Abstract: Aspects of the invention disclose an external and an add-on anamorphic lens, which comprises a focus group and an anamorphic group disposed in sequence from an object side to an image side along the optical axis. The focus group comprises a first lens and a second lens. The first lens and the second lens are spherical lenses. The anamorphic group includes a third lens, a fourth lens, and a fifth lens. These lenses are cylindrical lenses. The position of the first lens is adjustable and therefore solve the problem of requiring secondary focusing of the prior art.

Abstract: The present invention relates to optical imaging systems which are able to provide increased depth of field to microscope devices, motion-picture cameras, and still photographic cameras, while also reducing or elimination breathing while the focus of the device is adjusted. Optical systems described herein are also able to be used with standard film and digital sensor formats, and are able to be attached to, or integrated with, photographic and motion-picture cameras, including currently existing cameras.

Abstract: Systems and methods for testing and characterization of optical surfaces which works equally well on concave, flat, convex, and non-conic optical surfaces, and which does not require that a master surface be first produced. The method is automatic and requires little human intervention. It provides an extremely high degree of accuracy, and provides repeatability of measurements within a minuscule tolerance of error. The method determines the evolute of the surface automatically, deterministically, and repeatably via orthogonal reflection by ascertaining the evolute of the surface's figure along multiple diameters of the surface.

Abstract: The present disclosure provides a method, a device and a system for correcting distortion of a wide-angle lens. The method includes: acquiring n half field of views FOVs ?1 to ?n of the wide-angle lens, and acquiring ratios of adjacent FOVs ?1 to ?(n-1) according to the n half FOVs ?1 to ?n; obtaining image heights IHs r1 to rn corresponding to the n half FOVs according to the n half FOVs ?1 to ?n; obtaining an IH relationship of adjacent half FOVs according to the ratios of adjacent FOVs ?1 to ?(n-1) and the IHs r1 to rn corresponding to the n half FOVs, and obtaining the IH of each half FOV through recurrence calculation according to an IH corresponding to a maximum FOV and the IH relationship of adjacent half FOVs; and correcting distortion of the wide-angle lens across FOVs according to the IH of each half FOV.

Abstract: A supplementary lens system for providing at least one supplementary lens in front of a camera module of an electronic device, the supplementary lens system including an object-side lens-element unit with positive refractive power and an image-side lens-element unit with positive refractive power. The object-side lens-element unit and the image-side lens-element unit are configured to generate an intermediate image between the object-side lens-element unit and the image-side lens-element unit. Furthermore, the invention relates to a supplementary lens for such a supplementary lens system.

Abstract: An optical lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element and a third lens element. The first lens element with positive refractive power has an object-side surface being convex, and the object-side surface and an image-side surface thereof are aspheric. The second lens element with negative refractive power has an image-side surface being concave, and an object-side surface and the image-side surface thereof are aspheric. The third lens element with refractive power has an object-side surface being concave, and the object-side surface and an image-side surface thereof are aspheric. The optical lens assembly further includes a stop with no lens element having refractive power disposed between the stop and the first lens element. The optical lens assembly has a total of three lens elements with refractive power.

Abstract: A lithographic system includes a lithographic apparatus and a scatterometer. In an embodiment, the lithographic apparatus includes an illumination optical system arranged to illuminate a pattern and a projection optical system arranged to project an image of the pattern on to a substrate. In an embodiment, the scatterometer includes a measurement system arranged to direct a beam of radiation onto a target pattern on said substrate and to obtain an image of a pupil plane representative of radiation scattered from the target pattern. A computational arrangement represents the pupil plane by moment functions calculated from a pair of orthogonal basis function and correlates the moment function to lithographic feature parameters to build a lithographic system identification. A control arrangement uses the system identification to control subsequent lithographic processes performed by the lithographic apparatus.

Abstract: A free space optical receiver comprising a photodetector and a fiber bundle. The fiber bundle comprises a plurality of optical fibers splayed apart at one of their ends to receive free space optical energy from multiple directions. The splayed apart ends of the plurality of optical fibers may create a hemispherical shape. Each of the plurality of optical fibers has an acceptance cone for which it couples optical energy into the splayed end of the optical fiber. The acceptance cones of the splayed ends of the plurality of optical fibers may overlap to form an omnidirectional acceptance zone. The other, non-splayed ends of the plurality of optical fibers are communicatively coupled to the photodetector, which is positioned to receive the free space optical energy from the non-splayed ends of the plurality of optical fibers. An optical communication system including the free space optical receiver is also described.

Abstract: A laser scanning unit includes a scanning lens, a control portion, and a storage portion. The control portion controls a light amount of a light beam emitted from a light source. The storage portion stores therein aberration characteristics representing a relationship between image heights of the scanning lens and a wavefront aberration amount, which have been obtained in advance. The control portion, when the scanning is performed, controls the light amount of the light beam in accordance with the aberration characteristics, such that the light amount is set to a predetermined first light amount, at a point of a first image height where the wavefront aberration amount has a first value, and the light amount is set to a second light amount larger than the first light amount, at a point of a second image height where the wavefront aberration amount has a second value larger than the first value.

Abstract: A method of adjusting the pupil delay compensation of a convergent or divergent beam that includes placing a device composed of an afocal system comprising one or more passive optical components disposed on the propagation axis of the beam, at least one of the components being a focusing diffractive component, and moving the device along the propagation axis of the beam until the required pupil delay compensation is obtained, where the compensation is the algebraic sum of pupil delays of each passive optical component of the afocal system and lying in a range of values the limits of which are functions of the particular combination of the optical components chosen to form the afocal system of the compensation device.

Abstract: A laser system including a laser source that generates a laser beam and an optical switch that receives the laser beam and sends the laser beam to either a fast path or a slow path, wherein the F/# of the fast path is lower than the F/# of the slow path. The laser system includes an afocal optical system in the slow path and receives the laser beam from the optical switch and an x-y scanner that receives either a laser beam from the slow path or a laser beam from the fast path. The laser system including a scan lens system that performs a z-scan for the scanning laser beam only in the case wherein the scanning laser beam is generated from the laser beam in the fast path. The laser system including an aspheric patient interface device that receives a laser beam from the scan lens system.

Abstract: The invention provides a stereoscopic imaging optical system that has a total optical length short enough to be suitable for use in electron image microscopes. The stereoscopic imaging optical system comprises, in order from its object side, one objective lens DB and a plurality of zoom imaging optical systems ZI. Each zoom imaging optical system ZI comprises, in order from its object side, a positive first group G1, a negative second group G2, an aperture stop AS, a positive third group G3 and a positive fourth group G4. The second group moves for zooming on an optical axis, and the fourth group moves on the optical axis in association with the second group for correcting an image position fluctuation incidental to zooming. Various conditions are satisfied.

Abstract: A telescope that provides for simultaneous clear viewing of objects or areas at various distances may be either Galilean or astronomical. The telescope may be mounted on or into any mechanism or device used for targeting or aiming. Such devices may include iron sights of small arms weapons, and cameras and telescopes, which may be either electrically or manually focused. These miniature scopes are engineered to maximize the clear depth-of-field viewing by the eye regardless of vision irregularities, such as Presbyopia, Myopia, Hyperopic, Astigmatism, or combinations of these, in conjunction with or without spectacle lens corrections. This aiming scope/device may be placed on a pair of spectacles in a very close proximity to the eye cornea. Other maximized scope image characteristics that occur are field-of-view, luminosity, and unmagnified and unbroken or distorted viewing field.

Abstract: The present invention provides a complex modular afocal variator in which a modular afocal variator is supplemented with additional optics to form a more complex, but still modular afocal variator system, that can impart internal focusing as well as active spherical and chromatic aberration corrective improvement.

Abstract: A projection apparatus has a spatial light modulator to modulate illumination from a laser light source. A base projection lens has, from its long conjugate side to its short conjugate side, a first lens group with negative focal length and with a first lens element that has a negative focal length and a second lens element of positive focal length, a second lens group of negative focal length and spaced apart from the first lens group and having one or more cemented lens elements, and a third lens group spaced apart from the second lens group and having a lens with a positive focal length. The base projection lens has a first field of view and is telecentric in its short conjugate. An afocal attachment to the base projection lens alters the first field of view by the same amount in both of two orthogonal directions.

Abstract: Optical system for processing a light beam comprises first and second optical means that are convergent and divergent respectively and form an afocal optical device. The first optical means comprises a single convergent lens. According to the invention, this convergent lens provides an order 0 beam and an order 2 beam resulting from the light beam to be processed passing through this lens after having been subjected to a 0 reflection and 2 reflections respectively on the lens faces, and the lens is optimised for the order 2 beam and has an aperture f/# less than 4 for this order 2 beam, with a wave front quality less than ? peak-to-valley, where ? is the wavelength of the light beam to be processed.

Abstract: Miniature telescopes of both Galilean and astronomical design are fashioned to allow bi-level viewing, simultaneously, of both magnified scope images and non magnified normal images of both far and near objects or areas. Improvements in bi-leveling telescopes involve: objective lens aspherics, ocular lens materials of high refractive indices, anti-reflective fabric like materials for internal light control. This combination of innovations results in a bi-levelable miniature telemicroscope displaying wider magnified fields which display brighter and clearer imagery. Peripheral chromatic and spherical aberrations are considerably reduced even in shorter length telescope units. These shorter length scopes are spectacle mounted in such a way that the front surface of a spectacle carrier lens is coplanar with the telescope objective lens. Tintings and other coatings can now be applied to any of the scope's lenses or internal disks as well as to spectacle carrier lenses.

Abstract: The present invention provides optical systems containing an afocal variator able to impart focus means to the optical system, as well as essentially constant magnification throughout the focal translation. The present application teaches a specific formula or set of spacing requirements for the positioning of the afocal variator that can be used with any afocal variator optical lens system comprised of various lens combinations. Provided that the formula for spacing the afocal variator within the optical system is utilized, the afocal variator acts not only to focus the optical system but maintains substantially constant magnification during the translation of focus.

Abstract: Optical system for processing a light beam comprises first and second optical means that are convergent and divergent respectively and form an afocal optical device. The first optical means comprises a single convergent lens. According to the invention, this convergent lens provides an order 0 beam and an order 2 beam resulting from the light beam to be processed passing through this lens after having been subjected to a 0 reflection and 2 reflections respectively on the lens faces, and the lens is optimised for the order 2 beam and has an aperture f/# less than 4 for this order 2 beam, with a wave front quality less than ? peak-to-valley, where ? is the wavelength of the light beam to be processed.

Abstract: An afocal monolithic optical element formed of a shallow cylinder of optical material (glass, polymer, etc.) with fast aspheric surfaces, nominally confocal paraboloids, configured on the front and back surfaces. The front surface is substantially planar, and this lends itself to deposition of multi-layer stacks of thin dielectric and metal films to create a filter for rejecting out-of-band light. However, an aspheric section (for example, a paraboloid) can either be ground into a small area of this surface (for a Cassegrain-type telescope) or attached to the planar surface (for a Gregorian-type telescope). This aspheric section of the surface is then silvered to create the telescope's secondary mirror. The rear surface of the cylinder is figured into a steep, convex asphere (again, a paraboloid in the examples), and also made reflective to form the telescope's primary mirror.

Abstract: An optical viewer is disclosed which incorporates plastic lenses which reduce the weight and cost of the optical viewer. In accordance with an important aspect of the invention, the optical design of the viewer is configured to compensate for the inferior optical characteristics of the plastic lenses to provide an optical viewer with comparable performance relative to optical viewers with glass lenses.

Abstract: The present invention provides an afocal lens for an optical head that can ensure WD while satisfying NA, the optical head, an optical disk apparatus, a computer, an optical disk player, and an optical disk recorder. Using a blue-violet laser beam source with wavelength of about 400 nm, and in an optical head compatible to optical disks having different protective substrate thickness, an afocal lens that expands a diameter of light flux of light from a collimating lens and emits the light as substantially parallel light to an objective lens is provided between the collimating lens and the objective lens. The configuration makes it possible to ensure WD while satisfying NA.

Abstract: An afocal Galilean attachment lens is disclosed, with the lens comprising, along an optical axis, a first lens group with overall negative optical power and a second lens group with overall positive power. The first and second lens groups are arranged to define a Galilean configuration. The lens also has exit and an entrance pupils with respective diameters DEX and DEN that define a pupil magnification PM=DEX/DEN>4 and in some embodiments PM>10. The afocal Galilean attachment lens also has a length parameter defined LP>200 and in some embodiments LP>700. The extreme length of the afocal Galilean attachment allows for photographing or filming objects that are remote or otherwise hard to photograph while also providing a relatively large depth of field.

Abstract: A method of adjusting the pupil delay compensation of a convergent or divergent beam that includes placing a device composed of an afocal system comprising one or more passive optical components disposed on the propagation axis of the beam, at least one of the components being a focusing diffractive component, and moving the device along the propagation axis of the beam until the required pupil delay compensation is obtained, where the compensation is the algebraic sum of pupil delays of each passive optical component of the afocal system and lying in a range of values the limits of which are functions of the particular combination of the optical components chosen to form the afocal system of the compensation device.

Abstract: The present invention provides optical systems containing an afocal variator able to impart focus means to the optical system, as well as essentially constant magnification throughout the focal translation. The present application teaches a specific formula or set of spacing requirements for the positioning of the afocal variator that can be used with any afocal variator optical lens system comprised of various lens combinations. Provided that the formula for spacing the afocal variator within the optical system is utilized, the afocal variator acts not only to focus the optical system but maintains substantially constant magnification during the translation of focus.

Abstract: The present invention provides optical systems, devices and methods which utilize one or more electroactive polymer actuators to adjust an optical parameter of the optical device or system.

Abstract: A high-performance lens system includes lens elements of small diameters for projecting enlarged images from light valves (mainly Digital Micromirror Devices (DMDs)) for forming images by changing reflecting directions of light. The lens system includes, sequentially in order from a magnifying side, a first lens group which makes up a substantially afocal optical system as a whole and a second lens group having a positive refractive power as a whole. Depending on the application a third lens group made up of a single positive lens element is provided in the vicinity of the light valve on a contracting side of the second lens group.

Abstract: A high-performance lens system includes lens elements of small diameters for projecting enlarged images from light valves (mainly Digital Micromirror Devices (DMDs)) for forming images by changing reflecting directions of light. The lens system includes, sequentially in order from a magnifying side, a first lens group which makes up a substantially afocal optical system as a whole and a second lens group having a positive refractive power as a whole. Depending on the application a third lens group made up of a single positive lens element is provided in the vicinity of the light valve on a contracting side of the second lens group.

Abstract: An imaging lens includes first to third lenses G1 to G3 arranged in order from a object side. The first lens has a biconvex shape in a vicinity of an optical axis Z1. The second lens has a concave surface facing a object side. The second lens has a negative refractive power. The third lens has a positive or negative refractive power and has a meniscus shape containing, in a vicinity of the optical axis, a convex surface facing the object side. The following conditional expression is satisfied: 0.7<f1/f<1.3 0.2?D2/f<0.5 where f denotes a focal length of the entire system of the imaging lens, f1 denotes a focal length of the first lens G1 and D2 denotes an interval on the optical axis Z1 between the first lens G1 and the second lens G2.

Abstract: An afocal Galilean attachment lens is disclosed, with the lens comprising, along an optical axis, a first lens group with overall negative optical power and a second lens group with overall positive power. The first and second lens groups are arranged to define a Galilean configuration. The lens also has exit and an entrance pupils with respective diameters DEX and DEN that define a pupil magnification PM=DEX/DEN>4 and in some embodiments PM>10. The afocal Galilean attachment lens also has a length parameter defined LP>200 and in some embodiments LP>700. The extreme length of the afocal Galilean attachment allows for photographing or filming objects that are remote or otherwise hard to photograph while also providing a relatively large depth of field.

Abstract: A telescope that provides for simultaneous clear viewing of objects or areas at various distances may be either Galilean or astronomical. The telescope may be mounted on or into any mechanism or device used for targeting or aiming. Such devices may include iron sights of small arms weapons, and cameras and telescopes, which may be either electrically or manually focused. These miniature scopes are engineered to maximize the clear depth-of-field viewing by the eye regardless of vision irregularities, such as Presbyopia, Myopia, Hyperopic, Astigmatism, or combinations of these, in conjunction with or without spectacle lens corrections. This aiming scope/device may be placed on a pair of spectacles in a very close proximity to the eye cornea. Other maximized scope image characteristics that occur are field-of-view, luminosity, and unmagnified and unbroken or distorted viewing field.

Abstract: The invention is directed to an arrangement and a method for imaging depth-structured objects and for calibrating the imaging in connection therewith, preferably for generating stereoscopic images from different observation planes at different depth levels of an object. According to the invention, in an optical arrangement for imaging depth-structured objects comprising an entrance pupil, an aperture diaphragm, and a receiver surface positioned in the imaging beam path, at least one optical assembly which is displaceable in axial direction is provided between the aperture diaphragm and the receiver surface, and the displacement of this optical assembly within a predetermined length range causes a change in the focus position while the magnification remains the same.

Abstract: A telescope that provides for simultaneous clear viewing of objects or areas at various distances may be either Galilean or astronomical. The telescope may be mounted on or into any mechanism or device used for targeting or aiming. Such devices may include iron sights of small arms weapons, and cameras and telescopes, which may be either electrically or manually focused. These miniature scopes are engineered to maximize the clear depth-of-field viewing by the eye regardless of vision irregularities, such as Presbyopia, Myopia, Hyperopic, Astigmatism, or combinations of these, in conjunction with or without spectacle lens corrections. This aiming scope/device may be placed on a pair of spectacles in a very close proximity to the eye cornea. Other maximized scope image characteristics that occur are field-of-view, luminosity, and unmagnified and unbroken or distorted viewing field.

Abstract: An apparatus includes a planar waveguide, first and second gratings for coupling electromagnetic radiation into the planar waveguide, and a beam shaper for controlling the amplitude distribution of the electromagnetic radiation that impinges on the first and second gratings. A method of coupling electromagnetic radiation into a planar waveguide is also provided.

Abstract: Optical devices and methods for providing wide field magnification to assist the visually impaired, and others, are provided. The optical device includes a plurality of telescopic lens sets, for example, a plurality of telescopes, each telescopic lens set including an objective lens and an ocular lens, and a plurality of refracting optical elements, for example, prisms, positioned in front of at least some of the objective lenses. The refracting optical elements are adapted to at least partially redirect light rays toward at least some of the objective lenses to provide wider fields of view, for example, a wider contiguous field of view. Aspects of the invention can provide fields of view up to 40 degrees or more. These wider fields of view can greatly enhance the visual acuity of the visually impaired, as well as provide wider fields of view for non-corrective purposes, such as for field observations.

Abstract: A high-performance lens system including lens elements of small diameters for projecting on to a screen or the like in an enlarged fashion images from light valves such as mainly DMDs (Digital Micromirror Devices) for forming images by changing reflecting directions of light is provided. A lens system includes, sequentially in that order from a magnifying side, a first lens group which makes up a substantially afocal optical system as a whole and a second lens group having a positive refractive power as a whole, and depending upon applications, a third lens group made up of a single positive lens element is provided in the vicinity of a light valve such as a DMD on a contracting side of the second lens group.

Abstract: An optical device is provided which includes a plurality of optical modules and an alignment compensation module. Each optical module includes an optical component fixedly coupled to a relative reference mount. The relative reference mount is configured to attach to a substrate. A plurality of optical modules mount on the substrate to form the optical device. The alignment compensation module removes residual alignment errors of the optical device.

Abstract: A device for focusing a laser beam includes a first telescopic configuration and a second telescopic configuration. The first telescopic configuration includes a collimating optical element for collimating the laser beam and a downstream focusing optical element for focusing the laser beam onto a focal point. The second telescopic configuration includes a first lens and a downstream second lens disposed in the divergent beam path upstream of the first telescopic configuration. The first and second lenses of the second telescopic configuration are moveable relative to each other in the beam direction.

Abstract: The invention is directed to an afocal zoom system, particularly for use in microscopes, comprising at least four optical assemblies, two of which assemblies are movable relative to one another and to the rest of the assemblies for the purpose of changing the magnification. It is the object of the invention to develop an afocal zoom system which enables a relatively small structural size for a microscope also in combination with a suitable drive mechanism. This object is met by an afocal zoom system of the type described above in which every adjustable magnification can be achieved by a displacing movement of the two movable optical assemblies in the same direction.

Abstract: A magnification loupe carried by spectacles has a Galilean lens system comprising a single-element eyepiece lens and a two-element objective lens. The loupes may be mounted to eyeglass frames by a flip-up mounting member, or they may be mounted through the eyeglass lenses of the spectacles. The loupes provide high magnification while minimizing weight to thereby reduce strain and discomfort to users. In an exemplary embodiment, the objective lens has a non-circular shape that provides a wide field of view while further minimizing the weight of the loupe. A correction lens may be interchangeably coupled to the loupe housing to permit selective replacement with another correction lens to vary the working distance of the loupe.

Abstract: A compact reflector telescope has a spherical primary reflector and a secondary reflector with a negative lens interposed there between in axial alignment therewith. Light reflected from the primary reflector is passed through the negative lens and is diverted by the secondary reflector to a positive lens at the side of the telescope tube. The positive lens focuses the light rays onto an eye piece or ocular or onto a photographic emulsion or electronic detector. The telescope reduces or substantially eliminates spherical aberration and can be configured to have a focal ratio significantly greater than the focal ratio of the primary reflector. The telescope produces a flat field of view and an image which is substantially diffraction limited.

Abstract: The invention concerns a zoom system, having various materials (glass types) and variable air spaces, for example for a surgical (stereo)microscope, constructed from four symmetrically arranged lens groups (2 through 5), each two lens groups (2, 5; 3, 4) being arranged identically and in mirror-image fashion with respect to one another. As a result of the special selection of glass types having anomalous partial dispersion, and the specific design features, a high zoom factor is achieved with a short overall length, as well as good correction of the secondary spectrum, astigmatism, and field curvature.

Abstract: The invention relates to an afocal zoom (1) for use in microscopes of high resolution and high zoom factors having a tube lens (11), the zoom comprising four successive optical assemblies (G1, G2, G3, G4) when viewed from the object end, the first assembly (G1) having a positive focal length (f1), the second assembly (G2) a negative focal length (f2), the third assembly (G3) a positive focal length (f3), and the fourth assembly (G4) a negative focal length (f4), and the first and the fourth assembly (G1, G4) being arranged in stationary fashion and the second and the third assembly (G2, G3) being arranged movably for modifying the magnification of the zoom (1), the zoom magnification decreasing with increasing distance (D23) between the two assemblies (G2, G3). The zoom operates in the range of “useful magnification” of the microscope with sufficient contrast if the zoom meets the meets specific conditions.

Abstract: A method for manufacturing a spectacle lens, in which at first a semi-finished uncut spectacle lens (hereinafter referred to as a blank) is produced, i.e. a spectacle lens having merely one finished optical surface (hereinafter described as base surface); subsequently a prescription-optimized surface is computed according to the data of a spectacle lens prescription; and then the prescription-optimized surface is finished according to the computed data. The invention is characterized by the following method steps: after the production of the semi-finished spectacle lens the base surface is measured; the prescription-optimized surface is computed and finished taking into account not only the individual data of the spectacle prescription, but also the actual shape of the base surface.

Abstract: A bonding apparatus that includes a bonding tool through which a wire passes and which performs bonding on a workpiece, a position detection camera which takes images of the workpiece, a reference member which is disposed in a specified position, and an optical assembly which conducts the image of the tool and reference member to the position detection camera. A lens used in the position detection camera and a lens installed in the optical assembly are arranged so that such lenses construct an afocal optical system.

Abstract: An optical lens arrangement for a rangefinder system in a photographic camera with a fixed viewfinder magnification SK and a fixed measuring base MB is configured to be coupled with a rangefinder eyepiece of the rangefinder system and is designed as an afocal telescope with a minimum 1.1 times and a maximum 1.7 times magnification SL. The magnification SL may be selected so that the product of the viewfinder magnification SK and the magnification SL is at least very nearly equal to 1.

Abstract: An afocal, wide converter lens is provided in order to shorten the focal length of a main lens, thereby shortening the projection distance that is needed to fully illuminate a given screen size when the wide converter lens is attached to the enlarging side of a main lens which is used as a projection lens of a projection apparatus. The wide converter lens is formed of, in sequential order in a direction from the enlarging side to the reducing side of the main lens: a first lens element of positive refractive power; at least one lens element of negative refractive power; a first cemented lens of negative refractive power that is formed of a negative lens element that is cemented to a positive lens element; and a second cemented lens of positive refractive power that is formed of a positive lens element that is cemented to a negative lens element. Various conditions are satisfied in order that the wide converter lens does not degrade the optical performance of the main lens.

Abstract: An afocal, wide converter lens is provided in order to shorten the focal length of a main lens, thereby shortening the projection distance that is needed to fully illuminate a given screen size when the wide converter lens is attached to the enlarging side of a main lens which functions as a projection lens of a projection apparatus. The wide converter lens is formed of, in sequential order in the direction from the enlarging side to the reducing side of the main lens, a lens element of positive refractive power, at least one lens element of negative refractive power, a positive meniscus lens element having its convex surface on the enlarging side, a negative meniscus lens element having its concave surface on the enlarging side, and a cemented lens of overall positive refractive power. Various conditions are satisfied in order that the wide converter lens does not degrade the optical performance of the main lens.

Abstract: A dual field-of-view objective system (40) which is inexpensive, has high transmission and is essentially achromatized and athermalized. The system (40) uses a silicon front lens A and all lens elements have positive temperature/refractive index change coefficient.

Abstract: An image-blur correcting viewing-optical system including an objective optical system, an image-erecting optical system and an eyepiece optical system. The objective optical system includes an image-blur correcting lens element which is driven in a direction perpendicular to the optical axis, and the image-blur correcting lens element satisfies the following condition: 1 mm≦&phgr;−&phgr;0≦3 mm  (1) wherein &phgr; designates a mechanical diameter of the image-blur correcting lens element; and &phgr;0 designates the diameter of an axial open aperture of the first surface of the image-blur correcting lens element.