| 摘要 |
PURPOSE:To make a production easy and to obtain a high accuracy by arringing in two pairs on the same circumference of a light detecting plate the light detectors adjoining at an integer times of center angles of more than two of the center angle, which is between those adjoining the light penetrating part provided on a rotary plate. CONSTITUTION:Numerous light penetrating parts 4 are provided on a rotary plate 3 so as to adjoining at an equal center angle theta. Two pairs of light detecting parts 51 and 52 of a light detecting plate 6 are either projecting each other from the connecting conductors 53, 54 of both sides on the same circumference of beneath the light penetrating part 4. The respective detecting part 51, 52 is adjoined at the central angl of 3theta. The angle alpha made by the adjoining detecting parts 51 and 52 each other makes the angle of not integer times of theta/2, for instance, the angle adding 1/4theta to 3theta or subtracting, namely 13/4theta or 11/4theta. Consequently the adjoining different detectors 51, 52 can take the gap of the center angle wider and the generation of defects in a photoetching stage can be reduced remarkably. |
