Probing retroreflector and methods of measuring surfaces therewith

• US 5,530,549 A
• Filed: 05/24/1994
• Issued: 06/25/1996
• Est. Priority Date: 05/24/1994
• Status: Expired due to Term

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: SpatialMetrix Corporation (Faro Technologies Incorporated)
• Inventors: Brown, Lawrence B.
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US08/248,150
• Time in Patent Office: 763 Days
• Field of Search: 356/375, 356/376
• US Class Current: 356/622
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/74 Systems using reradiation of electromagnetic waves other than radio waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 17/89 for mapping or imaging

Abstract

A probing retroreflector for determining the location and dimensions of a target in conjunction with optical measuring systems, such as tracking laser interferometers. The probing retroreflector comprises a support, a retroreflector assembly coupled to the support and having a center point, a planar reflector coupled to the support for reflecting light towards and receiving light from the retroreflector assembly, and a sensor such as a slender probe coupled to an end of the support. The center point of the retroreflector assembly is located at a position which represents the virtual location of the center point of the sensor, so that the location of the point on the surface to be measured, which is sensed by the sensor, can be accurately determined by the optical measuring system.

Claims

1. A method of measuring the dimensions of a surface comprising the steps of

directing a light beam generally towards the surface from a range measuring means, located at a reference position, for measuring dimensions of the surface,

reflecting the light beam away from the surface and towards a point in space which represents the virtual location of a point on the surface,

retroreflecting the light beam in the opposite direction and in a substantially parallel manner,

reflecting the light beam generally away from the surface to the range measuring means, and

periodically moving the point in space relative to the surface and determining the location of the point in space from the reference position using the reflected light beam and the range measuring means.

2. A method according to claim 1, wherein the light beam is a coherent light beam.

3. A method according to claim 1, wherein the light beam is a laser beam.

4. A method according to claim 1, wherein

the directing step includes the steps of splitting the light beam into two parts, directing the first part of the light beam towards the target, and directing the second part of the light beam into the range measuring means, and

the second reflecting step is followed by the step of directing the first part of the light beam into the range measuring means to determine the distance of the target from the reference position.

5. A method of measuring the dimensions of a surface using a laser interferometer comprising the steps of

directing a light beam generally towards the surface from a source including the laser interferometer located at a reference position,

reflecting the light beam away from the surface and towards a point in space which represents the virtual location of a point on the surface,

retroreflecting the light beam in the opposite direction and in a substantially parallel manner,

reflecting the light beam generally away from the surface and generally towards the reference position, and

periodically moving the point in space relative to the surface and determining the location of the point in space from the reference position using the reflected light beam and the laser interferometer.

6. A method of determining the location of a target in space comprising the steps of

directing a light beam generally towards the target from a ranging measuring means, located at a reference position, for measuring dimensions of the surface,

reflecting the light beam away from the target and towards a point in space which represents the virtual location of a point on the target,

retroreflecting the light beam in the opposite direction and in a substantially parallel manner,

reflecting the light beam generally away from the target to the range measuring means, and

determining the location of the point in space from the reference position using the reflected light beam and the range measuring means.

7. A method according to claim 6, wherein the light beam is a coherent light beam.

8. A method according to claim 6, wherein the light beam is a laser beam.

9. A method according to claim 6, wherein

the directing step includes the steps of splitting the light beam into two parts, directing the first part of the light beam towards the target, and directing the second part of the light beam into the range measuring means, and

the second reflecting step is followed by the step of directing the first part of the light beam into the range measuring means to determine the distance of the target from the reference position.

10. A method of determining the location of a target in space using a laser interferometer comprising the steps of

directing a light beam generally towards the target from a source including the laser interferometer located at a reference position,

reflecting the light beam away from the target and towards a point in space which represents the virtual location of a point on the target,

retroreflecting the light beam in the opposite direction and in a substantially parallel manner,

reflecting the light beam generally away from the target and generally towards the reference position, and

determining the location of the point in space from the reference position using the reflected light beam and the laser interferometer.

11. A method of retroreflecting a light beam used to provide location information of a target in space, comprising the steps of

directing the light beam generally towards the target from a range measuring means, located at a reference location, for providing location information of the target,

reflecting the light beam away from the target and towards a a point in space which represents the virtual location of a point on the target,

retroreflecting the light beam in the opposite direction and in a substantially parallel manner,

reflecting the light beam generally away from the target to the range measuring means.

12. A method according to claim 11, and further comprising the step of

determining at least one of the x, y and z coordinates of the point in space relative to the reference position using the light beam.

13. A method according to claim 11, wherein

the directing step includes the step of splitting the light beam into two parts.

14. A method according to claim 13, wherein

the splitting step includes the steps of directing the first part of the light beam towards the target and directing the second part of the light beam into the range measuring means.

15. A method according to claim 14, wherein

the second reflecting step is followed by the step of directing the first part of the light beam into the range measuring means to determine the distance of the target from the reference position.

16. A retroreflector, the combination comprising:

a support having a central axis A;

retroreflector means, coupled to said support, for receiving a light beam and reflecting the beam in the form of an output beam parallel to the input beam, said retroreflector means having a central axis B and a center point C;

planar reflector means, coupled to said support, for reflecting a light beam from a range measuring means onto said retroreflector means and for reflecting a light beam from said retroreflector means towards the range measuring means, and

sensor means, coupled to said support, for sensing the location of a target, said sensor means and said retroreflector means center point C being substantially equidistant from and on opposite sides of a plane D containing said planar reflector means;

said sensor means and said retroreflector center point C lying on a line E which is substantially perpendicular to said plane D;

said planar reflector means being oriented at an angle of greater than 0° and

less than 180°

to said retroreflector means central axis B.

17. A retroreflector according to claim 16, wherein said retroreflector means comprises a corner cube.

18. A retroreflector according to claim 16, wherein

said planar reflector means comprises a front surface planar mirror.

19. A retroreflector according to claim 16, wherein said sensor means comprises a probe.

20. A retroreflector according to claim 16, wherein

said sensor means comprises a probe having a substantially spherical distal end.

21. A retroreflector according to claim 16, wherein

said retroreflector means comprises a corner cube,

said planar reflector means comprises a front surface planar mirror, and

said sensor means comprises a probe having a substantially spherical distal end.

22. A retroreflector according to claim 16, wherein

said planar retroreflector means is oriented at an angle of about 60°

to said retroreflector means central axis B.

23. A retroreflector according to claim 16, wherein said sensor means comprises a reticle.

24. A retroreflector according to claim 16, wherein

said sensor means comprises means for optically aligning the target with said support.