| 摘要 |
PURPOSE:To make it posible to perform simple adjustment and to reduce errors, by providing a reference scale which receives parallel light beams from one light source, a scale having 90 deg. phase difference, and windows, at lower halves in which scales are not graduated. CONSTITUTION:Four windows 5, 6, 7, and 8 are provided in a sliding part 2, which is moved in the logitudinal direction with respect to a main scale 1. An index scale (0) for a reference signal is attached to the window 5. A scale, which outputs a signal that is 90 deg. out of phase, is attached to the window 6. The transparent windows 7 and 8 are provided at the lower sides of the windows 5 and 6. The windows 5 and 7 and the windows 6 and 8 are made to face the upper and lower halves of the graduation of the main scale, respectively. Parallel light beams from one light source are applied to the four windows through a lens 4. The tansmitted light beams are received by y1, y2, y3, and y4 of a light receiving element 9, and the output is obtained. Based on the detected signals, (y1-y3) and (y2-y4) are made to be a sin signal and a cos signal. |
