Infrared sensor operable without cooling

• US 5,034,608 A
• Filed: 09/08/1989
• Issued: 07/23/1991
• Est. Priority Date: 09/08/1989
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Tavrow, Lee S., Flynn, Anita M., Brooks, Rodney A.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Glick, Edward J.
• Application Number:
  US07/404,732
• Time in Patent Office: 683 Days
• Field of Search: 901/1, 901/46, 901/47, 357/24 LR, 357/28, 357/30 B, 357/30 G, 357/30 E, 250/338.2, 250/338.4, 250/333, 250/211 J, 250/211 R, 250/334, 250/332, 250/338.1, 25/338.3
• US Class Current: 250/338.3
• CPC Class Codes: G01J 5/34 using capacitors, e.g. pyroelectric capacitors
• CPC Class Codes: H01L 27/14881 of the hybrid type
• 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

An infrared sensor operable without cooling and thus usable at room temperature comprises a substrate supporting thin films of pyroelectric material and switched capacitor control circuitry. The control circuitry compares the absolute capacitance of a reference thin film to that of a sensor thin film, thereby sensing infrared radiation without the use of a chopper device. The reference thin film is thermally coupled to the substrate, and the sensor thin film is thermally insulated form the substrate. To increase the fill factor, the sensor thin film is placed directly above the control circuitry. In another apsect, the sensor is adpated to sense visible and infrared light by adding a CCD sensor and appropriate control circuitry to the substrate.

Claims

1. An infrared sensor comprising

a supporting substrate,

a thermally insulating layer formed on said substrate,

a sensor thin film comprising pyroelectric material formed on said thermally insulating layer and thermally insulated from said substrate,

a reference thin film comprising pyroelectric material thermally coupled to said substrate, and

pyroelectric signal sensing circuitry for comparing the capacitance of said reference thin film and said sensor thin film.

2. The sensor of claim 1 wherein said pyroelectric signal sensing circuitry is formed in said substrate.

3. The sensor of claim 2 adapted for infrared and visible light detection, further comprising

a visible-light sensor comprising a charge coupled device formed in said substrate, and

CCD signal sensing circuitry formed in said substrate for detecting and amplifying electric signals from said visible-light sensor,

wherein said thermally insulating layer and said sensor thin film are disposed over said pyroelectric and CCD signal sensing circuitry, whereby the fill factor of said sensor is increased.

4. The sensor of claim 3 wherein said pyroelectric signal sensing circuitry is connected to said sensor thin film through an opening in said thermally insulating layer.

5. The sensor of claim 1 or 3 wherein said sensor thin film and said reference thin film comprise lead zirconium titanate thin films.

6. The sensor array of claim 1 or 3 wherein said thermally insulating layer is an Aerogel.

7. A combination infrared and visible light room-temperature sensor array comprising

a supporting semiconductor substrate,

a thermally insulating layer formed on said substrate,

an array of infrared-light sensor thin films comprising pyroelectric material formed on said thermally insulating layer and thermally insulated from said substrate,

an array of visible-light sensors comprising charge coupled devices formed in said substrate, the charge coupled devices of said second array interleaved on the surface of said substrate with the pyroelectric thin films of said first array, and

sensing circuitry formed in said substrate for detecting and amplifying electric signals from said infrared and visible-light sensors.

8. The sensor array of claim 7 wherein said thermally insulating layer and said infrared-light sensor thin films are disposed over said sensing circuitry, whereby the fill factor of said sensor array is increased.

9. The sensor array of claim 7 or 8 wherein said sensor thin films comprise lead zirconium titanate thin films.

10. The sensor array of claim 7 or 8 wherein said sensing circuitry is connected to said sensor thin films through openings in said thermally insulating layer.

11. The sensor array of claim 7 or 8 wherein said thermally insulating layer is an Aerogel.