Systems And Methods That Detect Changes In Incident Optical Radiation

• US 20090027038A1
• Filed: 06/30/2008
• Published: 01/29/2009
• Est. Priority Date: 10/23/2002
• Status: Abandoned Application

• 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.
• Application Number:
  US12/165,338
• Publication Number:
  US 20090027038A1
• Time in Patent Office: Days
• US Class Current: 324/95
• 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. Current is driven through one or more active areas of a detector while the incident optical radiation illuminates the active areas. Voltage is sensed across one or more of the active areas, a change in the voltage 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;

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

a first and a second electrical contact both electrically coupled to the first active area.

2. The detector of claim 1, the first active area 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, the first active area having a first end opposite a second end, the first electrical contact being electrically coupled to the first end, and the second electrical contact being electrically coupled to the second end.

5. The detector of claim 3, further comprising a third and fourth electrical contact both electrically coupled to the first active area between the first and second electrical contacts.

6. The detector of claim 3, further comprising a second photoconductive active area disposed on the first surface of the insulating substrate, for detecting the incident optical radiation, the second active area formed of silicon, the second active area being physically separated from the first active area.

7. The detector of claim 6, further comprising a third and a fourth electrical contact both electrically coupled to the second active area.

8. The detector of claim 6, the first electrical contact being electrically coupled to both the first and second active areas between the first and second active areas.

9. The detector of claim 8, further comprising a third active area formed on the first surface of the insulating substrate, for detecting the incident optical radiation, the third active area formed of silicon, the third active area being physically separated from the first and second active areas, the second electrical contact being electrically coupled to both the second and third active areas between the second and third active areas.

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

11. The detector of claim 3, the first surface of the insulating substrate being cylindrical.

12. 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 and a second electrical contact both electrically coupled to the first active area for driving an electrical current from a current source through the first active area; and

electronics for measuring a change in voltage across the first active area to determine the change in the incident optical radiation.

13. The sensor of claim 12, the current source being selected from the group consisting of a constant current source and a time varying current source.

14. The sensor of claim 12, further comprising a third and fourth electrical contact both coupled to the first active area, the electronics being connected to the third and fourth electrical contacts to measure the change in voltage across the first active area.

15. The sensor of claim 12, the electronics being coupled to the current source, the electronics being configured to modulate the current source so that current is modulated through the first active area at a desired frequency.

16. The sensor of claim 12, 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 active area arranged to detect the interfered laser beam within the optical fiber, the change in voltage across the first active area indicating motion of the object'"'"'s surface.

17. The sensor of claim 12, further comprising an optical fiber optically coupled to the first active area.

18. The sensor of claim 12,

further comprising a second photoconductive active area, formed on the first surface, for detecting the incident optical radiation, the second active area formed of silicon,

the second active area being physically separated from the first active area, and

the second active area being electrically connected in series with the first active area.

19. The sensor of claim 18, further comprising a third electrical contact, the third electrical contact being electrically coupled to the second active area, the second electrical contact being electrically coupled to both the first and second active areas between the first and second active areas.

20. 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;

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

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

a load resistor electrically connected in series with the 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.

21. The sensor of claim 20, the voltage source being selected from the group consisting of a constant voltage source and a time varying voltage source.

22. The sensor of claim 20, the electronics being coupled to the voltage source, and being configured to modulate the voltage source so that the voltage applied across the active area is modulated at a desired frequency.

23. The sensor of claim 20, 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

the active area 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.

24. The sensor of claim 20, further comprising an optical fiber optically coupled to the active area.

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

driving an electric current through a first photoconductive active area while the optical radiation illuminates the first active area, the first active area 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 voltage change across the first active area, the voltage change being indicative of the change in the optical radiation.

26. The method of claim 25, the first active area having a first, second, third, and fourth electrical contact electrically coupled thereto, the third and fourth electrical contacts being disposed between the first and second electrical contacts,

the step of driving comprising driving the current through the first and second electrical contacts and through the active area,

the step of measuring comprising measuring the voltage change across the first active area via the third and fourth electrical contacts.

27. The method of claim 25, further comprising driving the current through a second photoconductive active area formed of silicon on the first surface of the insulating substrate, while the optical radiation illuminates the second active area, the second active area being electrically connected in series with the first active area.

28. The method of claim 27, further comprising:

measuring a voltage change across the second active area,

comparing a time rate of change of the voltage across both of the first and second active areas, a difference between the two measured time rates being indicative of spatial characteristics of the optical radiation.

29. The method of claim 25, 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 voltage change across the first active area.

30. The method of claim 25, 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 first active area while current is driven through the first active area; and

determining surface motion from the voltage change across the first active area.

31. The method of claim 30, the step of illuminating the object'"'"'s surface comprising generating an interference pattern that varies with surface motion.

32. The method of claim 30, the surface motion comprising surface displacement.

33. The method of claim 25, 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 voltage change across the first active area, the voltage 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.

34. The method of claim 33, the optical radiation being generated by illuminating a gap between the objects with a laser.

35. The method of claim 33,

wherein the step of assessing the relative position comprises assessing relative angles between the two objects, and

wherein the voltage change across the first active area indicates a change in an angular relationship between the objects.

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

applying a voltage across a first photoconductive active area while the optical radiation illuminates the first active area, the first active area 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 voltage change across a first load resistor electrically connected in series with the first active area, the voltage change across the first load resistor being indicative of the change in the optical radiation.

37. The method of claim 36, 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 voltage change across the first load resistor.

38. The method of claim 36, 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 first active area while voltage is applied across the first active area; and

determining the surface motion from the voltage change across the first load resistor.

39. The method of claim 38, the step of illuminating the surface comprising generating an interference pattern that varies with the surface motion.

40. The method of claim 38, the surface motion comprising surface displacement.

41. The method of claim 36, 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 voltage change across the first load resistor, the voltage 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.

42. The method of claim 41, the optical radiation being generated by illuminating a gap between the objects with a laser.

43. The method of claim 41, wherein assessing a relative position comprises assessing relative angles between the two objects, and wherein the voltage change across the first load resistor indicates a change in an angular relationship between the objects.

44. The method of claim 36, further comprising:

applying a voltage across a second photoconductive active area formed of silicon on the first surface of the insulating substrate while the optical radiation illuminates the second active area;

measuring a voltage change across a second load resistor electrically connected in series with the second active area, the voltage change across the second load resistor being indicative of the change in the optical radiation;

comparing a time rate of change of the voltage across both of the first and second load resistors, a difference between the two measured time rates being indicative of spatial characteristics of the optical radiation.