Optical design for laser encoder resolution extension with three-dimensional motion decoupling

• US 6,822,733 B1
• Filed: 06/30/2003
• Issued: 11/23/2004
• Est. Priority Date: 06/30/2003
• Status: Expired due to Term

• Current Assignee: U Chicago Argonne, LLC
• Original Assignee: University of Chicago
• Inventors: Shu, Deming
• Primary Examiner(s): Gregory, Bernarr E.
• Assistant Examiner(s): Andrea, Brian
• Application Number:
  US10/610,192
• Time in Patent Office: 512 Days
• Field of Search: 356/4-1-, 356/152--15, 356/614, 356/139.03, 356/138.1
• US Class Current: 356/152.3
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01D 2205/95 Three-dimensional encoders, i.e. having codes extending in three directions
• CPC Class Codes: G01D 5/347 using displacement encoding scales
• CPC Class Codes: G01D 5/34715 Scale reading or illumination devices

Abstract

An optical system is provided for laser encoder resolution extension with three-dimensional motion decoupling capability. The optical system includes a first prism mounted on a moving target, and a plurality of prisms, a retroreflector, a laser source, and a detector mounted on a fixed base. The moving target has three-dimensional linear motion freedom. The first prism on the moving target and the plurality of prisms and the retroreflector on the fixed base reflect a laser beam from the laser source to the detector define a three-dimensional optical path. The three-dimensional optical path provides multiple times optical resolution extension power for linear displacement measurement and encoding. This optic system is only sensible to the target motion on X direction and is substantially unaffected by movement in the Y and Z directions.

Claims

1. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability comprising:

a moving target;

said moving target having three-dimensional linear motion freedom;

a fixed base positioned laterally spaced apart in an X direction from said moving target;

a single first prism mounted on said moving target,

a plurality of prisms, a retroreflector, a laser source, and a detector mounted on said fixed base;

said single first prism being larger than said plurality of prisms;

a three-dimensional optical path defined by said first prism, said plurality of prisms, and said retroreflector for reflecting a laser beam from said laser source to said detector with said laser beam being reflected multiple times between said single first prism and each of said plurality of prisms;

said three-dimensional optical path providing multiple times optical resolution extension power for linear displacement measurement and encoding;

said optical system being sensitive to a motion of said moving target in said X direction and being substantially unaffected by movement in a Y direction and a Z direction.

2. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 wherein said retroreflector provides a self-alignment capability within said three-dimensional optical path.

3. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 wherein said first prism mounted on said moving target includes a right angle prism.

4. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 wherein said plurality of prisms mounted on said fixed base includes a plurality of right angle prisms.

5. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 wherein said laser source includes a laser source housing and wherein said detector is arranged coaxially in a laser source housing.

6. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 5 wherein said retroreflector reflects the laser beam back to said laser source following said three-dimensional optical path to said detector.

7. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 wherein said detector includes a heterodyning detector.

8. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 wherein said laser source includes a frequency-stabilized laser source.

9. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 wherein said three-dimensional optical path provides twelve times optical resolution extension power for linear displacement measurement and encoding.

10. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 wherein said three-dimensional optical path provides twenty-four times optical resolution extension power for linear displacement measurement and encoding.

11. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 includes a first optical design configuration wherein said plurality of prisms mounted on the fixed base include at least one pair of prisms arranged substantially laterally aligned in spaced apart planes and at least one prism laterally offset and vertically spaced apart from said at least one pair of prisms.

12. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 11 wherein said first prism mounted on said moving target includes a right angle prism and wherein said at least one pair of prisms and said at least one laterally offset prism include right angle prisms.

13. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 11 wherein each of said at least one pair of prisms is larger than said at least one laterally offset prism.

14. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 11 wherein said three-dimensional optical path provides twelve times optical resolution extension power for linear displacement measurement and encoding.

15. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 11 wherein said three-dimensional optical path provides twenty-four times optical resolution extension power for linear displacement measurement and encoding.

16. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 1 includes a second optical design configuration wherein said plurality of prisms mounted on the fixed base include at least one pair of elongated prisms arranged substantially aligned in spaced apart planes and at least one prism disposed near an upper plane between said at least one pair of elongated prisms.

17. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 16 wherein said first prism mounted on said moving target includes a right angle prism and wherein said at least one pair of elongated prisms and said at least one prism include right angle prisms.

18. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 16 wherein each of said at least one pair of elongated prisms is larger than said at least one prism.

19. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 16 wherein said three-dimensional optical path provides twelve times optical resolution extension power for linear displacement measurement and encoding.

20. An optical system for laser encoder resolution extension with three-dimensional motion decoupling capability as recited in claim 16 wherein said three-dimensional optical path provides twenty-four times optical resolution extension power for linear displacement measurement and encoding.