GB2323715A - Optical detectionsystem protected against electromagnetic pulses - Google Patents
Optical detectionsystem protected against electromagnetic pulses Download PDFInfo
- Publication number
- GB2323715A GB2323715A GB9205329A GB9205329A GB2323715A GB 2323715 A GB2323715 A GB 2323715A GB 9205329 A GB9205329 A GB 9205329A GB 9205329 A GB9205329 A GB 9205329A GB 2323715 A GB2323715 A GB 2323715A
- Authority
- GB
- United Kingdom
- Prior art keywords
- gas
- plates
- photodetector
- enclosure
- transparent
- 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
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 32
- 238000001514 detection method Methods 0.000 claims abstract description 16
- 230000005855 radiation Effects 0.000 claims abstract description 11
- 239000012857 radioactive material Substances 0.000 claims abstract description 3
- 239000007789 gas Substances 0.000 claims description 32
- 230000005684 electric field Effects 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 2
- 230000005693 optoelectronics Effects 0.000 description 4
- 230000003595 spectral effect Effects 0.000 description 4
- 239000000523 sample Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000001960 triggered effect Effects 0.000 description 2
- 241000264877 Hippospongia communis Species 0.000 description 1
- 208000025274 Lightning injury Diseases 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000002844 continuous effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000003574 free electron Substances 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052743 krypton Inorganic materials 0.000 description 1
- DNNSSWSSYDEUBZ-UHFFFAOYSA-N krypton atom Chemical compound [Kr] DNNSSWSSYDEUBZ-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0216—Coatings
- H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Photometry And Measurement Of Optical Pulse Characteristics (AREA)
Abstract
This optical detection system includes a photodetector (1) placed in an enclosure (4) electrically continuous except for an input window (10) through which the optical radiation to be detected is transmitted to the photodetector (1). The protection of the optical detection system against electromagnetic pulses is achieved by the input window (10) including two parallel plates (5 and 6), spaced apart and transparent to the radiation to be detected, the space (7) delimited by the parallel sides of the transparent plates (5 and 6) and the edge of the conductive enclosure (4) on which the plates (5 and 6) are mounted being occupied by a rarefied gas transparent to the radiation to be detected in normal operation, and ionizable in case of an electromagnetic pulse to form then a continuous enclosure around the photodetector (1). Rapid ionization of the gas may be speeded up by providing a trace of radioactive material in the space 7 or by providing conductive strips on the inner faces of plates 5 and 8.
Description
2323715 1 Optical detection system protected against electromagnetic
pulses
The present invention relates to the field of optoelectronics and more particularly to the protection of optoelectronic systems by installing an optical detection system protected against electromagnetic pulses.
In the field of optoelectronic systems, the photodetectors used in the spectral bands ranging from ultraviolet to far infrared are in general comprised of photovoltaic diodes or Schottky diodes associated with silicon-based read circuits such as MOSFET, CMOS, CCD, etc. These detectors are placed in the focalization plane of optical systems which, in the general case, cannot be implemented with a material conducting electricity and which, consequently, do not allow to ensure the electromagnetic shielding of the detectors.
During phenomena such asa lightning stroke or a nuclear explosion, at high or low altitude in the case of equipment mounted in an aircraft, the optoelectronic equipment is struck by an electromagnetic pulse (EMP) whose electric fields, concentrated by the optical structures, can reach several hundred kilovolts per meter.
Similarly, the concept of "microwave weapon" is based on the transmission of electromagnetic pulses of several hundred kilovolts per meter at frequencies of several gigahertz. In this case, shielding is still more critic than for an electromagnetic pulse of nuclear origin because the wavelength is much shorter. Now, the detection photodiodes break down under these conditions for received energies under lpJ/cT?.
In the field of electromagnetic shielding, it is known to use shielding grids. But, taking into account the wavelengths of interest, the use of a simple shielding grid on optical systems would lead to the implementation of real deep honeycombs to efficiently shield the photodetector.
Such a device is not compatible with the fields of view and the apertures required for such systems.
An object of the present invention is an optical detection system protected against electromagnetic pulses so as to be efficient without disturbing the field of view or the optical aperture of the system.
To this end, a shield is implemented directly at the window of the detector in the form of a layer of rarefied gas, normally transparent in the spectral band of the d t tor and which becomes ionized ficant electric field. This fast gas spark gap and short thus the shielding envelope.
According to the present invention, an optical detection system protected against electromagnetic pulses including a photodetector responsive to the range of wavelengths to be detected is characterized in that the photodetector is placed in an enclosure electrically continuous except for an k_ - signi- ultra- with the occurence of a layer operates then as an s the incident wave by closing input window through which the optical radiation to be detected is transmitted to the photodetector, and in that the input window is made up of two parallel plates spaced apart and transparent to the optical radiation to be detec- ted, the space delimited by the parallel sides of the trans- parent plates and the edge of the conductive enclosure on which the plates are mounted being occupied by a rarefied gas, also transparent to the optical radiation to be detected in normal operation and ionizable in case of an electromagnetic pulse to form then an electrically continuous enclosure around the photodetector.
i 0 1 5 M . r 1 The present invention will be better understood and other features will become apparent from the following detailed description of a preferred embodiment given as a non-limi tative example with reference to the aCCOMDanying drawings, in which:
- Figure 1 is a schematic diagram of an optical detection head protected against electromagnetic pulses in.whie-h the inven tion is embodied as seen in longitudinal sectional view; - Figure 2 is a plane view of an embodiment of the plates of the input window enclosing the rarefied gas; Figure 3 is a schematic diagram of an optical detection system protected against electromagnetic pulses in which the invention is embodied.
The Following description is given with reference to an example applied to an infrared photodetector, but the same system is applicable to another photodetector, even if the shape of the case changes, as well as its internal pressure.
As shown in Figure 1, the optical detection head inc)udes an infrared photodetector 1 mounted in a case which, in conformance with common technology, forms an evacuated Dewar flask, that is a double-walled insulating vessel, the space between the walls being evacuated and the central portion being cooled by a cryogenic probe (not shown). The infrared photodetector 1 is placed within the flask, against the cooled internal wall, this central portion 2 being cooled by the cryogenic probe. The connections 3 of the detector pass through the evacuated space and output at the rear of the assembly, at the edges of the Dewar flask.
The outer body 4 of the Dewar flask is made of an elec- 1.0 trically highly conductive material, and this outer body is connected electrically and in a geometrically continuous manner (without holes) with the rest of the outer shield of the equipment located toward the rear. This outer body thus forms a good shield for the detector and its connections, except on the front side, where there is located the optical input window admitting the radiation to be detected.
A main object of the present invention is to implement a specific input window which allows to implement a conti nuous shield in the cases where this is necessary, in the case of an electromagnetic pulse.
In carryirg out the present invention, i. e., the window 10 is made up of two plates 5 and 6 made of a material transparent in the spectral band of the detector and which are, for example, made of germanium for an infrared photodetector system. For a photodetector operating in the visible or near infrared region, the two plates 5 and 6 of material transparent to the corresponding spectral band could be made of a specific glass matched to the wavelengths to be transmitted.
These two plates are separated by a space 7 filled with a rarefied gas such as that usually employed for lightningprotection spark gaps. Several gases are suitable. Prefera- bly, chemically inert gases such as neon, argon, krypton, will be chosen. This space filled with a rarefied gas is closed on the outer side by a highly conductive material in electrical contact with the outer body 4 of the case. In Figure 1, there is shown a seal 8 in contact with the outer body 4, for one thing, and with the rarefied gas, for another thing, and in which the transparent plates 5 and 6 delimiting the space for the gas are held in a gas-tight manner.
Referring to Figure 3, there is show n a protected infrared detection system which comprises, in addition to the optical detection head such as described above, an input.optical assembly 20, a cryogenic probe 30, electrical processing circuits 40, and the envelope 50 of the processing unit forming with the outer body 4 of the detection head an electrically continuous envelope in case of an electromagnetic pulse.
The photodetector system described above operates in the following manner: when an electromagnetic pulse arrives on the input window, the very high-strength and very sudden electric field ionizes the gas contained in the space 7. This gas becomes therefore highly conductive and thus closes the shield formed by the body 4, thus enclosing the photodetector in a continuous enclosure.
For the protection of the detector to be efficient, it is indispensable that the electric field created by the electromagnetic pulse does not reach the optical detector, and hence that the ionization of the gas be very rapid to form an electrically continuous enclosure in which the optical detector is protected, the gas-filled space acting as a shortcircuit.
The rapidity of the phenomenon of ionization and discharge in the rarefied gas depends an a number of parameters: nature of the gas, pressure, distance between equi- potentials, and presence of already ionized atoms in the gas at the time of arrival of the electromagnetic pulse.
The parameters related to the gas and the geometrical characteristics of the system can be optimized to make ioni zation as fast as possible. Moreover, additional characte ristics may be provided to speed up the discharge in the gas.
A first means to speed up the discharge in the gas and thus increase the efficiency of the protection of the photo detector consists in disposing in the vicinity of the space 7 or in this space a few traces of a radioactive material emitting gamma rays whose ionizing action on the gas allows to always maintain a sufficient number of ions and free elec trons so that the avalanche is very rapidly triggered.
Another means, provided the window is located sufficient ly far from the plane of optical focalization, thas is the plane of the photodetector 1, consists in depositing thin conductive strips 9 on the plates 5 and 6, on their side in contact with the oas, as shown in Figure 2, allowing to locally promote the increase of the electric field strength at the time of arrival of the electromagnetic pulse. This thin conductive strips, which form equipotential surfaces, must have points sufficiently close to each other to locally promote this increase of the electric field strength at the time of arrival of the electromagnetic pulse in order to rapidly trigger the discharge. If the plane of focalization is close to the input window, the optical image of the con ductive strips formed on the photodetector disturbs the re sulting image in normal operation.
The strips shown in Figure 2 are disposed along radii of the plates 5 and 6 forming the input window, but these thin strips may have other configurations, their role re maining the same.
To avoid an excessive wear of the conductive strips 9 in case of repeated electromagnetic pulses, these strips are made of a rather resistive material which will cause the rapid extension of ionization in the rarefied gas which thus conducts the maximum part of the short-circuit current.
Other improvements or modifications of structures may be envisaged without departing from the basic principles of the invention such as described above. In particular, the outer body 4 of the case and the ionizable input window may not be directly part of the detector assembly: they may be located more forward in the input optical assembly without changing the principle of the invention, provided the space containing a rarefied gas located between the two transparent plates forms, in case of ionization, a continuous surface with other conductive elements surrounding the photodetector.
Thus, a protection against violent electromagnetic pulses of various origin is obtained for a photodetector and is triggered by the electromagnetic pulse itself, the rarefied gas being used as a spark gap.
The present invention applies in particular to infrared and television cameras, but any optical detection system capable of being destroyed by an electromagnetic pulse can be equipped, in accordance with the same principle, of an optical input window made up of two plates transparent to the radiation to be transmitted closing a space containing a rarefied gas used as a spark gap to close a conductive surface surrounding the region to be protected in case of electromagnetic pulses.
1.0 , 5 -10 3 kti
Claims (8)
1. An optical detection system protected against electromagnetic pulses including a photodetector responsive to the range of wavelengths to be detected, wherein said photodetector is placed in an enclosure electrically continuous, except for an input window through which the radiation to be detected is transmitted to the detector, and wherein said input window is made up of two parallel plates, spaced apart and transparent to said optical radiation to be detected, the space delimited by the parallel sides of said spaced transparent plates and the edge of said conductive enclosure on which said plates are mounted being occupied by a rarefied gas, also transparent to said optical radiation to be detected in normal operation and ionizable in case of an electromagnetic pulse to form then an electrically continuous enclosure around said photodetector.
2. A system according to cl..-Aim 1, wherein said rarefied gas contains ionized atoms.
3. A system according to clairr wherein traces of a radioactive material emitting gamma rays are provided in or in the vicinity of said rarefied gas to speed up the triggering of ionization of the gas in case of an electromagnetic pulse.
L. A system according to clairn 1, wherein at least one thin conductive strip is formed on at least one side of said transparent plates in contact with the gas to put points distant from the edges of said conductive enclosure to a single potential and promote the increase of the electric field strength in case of an electromagnetic pulse to trigger the discharge in the gas.
5. A system according to claim 4, wherein thin conductive strips in contact with the edge of said enclosure are disposed on said transparent plates along radii.
6. A system according to claim 4, wherein said thin conductive strips are fabricated from a material sufficiently resistive to cause a rapid extension of ionization in the gas in case of an electromagnetic pulse.
7. A system according to claim 1, wherein said rarefied gas is a chimically inert gas.
8. An optical detection system protected against electromagnetic pulses substantially as described hereinbefore with reference to and as illustrated in the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9103308A FR2754637A1 (en) | 1991-03-19 | 1991-03-19 | Optical detector with protection against electromagnetic pulse |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9205329D0 GB9205329D0 (en) | 1998-06-10 |
| GB2323715A true GB2323715A (en) | 1998-09-30 |
| GB2323715B GB2323715B (en) | 1999-01-13 |
Family
ID=9410881
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9205329A Expired - Fee Related GB2323715B (en) | 1991-03-19 | 1992-03-12 | Optical detection system protected against electromagnetic pulses |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE4208526A1 (en) |
| FR (1) | FR2754637A1 (en) |
| GB (1) | GB2323715B (en) |
| IT (1) | IT1283986B1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ITUB20160819A1 (en) * | 2016-02-17 | 2017-08-17 | Tecnovideo S R L | CASE FOR EXPLOSION-PROOF CAMERA |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2109993A (en) * | 1981-04-01 | 1983-06-08 | Biox Tech Inc | Improved photodetector |
| EP0226151A1 (en) * | 1985-12-09 | 1987-06-24 | Southwall Technologies, Inc. | Multiple pane glass unit with electrically conductive transparent film for use as radiation shield |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0033814A3 (en) * | 1979-12-17 | 1981-09-09 | The Bendix Corporation | Electrical connector including surge protection for a plurality of circuits and method of making same |
| SU999185A1 (en) * | 1981-03-20 | 1983-02-23 | Предприятие П/Я В-2431 | Apparatus shielding device |
| DE3113349A1 (en) * | 1981-04-02 | 1982-10-21 | Siemens AG, 1000 Berlin und 8000 München | GAS DISCHARGE SURGE ARRESTER |
-
1991
- 1991-03-19 FR FR9103308A patent/FR2754637A1/en active Pending
-
1992
- 1992-02-27 IT IT92TO000161A patent/IT1283986B1/en active IP Right Grant
- 1992-03-12 GB GB9205329A patent/GB2323715B/en not_active Expired - Fee Related
- 1992-03-17 DE DE4208526A patent/DE4208526A1/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2109993A (en) * | 1981-04-01 | 1983-06-08 | Biox Tech Inc | Improved photodetector |
| EP0226151A1 (en) * | 1985-12-09 | 1987-06-24 | Southwall Technologies, Inc. | Multiple pane glass unit with electrically conductive transparent film for use as radiation shield |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ITUB20160819A1 (en) * | 2016-02-17 | 2017-08-17 | Tecnovideo S R L | CASE FOR EXPLOSION-PROOF CAMERA |
| WO2017140653A1 (en) * | 2016-02-17 | 2017-08-24 | Tecnovideo S.R.L. | Explosion-proof case for a video camera |
Also Published As
| Publication number | Publication date |
|---|---|
| ITTO920161A0 (en) | 1992-02-27 |
| FR2754637A1 (en) | 1998-04-17 |
| IT1283986B1 (en) | 1998-05-07 |
| GB9205329D0 (en) | 1998-06-10 |
| ITTO920161A1 (en) | 1993-08-27 |
| GB2323715B (en) | 1999-01-13 |
| DE4208526A1 (en) | 1998-09-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19990413 |