Abstract: A beam shaping optical system which is provided with a first wedge prism having two refractive surfaces defining a first principal section, and a second wedge prism having two refractive surfaces defining a second principal section that is parallel to the first principal section, wherein a reference ray of light forms incident angles at each of the refractive surfaces of the prisms satisfying the following condition (1): ##EQU1##

Abstract: A scanning optical comprises a light source, a rotating mirror for deflecting and scanning a light beam emitted form the light source, a scanning lens for converging the light beam deflected by the rotating mirror onto an object surface, a transparent cover plate obliquely disposed between the rotating mirror and the scanning lens, and a transparent compensation plate obliquely disposed between the cover plate and the object surface. The cover plate has no power and a normal of the cover plate is inclined at a predetermined angle with respect to a main scanning plane. The compensation plate has no power and a normal of the compensation plate is inclined at a predetermined angle with respect to the main scanning plane.

Abstract: A scanning optical system includes a polygonal mirror, enclosed in a housing, which deflects light. The housing is provided with a transparent plane-parallel plate, parallel to a reflecting surface of the polygonal mirror, through which a laser light source emits a laser beam into the housing. An image forming optical system, provided between the polygonal mirror and an objective surface to be scanned, has a power at least in a main scanning direction. The laser beam is made incident on the polygonal mirror in a direction inclined toward a sub-scanning direction, with respect to a direction perpendicular to the reflecting surface of the polygonal mirror.

Abstract: A diffractive multi-focal objective lens formed, macroscopically, as a double convex lens having convex aspherical surfaces of which radii of curvatures are larger as a function of distance from the optical axis. One lens surface is provided with a microscopic diffractive lens construction that is formed as ring zones concentric about the optical axis. The diffractive lens construction is designed so that the higher the diffractive order, the shorter the focal length. For example, a first order diffractive light beam forms a first focal point F1 on the optical axis, and a second order diffractive light beam forms a second focal point F2 on the optical axis that is nearer to the lens than the first focal point F1.

Abstract: An optical data recording and reproducing apparatus includes a laser source, a collimating lens made of a single lens having a positive power to collimate the divergent laser beams emitted from the laser source, and an objective lens which is to converge the collimated light onto a data recording surface of a data recording medium. The chromatic aberration of the objective lens is corrected to reduce the back focal distance thereof as the wavelength increases to cancel the chromatic aberration of the collimating lens.