Optical Interferometer

Abstract

An optical interferometer (100) includes a first optical interferometer (200) disposed on a front surface side of a workpiece (W) and a second optical interferometer (300) disposed on a rear surface side of the workpiece (W). The first optical interferometer (200) and the second optical interferometer (300) each include a light emitting section (210, 310), a wire grid (220, 320) and an interference fringe sensor (230, 330). Wire alignment directions of the wire grid (220) of the first optical interferometer (200) and the wire grid (320) of the second optical interferometer (300) are orthogonal to each other. When no workpiece (W) is set, the wire grid (220) of the first optical interferometer (200) reflects light from the second optical interferometer (300) to generate object light and the wire grid (320) of the second optical interferometer (300) reflects light from the first optical interferometer (200) to generate object light.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an arrangement of an optical interferometer according to a first embodiment of the present invention;

FIG. 2 is a side elevational view of the optical interferometer showing a measurement in a measurement mode of the first embodiment;

FIG. 3 is a side elevational view of the optical interferometer showing a measurement in a calibration mode of the first embodiment;

FIG. 4 shows an arrangement of an interference fringe sensor according to a first modification of the invention;

FIG. 5 shows an example of a phase shift interference fringe acquired by the interference fringe sensor of the first modification;

FIG. 6 shows an arrangement of an interference fringe sensor according to a second modification of the invention;

FIG. 7 shows an arrangement of an interference fringe sensor according to a third modification of the invention;

FIG. 8 shows a Michelson interferometer as a related-art optical interferometer;

FIG. 9 shows how to match front surface data with rear surface data of a workpiece; and

FIG. 10 shows an arrangement in which the relater-art optical interferometers are disposed on a front surface side and a rear surface side of the workpiece.

Claims

1. An optical interferometer that measures change in thickness of a workpiece, comprising: a first optical interferometer disposed on a front surface side of the workpiece; anda second optical interferometer disposed on a rear surface side of the workpiece,

2. The optical interferometer according to claim 1, wherein the polarization separators each are a wire grid polarizer that has a plurality of wires aligned in parallel to each other, the polarization separators reflecting a component that is parallel to the plurality of wires and transmitting a component that is orthogonal to the plurality of wires, anda direction in which the plurality of wires are aligned of the wire grid polarizer of the first optical interferometer is not parallel to a direction in which the plurality of wires are aligned of the wire grid polarizer of the second optical interferometer.

3. The optical interferometer according to claim 1, wherein the polarization separator of the first optical interferometer and the polarization separator of the second optical interferometer are disposed such that the polarization axes thereof are orthogonal to each other.

4. The optical interferometer according to claim 2, wherein the polarization separator of the first optical interferometer and the polarization separator of the second optical interferometer are disposed such that the polarization axes thereof are orthogonal to each other.

5. The optical interferometer according to claim 1, wherein the light emitting section of the first optical interferometer and the light emitting section of the second optical interferometer include:a common light source; anda light guiding section that divides light from the common light source and respectively guides the divided light to optical paths of the first optical interferometer and the second optical interferometer.

6. The optical interferometer according to claim 2, wherein the light emitting section of the first optical interferometer and the light emitting section of the second optical interferometer include:a common light source; anda light guiding section that divides light from the common light source and respectively guides the divided light to optical paths of the first optical interferometer and the second optical interferometer.

7. The optical interferometer according to claim 3, wherein the light emitting section of the first optical interferometer and the light emitting section of the second optical interferometer include:a common light source; anda light guiding section that divides light from the common light source and respectively guides the divided light to optical paths of the first optical interferometer and the second optical interferometer.

8. The optical interferometer according to claim 4, wherein the light emitting section of the first optical interferometer and the light emitting section of the second optical interferometer include:a common light source; anda light guiding section that divides light from the common light source and respectively guides the divided light to optical paths of the first optical interferometer and the second optical interferometer.