Abstract: New designs of optical devices, particularly for adding or dropping a selected wavelength or a group of wavelengths are disclosed. In one embodiment, an optical filter is positioned a distance from a first lens to form an assembly with a mechanical axis. The optical filter is configured at a selected wavelength and reflecting light beams at wavelengths other than the selected wavelength and transmitting a light beam at the selected wavelength. The distance is obtained with respect to a reflection measurement of a light beam at a wavelength other than the selected wavelength such that the reflection measurement is minimized. A second lens is initially positioned towards the optical filter. Before being fixed with respect to the assembly, the second lens is laterally shifted from the mechanical axis of the assembly to collect with a minimum loss a light beam refracted from the assembly. Such lateral shift also benefits when a light beam comes out from the second lens.

Abstract: A lightweight and homogeneous optical element exhibiting favorably weak birefringence and hygroscopicity as well as superior productivity and producing minimal chromatic aberrations is formed by using an organic-inorganic composite material having both the properties of a glass material and those of a plastic material. The optical element has at least one entrance refracting surface and at least one exit refracting surface. The optical element is formed from an organic-inorganic composite material having an inorganic phase dispersed in the three-dimensional network (matrix) of an organic phase.

Abstract: An optical system for optical communications is composed of a transparent material having a refractive index distribution formed by changing the molar ratio of metal oxide with valence of 2 or more. The metal oxide with valence of 2 or more includes, for example, Fe2O3. Using such an optical system for optical communications, optical communication components such as an optical fiber collimator and an optical isolator are composed.

Abstract: The planar lens of the invention having a flat glass substrate, in which a refractive index distribution is formed by diffusing a refractive index-increasing component into the flat glass substrate in a substantially hemispherical form or semicylinder form, wherein the refractive index-increasing component is silver, and the flat glass substrate comprises Li as an alkali metal that is subject to an ion exchange with the silver.

Abstract: The present invention provides a plastic lens, used in an optical system of an optical image recording apparatus, which is low in birefringence, and is less susceptible to displacement of focus caused by resistance to environment. At least a part of a non-effective area is concave, and there is a sink mark in the concave portion. The shape of the concave portion is determined so as to achieve a GI ratio (&Dgr;f/f0)≦5%.

Abstract: A thermally-shaped optical fiber and a method for forming the same so as to minimize the presence of optical artifacts in the optical fiber that contributes to insertion loss.

Abstract: Graded index lenses, methods, and devices are disclosed. In certain embodiments, he lenses are made from generally cylindrical glass members having a radially varying refractive index and have a pitch less than about 0.23. Other embodiments relate to graded index lenses having a pitch between about 0.23 and 0.25 and an index gradient less than or equal to 0.3.

Abstract: Graded index lenses, methods, and devices are disclosed. In certain embodiments, he lenses are made from generally cylindrical glass members having a radially varying refractive index and have a pitch less than about 0.23. Other embodiments relate to graded index lenses having a pitch between about 0.23 and 0.25 and an index gradient less than or equal to 0.3.

Abstract: A microlens has a material composition gradient that varies along the z-axis of the microlens to provide desired refractive properties in conjunction with the surface shape of the microlens. A method for designing the microlens may include defining a microlens surface shape, defining desired refraction properties of the microlens, and determining a refractive index gradient of the microlens in the direction of the z-axis using the desired refraction properties and the defined surface shape of the microlens. A method for fabricating the microlens may include depositing a material having a material composition gradient that is determined based on a lens shape and desired refractive parameters, and forming the microlens having the desired surface shape in the material.

Abstract: An optical microscope includes a compound GRIN objective and a lens system. The compound GRIN objective is able to form an image of an object located near one end of the GRIN objective. The compound GRIN objective is configured to limit a lateral field of view for the image to a distance equal to the diameter of the GRIN objective. The lens system is positioned to form a magnified image of an image formed by the compound GRIN objective.

Abstract: A graded optical element is provided that includes graded layers of optical material, wherein the layers may or may not have different indexes of refraction. A method for making such a graded thickness optical element is also provided. A masking layer is preferably spaced above a substrate, where the masking layer has at least one aperture therein. Optical material is then deposited on the substrate through the aperture in the masking layer to form a layer of refr material that extends laterally beyond the aperture in the masking layer in at least one region.

Abstract: A graded optical element is provided that includes graded layers of optical material, wherein the layers may or may not have different indexes of refraction. A method for making such a graded thickness optical element is also provided. A masking layer is preferably spaced above a substrate, where the masking layer has at least one aperture therein. Optical material is then deposited on the substrate through the aperture in the masking layer to form a layer of refr material that extends laterally beyond the aperture in the masking layer in at least one region.

Abstract: A graded index lens is obtained by treating a raw glass material having a rod shape by ion exchange using silver to form a refractive index distribution in the radial direction of the rod, wherein the raw glass material comprises a glass composition of the following components: 15<Na2O≦30 mol %; 10<Al2O3≦25 mol %; 27.5≦SiO2≦55 mol %; 3≦B2O3≦18 mol %; 2.5≦MgO≦18 mol %; 0≦Ta2O5≦5 mol %; 0≦La2O3≦3 mol %; 0≦BaO≦3 mol %; and 0≦ZrO2≦3 mol %.

Abstract: In an objective lens for use in an optical pickup device, when NA1 and N2 (NA2 <NA1) represent a needed numerical aperture of the objective lens on an image side, a first spot and a second spot represent a spot formed by the light flux having passed through the central region, a mth order diffracted ray and a nth diffracted ray represent a diffracted ray having the maximum diffraction efficiency among diffracted rays, the central region nearly corresponds to a region through which the light flux in the inside of the numerical aperture NA2 passes, the light amount of the nth order diffracted ray which reaches the inside of the second spot is less than that of the mth order diffracted ray which reaches the inside of the first spot, and the mth order diffracted ray and the nth order diffracted ray satisfy the relationship of m=n.

Abstract: A method of producing a collimator or collimator array is constituted by the steps of: fixing long-size gradient index rod lens raw materials on a substrate having end surfaces each forming a plane so that the long-size gradient index rod lens raw materials are arranged side by side at intervals of the predetermined pitch while optical axes of the gradient index rod lens raw materials are parallel to one of the end surfaces of the substrate cutting the substrate provided with the gradient index rod lens raw materials at a predetermined position in a plane perpendicular to the optical axes of the gradient index rod lens raw materials to thereby divide the substrate provided with the gradient index rod lens raw materials into lens array parts; adjusting the divided lens array parts so that each of the gradient index rod lens raw materials in the lens array parts has a defined lens length; and arranging the lens array parts so that the cut end surfaces of the lens array parts are made to face each other while op

Abstract: A fiber collimator is provided, comprising at least two optical components, one of the optical components (e.g., an optical element such as a collimating lens or a plano-plano pellet) having a surface that has a comparatively larger cross-sectional area than the surface of the other optical component(s) (e.g., at least one optical fiber). The optical components are joined together by fusion-splicing, using a laser. A gradient in the index of refraction is provided in at least that portion of the surface of the optical element to which the optical fiber(s) is fusion-spliced or at the tip of the optical fiber. The gradient is either formed prior to or during the fusion-splicing. Back-reflection is minimized, pointing accuracy is improved, and power handling ability is increased.

Abstract: The transparent article with radial gradient index, according to the invention, comprises a matrix made of a first transparent polymer having a first refractive index n1 and a first Abbe number &ngr;1, a second transparent polymer, diffused into the first polymer in order to produce the radial gradient index and having a second refractive index n2, different than the first refractive index, and a second Abbe number &ngr;2, characterized in that it furthermore comprises an effective amount of an Abbe number modifier agent which reduces by at least 10%, preferably by at least 15%, and more preferably by at least 20%, the value of the Abbe number of that of the first or second polymer which has the refractive index with lower value.

Abstract: An optical system comprising a radial type gradient index lens element which has a negative refractive power of medium and a negative refractive power as a whole, and a radial type gradient index lens element which has a negative refractive power of medium and a negative refractive power as a whole; the optical system having favorable imaging performance: and an optical module using the optical system which is suited for stereoscopic photography and automatic focusing.

Abstract: A radial gradient contact lens is provided. The methodology described above allows the parameters of the lens and of the radial gradient profile to be chosen to improve the vision and the comfort of the wearer. The lens can be made thinner and the optical performance remains improved as the CL moves around in the eye. The improved vision leads to higher contrast when the iris of the eye is fully open as it is under low light level conditions. The use of an anamorphic lens consisting of an elliptical index profile for use in correcting astigmatism is described.

Abstract: An excellent axial refractive index distributed lens is disclosed, which has a refractive index distribution required for an optical design, high durability, and high quality (a low melting temperature) and is obtained, by an ion exchange method using silver, from a glass material having the following composition:10 <Na.sub.2 O.ltoreq.25 mol %8 <A1.sub.2 O.sub.3 .ltoreq.25 mol %0 .ltoreq.MgO.ltoreq.18 mol %0 .ltoreq.ZnO.ltoreq.18 mol %3 .ltoreq.B.sub.2 O.sub.3 .ltoreq.18 mol %35 .ltoreq.SiO.sub.2 .ltoreq.55 mol %0 .ltoreq.La.sub.2 O.sub.3 .ltoreq.5 mol %0 .ltoreq.BaO.ltoreq.5 mol %0 .ltoreq.Ta.sub.2 O.sub.5 .ltoreq.3 mol %0 .ltoreq.ZrO.sub.2 .ltoreq.3 mol %provided that2.5 .ltoreq.MgO+ZnO.ltoreq.18 mol %.The glass composition constituting the glass material has an ion exchange rate sufficient for practical use and is capable of allowing silver ions to be stably present therein.

Abstract: A gradient index lens has a base lens and a resin layer. The resin layer is formed on a surface of the base lens. The resin layer has an aspherical surface. The base lens has a gradient index.

Abstract: In a rod lens array in which a plurality of rod lenses each having a refractive-index distribution in the radial direction are arranged in one row such that the optical axes are parallel to each other, and in a life-size imaging optical apparatus using the rod lens array, the outside diameter of each rod lens is such that 0.05 mm.ltoreq.R.ltoreq.0.25 mm and 0.5R.ltoreq.r.sub.0 .ltoreq.1.0R (2R: the distance between the optical axes of adjacent rod lenses and r.sub.0 : the radius of the effective area of each rod lens that provides a lens action) and the degree of overlap m defined by m=x.sub.0 /2R is such that 1.61.ltoreq.m.ltoreq.1.80 or 2.06.ltoreq.m.ltoreq.2.50 where X.sub.0 is the view radius of a single rod lens which is given by X.sub.0 =-r.sub.0 /cos(Z.sub.0 .pi./P).

Abstract: A segmented GRIN anamorphic lens and a lens array using such lenses are provided. The lens has an optical axis and is composed of a plurality of segments. The interfaces between the segments are planes or wedges inclined at an angle to the optical axis. At least one segment has a predetermined axial index of refraction profile while the other segment may have either a predetermined homogeneous index of refraction or a predetermined radial index of refraction profile. The planar interface geometry and the index of refraction profiles are chosen to provide lenses with desirable optical properties. Spherical and cylindrical aberrations can be reduced or eliminated by appropriate choice of the index of refraction profile. The front and rear surfaces of the lens assembly can also be ground and polished into spherical shapes which act with the axial gradient interface to yield an anamorphic lens functionality.

Abstract: An optical coupler is provided that comprises a single lens component, comprising two axially-graded index of refraction elements, each having a low refractive index surface and a high refractive index surface and joined along their respective high refractive index surfaces. As configured, the optical coupler is useful as a solar concentrator for concentrating solar radiation onto a solar cell or other solar-receptive medium.

Abstract: An optical product such as an optical lens, or semi-finished lens blank is provided comprising a composite of at least three different and separately applied layers, each layer having a different refractive index which allow for a progressive multifocal lens having a wide and natural progression of vision when looking from far to near. In addition, a method is provided for simply, quickly and inexpensively manufacturing a composite refractive gradient progressive multifocal lens. A transition zone disposed between a base and an outer layer includes a distinct and separately applied transition layer or layers having an effective refractive index which is intermediate between the refractive indices of the base and outer layers, and preferably approximates the geometric mean of the refractive indices of the base and outer layers. This transition zone may include multiple transition layers, with each transition layer having a different and distinct refractive index.

Abstract: An optical coupler is provided that comprises one lens component, comprising at least one axially-graded index of refraction element. When the optical coupler component includes one axially-graded index of refraction element, a homogeneous "boot" element is cemented on entrance surface to provide plano-plano coupling. When the optical coupler includes two or more axially-graded index of refraction elements, both entrance and exit surfaces are planar. The optical coupler component may be sized to provide focusing at its exit surface. The axially graded index-based couplers of the present invention comprise a single component, thereby reducing the number of components and the concomitant complexity of the optical system. Further, many of these couplers can be fabricated with plano-plano entrance-exit surfaces, thereby obviating the need for forming curved focusing surfaces and thus avoiding the introduction of air spaces.

Abstract: An axially-based lens is provided, comprising two biaxial elements, each having entrance and exit surfaces. The exit surface of one of the elements is joined to the entrance surface of the other element, with one of the elements rotated at an angle with respect to the other. In a preferred embodiment, the angle of rotation is 90.degree.. The axially-based lens thus comprises four axial sub-elements, and is called a "quadaxial" lens herein. The axially-based lens element has the ability to gather and focus light to a spot with a minimum of spherical aberration and with a substantially uniform distribution of light intensity from center to periphery of the spot. In a preferred embodiment, the lens element focuses light to a square spot size.

Abstract: A segmented axial gradient array lens is provided. In one embodiment, the segmented array lens includes two sheets of optical material which mate at opposing faces which have a series of corresponding parallel grooves and ridges. At least one of the sheets has an axial gradient index of refraction profile. This provides the functionality of a series of parallel cylindrical lenses. The array lenses may include one or more additional intermediate sheets which may have a homogeneous or axial gradient index. With the first and last sheets having an axial gradient index of refraction, and the grooves forming the first and last interfaces between the sheets being rotated 90 degrees relative to each other, a two dimensional array of point foci can be provided. An array of cones and conical indentations can be used at the interfaces to provide the functionality of an array of spherical lenses. An array lens of the invention can be used to provide an optical multiplexer.

Abstract: An optical system for a compound camera includes an equivalent image plane provided at a position substantially optically equivalent to an image plane of the photographing lens system. A condenser lens is provided proximate to the equivalent image plane and a relay lens system is provided behind the condenser lens to form an image of the photographing lens system on an image pickup device. The relay lens system satisfies the requirements defined by -0.1<P<0.09, and S3<0, where P designates the Petzval sum of the whole relay lens system when the focal length of the relay lens system is assumed to be 1.0, and S3 designates the astigmatism coefficient of the whole relay lens system when the focal length thereof is assumed to be 1.0, respectively.

Abstract: A birefringent element is patterned such that for light of a first polarisation the element acts as a first refractive optical element and for light of a second polarisation the optical response of the element changes. The element can be used in conjunction with a polarisation selecting means, such as a liquid crystal device, to provide an electrically controllable optical element that can be used in light beam manipulation applications.

Abstract: Axial gradient index of refraction lens elements are used in a lens system, for instance for a photographic objective lens, to correct monochromatic and chromatic lens aberrations, thereby reducing the number of lens elements required to achieve good optical performance in the overall lens design compared to for instance a lens system using aspheric lenses. The gradient index (GRIN) lens elements are bi-convex and/or meniscus type lens elements. The large refractive index gradients as well as large dispersion value gradients provide aberration correction in the overall lens system. A high aperture ratio lens system uses six lens elements where the first and last lens elements are positive power lens elements having refractive index and/or dispersion gradients along the optical axis.

Abstract: A lens element (40) is formed from a monolithic unit (46) having two sections (46A and 46B) aligned on an optical axis. A selected one of the sections has an axial gradient refractive index, and the other has a homogeneous refractive index. A first surface 42 is generated one section and a second surface is generated on the other. The axial gradient index material may be selected such that third order spherical aberration of the element is zero. The axial gradient index material may be selected such that similarly constructed elements having shape factors between about 0 and 2.0 also have zero third order spherical aberration. Another element (20) may be formed entirely from an axially graded refractive index material. The refractive index preferably varies as a non-linear function of at least distance along the optical axis. The refractive index function and index change may be selected such that a selected third order aberration is zero or some constant value over a wide range of shape factor.

Abstract: A zoom lens system comprises in the following order from the object side: a first lens group of a positive refracting power; a second lens group of a negative refracting power; a third lens group; and a fourth lens group of a positive refracting power, wherein, when changing a focal length of the zoom lens system from a wide-angle end to a telephoto end, the second lens group is shifted in one direction along an optical axis of the zoom lens from the object side toward the image side, the third lens group is shifted so as to reciprocate along the optical axis, and the first lens group has a gradient index lens whose refractive index varies along the direction of the optical axis and which satisfies the following condition:-10.6<(.nu.2-.nu.1)/[(n2-n1).multidot.100]<-0.9whereinn1: a refractive index at an object-side vertex of the gradient index lens,n2: a refractive index at an image-side vertex of the gradient index lens,.nu.1: Abbe number at the object-side vertex of the gradient index lens,.nu.

Abstract: In an optical system, a lens array comprises a plurality of gradient index lenses arranged in a plurality of rows. The lens array is aligned with an image bar having a plurality of pixel rows in such a manner that each pixel row in the image bar is symmetrically arranged with respect to lens rows having fields of view encompassing the pixel row.

Abstract: A wide-angle lens system comprising, in order from the object side, a front unit, a stop and a rear unit: the front unit comprising, in order from the object side, a first lens unit which comprises a plurality of lens components including a positive lens component and has a negative refractive power as a whole, a negative lens component having a concave surface on the object side and a cemented lens component; and the rear unit comprising a negative lens component disposed on the side of the stop and at least two positive lens components. This wide-angle lens system has sufficiently corrected aberrations, in particular, negative distortion, curvature of field and sagittal coma.

Abstract: A segmented axial gradient lens and a lens system using such lenses are provided. The lens has an optical axis and is composed of a plurality of segments. The interfaces between the segments are either planes inclined at an angle to the optical axis, wedges or cones. At least one segment has a predetermined axial index of refraction profile while other segments may have either a predetermined homogeneous index of refraction or a predetermined axial index of refraction profile. The interface geometry and the index of refraction profiles are chosen to provide lenses with desirable optical properties from segments having only simple interfaces. Spherical and cylindrical aberrations can be reduced or eliminated by appropriate choice of the index of refraction profile even for a lens fabricated entirely from segments with flat surfaces. The front and rear surfaces of the lens assembly can also be ground and polished into spherical or cylindrical shapes.

Abstract: A two-wavelength antireflection film includes a substrate and an alternate film. The alternate film consists of alternately laminated layers of a low refractive index material and an intermediate refractive index material, in order from a light entrance side to the surface of the substrate. The low refractive index material is at least a member selected from the group consisting of MgF.sub.2, SiO.sub.2, BaF.sub.2, LiF, SrF.sub.2, AlF.sub.3, NaF, a mixture thereof and a compound thereof. The intermediate refractive index material is at least a member selected from the group consisting of Al.sub.2 O.sub.3, LaF.sub.3, NdF.sub.3, YF.sub.3, a mixture thereof and a compound thereof.

Abstract: A fused glass block having an axial gradient index of refraction profile between two opposed parallel surfaces, with a change in refractive index from one of the surfaces to the other ranging from about 0.04 to 0.47, is provided. The fused glass block has a change in thermal expansion coefficient from one of the surfaces to the other of less than about 3.times.10.sup.-7 .degree. C..sup.-1, has essentially no strain or birefringence therein, and has a smoothly varying refractive index profile from one of the surfaces to the other. The fused glass block is prepared from at least two pre-selected compositions of a lead-silicate glass series that has been discovered to provide the requisite properties.

Abstract: A fused glass block having an axial gradient index of refraction profile between two opposed parallel surfaces, with a change in refractive index from one of the surfaces to the other ranging from about 0.04 to 0.47, is provided. The fused glass block has a change in thermal expansion coefficient from one of the surfaces to the other of less than about 3.times.10.sup.-7 .degree.C..sup.-1, has essentially no strain or birefringence therein, and has a smoothly varying refractive index profile from one of the surfaces to the other. The fused glass block is prepared from at least two pre-selected compositions of a lead-silicate glass series that has been discovered to provide the requisite properties.

Abstract: In accordance with the invention, a mode-field transforming waveguide region comprise an elongated glass core surrounded by glass cladding wherein the normalized index differential between the cladding and the core (termed .DELTA.) varies along the length. Preferably the waveguide comprises an optical fiber having a hydrogen-loaded germanosilicate core. The variation of .DELTA. as a function of longitudinal distance can be effected by exposing the fiber to ultraviolet light and varying the dosage of exposure as a function of longitudinal distance.

Abstract: A projection TV lens (60) includes first (64), second (66), third (70), and fourth (72) element-groups counted in numerical order and arranged on a common optical axis (62). The first, third, and fourth groups each include at least one lens element. The first and third group has positive power and the fourth group has negative power. The second group includes a first lens element (67) having negative power and having a graded refractive index.

Abstract: A gradient index optical element has at least one first metal dopant selected from the group consisting of La, Y, Ga, In, Ge, Sn, Zn, Zr, Ba, Ca, As, Sr, Gd and Be distributed at a concentration gradient in a glass medium. The concentration gradient of the first metal dopant defines a slope having a direction. At least one second metal dopant different from the first metal dopant and selected from the group consisting of Bi, Sb, Nb, Ti, Ta, Pb, Tl, Zr, In, Sn, Y, Ba, Ca and Sr is distributed at a concentration gradient in the glass medium. The concentration gradient of the second metal dopant defines a slope smaller than the slope of the concentration gradient of the first metal dopant. The slope of the concentration gradient of the second metal dopant is in the same direction as the slope of the concentration gradient of the first metal dopant.

Abstract: A spherical recess is provided to one end wall of a first planar lens and the opposite end walls of a second planar lens, the first planar lens having a thicknesswise index distribution in the vicinity of the one end wall whereas the second planar lens has a thicknesswise index distribution in the vicinity of each of the opposite end walls. A high refractive index homogeneous sphere lens is sandwiched between the first planar lens and the second planar lens to be brought into contact with the spherical recesses. A homogeneous semi-sphere lens is held to contact the other spherical recess of the second planar lens. The homogeneous sphere lens side first planar lens and second planar lens of the first planar lens and second planer lens increase in refractive index toward the homogeneous sphere lens so that the sphere lens is corrected in spherical aberration, and so that distribution gradient of the refractive index is selected for correcting the sphere lens in coma.

Abstract: Methods of making gradient property refractive elements such as gradient index lens blanks. The spatial distributions of constituents achieved by subjecting various starting assemblages to various diffusion conditions are predicted. Each such predicted spatial distribution of constituents is converted to a spatial distribution of the graded property. The property distribution which best approximates a desired distribution is selected, to thereby select one starting assemblage and one set of diffusion conditions. That assemblage and set of conditions are used in fabrication of the element.

Abstract: A method of manufacturing a multimode optical transmission medium from a synthetic resin having the distribution of refractive index varying continuously in a fixed direction. In the method, the polymerization is caused to proceed utilizing the effect of diffusion or exclusion of a monomer in the gel formed at the polymerization initiating terminal. Therefore, this method is free from the defects of methods using conventional polymerization reactions, and has an extremely high productivity.

Abstract: A high performance objective lens system for microscopes comprising a plurality but a very small number of lens elements at least one of which is designed as an axial GRIN lens element.

Abstract: A one-dimensional semiconductor laser array assembly typically comprising a one-dimensional semiconductor laser array, a heatsink upon which the laser array is bonded, and a lens assembly. The one-dimensional semiconductor laser array consists of a plurality of emitters with each emitter electrically connected in parallel to a power supply. The bonding agent, typically silver epoxy, must be of a uniform thickness so that the laser array is aligned properly upon the heatsink. The lens assembly is typically comprised of a refractive lens, typically of a bi-convex design, and a one-dimensional array of binary optical elements. The one-dimensional array of binary optical elements is designed such that each element has a front surface having a binary optic diffractive element etched thereon. The refractive lens and the one-dimensional array of binary optical elements are aligned and held in place by means of ears protruding from the heatsink.

Abstract: Tailored glass bodies (10) having a substantial change in index of refraction (a .DELTA.n of at least about 0.08 along an axis) are provided. The glass body is characterized by two substantially parallel surfaces, with one surface having a first composition (12t) and the other surface a second composition (12b). The composition of the glass body varies in some predetermined fashion between the two surfaces (12i1-12i8) to provide a predetermined graded index of refraction. A method is also provided to tailor the glass body so that the two compositions have one or more of the following properties substantially constant: thermal coefficient of expansion, glass fusion temperature, Abbe value, and density.

Abstract: A gradient index optical element includes a first metal which is at least one kind of metal selected from the metals of Group A each having the content of 10-40 mol % in terms of oxide and a second metal which is at least one kind of metal selected from the metals of Group B each having the content of 2-15 mol % in terms of oxide, in which the first and second metals are distributed so that the concentration of one of said first and second metals increases from the center of the optical element toward the periphery and that of the other decreases. Hence, the gradient index optical element has an important advantage in practical use that the correction for chromatic aberration is excellent, that is, the Abbe's number increases as the refractive index becomes great.

Abstract: Riflescope arrangement includes a tube containing an eye piece section fowed by a relay section which is followed by an objective section. The eye piece, relay and objective sections lie along and are aligned with the optical axis of the riflescope. The front optical element of the objective section is in the form of an axial gradient index element to add a degree of freedom for chromatic and other corrections, without adding an extra element or weight to the riflescope.