Abstract: A polygon mirror is enclosed in an airtight cap that is provided with a polygon window. By having the normal line to the surface of the polygon window tilt a predetermined angle in the main scanning direction with respect to the principal ray of the light beam that is to be applied to the polygon window, the reflected light, which is a part of the light beam reflected by the surface of the polygon window, is not applied to the image forming area of a photoconductive drum.

Abstract: In an optical system, the scanning center axis of a scanning lens, the principal ray of a laser beam applied to the scanning lens, and the rotational axis of a polygon mirror are in one plane. By forming a thin film layer on the deflecting facets, the exposure quantity of a photo conductor, which decreases as the incident angle to the deflecting facet increases, is corrected. The thin film layer has the increasing ratio of the reflectance that increases as the incident angle, which principal ray of the laser beam forms with the normal line to the deflecting facet of the polygon mirror, increases.

Abstract: The image forming apparatus provides a plurality of recording units to form images based on their respective image data, overlaying the images formed by the plurality of recording units on a single transfer member traveling in a predetermined direction, control means to sequentially cause registration patterns of predetermined shape to be formed by the plurality of recording units, and detecting means to detect each registration pattern on the transfer member in at least two locations in both the diretion of travel of the transfer member and a direction perpendicular thereto, and output non-integrated detection values.

Abstract: Laser beams LK and LY are respectively emitted from laser diodes 51K and 51Y and incident on a mirror face of a polygon mirror 55 via collimator lenses 52K, 52Y and first cylindrical lenses 53K, 53Y. The laser beams LK and LY are reflected off the polygon mirror 55 and deflected. Incidence angles of the laser beams LK and LY are set so that the laser beams LK and LY intersect with each other at a position P which is located before the polygon mirror 55.

Abstract: In a multibeam scanning optical apparatus of a type where two parallel lines are simultaneously scanned by two laser beams irradiated from two semiconductor lasers, stable images are formed on the scanned surface by the two laser beams and the cost is reduced. The two laser beams irradiated from the two semiconductor lasers are directed substantially in the same direction through a beam splitter and then shaped by a condenser lens into two luminous fluxes whose optical axes are substantially parallel to each other. In another arrangement, the semiconductor lasers are directly secured to a surface of the beam splitter by use of an ultraviolet setting resin.

Abstract: A laser beam scanning optical apparatus has a focusing lens having different optical powers in the main scanning direction and the sub-scanning direction, moving means for moving the focusing lens on an optical direction, detecting means for detecting a state of convergence of the laser beam on a scanned surface, and control means for adjusting the convergence position of the laser beam by moving the focusing lens via driving said moving means based on the detection result of the detection means. In the aforementioned construction, the state of the convergence of the laser beam on a scanned surface is adjusted in the main scanning direction and the sub-scan direction by moving the focusing lens in an optical axis. The focusing lens is moved to a position of optimum convergence based on the construction of the optical system by detecting the state of convergence in the main scan direction and the sub-scan direction via a detecting means.

Abstract: A laser beam optical scanning device which focuses and scans a laser beam emitted from laser diode 1 in the arrow b direction on a photosensitive drum 40 via focusing lens 3, polygonal mirror 6, and f.theta. lens 7. The scanning laser beam enters a convergence state detector 10, which detects the amount of dislocation of the convergence position. The amount of positional change is calculated to correct the convergence position based on the detected amount of dislocation, and the focusing lens 3 is moved on the optical axis of the lens via motor 21 to correct the beam convergence position. When processing is executed to correct the convergence position in the intermediate zone of the image formign range and the calculated amount of positional change exceeds a limit value, a detection error is assumed, and the focusing lens 3 is moved an amount less than the limit value.

Abstract: A laser beam scanning optical apparatus which images and scans a laser beam emitted from a laser diode on a photo-sensitive drum through a focusing lens, a polygon mirror and an f.theta. lens. An SOS photosensor detects the scanned laser beam and generates a detection signal. The laser diode is controlled to perform pulse emission a specified time after the generation of the detection signal. The pulse beam is incident to a beam detector which adopts a knife edge method, and the amount of a focal shift is detected. The focusing lens is moved along the optical axis in accordance with the detected amount of a focal shift to correct the position of the image point.

Abstract: A laser beam scanning optical apparatus which has Moire fringes generating elements which is located near a position optically equivalent to a scanning surface and modulates a laser beam emitted from a laser source to generate Moire fringes. The Moire fringes generating elements comprises, for example, a first filter which has spatial grating and a second filter which has spatial grating which slants slightly with respect to the spatial grating of the first filter, the first filter and the second filter being arranged upstream and downstream respectively in an optical path. The laser beam scanning optical apparatus further has a light receiving element for receiving the Moire fringes generated by the Moire fringes generating elements. Focusing means for correcting a position of an image point of the laser beam is driven in accordance with an output of the light receiving element.

Abstract: A laser beam scanning optical apparatus which has a laser source unit, a collimator lens, a cylindrical lens, a polygon mirror and a scanning lens with an f.theta. function. The collimator lens is a bifocal lens, and because of the bifocal collimator lens, a part of the laser beam is focused on a point before the surface of a photosensitive member, and another part of the laser beam is focused on a point after the surface of the photosensitive member. Also, the cylindrical lens can be a bifocal lens. In this case, even when the magnification ratio in the sub scanning direction is designed small, the focal length of the cylindrical lens does not have to be lengthened.

Abstract: An optical device having an optical element, a base plate which has a mount surface for setting the optical element, a first holding member composed of at least a hole and a projection so as to permit the optical element mounted on the base plate to move longitudinally and a second holding member composed of a hole and a projection so as to restrain the optical element from moving in a direction orthogonal to an optical axis.

Abstract: An optical device comprises an optical lens and a mounting assembly for securing the optical lens to a support surface. The optical lens has a longitudinal axis and has first and second projections; the mounting assembly includes a clamp member which has a clamp surface and depresses the optical lens downwardly through contact of the clamp surface with the optical lens so as to mount the optical lens on the support surface. The clamp member is formed, on the clamp surface, with first and second holes engageable with the first and second projections of the optical lens, respectively; the second hole is an elongated opening extending in the longitudinal direction of the optical lens.

Abstract: An optical apparatus includes a laser beam emitter for outputting a laser beam modulated in accordance with image information, and a lens unit resting on a lens mount. The lens unit includes, all formed integral with one another, an effective lens portion, a cylindrical portion surrounding a side surface of the effective lens portion, and projections extending from peripheral positions of the cylindrical portion. The lens mount includes a holder for holding the cylindrical portion of the lens unit to be rotatable and axially slidable on an optical axis of the laser beam, and a groove formed in the bottom of the holder for receiving the projection.

Abstract: A mirror which is incorporated in an optical device and is made of plastic, comprising: an effective portion which has a constant thickness and a reflecting surface; and a reinforcing portion which is so provided as to enclose the effective portion and reinforces the effective portion from a periphery of the effective portion; the reinforcing portion being formed integrally with the effective portion; the reinforcing portion having a thickness equal to the thickness of the effective portion; the reinforcing portion having a constant width.

Abstract: An optical beam scanning apparatus wherein a resin polygonal scanner deflects a light beam radiated from a laser diode as the polygonal scanner is rotating. The polygonal scanner is pressed by a pressing member against a scanner rest which rotates together with a rotary shaft of a motor and thus fixed on the scanner rest. The pressing member has a plurality of tabs, and the polygonal scanner is pressed evenly when the tabs pierce the polygonal scanner.

Abstract: An optical scanning device for scanning the surface of a photosensitive member with an optical beam emitted from a light source. The optical scanning device has a casing for accommodating a plurality of optical members. The casing is provided with a baseplate having a top surface, a bottom surface and a curved portion integrally formed with the top surface and the bottom surface so as to connect the top surface and the bottom surface. In the casing, the plurality of optical members are dividedly attached to the top and bottom surfaces of the baseplate, and therefore the curved portion is provided with an aperture for transmitting the optical beam therethrough.