| 摘要 |
PURPOSE:To obtain a signal having a certain amplitude invariably and being free from central drift even when an output signal is varied, by using signals obtained by applying arithmetic processings using specific formulas to signals of phase A taken out of an encoder and phases A' and B which are inverted thereto in phase by 180 deg. and different in phase by 90 deg. therefrom. CONSTITUTION:A light from a light-emitting element 6 is inputted to forwarding fibers 4 of phases A, A' and B and reaches a reflection-type encoder sensor unit 1 through an optical fiber cable 2. The light reflected with the rotation of a rotary slit plate of the unit is transmitted through backing fibers and converted into output voltages VA, VA' and VB by photodetecting circuits 9a, 9a' and 9b provided with photodetectors 7a, 7a' and 7b corresponding to the phases A, A' and B respectively. By using for these voltages the signals computed by an arithmetic processing circuit 10 so that the formula I using mark theta as a rotational angle of the rotary plate be established, a signal having a fixed peak value and being free from central drift can be obtained. |
