Abstract: A laser beam optical scanning system which has a laser source unit for emitting a laser beam which is a parallel pencil of rays, a first imaging system for imaging the laser beam emitted from the laser source unit on a reflective facet of a deflector, and a second imaging system for imaging the laser beam deflected by the deflector on a photosensitive drum. At least one of the first and the second imaging systems has a resin lens. The resin lens changes its power according to temperature so as to offset a change in light converging performance of the laser source unit.

Abstract: A toroidal lens and two pieces of spherical mirrors cooperatively function to have a uniform velocity of a light beam over a range from the center to both edges of a scanning area when the light beam deflected at an equiangular velocity by a rotative deflection device is directed toward a light collecting surface. The toroidal lens further maintains a conjugate relation of each reflective surface of the rotative deflection device and the light collecting surface by which an error in the inclination of image on each reflective surface is rectified, and at the same time, the direction of radiation of the light beam is regulated so as to make the curvature of the field smaller.

Abstract: In a light beam scanning optical system, a toroidal lens and a spherical mirror or a cylindrical mirror function in cooperation to rectify the scanning speed of a light beam deflected at an equiangular velocity by a rotative deflection device to be uniform over the range from the center to both edges of scanning area in the main scanning direction. The toroidal lens is further arranged to maintain each reflective facet of the rotative deflection device and the light collecting surface in the conjugate relation, thereby rectifying an error of image inclination of each reflective facet and at the same time regulating the direction of emission of the light beam so as to lessen the curvature of the field.

Abstract: A deflection device and a spherical mirror for use in a light beam scanning optical system which fulfills either one of the following equations,0.15< (d/.vertline.R.sub.M .vertline.)<0.45 (1)wherein d is a distance from a point of reflection of luminous flux directed toward the center of a scanning direction by a deflection device to the vertex of a spherical mirror, and R.sub.M is a radius of curvature or, ##EQU1## wherein s is a distance from a point of reflection of luminous flux directed toward the center of scanning direction by a deflection device to light collecting point after reflection of deflection device. When the spherical mirror fulfills the equation (1), it collects a parallel luminous flux deflected by the deflection device onto the surface of photodetector, while when the equation (2) is fulfilled, the spherical mirror receives a converged luminous flux deflected by the deflection device and collects it onto the surface of photoconductor.

Abstract: A cylindrical lens for use in a light beam scanning optical system is arranged to have a luminous flux enter a deflection device in straight line in the direction of deflection. The luminous flux deflected by the deflection device enters a toroidal lens and is then directed toward the concave surface of the cylindrical mirror or a spherical mirror to converge on the surface of a photoconductor.

Abstract: A light amount correcting interference membrane having almost constant thickness and characteristic for increasing transmissivity corresponding to an increase of incidence angle of a laser beam is provided on a scanning light path extending from a rotary optical deflector to a recording medium in a scanning optical system. The laser beam deflected by the rotary optical deflector for scanning the recording medium is transmitted through the light amount correcting interference membrane wherein the scanning velocity of the laser beam reaching the peripheral portion of the recording medium is faster than that of the laser beam reaching the central portion, and an incidence angle becomes large and transmissivity becomes high.

Abstract: A cylindrical lens for use in a light beam scanning optical system is arranged to have luminous flux enter a deflection device for converting it into a straight line along a plane perpendicular to a rotation axes of the deflection device. The luminous flux deflected by the deflection device is turned over by the concave surface of a cylindrical mirror or spherical mirror to converge on the surface of a photoconductor through the cylindrical lens. The deflection device with the cylindrical lens and cylindrical mirror or the spherical mirror provided behind the deflection device in the light path fullfills the following equations..vertline.s/R.vertline..gtoreq.0.50.15<d/.vertline.R.vertline.<0.45(.vertline.d.sub.2 .vertline.+.vertline.d.sub.3 .vertline./.vertline.R.vertline.<0.

Abstract: A slit exposure type copying machine capable of copying with anamorphic magnification. The degree of the refractive action of at least one triangular prism is so set as to compensate for the difference between the magnification of projection means and the magnification corresponding to the speed of scanning means.

Abstract: An optical imaging system for a copier comprising at least a pair of multilens plates made from the same mold to have matched surface configurations. One of the pair of multilens plates is arranged to be rotated from the position of the other multilens plate through 180 degrees about an axis parallel to the longitudinal direction of the other multilens plate. A reflecting surface is positioned parallel to the axis of rotation for deflecting the optical path between the pair of multilens plates once or an odd number of times whereby a clear image is provided despite imperfections from molding.