| 摘要 |
<p>PURPOSE:To attain an accurate voltage detection without using an electric chopper by providing an electric force line interrupting means intermitting the electric force line of an electric signal under measurement to the tip of an optical probe and a synchronous amplifier amplifying the output of a photodetector synchronizing thereto. CONSTITUTION:An oscillator 22, by which an integrated circuit 20 oscillates at high speed in the direction of optical axis for an light beam against the optical probe 12, is provided. The oscillator 22 is oscillated by a driver 24 to make the circuit 20 to oscillate against a dielectric multilayer film mirror 12A at the tip of optical probe 12. A lock-in amplifier 28 is synchronized to this oscillation to amplify a signal from the light detector 26. When the oscillated circuit 20 is separated from the optical prove 12, it is not exerted by the electric force line but only exerted at the time of approaching; therefore, a refractive index of the optical probe 12 is varied with synchronizing to the oscillation, and the incident light beam is some time modulated and some time unmodulated in synchronizing with the oscillation accordingly. By this procedure, a distortion of signal waveform caused by ON/OFF of the electric signal under measurement is prevented, and the accurate voltage detection can be performed.</p> |
