Detection beyond the standard radiation noise limit using reduced emissivity and optical cavity coupling

• US 20080217539A1
• Filed: 12/06/2007
• Published: 09/11/2008
• Est. Priority Date: 12/08/2006
• Status: Active Grant

• Current Assignee: Regents of the University Minnesota
• Original Assignee: Regents of the University Minnesota
• Inventors: Talghader, Joseph J.
• Granted Patent: US 7,800,066 B2
• Time in Patent Office: Days
• US Class Current: 250/340
• CPC Class Codes: A61B 17/00234 for minimally invasive surgery A61B17/0218, A61B17/0469, A61B17/12013, A61B17/1285, A61B17/29, A61B17/320016 take precedence
• CPC Class Codes: A61B 17/205 Vaccinating by means of needles or other puncturing devices
• CPC Class Codes: A61B 17/3478 Endoscopic needles, e.g. for infusion biopsy needles A61B10/0233; catheters with injection needles A61M25/0067
• CPC Class Codes: A61B 2017/00247 Making holes in the wall of the heart, e.g. laser Myocardial revascularization
• CPC Class Codes: A61B 2017/00876 magnetic
• CPC Class Codes: A61B 2017/2936 Pins in guiding slots
• CPC Class Codes: A61B 2017/2943 Toothed members, e.g. rack and pinion
• CPC Class Codes: A61B 2017/306 holding by means of suction
• CPC Class Codes: A61B 2018/00392 Transmyocardial revascularisation
• CPC Class Codes: A61B 2090/034 abutting on parts of the device itself
• CPC Class Codes: A61M 2025/0086 the needles having bent tips, i.e. the needle distal tips are angled in relation to the longitudinal axis of the catheter
• CPC Class Codes: A61M 2025/0087 Multiple injection needles protruding laterally from the distal tip
• CPC Class Codes: A61M 5/32 Needles; Details of needles pertaining to their connection with syringe or hub infusion needles A61M5/158; Accessories for bringing the needle into, or holding the needle on, the body A61M5/42, A61M5/46 take precedence; guide needles for catheters A61M25/065; Devices for protection of needles apparatus specially adapted for cleaning or sterilising needles A61M5/001
• CPC Class Codes: G01J 5/061 by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices

Abstract

The present invention provides thermal detectors having an optical cavity that is optimized to couple light into a sensor. Light that is on resonance is coupled with the sensor with as high as 100% efficiency, while light off resonance is substantially reflected away. Light that strikes the sensor from the sides (i.e. not on the optical cavity axis) only interacts minimally with sensor because of the reduced absorption characteristics of the sensor. Narrowband sensors in accordance with the present invention can gain as much as 100% of the signal from one direction and spectral band, while receiving only a fraction of the normal radiation noise, which originates from all spectral bands and directions.

Claims

1. A thermal detector for sensing infrared radiation, the thermal detector comprising:

a resonant optical cavity at least partially defined by first and second spaced apart layered thin-film mirror structures; and

an infrared sensor operatively positioned between the first and second thin-film mirror structures and suspended within the resonant optical cavity by one or more electrically conductive support structures so radiation received by the resonant optical cavity impinges on at least a surface portion of the infrared sensor.

2. The thermal detector of claim 1, wherein at least one of the first and second thin-film mirror structures comprises a Distributed Bragg Reflector.

3. The thermal detector of claim 1, wherein the first and second thin-film mirror structures provide a standing maximum centered in the resonant optical cavity.

4. The thermal detector of claim 1, wherein at least one of the first and second thin-film mirror structures comprises a reflectivity centered between about 3 microns and about 14 microns.

5. The thermal detector of claim 1, wherein the resonant optical cavity provides a vacuum to thermally isolate the infrared sensor from the first and second thin-film mirror structures.

6. The thermal detector of claim 1, wherein the infrared sensor comprises a bolometer.

7. The thermal detector of claim 6, wherein the bolometer comprises a thin-film temperature sensitive resistor electrically connected to the one or more electrically conductive support structures.

8. The thermal detector of claim 7, wherein the thin-film temperature sensitive resistor comprises one or more of vanadium oxide, YBaCuO, polysilicon, and titanium.

9. The thermal detector of claim 6, wherein the bolometer comprises an absorbing layer.

10. The thermal detector of claim 9, wherein the absorbing layer comprises one or more of a metal, alloy, dielectric, and semiconductor.

11. The thermal detector of claim 1, wherein the one or more electrically conducting support structures thermally isolate the infrared sensor and comprises a thermal conductance per unit surface area below about 1 W/(Km²).

12. The thermal detector of claim 1 in combination with one or more of a chemical sensing device, an industrial process control device, an engine monitoring device, an effluent monitoring device, an environmental monitoring device, a temperature measurement device, a pressure measurement device, an explosives detection device, an imaging device, and a medical monitoring device.

13. A thermal detector for sensing infrared radiation, the thermal detector comprising:

a resonant optical cavity at least partially defined by first and second spaced apart layered thin-film mirror structures; and

an infrared sensor operatively positioned between the first and second thin-film mirror structures and suspended within the resonant optical cavity by one or more electrically conductive support structures so radiation received by the resonant optical cavity impinges on at least a portion of the infrared sensor and wherein said portion of the infrared sensor has an absorption less than or equal to twenty-five percent.

14. The thermal detector of claim 13, wherein the infrared sensor has an absorption less than about ten percent.

15. The thermal detector of claim 13, wherein the infrared sensor comprises a bolometer.

16. The thermal detector of claim 13, wherein the one or more electrically conducting support structures thermally isolate the infrared sensor and comprises a thermal conductance below about 1 W/K/m².

17. The thermal detector of claim 13, wherein the infrared sensor comprises a membrane having a thickness less than about one hundred nanometers.

18. The thermal detector of claim 13, wherein the one or more electrically conducting support structures comprises a thin-film structure comprising an insulating layer and an electrically conductive layer.

19. A method of sensing infrared radiation, the method comprising the steps of:

providing a resonant optical cavity at least partially defined by first and second spaced apart mirror thin-film structures and an infrared sensor suspended within the resonant optical cavity;

causing radiation to enter the resonant optical cavity and couple with the infrared sensor; and

measuring a change in the infrared sensor caused by the radiation coupled with the infrared sensor.

20. The method of claim 19, therein the infrared sensor comprises a bolometer.

21. The method of claim 19, wherein the step of measuring a change in the infrared sensor includes measuring a change in the resistance of at least a portion of the infrared sensor.

22. A method of making a thermal detector for sensing infrared radiation, the method comprising the steps of:

forming a resonant optical cavity at least partially defined by first and second spaced apart thin-film mirror structures;

suspending an infrared sensor within the resonant optical cavity; and

positioning the infrared sensor within the optical cavity so the absorption of the resonant wavelength of the optical cavity by the sensor is greater than twenty-five percent.

23. The method of claim 22, comprising providing a vacuum in the resonant optical cavity.

24. The method of claim 22, wherein the step of suspending an infrared sensor within the resonant optical cavity comprises forming a bolometer structure.

25. The method of claim 22, wherein the absorption of the resonant wavelength of the optical cavity by the sensor is greater than seventy-five percent.