| 摘要 |
An optical scanner including a semiconductor laser device, aperture, collimator, cylindrical lens, polygonal mirror and one f theta lens element molded from plastics. The first surface of the f theta lens in a deflecting plane (or the plane formed by the principal rays of light as deflected by the polygonal mirror) is aspheric whereas the second lens surface is toric. When taken in the deflecting plane, the first lens surface has a positive value of the near-axis radius of curvature and, hence, it is convex toward the polygonal mirror. Taken in a plane crossing the deflecting plane at right angles, the first lens surface forms an arc of a circle having a negative value of the radius of curvature and, hence, it is concave toward the polygonal mirror. When taken in the deflecting plane, the second lens surface forms an arc of a circle having a negative value of the radius of curvature and, hence, it is convex toward the scanning surface.
|
