| 摘要 |
PROBLEM TO BE SOLVED: To suppress an error in positional detection and detect a position accurately. SOLUTION: When the direction of X-axis is assumed to be the direction of positional detection and the direction of Y-axis and the longitudinal direction of a slit are deviated from their parallel condition due to the inclination of the slit, an LED 19 and the slit move in the direction of Y-axis and in the irradiation light from the LED 19 through a silt, deviation of the center of gravity (position detection error) in the direction of X-axis of a PSD(position sensitive light detector) 16 for a light receive face 20 occurs. But, a correction value which corresponds to a position detection error which corresponds to Y-axis light receive position is added to an X-axis light receive position detected by a control part 22 to detect a travel position on the X-axis so that the accurate position detection becomes possible by suppressing the position detection error. |
