半導体レーザの自己結合効果による微小振動センサの自動調整化

Abstract

With the advance in technology, it becomes to necessary to detect a small vibration that has been neglected in the manufacturing process before. A laser interferometer is used as a small vibration sensor. But there are some disadvantages, for example, weakness for external vibration, difficulty for optical alignment, etc. These disadvantages are improved making use of self-coupling effect of semiconductor laser, because this sensor is composed of only a laser diode and a lens. The laser light is irradiated to a target with the lens, and the scattered light is detected by photodiode. When a small vibration less than half-wavelength of laser is measured, it is needed the reference signal. The reference signal is generated by moving the sensor at high speed. The vibration amplitude is detected from the ratio of the output signal to the reference one. Moreover, the sensitivity of the sensor is different from the distance between LD and target. Therefore, it is necessary to adjust sensitivity. Up to now, it has been adjusted by the method of the manual operation. The sensitivity adjustment is automated by the microcomputer. As a result, the measurement accuracy was able to be improved.