Abstract: A three-group zoom lens includes first, second, and third lens groups, of negative, positive, and positive or negative refractive power, respectively. The second lens group includes a stop and the third lens group moves for focusing. When zooming from the wide-angle end to the telephoto end, the first and second lens groups become closer together. The zoom lens preferably satisfies specified conditions that ensure compactness, ease of manufacture, and favorable correction of aberrations. The zoom lens includes aspheric lens elements with lens surfaces defined by an aspheric lens equation that: (a) includes at least one non-zero coefficient of an even power of Y, and at least one non-zero coefficient of an odd power of Y, where Y is the distance of a point on the aspheric lens surface from the optical axis, and/or (b) includes at least one non-zero coefficient of Yi, where i is even and 16 or greater.

Abstract: A single focus lens is composed of four lens components of negative, positive, negative and positive refractive power, respectively, in order from the object side. The first lens, in order from the object side, has a concave surface on the image side, and a stop is positioned between the first lens and the second lens. The second lens has a convex surface on the object side, the third lens has a concave surface on the object side, and the fourth lens has a convex, aspherical surface on the image side such that the refractive power of the fourth lens becomes weaker towards the edge of the lens. Specified conditions are preferably satisfied in order to provide favorable correction of aberrations.

Abstract: A zoom lens is disclosed having four groups of positive, negative, positive, and positive refractive power, respectively, in order from the object side. The second lens group includes, in order from the object side, a biconcave or plano-concave lens, a biconcave lens, and a positive meniscus lens with its convex surface on the object side. The third lens group is a single lens having at least one surface that is aspherical. The fourth lens group includes a biconvex lens positioned between two meniscus lenses, and includes at least one surface that is aspherical. The first and third lens groups are fixed in position, the second lens group moves for zooming, and the fourth lens group moves for both zooming and focusing. A specified condition is satisfied to provide a zoom lens of small overall length, a zoom ratio that exceeds 6, a wide-angle of view, and favorably corrected aberrations.

Abstract: A three-group zoom lens includes, in order from the object side, a first lens group of negative refractive power, and second and third lens groups, each of positive refractive power. The first and second lens groups include negative and positive components and the third lens group is a single lens component. All but one lens component may be a single lens element. When zooming from the wide-angle end to the telephoto end, the first and second lens groups move closer together while the second lens group moves farther from the third lens group. The third lens group remains stationary during zooming but moves for focusing. The second lens group includes a diaphragm on its object side. Aspheric lens surfaces are disclosed. The zoom lens satisfies certain conditions for the focal lengths of the zoom lens and a component of the zoom lens, and for Abbe numbers of two lens elements.

Abstract: A light-scanning optical system having a function of correcting surface tilt comprises a light source 11; a first optical means 1; a light-deflecting means 14 for reflecting and deflecting a luminous flux by its deflecting/reflecting surface 15 so as to scan a surface to be scanned 18; a first lens 16 having a positive refracting power in each of the main scanning and sub-scanning directions, in which each of both sides is made of a toric surface; and a second lens 17 having a small negative refracting power, in which each of both sides is made of an aspheric surface. A semiconductor laser having a wavelength of 500 nm or shorter is used as the light source. The first and second lenses 16, 17 may be made of plastic. Thus, in a simple configuration, the light-scanning optical system can reduce its size and cost, while being able to respond to higher image density.

Abstract: A three-group zoom lens includes, in order from the object side, a first lens group of negative refractive power, and second and third lens groups, each of positive refractive power. The first and second lens groups include negative and positive components and the third lens group is a single lens component. All the lens components may be single lens elements. When zooming from the wide-angle end to the telephoto end, the second and third lens groups move toward the object side and all three lens groups move such that the group spacings decrease. The second lens group includes a diaphragm on its object side. A constant axial spacing between the second and third lens groups is maintained when zooming while the zoom lens is focused at infinity, and the third lens group is moved toward the object side when focusing from infinity to a near point.

Abstract: A three-group zoom lens includes, in order from the object side, a first lens group of negative refractive power, and second and third lens groups, each of positive refractive power. The first and second lens groups include negative and positive components and the third lens group is a single lens component. All the lens components may be single lens elements. When zooming from the wide-angle end to the telephoto end, the second and third lens groups move toward the object side and all three lens groups move such that the group spacings decrease. The second lens group includes a diaphragm on its object side. A constant axial spacing between the second and third lens groups is maintained when zooming while the zoom lens is focused at infinity, and the third lens group is moved toward the object side when focusing from infinity to a near point.

Abstract: A single focus lens is composed of four lens components of negative, positive, negative and positive refractive power, respectively, in order from the object side. The first lens, in order from the object side, has a concave surface on the image side, and a stop is positioned between the first lens and the second lens. The second lens has a convex surface on the object side, the third lens has a concave surface on the object side, and the fourth lens has a convex, aspherical surface on the image side such that the refractive power of the fourth lens becomes weaker towards the edge of the lens. Specified conditions are preferably satisfied in order to provide favorable correction of aberrations.

Abstract: A zoom lens is disclosed having four groups of positive, negative, positive, and positive refractive power, respectively, in order from the object side. The second lens group includes, in order from the object side, a biconcave or plano-concave lens, a biconcave lens, and a positive meniscus lens with its convex surface on the object side. The third lens group is a single lens having at least one surface that is aspherical. The fourth lens group includes a biconvex lens positioned between two meniscus lenses, and includes at least one surface that is aspherical. The first and third lens groups are fixed in position, the second lens group moves for zooming, and the fourth lens group moves for both zooming and focusing. A specified condition is satisfied to provide a zoom lens of small overall length, a zoom ratio that exceeds 6, a wide-angle of view, and favorably corrected aberrations.

Abstract: The present invention includes a first plate (14) and a second plate (15) which perform a coarse adjustment of a cylinder mirror (245) by moving the cylinder mirror (245) linearly in the substantially vertical and parallel directions with respect to an appropriate plane surface of a reflective surface (RS) of the cylinder mirror (245), and the second plate (15), a second plate opening section (15b), a setscrew (24), and a hexagon shaft (25) which perform a fine adjustment in the position of the cylinder mirror (245) by moving linearly only in the substantially parallel direction after the coarse adjustment has been completed.

Abstract: An optical system and optical scanning apparatus can form a minute beam spot and big size images. The optical scanning apparatus deflects a beam with a polygon mirror, and focuses the beam on a target surface through a f&thgr;-lens, a cylindrical lens, and a cylindrical mirror. The scanning stroke on the target surface is longer than 500 mm, and the incident angle in the sub-scan direction of the incident light into the cylindrical mirror is 15 degrees or less. The ratio of the beam size DX in the sub-scan direction of the incident light into the cylindrical mirror to the distance DL between the cylindrical mirror and the target surface satisfies 0.03<DX/DL<0.06.

Abstract: An objective lens for an optical recording medium comprises two lenses each having a positive refracting power disposed within a laser luminous flux having a wavelength of 360 to 450 nm outputted from a laser diode. The two lenses have at least one diffractive optical surface and at least one aspheric surface, and are set so as to have a total NA of at least 0.7.

Abstract: An optical scanner assembly in which a pair of F&thgr; lenses are arranged symmetrically across a single deflector means and a reflector for introducing a light beam from at least one of a plurality of light sources to the deflector means is arranged on the side opposite to that light source with respect to an axis of symmetry of the F&thgr; lenses so that the optical path up to the reflector crosses the axis of symmetry, thereby securing the optical path length from the light source to the deflector for the miniaturization of the optical scanner assembly and allowing easy adjustment for equalizing the optical path lengths of all the light sources.

Abstract: An optical scanner assembly in which a pair of F&thgr; lenses are arranged symmetrically across a single deflector means and a reflector for introducing a light beam from at least one of a plurality of light sources to the deflector means is arranged on the side opposite to that light source with respect to an axis of symmetry of the F&thgr; lenses so that the optical path up to the reflector crosses the axis of symmetry, thereby securing the optical path length from the light source to the deflector for the miniaturization of the optical scanner assembly and allowing easy adjustment for equalizing the optical path lengths of all the light sources.

Abstract: An optical system and optical scanning apparatus can form a minute beam spot and big size images. The optical scanning apparatus deflects a beam with a polygon mirror, and focuses the beam on a target surface through a f&thgr;-lens, a cylindrical lens, and a cylindrical mirror. The scanning stroke on the target surface is longer than 500 mm, and the incident angle in the sub-scan direction of the incident light into the cylindrical mirror is 15 degrees or less. The ratio of the beam size DX in the sub-scan direction of the incident light into the cylindrical mirror to the distance DL between the cylindrical mirror and the target surface satisfies 0.03<DX/DL<0.06.

Abstract: An objective lens having no more that two lens elements with refractive power is disclosed for reading or writing at high density on a recording medium. The first lens element, in order from a light source side, is biconvex and includes at least one aspheric surface so that it is individually well-corrected for spherical aberration. The second lens element is of a meniscus shape with its concave surface on the recording medium side of the objective lens. If the objective lens is used without a cover glass at the recording medium, the convex surface of the second lens element is made to have an aplanatic surface, which is a surface that is capable of changing the convergence or divergence of a cone of rays without introducing any spherical aberration, coma or astigmatism. Whether or not there is a cover glass at the recording medium, the following condition is satisfied 0.8<R4/BF<1.

Abstract: A zoom lens formed of no more than four lens groups having refractive power of, in order from the object side, positive, negative, positive, and positive. The first and third lens groups are fixed in position, whereas the position of the second lens group along the optical axis is varied to change the focal length during zooming, and the position of the fourth lens group is adjusted along the optical axis so as to compensate for what otherwise would be movement of the image surface with zooming and distance to the object. The second lens group includes a negative lens element having a concave surface or a planar surface on its object side, a combined lens which includes a biconcave lens element joined to a positive meniscus lens element with its convex surface on the object side. The third lens group consists of a single lens element with at least one surface thereof being aspherical, and the fourth lens group includes a lens element having an aspherical surface.

Abstract: A photographic lens for an electronic still camera having five lens components, with refractive powers in sequential order from the most object side, as follows: negative, positive, positive, negative and positive. A stop is positioned between the second lens component and the third lens component. The photographic lens has a short overall length, a wide angle of view, a large numerical aperture, and high resolution as a result of the lens being favorably corrected for aberrations. The first lens component includes at least one ashperical surface, the second lens component has a convex surface on the image side, the third lens component has at least one aspherical surface, and has a convex surface on the image side. The fourth lens component has a concave surface on the object side, and the fifth lens component has a convex surface on the image side.

Abstract: A zoom lens formed of no more than four lens groups having refractive power of, in order from the object side, positive, negative, positive, and positive. The first and third lens groups are fixed in position, whereas the position of the second lens group along the optical axis is varied to change the focal length during zooming, and the position of the fourth lens group is adjusted along the optical axis so as to compensate for what otherwise would be movement of the image surface with zooming and distance to the object. The second lens group includes a negative lens element having a concave surface or a planar surface on its object side, a combined lens which includes a biconcave lens element joined to a positive meniscus lens element with its convex surface on the object side. The third lens group consists of a single lens element with at least one surface thereof being aspherical, and the fourth lens group includes a lens element having an aspherical surface.

Abstract: A synchronous light detector for an optical scanning apparatus comprises a cylindrical lens 14 and a light-receiving device 15. The cylindrical lens 14 is disposed between an imaging lens 8 of the optical scanning apparatus and the light-receiving device 15 so as to have a generator direction parallel to a scanning direction of a light beam. The light-receiving surface of the light-receiving device 15 is disposed at a position shifted from a paraxial image point P in the direction orthogonal to the scanning plane of the light beam by a predetermined distance &Dgr; along the optical axis direction of the light-receiving device 15 when the deflecting point of the light beam caused by a polygon mirror 6 is taken as an object point. As a consequence, the synchronous signal of the optical scanning can be detected correctly even when there is a flaw or dirt on the light-receiving surface.