| 摘要 |
PURPOSE:To perform measurement without an error by comparing the difference of measured value obtained when the size of a sport is changed by changing a distance between a light source and a light projecting lens or the irradiation angle of a light beam with a reference value, detecting the missing of the spot even when the missing occurs in the spot and correcting an obtained result. CONSTITUTION:A projected light beam L emitted from a light emitting element LED passes the light projecting lens 10 and is reflected on an object M, then a reflected light beam S is made incident on a photodetector PSD by a light receiving lens. In order to change the diameter of the spot 50 generated by irradiating the object M with the projected light beam L, a piezo-electric element 6 for changing the distance between the lens 10 and the LED is attached to the lens 10. The lens 10 is laterally moved by the piezo-electric element 6 and the spot 50 on the object M is made 51, for instance, or large 52. By changing the irradiation angle of the beam L, the size of the spot 50 can be varied. In the case that the difference of output obtained when the size of the spot is changed exceeds the range of set value, the obtained result is corrected by judging there is a large possibility that an erroneous distance is obtained or a warning is given to accelerate to perform measurement again. |
