WO2001039153A1 - An illumination source - Google Patents
An illumination source Download PDFInfo
- Publication number
- WO2001039153A1 WO2001039153A1 PCT/GB2000/004459 GB0004459W WO0139153A1 WO 2001039153 A1 WO2001039153 A1 WO 2001039153A1 GB 0004459 W GB0004459 W GB 0004459W WO 0139153 A1 WO0139153 A1 WO 0139153A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- camera
- fibre
- optical fibre
- illumination source
- radiation
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/052—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed
- G08G1/054—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed photographing overspeeding vehicles
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/262—Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4298—Coupling light guides with opto-electronic elements coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers
Definitions
- the invention relates to an illumination source for illuminating a scene to be captured by a camera, and to a camera having associated therewith such an illumination source.
- the invention is particularly, but not exclusively, applicable to surveillance cameras which may be used for viewing vehicle number plates in covert surveillance operations at night.
- UK-B-2248994 discloses an apparatus for viewing a vehicle number plate in covert night-surveillance operations, the apparatus comprising an illuminator for emitting a series of high peak power pulses of infrared light, outside the range visible to the human eye, the illuminator being powered by a pulsed current of at least ten times the continuous rating, and a shuttered camera whose shutter open period is synchronised with the illuminator to receive the pulses of infrared light after reflection from the number plate.
- LEDs light emitting diodes
- a practical device currently manufactured by one of the proprietors of UK-B-2248994. uses an array of LEDs which takes a considerable amount of power, and still has a relatively limited range.
- the invention provides an illumination source for illuminating a scene for capture by a camera, the illumination source comprising a laser diode coupled to one end of a first length of optical fibre for transmitting radiation emitted by the laser diode, the other end of the first length of optical fibre being coupled to one end of a second, mismatched optical fibre formed into a coil, the length of the second optical fibre and the diameter of the coil being such that the radiation emitted from the other end of the second optical fibre is substantially incoherent.
- the first optical fibre may be a single mode fibre, and the second optical fibre a stepped mode fibre. It has been found that, with a radiation wavelength of 880 nm, if the first optical fibre is a short length of 100pm single mode fibre, a ten metre length of 200/230 pm stepped index fibre wound in a coil of about 100mm diameter is sufficient for effective destruction of the effect of coherence in this application. Of course, different lengths of fibre would be appropriate with different radiation wavelengths, different fibre types and sizes, and different coil diameters. Trial and error methods can be used to determine appropriate lengths. Thus, starting with given fibres, the tightness of coiling can be varied until sufficient incoherence is obtained for a given length of fibre. Alternatively, the length of fibre may be altered for a given coil diameter.
- the laser diode may emit radiation in the infrared range. This has the advantage that it is not visible, and consequently will not alert anyone to the fact that the taking of a photograph has occurred, thereby allowing covert surveillance.
- An additional advantage is that, because the arrangement of the present invention allows the use of low power radiation, the risk of anyone detecting the presence of this radiation is reduced as compared with the prior art. This is possible because of the high efficiency of use of the illumination.
- the invention further provides a surveillance camera including such an illumination source.
- the surveillance camera may comprise a camera body and a lens housing, said other end of the second optical fibre being located on the lens housing such that the radiation is transmitted parallel to the optical axis of the lens, and said other end of the second optical fibre being located close to the optical axis.
- the illumination source may be combined with an existing surveillance camera with a minimum of changes to the basic camera. Consequently, the advantages of the invention can be realised with minimal changes to existing cameras.
- a television camera 1 has a camera body 2 and a lens housing 3.
- An illumination source comprising a laser diode 4 is mounted on the side of the camera by any convenient means.
- a short length of optical fibre 5 is coupled to the laser diode, and is provided with a connector 6.
- the connector 6 mates with a further connector 7 that is attached to a length of optical fibre 8.
- the optical fibres 5 and 8 are mismatched, so that optical interference is produced in the fibre 8.
- the fibre 5 may, for example, be a 100pm single mode fibre, while the fibre 8 may be a 200/230pm stepped index fibre ten metres long and formed into a coil 9 of approximately 100mm diameter.
- the fibre 8 is fixed to the lens housing 3 with its free, or remote, end 10 arranged parallel to the optical axis of the lens.
- the laser diode 4 preferably emits radiation in the infrared wavelengths when the camera and illumination source are intended for use in covert surveillance. This is, of course, not necessary if the surveillance is not intended to be covert, when radiation in the visible wavelengths could be used.
- a suitable infra red wavelength laser diode is that sold by Opto Power Corporation under the type number OPC-AOOl-mmm-FC/1 00.
- the fibre 8 is attached to the outer surface of the lens housing 3 at a point close to the end of the housing, and the remote portion of that fibre is arranged substantially parallel to the optical axis of the lens. Consequently, the radiation emitted by the laser diode 4 will travel along the optical axis and, when it encounters a retro-reflective number plate, will be reflected back into the lens, and hence enter the camera through the shutter to provide maximum illumination to the camera detector (for example film or a CCD detector in the case of a CCTN camera).
- the camera detector for example film or a CCD detector in the case of a CCTN camera.
- the laser drive electronics so that the laser is turned on only when required, thus prolonging the laser life.
- the cameras used in vehicle surveillance operations which are typically mounted on gantries above motorways or other major roads or on roadside pylons, are usually operated at fast shutter speeds (1/1000th of a second is normal), it is useful to pulse the laser at 1/100th of a second synchronised to the camera shutter. This both maximises the laser life and minimises the total power requirements. This may be of importance when the camera is situated at a remote location, where easy access to a main power supply is not available.
- the particular form of the camera is not part of the present invention, which may be applied to many different types of camera.
- the invention is particularly useful for roadside CCTV type cameras, where the possibility of synchronising the switching of the laser diode with the shutter opening can be exploited for minimising the electrical power requirements.
- Such cameras mounted at roadsides already include an electrical signal for operating the shutter, often involving the use of a proximity detector for detecting the presence of an object (vehicle) to be photographed, or a vehicle speed sensor, and that signal or one derived from it can be used to pulse the laser.
- the embodiment shown in the drawing is particularly convenient for fitting to existing camera designs, since it merely needs to be fixed mechanically to the exterior of the camera with some access to signals within the camera, and thus requires a minimum of modification to the camera.
- a completely redesigned camera could allow the fibre to be carried within the camera housing. In that case, the fibre could be located even closer to the optical axis with the radiation shining through the lens rather than from alongside it, thereby increasing the efficiency of the illumination source still further.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Studio Devices (AREA)
- Closed-Circuit Television Systems (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU15339/01A AU1533901A (en) | 1999-11-24 | 2000-11-23 | An illumination source |
EP00977701A EP1234291A1 (en) | 1999-11-24 | 2000-11-23 | An illumination source |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9927623.0 | 1999-11-24 | ||
GBGB9927623.0A GB9927623D0 (en) | 1999-11-24 | 1999-11-24 | Illumination source |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2001039153A1 true WO2001039153A1 (en) | 2001-05-31 |
Family
ID=10864952
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB2000/004459 WO2001039153A1 (en) | 1999-11-24 | 2000-11-23 | An illumination source |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1234291A1 (en) |
AU (1) | AU1533901A (en) |
GB (1) | GB9927623D0 (en) |
WO (1) | WO2001039153A1 (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008037049A1 (en) * | 2006-09-25 | 2008-04-03 | Tony Mayer | Micro-diffractive surveillance illuminator |
US8842182B2 (en) | 2009-12-22 | 2014-09-23 | Leddartech Inc. | Active 3D monitoring system for traffic detection |
US8908159B2 (en) | 2011-05-11 | 2014-12-09 | Leddartech Inc. | Multiple-field-of-view scannerless optical rangefinder in high ambient background light |
US9235988B2 (en) | 2012-03-02 | 2016-01-12 | Leddartech Inc. | System and method for multipurpose traffic detection and characterization |
US9378640B2 (en) | 2011-06-17 | 2016-06-28 | Leddartech Inc. | System and method for traffic side detection and characterization |
US10488492B2 (en) | 2014-09-09 | 2019-11-26 | Leddarttech Inc. | Discretization of detection zone |
USRE49342E1 (en) | 2007-12-21 | 2022-12-20 | Leddartech Inc. | Distance detection method and system |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4011403A (en) * | 1976-03-30 | 1977-03-08 | Northwestern University | Fiber optic laser illuminators |
US4981333A (en) * | 1989-09-27 | 1991-01-01 | Fotec, Inc. | Universal launch cable assembly and integrated idealized light source system using same |
GB2248994A (en) * | 1990-08-17 | 1992-04-22 | Secr Defence | Surveillance apparatus for viewing vehicle number-plates |
US5684642A (en) * | 1994-02-22 | 1997-11-04 | Mitsubishi Denki Kabushiki Kaisha | Optical transmission system and light radiating method |
-
1999
- 1999-11-24 GB GBGB9927623.0A patent/GB9927623D0/en not_active Ceased
-
2000
- 2000-11-23 EP EP00977701A patent/EP1234291A1/en not_active Withdrawn
- 2000-11-23 AU AU15339/01A patent/AU1533901A/en not_active Abandoned
- 2000-11-23 WO PCT/GB2000/004459 patent/WO2001039153A1/en not_active Application Discontinuation
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4011403A (en) * | 1976-03-30 | 1977-03-08 | Northwestern University | Fiber optic laser illuminators |
US4981333A (en) * | 1989-09-27 | 1991-01-01 | Fotec, Inc. | Universal launch cable assembly and integrated idealized light source system using same |
GB2248994A (en) * | 1990-08-17 | 1992-04-22 | Secr Defence | Surveillance apparatus for viewing vehicle number-plates |
US5684642A (en) * | 1994-02-22 | 1997-11-04 | Mitsubishi Denki Kabushiki Kaisha | Optical transmission system and light radiating method |
Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008037049A1 (en) * | 2006-09-25 | 2008-04-03 | Tony Mayer | Micro-diffractive surveillance illuminator |
JP2010504596A (en) * | 2006-09-25 | 2010-02-12 | トニー・メイアー | Micro diffraction monitoring illumination system |
US9202373B2 (en) | 2006-09-25 | 2015-12-01 | Bosch Security Systems Bv | Micro-diffractive surveillance illuminator |
USRE49342E1 (en) | 2007-12-21 | 2022-12-20 | Leddartech Inc. | Distance detection method and system |
US8842182B2 (en) | 2009-12-22 | 2014-09-23 | Leddartech Inc. | Active 3D monitoring system for traffic detection |
US8908159B2 (en) | 2011-05-11 | 2014-12-09 | Leddartech Inc. | Multiple-field-of-view scannerless optical rangefinder in high ambient background light |
USRE47134E1 (en) | 2011-05-11 | 2018-11-20 | Leddartech Inc. | Multiple-field-of-view scannerless optical rangefinder in high ambient background light |
USRE48763E1 (en) | 2011-05-11 | 2021-10-05 | Leddartech Inc. | Multiple-field-of-view scannerless optical rangefinder in high ambient background light |
US9378640B2 (en) | 2011-06-17 | 2016-06-28 | Leddartech Inc. | System and method for traffic side detection and characterization |
US9235988B2 (en) | 2012-03-02 | 2016-01-12 | Leddartech Inc. | System and method for multipurpose traffic detection and characterization |
USRE48914E1 (en) | 2012-03-02 | 2022-02-01 | Leddartech Inc. | System and method for multipurpose traffic detection and characterization |
US10488492B2 (en) | 2014-09-09 | 2019-11-26 | Leddarttech Inc. | Discretization of detection zone |
Also Published As
Publication number | Publication date |
---|---|
AU1533901A (en) | 2001-06-04 |
EP1234291A1 (en) | 2002-08-28 |
GB9927623D0 (en) | 2000-01-19 |
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