Displacement measurement apparatus and displacement measurement method

摘要

There is provided a displacement measurement apparatus including: a light source; a pair of diffraction gratings that light emitted from the light source enters, the pair of diffraction gratings opposing each other while being relatively movable along an optical axis; a first optical sensor that detects interference light obtained by diffracted light emitted from a diffraction grating device of each of the pair of diffraction gratings; a second optical sensor that detects non-interference light emitted from the pair of diffraction gratings; and a correction unit that corrects a signal obtained by the first optical sensor based on a signal obtained by the second optical sensor.

主权项

1. A displacement measurement apparatus, comprising:
a light source; a pair of diffraction gratings that light emitted from the light source enters, the pair of diffraction gratings opposing each other while being relatively movable along an optical axis; a first optical sensor that detects interference light obtained by diffracted light emitted from a diffraction grating device of each of the pair of diffraction gratings; a second optical sensor that detects non-interference light emitted from the pair of diffraction gratings; and an operation circuit that corrects a signal obtained by the first optical sensor based on a signal obtained by the second optical sensor, wherein the operation circuit is configured to determine whether a detection value of the signal obtained by the second optical sensor is within a redetermined range of a percentage of a change with respect to a reference value; and wherein the operation circuit is configured such that, if the operation circuit determines that the detection value is out of the range, it multiplies a detection value of the signal obtained by the first optical sensor by a coefficient corresponding to the percentage of a change, and outputs the obtained value.