JPS6484103A - Laser interference device - Google Patents

Abstract

PURPOSE:To stabilize the operation of a laser light source and to improve its measurement accuracy by attenuating light which returns to a laser light source to the product of the quenching ratios of both polarization beam splitters with only light which is transmitted through both 2nd and 1st polarization beam splitters. CONSTITUTION:A laser light source 2 outputs 1st and 2nd linear polarized light beams 41v and 42h which cross each other at right angles and differ in frequency and those are split by a 1st polarization beam splitter 61. Then the polarized light 41v which is transmitted through the splitter 61 is passed through a 2nd polarization beam splitter 62 and circular polarized light 41c which is converted by a phase element 8 is reflected on the same optical path with the incident light by a 1st reflector 10 fitted on a moving body. This is reconverted by the phase element 8 into linear polarized light 41h which has its polarization direction 90 deg. different from that of the polarized light 41v and the linear polarized light is reflected by the splitter 62 and entered into a beam matching device 20. The polarized light 42h which is split by the splitter 61, on the other hand, is reflected by a 2nd reflector 22 and entered into the beam matching device 20, and a detector 14 detects the composite light 44 of the polarized light beams 42h and 41h. At this time, the return light to the light source 2 is small enough to ignore because of the quenching ratio of the splitters 62 and 61.