GB1499670A - Detection of degree of opacity in light paths - Google Patents

Detection of degree of opacity in light paths

Info

Publication number
GB1499670A
GB1499670A GB2417874A GB2417874A GB1499670A GB 1499670 A GB1499670 A GB 1499670A GB 2417874 A GB2417874 A GB 2417874A GB 2417874 A GB2417874 A GB 2417874A GB 1499670 A GB1499670 A GB 1499670A
Authority
GB
United Kingdom
Prior art keywords
source
detector
path
mirror
along
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
Application number
GB2417874A
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.)
ENVIRONMENT SEC OF STATE FOR
Original Assignee
ENVIRONMENT SEC OF STATE FOR
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.)
Filing date
Publication date
Application filed by ENVIRONMENT SEC OF STATE FOR filed Critical ENVIRONMENT SEC OF STATE FOR
Priority to GB2417874A priority Critical patent/GB1499670A/en
Publication of GB1499670A publication Critical patent/GB1499670A/en
Expired legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
    • G01N21/538—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke for determining atmospheric attenuation and visibility

Landscapes

  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

1499670 Photo-electric detection of fog, intruders &c. ENVIRONMENT SECRETARY OF STATE FOR THE 2 June 1975 [31 May 1974] 24178/74 Heading G1A An apparatus which monitors the transmission of light along a path, e.g. to detect fog, smoke or an intruder in the path, has a light source 10, Fig. 1, which transmits light along the path to a concave mirror 12 and thence to a detector 14, the output of which is compared with that of a detector 17 receiving light from the source along a reference path. The mirror has its centre of curvature at point 33 where its axis intersects a line joining lenses 11 and 13; if the apparatus is supported at 33 this geometry minimizes the effects of distortion due, e.g., to wind, fatigue or temperature changes. If the lenses are not used, the centre of curvature is at the intersection of the mirror axis and a line joining source 10 and detector 14. Baffles 18, 19, 20 trap dirt and prevent entry of external light; the mirror and lenses are heated to prevent condensation. The detectors are of similar type and are close together, to minimize temperature effects. The source may be a Ga As P diode, which can be amplitude modulated; in this case it is supplied with current via a PTC thermistor so that ambient temperature does not affect its brightness, and the signals from the detectors, which are balanced in the absence of fog &c., are subtracted and phase detected against the source current to drive a visibility indicator, or to give a visual or audible alarm when visibility drops to a pre-set level, Fig. 2, (not shown). The reference path to detector 17 may be along an optical fibre 16.
GB2417874A 1975-06-02 1975-06-02 Detection of degree of opacity in light paths Expired GB1499670A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB2417874A GB1499670A (en) 1975-06-02 1975-06-02 Detection of degree of opacity in light paths

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2417874A GB1499670A (en) 1975-06-02 1975-06-02 Detection of degree of opacity in light paths

Publications (1)

Publication Number Publication Date
GB1499670A true GB1499670A (en) 1978-02-01

Family

ID=10207651

Family Applications (1)

Application Number Title Priority Date Filing Date
GB2417874A Expired GB1499670A (en) 1975-06-02 1975-06-02 Detection of degree of opacity in light paths

Country Status (1)

Country Link
GB (1) GB1499670A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4041363A1 (en) * 1990-12-20 1992-07-02 Hermann Gmbh Co Heinrich Transparent object detection arrangement for moving glass bottles - has two light barriers inclined at acute angle with logic circuit for combining their output signals
DE4408294A1 (en) * 1994-03-11 1995-09-21 Sick Optik Elektronik Erwin Reflection light barrier for identifying objects within range covered by beam
DE4430778A1 (en) * 1994-08-30 1996-03-07 Sick Optik Elektronik Erwin Coupling tube for light barrier sensor
CN113168752A (en) * 2018-10-15 2021-07-23 庞巴迪运输有限公司 Smoke detector for the segmented detection of smoke and vehicle having a smoke detector

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4041363A1 (en) * 1990-12-20 1992-07-02 Hermann Gmbh Co Heinrich Transparent object detection arrangement for moving glass bottles - has two light barriers inclined at acute angle with logic circuit for combining their output signals
DE4408294A1 (en) * 1994-03-11 1995-09-21 Sick Optik Elektronik Erwin Reflection light barrier for identifying objects within range covered by beam
DE4430778A1 (en) * 1994-08-30 1996-03-07 Sick Optik Elektronik Erwin Coupling tube for light barrier sensor
US5748816A (en) * 1994-08-30 1998-05-05 Sick Ag Optical cavity for exclusively receiving light parallel to an optical axis
DE4430778C2 (en) * 1994-08-30 2000-01-27 Sick Ag Tube
CN113168752A (en) * 2018-10-15 2021-07-23 庞巴迪运输有限公司 Smoke detector for the segmented detection of smoke and vehicle having a smoke detector
CN113168752B (en) * 2018-10-15 2023-09-22 庞巴迪运输有限公司 Smoke detector for the segmented detection of smoke and vehicle with a smoke detector

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Legal Events

Date Code Title Description
PS Patent sealed
PCNP Patent ceased through non-payment of renewal fee