Method and system for determining surface profile information

• US 4,850,712 A
• Filed: 02/01/1988
• Issued: 07/25/1989
• Est. Priority Date: 02/01/1988
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Abshire, James B.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US07/150,603
• Time in Patent Office: 540 Days
• Field of Search: 356/373, 356/375, 356/376, 250/205, 219/124.34
• US Class Current: 356/602
• CPC Class Codes: B23Q 35/128 Sensing by using optical means

Abstract

A system determines the surface profile of an object. Systems of this kind are used in industrial robots, such as automatic welders. The severe operating environment requires a vision system with noise immunity along with accuracy. A beam splitter enables the use of discrete optical detectors which eliminate many problems inherent with previously used detectors, such as diode arrays and TV cameras. Additionally, an automatic gain control alters the intensity of a generated optical beam in response to the reflectivity of the surface. These features increase the accuracy and noise immunity of an optical vision system for use in sever industrial applications.

Claims

1. A system for determining profile information from the surface of an object, comprising:

an optical beam source for generating an optical beam for application to the surface;

means for receiving a reflected optical beam from the surface;

means for splitting said received reflected optical beam into a first portion and a second portion;

optical detecting means for producing a first signal and a second signal in response to the magnitude of said first portion and said second portion, respectively; and

processing means for determining the profile of said surface in response to the respective magnitudes of successive first and second signals wherein said processing means divides a difference of the first and second signals by the sum of the first and second signals to derive a beam position signal.

2. The system, as set forth in claim 1, wherein said receiving means includes a fiber optic bundle.

3. The system, as set forth in claim 1, wherein said splitting means includes a variable beam splitter.

4. The system, as set forth in claim 3, wherein the magnitude of the first and second portions are responsive to location of the reflected beam on said variable beam splitter.

5. The system, as set forth in claim 3, further comprising a lens arrangement for focusing said reflected optical beam onto said variable beam splitter.

6. The system, as set forth in claim 1, wherein said optical detecting means includes a first optical detector for receiving said first beam portion, and a second optical detector for receiving said second beam portion.

7. The system, as set forth in claim 6, wherein said optical detecting means includes a first lens adapted to focus said first beam portion onto said first optical detector, and a second lens adapted to focus said second beam portion onto said second optical detector.

8. The system, as set forth in claim 1, wherein said processing means determines the profile of the surface in response to successive beam position signals.

9. The system, as set forth in claim 1, further comprising:

means for scanning said generated optical beam in a predefined path along the surface at a first preselected rate.

10. The system, as set forth in claim 9, wherein said receiving means scans across said predefined path at a second preselected rate.

11. The system, as set forth in claim 10, wherein said second preselected rate is greater than said first preselected rate.

12. The system, as set forth in claim 1, further comprising:

means for automatically controlling the gain of said generated optical beam in response to the magnitude of said received reflected optical beam.

13. The system, as set forth in claim 12, wherein said automatic gain control means sums said first portion with said second portion, and delivers a feedback signal having a magnitude correlative to said sum.

14. The system, as set forth in claim 13, wherein said feedback signal is compared to a preselected setpoint signal to produce a control signal.

15. The system, as set forth in claim 14, further comprising means for altering the magnitude of said generated optical beam in response to said control signal.

16. A system for determining profile information from the surface of an object, comprising:

an optical beam source for generating an optical beam for application to the surface;

means for receiving a reflected optical beam from the surface, and applying the reflected optical beam onto an image plane;

a variable beam splitter being adapted to receive the reflected optical beam from the image plane and pass a first portion of said beam and reflect a second portion of said beam;

optical detecting means for producing a first signal and a second signal in response to the magnitude of said first portion and said second portion, respectively; and

processing means for determining the position of said reflected optical beam on said variable beam splitter in response to said first and second signals wherein said processing means divides a difference of the first and second signals by the sum of the first and second signals to derive a beam position signal.

17. The system, as set forth in claim 16, where in said receiving means includes a fiber optic bundle.

18. The system, as set forth in claim 16, wherein the magnitude of the first and second portions are responsive to location of the reflected beam on said variable beam splitter.

19. The system, as set forth in claim 16, wherein said optical detecting means includes a first optical detector for receiving said first beam portion, and a second optical detector for receiving said second beam portion.

20. The system, as set forth in claim 19, wherein said optical detecting means includes a first lens adapted to focus said first beam portion onto said first optical detector, and a second lens adapted to focus said second beam portion onto said second optical detector.

21. The system, as set forth in claim 16, further comprising a lens arrangement for focusing said reflected optical beam onto said variable beam splitter.

22. The system, as set forth in claim 16, wherein said processing means includes:

means for determining the profile of the surface in response to successive beam position signals.

23. The system, as set forth in claim 16, further comprising:

means for scanning said generated optical beam in a predefined path along the surface at a first preselected rate.

24. The system, as set forth in claim 23, wherein said receiving means scans across said predefined path at a second preselected rate.

25. The system, as set forth in claim 24, wherein said second preselected rate is greater than said first preselected rate.

26. The system, as set forth in claim 16, further comprising:

means for automatically controlling the gain of said generated optical beam in response to the magnitude of said received reflected optical beam.

27. The system, as set forth in claim 26, wherein said automatic gain control means sums said first portion with said second portion, and delivers a feedback signal having a magnitude correlative to said sum.

28. The system, as set forth in claim 27, wherein said feedback signal is compared to a preselected setpoint signal to produce a control signal.

29. The system, as set forth in claim 28, further comprising means for altering the magnitude of said generated optical beam in response to said control signal.