JPH05240884

PURPOSE:To simplify the constitution, make control easy and improve the S/N ratio by providing an electric field detection probe with a modulation means for the state of polarized wave. CONSTITUTION:The output light pulse of a light source 1 goes in an electrode 18 and an electric field detection probe 7 by way of mirrors 2, 3, a light polarizer 4, a wave length plate 5 and a mirror 6. By impressing the output signal of an oscillator 12 to the electrode 18, the state of polarized wave of the incidence light 100 is modulated. On the other hand, a drive circuit 14 outputs the drive signal of a measured circuit 8, supplies the light source 1 with a trigger signal and make the light pulse and the drive signal synchronize. The, incidence light 100 changes in conditions of the plane of polarization due to the electrooptic effect of the probe 7 and is reflected. The reflected light goes into the polarizer 4 by way of the mirror 6 and the wave length plate 5 and only light signal having a specific polarized wave is separated to send in a light detector. Its output is detected in a synchronous detection circuit 10 by referring the output of the oscillator 12 and indicated on a display 11.