Non-contact capacitance based image sensing method and system

• US 5,281,921 A
• Filed: 04/24/1990
• Issued: 01/25/1994
• Est. Priority Date: 04/24/1990
• Status: Expired due to Fees

• Current Assignee: Sandia Corporation (Martin Marietta Corporation)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Wiczer, James J., Novak, James L.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US07/514,051
• Time in Patent Office: 1,372 Days
• Field of Search: 324/661, 324/662, 324/663, 324/671, 324/686, 324/687, 324/690, 382/58
• US Class Current: 324/671
• CPC Class Codes: G01B 7/34 for measuring roughness or irregularity of surfaces

Abstract

A system and a method for imaging desired surfaces of a workpiece. A sensor having first and second sensing electrodes which are electrically isolated from the workpiece is positioned above and in proximity to the desired surfaces of the workpiece. An electric field is developed between the first and second sensing electrodes of the sensor in response to input signals being applied thereto and capacitance signals are developed which are indicative of any disturbances in the electric field as a result of the workpiece. An image signal of the workpiece may be developed by processing the capacitance signals. The image signals may provide necessary control information to a machining device for machining the desired surfaces of the workpiece in processes such as deburring or chamfering. Also, the method and system may be used to image dimensions of weld pools on a workpiece and surfaces of glass vials. The sensor may include first and second preview sensors used to determine the feed rate of a workpiece with respect to the machining device.

Claims

1. A method for sensing discontinuities on desired surfaces of a workpiece, said workpiece being electrically isolated at low frequencies from sensing means, comprising the steps of:

developing an electric field between first and second electrodes of said sensing means; and

sensing any effects on said electric field produced by said workpiece being disposed within said electric field;

said step of sensing any effects on said electric field corresponds to disturbances of said electric field for imaging the desired surfaces of the workpiece.

2. A method according to claim 1, wherein said sensing means comprises an array of first and second sensing electrodes.

3. A method for imaging desired surfaces of a workpiece, comprising the steps of:

(a) positioning sensor means above and in proximity to the workpiece;

(b) developing an electric field between first and second sensing electrodes of said sensor means in response to input signals applied to said sensor means;

(c) changing the locations of said sensor means with respect to the desired surfaces of the workpiece;

(d) developing coordinate signals indicative of the location of said sensor means with respect to the location of the workpiece in response to said step (c);

(e) sensing any effects in said electric field produced by the workpiece being disposed with said electric field and developing output display signals corresponding thereto; and

(f) imaging the desired surfaces of the workpiece in response to said output display and coordinate signals developed at said steps (d) and (e).

4. A method according to claim 3, wherein said sensor means comprises an array of first and second sensing electrodes.

5. A method according to claim 3, wherein the desired surfaces imaged at said step (f) comprise desired weld pools of the workpiece so that the width, height, thickness and back-side penetration of the desired weld pools on the workpiece are imaged;

said step (c) changes the location of said sensor means with respect to the desired weld pools of the workpiece, and said step (f) images the width, height, thickness and back-side penetration of the desired weld pools in response to said steps (d) and (e).

6. A method according to claim 5, wherein said step (f) images relative width, height, thickness and back side penetration for the desired weld pools according to the frequency of any effects in said electric field sensed at said step (e).

7. A method according to claim 3, wherein the desired surfaces imaged at said step (f) comprise desired surfaces of a glass vial, said step (c) changes the location of said sensor means with respect to the desired surfaces of the glass vial, and said step (f) images the desired surfaces of the glass vial in response to said steps (d) and (e).

8. A system for sensing discontinuities in desired surfaces of a workpiece, comprising:

sensing means having fist and second sensing electrodes and being electrically isolated from said workpiece;

field generating means for developing an electric field between first and second sensing electrodes; and

field sensing means for sensing any effects on said electric field by said workpiece being disposed within said electric field, said field sensing means detecting discontinuities on the desired surfaces of said workpiece corresponding to disturbances of said electric field for imaging the desired surfaces of the workpiece.

9. A system according to claim 8, wherein said sensing means comprises an array of first and second sensing electrodes.

10. A system for imaging desired surfaces of a workpiece, comprising:

sensor means being positioned above and in proximity to the workpiece for monitoring the desired surfaces of the workpiece;

field generating means for generating an electric displacement field between first and second sensing electrodes of said sensor means by applying input signals to said sensor means;

driving means for changing the location of said sensor means with respect to the desired surfaces of the workpiece generating coordinate signals indicative of location of said sensor means with respect to the desired surfaces of the workpiece;

detection means for sensing any effects in said electric displacement field in response to said sensor means being driven by said driving means; and

processing means for imaging the desired surfaces in response to any effects in said electric displacement field sensed by said detection means and said coordinate signals from said driving means.

11. A system according to claim 10, wherein said first sensing electrode receives said input signals and said second sensing electrode develops capacitance signals in response to any effects in said electric field.

12. A system according to claim 10, wherein said sensor means comprises an array of first and second sensing electrodes.

13. A system according to claim 12, wherein said array of first and second sensing electrodes comprises a plurality of first sensing electrodes for receiving said input signals and a plurality of second sensing electrodes for developing capacitance signals in response to any effects in said electric field.

14. A system according to claim 10, wherein the desired surfaces imaged by said processing means comprise desired weld pools of the workpiece so that the width, height, thickness and back-side penetration of desired weld pools on the workpiece are imaged, said sensor means is positioned above and in proximity to the workpiece for imaging the desired weld pools on the workpiece, said driving means changes the location of said sensor means with respect to the desired weld pools of the workpiece and developing coordinate signals indicative of the location of said sensor means with respect to the desired weld pools of the workpiece, and said processing means develops image signals of the desired weld pools in response to any effects in said electric field sensed by said detection means and said coordinate signals from said driving means.

15. A system according to claim 14, wherein said first sensing electrode receives said input signals and said second sensing electrode develops capacitance signals corresponding to any disturbances in said electric field.

16. A system according to claim 14, wherein said sensing means comprises an array of first and second sensing electrodes.

17. A system according to claim 16, wherein said array of first and second sensing electrodes comprises a plurality of first sensing electrodes for receiving said input signals and a plurality of second sensing electrodes for developing capacitance signals corresponding to any disturbances in said electric field.

18. A system according to claim 10, wherein the desired surfaces imaged by said processing means comprise desired surfaces of a glass vial, wherein said sensor means is positioned above and in proximity to the glass vial for imaging the desired surfaces of the glass vial, said driving means changes the location of said sensor means with respect to the desired surfaces of the glass vial and developing coordinate signals indicative of the location of said sensor means with respect to the desired surfaces of the glass vial, and said processing means develops image signals in response to any effects in said electric field sensed by said detection means and coordinate signals from said driving means.

19. A system according to claim 18, wherein said first sensing electrode receives said input signals and said second sensing electrode develops capacitance signals corresponding to any disturbances in said electric field.

20. A system according to claim 18, wherein said sensing means comprises an array of first and second sensing electrodes.

21. A system according to claim 20, wherein said array of first and second sensing electrodes comprises a plurality of input electrodes for receiving said input signals and a plurality of second sensing electrodes for developing capacitance signals corresponding to any disturbances in said electric field.