| 摘要 |
<p>PURPOSE:To set an operation point freely, and to prevent a photodetector from being saturated and to detect the voltage of a body to be measured with high accuracy by outputting a light intensity signal corresponding to a voltage to be detected by an optical modulating means and chopping the light intensity signal before it is inputted to a sampling type fast photodetecting means. CONSTITUTION:Light from a DC light source 70 consisting of an He-Ne laser, a semiconductor laser, etc., is inputted to the optical modulator 4 which chops the light at a prescribed chopping frequency and its output is sent to the optical modulator 40 which modulates the input with the voltage from the body 53 and outputs a corresponding light intensity signal; and its output is inputted to the sampling type fast photodetector 2. In this constitution, the optical modulator 4 uses an acoustooptic modulator or electrooptic modulator and consists of a polarizer 55, a Pockel's cell 54, a phase compensator 56, and an analyzer 57. Consequently, the operation point can be set freely and even when the quantity of light is large, the fast photodetector 2 can be operated normally.</p> |
