Laser interferometer

A laser interferometer comprising:

• a laser light source configured to emit laser light toward an object;
• an optical modulator including a vibrator configured to modulate the laser light using the vibrator and superimpose a modulation signal on the laser light;
• a photodetector configured to receive the laser light including a sample signal derived from the object and the modulation signal, and to output a light reception signal;
• a demodulation circuit configured to demodulate the sample signal from the light reception signal based on a reference signal;
• and
• an oscillation circuit configured to operate using the vibrator as a signal source and output the reference signal to the demodulation circuit, wherein
• the vibrator includes a vibration substrate having a base portion and a vibration unit coupled to the base portion,
• the vibration unit vibrates along an in-plane direction of the vibration substrate,
• the vibration unit includes a side surface intersecting with the in-plane direction, and
• the side surface is irradiated with the laser light.