Pyroelectric infrared sensor

• US 4,973,843 A
• Filed: 08/29/1989
• Issued: 11/27/1990
• Est. Priority Date: 08/30/1988
• Status: Expired due to Term

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Sawada, Shyzi, Nishio, Muneharu, Ito, Satoru, Murata, Michihiro
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Eisenberg, Jacob
• Application Number:
  US07/400,471
• Time in Patent Office: 455 Days
• Field of Search: 250/338.3, 250/338.4, 250/338.2, 250/338.1
• US Class Current: 250/338.3
• CPC Class Codes: G01J 5/34 using capacitors, e.g. pyroelectric capacitors
• CPC Class Codes: G08B 13/191 using pyroelectric sensor means
• CPC Class Codes: H10N 15/10 Thermoelectric devices using thermal change of the dielectric constant, e.g. working above and below the Curie point

Abstract

A pyroelectric sensor senses the infrared rays radiated from the human body and outputs the detected infrared rays as an electric signal. It detects the trespass of somebody on a room and is used for the prevention of crimes and the like. The pyroelectric sensor includes a substrate, an element-pair disposed on the surface of the substrate and an amplification circuit for amplifying the current signals output from the element-pair. The substrate is composed of a material having a thermal conductivity as low as not more than 0.04 cal/cm sec° C. so as to prevent the heat from being released through the substrate. A hole is formed in the substrate. The amplification circuit amplifies the current signals of the element-pair, thereby dispensing with the impedance transformation which is inevitable in the prior art. Thus, the sensitivity of detection is improved and the manufacture of the sensor is facilitated.

Claims

1. A pyroelectric infrared sensor comprising:

a substrate, said substrate comprising a composite material of glass and an epoxy resin; and

an element-pair provided on the surface of said substrate so as to output current signals corresponding to the dose of radiation of infrared rays, said substrate having a material having a thermal conductivity of not more than 0.04 (cal/cm sec°

C.).

2. A pyroelectric infrared sensor according to claim 1, wherein said substrate comprises BaO-SiO₂ -Al₂ O₃ -B₂ O₃ -Cr₂ O₃.

3. A pyroelectric infrared sensor according to claim 1, wherein said substrate is provided with a hole.

4. A pyroelectric infrared sensor according to claim 2, wherein said substrate is provided with a hole.

5. A pyroelectric infrared sensor comprising:

a substrate;

an element-pair provided on the surface of said substrate so as to output current signals corresponding to the dose of radiation of infrared rays, said substrate comprising a material having a thermal conductivity of not more than 0.04 (cal/cm sec°

C.); and

an amplification circuit provided on the surface of said substrate so as to amplify current signals output from said element-pair.

6. A pyroelectric sensor according to claim 5, wherein said amplification circuit includes an operational amplifier for executing current amplification.

7. A pyroelectric infrared sensor according to claim 6, wherein said amplification circuit includes a low pass filter for eliminating high-frequency noise from said current signals output from said element-pair.

8. A pyroelectric infrared sensor according to claim 5, wherein said substrate comprises a composite material of glass and an epoxy resin.

9. A pyroelectric infrared sensor according to claim 6, wherein said substrate comprises a composite material of glass and an epoxy resin.

10. A pyroelectric infrared sensor according to claim 7, wherein said substrate comprises a composite material of glass and an epoxy resin.

11. A pyroelectric infrared sensor according to claim 5, wherein said substrate comprises BaO-SiO₂ -Al₂ O₃ -B₂ O₃ -Cr₂ O₃.

12. A pyroelectric infrared sensor according to claim 6, wherein said substrate comprises BaO-SiO₂ -Al₂ O₃ -B₂ O₃ -Cr₂ O₃.

13. A pyroelectric infrared sensor according to claim 7, wherein said substrate comprises BaO-SiO₂ -Al₂ O₃ -B₂ O₃ -Cr₂ O₃.

14. A pyroelectric infrared sensor according to claim 5, wherein said substrate is provided with a hole.

15. A pyroelectric infrared sensor according to claim 6, wherein said substrate is provided with a hole.

16. A pyroelectric infrared sensor according to claim 7, wherein said substrate is provided with a hole.

17. A pyroelectric infrared sensor according to claim 10, wherein said substrate is provided with a hole.

18. A pyroelectric infrared sensor according to claim 13, wherein said substrate is provided with a hole.