Systems And Methods That Detect Changes In Incident Optical Radiation

• US 20110139964A1
• Filed: 02/22/2011
• Published: 06/16/2011
• Est. Priority Date: 10/23/2002
• Status: Active Grant

• Current Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Original Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Inventors: Gogo, Ashifi, Garmire, Elsa, Bessette, Jonathan T.
• Granted Patent: US 8,174,253 B2
• Time in Patent Office: Days
• US Class Current: 250/208.2
• CPC Class Codes: G01B 11/162 by speckle- or shearing interferometry
• CPC Class Codes: G01B 9/02 Interferometers
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01J 1/42 using electric radiation detectors optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices

Abstract

Systems, methods and sensors detect changes in incident optical radiation. Voltage is applied across one or more active areas of a detector while the incident optical radiation illuminates the active areas. Current is sensed across one or more of the active areas, a change in the current being indicative of the changes in incident optical radiation.

Claims

1. A detector for detecting changes in incident optical radiation, comprising:

an insulating substrate having a first surface;

an array of photoconductive active areas formed on the first surface of the insulating substrate, for detecting the incident optical radiation, the active areas formed of a group IV semiconductor; and

for each active area, a pair of electrical contacts mounted with and electrically coupled to opposing ends of said each active area, for providing electrical interface to the active area;

wherein electrical contacts on first ends of the active areas are independent of electrical contacts on second ends of the active areas.

2. The detector of claim 1, the active areas being formed of silicon.

3. The detector of claim 2, the insulating substrate comprising:

a layer of silicon, and

a layer of silicon dioxide formed on the silicon layer, an upper surface of the silicon dioxide layer opposite to the silicon layer forming the first surface.

4. The detector of claim 3, each active area of the array having a first end opposite a second end, a first electrical contact of the associated pair of electrical contacts being electrically coupled to the first end, and a second electrical contact of the associated pair of electrical contacts being electrically coupled to the second end;

wherein the first electrical contacts are independent of the second electrical contacts, and wherein each pair of electrical contacts provides a voltage across its associated active area.

5. The detector of claim 1, the active areas of the array being physically separated from one another.

6. The detector of claim 3, the first surface of the insulating substrate being planar.

7. A sensor for detecting a change in incident optical radiation, comprising:

a detector, including;

an insulating substrate including;

a layer of silicon, and

a layer of silicon dioxide formed on the silicon layer, an upper surface of the silicon dioxide layer opposite to the silicon layer forming a first surface;

a first photoconductive active area formed on the first surface, for detecting the incident optical radiation, the first active area formed of silicon; and

a first electrical contact electrically coupled to a first end of the first active area and a second electrical contact electrically coupled to an opposing, second end of the first active area for providing electrical interface with the first active area;

a second photoconductive active area formed of silicon on the first surface, having opposing first and second ends and being physically separated from the first active area, for detecting the incident optical radiation; and

a third electrical contact electrically coupled to the first end of the second active area and a fourth electrical contact electrically coupled to the second end of the second active area, for providing electrical interface with the second active area; and

electronics for measuring a change in current through the active areas to determine the change in the incident optical radiation;

wherein the first and third electrical contacts are independent of the second and fourth electrical contacts.

8. The sensor of claim 7, wherein output of each active area connects to individually addressable current sensing and processing electronics.

9. The sensor of claim 7, further comprising:

a laser;

a power splitter including an arm; and

an optical fiber coupled to the power splitter,

the laser generating a laser beam into the arm of the power splitter, the laser beam exiting the optical fiber, reflecting off a surface of an object and reentering the optical fiber to interfere with the laser beam within the optical fiber, and

the first and second active areas arranged to detect the interfered laser beam within the optical fiber, a change in current through the first and second active areas indicating motion of the object'"'"'s surface.

10. The sensor of claim 7, further comprising an optical fiber optically coupled to the first or the second active area.

11. A sensor for detecting a change in incident optical radiation, comprising:

a detector, including;

an insulating substrate including;

a layer of silicon, and

a layer of silicon dioxide formed on the layer of silicon, an upper surface of the silicon dioxide layer opposite to the silicon layer forming a first surface;

an array of photoconductive active areas for detecting the incident optical radiation, the active areas formed of silicon on the first surface of the insulating substrate; and

for each active area, a first and a second electrical contact electrically coupled to opposing first and second ends of the active area, for applying a voltage from a voltage source across the active area;

wherein electrical contacts coupled to first ends of the active areas are independent of electrical contacts coupled to second ends of the active areas;

for at least one active area of the array, a load resistor electrically connected in series with the at least one active area, and

electronics for measuring a change in voltage across the load resistor, the change in voltage being indicative of the change in the incident optical radiation.

12. The sensor of claim 11, the voltage source being common to each active area of the array and being selected from the group consisting of a constant voltage source and a time varying voltage source.

13. The sensor of claim 11, the electronics being coupled to the voltage source, and being configured to modulate the voltage source so that the voltage applied across each active area is modulated at a desired frequency.

14. The sensor of claim 11, further comprising:

a laser;

a power splitter including an arm; and

an optical fiber coupled to the power splitter,

the laser generating a laser beam into the arm of the power splitter, the laser beam exiting the optical fiber, reflecting off an object'"'"'s surface, and reentering the optical fiber to interfere with the laser beam within the optical fiber, and wherein

the active areas are arranged to detect the interfered laser beam within the optical fiber, the change in voltage across the load resistor indicating motion of the object'"'"'s surface.

15. The sensor of claim 11, further comprising an optical fiber optically coupled to the array.

16. A method for detecting a change in optical radiation, comprising the steps of:

applying an electric voltage to at least one of an array of photoconductive active areas via first and second individually-addressable electrical contacts coupled with opposing first and second ends of the at least one active area while the optical radiation illuminates the at least one active area, the active areas formed of silicon on a first surface of an insulating substrate, the insulating substrate including a layer of silicon and a layer of silicon dioxide formed on the silicon layer, an upper surface of the silicon dioxide layer opposite to the silicon layer forming the first surface; and

measuring a current change through the at least one active area, the current change being indicative of the change in the optical radiation.

17. The method of claim 16, the optical radiation reflecting off an object'"'"'s surface, the change in the optical radiation resulting from a movement of the object'"'"'s surface, the method further comprising determining motion of the object'"'"'s surface from the current change across the first active area.

18. The method of claim 16, further comprising:

illuminating an object'"'"'s surface with a laser having a wavelength that is smaller than defined geometric features of the surface such that moving speckle, indicative of surface motion, illuminates the at least one active area while voltage is applied to the at least one active area; and

determining surface motion from the current change through the at least one active area.

19. The method of claim 18, the step of illuminating the object'"'"'s surface comprising generating an interference pattern that varies with surface motion.

20. The method of claim 18, the surface motion comprising surface displacement.

21. The method of claim 16, the optical radiation comprising an interference or diffraction pattern dependent upon a distance between two objects, the method further comprising:

detecting changes in the interference or diffraction pattern to align the objects by measuring the current change through the at least one active area, the current change indicating a change in the distance between the objects;

assessing a relative position between the objects; and

aligning the objects according to changes in the interference or diffraction pattern.

22. The method of claim 21, the optical radiation being generated by illuminating a gap between the objects with a laser.

23. The method of claim 21, wherein the step of assessing the relative position comprises assessing relative angles between the two objects, and wherein the current change through the at least one active area indicates a change in an angular relationship between the objects.

24. A method for detecting a change in optical radiation, comprising the steps of:

applying a voltage across an array of photoconductive active areas while the optical radiation illuminates the array, the active areas formed of silicon on a first surface of an insulating substrate, the insulating substrate including a layer of silicon and a layer of silicon dioxide formed on the silicon layer, an upper surface of the silicon dioxide layer opposite to the silicon layer forming the first surface; and

measuring a current change through at least a first active area of the array of photoconductive active areas, the change being indicative of the change in the optical radiation;

wherein applying a voltage across the array comprises utilizing a plurality of first electrodes and second electrodes to apply the voltage across the active areas, each of the first electrodes electrically coupled with a first end of an active area, and each of the second electrodes electrically coupled with an opposing second end of an active area, and wherein the first electrodes are independent of the second electrodes.

25. The method of claim 24, the optical radiation reflecting off an object'"'"'s surface, the change in the optical radiation resulting from a movement of the object'"'"'s surface, the method further comprising determining motion of the object'"'"'s surface from the current change through at least the first active area of the array.

26. The method of claim 24, further comprising:

illuminating an object'"'"'s surface with a laser having a wavelength that is smaller than defined geometric features of the surface such that moving speckle, indicative of surface motion, illuminates the array while voltage is applied across the active areas; and

determining the surface motion from current change through the first active area.

27. The method of claim 26, the step of illuminating the surface comprising generating an interference pattern that varies with the surface motion.

28. The method of claim 26, the surface motion comprising surface displacement.

29. The method of claim 24, the optical radiation comprising an interference or diffraction pattern dependent upon a distance between two objects, the method further comprising:

detecting changes in the interference or diffraction pattern to align the objects by measuring the current change through at least the first active area, the current change indicating a change in the distance between the objects;

assessing a relative position between the objects; and

aligning the objects according to changes in the interference or diffraction pattern.

30. The method of claim 29, the optical radiation being generated by illuminating a gap between the objects with a laser.

31. The method of claim 29, wherein assessing a relative position comprises assessing relative angles between the two objects, and wherein the current change through at least the first active area indicates a change in an angular relationship between the objects.

32. The method of claim 24, further comprising:

measuring a current change through a separate second active area of the array of photoconductive active areas, and

comparing a time rate of change of the current through the first and second active areas of the array, a difference between the separate time rates being indicative of spatial characteristics of the optical radiation.