An apparatus and a method which enable, in optical
angle modulation, measurement of
laser light, to measure by a delayed self-
heterodyne method, accurate measurement of a temporal waveform of optical
angle modulation, without any influence by
light intensity modulation, without necessity of for calibration, and without necessity for stabilizing an interferometer. In an optical
angle modulation measurement apparatus using a delayed self-
heterodyne method, a
heterodyne interferometer that is fed with
laser light to be measured; a
photodetector that receives output light of the
heterodyne interferometer and performs
heterodyne detection of the output light to output a beat
signal; using a phase demodulator that is configured to demodulate a phase of a beat
signal; and a temporal waveform analyzer that is configured to obtain a temporal waveform of optical angle modulation, from the phase of the beat
signal. In an optical angle modulation measurement method by a delayed self-heterodyne method,
laser light to be measured, which is optical-angle modulated is input to a
heterodyne interferometer,
heterodyne detection of the output light is performed by a
photodetector, and a temporal waveform of optical angle modulation is obtained by demodulating a phase of the beat signal.