| 摘要 |
PURPOSE:To eliminate the adjustment of the mounting position, by providing first and second slot trains along the circumference of a concentric circle of a rotary disc in such a manner as to be the same in the cycle but difference in the phase to arrange two photosensors on the straight line. CONSTITUTION:Slits S1 are formed circumferentially at a fixed interval on the circumference of a rotary disc 1 to make a first slit train while slits S2 are cut circumferentially along the circumference of a concentric circle inside it at such a position as to be the same in the cycle as the first slit train but shifted by 90 deg. in the phase to make a second slit train. First and second photosensors 2 and 3 are arranged at respective positions where the first and second slit trains pass on the radius of the disc 1. A digital circuit 4 is made up of gates 5-9, NAND gates 10-13, OR circuits 14 and 15 and the like and outputs a high level or a low level according to the phase difference in the output between sensors 2 and 3 to indicate the direction of rotation of the rotary disc 1. |
