Infrared detecting apparatus

• US 5,055,685 A
• Filed: 12/01/1989
• Issued: 10/08/1991
• Est. Priority Date: 12/01/1989
• Status: Expired due to Term

• Current Assignee: Optex Company Limited (OPTEX GROUP Co., Ltd.)
• Original Assignee: Optex Company Limited (OPTEX GROUP Co., Ltd.)
• Inventors: Sugimoto, Tadashi, Shoji, Yasuo, Iwasawa, Masashi
• Primary Examiner(s): Fields, Carolyn E.
• Assistant Examiner(s): BEYER, JAMES
• Application Number:
  US07/444,755
• Time in Patent Office: 676 Days
• Field of Search: 250/349, 250/342, 250/338.1, 250/338.3
• US Class Current: 250/342
• CPC Class Codes: G01J 1/04 Optical or mechanical part supplementary adjustable parts
• CPC Class Codes: G01J 5/07 Arrangements for adjusting the solid angle of collected radiation, e.g. adjusting or orienting field of view, tracking position or encoding angular position optical collimating elements G01J5/0806
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0802 Optical filters
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/0846 having multiple detectors for performing different types of detection, e.g. using radiometry and reflectometry channels
• CPC Class Codes: G01J 5/0875 Windows; Arrangements for fastening thereof
• CPC Class Codes: G01J 5/0893 Arrangements to attach devices to a pyrometer, i.e. attaching an optical interface; Spatial relative arrangement of optical elements, e.g. folded beam path G01J5/049 takes precedence
• CPC Class Codes: G08B 13/193 using focusing means
• CPC Class Codes: Y10S 250/01 Passive intrusion detectors

Abstract

An infrared detecting apparatus which includes an infrared filter which intercepts visible light and transmits infrared rays having at least two infrared detecting elements for receiving infrared rays transmitted through the filter and converting the received infrared rays into an electric signal and an electronic circuit which amplifies the difference signal supplied from the infrared detecting elements so that the relative positional relationship between the infrared detecting elements and the infrared filter which allows for the solid angle extending from an arbitrary point on the infrared filter to the peripheral edge of the infrared detecting element'"'"'s receiving surface to be not greater or less than a specific range.

Claims

1. An infrared detecting apparatus comprising:

at least two infrared detecting elements for converting infrared rays into electric signals;

an electronic circuit for amplifying a difference signal due to a difference between output signals from two of said at least two infrared detecting elements;

an infrared filter for transmitting only infrared rays to said at least two infrared detecting elements, said infrared filter being positioned so that solid angles extending from an arbitrary point on the infrared filter to the peripheral edges of the at least two detecting elements are not larger than 1/(8π

) steradian, said solid angles extending from an arbitrary point on the infrared filter to the peripheral edges of the at least two detecting elements for keeping said difference signal lower than a predetermined level when said at least two infrared detecting elements are irradiated by secondary infrared rays generated when said infrared filter is locally heated by being irradiated by a beam of visible light.

3. An infrared detecting apparatus as set forth in claim 1 or 2, wherein

the at least two infrared detecting elements and the electronic circuit are housed in a shield case made of a conductive material having a light receiving port for said at least two infrared detecting element,

said light receiving port is sealed by the infrared filter, and

said infrared filter is made of a conductive material.

4. An infrared detecting apparatus as set forth in claim 1 or 2, wherein said at least two infrared detecting elements are housed in an element housing space in the form of a concave formed in the outer surface of a housing case, and an opening of said element housing space is sealed by the infrared filter.

5. An infrared detecting apparatus as set forth in claim 1 or 2, wherein

said at least two infrared detecting element are housed in a shell having a receiving window for receiving infrared rays,

said shell is protected, at the outer periphery thereof, by a protective member which has an opening opposite to said receiving window and which is made of a material different from that of said shell, and

said opening is sealed by the infrared filter.

2. An infrared detecting apparatus comprising:

at least two infrared detecting elements for converting infrared rays into electric signals;

an electronic circuit for amplifying a difference signal due to a difference between output signals from two of said at least two infrared detecting elements;

an infrared filter for transmitting only infrared rays to said at least two infrared detecting elements, said infrared filter being positioned so that the distance between said infrared filter and the surfaces of said at least two infrared detecting elements is not less than 2 mm, said distance between said infrared filter and the surfaces of said at least two infrared detecting elements for keeping said difference signal lower than a predetermined level when said at least two infrared detecting elements are irradiated by secondary infrared rays generated when said infrared filter is locally heated by being irradiated by a beam of visible light.