| 摘要 |
PURPOSE:To prevent the generation of beat, by changing a modulating frequency in response to the drift of a fundamental chopper frequency. CONSTITUTION:A control means 51 is arranged as shown by the Figure. Control signals are outputted from terminals 31 and 30, based on a reference signal from a chopper 3 to a terminal 32 through a path (c). The sine wave appeared at the terminal 30 is sent to the direction of an arrow (d) and controls the frequency and phase of a laser driving power source 7. The pulses outputted from the terminal 31 become a reference signal for a lock in amplifier LA2 and controls the phase detector in the amplifier LA2. In this constitution, even though harmonic waves 2fch-7fch are drifted, a modulating wave fmod is changed following said drift. Therefore the beat is not generated. |
