Systems and methods for sensing position and movement

• US 4,767,973 A
• Filed: 07/06/1987
• Issued: 08/30/1988
• Est. Priority Date: 07/06/1987
• Status: Expired due to Fees

• Current Assignee: Sarcos Group
• Original Assignee: Sarcos Incorporated (Rtx Corporation)
• Inventors: Phillips, Richard P., Jacobsen, Stephen C., Wood, John E.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US07/070,349
• Time in Patent Office: 421 Days
• Field of Search: 318/652, 357/23.1, 357/52, 357/53, 357/85, 307/308, 324/72, 324/109, 324/457, 340/870.3
• US Class Current: 318/652
• CPC Class Codes: G01D 5/18 by varying effective impedance of discharge tubes or semiconductor devices
• CPC Class Codes: H04R 19/00 Electrostatic transducers
• CPC Class Codes: H04R 23/006 using solid state devices solid state devices per se H01L

Abstract

Sensor systems and methods for detecting the position and/or movement of an object in multiple degrees of freedom. The sensor system of the present invention comprises at least one field-effect transistor (FET), the geometrical configuration of the FET being selected so as to provide the desired sensitivity. The FET is preferably provided with a conductive gate adjacent to but insulated from the channel region of the FET. An object whose position and/or movement is to be detected is prepared such that an electric field emanates from the object.

The FET is brought into the vicinity of the object, and the electric field emanating from the object interacts with the gate and/or channel region of the FET so as to modify the magnitude of the electrical current flowing through the channel region. The current through the channel region is detected and is used to obtain information about the position and movement of the object relative to the channel region of the FET. By positioning a plurality of substantially coplanar FETs in the vicinity of the object, the position and/or movement of the object in any desired number of degrees of freedom can be detected and monitored.

Claims

1. A sensor system for detecting the position and movement of an object, the system comprising:

means for producing an electric field which emanates from the object;

a field-effect transistor positioned in the vicinity of the object so as to be located directly within said electric field, the field-effect transistor having a source region, a drain region, and a channel region, the source and drain regions being separated by the channel region; and

means for detecting variations caused by said electric field in the conductivity of the channel region of the field-effect transistor, whereby information about the position and movement of the object relative to the channel region of the field-effect transistor can be obtained.

2. A sensor system as defined in claim 1 wherein the electric field producing means comprises means for forming a bounded region having a non-zero net electrical charge.

3. A sensor system as defined in claim 2 wherein the bounded region forming means comprises an electret having a substantially constant, non-zero net electrical charge.

4. A sensor system as defined in claim 2 wherein the bounded region forming means comprises an electrical conductor having a substantially fixed voltage level.

5. A sensor system as defined in claim 1 wherein the electric field producing means comprises for forming a bounded region having a non-zero net electric polarization.

6. A sensor system as defined in claim 1 wherein the electric field is a non-uniform electric field.

7. A sensor system as defined in claim 1 wherein the field-effect transistor further comprises a conductive gate positioned adjacent to the channel region of the field-effect transistor.

8. A sensor system as defined in claim 7 wherein the conductive gate is formed of a conductive metal material.

9. A sensor system as defined in claim 7 wherein the conductive gate is formed of a polycrystalline silicon material.

10. A sensor system as defined in claim 7 wherein the conductive gate is electrically insulated from the channel region of the field-effect transistor.

11. A sensor system as defined in claim 7 wherein the conductive gate is substantially completely surrounded by an insulating material.

12. A sensor system as defined in claim 11 wherein the insulating material comprises silicon dioxide.

13. A sensor system as defined in claim 1 wherein the field-effect transistor further comprises a biasing contact positioned adjacent to the channel region of the field-effect transistor.

14. A sensor system as defined in claim 1 wherein the source region of the field-effect transistor is a substantially circular region and wherein the channel region and drain region of the field-effect transistor are substantially concentric, annular regions which encircle the source region.

15. A sensor system for detecting the position and movement of an object, the system comprising:

means for forming at least one bounded region having a non-zero net electrical charge, said bounded region being configured and positioned so as to produce a non-uniform electric field which emanates from the object;

at least one field-effect transistor positioned in the vicinity of the object, each field-effect transistor having a source region, a drain region, and a channel region, the source and drain regions being separated by the channel region, each field-effect transistor also comprising a conductive gate positioned adjacent to but electrically insulated from the channel region of the field-effect transistor; and

means for detecting variations caused by said electric field in the conductivity of the channel region of each field-effect transistor, whereby information about the position and movement of the object relative to the channel region of each field-effect transistor can be obtained.

16. A sensor system as defined in claim 15 wherein there are a plurality of field-effect transistors positioned in the vicinity of the object.

17. A sensor system as defined in claim 16 wherein the field-effect transistors are substantially co-planar.

18. A sensor system as defined in claim 16 wherein the field-effect transistors are positioned so as to be located directly within the electric field which emanates from the object.

19. A sensor system as defined in claim 18 wherein the conductive gate of each field-effect transistor is substantially completely surrounded by an insulating material.

20. A sensor system as defined in claim 19 wherein the conductive gate of each field-effect transistor is formed of a polycrystalline silicon material.

21. A sensor system as defined in claim 19 wherein the source region of each field-effect transistor is a substantially circular region and wherein the channel region and drain region of each field-effect transistor are substantially concentric, annular regions which encircle the source region.

22. A sensor system as defined in claim 19 wherein the bounded region forming means comprises an electret having a substantially constant, non-zero net electrical charge.

23. A sensor system as defined in claim 19 wherein the bounded region forming means comprises an electrical conductor having a substantially fixed voltage level.

24. A sensor system as defined in claim 19 wherein each field-effect transistor further comprises a biasing contact positioned adjacent to but insulated from the conductive gate.

25. A sensor system as defined in claim 15 wherein the field-effect transistors are n-channel field-effect transistors.

26. A sensor system as defined in claim 25 wherein the field-effect transistors have a negative threshold voltage.

27. A sensor system, comprising:

an object which comprises at least one electret having a substantially constant, non-zero net electrical charge, the electret being configured and positioned so as to produce a non-uniform electric field around the object;

a plurality of field-effect transistors positioned in the vicinity of the object so as to be located directly within said electric field, the field-effect transistors being substantially coplanar and each field-effect transistor having a source region, a drain region, and a channel region, the source and drain regions being separated by the channel region, each field-effect transistor also comprising a conductive gate positioned adjacent to but electrically insulated from the channel region of the field-effect transistor, the conductive gate being substantially completely surrounded by an insulating material; and

means for detecting variations caused by said electric field in the conductivity of the channel region of each field-effect transistor, whereby the position and movement of the object can be determined.

28. A sensor system as defined in claim 27 wherein the object comprises a plurality of electrets and wherein the electrets of the object are discrete, substantially linear regions which are substantially parallel to one another.

29. A sensor system as defined in claim 27 wherein the object is configured as a substantially circular disc and wherein the electret is configured as a substantially circular ring which is substantially concentric with the disc.

30. A sensor system as defined in claim 27 wherein the object comprises a flexible membrane and wherein the position and movement of the membrane are dependent upon the amount of pressure which is exerted upon the membrane.

31. A sensor system as defined in claim 27 wherein the object is a stereo phonograph needle.

32. A sensor system as defined in claim 27 wherein the drain region of each field-effect transistor is a substantially circular region and wherein the channel region and source region of each field-effect transistor are substantially concentric, annular regions which encircle the drain region.

33. A sensor system as defined in claim 27 wherein each field-effect transistor further comprises a biasing contact positioned adjacent to but insulated from the conductive gate.

34. A sensor system as defined in claim 27 wherein the means for detecting variations in conductivity comprises an operational amplifier.

35. A method for sensing the position and movement of an object, the method comprising the steps of:

preparing the object such that an electric field emanates from the object;

positioning at least one field-effect transistor in the vicinity of the object, the field-effect transistor having a source region, a drain region, and a channel region, the source and drain regions being separated by the channel region;

establishing an electrical voltage difference between the source region and drain region of the field-effect transistor; and

detecting variations caused by said electric field in the conductivity of the channel region of the field-effect transistor, whereby information about the position and movement of the object relative to the channel region of the field-effect transistor can be obtained.

36. A method as defined in claim 35 wherein the preparing step comprises preparing the object such that a non-uniform electric field emanates from the object.

37. A method as defined in claim 35 wherein the preparing step comprises providing the object with at least one bounded region having a non-zero net electrical charge.

38. A method as defined in claim 37 wherein said bounded region comprises an electret having a substantially constant, non-zero net electrical charge.

39. A method as defined in claim 37 wherein said bounded region comprises an electrical conductor having a substantially fixed voltage level.

40. A method as defined in claim 35 wherein the preparing step comprises providing the object with at least one bounded region having a non-zero net electric polarization.

41. A method as defined in claim 35 wherein the positioning step comprises positioning the field-effect transistor in the vicinity of the object so as to be located directly within said electric field.

42. A method as defined in claim 35 wherein the positioning step comprises positioning a plurality of field-effect transistors in the vicinity of the object.

43. A method as defined in claim 42 wherein the field-effect transistors are substantially coplanar.

44. A method as defined in claim 35 wherein the field-effect transistor comprises a biasing contact positioned adjacent to the channel region and further comprising the step of fixing the voltage level of the biasing contact so as to establish a desired reference point from which the position of the object is to be determined.