DUAL FIELD OF VIEW INTRUSION DETECTOR

• US 3,829,693 A
• Filed: 10/03/1973
• Issued: 08/13/1974
• Est. Priority Date: 10/03/1973
• Status: Expired due to Term

• Current Assignee: Frank Schwarz
• Original Assignee: Frank Schwarz
• Inventors: Schwarz, Frank
• Primary Examiner(s): Borchelt, Archie R.
• Application Number:
  US05/403,228
• Time in Patent Office: 314 Days
• Field of Search: 250/332,334,338,342,344
• US Class Current: 250/338.1
• CPC Class Codes: G08B 13/193 using focusing means
• CPC Class Codes: Y10S 250/01 Passive intrusion detectors

Abstract

An intrusion detector for detecting movement of bodies radiating in the infrared in a space to be monitored is a combination of an infrared detector such as a thermopile, thermistor, or pyroelectric detector in which a series of all-active thermocouple junctions or pyroelectric detectors connected in opposition is arranged in alignment so that columns of junctions are of alternating polarity, so that an object moving in the space and radiating in the infrared, the image of which moves across the columns, will produce an AC signal which is then amplified and processed electronically to produce an alarm. The electronic circuits, including logic, are well known, and their particular design forms no part of the present invention. Instead of having a single optical system, such as, for example, a germanium lens, imaging the body on the plane of the detector, there are two optical systems, preferably on different focal lengths, one of which images on the front of the detector and the other on the back. The imaging on the back may be reflective, so that intensified images are produced, or it may employ a refracting element for imaging on the back of the detector. In the former case, sensitivity is greatly increased, for example, doubled, and in the second case, which can be used for a detector in long, narrow spaces such as corridors, the sensor can be placed in the middle and will respond to moving bodies on either side of the detector. If it is desired to have a denser coverage of image so that to some extent the spaces between the columns are filled in, in this case the optics is adjusted so that a slightly different field of view is imaged on the back of the detector. This means that a moving object would have to be much smaller or move a lesser distance in order not to strike columns. The sensitivity of course is not increased in such a case.

Claims

1. A detector or detector system for detecting motion of bodies which emit infrared radiation comprising, in combination a. a transparent detector having a plurality of allactive detection elements arranged in series and aligned to form rows and columns, each column having the same polarity and the columns alternating the polarity, and b. two optical collecting systems, one imaging a moving body on one side of the detector, and the other on the opposite side.

2. A motion detector according to claim 1 in which the optical collecting system images a body on front and back of the detector, the body being on one side of the detector whereby the dual images can reinforce responses, or increase the density of fields of view imaging to reduce spacing whereby gaps in the fields of view imaged on particular columns are minimized.

3. A motion detector according to claim 1 in which one of the optical collecting systems images a body on one side of the detector, and the other images a moving body on the opposite side, whereby central location of the detector makes possible adequate signal from a longer, narrow space.

4. A detector according to claim 1 in which the detector elements are thermoelectric junctions forming a thermopile.

5. A detector according to claim 2 in which the detector elements are thermoelectric junctions forming a thermopile.

6. A detector according to claim 3 in which the detector elements are thermoelectric junctions forming a thermopile.

7. A detector according to claim 4 in which the density and spacing of elements are varied so that on one portion of the detector the sensitivity is greater than on others, whereby the maximum density and hence sensitivity may receive images from a direction which is the greatest direction of a particular space to be monitored and hence longest path, and the other zones of lesser density are positioned to receive radiation from shorter paths.

8. A detector according to claim 5 in which the density and spacing of elements are varied so that on one portion of the detector the sensitivity is greatEr than on others, whereby the maximum density and hence sensitivity may receive images from a direction which is the greatest direction of a particular space to be monitored and hence longest path, and the other zones of lesser density are positioned to receive radiation from shorter paths.

9. A detector according to claim 6 in which the density and spacing of elements are varied so that on one portion of the detector the sensitivity is greater than on others, whereby the maximum density and hence sensitivity may receive images from a direction which is the greatest direction of a particular space to be monitored and hence longest path, and the other zones of lesser density are positioned to receive radiation from shorter paths.

10. An instrument according to claim 2 in which the collecting optics imaging on the rear of the detector are laterally somewhat offset to prevent undue attenuation between rows.