (de) 1986-05-28
EP0182405B1 EP0182405B1 (de) 1992-04-22

Family

ID=9309123

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85201691A Expired - Lifetime EP0182405B1 (de) 1984-10-30 1985-10-16 Photoelektrische Vorrichtung zum Nachweisen leuchtender Ereignisse

Country Status (5)

Country Link
US (1) US4698496A (de)
EP (1) EP0182405B1 (de)
JP (1) JPS61109251A (de)
DE (1) DE3585909D1 (de)
FR (1) FR2572583B1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5304815A (en) * 1986-09-11 1994-04-19 Canon Kabushiki Kaisha Electron emission elements
US5311098A (en) * 1992-05-26 1994-05-10 The United States Of America As Represented By The Secretary Of The Navy Interference photocathode
GB2271464A (en) * 1992-08-21 1994-04-13 Sharp Kk Photoemission apparatus.

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2871371A (en) * 1954-05-06 1959-01-27 Rca Corp Wide-band interference light filter
US3787609A (en) * 1972-06-13 1974-01-22 Itt Electronic color filter system
US3796826A (en) * 1971-03-11 1974-03-12 Spar Aerospace Prod Ltd Multispectral camera

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2821637A (en) * 1953-11-30 1958-01-28 Westinghouse Electric Corp Light image reproduction devices
US3663913A (en) * 1967-12-22 1972-05-16 Tohoku Metal Ind Ltd Core coil having a improved temperature characteristic
US3575628A (en) * 1968-11-26 1971-04-20 Westinghouse Electric Corp Transmissive photocathode and devices utilizing the same
US3863093A (en) * 1969-01-30 1975-01-28 Itt Multicolor direct view device
US3748523A (en) * 1971-08-04 1973-07-24 Westinghouse Electric Corp Broad spectral response pickup tube
US4004176A (en) * 1972-10-16 1977-01-18 Hitachi, Ltd. Stripe-shaped color separation filter for image pickup tube and method for manufacturing the same
JPS5256850A (en) * 1975-11-05 1977-05-10 Nec Corp Color noctovision
GB1605139A (en) * 1977-06-04 1982-01-27 Pilkington Perkin Elmer Ltd Optical apparatus
JPS56135809A (en) * 1980-03-26 1981-10-23 Hino Kinzoku Sangyo Kk Filter for astronominal observation
FR2515870A1 (fr) * 1981-11-04 1983-05-06 Labo Electronique Physique Photocathode pour entree de tube electronique comportant un dispositif semi-conducteur avec photo-emission par transmission

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2871371A (en) * 1954-05-06 1959-01-27 Rca Corp Wide-band interference light filter
US3796826A (en) * 1971-03-11 1974-03-12 Spar Aerospace Prod Ltd Multispectral camera
US3787609A (en) * 1972-06-13 1974-01-22 Itt Electronic color filter system

Also Published As

Publication number Publication date
US4698496A (en) 1987-10-06
DE3585909D1 (de) 1992-05-27
JPS61109251A (ja) 1986-05-27
FR2572583A1 (fr) 1986-05-02
FR2572583B1 (fr) 1987-02-20
EP0182405B1 (de) 1992-04-22

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