OPTICAL COUPLED SENSORS FOR HARSH ENVIRONMENTS

• US 20090302242A1
• Filed: 06/05/2009
• Published: 12/10/2009
• Est. Priority Date: 06/06/2008
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Alliant Techsystems Incorporated (Northrop Grumman Corporation)
• Inventors: Papadopoulos, George
• Granted Patent: US 9,391,216 B2
• Time in Patent Office: Days
• US Class Current: 250/550
• CPC Class Codes: G01F 1/661 using light
• CPC Class Codes: G01N 2011/008 optical properties
• CPC Class Codes: H01L 31/0203 Containers; Encapsulations , e.g. encapsulation of photodiodesfor photovoltaic devices H01L31/048; for organic photosensitive devices H10K30/80
• CPC Class Codes: H01L 31/02325 the optical elements not being integrated nor being directly associated with the device

Abstract

An optical sensor comprising a light source; a sensor substrate, arranged to receive a force to be detected, the sensor substrate including an interference pattern generator, optically coupled to the light source for receiving light from the light source, and generating an interference pattern, and a detector, optically coupled to the sensor substrate for receiving the interference pattern and providing a signal which can be used to determine the force applied to the sensor substrate.

Claims

1. An optical sensor comprising:

a light source;

a sensor substrate, arranged to receive a force to be detected, the sensor substrate including an interference pattern generator, optically coupled to the light source for receiving light from the light source, and generating an interference pattern, and

a detector, optically coupled to the sensor substrate for receiving the interference pattern and providing a signal which can be used to determine the force applied to the sensor substrate.

2. The optical sensor of claim 1 wherein the light source produces coherent light.

3. The optical sensor of claim 2 wherein the light source is a laser diode optically connected to a collimating lens.

4. The optical sensor of claim 2 wherein the light source is a fiber optic having proximal and distal ends, the proximal end of the fiber optic optically connected to the light source, the distal end of the fiber optic optically connected to a collimating lens.

5. The optical sensor of claim 2 wherein the light source is a laser emitting diode (LED) optically connected to a collimating lens.

6. The optical sensor of claim 1 wherein the force to be detected is a pressure force, which is normal to the sensor substrate.

7. The optical sensor of claim 6 wherein the sensor substrate comprises a diaphragm and wherein the interference pattern generator is a reflection grating attached to the diaphragm, which flexes under the normal force applied to the diaphragm, which results in a change to the fringe frequency produced by the reflective grating, the change in fringe frequency allowing the determination of the pressure force applied to the diaphragm.

8. The optical sensor of claim 7 wherein the sensor substrate is arranged in a sensor cavity, the cavity being hermetically sealed.

9. The optical sensor of claim 8 further including a temperature sensor for monitoring the temperature of the sensor cavity, the temperature of the sensor cavity being used to calibrate the measured pressure force.

10. The optical sensor of claim 6 wherein the detector is a photodetector.

11. The optical sensor of claim 6 wherein the detector is a linear detector array.

12. The optical sensor of claim 6 wherein the detector is a CCD or CMOS imager device.

13. The optical sensor of claim 1 wherein the sensor substrate is comprised of silicon carbide.

14. The optical sensor of claim 1 wherein the force to be detected is a shear force, which is parallel to the sensor substrate.

15. The optical sensor of claim 14 wherein the sensor substrate comprises a sensor pad connected between two springs to the sensor substrate, arranged to move laterally by the shear force, and wherein the interference pattern generator is a reflection grating attached to the sensor pad, which moves laterally with the sensor pad under the shear force applied to the sensor pad, which results in a phase change as the fringe pattern moves laterally across the detector, the lateral movement of the fringe pattern allowing the determination of the shear force applied to the sensor pad.

16. The optical sensor of claim 15 wherein the sensor substrate is arranged in a sensor cavity.

17. The optical sensor of claim 14 wherein the detector is a photodetector.

18. The optical sensor of claim 14 wherein the detector is a linear detector array.

19. The optical sensor of claim 14 wherein the detector is a CCD or CMOS imager device.

20. The optical sensor of claim 15 wherein the sensor is configured and arranged to operate in a hypersonic high temperature environment.

21. The optical sensor of claim 20 wherein sensor substrate is made from silicon carbide, and the detector is optically connected to the reflection grating with a sapphire based fiber optic, the optical sensor capable of operating in temperatures of greater than 1000°

C.

22. The optical sensor of claim 14 wherein the sensor substrate comprises a sensor pad connected between two springs to the sensor substrate, arranged to move laterally by the shear force, and wherein the interference pattern generator is comprised of a first through-hole arranged in the stationary portion of the sensor substrate and a second through-hole arranged in the moveable sensor pad portion of the sensor substrate, wherein the change in separation distance between the moveable through-hole and the stationary through-hole creates a change in the fringe frequency of the interference pattern at the detector, which is used to determine the shear force.

24. The optical sensor of claim 1 can be configured so that the light source and detector are on the same side of the sensor substrate, using a reflection grating, or the light source and detector can be on opposite sides of the sensor substrate, using slits or pinholes.

25. The optical sensor of claim 1 wherein the sensor substrate is comprised of silicon.

23. An optical sensor comprising:

a light source;

a fixed sensor substrate, the sensor substrate including a pair of slits separated a predetermined distance apart, each slit illuminated by the light source after traveling through compressible or thermal turbulence so as to generate an interference pattern that varies with time, the light intensity of which is converted to a voltage signal by a pair of photodetectors optically aligned with the slits. and

a signal processor for performing cross-correlation of the two voltage signals output from the photodetectors, to determine the time separation between the two signals, which can be used to determine the flow velocity of the fluid.