Abstract: An optical member having a toric functional surface has a marking which is made by a configuration of a mold used to form the optical member. The marking is formed in the optical member outside an effective area of the functional surface of the optical member. In one embodiment, the optical member is an optical member for a scanning optical system.

Abstract: The light beam scanning device has a casing injection molded from magnesium or magnesium alloy as the material. A polygon mirror and a motor are sealed in the inside of the casing and a cover covering the latter. Since the thickness of the magnesium or magnesium alloy material can be reduced, heat generated from a motor is dissipated satisfactorily. Heat dissipating fins are formed to the casing to promote heat dissipation and enhance the strength of the casing.

Abstract: The light beam scanning device has a casing injection molded from magnesium or magnesium alloy as the material. A polygon mirror and a motor are sealed in the inside of the casing and a cover covering the latter. Since the thickness of the magnesium or magnesium alloy material can be reduced, heat generated from a motor is dissipated satisfactorily. Heat dissipating fins are formed to the casing to promote heat dissipation and enhance the strength of the casing.

Abstract: A scanning optical apparatus constitutes a light source which emits a ray in a wavelength range of 460 to 650 nm, a first lens unit for forming a luminous flux using the ray and having at least one or more positive lens element, a scanner for scanning the luminous flux, a second lens unit for forming an image on a scanned medium using the luminous flux and a holding structure connected the light source to the first lens unit via at least two support members having mutually different linear expansion coefficients. In scanning optical apparatus, the movement of the image forming point on the scanned medium caused by change in the oscillation wavelength of the light source is compensated by the thermal expansion of the support members.

Abstract: The light beam scanning device has a casing injection molded from magnesium or magnesium alloy as the material. A polygon mirror and a motor are sealed in the inside of the casing and a cover covering the latter. Since the thickness of the magnesium or magnesium alloy material can be reduced, heat generated from a motor is dissipated satisfactorily. Heat dissipating fins are formed to the casing to promote heat dissipation and enhance the strength of the casing.

Abstract: A scanning apparatus has a luminous flux deflector and a single f.theta. lens. The deflector deflects a convergent luminous flux on a scanned surface at a uniform angular velocity. The f.theta. lens is arranged between the deflector and the scanned surface. The f.theta. lens is bi-convex in a main scanning direction and is made of a material having a refractive index of at most 1.6. One surface of the f.theta. lens in a main scanning direction is so curved that a radius of curvature in the main scanning direction A decreases as an angle of view in the main scanning direction increases.

Abstract: A scanning apparatus has a luminous flux deflector and a single f.theta. lens. The deflector deflects a convergent luminous flux on a scanned surface at a uniform angular velocity. The f.theta. lens is arranged between the deflector and the scanned surface. The f.theta. lens is bi-convex in a main scanning direction and is made of a material having a refractive index of at most 1.6. One surface of the f.theta. lens in a main scanning direction is so curved that a radius of curvature in the main scanning direction decreases as an angle of view in the main scanning direction increases.

Abstract: A scanning apparatus has a luminous flux deflector and a single f.theta. lens. The deflector deflects a convergent luminous flux on a scanned surface at a uniform angular velocity. The f.theta. lens is arranged between the deflector and the scanned surface. The f.theta. lens is bi-convex in a main scanning direction and is made of a material having a refractive index of at most 1.6. One surface of the f.theta. lens in a main scanning direction is so curved that a radius of curvature in the main scanning direction decreases as an angle of view in the main scanning direction increases.

Abstract: A light beam scanning optical apparatus which deflects a light beam emitted from a light source with a polygonal mirror and scans the light beam on a photosensitive member through an f.theta. optical system. Suppose the distance between a rotation axis of the polygonal mirror and each reflecting facet in a case wherein the reflecting facets are flat to be A. If a convergent light beam is incident to the polygonal mirror, and if the reflecting facets are concave, the distance between the rotation axis and the facets is adjusted to be larger than A. If the reflecting facets are convex, the distance is adjusted to be smaller than A. Also, if a divergent light beam is incident, and if the reflecting facets are concave, the distance between is adjusted to be smaller than A. If the reflecting facets are convex, the distance is adjusted to be larger than A.