| 摘要 |
PURPOSE:To improve the quality of an image by eliminating variation in the diameter of a beam spot due to the rotation of an elliptic beam on a scanning line and forming a uniform beam spot on a scanned surface. CONSTITUTION:Not the whole of a pyramidal mirror 24 and a slanting surface 41, but a nearly elliptic area formed to size A in a rotary circumferential direction as a main scanning direction and to size B in a subscanning direction intersecting orthogonally with the main scanning direction nearly axially symmetrically about the rotary shaft of the pyramidal mirror in the slanting surface 41 is made into a reflecting surface 42. Then the reflecting surface 42 is so sized that it is covered with a beam incident on the reflecting surface 42 at all times at least within a range wherein a deflector 23 rotates by an effective view angle. The relation between the angles of incidence and reflection of the deflector 23 to the reflecting surface 42 is the same as before and the elliptic beam which is deflected never varies in spot diameter on the scanned surface in the main scanning direction and subscanning direction. Consequently, the picture quality is improved. |
