| 摘要 |
PROBLEM TO BE SOLVED: To enable compactness and high resolution by enabling the acquisition of output signals with a phase difference of 180 deg. at all times. SOLUTION: A movable plate is provided between light-emitting and light- receiving elements 22 and 23. Light from the light emitting element transmitted through the slits of the movable plate or reflected at the reflecting fringes of the movable plate is detected by the two light-receiving elements 22 and 23 arranged so as to have a phase difference of 180 deg. to the slits or reflecting fringes. Then a first detection current flowing through the one light-receiving element 22 is converted from current into voltage and amplified by a first amplifier 35 to be a first output voltage, and a second detection current flowing through the other light receiving element 23 is converted from current into voltage and amplified by a second amplifier 36 to be a second output voltage. The first and second output voltages are inputted to a comparator 43 to obtain a rectangular signal. Then each reference-side voltage of the first and second amplifiers 35 and 36 is a voltage obtained from a synthetic voltage based on a synthetic signal synthesized from signals from the two light-receiving elements 22 and 23.
|
