| 摘要 |
PURPOSE:To eliminate the phase error of a segment pattern by providing a means of adjusting an interval between a light source and a condenser. CONSTITUTION:A movable grating 1 having grating pitch P moves as a moving body moves. A fixed grating 2 has the same pitch as the movable grating 1 and consists of two left and right segments 21 and 22 at a nearly 1/4 period, i.e. P/4. A light source device 3 is provided with an interval adjusting means for adjusting an interval l between a light source 4 and a condenser lens 5, and the position of an image of the movable grating 1 formed on the fixed grating 2 is displaced to left and right to eliminate a phase error included in respective segment patterns between the left and right segments 21 and 22, and 23 and 24. |
