Steerable retroreflective system and method

• US 6,420,694 B1
• Filed: 09/21/1999
• Issued: 07/16/2002
• Est. Priority Date: 09/21/1999
• Status: Expired due to Term

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Greenwood, Thomas A.
• Primary Examiner(s): ALLEN, STEPHONE B
• Application Number:
  US09/400,421
• Time in Patent Office: 1,029 Days
• Field of Search: 250/203.4, 250/221, 250/222.1, 356/138, 356/139.03, 356/139.04, 356/139.06, 356/139.07, 356/141.2, 359/152, 359/159, 359/171, 359/168-170, 700/108-110, 700/114, 700/192, 700/193
• US Class Current: 250/221
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves
• CPC Class Codes: G02B 5/122 cube corner, trihedral or triple reflector type

Abstract

A steerable retroreflective system is disclosed that includes a retroreflector that reflects at least some light incident upon the retroreflector, while permitting at least some of the incident light to leak therethrough. The steerable retroreflective system also includes an optical detector that detects leakage light that passes through the retroreflector. The steerable retroreflective system further includes means for controllably steering the retroreflector in response to the leakage light detected by the optical detector, such as to track the incident light. The method of controllably steering the retroreflector is also disclosed. The steerable retroreflective system and method therefore provides a retroreflective target with a much wider acceptance angle than conventional retroreflective targets. As a result, the retroreflective target can continue to be illuminated by a laser tracker and can continue to provide information indicative of the position of the retroreflective target as a machine tool on which the retroreflective target is mounted is moved during machining operations.

Claims

1. A steerable retroreflective system comprising:

a retroreflector for reflecting at least some light incident thereupon;

an optical detector for detecting leakage light that passes through said retroreflector, wherein said optical detector defines a target zone; and

means for controllably steering said retroreflector in response to the leakage light detected by said optical detector, wherein said means for controllably steering said retroreflector comprises;

at least one positioner for moving said retroreflector; and

a controller, responsive to said optical detector, for directing said at least one positioner to controllably steer said retroreflector to follow the incident light in response to the leakage light detected by said optical detector, wherein said controller steers said retroreflector to move the leakage light toward the target zone.

2. A steerable retroreflective system according to claim 1, wherein said at least one positioner comprises a plurality of motors for moving said retroreflector about respective axes.

3. A steerable retroreflective system comprising:

a retroreflector for reflecting at least some light incident thereupon, wherein said retroreflector comprises a trihedral prism having an input surface through which incident light is received and a plurality of reflective surfaces for reflecting the incident light, wherein said trihedral prism defines an at least partially transmissive window opposite the input surface such that leakage light passes through said window and escapes from said trihedral prism, wherein edges of said reflective surfaces define lines that intersect at an imaginary apex of said trihedral prism, and wherein said window is offset from the imaginary apex of said trihedral prism and is sized such that between about 0.5% and 5% of the light received through said input surface of said trihedral prism passes through said window;

an optical detector for detecting leakage light that passes through said retroreflector; and

means for controllably steering said retroreflector in response to the leakage light detected by said optical detector, wherein said means for controllably steering said retroreflector comprises;

at least one positioner for moving said retroreflector; and

a controller, responsive to said optical detector, for directing said at least one positioner to controllably steer said retroreflector in response to the leakage light detected by said optical detector.

4. A steerable retroreflective system comprising:

a trihedral prism having an input surface through which incident light is received and a plurality of reflective surfaces for reflecting the incident light, wherein said trihedral prism defines a window opposite the input surface such that said plurality of reflective surfaces converge at said window, said window being at least partially transmissive such that leakage light passes through said window and escapes from said trihedral prism;

an optical detector for detecting leakage light that passes through said trihedral prism;

at least one positioner for moving said trihedral prism; and

a controller, responsive to said optical detector, for directing said at least one positioner to controllably steer said trihedral prism in response to the leakage light detected by said optical detector.

5. A steerable retroreflective system comprising:

a trihedral prism having an input surface through which incident light is received and a plurality of reflective surfaces for reflecting the incident light, wherein said trihedral prism defines a window opposite the input surface such that said plurality of reflective surfaces converge at said window, said window being at least partially transmissive such that leakage light passes through said window and escapes from said trihedral prism wherein edges of said reflective surfaces define lines that intersect at an imaginary apex of said trihedral prism, and wherein said window is offset from the imaginary apex of said trihedral prism;

an optical detector for detecting leakage light that passes through said trihedral prism;

at least one positioner for moving said trihedral prism; and

a controller, responsive to said optical detector, for directing said at least one positioner to controllably steer said trihedral prism in response to the leakage light detected by said optical detector.

6. A steerable retroreflective system according to claim 5, wherein said reflective surfaces are mirrored, and wherein the window is free of any mirrored coating.

7. A steerable retroreflective system according to claim 5, wherein said window is sized such that between about 0.5% and 5% of the light received through said input surface of said trihedral prism passes through said window.

8. A steerable retroreflective system according to claim 7, wherein said window is sized such that about 1% of the light received through said input surface of said trihedral prism passes through said window.

9. A steerable retroreflective system according to claim 5, wherein said at least one positioner comprises a plurality of motors for moving said trihedral prism about respective axes.

10. A steerable retroreflective system according to claim 5, wherein said controller steers said trihedral prism to follow the incident light.

11. A method of controllably steering a retroreflector comprising:

illuminating the retroreflector with light incident thereupon, wherein the retroreflector comprises a trihedral prism having an input surface through which the incident light is received and a plurality of reflective surfaces for reflecting the incident light, wherein the trihedral prism defines a window opposite the input surface such that the plurality of reflective surfaces converge at the window, the window being at least partially transmissive such that leakage light passes through the window and escapes from the trihedral prism, wherein edges of the reflective surfaces define lines that intersect at an imaginary apex of said trihedral prism, and wherein the window is offset from the imaginary apex of the trihedral prism;

detecting the leakage light that passes through the window of the retroreflector; and

controllably steering the retroreflector in response to the detected leakage light, wherein controllably steering the retroreflector comprises controllably steering the retroreflector to follow the incident light.

12. A method of according to claim 11, wherein controllably steering the retroreflector comprises controllably steering the retroreflector in each of a plurality of directions.

13. A method according to claim 11 further comprising allowing between about 0.5% and 5% of the light illuminating the retroreflector to leak therethrough and be detected.