| 摘要 |
PURPOSE:To correct illuminance in contraction mode and secular variations in the ouput light intensity of a light sorce for exposure by providing a slit for correcting illuminance distribution rotatably and by specifying the shape of a light-shielding plate so that it has prescribed area according to the turning angle of the slit. CONSTITUTION:Between a lens 1 and a photoreceptor surface 2 as an imaging surface, a light-shielding plate 4, a slit 5 for correcting illuminance distribution, and a slit 3 for controlling exposure time are arranged successively at intervals and according to the rotation of the slit 5, the shape of the light-shielding plate 4 wherein required area is obtained in contraction mode is found, thereby obtaining two kinds of light-shielding plates 4 and 4' in nonmagnification and contraction modes. The slit 5, on the other hand, turns to vary the apparent slit width, and then the effective are of the lens also varies, so the shape of the light-shielding plate is so determined that when the slit 5 turns, the shielding plate has area corresponding to the apparent slit width variations. |
