Abstract: This invention intends to provide an optical pickup of which it is possible to limit aberrations within a tolerable limit without incorporating a special device for that purpose even if errors arise in thickness of component lenses of a two-lens system constituting an element of the pickup. This object is achieved by providing an optical pickup incorporating a two-lens system with first and second lenses 13 and 14 being arranged in the following manner: the first lens has a first surface 15 to receive a laser beam radiated from a semiconductor laser and a second surface 16 to direct the laser beam transmitted from the first surface 15 towards the second lens 14; the second lens 14 has a third surface 17 to receive the light flux transmitted from the second surface 16 and a fourth surface 18 to direct the light flux transmitted from the third surface 17 towards an optical disc placed opposite thereto; and the first and fourth surfaces are used as a reference during positioning.

Abstract: The present invention is directed toward a wide-angle lens. Because of a small quantity (two) of lens elements, the wide-angle lens facilitates size and weight reduction and permits low-cost manufacture. The lens is made from plastic, which permits further cost reduction. The lens is particularly useful when employed in CCD cameras.

Abstract: A low-cost wide-angle lens assembly being comprised of a decreased number of lenses yet capable of properly correcting optical aberrations. The second lens in each lens group from the minimum to the maximum horizontal viewing angle is commonly used, and the first lens in each lens group from a reference angle to the maximum horizontal viewing angle is commonly used, thus reducing the total number of required lenses. Aberrations are favorably corrected by satisfying predetermined conditions as to focal distances and back focuses of the lenses.

Abstract: A compact and lightweight zoom lens includes a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, and performs zooming by changing the distance between the first and second lens units. The zoom lens satisfies required conditions related to the glass material, lens shape and optical power of the first and second lens units, and achieves a high zooming ratio ranging from 2.6 to 3 and high optical performance.

Abstract: An imaging lens with a wide image angle, that is compact and bright, is composed of a first lens group of negative refracting power which has three lens elements which are of positive, negative, and positive refracting power, respectively, and a second lens group of positive refracting power. By providing the first lens element on the object side of the first lens group with an aspherical surface, and by fixing the range of the spacing between the first lens element and the second lens element to satisfy a first condition, as well as fixing the spacing between the second lens element and the third lens element to satisfy a second condition, the distortion of the imaging lens is reduced and its resolution is increased.

Abstract: A zoom lens system has, from the object side, a first lens unit having a positive optical power and a second lens unit having a negative optical power. The second lens unit is provided at the image side of said first lens unit with a variable air space formed between said first and second lens units. The zooming from the shortest focal length condition to the longest focal length condition is performed by decreasing said variable air space. The zoom lens system fulfills the following conditions:tan .omega.W.gtoreq.0.7 ##EQU1## where, .omega.W represents a half angle of view in the shortest focal length condition;fT represents a focal length of the entire zoom lens system in the longest focal length condition; andTLW represents a total length of the entire zoom lens system (a distance between a summit of the most object side surface of the entire lens system and the image plane).

Abstract: A zoom lens system is composed of two lens units. The first lens unit is arranged at an object-side end and the second lens unit is arranged at an image-side end. The first lens unit has one lens element of a positive refractive power. The second lens unit has two lens elements. One is an aspherical plastic lens of non-refractive power. The other is a lens having a negative refractive power. During zooming from a wide angle end to a telephoto end, the distance between the first and second lens units is decreased.

Abstract: A compact two-group zoom lens, wherein zooming is accomplished by changing the distance between the two lens groups. In order from the object side, the first lens group G1 is of positive refracting power and includes a negative meniscus lens element L.sub.1 with its concave surface on the object side, a positive meniscus lens element L.sub.2 made of plastic having two aspherical surfaces with its convex surface on the object side, and a biconvex lens element L.sub.3 having different surface curvatures, with its surface of stronger curvature on the image side. The second lens group G2 includes a positive meniscus lens element L.sub.4 that has two aspherical surfaces with its concave surface on the object side, and a negative meniscus lens element L.sub.5 with its concave surface on the object side. It is preferable that lens element L.sub.4 has an aspherical surface of positive refracting power and lens element L.sub.2 has an aspherical surface of negative refracting power.

Abstract: An optical system for a view finder reduced in the overall length without aggravation of the optical performance has a negative power object lens and a positive power eyepiece lens each of which has an asphrical surface at at least one side respectively. The negative power object lens having a concave object side lens surface is comprised of a rectangular-shaped solid lens base with its four corners cut away along periphery of the concave lens surface.

Abstract: A zoom lens system has a plurality of lens units. Zooming is performed by varying distances between the lens units. A gradient index lens is included in the lens units. The gradient index lens has a gradient index in a direction vertical to an optical axis. The gradient index lens has at least one aspherical surface.

Abstract: A zoom lens system comprises a first lens group of positive power and a second lens group of negative power. The zoom lens system is arranged to perform a zooming operation by varying a distance between the first lens group and the second lens group. Furthermore, the first lens group comprises a front sub lens group of negative poser and a rear sub lens group of positive power. Still further, the front sub lens group comprises a first single lens element of negative power and a second single lens element having an aspherical surface on which the radius of curvature becomes larger in the off-axis region, and the rear sub lens group of the first lens group comprises a cemented lens having a positive lens element and a negative lens element. Moreover, the zoom lens system satisfies various conditions.

Abstract: A reading lens system composed, in order from the object side, of a first positive biconvex lens component, a second positive meniscus lens component convex toward the image side and an aperture stop disposed on the image side of the second lens component. By setting a distance as measured from a first surface to an aperture stop of the reading lens system adequately, it is configured so as to have a short total length and allow little variation of a size of an image even when the image is defocused due to a variation of an object location.

Abstract: According to the present invention the magnifier lens comprises two lens elements. More specifically, from a front, eye side to a rear, object side there is a front, positive lens element, and a rear, meniscus lens element. The front, positive power lens element has at least one aspheric surface and an Abbe V-number V.sub.1. The rear, meniscus lens element has an Abbe V-number V.sub.2. The front and the rear lens elements, in combination, contain at least one diffractive surface. The rear, meniscus lens element has front and rear refractive surfaces, both of which are concave toward the object side. The rear refractive surface is positionable within 5 mm of an associated object to be viewed from the eye side. This rear surface is an aspheric surface of negative refractive power. The Abbe V-numbers satisfy the following inequalities 50.4<V.sub.1 <65, 25.4<V.sub.2 <40, and V.sub.1 -V.sub.2 >25.

Abstract: A photographic lens consists of a first meniscus lens element having a concave surface directed to the image, and a second meniscus lens element having a concave surface directed to the object, arranged in this order from the object side. Both surfaces of the first lens element are spherical, and at least one surface of the second lens element is aspherical. The absolute value of the focal length of the first lens is smaller than the absolute value of the focal length of the second lens.

Abstract: A object of the present invention is to provide an objective lens that two non spherical surfaces are combined and a numeral aperture is more than 0.7, and to provide an optical pick-up apparatus which can be used for an optical recording medium having high information recording density by using this objective lens.There is disclosed that a first surface is a rotating ellipse surface (a cone constant k: -1.ltoreq.k<0), and curvature of the first surface, glass materials (refractive index) of a first lens 1 and a main plane interval d of the total of combination of two lenses are properly established to satisfy the fixed relational expression.

Abstract: Variable focal length lens system comprises two adjacent lens units, one stationary, the other movable. These lens units are in order from an object side towards an image side(i) A first lens unit possessing divergent refractive power. The first lens unit is the front most lens unit. It consists of a single negative lens component.(ii) A second lens unit possessing convergent refractive power. The second lens unit, includes at least two positive power lens components and an aperture stop.

Abstract: In a compact wide-angle zoom lens having a two-group configuration composed of positive and negative lens groups, each lens is set to have a predetermined form and satisfy a predetermined range of conditional expression, thereby attaining a high brightness at its wide-angle end, a large angle of view, and a small lens thickness at its telephoto end. The first lens group comprises a biconcave negative first lens L.sub.1 ; a cemented lens composed of a negative second lens L.sub.2 and a biconvex positive third lens L.sub.3 ; and a biconvex positive fourth lens L.sub.4. The second lens group comprises a fifth lens L.sub.5 having an aspheric surface; a sixth lens L.sub.6 having a positive meniscus form with a convex surface directed onto the image side; and a seventh lens L.sub.7 having a negative meniscus form with a convex surface directed onto the image side. The zoom lens further satisfies the following conditional expressions:0<(r.sub.3 +r.sub.4)/(r.sub.3 -r.sub.4)<3.5, 0.5<(r.sub.11 +r.sub.12)/(r.

Abstract: In a non-flexible endoscope consisting of an insertion section and an eyepiece section which are separable from each other, an optical system configured so as to correct chromatic aberration produced by an observation optical system disposed in the insertion section with an eyepiece optical system disposed in the eyepiece section. The optical system according to the present invention selects a simple composition for the observation optical system so that it is manufacturable at a low cost and disposable, and is configured so as to have favorable optical performance as a whole by correcting chromatic aberration produced by the observation optical system with the eyepiece optical system.

Abstract: A zoom lens comprising, from the object end, a positive power first lens having a convex image side surface and a negative power second lens having a curvature on a concave object side surface larger than on an image side surface, the first and second lenses being movable relative to each other to vary the focal length of the zoom lens, the zoom lens satisfying the following relations:0.05<d.sub.1 /f.sub.w <0.20-0.25<R.sub.2 /f.sub.w <-0.15-0.65<R.sub.3 /f.sub.w <-0.35where d.sub.1 is the axial distance between the surfaces of the first lens;f.sub.w is the focal length at the wide angle end of the whole zoom lens;R.sub.2 is the radius of curvature of the image side surface of the first lens; andR.sub.3 is the radius of curvature of the object side surface of the second lens.

Abstract: In a configuration constituted by two lens sheets, the ranges of levels of refractive index n and Abbe number .nu. of the image-side lens made of a biconvex lens are specified in order to realize an imaging lens constituted by two lens sheets which can attain a long back focus, a relatively wide angle of view, a high brightness, a small size, and a lower manufacturing cost. The imaging lens comprises, successively disposed from the object side to the image side, a concave lens and a biconvex lens, while at least one surface of the concave lens is an aspheric surface. Also, assuming that the refractive index and Abbe number of the biconvex lens are respectively n and .nu., the following conditional expressions (1) and (2):1.55.ltoreq.n (1)35.ltoreq..nu. (2)are satisfied.

Abstract: A zoom lens system of compact size having a small number of lenses and a large field area is provided, comprising, in the following order from the object side, a first lens group G1 with a negative refractive power and a second lens group G2 with a positive refractive power, wherein zooming is executed by changing dead space between lens groups G1 and G2. The first lens group G1 comprises, in the following order from the object side, a first lens group front group G.sub.1F with a negative refractive power, and a first lens group rear group G.sub.1R with either a negative refractive power or a positive refractive power having at least one set of color erasable negative lens components L.sub.n and positive lens components L.sub.p. Focusing is executed by moving only front group G.sub.1F.

Abstract: An objective lens for an endoscope includes a front lens of negative power, an aperture stop, and a rear lens group of positive power in this order from the object side. At least one surface of the front lens group and/or the rear lens group is a compound aspherical lens made of a glass lens and a transparent layer applied to the glass lens surface. A surface of the transparent layer farther from the glass lens is an aspherical surface. The refractive index n of the glass lens to which the transparent layer is applied is more than 1.65 (n>1.65).

Abstract: A zoom lens system is composed of two lens units. The first lens unit is arranged at an object-side end and the second lens unit is arranged at an image-side end. The first lens unit has one lens element of a positive refractive power. The second lens unit has two lens elements. One is an aspherical plastic lens of non-refractive power. The other is a lens having a negative refractive power. During zooming from a wide angle end to a telephoto end, the distance between the first and second lens units is decreased.

Abstract: An imaging lens provided with a first component lens (L.sub.1), which is a negative meniscus lens, whose convex surface has a large curvature and faces an object to be imaged, and with a second component lens (L.sub.2) that is a convex lens having a positive power. Moreover, as a whole, the imaging lens employs at least two aspherical surfaces. Thereby, various aberrations are corrected favorably. Further, this enables the effective use of plastic lenses. In addition to the provision of the first and second component lenses, the imaging lens satisfies the following configurational conditions:0.3<f.sub.2 /F<0.99 (1)8>F>D.sub.2 (2)where F designates a focal length of the imaging lens; f.sub.2 a focal length of the second component lens (L.sub.2); and D.sub.2 the distance between the first component lens (L.sub.1) and the second component lens (L.sub.2).

Abstract: A zoom lens system composed, in order from the object side, of a first positive lens unit and a second negative lens unit, and configured to change a magnification thereof by varying an airspace reserved between the first lens unit and the second lens unit. The first lens unit is composed, in order from the object side, of a first negative lens element, a second plastic lens element which has at least one aspherical surface and a remarkably weak refractive power, and a cemented lens component consisting of a third negative lens element and a fourth positive lens element.

Abstract: A zoom lens system having two, positive and negative, lens units, which is designed so that the number of constituent lenses is minimized to lower the cost and reduce the size, and yet high performance is realized, and that deterioration of the performance caused when the lenses are incorporated into a lens frame is minimized, and assembling is also facilitated. The zoom lens system has a 1-st lens unit (G1) of positive power and a 2-nd lens unit (G2) of negative power and is adapted to effect zooming by varying the spacing between the 1-st and 2-nd lens units (G1 and G2). The 1-st lens unit (G1) includes a single cemented lens (L.sub.12) composed of a negative lens (L.sub.1) and a positive lens (L.sub.2). The 1-st lens unit (G1) has at least one aspherical lens surface and satisfies the condition of .nu..sub.P -.nu..sub.N >15, where .nu..sub.N is the Abbe's number of the negative lens (L.sub.1), and .nu..sub.P is the Abbe's number of the positive lens (L.sub.2).

Abstract: An optical system for magnifying a display panel includes a magnifying lens disposed in front of a display panel. The magnifying lens is constructed with two lenses respectively having convex surfaces opposite each other. At least one of the two convex surfaces is aspherical. A transverse aberration of the magnifying lens is less than the diameter of the pupil of an eye at a point where the eye is positioned. The lens for the optical system is a Fresnel lens whose vortex center is located on its edge. An apparatus for magnifying display panels according to the invention includes an instrument to be viewed distantly and instruments to be viewed not distantly. The instrument to be viewed distantly is disposed distant from the Fresnel lens under a center portion of the Fresnel lens, whereas the instruments to be viewed not distantly are disposed close to the Fresnel lens under an edge portion of the Fresnel lens.

Abstract: Even when the refractive index of the plastic material forming a plastic lens fluctuates due to temperature change and the like, the change in the paraxial back focus amount caused by this fluctuation is canceled by spherical aberration which is generated by an aspheric surface and yields an action in a direction opposite thereto, whereby the fluctuation in refractive index in the plastic lens due to temperature change and the like is suppressed while a demand for attaining a compact size with high performances is satisfied. The second lens (L.sub.2) in the first lens group (G.sub.1) and the fourth lens (L.sub.4) in the second lens group (G.sub.

Abstract: An optical scanning lens is provided with a lens configuration for focusing and correction of field curvature and scanning speed of a deflected laser beam. The lens configuration includes a meniscus lens and a positive meniscus lens sequentially aligned and sharing an optical axis with the optical scanning lens. Specific parameters are provided for each lens in order to satisfy the relationship:-0.25<f.sub.2 /f.sub.1 <0.11,between respective focal lengths of the lenses, and the surfaces of the meniscus lens have radii of curvature satisfying the relationship:0.8<r.sub.1 /r.sub.2 <1.25.The above relationships provide for correction of scanning speed and field curvature in a main scanning direction. Specific lens surfaces are identified and provided with an aspheric surface which provides additional field curvature correction in the main scanning direction.

Abstract: An eyepiece system for use with binoculars, etc. which comprises, in order from a side of an observer's eye, a first convex lens element having a strongly convex surface on a side of an objective lens, and a cemented doublet lens component which consists of a second biconvex lens element and a third negative or negative meniscus lens element. This eyepiece system is configured to have a wide apparent field angle and favorably corrected aberrations by selecting an adequate value for a distance as measured from a front focal point of the eyepiece system to a vertex on a surface of the first lens element which is located on the side of the observer's eye.

Abstract: A zoom lens system comprises a stationary negative power singlet and a positive power singlet which is movable between two specific axial positions so as to change its focal length between the shortest focal length suitable for wide angle photography and the longest focal length suitable for a tele-photography, and satisfies the following condition:f.sub.W .multidot..beta..sup.1/2 /(1+.beta..sup.1/2)<f.sub.2 .ltoreq.(2.multidot.F.sub.NO .multidot.LD/1500).multidot..beta..sup.1/2 /(1-.beta..sup.1/2).sup.2where f.sub.w is the overall focal length of the zoom lens system at the wide angle end, .beta. is the zoom ratio of the zoom lens system which is expressed by a ratio of the overall focal length between the tele-photo end and the wide angle end, f.sub.2 is the focal length of the second lens group, F.sub.NO is the F number of the zoom lens system at the wide angle end, and LD is the diagonal length of the image area.

Abstract: A wide angle lens comprises in order from the object end an aperture stop, a first meniscus lens .sub.L1 having a convex object end surface and a second positive power lens element L.sub.2, the lens satisfying the following conditions:-0.10<f.sub.2 /f.sub.1 <0.74.0<f/R.sub.1 <7.50<f/R.sub.3 <1.60.01<D/f<0.22where f.sub.1, f.sub.2 and f are the focal length of the first lens L.sub.1, the second lens L.sub.2 and the overall lens system, respectively, R.sub.1 and R.sub.3 are the radii of the object end surfaces of the first and second lenses L.sub.1 and L.sub.2, respectively, and D is the axial distance between the object end surface of the first lens L.sub.1 and the image plane.

Abstract: A dual-focus objective lens for an optical pickup which is compatible with both 0.6 mm and 1.2 mm disks is compensated in its aberration with respect to a light spot on a recording plane of the loaded disk and is composed of a first lens and a second lens. The loaded positions of the 0.6 mm disk and 1.2 mm disk in view of the second lens are different from each other. An optical pickup having the dual-focus objective lens can reproduce a signal with a high signal-to-noise ratio and has improved light efficiency. Also, an optical pickup enabling recording as well as reproduction is obtained.

Abstract: An image transmitting optical system comprising at least two bar-shaped lens components and constructed to have a numerical aperture enlarged by reserving an adequate space between an image of object to be transmitted and one of surfaces of the bar-shaped lens component which is located closest to the image of the object. In this image transmitting optical system, spherical aberration and curvature of coma are corrected by designing each of the bar-shaped lens components as a cemented lens component consisting of two bar-shaped lens elements.

Abstract: A zoom lens system comprises a front meniscus lens of negative power and a rear meniscus lens of positive power which are shifted along an optical axis of the zoom lens system to change a relative axial distance so as to achieve zooming continuously from a wide angle end to a telephoto end and satisfies the following condition:1.85<f.sub.1 /f.sub.2 <-1.5where f.sub.1 and f.sub.2 are the focal length of the front and rear meniscus lenses, respectively.

Abstract: An optical magnifier, preferably having only two elements and including a rear negative surface associated with an object to be viewed, which is aspheric. The aspheric surface follows a formula having a sag which is positive to help effect correction for field curvature, astigmatism and distortion. Preferably the lens has at least one other aspheric surface and a diffractive surface. The diffractive surface is preferably on a curved surface to assist in improving the quality of the magnifier with a limited number of elements.

Abstract: A camera for taking a photograph on a picture plane of a rolled film which has a width of 24 mm. The camera includes: a photographing lens of which a convex surface is faced toward an object to be photographed and satisfying: 18.ltoreq.f.ltoreq.32 and f.sup.2 /90.ltoreq.F.ltoreq.16 in which f is the focal length of the photographing lens and F is the F-number of the photographing lens; at least one diaphragm; and the picture plane having a picture frame satisfying: 23.ltoreq.L.ltoreq.32 and 1.5.ltoreq.L/S 6.5 in which L (mm) is the long dimension of the picture frame, S is the short dimension of the picture frame, and an image of the object is focused on the picture plane through the photographing lens and the diaphragm.

Abstract: An optical system comprising two lens elements one of which is biaspheric, the optical system is suitable for use in photographic devices such as single-use cameras having curved image planes. This optical system can operate at low F-numbers while maintaining an excellent performance.

Abstract: To attain a compact wide-angle 2-unit zoom lens having a variable magnification range of 2.6 to 2.9 or thereabout which is well corrected for high optical performance throughout the entire variable magnification range with the total length shortened, the zoom lens comprises, in order from the object side, a first lens unit of positive refractive power and a second lens unit of negative refractive power, the separation between both the first and second lens units being varied to vary magnification, wherein an aspheric surface layer is formed on a lens surface of the object side among the lenses made of glass in the second lens unit by coating that lens surface with transparent resin and then setting the transparent resin.

Abstract: An image forming lens system including a positive front lens group, a diaphragm, and a rear lens group, in this order from an object to be imaged. The front lens group is made of optical glass. The rear lens group is made of a single meniscus plastic lens having opposed aspherical lens surfaces with a concave surface adjacent to the diaphragm. The lens system satisfies the following relationships:f.sub.0 .multidot..vertline.1/f.sub.R-1 +1/f.sub.R-2 .vertline.<0.3-4<f.sub.0 /r.sub.R-1 <-0.7.DELTA.X.sub.R-1 /f.sub.0 <0.DELTA.X.sub.R-2 /f.sub.0 <00.1<d.sub.R /f.sub.0.In the above, f.sub.R-1 (=r.sub.R-1 /n-1) represents the focal length of the first surface of the plastic lens, f.sub.R-2 (=r.sub.R-2 /1-n) represents the focal length of the second surface of the plastic lens, f.sub.0 represents the focal length of the whole lens system, n represents the refractive index of the plastic lens at a reference wavelength, r.sub.

Abstract: The invention provides a photographic lens which uses a low-hygroscopicity resin lens component as a constitutional component, is made compact without incurring some expense, and enables the optical properties to be kept stable to an atmospheric humidity change. The photographic lens is of the single-focus or varifocallength type that comprises a plurality of lens components among which at least one or more lens components are resin lens components, wherein at least one of the resin lens components is formed of a low-hygroscopicity resin. For instance, the invention is applicable to a single-focus lens comprising four lens components, i.e., a positive meniscus lens component convex on the object side, a double-concave lens component, a double-convex lens component and a negative meniscus lens component convex on the image surface side.

Abstract: An optical system composed of two lens elements and a postpositional aperture stop, which are arranged in such a manner as to facilitate mounting on a casing of a camera or lens-equipped photographic film package and to suppress spherical aberration to ensure high quality performance from center to peripheral regions despite asymmetric lens disposition. The optical system includes, from the object side, a first lens element L.sub.1, a second lens element L.sub.2, and a postpositional aperture stop D located behind the second lens element on the side of the image field. The first lens element is a positive meniscus having a convex surface disposed on the object side, and the second lens element is a biconvex lens. Alternatively, the first lens element is a biconvex lens, and the second lens element is a positive meniscus having a convex surface disposed on the side of the image field. The image surface of the optical system is curved in a convace shape on the object side.

Abstract: In a negative first lens group composed of four sheets of lenses and a positive second lens group composed of four sheets of lenses, the lens in each lens group placed closest to the enlargement side is formed as a plastic lens having an aspheric surface, while predetermined conditional expressions are satisfied, whereby various kinds of aberration are made favorable and influence of changes in the plastic lens upon temperature is suppressed. A first lens group comprising a negative first lens (L1) made of a plastic lens having an aspheric surface, a negative second lens (L2), a negative third lens (L3), and a positive fourth lens (L4) and a second lens group comprising, a positive fifth lens (L5) made of a plastic lens having an aspheric surface, a negative sixth lens (L6), a positive seventh lens (L7), and a positive eighth lens (L8) are successively disposed from the enlargement side, while satisfying the following conditional expressions:-2.5<F.sub.1 /F.sub.5 <-0.3,-2.8<FG.sub.1 /FG.sub.2 <-1.

Abstract: A lens system comprises a stationary negative power singlet and a positive power singlet which is changed between two specific axial positions so as to yield a short focal length suitable for wide angle photography and a long focal length suitable for a tele-photography, respectively, and satisfies the following condition:-2.0<f1/f2<-1.7where f1 is the focal length of a first negative power singlet component, and f2 is the focal length of a second singlet component of positive power.

Abstract: An optical system of an optical information recording/reproducing apparatus includes a light source for emitting a generally parallel luminous flux. An objective optical system for converging the luminous flux emitted from the light source portion onto a medium is provided. The objective optical system can comprise a hologram lens or can have both surfaces formed as convex aspherical surfaces. A chromatic aberration correcting element having almost no power is adapted to correct chromatic aberration of the objective lens. A mechanism for independently actuating the objective lens at least in an optical axis direction is provided. Further, a beam splitter for splitting the luminous flux reflected by the medium from a light path directed to the light source portion and guiding the luminous flux to a light receiving system can be provided.

Abstract: In a scanning image forming lens used in an optical scanner, a light beam from a laser light source is coupled and deflected at an equal angular velocity by an optical deflector and is converged as a light spot on a scanned face by the scanning image forming lens to optically scan the scanned face at an equal speed. The scanning image forming lens is constructed by first and second plastic lenses such that the first lens is constructed by a positive meniscus lens having a concave face directed onto an optical deflector side. The second lens is arranged near a scanned face side of the first lens. At least one face of each of the first and second lenses is constructed by an aspherical surface. .vertline..theta..sub.1 /.theta..sub.2 .vertline. has a local minimum near an optical axis of the scanning image forming lens and is increased from the optical axis toward a peripheral portion of the scanning image forming lens when .theta..sub.

Abstract: This invention discloses an optical scanning apparatus which gives an F-.theta. function by means of an axis-symmetric aspherical lens serving as a scanning lens and facilitates the manufacture, assembly and adjustment of the lens by providing a cylindrical lens between a rotating polygon mirror and the axis-symmetric aspherical lens. According to this invention, two lenses which may be injection moulded and use plastic material form an optical scanning system. The cylindrical lens of these two lenses is located between the rotating polygon mirror and the scanning lens for image-forming light in the subscanning direction, the scanning lens of these two lenses is located between the cylindrical lens and the image formation plane for image-forming light in the mainscanning direction. Also, magnification of the mainscanning direction and that of the subscanning direction are independent.

Abstract: This invention relates to a simple, compact, and robust, cylindrical microlens external cavity for laser diode frequency control. The microlens system makes possible a tunable laser diode that utilizes an orthogonal pair of collimating microlenses to form a short external cavity for longitudinal mode and frequency control. The resulting system generates a circular, collimated beam of single frequency, tunable laser radiation. A cylindrical microlens collimator has a powered surface that semi-collimates (i.e., collimates in one axis only) the light from a laser diode. This powered surface is placed so as to be the surface closest to the laser facet. A second lens surface opposite the powered surface, is located in the semi-collimated beam is planar. The second surface of the lens is flat and has a reflective coating. Hence, it provides feedback that is refocused (in one axis) onto the laser aperture.

Abstract: An f.theta. lens system employing two f.theta. lenses in a laser scanning unit. According to the f.theta. lens system, a cheap plastic can be used for an f.theta. lens by lowering the refractive index of one of two f.theta. lenses and forming a toric face on one of total four refractive faces. Incident and emergent faces in the cross scan direction of a first f.theta. lens closer to a rotary polygon mirror has the curvature of .infin., and an incident face in the main scan direction of a second f.theta. lens closer to a photoconductive drum also has the curvature of .infin.. Thus, only an emergent face of the second f.theta. lens has a toric face.

Abstract: A photographic lens includes a first meniscus lens having a positive refracting power, a convex face of which is directed to a photographic object side, and includes a second meniscus lens having a positive refracting power, a concave face of which is directed to the photographic object side. The first and second lenses are arranged in this order from the photographic object side. The photographic lens is composed in such a manner that the following conditional expressions are satisfied:0.60<f/f.sub.1 <0.75-3.2<(r.sub.4 +r.sub.3)/(r.sub.4 -r.sub.3)<-2.5where f represents a focal length of the photographic lens, f.sub.1 represents a focal length of the first meniscus lens, r.sub.3 represents a radius of curvature of the concave surface facing the object side of the second meniscus lens and r.sub.4 represents a radius of curvature of a surface facing an image plane side of the second meniscus lens.