GB2147172A - Imaging or like apparatus - Google Patents
Imaging or like apparatus Download PDFInfo
- Publication number
- GB2147172A GB2147172A GB08423832A GB8423832A GB2147172A GB 2147172 A GB2147172 A GB 2147172A GB 08423832 A GB08423832 A GB 08423832A GB 8423832 A GB8423832 A GB 8423832A GB 2147172 A GB2147172 A GB 2147172A
- Authority
- GB
- United Kingdom
- Prior art keywords
- liquid crystal
- radiation
- detector means
- detector
- condition
- 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
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/50—Constructional details
- H04N23/55—Optical parts specially adapted for electronic image sensors; Mounting thereof
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Transforming Light Signals Into Electric Signals (AREA)
Abstract
Where detectors, for example in thermal imaging apparatus, have been necessarily periodically irradiated at a predetermined level to provide a grey level reference this has hitherto been effected by periodically moving an opaque member in the form of a blade onto the optical path to intercept the radiation normally incident upon the detector. Since it is a mechanical arrangement, the blade is difficult to operate in the precise time intervals; thus the present invention comprises the replacement of the blade and its drive mechanism with a liquid crystal assembly 1, 2, 3. The liquid crystal assembly becomes diffusive when a voltage is applied giving a relatively uniform level of radiation at the detector 5 which may be used to provide a grey level reference. <IMAGE>
Description
SPECIFICATION
Imaging or like apparatus
This invention relates to imaging or like apparatus (eg. thermal imaging apparatus) having detector means upon which electromagnetic radiation from an object or scene is directed and which detector means requires to be periodically irradiated art a predetermined low level, preferably related to the radiance of the object or scene, in order to provide a reference, for example a grey level reference.
Hitherto, this irradiation has been achieved by periodically moving an opaque member, for example in the form of a blade, into the optical path to interrupt the radiation normally incident upon the detector means. Such an arrangement has various shortcomings. Since it is a a mechanical arrangement, it is difficult to drive the blade at precise time intervals especially during conditions of vibration and acceleration and where there are limitations on space for the drive arrangement. Moreover, the opaque blade gives a radiance which is unrelated to the object or scene radiance.
It is therefore an object of the present invention to overcome these shortcomings in a relatively simple manner.
Accordingtothe present invention, imaging apparatus having detector means upon which electromagnetic radiation from a source is directed and which detector means requires to be periodically exposed to a predetermined radiance level, includes liquid crystal means located in between the detector means and the source, the liquid crystal means being changeable from a condition in which there is substantially no effect on the radiation directed onto the detector means, to a condition or conditions in which the radiation is diffused, and means to effect such change in condition.
Thus, any mechanically movable parts are eliminated; it is found that in its diffuse condition the liquid crystal means provides a radiance which is related to the object or scene radiance. The liquid crystal means also destroys the structure of the object or scene within the radiation giving a relatively uniform irradiance on the detector means.
One embodiment ofthe invention is illustrated by way of example with reference to the accompanying drawing.
In this embodiment, a liquid crystal assembly is incorporated in thermal imaging apparatus, the liquid crystal assembly comprising a liquid crystal layer 1.
sandwiched between two germanium discs 2 and 3 respectively. In the normal quiescent condition, the layer 1 is clear. When a voltage is applied across the discs, the layer 1 becomes diffuse to an extent depending upon the magnitude of the voltage.
The imaging apparatus itself comprises focussing means 4 by means of which incoming radiation from
an object or scene is focussed onto detector means 5, for example an array of detector elements. The detector mears is mounted within a vacuum encapsulation 6 and cooled to its operating temperature by cooling means 7.
Awindowisformed in the encapsulation 6; this, when of germanium or similar material, thus can provide one layer2 of the liquid crystal sandwich. The liquid crystal layer 1 and its two sandwiching layers 2 and 3 lie external to the encapsulation 6 but between it and the focussing means 4. Leads 8,9 allow a voltage to be applied across the germanium discs 2 and 3 of the liquid crystal sandwich.
A suitable liquid crystal layer 1 is of a thickness of several wavelengths of the radiation to be detected. It has a high transmission to those radiation wavelengths forwhich the apparatus is to be used when in the quiescent condition.
When, periodically, avoltage is applied, the layer 1 scatters the radiation to an extent depending on the magnitude ofthe voltage. If desired, more than one voltage level may be used to effect different degrees of scattering sothatthe gains of the channels of any amplifier means receiving the outputs ofthe detector means may be matched as well as having the D.C.
output levels restored.
Although the sandwiching layers 2 and 3 have been specified as being formed of germanium and are therefore electrically conductive, other infra red transmissive materials can be used. Naturally, ifthese, like zinc sulphide and sapphire, are not electrically conductive, then some form of treatment is necessary to render them so.
1. Imaging apparatus, having detector means upon which electromagnetic radiation from a source is directed and which detector means requires to be periodically exposed to a predetermined radiance level, including liquid crystal means located in between the detector means and the source, the liquid crystal means being changeable from a condition in which there is substantially no effect on the radiation directed into the detector means, to a condition or conditions in which the radiation is diffused, and meansto effect such change in condition.
2. Imaging apparatus according to claim 1 wherein the detector means includes a radiation transparent window, the liquid crystal means comprises a liquid crystal layer sandwiched between two radiation transparent layers, and one of said layers comprises the radiation transparent window.
3. Imaging apparatus according to claim 2 wherein the transparent layers are formed of germanium.
4. Imaging apparatus substantially as described with reference to the accompanying drawing.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (4)
1. Imaging apparatus, having detector means upon which electromagnetic radiation from a source is directed and which detector means requires to be periodically exposed to a predetermined radiance level, including liquid crystal means located in between the detector means and the source, the liquid crystal means being changeable from a condition in which there is substantially no effect on the radiation directed into the detector means, to a condition or conditions in which the radiation is diffused, and meansto effect such change in condition.
2. Imaging apparatus according to claim 1 wherein the detector means includes a radiation transparent window, the liquid crystal means comprises a liquid crystal layer sandwiched between two radiation transparent layers, and one of said layers comprises the radiation transparent window.
3. Imaging apparatus according to claim 2 wherein the transparent layers are formed of germanium.
4. Imaging apparatus substantially as described with reference to the accompanying drawing.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8325303 | 1983-09-21 |
Publications (3)
Publication Number | Publication Date |
---|---|
GB8423832D0 GB8423832D0 (en) | 1984-10-24 |
GB2147172A true GB2147172A (en) | 1985-05-01 |
GB2147172B GB2147172B (en) | 1986-11-12 |
Family
ID=10549104
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08423832A Expired GB2147172B (en) | 1983-09-21 | 1984-09-20 | Imaging or like apparatus |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2147172B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0478457A1 (en) * | 1990-09-28 | 1992-04-01 | Commissariat A L'energie Atomique | Solid state image sensor with an integrated noise filter |
WO1999017541A1 (en) * | 1997-09-26 | 1999-04-08 | The Secretary Of State For Defence | Sensor apparatus |
-
1984
- 1984-09-20 GB GB08423832A patent/GB2147172B/en not_active Expired
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0478457A1 (en) * | 1990-09-28 | 1992-04-01 | Commissariat A L'energie Atomique | Solid state image sensor with an integrated noise filter |
FR2667471A1 (en) * | 1990-09-28 | 1992-04-03 | Commissariat Energie Atomique | DEVICE FOR SHOOTING. |
US5216510A (en) * | 1990-09-28 | 1993-06-01 | Commissariat A L'energie Atomique | Imaging device |
WO1999017541A1 (en) * | 1997-09-26 | 1999-04-08 | The Secretary Of State For Defence | Sensor apparatus |
WO1999017542A1 (en) * | 1997-09-26 | 1999-04-08 | The Secretary Of State For Defence | Sensor system |
GB2344247A (en) * | 1997-09-26 | 2000-05-31 | Secr Defence | Sensor system |
GB2344246A (en) * | 1997-09-26 | 2000-05-31 | Secr Defence | Sensor apparatus |
GB2344246B (en) * | 1997-09-26 | 2001-12-05 | Secr Defence | Sensor apparatus |
US6396045B1 (en) | 1997-09-26 | 2002-05-28 | Qinetiq Limited | Sensor apparatus |
US6414294B1 (en) | 1997-09-26 | 2002-07-02 | Qinetiq Limited | Sensor system |
GB2344247B (en) * | 1997-09-26 | 2002-08-07 | Secr Defence | Sensor system |
Also Published As
Publication number | Publication date |
---|---|
GB2147172B (en) | 1986-11-12 |
GB8423832D0 (en) | 1984-10-24 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920920 |