| 摘要 |
PURPOSE:To measure displacements without receiving the flutuations in the power of laser light by controlling a common voltage with the total output current quantity of an optical axis sensor having photodetectors connected in parallel to the common voltage. CONSTITUTION:The voltage generated in a resistor RO by the total current IT of the currents Ia-Id flowing in photodiodes A-D when an optical axis sensor receives laser beams is superposed on the negative voltage determined by a reference voltage power source 3 and the superposed voltage is inputted to a differential amplifier 4 by which the total current IT is so controlled as to be kept constant despite the fluctuation in the power of the laser light. Therefore the potentials Ea-Ed at points (a)-(d) are determined only by the displacements of optical axes and the optical axis sensor without receiving the influece of the fluctuations in the laser power. The potentials Ea-Ed are arithmetically processed by operational amplifiers 5-10, whereby the displacements of the optical axis sensor with respect to the optical axes are detected. |
