Abstract: An optical scanner that has a simple construction and which yet exhibits satisfactory imaging performance under varying temperature conditions. Of the two orthogonal scanning cross sections of scanning optics (i.e., the main and sub-scanning cross sections), the one that involves the greater movement of the image plane due to the temperature-dependent changes in optical characteristics (e.g. the variation in the operating wavelength of a light source, the index variation of a lens material and the thermal expansion of a lens itself) is adapted to be the same as the other cross section that involves the greater movement of the image plane due to the change in the distance from the light source to a collimator lens.

Abstract: An optical scanner for use in laser beam printers and the like which is particularly satisfactory in imaging characteristics. A light beam from a semiconductor laser passes through a collimator lens, an aperture diaphragm and a cylindrical lens. The beam is then deflected by a rotating lens mirror and subjected to the focusing action of an imaging lens so that it is focused to form a beam spot, which scans over a scan surface as the beam is deflected. The imaging lens has aspheric surfaces in the main-scanning cross section and is designed so that the rate of change in its curvature and other relevant parameters satisfy a predetermined equation so as to lie within a predetermined range.

Abstract: A charger capable of reliably and uniformly maintaining a discharging gap formed in the vicinity of a contact portion between a charging member and a photosensitive member. A charging member 101 is arranged by supporting and fixing both ends of a flexible film 102 by means of support members 103 to 105. The film 102 forms a flexible portion oriented downwardly from fixed ends S1, S2. The film 102 is brought into contact with the member 110 to be charged in a state in which an unsupported side of the film 102 is oriented toward the downstream side in the rotating direction of the member 110 to be charged. Then, the film 102 is brought into contact with the member 110 to be charged in a contact area N, and the radius of curvature of the film 102 in a zone P2 located downstream of that zone N in the rotating direction of the member 110 to be charged becomes smaller than the radius of curvature of the film 102 in an upstream zone P1.