| 摘要 |
PURPOSE:To generate a stable signal through small-sized constitution by obtaining two out-of-phase position signals from three photodetectors arranged so as to obtain the out-of-phase signals. CONSTITUTION:The photodetectors (a), (b), and (c) are arranged at intervals a quarter as large as one cycle of slits. Signals A, B, and C obtained by the detectors (a), (b), and (c) shift in phase from one another by a quarter cycle; and a subtractor 14 obtain a signal A-B and a subtractor 15 obtain a signal C-B. Further, an inversion type adder 16 obtains a signal A+C, with which the brightness of an LED is held constant through an LED driving circuit 17. |
