| 摘要 |
PURPOSE: To generate at least two electric signals, which have a phase difference other than 180 deg., as the output with a simple means by providing an attenuation element used for generation of at least two electric signals, whose positions are shifted from each other by an angle other than 180 deg., in the output of a waveguide coupler. CONSTITUTION: At least one attenuation element T is provided which reduces the intensity of light for the purpose of generating at least two electric signals S1a and S1b , whose positions are shifted from each other by an angle other than 180 deg., in outputs A1a and A1b of a waveguide coupler K1 . Because of the existence of at least one attenuation element T or at least one phase shifting element, two electric signals S1a and S1b whose phases are shifted from each other by an angle other than 180 deg. are generated in both outputs A1a and A1b of at least one 2×2 coupler K1 with a simple method by detectors D1a and D1b . This 2×2 coupler K1 can be used in a position measuring instrument requiring discrimination of the measurement direction. |
