Patent ID: 11879730
Assignee: SEIKO EPSON CORPORATION
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 4:
5. A laser interferometer, comprising:
a light source configured to emit a first laser light;
a beam splitter configured to split the first laser light is split into a first polarized light and a second polarized light;
an optical modulator that includes a vibrator, wherein
the optical modulator is configured to modulate the first polarized light by using the vibrator to generate a second laser light including a modulated signal,
the second polarized light is reflected by an object to be measured, and
the reflected second polarized light generates a third laser light including a sample signal;

a photodetector configured to receive an interference light to output a light reception signal, wherein the interference light is between the third laser light and the second laser light;
an optical path length variable section configured to change an optical path length of an optical path through which the second laser light propagates, wherein
the optical path of the second laser light is between the optical modulator and the photodetector via the beam splitter,
the optical path length is one of equal to or more than an optical distance, and
the optical distance corresponds to a wavelength of the first laser light;

a demodulation circuit that includes a first signal path and a second signal path, wherein the demodulation circuit is configured to:
demodulate the sample signal from a first light reception signal that is the light reception signal passed through the first signal path and a second light reception signal that is the light reception signal passed through the second signal path;
detect a maximum amplitude of the first light reception signal and record the detected maximum amplitude as a first recording maximum amplitude when the optical path length is changed by the optical path length variable section;
detect a maximum amplitude of the second light reception signal and record the detected maximum amplitude as a second recording maximum amplitude when the optical path length is changed by the optical path length variable section;
adjust the maximum amplitude of the first light reception signal based on the first recording maximum amplitude; and
adjust the maximum amplitude of the second light reception signal based on the second recording maximum amplitude.