Security sensor having disturbance detecting capability

• US 6,469,625 B1
• Filed: 02/06/2001
• Issued: 10/22/2002
• Est. Priority Date: 02/18/2000
• Status: Expired due to Fees

• Current Assignee: Optex Company Limited (OPTEX GROUP Co., Ltd.)
• Original Assignee: Optex Company Limited (OPTEX GROUP Co., Ltd.)
• Inventors: Tomooka, Hiroyuki
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Previl, Daniel
• Application Number:
  US09/777,806
• Time in Patent Office: 623 Days
• Field of Search: 340/556, 340/555, 340/552, 340/551, 340/541, 340/545.3, 340/561, 340/565, 340/567, 250/342, 250/341, 250/341.8, 250/DIG.1
• US Class Current: 340/556
• CPC Class Codes: G08B 29/046 prevention of tampering with detection circuits

Abstract

A security sensor 1 having a disturbance detecting capability capable of detecting the presence of an obstacle 8 purposefully applied to the sensor 1 in an attempt to fool or tamper the sensor 1 includes a carrier body A having an infrared sensor element 4, an incident side enclosure 5, such as a lens defining a detection area B, mounted on the carrier body A, a light projecting element 11 for projecting a disturbance detecting beam L1 from inside of the incident side enclosure 5 towards the incident side enclosure 5, a light receiving element 12 for receiving the disturbance detecting beam L1 reflected from the incident side enclosure 5, and a detecting circuit 15 for detecting a presence or absence of the obstacle 8 on the incident side enclosure 5, based on an amount of light received by the light receiving element 12. A multiplicity of projections 7 are formed on an outer surface of the incident side enclosure 5 so as to define a multiplicity of gaps between the obstacle 8 and the outer surface of the incident side enclosure 5, when the obstacle 8 is applied to the outer surface of the incident side enclosure 5.

Claims

1. A security sensor having a disturbance detecting capability, which comprises:

a carrier body having an infrared sensor element;

an incident side enclosure mounted on the carrier body, said incident side enclosure comprising a lens that defines at least one detection area for the infrared sensor element;

a light projecting element for projecting a disturbance detecting beam from inside of the incident side enclosure towards an inner surface of the detection area of said incident side enclosure;

a light receiving element for receiving at least a portion of the disturbance detecting beam reflected from the incident side enclosure;

a detecting circuit for detecting a presence or absence of an obstacle, applied to the incident side enclosure, based on an amount of light received by the light receiving element; and

a multiplicity of projections integrally formed and spaced apart on an outer surface of the incident side enclosure and positioned in an incident area aligned with the infrared sensor element so as to define a multiplicity of gaps between the obstacle and the outer surface of the incident side enclosure, when the obstacle is applied to the outer surface of the incident side enclosure.

2. The security sensor as claimed in claim 1, further comprising a light guide member for guiding the disturbance detecting beam reflected from the obstacle towards the light receiving element.

3. The security sensor as claimed in claim 2, wherein said light guide member is positioned at a location offset from the incident area aligned with the infrared sensor element.

4. The security sensor as claimed in claim 1, wherein the carrier body includes a printed circuit board, said infrared sensor element and said light projecting elements being mounted on the printed circuit board.

5. The security sensor as claimed in claim 1, wherein said incident side enclosure comprises a lens having an inner surface formed with a Fresnel lens having rugged lens elements each having a step and wherein the projections are positioned on an outer surface of the lens at respective locations aligned with the steps of the rugged lens elements of the Fresnel lens.

6. The security sensor as claimed in claim 1, wherein said carrier body comprises a base for supporting the infrared sensor element, the light projecting element and the light receiving element mounted thereon, and a casing fitted to the base;

wherein the lens is fitted to the casing, said carrier body and said lens cooperating to enclose the infrared sensor element, the light projecting element and the light receiving element; and

wherein the projections are formed on a center portion of the lens.

7. A security sensor having a disturbance detecting capability, which comprises:

a carrier body having an infrared sensor element;

an incident side enclosure mounted on the carrier body, said incident side enclosure comprising a cover that covers an incident surface area of the infrared sensor element;

a projecting element for projecting a disturbance detecting beam from inside of the incident side enclosure towards an inner surface of the detection area of the incident side enclosure;

a receiving element for receiving at least a portion of the disturbance detecting beam reflected from the incident side enclosure;

a detecting circuit for detecting a presence or absence of an obstacle, applied to the incident side enclosure, based on an amount of detecting beam received by the receiving element; and

a multiplicity of projections integrally formed on and extending from an outer surface of the incident side enclosure, the projections are positioned in an incident area aligned with the infrared sensor element and spaced apart from each other so as to define a multiplicity of gaps between any obstacle and the outer surface of the incident side enclosure, when the obstacle is applied to the outer surface of the incident side enclosure.

8. The security sensor as claimed in claim 7, further comprising a guide member for guiding the disturbance detecting beam reflected from the obstacle towards the receiving element.

9. The security sensor as claimed in claim 8, wherein said guide member is positioned at a location offset from an incident area aligned with the infrared sensor element.

10. The security sensor as claimed in claim 7, wherein the carrier body includes a printed circuit board, said infrared sensor element and said projecting element being mounted on the printed circuit board.

11. The security sensor as claimed in claim 7, wherein the carrier body comprises a base for supporting the sensor element, the projecting element and the receiving element mounted thereon, and the cover is fitted to the base so as to enclose the sensor element, the projecting element and the receiving element.

12. A security sensor system comprising:

a detector element for detecting infrared radiation representative of an intruder in a target area;

a cover member extending over the detector element and having an incident surface transmissive of the infrared radiation from the target area;

a plurality of projections formed on and extending outward from the incident surface of the cover member, while permitting the infrared radiation to pass between the projections to contact the detector element;

a source of a disturbance detecting beam directed at an interior surface of the cover member having the projections; and

a disturbance detecting beam detector unit positioned under the cover member to receive a portion of the disturbance detecting beam that will vary depending upon a presence of any obstacle placed over the plurality of projections on the incident surface whereby the plurality of projections will provide gaps between any obstacle and the adjacent incident surface of the cover member to reflect the disturbance detecting beam toward the disturbance detecting beam detector, wherein the cover member includes a Fresnel lens having lens elements each having a step and wherein the projections are positioned at respective locations in alignment with the steps of the lens elements.

13. The security sensor system of claim 12 wherein the cover member includes a Fresnel lens having lens elements each having a step and wherein the projections are positioned at respective locations in alignment with the steps of the lens elements.