Multiple fanned laser beam metrology system

• US 20070103699A1
• Filed: 04/19/2006
• Published: 05/10/2007
• Est. Priority Date: 11/09/2005
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Liu, Ketao, Bender, Douglas, Kohnen, Kirk, McVey, Ray, Becker, Gregory, Guthrie, Richard, Lundgren, Mark, Liu, John, Sedivec, Peter
• Granted Patent: US 7,787,134 B2
• Time in Patent Office: Days
• US Class Current: 356/620
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/48 Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

Systems and techniques for laser metrology. Two or more fanned probe beams are scanned relative to a surface including one or more targets. A position detection module receives return beam information from the fanned probe beams, and determines a position of at least a first target of the one or more targets based on the return beam information.

Claims

1. A metrology system comprising:

a scanner configured to generate relative motion of a first fanned probe beam and a second fanned probe beam with respect to a surface including a first target about a scan axis;

a light source system configured to generate the first fanned probe beam having a first wavelength, a first modulation frequency, and a first tilt angle with respect to the scan axis, the light source system further configured to generate the second fanned probe beam having a second different wavelength, a second different modulation frequency, and a second different tilt angle with respect to the scan axis; and

a position detection module configured to receive a first reflected return beam having the first wavelength and first modulation frequency from the first target and to receive a second reflected return beam having the second wavelength and the second modulation frequency from the first target and configured to determine a position of the first target using information indicative of the first return beam and the second return beam.

2. The system of claim 1, wherein the position detection module is configured to determine the position of the first target using a range and a scan angle associated with the first return beam.

3. The system of claim 2, wherein the position detection module is further configured to determine the position of the first target using a range and a scan angle associated with the second return beam.

4. The system of claim 1, wherein the information indicative of the first return beam includes a range, and wherein the position detection module includes a phase processing module configured to determine the range using phase information associated with the first modulation frequency and phase information associated with the first return beam.

5. The system of claim 1, wherein the light source system comprises a first laser source in communication with an amplitude modulation driver system configured to drive the first laser at the first modulation frequency.

6. The system of claim 1, wherein the scanner comprises a scanning mirror, and wherein the system further comprises an angular measurement sensor in communication with the scanning mirror and configured to generate a signal indicative of a scan angle of the mirror.

7. A metrology system comprising:

scanning means for generating relative motion of a first fanned probe beam and a second fanned probe beam with respect to a surface including a first target about a scan axis;

means for generating the first fanned probe beam having a first wavelength, a first modulation frequency, and a first tilt angle with respect to the scan axis;

means for generating the second fanned probe beam having a second different wavelength, a second different modulation frequency, and a second different tilt angle with respect to the scan axis; and

means for receiving a first reflected return beam having the first wavelength and first modulation frequency from the first target;

means for receiving a second reflected return beam having the second wavelength and the second modulation frequency from the first target; and

means for determining a position of the first target using information indicative of the first return beam and the second return beam.

8. The system of claim 7, wherein the means for determining the position of the first target comprises means for determining the position of the first target using a range and a scan angle associated with the first return beam.

9. The system of claim 8, wherein the means for determining the position of the first target comprises means for determining the position of the first target using a range and a scan angle associated with the second return beam.

10. The system of claim 7, wherein the information indicative of the first return beam includes a range, and wherein the means for determining the position of the first target includes a means for determining the range using phase information associated with the first modulation frequency and phase information associated with the first return beam.

11. The system of claim 7, wherein the means for generating a first fanned probe beam comprises a first laser source in communication with an amplitude modulation driving means for modulating the amplitude of the first laser at the first modulation frequency.

12. The system of claim 7, wherein the scanning means comprises a scanning mirror, and wherein the system further comprises an angular measurement sensor in communication with the scanning mirror and configured to generate a signal indicative of a scan angle of the mirror.

13. A method of determining a three-dimensional position of a first target comprising:

generating a first probe beam having a first wavelength, a first amplitude modulation frequency, and a first tilt angle with respect to a scan axis;

generating a second probe beam having a second wavelength, a second amplitude modulation frequency, and a second tilt angle with respect to the scan axis;

scanning the first probe beam and the second probe beam about the scan axis;

reflecting from the first target the first probe beam as a first reflected beam;

detecting the first reflected beam;

determining a first range and a first scan angle based on detecting the first reflected beam;

reflecting from the first target the second probe beam as a second reflected beam;

detecting the second reflected beam;

determining a second range and a second scan based on detecting the second reflected beam; and

determining the three-dimensional position of the first target using the first range, the second range, the first scan angle, and the second scan angle.

14. The method of claim 13, wherein the first target is a retro-reflective target.

15. The method of claim 13, wherein determining the first scan angle comprises determining the first scan angle based on an angular position of a scanner at a time at which the first reflected beam is received and a correction factor indicative of the first range and a scan rate.

16. The method of claim 13, wherein the first probe beam is generated using a driver configured to drive a light source at the first modulation frequency, and wherein determining the first range comprises determining the first range using a phase of the first reflected beam and a phase of an output of the driver.