| 摘要 |
PURPOSE:To enable the measurement of distance to an object to be measured without being affected by any frequency shift, by providing a measuring optical system for obtaining a measuring beat wave with a reference optical system for obtaining a reference beat wave. CONSTITUTION:A measuring optical system 15 for obtaining a measuring beat wave is provided with a reference optical system 16. A laser beam to be introduced into the reference optical system 16 shall be a part of a laser beam introduced from a semiconductor laser 1 with a beam splitter 17 provided between a convex lens 3 and a beam splitter 4 in the measuring optical system 15. Furthermore, a part of the laser beam is reflected with a beam splitter 18 to irradiate a first reference reflector 19 such as mirror or prism separated by a specified distance while the rest thereof is transmitted through the beam splitter 18 to irradiate a second reference reflector 20 such as mirror or prism separated by a specified distance. The distance from the first reference reflector 19 and the second reference reflector 20 is differentiated with respect to the beam splitter 18.
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