Optical heterodyne interference measurement device and optical heterodyne interference measurement method

An optical heterodyne interference measurement apparatus comprising:

• a laser light source configured to generate and output a first light beam and a second light beam having optical frequencies different from each other by a heterodyne frequency and polarizations orthogonal to each other based on light reflected by or transmitted through a measurement object;
• a first photodetector configured to detect a temporal change of an intensity generated by heterodyne interference between the first light beam and the second light beam, and output a first detection signal;
• and
• a computer configured to set, when Op is set to any peak frequency being temporally constant in a frequency spectrum of intensity noise included in the first light beam or the second light beam output from the laser light source, the heterodyne frequency being a difference between the optical frequencies of the first light beam and the second light beam output from the laser light source to a value of a rational multiple of the peak frequency ωp, and configured to acquire information on the measurement object based on a phase of a component temporally changing sinusoidally at the heterodyne frequency in the first detection signal.

An optical heterodyne interference measurement method comprising:

• generating and outputting a first light beam and a second light beam having optical frequencies different from each other by a heterodyne frequency and polarizations orthogonal to each other;
• detecting a temporal change of an intensity generated by heterodyne interference between the first light beam and the second light beam by a first photodetector after any one or both of the first light beam and the second light beam are reflected by or transmitted through a measurement object, and outputting a first detection signal;
• setting, when ωp is set to any peak frequency being temporally constant in a frequency spectrum of intensity noise included in the first light beam or the second light beam output in the beam generation, the heterodyne frequency being a difference between the optical frequencies of the first light beam and the second light beam output in the beam generation to a value of a rational multiple of the peak frequency ωp;
• and
• acquiring information on the measurement object based on a phase of a component temporally changing sinusoidally at the heterodyne frequency in the first detection signal.

An optical heterodyne interference measurement method comprising:

• generating and outputting a first light beam and a second light beam having optical frequencies different from each other by a heterodyne frequency and polarizations orthogonal to each other based on light reflected by or transmitted through a measurement object;
• detecting a temporal change of an intensity generated by heterodyne interference between the first light beam and the second light beam by a first photodetector, and outputting a first detection signal;
• setting, when ωp is set to any peak frequency being temporally constant in a frequency spectrum of intensity noise included in the first light beam or the second light beam output in the beam generation, the heterodyne frequency being a difference between the optical frequencies of the first light beam and the second light beam output in the beam generation to a value of a rational multiple of the peak frequency ωp, and
• acquiring information on the measurement object based on a phase of a component temporally changing sinusoidally at the heterodyne frequency in the first detection signal.