| 摘要 |
PURPOSE:To detect the displacement with high precision by providing a photodetecting element outputting a background light signal and correcting a position detecting signal when an object is irradiated with laser light for measurement and scattered light is made incident on a position detecting element and the displacement of a datum plane of the object is detected. CONSTITUTION:The opposite side of a working head is irradiated with the laser light of laser light sources A4, B4 for measurement and the respective scattered light are photodetected by the position detecting elements A7, B7. Then, the lights photodetected by the elements A7, B7 are converted into the voltages to detect the displacement of the datum plane of the object. Here, when the light from the laser source A4 irradiates the object and photodetected by the position detecting element A7, the background light is mixed. Meantime, the light from the laser light source B4 is stopped and the spot light only in the shade of the working head is photodetected by the element B7 to detect the background light only. Then, a detected value of the position detecting elements B7 is calculated backward from a detected value of the position detecting element 7 to eliminate the background light signal from the position detecting signal. Accordingly, since the background light signal is eliminated from a mixed signal of the position detecting signal, the displacement of the object can be detected with high precision. |
