Thermal detector and method

• US 5,708,269 A
• Filed: 08/07/1996
• Issued: 01/13/1998
• Est. Priority Date: 08/15/1995
• Status: Expired due to Term

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Raytheon TI Systems, Inc. (Rtx Corporation)
• Inventors: Hanson, Charles M., Meissner, Edward G.
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US08/693,770
• Time in Patent Office: 524 Days
• Field of Search: 250/338.4, 250/338.2, 250/332
• US Class Current: 250/332
• CPC Class Codes: G01J 5/22 Electrical features thereof
• CPC Class Codes: G01J 5/34 using capacitors, e.g. pyroelectric capacitors
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20
• 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 thermal imaging system (10) for providing an image representative of an amount of thermal radiation incident to the system is provided. The system (10) includes a thermal detector (28 or 30) made from a layer of temperature sensitive material forming a first element of a signal-producing circuit (54). The first element (28 or 30) has either a resistance or capacitance value depending on its temperature. The system (10) also includes an integrated circuit substrate (32) having a second element (56 or 58) of the signal-producing circuit (54) complementary and electrically coupled to the first element (28 or 30). The signal-producing circuit (54) may produce an output signal having a amplitude. The amplitude of the output signal is monitored as representing an absolute temperature of the detector (28 or 30) so as to determine the amount of thermal energy incident to the system (10).

Claims

1. A method for producing an image representative of an amount of thermal radiation incident to a thermal imaging system, the method comprising the steps of:

forming a layer of temperature sensitive material as a thermal detector and first element of a signal-producing circuit, the first element having one of a resistance and capacitance value depending on its temperature;

forming a second element of the signal-producing circuit complementary and electrically coupled to the first element;

providing an output signal having an amplitude from the signal-producing circuit, the amplitude of the output signal depending on the value of the first element and representing a temperature of the detector; and

monitoring the amplitude of the output signal of the signal-producing circuit so as to detect a change in the temperature of the thermal detector.

2. The method of claim 1 wherein the first and second elements further comprise a resistor-capacitor (RC) network of a filter circuit.

3. The method of claim 2 wherein the first element is capacitive and the second element is resistive.

4. The method of claim 2 wherein the first element is resistive and the second element is capacitive.

5. The method of claim 2 wherein the filter circuit further comprises one of a high and low pass filter circuit.

6. The method of claim 1 wherein the forming a second element step further comprises forming the second element in an integrated circuit substrate.

7. The method of claim 1 wherein the forming a second element step further comprises forming the second element in an integrated circuit substrate and forming a support structure for providing thermal and electrical isolation between the thermal detector and the substrate.

8. The method of claim 1 wherein the temperature sensitive material further comprises a bolometric resistive material.

9. The method of claim 1 wherein the layer of temperature sensitive material comprises ferroelectric material.

10. The method of claim 1 wherein the layer of temperature sensitive material comprises one of barium strontium titanate, barium titanate, antimony sulfoiodide, vanadium oxide, lead titanate, lead lanthanum zirconium titanate, polysilicon, and amorphous silicon.

11. The method of claim 1 further comprising the step of forming an infrared absorber assembly extending outwardly from the thermal detector for interacting with infrared energy incident thereto and for producing a temperature change in the thermal detector.

12. The method of claim 1 wherein the monitoring step further comprises detecting a change in the amplitude of the output signal.

13. A thermal imaging system for providing an image representative of an amount of thermal radiation incident to the system, the system comprising:

a focal plane array comprising a plurality of thermal detectors, each detector comprising a layer of temperature sensitive material forming a first element of a signal-producing circuit, the first element having one of a resistance and capacitance value depending on its temperature;

an integrated circuit substrate comprising a plurality of second elements, each of the second elements part of one of a plurality of signal-producing circuits and complementary and electrically coupled to an associated first element, each signal-producing circuit operable to produce an output signal having an amplitude; and

wherein the amplitude of each output signal is monitorable as representing an absolute temperature of the detector so as to determine the amount of thermal energy incident to the detector.

14. The system of claim 13 wherein each associated first and second element further comprise a resistor-capacitor (RC) network of a filter circuit.

15. The system of claim 13 further comprising a support structure providing thermal and electrical isolation between the plurality of thermal detectors and the substrate.

16. The system of claim 13 wherein the layer of temperature sensitive material comprises one of barium strontium titanate, barium titanate, antimony sulfoiodide, vanadium oxide, lead titanate, lead lanthanum zirconium titanate, polysilicon, and amorphous silicon.

17. The system of claim 13 further comprising an infrared absorber assembly extending outwardly from the thermal detectors for interacting with infrared energy incident thereto and for producing a temperature change in the thermal detectors.

18. A thermal imaging system for providing an image representative of thermal radiation incident to the system, the system comprising:

an array of thermal detectors, each detector comprising a layer of temperature sensitive material forming a first element of a signal-producing circuit, the first element having at least one of a resistance and capacitance value that depends on its temperature;

an array of the signal-producing circuits, each circuit comprising a second element complementary and electrically coupled to an associated first element, the signal-producing circuit operable to produce an output signal having an amplitude; and

wherein the amplitude of the output signal is monitored as representing an absolute temperature of the detector so as to determine the amount of thermal energy incident to the system.

19. The system of claim 18 wherein the first and second elements further comprise a resistor-capacitor (RC) network of a filter circuit.

20. The system of claim 19 wherein the first element is capacitive and the second element is resistive.

21. The system of claim 19 wherein the first element is resistive and the second element is capacitive.

22. The system of claim 18 wherein the signal-producing circuit further comprises one of a high and low pass filter circuit.

23. The system of claim 18 further comprising a support structure providing thermal and electrical isolation between the thermal detector and the substrate.

24. The system of claim 18 wherein first and second electrical contacts couple to a top and bottom surface of the layer of temperature sensitive material.

25. The system of claim 18 wherein the first and second electrical contacts couple to a first and second side surface of the layer of the temperature sensitive material.

26. The system of claim 18 wherein the layer of temperature sensitive material further comprises barium strontium titanate.

27. The system of claim 18 wherein the layer of temperature sensitive material comprises one of barium strontium titanate, barium titanate, antimony sulfoiodide, vanadium oxide, lead titanate, lead lanthanum zirconium titanate, polysilicon, and amorphous silicon.

28. The system of claim 18 wherein the temperature sensitive material further comprises a bolometric resistive material.

29. The system of claim 18 wherein the temperature sensitive material further comprises ferroelectric material.

30. The system of claim 18 further comprising an infrared absorber assembly extending outwardly from the thermal detector for interacting with infrared energy incident thereto and for producing a temperature change in the thermal detector.