| 摘要 |
<p>PURPOSE:To detect an angle with high precision without any error against the drift of a photodiode and sensitivity variation by providing a light emission source which generates linear polarized light, a driving circuit which turns on and off repeatedly, and a phase detecting circuit. CONSTITUTION:A magnetic field measuring instrument is equipped with the light emission source 1 which generates a 0 deg., a 60 deg., and a 120 deg. linear polarized wave, the driving circuit 11 which excites the light emission source 1 so that signals of three phases have a difference of a 120 deg. electric angle and turn on and off at intervals of two periods, and the phase detecting circuit which makes respective linear polarized waves incident on photoelectric converters 4a and 4b through a Faraday rotator 2 and an analyzer 7 and detects phases of phase modulated waves obtained from output signals of the photoelectric converters 4a and 4b. Then, the phase detector 10 compares phase modulated waveforms with the reference phase of a driving circuit 11 to obtain an output signal proportional to an angle theta. Consequently, the angle theta is detected with high precision without any error against the drift of the photodiode and sensitivity variation.</p> |
