| 摘要 |
PURPOSE:To obtain a high-resolution and inexpensive optical scanner by constituting a scanning lens of two lenses, making a lens on the side of a light deflecting device an aspherical lens and a lens on the side of a surface to be scanned a cylindrical lens. CONSTITUTION:This scanner is provided with a rotary polygon mirror 1, the surface of a photoreceptive drum 6, the aspherical lens 44, and the cylindrical lens 45, and a beam 94 at ordinary temperature, a beam 95 at high temperature, an image surface 64 at the ordinary temperature, and an image surface 65 at the high temperature are shown in figure. In such a case, since the radius of curvature of the lens 44 is continuously changed at a deflecting position so that the curvature of field may be zero at the ordinary temperature, the image surface 66 is aligned with the surface of the photoreceptive drum 6 when an error is not found in the radius of curvature. Meanwhile, since the refractive index of plastic material is lowered at the high temperature and the power of the lenses 44 and 45 is reduced, the image surface 65 is separated from the surface of the photoreceptive drum but less than usual. Thus, the high-resolution optical scanner is obtained. |
