Laser interferometer

A laser interferometer comprising:

• a light source configured to emit first laser light;
• a beam splitter configured to split the first laser light in a first part of the first laser light towards an optical modulator and a second part of the first laser light towards an optical path switching unit;
• the optical modulator including a vibrator and configured to modulate, by the vibrator, the first part of the first laser light into second laser light having a different frequency;
• the optical path switching unit disposed in a first optical path through which the second part of the first laser light travels and configured to switch a direction of travel of the second part of the first laser light between the first optical path and a second optical path different from the first optical path;
• a reflector including a light-reflecting surface configured to move along the second optical path and reflect the second part of the first laser light traveling through the second optical path;
• and
• a photoreceptor configured to
• receive first interference light of the second laser light and third laser light generated by reflection of the second part of the first laser light on an object to be measured, and second interference light of the second laser light and fourth laser light generated by reflection of the second part of the first laser light on the light-reflecting surface, and
• output a light-receiving signal.