GB1401532A - Light responsive circuit arrangement - Google Patents
Light responsive circuit arrangementInfo
- Publication number
- GB1401532A GB1401532A GB3542772A GB3542772A GB1401532A GB 1401532 A GB1401532 A GB 1401532A GB 3542772 A GB3542772 A GB 3542772A GB 3542772 A GB3542772 A GB 3542772A GB 1401532 A GB1401532 A GB 1401532A
- Authority
- GB
- United Kingdom
- Prior art keywords
- photodiode
- output
- current
- feedback
- logarithmically related
- 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.)
- Expired
Links
- 230000005855 radiation Effects 0.000 abstract 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract 1
- 230000000694 effects Effects 0.000 abstract 1
- 229910052710 silicon Inorganic materials 0.000 abstract 1
- 239000010703 silicon Substances 0.000 abstract 1
- 230000003595 spectral effect Effects 0.000 abstract 1
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06G—ANALOGUE COMPUTERS
- G06G7/00—Devices in which the computing operation is performed by varying electric or magnetic quantities
- G06G7/12—Arrangements for performing computing operations, e.g. operational amplifiers
- G06G7/24—Arrangements for performing computing operations, e.g. operational amplifiers for evaluating logarithmic or exponential functions, e.g. hyperbolic functions
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/44—Electric circuits
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B17/00—Details of cameras or camera bodies; Accessories therefor
- G03B17/02—Bodies
- G03B17/06—Bodies with exposure meters or other indicators built into body but not connected to other camera members
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Mathematical Physics (AREA)
- Theoretical Computer Science (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Software Systems (AREA)
- Computer Hardware Design (AREA)
- Radiation Pyrometers (AREA)
- Photometry And Measurement Of Optical Pulse Characteristics (AREA)
Abstract
1401532 Photo-detector circuits TEXAS INSTRUMENTS Ltd 28 July 1972 35427/72 Heading G1A [Also in Division H3] A logarithmic output photo-detector comprises a photodiode connected between a reference potential and the input of a D.C. amplifier the output of which is connected to a logarithmic element producing a feedback current and a logarithmically related output voltage, the feedback current being applied to the input of the amplifier in such a sense as to maintain substantially zero voltage across the photodiode whereby the output voltage is logarithmically related to the intensity of the light incident on the photodiode. As shown, a commercial I.C. operational amplifier OAI provided with a high impedance discrete component differential input stage (see Division H3) is connected to a photodiode D1 and is provided with a negative feedback path so that the diode is connected between earth and a virtual earth and operates with zero voltage across it resulting in a linear relationship between light intensity and output current. The current produced by the photodiode flows through the feedback loop and passes through transistor VT7. A second, matched transistor VT8 has its base connected to its collector and is provided with a high value load resistor so that it draws substantially constant current. Since the differential base voltage of the transistor pair VT7, 8 is logarithmically related to the ratio of the collector currents and the circuit is arranged so that VT8 draws constant current and the base of VT8 is earthed, it follows that the base voltage of VT8 is logarithmically related to the collector current of VT7 and hence to the photodiode current. The logarithmic output is applied to a second operational amplifier OA2 which has a feedback loop containing a temperature sensitive silicon resistor in series with a normal resistor proportioned to offset the temperature dependance of the logarithmic converter transistors. The output of op amp OA2 is applied to a meter Ml which provides a reading logarithmically related to the intensity of the radiation falling on the photodiode D1. The detector may be used as a densitometer with a linear density scale. A reference density level may be set by means of a potentiometer P1 in the feedback circuit of the output amplifier OA2. The spectral response is similar to that of the human eye so that the detector may be used for colour analysis, but an IR filter may be necessary to reduce the effects of relatively high levels of IR radiation. The meter may be calibrated in terms of photographic exposure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3542772A GB1401532A (en) | 1972-07-28 | 1972-07-28 | Light responsive circuit arrangement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3542772A GB1401532A (en) | 1972-07-28 | 1972-07-28 | Light responsive circuit arrangement |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1401532A true GB1401532A (en) | 1975-07-16 |
Family
ID=10377591
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB3542772A Expired GB1401532A (en) | 1972-07-28 | 1972-07-28 | Light responsive circuit arrangement |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1401532A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2437014A1 (en) * | 1978-09-25 | 1980-04-18 | Agfa Gevaert Ag | PHOTOGRAPHIC APPARATUS WITH ADJUSTMENT DEVICE CAPABLE OF BEING CONTROLLED USING A DRIVING MEMBER |
| GB2171512A (en) * | 1985-02-21 | 1986-08-28 | Perkin Elmer Corp | Detector preamplifier |
| EP1182435A2 (en) * | 2000-08-18 | 2002-02-27 | Visteon Global Technologies, Inc. | Light sensor system and method for detecting ambient light |
-
1972
- 1972-07-28 GB GB3542772A patent/GB1401532A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2437014A1 (en) * | 1978-09-25 | 1980-04-18 | Agfa Gevaert Ag | PHOTOGRAPHIC APPARATUS WITH ADJUSTMENT DEVICE CAPABLE OF BEING CONTROLLED USING A DRIVING MEMBER |
| GB2171512A (en) * | 1985-02-21 | 1986-08-28 | Perkin Elmer Corp | Detector preamplifier |
| EP1182435A2 (en) * | 2000-08-18 | 2002-02-27 | Visteon Global Technologies, Inc. | Light sensor system and method for detecting ambient light |
| EP1182435A3 (en) * | 2000-08-18 | 2004-03-24 | Visteon Global Technologies, Inc. | Light sensor system and method for detecting ambient light |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |