Abstract: An ocular optical system configured to allow imaging rays from a display image to enter an observer's eye through the ocular optical system so as to form an image is provided. A direction toward the eye is an eye side, and a direction toward the display image is a display side. The ocular optical system sequentially includes a first and a second lens elements having refracting power from the eye side to the display side along an optical axis. Each lens element includes an eye-side surface and a display-side surface. An optical axis region of a display-side surface of the first lens element is convex. The display-side surface of the first lens element is a Fresnel surface. An optical axis region or a periphery region of a display-side surface of the second lens element is convex.

Abstract: Disclosed is an eyepiece optical system with a large field-of-view angle, and a head-mounted display apparatus. The eyepiece optical system comprises a first lens group (G1) and a second lens group (G2) which are arranged coaxially and successively along an optical axis from a human eye to an image source and meet a certain focal length relationship. A distance (D12) between the first lens (L1) and the second lens (L2), a focal length relationship of lenses within the second lens group (G2) and the material properties of various lenses meet a certain relationship. The eyepiece optical system has the advantages of large aperture, large field-of-view, high resolution, low distortion, and small size, etc., and is suitable for a head-mounted display and similar apparatuses.

Abstract: The invention provides an ocular lens well corrected for aberrations through a sufficiently large angle of view and having a sufficient eye relief while ensuring avoidance of increasing the overall length and suppression of an increase in lens diameter, and provides an optical device including this ocular lens. An ocular lens 3 includes, in order from an object side, a first lens group G1 including a first lens component G1A in meniscus form having a convex surface facing the object side, a second lens group G2 including a lens component L21 having a convex surface facing a viewing eye side, and a third lens group G3 having a positive refractive power. An object-side focal plane I of the third lens group G3 is positioned between the second lens group G2 and the third lens group G3.

Abstract: An eyepiece lens includes: a first lens having positive refractive power, the first lens having a convex surface that faces toward an eye point side; and a second lens having positive refractive power, the second lens having a convex surface that faces toward the eye point side. The first and second lenses are arranged in order from the eye point side. Following conditional expressions are satisfied, 3.0>(h×?)1/2/E>1.2??(1) 2.3>(L?E)/h>1.5??(2) where h is a height of the image at a horizontal end, ? is a half angle of view in a horizontal direction, E is a distance from an eye point to the first lens, the distance being an eye relief, and L is a distance from the eye point to the image.

Abstract: A finder optical system includes an erecting optical system, an eyepiece optical system, and a light metering optical system. An optical axis of the light metering optical system is non-parallel to an optical axis of the eyepiece optical system. The light metering optical system includes a first lens having positive refractive power and a second lens having negative refractive power in this order from a side of the erecting optical system to a side of an image sensor, and the second lens is a prism body reflecting a light flux incoming from an incident surface off an inner reflection surface and outputting the light flux from a light outputting surface.

Abstract: An ocular lens used in an optical apparatus, such as a telescope optical system, includes the following lens groups sequentially arranged from the object side: a first lens group G1 having negative refracting power; a second lens group G2 including a lens component having a convex surface facing the viewer's eye side; and a third lens group G3 having positive refracting power. An object-side focal plane of the third lens group G3 is located between the second lens group G2 and the third lens group G3. The first lens group G1 includes the following lens components sequentially arranged from the object side: a first lens component G1A having a convex surface facing the object side, having negative refracting power, and having a meniscus shape; and a second lens component G1B having negative refracting power.

Abstract: The invention provides a zoom optical system comprising at least three lens groups and designed to implement zooming by varying a separation between the respective lens groups. The zoom optical system includes, on an image plane side with respect to a stop, a lens group comprising a plurality of lenses and having positive refracting power throughout. The lens group having positive refracting power includes therein a first lens and a second lens in order from the object side, an image plane side surface of the first lens being convex toward the object side, and an object side surface of the second lens being concave toward the object side.

Abstract: A fixed-focus lens module includes an outer lens barrel, an inner lens, a first lens, and a second lens group. The outer lens barrel includes a first open end, a first cavity, and a second open end arranged in the order from the object side to the image side of the outer lens barrel. The inner lens barrel is received in the outer lens barrel adjacent to the first open end. The first lens is received in the inner lens barrel. The second lens group is received in the outer lens barrel adjacent to the second open end. An gap is defined between an outer wall of the inner lens barrel and an inner wall of the outer lens barrel at the first open end, and the center axis of the inner lens barrel is adjustable relative to the outer lens barrel for adjusting the alignment between the first lens and the second lens group.

Abstract: An imaging lens system with two lenses is provided. The imaging lens system with two lenses, along an optical axis from an object side to an image side, comprises an aperture stop; a first lens having positive refractive power and being a biconvex lens; and a second lens having negative refractive power and being a meniscus lens with a concave surface on the object side and a convex surface on the image side.

Abstract: The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The viewing optical system comprises, in order from the viewing plane side, a cemented lens and a positive lens component, and satisfies the following condition (1). 0.2<Dm/L<0.8??(1) where Dm is the widest of lens-to-lens spaces in the viewing optical system, and L is a distance of said viewing plane to a lens surface positioned in the viewing optical system and nearest to the eye point side.

Abstract: A fixed-focus lens disposed between a magnified side and a minified side. The fixed-focus lens has an optical axis and includes a reflective system and a refractive system. The reflective system includes a reflection mirror with a negative refractive power. The refractive system is disposed between the reflection mirror and the minified side and includes a first lens group and a second lens group. The first lens group has a positive refractive power. The second lens group is disposed between the first lens group and the minified side, and has a positive refractive power. The fixed-focus lens satisfies F/H>0.23, where F is an effective focal length and H is an image height.

Abstract: To provide an aberration correction configuration that can realize both an aberration correction function for a long focus and an aberration correction function for a short focus. While having a conventional aberration correction apparatus configuration that has two rotationally symmetric lenses arranged between two multipole lenses, three rotationally symmetric lenses are disposed between an objective lens and a multipole lens instead of the conventional arrangement in which two rotationally symmetric lenses are disposed therebetween. When using the objective lens with a long focal length, aberrations are corrected using two rotationally symmetric lenses among three rotationally symmetric lenses disposed between the objective lens and the multipole lens. When using the objective lens with a short focal length, e.g.

Abstract: The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The viewing optical system comprises, in order from the viewing plane side, a cemented lens in which at least one negative lens and at least one positive lens are cemented together and one positive lens, and satisfies the following condition (1). ?8<r3/f<?0.2??(1) Here r3 is the radius of curvature of the lens surface positioned in the cemented lens and nearest to the viewing plane side, and f is the focal length of the whole viewing optical system.

Abstract: The invention relates to an eyepiece optical system that, albeit being of small size, works in favor of gaining an angle of field and optical performance, and an electronic view finder incorporating such an eyepiece optical system. Specifically, the invention is characterized by comprising, in order from an object side to an exit side thereof, a first lens group that is a single lens that has positive refracting power and is in a meniscus configuration concave on its object side, a second lens group that is a single lens that has negative refracting power and is in a meniscus configuration concave on its object side, and a third lens group that is a single lens that has positive refracting power, wherein an object-side concave lens surface in the first lens group is an aspheric surface, an object-side concave lens surface in the second lens group is an aspheric surface, and an exit-side lens surface in the third lens group is an aspheric surface.

Abstract: A lens system includes a first lens axially aligned with a second lens, where the first and second lenses are configured to be sequentially positioned from a pupil image of a viewer. The second lens is formed as a triplet having three cemented elements. The second lens includes a convex surface facing the first lens, and a flat surface opposing the convex surface of the second lens. The first lens includes a concave surface opposing a flat surface of the first lens; the second lens includes a concave surface and a convex surface; and the concave surface of the first lens and the concave and convex surfaces of the second lens have equal radii of curvatures.

Abstract: An image forming lens has a configuration that an image forming lens IL for receiving parallel beams of light emitted from an observation target object and emerging from an infinity-designed objective lens of a microscope and forming an image of the observation target object in a predetermined position, is constructed of, in order from an object side, a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power, and the first lens group is constructed of a positive lens (e.g., a biconvex lens L1) and a negative lens (e.g., a negative meniscus lens L2).

Abstract: A lens system includes a first lens axially aligned with a second lens, where the first and second lenses are configured to be sequentially positioned from a pupil image of a viewer. The second lens is formed as a triplet having three cemented elements. The second lens includes a convex surface facing the first lens, and a flat surface opposing the convex surface of the second lens. The first lens includes a concave surface opposing a flat surface of the first lens; the second lens includes a concave surface and a convex surface; and the concave surface of the first lens and the concave and convex surfaces of the second lens have equal radii of curvatures.

Abstract: An eye piece (EL1) is formed having a first lens (L1) having a positive refractive power and a second lens (L2) having a positive refractive power, which are disposed in order from an object (O), and a contact multi-layer diffractive optical element (DOE), which has a first optical element (51) formed with a relief pattern and a second optical element (52) which is in contact with the surface of the first optical element (51) where the relief pattern is formed, is disposed on an optical surface of the first lens (L1) or the second lens (L2).

Abstract: The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The viewing optical system comprises, in order from the viewing plane side, a cemented lens and a positive lens component, and satisfies the following condition (1). 0.2<Dm/L<0.8??(1) where Dm is the widest of lens-to-lens spaces in the viewing optical system, and L is a distance of said viewing plane to a lens surface positioned in the viewing optical system and nearest to the eye point side.

Abstract: The invention provides a viewing optical system positioned between a viewing plane as a virtual plane and an eye point. The viewing optical system comprises, in order from the viewing plane side, a first lens and a filter.

Abstract: The invention relates to an image pickup system comprising an electronic view finder suitable for achieving compactness and having a sufficient viewing angle of field and satisfactory optical performance. The image pickup system comprises an image pickup device, an image display device for displaying an image, a controller for converting image formation obtained from the image pickup device into a signal that enables the image information to be formed on the image display device, and a viewing optical system for guiding an image displayed on the display device to a viewer's eye. The viewing optical system comprises at least three lenses.

Abstract: The invention relates to an image pickup system comprising an electronic view finder suitable for achieving compactness and having a sufficient viewing angle of field and satisfactory optical performance. The image pickup system comprises an image pickup device, an image display device for displaying an image, a controller for converting image formation obtained from the image pickup device into a signal that enables the image information to be formed on the image display device, and a viewing optical system for guiding an image displayed on the display device to a viewer's eye. The viewing optical system comprises at least three lenses.

Abstract: The invention relates to an image pickup system comprising an electronic view finder suitable for achieving compactness and having a sufficient viewing angle of field and satisfactory optical performance. The image pickup system comprises an image pickup device, an image display device for displaying an image, a controller for converting image formation obtained from the image pickup device into a signal that enables the image information to be formed on the image display device, and a viewing optical system for guiding an image displayed on the display device to a viewers eye. The viewing optical system comprises at least three lenses.

Abstract: The invention relates to an image pickup system comprising an electronic view finder suitable for achieving compactness and having a sufficient viewing angle of field and satisfactory optical performance. The image pickup system comprises an image pickup device, an image display device for displaying an image, a controller for converting image formation obtained from the image pickup device into a signal that enables the image information to be formed on the image display device, and a viewing optical system for guiding an image displayed on the display device to a viewer's eye. The viewing optical system comprises at least three lenses.

Abstract: The invention relates to an imaging system equipped with an electronic viewfinder suitable for compactness and having a sufficient angle of viewing field and satisfactory optical performance, especially the ability to prevent harmful light. The imaging system comprises an image pickup optical system, an image pickup device for receiving a light beam guided by the image pickup optical system, an image display device for displaying an image thereon, a controller for converting image information obtained from the image pickup device into signals capable of being displayed on the image display device, and a viewing optical system for guiding an image appearing on the image display device to a viewer's eye. The viewing optical system comprises, in order from an image display device side, one negative lens and one positive lens.

Abstract: In one form, an imaging system comprises an imager that forms an image of an object in a field of view, a rotationally symmetric lens assembly disposed between the imager and the object, and an equalizer. The rotationally symmetric lens assembly provides increased collection efficiency for a given depth of field, whereby the rotationally symmetric lens assembly causes aberration, compared to a well-focused lens. The rotationally symmetric lens assembly comprises a front negative lens, a rear positive lens, and an aperture positioned between the front and rear lenses. The equalizer, which is connected to the imager, receives image data and at least partially compensates for the aberration caused by the rotationally symmetric lens assembly.

Abstract: A viewfinder of a small size and a small thickness is implemented to achieve a miniaturization and reduction in thickness of an image pickup apparatus. The viewfinder includes an eyepiece system for expanding an image displayed on an image display element so as to be visually observed. The eyepiece includes a first single lens disposed adjacent to the image display element and having a negative refractive power and a second single lens disposed remotely from the image display element and having a positive refractive power. A reflecting member is disposed between the first single lens and the second single lens for diverting an optical axis to a predetermined direction.

Abstract: The present invention relates to an optical device having a structure that can make the diameter of the emitted Gaussian beam smaller. The optical device is arranged between a first and second positions, and comprises a first and second optical systems separated with a focus on an intermediate position between the first and second positions. The first optical system, arranged between the first and intermediate positions, comprises a first light entrance surface on which a Gaussian beam having a beam waist, whose radius becomes w0 at the first position, is incident, and a first light emission surface from which a Gaussian beam having a beam waist, whose radius becomes w1 at the intermediate position, is emitted.

Abstract: A system and method of providing a micromirror pixel 400 that is highly resistant to bright failure states. The micromirror 400 uses an asymmetric yoke 402 to ensure the mirror is only attracted to the address electrode in one rotation direction. The landing mechanism on the other side of the torsion binge axis also is altered to allow the pixel to over rotate in the “off” direction. The over rotation ensures that light reflected by the mirror when in the off direction will miss the projection lens pupil, allowing the corresponding pixel to remain dark in both an operational and failed state.

Abstract: An observation optical system of the present invention comprises an image erect optical system and an eyepiece optical system for observing an object image. The eyepiece optical system comprises a positive single lens having double convex surfaces and a negative meniscus lens having a concave surface directed toward eye point side, and the following condition is satisfied: 0<S<0.3 0.05<d1/f<0.15 where S=(r1?r2)/(r1+r2), r1 is a curvature radius of the object image side surface of the negative meniscus lens, r2 is a curvature radius of the eye point side surface of the negative meniscus lens, d1 is a distance of air space between the positive single lens and the negative meniscus lens, which represents a distance of air space when diopter of the observation optical system is adjusted to be ?0.8 (m?1) if the air space is changed, and f is a focal length of the eyepiece optical system.

Abstract: An optical system for use in a head-mounted display is provided which includes a microdisplay (4) and a magnifier (10) for producing a magnified image of the microdisplay for viewing by a human eye. The magnifier (10) includes a diffractive surface and has in order: a first element (1) having a first surface (S1) which is convex in the direction of the long conjugate, a block (3) of optical material, and a second element (2) having a second surface (S2) which is convex in the direction of the short conjugate. The first surface (S1) is preferably the diffractive surface. The magnifier provides a long eye relief, a large exit pupil, and a large field of view with a minimum of components.

Abstract: The invention relates to an image pickup system comprising an electronic view finder suitable for achieving compactness and having a sufficient viewing angle of field and satisfactory optical performance. The image pickup system comprises an image pickup device, an image display device for displaying an image, a controller for converting image formation obtained from the image pickup device into a signal that enables the image information to be formed on the image display device, and a viewing optical system for guiding an image displayed on the display device to a viewer's eye. The viewing optical system comprises at least three lenses.

Abstract: The relay optical system comprises, in order from the intermediate image position I toward the the exit pupil EXP side, a first unit G1 having a negative refracting power and a second unit G2 having a positive refracting power, wherein the distance from the rearmost surface of the second unit to the exit pupil position is at least 30 mm. The relay optical system allows a photographing apparatus to be mounted on a microscope without the microscope and the photographing apparatus excluding each other from their predetermined positions.

Abstract: An eyepiece optical system is interposed between the positions of an intermediate image and a pupil in a finder and includes, in order from the intermediate-image side, a first lens unit having a negative lens located at the most intermediate-image-side position and a second lens unit provided with a path-bending optical member and having positive power as a whole, satisfying the following condition: −20<sf1<0 where sf1 is the shaping factor of the negative lens and is expressed as (r11+r12)/(r11−r12), where r11 is the radius of curvature of the intermediate-image-side surface of the negative lens and r12 is the radius of curvature of the pupil-side surface of the negative lens.

Abstract: An optical magnifier is provided. One general form of one example embodiment includes two lens elements, at least two aspheric surfaces, and at least one diffractive surface. Another general form of another example embodiment includes three lens elements, and at least three aspheric surfaces. At least two of the aspheric surfaces can be simple conics. The optical magnifier, suitable for use in an electronic display system, has an apparent field of view of at least +/−10 degrees; a magnification of at least 15×; a back focal length of at least 5 mm; and an eye relief greater than the effective focal length of the optical magnifier. The lens elements can be made from plastic.

Abstract: An optical magnifier is provided. One general form of one example embodiment includes two lens elements, at least two aspheric surfaces, and at least one diffractive surface. Another general form of another example embodiment includes three lens elements, and at least three aspheric surfaces. At least two of the aspheric surfaces can be simple conics. The optical magnifier, suitable for use in an electronic display system, has an apparent field of view of at least +/−10 degrees; a magnification of at least 15×; a back focal length of at least 5 mm; and an eye relief greater than the effective focal length of the optical magnifier. The lens elements can be made from plastic.

Abstract: The present invention discloses a dual-lens hybrid diffractive/refractive imaging system comprising: a first lens including a concave surface and a convex surface; and the second lens including a convex surface and a concave surface. The concave surface of the first lens is an objective surface facing the object. The convex surface faces the convex surface of the second lens, while the concave surface of the second lens faces the charge-coupled device (CCD) through a filter. Any surface of the first lens and the second lens is spheric or aspheric. Moreover, the imaging system comprises at least one diffractive surface, referred to as a hybrid diffractive/refractive surface, formed on any surface of the two lenses. Therefore, aberration is eliminated and image quality is improved without increasing the number of lenses.

Abstract: A system and method of providing a micromirror pixel 400 that is highly resistant to bright failure states. The micromirror 400 uses an asymmetric yoke 402 to ensure the mirror is only attracted to the address electrode in one rotation direction. The landing mechanism on the other side of the torsion binge axis also is altered to allow the pixel to over rotate in the “off” direction. The over rotation ensures that light reflected by the mirror when in the off direction will miss the projection lens pupil, allowing the corresponding pixel to remain dark in both an operational and failed state.

Abstract: A compound refractive lens for focusing, collecting, collimating and imaging with x-rays comprising N unit lenses numbered i=1 through N unit lenses substantially aligned along an axis such that i-th lens having a displacement ti orthogonal to said axis, with said axis located such that the sum of the lens displacements ti equals zero, and wherein each of said unit lenses comprises a lens material of lithium, carbon, or polyimide. A method for molding and housing the unit lenses is provided such that the unit lens have high surface and optical quality, and do not chemically deteriorate due to absorption of water or oxidation.

Abstract: The invention is directed to a method for making composite articles, including optical lenses, which includes the steps of obtaining a substrate; placing a semi-solid-like polymerizable composition in contact with at least one of the front or back surface of the substrate; compressing or heating the resulting semi-solid/substrate sandwich between two mold halves, where the mold contacting the semi-solid polymerizable material has a desired surface geometry; and exposing the semi-solid/substrate sandwich to a source of polymerizing energy. The resulting composite article has the desirable characteristics of the substrate but is also easily fabricated as a result of the semi-solid molding process. Also included within the present invention is a composite article comprising a substrate portion and at least one layer of a cured resin bonded to the substrate portion, the cured resin comprising an interpenetrating crosslinked polymer network of reactive plasticizer within a dead polymer.

Abstract: An eyepiece lens system using an aspherical lens can be formed at a low cost, having an eye relief equivalent to 80% or more of the focal length of the entire eyepiece lens system, with aberrations satisfactorily corrected up to the circumference of the field of view, as well as a telescope, a binocular and a microscope. The eyepiece lens system comprises a cemented lens and a positive lens, and at least one of the lens surfaces is formed aspherical. The aspherical surface is a hybrid type spherical surface formed by applying a synthetic resin layer on a basic spherical surface made of glass. There are also provided a telescope, a binocular and a microscope employing such eyepiece lens system.

Abstract: The relay optical system comprises, in order from the intermediate image position I toward the the exit pupil EXP side, a first unit G1 having a negative refracting power and a second unit G2 having a positive refracting power, wherein the distance from the rearmost surface of the second unit to the exit pupil position is at least 30 mm. The relay optical system allows a photographing apparatus to be mounted on a microscope without the microscope and the photographing apparatus excluding each other from their predetermined positions.

Abstract: A real image mode variable magnification finder has an objective optical system with positive refracting power, an image erecting optical system, and an ocular optical system with positive refracting power. The objective optical system has a first lens unit with negative refracting power, a second lens unit with negative refracting power, a third lens unit with positive refracting power, and a fourth lens unit with negative refracting power. When the magnification of the finder is changed, at least one lens unit, namely the third lens unit is moved. In this way, the total length of the objective optical system can be reduced, and thus a compact finder is obtained.

Abstract: An eyepiece optical system for projecting an enlarged virtual image of a two-dimensional image on an observer's pupil has a first reflective/transmissive surface formed as a flat surface, a second reflective/transmissive surface so shaped as to be concave to the pupil side, and a negative-powered optical element having a negative power and arranged between the second reflective/transmissive surface and the two-dimensional image. Here the focal length of the negative-powered optical element f2 and the focal length of the entire eyepiece optical system fs are so determined as to fulfill the following condition: −1.0<fs/f2<−0.1.

Abstract: An eyepiece comprises, successively from the eye side, a first lens L1, which is a diffractive optical element with a diffractive optical surface on the object side, made of a biconvex lens having a surface with a greater curvature directed onto the eye side; and a second lens L2, which is a diffractive optical element with a diffractive optical surface on the eye side, made of a meniscus lens with a positive refracting power having a convex surface directed onto the eye side. Both of the diffractive optical elements satisfy the following conditional expression (1): E<0  (1) where E is the coefficient of the quadratic term of the phase difference function.

Abstract: In order to provide an eyepiece lens which has a sufficiently long eye relief and a high magnification, there is provided an eyepiece lens for observing an image formed by an objective lens through an erect system, at least comprising a first lens group 4 having a positive refracting power and a second lens group 3 having a negative refracting power in this order from the side of an observer, and satisfying the following condition: −3<SF1<−1  (1) where SF1 indicates a shape factor of the first lens group 4, and SF indicates a shape factor of the lens group, which is defined by: SF=(Rs+RE)/(Rs−RE), where Rs indicates a radius of curvature of a lens surface which is closest to the object side and RE indicates a radius of curvature of a lens surface which is closest to the observer side.

Abstract: In order to provide an eyepiece lens which has a sufficiently long eye relief and a high magnification, there is provided an eyepiece lens for observing an image formed by an objective lens through an erect system, at least comprising a first lens group 4 having a positive refracting power and a second lens group 3 having a negative refracting power in this order from the side of an observer, and satisfying the following condition:

Abstract: The invention relates to a microscope eyepiece with theoretically reduced astigmatism in a compensating optical system. The inventive eyepiece has 10× magnification, a sight field (SFZ)≦25 and a Petzval sum (SP) of 0.014≦SP≦0.021. Said eyepiece comprises a special field lens placed in front of a field stop and a negative lens in the eye lens section placed behind said field stop. The inventive field lens is embodied in the form of a simple, thick, positively diffracting meniscus which is convex in relation to the field stop and provided with the following field lens factor: 0.95≦beta′≦1.05. The eye lens section can be displaced in relation to the field stop to enable diotropic adjustment. Special, advantageous embodiments of the field lens and examples of embodiments of the microscope eyepiece, complete with structural data, are described.

Abstract: The invention relates to an image pickup system comprising an electronic view finder suitable for achieving compactness and having a sufficient viewing angle of field and satisfactory optical performance. The image pickup system comprises an image pickup device, an image display device for displaying an image, a controller for converting image formation obtained from the image pickup device into a signal that enables the image information to be formed on the image display device, and a viewing optical system for guiding an image displayed on the display device to a viewer's eye. The viewing optical system comprises at least three lenses.

Abstract: In one form, an imaging system comprises an imager that forms an image of an object in a field of view, a rotationally symmetric lens assembly disposed between the imager and the object, and an equalizer. The rotationally symmetric lens assembly provides increased collection efficiency for a given depth of field, whereby the rotationally symmetric lens assembly causes aberration, compared to a well-focused lens. The rotationally symmetric lens assembly comprises a front negative lens, a rear positive lens, and an aperture positioned between the front and rear lenses. The equalizer, which is connected to the imager, receives image data and at least partially compensates for the aberration caused by the rotationally symmetric lens assembly.