| 摘要 |
<p>PURPOSE:To obtain an inexpensive detector with high measurement precision by dividing object light and reference light into mutually pi/2 out-of-phase polarized components and causing each polarized component to interfere. CONSTITUTION:Light from a laser light source 40 is transmitted through beam splitters 41 and 42 and reflected by a mirror 43 fitted to the surface of a body to be measured, and further deflected by the splitter 42 to obtain the object light. Light reflected by the splitter 41, on the other hand, is deflected by a fixed mirror 44 and then passed through a quarter-wavelength plate 45 to obtain the reference light. This object light does not change in polarization state, but varies with optical path length according to the displacement of the object. The reference light is polarized circularly by the quarter-wavelength plate 45 into pi/2 out-of-phase components. Then, the object light and reference light are each split into two by a beam splitter 46, and respective polarized components are separated by two polarizers 47 and 48 which have planes of polarization at right angles to cause each component to interfere on two detectors 49 and 50. For the purpose, output currents of the detectors 49 and 50 are processed electrically to obtain displacement.</p> |
