Imaging system including an array of dual-band microbridge detectors

• US 6,157,404 A
• Filed: 07/20/1998
• Issued: 12/05/2000
• Est. Priority Date: 11/15/1995
• Status: Expired due to Term

• Current Assignee: Lockheed Martin IR Imaging Systems, Inc. (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin IR Imaging Systems, Inc. (Martin Marietta Corporation)
• Inventors: Marshall, Charles M., Blackwell, Richard
• Primary Examiner(s): Garber, Wendy
• Assistant Examiner(s): MOE, AUNG SOE
• Application Number:
  US09/119,158
• Time in Patent Office: 869 Days
• Field of Search: 348/207, 348/216, 348/332, 348/345, 250/214 R, 250/208.1, 250/332, 250/338.4
• US Class Current: 348/216.1
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H01L 25/042 the devices being arranged next to each other solar cells H01L31/042
• CPC Class Codes: H01L 27/1465 of the hybrid type
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 31/09 Devices sensitive to infrared, visible or ultraviolet radiation H01L31/101 takes precedence
• CPC Class Codes: H10N 19/00 Integrated devices, or assemblies of multiple devices, comprising at least one thermoelectric or thermomagnetic element covered by groups H10N10/00 - H10N15/00

Abstract

A dual-band detector that absorbs incident radiation in a first range of wavelengths and that absorbs incident radiation in a second range of wavelengths. The dual-band detector includes a semiconductor substrate and a first microbridge detector level disposed above the semiconductor substrate. The first microbridge detector level includes an active area that absorbs incident radiation in one of the first range of wavelengths and the second range of wavelengths. In one embodiment, the semiconductor substrate includes a detector that detects incident radiation in the other of the first and second range of wavelengths. In another embodiment, the dual-band microbridge detector also includes a second microbridge detector level. The second microbridge detector level also includes an active area that absorbs incident radiation in an alternative one of the first range of wavelengths and the second range or wavelengths. With this apparatus, the dual-band detector can operate in a first range of wavelengths and also in a second range of wavelengths. In addition, this apparatus can be fabricated using existing processing techniques.

Claims

1. An imaging system, comprising:

a lens that receives an electromagnetic signal, focuses the electromagnetic signal and outputs a focussed electromagnetic signal;

a focal plane array including a plurality of dual-band detector devices disposed in the focal plane array, wherein each dual-band detector device detects the focussed signal, converts the focussed signal into a sensed signal and outputs the sensed signal to provide a plurality of sensed signals at an output of the focal plane array, and wherein each dual-band detector device includes;

a semiconductor substrate including a detector device that is responsive to the focussed signal in a first band of wavelengths; and

a microbridge detector disposed above the semiconductor substrate, including a sensing element that is responsive to the focussed signal in a second band of wavelengths, and support legs that support the microbridge detector above the semiconductor substrate and that couple a detected signal provided by the sensing element to the semiconductor substrate;

a focal plane array processor that receives the plurality of sensed signals, processes the plurality of sensed signals to correct any gain and any offset errors between each of the plurality of sensed signals, and that outputs a plurality of processed signals;

a display processor that receives the plurality of processed signals, converts the plurality of processed signals into a display signal suitable for output to a display, and that outputs the display signal; and

the display that receives the display signal and displays the display signal so as to display an image of a scene or object that emitted the electromagnetic signal.

2. The imaging system of claim 1, wherein the imaging system is a helmet-mounted imaging device.

3. The imaging system of claim 1, wherein the imaging system is a goggle-mounted imaging system.

4. The imaging system of claim 1, wherein the imaging system is a monocular system.

5. The imagining system of claim 1, wherein the imaging system is a binocular system.

6. The imaging system of claim 1, wherein the imaging system is a weapon sight.

7. The imaging system of claim 1, wherein the imaging system is a camcorder apparatus.

8. The imaging system of claim 1, wherein the imaging system is a microscope.

9. The imaging system of claim 1, wherein the imaging system is a radiometer.

10. The imaging system of claim 1, wherein the imaging system is a spectrometer.

11. The imaging system of claim 1, wherein the microbridge detector is disposed above the detector device and is substantially transmissive to electromagnetic radiation in the first band of wavelengths.

12. The imaging system of claim 1, wherein the microbridge detector is disposed adjacent the detector device.

13. The imaging system of claim 12, further comprising a reflective layer disposed on the semiconductor substrate below the microbridge detector, wherein a distance between the microbridge detector and the reflective layer is selected so as to enhance absorption of the incident radiation in the second band of wavelengths.

14. The imaging system of claim 1, wherein the support legs include downwardly extending leg portions which are a continuation of the microbridge detector support the microbridge detector above the semiconductor substrate so that a thermal isolation gap exists between the microbridge detector and the semiconductor substrate;

and

electrically conductive paths included within said downwardly extending leg portions connecting the sensing element to the semiconductor substrate.

15. The imaging system of claim 1, wherein the support legs include etched contacts which vertically extend from the microbridge detector to the semiconductor substrate and which support the microbridge detector above the semiconductor substrate so that a thermal isolation gap exists between the microbridge detector and the semiconductor substrate.

16. The imaging system of claim 1, wherein the sensing element includes a thin film layer of temperature responsive resistive material.

17. The imaging system of claim 1, wherein the sensing element includes a layer of absorptive material which has peak absorption characteristics in the second band of wavelengths.

18. The imaging system of claim 1, wherein the detector device is a charge coupled device sensor disposed in the semiconductor substrate.

19. The imaging system of claim 1, wherein the semiconductor substrate further comprises:

means for pulsing the sensing element; and

means for sampling a signal provided by each of the detector device and the sensing element, in response to the incident energy in the corresponding first band of wavelengths and the second band of wavelengths.

20. The imaging system of claim 1, wherein the semiconductor substrate further comprises an integrated circuit disposed within the semiconductor substrate, that pulses the sensing element and that samples a signal provided by each of the detector device and the sensing element, in response to the incident radiation in each of the respective first band of wavelengths and the second band of wavelengths.

21. The imaging system of claim 1, wherein the first band of wavelengths is in a range between 0.4 and 0.8 microns.

22. The imaging system of claim 1, wherein the second band of wavelengths is in a range between 8 and 14 microns.

23. An imaging system, comprising:

a lens that receives an electromagnetic signal, focuses the electromagnetic signal and outputs a focussed electromagnetic signal;

a focal plane array including a plurality of dual-band detector devices disposed in the focal plane array, wherein each dual-band detector device detects the focussed signal, converts the focussed signal into a sensed signal and outputs the sensed signal to provide a plurality of sensed signals at an output of the focal plane array, and wherein each dual-band detector device includes;

a first microbridge detector disposed above a semiconductor substrate, including a first sensing element that is responsive to the focussed signal in a first band of wavelengths, and first support legs that support the microbridge detector above the semiconductor substrate and couple a first detected signal provided by the first sensing element to the semiconductor substrate; and

a second microbridge detector disposed above the semiconductor substrate, including a second sensing element that is responsive to the focussed signal in a second band of wavelengths, and second support legs that support the microbridge detector above the semiconductor substrate and couple a second detected signal provided by the second sensing element to the semiconductor substrate;

a focal plane array processor that receives the plurality of sensed signals, processes the plurality of sensed signals to correct any gain and any offset errors between each of the plurality of sensed signals, and that outputs a plurality of processed signals;

a display processor that receives the plurality of processed signals, converts the plurality of processed signals into a display signal suitable for output to a display, and that outputs the display signal; and

the display that receives the display signal and displays the display signal so as to display an image of a scene or object that emitted the electromagnetic signal.

24. The imaging system of claim 23, wherein the imaging system is a helmet-mounted imaging device.

25. The imaging system of claim 23, wherein the imaging system is a goggle-mounted imaging device.

26. The imaging system of claim 23, wherein the imaging system is a monocular device.

27. The imaging system of claim 23, wherein the imaging system is a binocular device.

28. The imaging system of claim 23, wherein the imaging system is a weapon sight.

29. The imaging system of claim 23, wherein the imaging system is a camcorder device.

30. The imaging system of claim 23, wherein the imaging system is a microscope.

31. The imaging system of claim 23, wherein the imaging system is a radiometer.

32. The imaging system of claim 23, wherein the imaging system is a spectrometer.

33. The imaging system of claim 23, wherein the second microbridge detector including the second sensing element is substantially transmissive to the focussed signal outside the second range of wavelengths, wherein the first microbridge detector including the first sensing element is substantially transmissive to the focussed signal outside the first range of wavelengths, and wherein the second microbridge detector including the second sensing element is disposed above the first microbridge detector including the first sensing element.

34. The imaging system as claimed in claim 33, further comprising a reflective layer disposed on the first microbridge detector below the second microbridge detector, so that a distance between the second microbridge detector and the reflective layer enhances absorption of the incident radiation in the second range of wavelengths by the second sensing element.

35. The imaging system as claimed in claim 23, wherein the first microbridge detector including the first sensing element is disposed adjacent the second microbridge detector including the second sensing element.

36. The imaging system of claim 23, wherein the first sensing element includes a thin film layer of temperature responsive resistive material.

37. The imaging system of claim 36, wherein the second sensing element includes a thin film layer of temperature responsive resistive material.

38. The imaging system of claim 37, wherein the second sensing element includes a layer of absorptive material which has peak absorption characteristics in the second range of wavelengths.

39. The imaging system of claim 23, wherein the first sensing element includes a layer of absorptive material which has peak absorption characteristics in the first range of wavelengths.

40. The imaging system of claim 23, further comprising a reflective layer disposed on the semiconductor substrate below the first microbridge detector and the second microbridge detector, wherein a first distance between the first microbridge detector and the reflective layer enhances absorption of the incident radiation in the first range of wavelengths and wherein a second distance between the second microbridge detector and the reflective layer enhances absorption of the incident radiation in the second range of wavelengths.

41. The imaging system of claim 23, wherein the first range of wavelengths is in a range of 3-5 microns.

42. The imaging system of claim 23, wherein the second range of wavelengths is in a range of 8-14 microns.

43. The imaging system of claim 23, wherein the semiconductor substrate includes means for pulsing each of the first sensing element and the second sensing element.

44. The imaging system of claim 43, wherein the semiconductor substrate further includes a means for sampling the first detected signal from the first sensing element and a means for sampling the second detected signal from the second sensing element, in response to the focussed signal in the first range of wavelengths and the second range of wavelengths.

45. The imaging system of claim 23, wherein the semiconductor substrate includes an integrated circuit disposed within the semiconductor substrate that pulses each of the first sensing element and the second sensing element and that samples the first detected signal and the second detected signal provided by each of the first sensing element and the second sensing element, in response to the focussed signal in the corresponding first range of wavelengths and the second range of wavelengths.

46. The imaging system of claim 23, wherein the first support legs include first downwardly extending leg portions which are a continuation of the first microbridge detector and which support the first microbridge detector above the semiconductor substrate so that a thermal isolation gap exists between the first microbridge detector and the semiconductor substrate, and first electrically conductive paths included within the first downwardly extending leg portions connecting the first sensing element to the semiconductor substrate.

47. The imaging system of claim 46, wherein the second support legs include second downwardly extending leg portions which are a continuation of the second microbridge detector and which support the second microbridge detector above the semiconductor substrate so that a thermal isolation gap exists between the second microbridge detector and the semiconductor substrate, and second electrically conductive paths included within said second downwardly extending leg portions connecting the second sensing element to the semiconductor substrate.

48. The imaging system of claim 23, wherein the first support legs include etched contacts which vertically extend from the first microbridge detector down to the semiconductor substrate.

49. The imaging system of claim 48, wherein the second support legs include etched contacts which vertically extend from the second microbridge detector down to the semiconductor substrate.