| 摘要 |
An optical instrument which has a parallel scanning beam generator including a polygonal rotary mirror adpated to reflect an incident beam from a beam generator and obtain a rotary scanning beam, and a f theta lens adapted to turn the rotary scanning beam into a parallel scanning beam, and a light-receiving element for detecting the brightness and darkness of the parallel scanning beam passed through an object to be measured, and which is adapted to detect the time length of a dark or bright portion occurring when a part of the parallel scanning beam is intercepted by the object to be measured, which is disposed between the parallel scanning beam generator and the light-receiving element, and thereby determine the measurement of the object with respect to the scanning direction, a variable lens system which has a focus on an optical path between the beam generator and polygonal rotary mirror being provided on the same optical path. |
