| 摘要 |
<p>PURPOSE:To obtain an absolute measurement output by making two light beams which differ in wavelength incident n an interference optical system one over the other at a length measurement part, and separating and receiving return light beams by different measuring means. CONSTITUTION:The light beams with wavelengths lambda1 and lambda2 emitted by laser light sources LZ11 and LZ12 are superposed one over the other through a polarization beam splitter BS1 and a lambda/2 plate P1 so that their planes of polarization cross each other at right angles. The superposed light is made incident on a cube corner CC1 adn an object OBJ of measurement through a half-mirror HMR1. The obtained interference light is split by a polarization beam splitter BS2 according to the direction of its plane of polarization. Namely, the lights with the wavelengths lambda1 and lambda2 enter a phase detecting circuit PD1 through photodetectors D1 and D2 and the circuit outputs a signal corresponding to the difference in phase delay quantity between those light beams. This measurement data is utilized to calculate distance. Combinations of wavelengths are changed to narrow down the measurement range, so that an absolute measurement output with high accuracy is obtained.</p> |
