| 摘要 |
<p>The instability of a signal light beam or a reference light beam in an interferometer is detected and fed back to the interferometer to allow the interferometer to compensate the instability, and the stability is ensured. In an interferometer which measures the information about the displacement of an object (2) which is placed in a light path from a light source (1) which emits a laser beam, incoherent light beam, or the like by using the interference of the light, a phase modulator (3) is provided in the light path to detect the signal light beam and reference light beam. The instability of the light is detected by a photodetector (6) and the detected instability is converted to a voltage or a current through a differential amplifier (7) and the voltage or the current is applied to the phase modulator (3) to stabilize the signal light beam and reference light beam.</p> |
