PURPOSE: To obtain a highly accurate laser length-measuring instrument which is free from returning light and can be miniaturized by using a semiconductor laser which outputs laser beams from both sides.
CONSTITUTION: The output laser beam of a semiconductor laser 1a from one side is emitted to the outside of a semiconductor substrate 50 through an optical waveguide 6a and entered into another optical waveguide 6b through a lens 2a, prism 7, and lens 2b. The laser beam entered into the waveguide 6b is entered into photodetectors 5a and 5b. The output laser light of the laser 1a from the other side is entered into the photodetectors 5a and 5b through the waveguide 6b. Since the two laser beams emitted from the laser 1a pass trough difference optical paths before they reach the photodetectors 5a and 5b, they interfere with each other. Since the prism 7 is fitted to an object to be measured, an output signal is obtained on the basis of the interference due to the position of the prism 7. Since the output laser beams from both sides of the laser 1a are used without using any light branching means, in addition, no returning light exists and highly accurate measurement can be performed.
HOSOMATSU HARUO
ISOZAKI KATSUMI
