| 摘要 |
PURPOSE:To make it possible to detect and evaluate minute defects in a recording medium and their growing steps and to make it possible to separate the polarizing light type defect and the non-polarizing light type defect and to detect and analyze the defects, by providing a condensing optical system, optical sensors, an operating circuit and the like. CONSTITUTION:When a recording medium D is relatively moved with respect to a condensing optical system 2, reflected light from the recording medium D is divided into two polarized light components having the different polarization angles through the optical system 2. The light beams are inputted into optical sensors 6 and 7 and transduced into electric signals. The electric signals are operated in an operating circuit 8. The voltages, which depend on the polarization angle and the intensity of the reflected light, are selectively outputted. Low frequency noises are removed from the voltages in a high frequency filter 9. The voltages, which exceed a reference voltage, are outputted from a differential amplifier 10 and counted 11 based on the lengths of the pulses. In this way, the minute defects and the growing steps of the medium D can be detected and evaluated. The deflecting light type and non-light type defects can be separately detected and analyzed. |
