Temperature compensation for a microoptical displacement sensor using an integrated thermal sensor

We developed a microoptical displacement sensor on which a thermal sensor was integrated. The sensor was 3 × 3 mm² in size and 0.7 mm thick including the optical power source and thermal sensor. The optical displacement sensor can measure the linear displacement at high resolution without contacting the subject to be measured. We also investigated the dependence of the sensor on thermal change, and we tried to compensate for the dependence when using the thermal sensor by applying the correction functions A(T), B(T), and C(T). These correction functions, which can be easily calibrated, corresponded to the thermal correction of the irradiation angle of the optical power source, the output power of the optical power source, and the sensitivity of photodiodes (PDs), respectively. From the experimental results, the dependence of the optical displacement sensor was reduced from 2.27 to 0.13 μm/°C. This optical displacement sensor is expected to be used as a position sensor for piezoelectric actuators that also show strong thermal dependence.