TRACKING TYPE LASER INTERFEROMETER AND METHOD FOR RESETTING THE SAME

• US 20080316497A1
• Filed: 06/18/2008
• Published: 12/25/2008
• Est. Priority Date: 06/20/2007
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Taketomi, Naoyuki, Yanaka, Sinichirou
• Granted Patent: US 7,872,733 B2
• Time in Patent Office: Days
• US Class Current: 356/498
• CPC Class Codes: G01B 2290/15 Cat eye, i.e. reflection always parallel to incoming beam
• 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

Abstract

A tracking type laser interferometer that detects displacement of a retroreflector 300 being an object to be measured by utilizing interference of a laser beam 102 irradiated onto the retroreflector 300 and reflected by the retroreflector 300 in the returning direction, and carries out tracking by means of a two-axis turning mechanism 240 using displacement in the position of the optical axis of the laser beam 102; the same tracking type laser interferometer, includes; a light irradiator 600 that emits a fan-shaped laser light 602 that is fan-shaped including the optical axis of the laser beam 102, is interlocked with turning movements of the two-axis turning mechanism 240 around an axis orthogonal to the center axis of the corresponding fan shape; and a light receptor 620 that has a specific positional relationship with the retroreflector 300 or the light irradiator 600 and receives the fan-shaped laser light. Thereby, tracking can be automatically reset when the tracking is disabled due to a reason such as interruption of laser light or initial adjustment work can be automated when commencing measurement.

Claims

1. A tracking type laser interferometer that detects displacement of a retroreflector being an object to be measured by utilizing interference of a laser beam irradiated onto the retroreflector and reflected by the retroreflector in the returning direction, and carries out tracking by means of a two-axis turning mechanism using displacement in the position of the optical axis of the laser beam;

the same tracking type laser interferometer, comprising;

a light irradiator that emits a fan-shaped laser light that is fan-shaped including the optical axis of the laser beam, is interlocked with turning movements of the two-axis turning mechanism around an axis orthogonal to the center axis of the corresponding fan shape; and

a light receptor that has a specific positional relationship with the retroreflector or the light irradiator and receives the fan-shaped laser light.

2. The tracking type laser interferometer according to claim 1, wherein the light receptor is provided in the retroreflector.

3. The tracking type laser interferometer according to claim 1, wherein the light receptor is provided in the two-axis turning mechanism.

4. The tracking type laser interferometer according to claim 3, wherein the light receptor is fixed so that the optical axis when the fan-shaped laser light is emitted to the retroreflector and the optical axis when the laser light is reflected by the retroreflector and is received by the light receptor are common to each other at least on a part of the optical path.

5. The tracking type laser interferometer according to claim 3, wherein the light irradiator and the light detector including the light receptor is provided in the two-axis turning mechanism.

6. A method for resetting a tracking type laser interferometer that detects displacement of a retroreflector being an object to be measured by utilizing interference of a laser beam, which is irradiated onto the retroreflector, and is reflected by the retroreflector in the returning direction, and carries out tracking by means of a two-axis turning mechanism using a change in the position of the optical axis of the laser beam;

the same method comprising the steps of;

emitting a fan-shaped laser light having a fan shape on a plane including the optical axis of the laser beam from a light irradiator secured on the two-axis turning mechanism when no tracking control is carried out;

executing a turning movement centering around the axis orthogonal to the fan-shaped center axis of the two-axis turning mechanism;

detecting the fan-shaped laser light in a light receptor having a specific positional relationship with the retroreflector or the light irradiator;

obtaining a first turning angle by which tracking control is enabled;

moving to the first turning angle by turning centering around the axis orthogonal to the center axis of the fan shape;

executing turning movements of the remaining axes with the first turning angle maintained;

detecting the laser beam;

obtaining a second turning angle by which tracking control is enabled;

moving to the second turning angle by turning centering around the remaining axes so as to enable the tracking control.

7. The method for resetting a tracking type laser interferometer according to claim 6, wherein the light receptor is provided in the retroreflector.

8. The method for resetting a tracking type laser interferometer according to claim 6, wherein the light receptor is provided in the two-axis turning mechanism.

9. The method for resetting a tracking type laser interferometer according to claim 8, wherein the light receptor is fixed so that the optical axis when the fan-shaped laser light is emitted to the retroreflector and the optical axis when the laser light is reflected by the retroreflector and is received by the light receptor are common to each other at least on a part of the optical path.

10. The method for resetting a tracking type laser interferometer according to claim 8, wherein the light irradiator and the light detector including the light receptor is provided in the two-axis turning mechanism.