Abstract: A reflecting optical element is disclosed which includes the following articles. The reflecting optical element is constituted by: a base member having a continuous curved-surface portion, and a resin layer integrally formed of resin on the curved surface of the base member, and having a plurality of mutually discontinuous curved surfaces to be reflecting surfaces. The base member is made of a material smaller in coefficient of linear expansion than the resin for forming the resin layer. Thus, a reflecting optical element is provided which is low in optical-performance deterioration caused by the temperature effect, and small in the number of restraints in fabrication.

Abstract: An optical element comprising an object-side imaging element for imaging an object on an intermediate image plane in an optical path before a final image plane and an image-side imaging element for reimaging an object image formed on the intermediate image plane, on the final image plane, wherein at least one of the object-side imaging element and the image-side imaging element comprises an off-axial curved surface, and wherein aberration is generated by both of the object-side imaging element and the image-side imaging element, thereby flattening (disturbance of) a light intensity distribution caused on the final image plane by a noise source at or near the intermediate image plane.

Abstract: A laser beam includes a concave or convex mirror which is reflective for wavelength of the high intensity beam. The reflective mirror is located along a preselected path of a high intensity laser beam so that the high intensity laser beam intersects the mirror at a first position. A beam collimator is located in the path of the high intensity beam reflected by the concave or convex mirror. The concave or convex mirror is movably mounted desirably rotatably mounted in the path of the high intensity beam. Desirably the mirror is rotated about a preselected axis. Desirably, the axis is selected so that when the mirror is rotated to a new position, the high intensity beam will be reflected along the same path to the collimator as it was prior to any rotation.

Abstract: A catadioptric projection lens for imaging a pattern arranged in an object plane onto an image plane, preferably while creating a real intermediate image, including a catadioptric first lens section having a concave mirror and a physical beamsplitter having a beamsplitting surface, as well as a second lens section that is preferably refractive and follows the beamsplitter, between its object plane and image plane. Positive refractive power is arranged in an optical near-field of the object plane, which is arranged at a working distance from the first optical surface of the projection lens. The beamsplitter lies in the vicinity of low marginal-ray heights, which allows configuring projection lenses that are fully corrected for longitudinal chromatic aberration, while employing small quantities of materials, particularly those materials needed for fabricating their beamsplitters.

Abstract: The invention relates to a small-format display optical system using a reflection type image device as an image display device and capable of displaying bright, high-resolution images. The display optical system comprises a reflection type display device 3 for displaying an image, an illumination light source 5 for illuminating the reflection type display device 3, an illumination optical system for guiding light from the illumination light source 5 to the reflection type disply device 3, a relay optical system 21 for projection of an image appearing on the reflection type display device 3 and an eyepiece optical system 22 acting to converge a light beam from the relay optical system 21 toward the eyeball of a viewer. An image projected through the relay optical system 21 is formed near the eyepiece optical system 22.

Abstract: A catadioptric projection lens (1) which is designed in particular for use in microlithographic projection-exposure apparatus includes a plurality of refractive optical elements having intrinsic birefringence both in a catadioptric part (5) and in a dioptric part (18) adjacent to the image plane (3). Because these refractive optical elements in the catadioptric part (5) and in the dioptric part (18) are decoupled from one another with respect to polarisation by a polarisation-sensitive reflective layer (10), the catadioptric part (5) and the dioptric part (18) are compensated separately from one another with respect to intrinsic birefringence.

Abstract: An omnidirectional vision sensor includes: an optical system including a body-of-revolution mirror having a convex portion and having a symmetrical structure with respect to a revolution axis, wherein the body-of-revolution mirror includes a cutaway section in the convex portion of the body-of-revolution mirror so as to allow light incident from surroundings of the revolution axis of the body-of-revolution mirror to be collected; and imaging means, including a light-receiving element for receiving the collected light and image processing means for converting an optical image generated from the collected light received by the light-receiving element into image data. The revolution axis of the body-of-revolution mirror and an optic axis of the light-receiving element coincide.

Abstract: A reflecting-type optical system according to the invention includes an optical element composed of a transparent body having an entrance surface, an exit surface and at least three curved reflecting surfaces of internal reflection. A light beam coming from an object and entering at the entrance surface is reflected from at least one of the reflecting surfaces to form a primary image within the optical element and is, then, made to exit from the exit surface through the remaining reflecting surfaces to form an object image on a predetermined plane. In the optical system, 70% or more of the length of a reference axis in the optical element lies in one plane.

Abstract: The invention relates to a compact, high-performance yet wide-field real image type zoom finder comprising a positive objective optical system Ob and a positive eyepiece optical system Ep and further including an image-inverting means for erecting an real image formed by the objective optical system. The objective optical system Ob comprises a plurality of moving groups G2 and G3, and the eyepiece optical system Ep comprises positive reflecting surfaces, at least one of which is defined by a rotationally asymmetric surface, and satisfies conditions 1.25<dEP/fOC<2.0 and 0.5<lOC/fOC<1.3 where dEP is the distance as measured along an axial chief ray from a final surface to an eye point of the eyepiece optical system, fOC is the focal length of the eyepiece optical system, and lOC is the length as calculated on an air basis and measured along an axial chief ray from an intermediate image-formation plane to the final surface of the eyepiece optical system.

Abstract: An optical system comprises a three-mirror anastigmat including a primary mirror, a secondary mirror, and a tertiary mirror positioned to reflect a beam path. An intermediate image is formed on the beam path at an intermediate-image location between the secondary mirror and the tertiary mirror. A negative-optical-power field mirror is positioned in the beam path at a field-mirror location subsequent to the intermediate-image location along the beam path. The field mirror reflects the intermediate image to the tertiary mirror.

Abstract: An objective is configured with a first partial objective and a second partial objective. The first partial objective, which projects a first field plane onto an intermediate image, has a first, convex mirror and a second, concave mirror. The second partial objective, which projects the intermediate image onto a second field plane, has a third and a fourth mirror, both concave. All of the four mirrors have central mirror apertures. The axial distance between the first and second mirrors is in a ratio between 0.95 and 1.05 relative to the distance between the second mirror and the intermediate image. The axial distance ZM3-IM between the third mirror and the second field plane conforms to the relationship 1 0.03 · Du M3 + 5.0 ⁢   ⁢ mm < Z M3 - IM < 0.25 · Du M3 tan ⁡ ( arcsin ⁡ ( NA ) ) .

Abstract: An optical system has a light source of an optical beam, and a wavefront distortion generator that introduces a known wavefront distortion into at least one wavelength component of the optical beam prior to the formation of an intermediate image. A focusing device receives the optical beam, produces the intermediate image of the optical beam, and outputs the optical beam. A wavefront distortion corrector, after the formation of the intermediate image, introduces a wavefront distortion correction into each component of the optical beam into which the known wavefront distortion was introduced by the wavefront distortion generator. The wavefront distortion correction is the reverse of the known wavefront distortion introduced into the optical beam by the wavefront distortion generator.

Abstract: A panoramic imaging lens having an annular light incident surface formed in a substantial convex lens form; a first reflective surface formed in an annular concave mirror form to reflect light inside the lens; a second reflective surface provided at a central part inside the annular light incident surface to reflect the reflected light from the first reflective surface toward an inner part of the annular first reflective surface; and a light outgoing surface positioned at a central part inside the annular first reflective surface and opposing the second reflective surface to transmit light. A non-reflective part exerting no regular reflection of light is provided on a light path toward the light incident surface amongst light paths of light proceeding to agree with a light path of imaging light incident on and refracted at the light incident surface and proceeding inside the lens.

Abstract: A reflecting type of zoom optical system comprises a plurality of optical elements each of which includes a transparent body and two refracting surfaces and a plurality of reflecting surfaces formed on the transparent body and is arranged so that a light beam enters the transparent body from one of the two refracting surfaces, repeatedly undergoes reflection by the plurality of reflecting surfaces, and exits from the other of the two refracting surfaces, and/or a plurality of optical elements on each of which a plurality of reflecting surfaces made from surface reflecting mirrors are integrally formed, and each of which is arranged so that an entering light beam repeatedly undergoes reflection by the plurality of reflecting surfaces and exits from the optical element.

Abstract: An optical element formed from a transparent optical material includes two refraction surfaces, a first reflection surface group having a plurality of internal reflection surfaces arrayed in a predetermined direction, a second reflection surface group opposing the first reflection surface group and having at least one internal reflection surface and two side surfaces opposing each other in parallel to the predetermined direction. Light incident from one of the refraction surfaces is alternately reflected by the internal reflection surfaces of the first reflection surface group and the internal reflection surface of the second reflection surface group and guided to the other refraction surface.

Abstract: An aspheric reduction objective has a catadioptric partial objective (L1), an intermediate image (IMI) and a refractive partial objective (L2). The catadioptric partial objective has an assembly centered to the optical axis and this assembly includes two mutually facing concave mirrors (M1, M2). The cutouts in the mirrors (B1, B2) lead to an aperture obscuration which can be held to be very small by utilizing lenses close to the mirrors and having a high negative refractive power and aspheric lens surfaces (27, 33). The position of the entry and exit pupils can be corrected with aspherical lens surfaces (12, 48, 53) in the field lens groups. The number of spherical lenses in the refractive partial objective can be reduced with aspherical lens surfaces (66, 78) arranged symmetrically to the diaphragm plane. Neighboring aspheric lens surfaces (172, 173) form additional correction possibilities.

Abstract: An objective comprising axial symmetry, at least one curved mirror and at least one lens and two intermediate images. The objective includes two refractive partial objectives and one catadioptric partial objective. The objective includes a first partial objective, a first intermediate a image, a second partial objective, a second intermediate image, and a third partial objective. At least one of the partial objectives is purely refractive. One of the partial objectives is purely refractive and one is purely catoptric.

Abstract: A projection lens for imaging a pattern arranged in an object plane onto an image plane using electromagnetic radiation from the extreme-ultraviolet (EUV) spectral region has several imaging mirrors between its object plane and image plane that define an optical axis of the projection lens and have reflective coatings. At least one of those mirrors has a graded reflective coating that has a film-thickness gradient that is rotationally symmetric with respect to a coating axis, where that coating axis is acentrically arranged with respect to the optical axis of the projection lens. Providing at least one acentric, graded, reflective coating allows designing projection lenses that allow highly uniform field illumination, combined with high total transmittance.

Abstract: A double mirror objective lens system uses a three optical surface refractor incorporating a convex mirror into a right surface thereof that reflects incident light to a concave mirror, which reflects the light back through the refractor and on toward a focal point of the system. This arrangement yields better resolution images with low spherical aberration, minimal chromatic aberration, and long working distance. A variation of the invention includes another refractor, a right surface of which carries the concave mirror to form a Mangin mirror. This variation on of the invention has even less aberration over increased wavelength range due to better corrected chromatic aberration.

Abstract: When n is taken as integers of 2 or more, n reflecting systems are constituted by providing reflecting mirrors on opposite (two) side surfaces in 2n side surfaces of a transparent body having the shape of a 2n-sided prism. The n reflecting systems are provided on each pair of opposite side surfaces, and images of an object are formed using each of the n reflecting systems.

Abstract: A zoom optical system comprises a plurality of optical elements. The plurality of optical elements include a first optical element having two refracting surfaces and a plurality of reflecting surfaces formed in a transparent body, being arranged such that a light beam enters an inside of the transparent body from one of the two refracting surfaces and, after being successively reflected from the plurality of reflecting surfaces, exits from the other of the two refracting surfaces, and/or a second optical element having a plurality of surface mirrors integrally formed and decentered relative to one another, being arranged such that an incident light beam exits therefrom after being successively reflected from reflecting surfaces of the plurality of surface mirrors, and a third optical element composed of a plurality of coaxial refracting surfaces.

Abstract: An imaging lens is used in image reading and adapted to image information of an original on a reading device. In the imaging lens at least one surface out of a plurality of surfaces forming the imaging lens has refracting power rotationally asymmetric with respect to the optical axis.

Abstract: A system for multiple mode imaging is disclosed herein. The system is a catadioptric system preferably having an NA greater than 0.9, highly corrected for low and high order monochromatic aberrations. This system uses unique illumination entrances and can collect reflected, diffracted, and scattered light over a range of angles. The system includes a catadioptric group, focusing optics group, and tube lens group. The catadioptric group includes a focusing mirror and a refractive lens/mirror element. The focusing optics group is proximate to an intermediate image, and corrects for aberrations from the catadioptric group, especially high order spherical aberration and coma. The tube lens group forms the magnified image. Different tube lens groups can be used to obtain different magnifications, such as a varifocal tube lens group to continuously change magnifications from 20 to 200×. Multiple imaging modes are possible by varying the illumination geometry and apertures at the pupil plane.

Abstract: A high resolution lens is provided as a condensing lens for collecting light made incident from a light source, of which one face is plane and the other face is curved. The curved face of the lens is coated with a reflecting material except for its central apex portion, and incident light is made incident through the plan portion of the lens. The curved face of the high resolution lens may be spherical or is a parabolic face to reduce aberration. When a parallel light is made incident on the plane face of the high resolution lens, it is reflected in the lens and totally reflected, and then is transmitted through the uncoated apex to an external object.

Abstract: A catadioptric projection lens for projecting a pattern located in an object plane onto an image plane without an intermediate image includes the following components between the object plane and the image plane in the given order: a first lens part for creating a beam that is directed at a physical beam splitter, a physical beam splitter with a beam splitter surface, a mirror group with a concave mirror, and a second lens part with positive focal power to create an image of the pattern on the image plane. The mirror group preferably has no free-standing lens, and the focal power of the mirror group is largely determined by the magnification of the concave mirror. The focal power of the mirror group is large enough to convert the incident divergent beam into a convergent beam. The system aperture is located on the image side behind of the concave mirror, preferably at the exit of the beam splitter.

Abstract: The present invention relates to providing enhanced panoramic images with an improved panoramic mirror. A panoramic mirror is provided with a controlled vertical field of view. The controlled vertical field of view improves the resolution of a viewable panoramic image by eliminating portions of unwanted images from the viewable panoramic image.

Abstract: An optical system includes a nonspherical outer dome that is rotationally symmetric about a central axis, a detector system, and an optical corrector positioned in an optical path between the outer dome and the detector system. At least one light baffle is positioned in the optical path between the outer dome and the detector system and is fixed in space relative to the central axis. There are typically from one to three baffles, each affixed to either the inter surface of the outer dome or to the optical corrector. Each baffle is a frustoconical tube that is rotationally symmetric about the central axis. A set of fins may be supported on one of the baffles, with each fin extending radially outwardly from an outer surface of the baffle and parallel to the central axis. The baffles combine to reduce stray light that otherwise would enter the optical system.

Abstract: The present invention relates to an omnidirectional wide angle optical system, which is associated with a sensor, camera, projector, medical instrument, surveillance system, flight control system, robotic command and control or sensing system, home entertainment system, conference area, virtual reality suite, theater, or similar article. The optical system consists of an external refracting surface which may be strongly curved, an strongly curved internal primary reflector surface, a secondary reflector surface (in most embodiments), central wide angle refracting optics (in some embodiments), a modular or integral imaging and correcting lens system which may have aperture adjustment means, and mounting components.

Abstract: An optical system of reflecting type according to the invention comprises an optical element composed of a transparent body having an entrance surface, an exit surface and at least three curved reflecting surfaces of internal reflection, wherein a light beam coming from an object and entering at the entrance surface is reflected from at least one of the reflecting surfaces to form a primary image within the optical element and is, then, made to exit from the exit surface through the remaining reflecting surfaces to form an object image on a predetermined plane, and wherein 70% or more of the length of a reference axis in the optical element lies in one plane.

Abstract: In a method for correcting optical wavefront errors in an optical system, the optical wavefront is calculated for different wavelengths and fields of view between the entry pupil (EP) and exit pupil (AP). Any phase differences are compensated by at least one surface (5, 7) compensating the phase differences in the beam path. A particular optical system, expediently in the form of a telescope, accordingly has a beam path which comprises the following: a first reflector (3), arranged along its axis (A), for reflecting a beam (1) incident along an optical axis (O) onto a concave second reflector (4) which throws the beam obtained from the first reflector (3) onto a third reflector (5), from which it is passed to a concave fourth reflector (6) in order to be reflected at an angle with said optical axis (O). Such a means (5, 7) for correcting the wavefront errors is provided in the beam path of such an optical system.

Abstract: An optical system has an aperture stop, and an optical unit placed on the image side of the aperture stop. The optical unit consists of the following components in the order named from the object side: a first optical component with a reflective curved surface, for forming an intermediate image of an object, a second optical component with a reflective curved surface, for forming an image of the aperture stop with light from the intermediate image of the object, and a third optical component with a reflective curved surface, for forming a secondary image of the object with light from the image of the aperture stop. When fB1(&thgr;), fB2(&thgr;), and fB3(&thgr;) are focal lengths of the first optical component, the second optical component, and the third optical component, respectively, at an azimuth &thgr;, the focal lengths satisfy the following conditions in the azimuth range of 0<&thgr;<2&pgr;: fB1(&thgr;)>0, fB2(&thgr;)<0, fB3(&thgr;)>0.

Abstract: A reflecting-type optical system according to the invention includes an optical element composed of a transparent body having an entrance surface, an exit surface and at least three curved reflecting surfaces of internal reflection. A light beam coming from an object and entering at the entrance surface is reflected from at least one of the reflecting surfaces to form a primary image within the optical element and is, then, made to exit from the exit surface through the remaining reflecting surfaces to form an object image on a predetermined plane. In the optical system, 70% or more of the length of a reference axis in the optical element lies in one plane.

Abstract: The invention relates to a wide-angle catoptric system. The system comprises a convex primary mirror (M1), a secondary mirror (M2), a tertiary mirror (M3), and a quaternary mirror (M4), and it is characterized in that the secondary mirror (M2) is convex. The invention is particularly applicable to astronomical or space observation over a broad spectral range.

Abstract: An all-reflective zoom optical system is disclosed. The system comprises a plurality of curved relay mirrors successively reflecting electromagnetic radiation received by the system to generate a real image with electromagnetic radiation on a focal surface that is fixed across the zoom range. Further, the entrance aperture also is constant for any zoom position. The curved relay mirrors are movable in relationship to each other in mutually parallel tracks to effect the magnification. The system further includes a primary and secondary mirror for collecting and reflecting incoming electromagnetic radiation to the curved relay mirrors.

Abstract: The present invention relates to an omniramic wide angle optical system which is associated with a camera, projector, medical instrument, surveillance system, flight control system, or similar article. The optical system typically consists of a Cassegrain system having a strongly curved convex reflecting surface with a prolate aspheric figure, a secondary reflector surface, and a modular imaging and correcting lens system. The invention further relates to the distribution of still or motion picture image elements by optical or electronic means, whereby the entire image or any subset thereof is converted from a two dimensional annular image or a segment thereof to a viewable horizontal image or a subset thereof; or, from a horizontal format image or a subset thereof into an annular image or a segment thereof.

Abstract: A compact, lightweight and bright image display apparatus which uses a non-telecentric optical system, or a decentered optical system and a reflection-type image display device, such as a reflection-type LCD, to have high optical performance. The image display apparatus comprises an image display device, and an ocular optical system which leads an image formed by the image display device to an eye point of an observer without forming an intermediate image so that the image can be observed as a virtual image. The ocular optical system comprises a decentered optical system having at least one decentered back-coated reflecting surface. The image display device is a reflection-type image display device which displays an image by reflection of illumination light. An illumination means for forming the illumination light is arranged outside an optical path between the reflection-type image display device and the eye point of the observer.

Abstract: An optical system includes an optical element having a plurality of reflective surfaces integrally formed, at least one reflective surface out of the plurality of reflective surfaces of the optical element being a curved surface a normal to which at an intersecting point with a reference axis does not coincide with the reference axis, an image pickup element to which light successively reflected by the plurality of reflective surfaces is incident, and an optical member for making at least part of the light that ought to enter the image pickup element, travel in an optical path different from an optical path toward the image pickup element. The light made to travel in the different optical path by the optical member is utilized for a purpose other than image pickup by said image pickup element.

Abstract: A zoom lens comprises a plurality of optical elements each of which includes a transparent body having two refracting surfaces and a plurality of reflecting surfaces and is arranged so that a light beam enters the transparent body from one of the two refracting surfaces, repeatedly undergoes reflection, and exits from the other of the two refracting surfaces, and/or a plurality of optical elements on each of which a plurality of reflecting surfaces made from front surface mirrors are integrally formed, and each of which is arranged so that an entering light beam repeatedly undergoes reflection by the plurality of reflecting surfaces and exits from the optical element.

Abstract: An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate. The four optical elements are characterized in order from object to image as convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention increases the slit dimensions associated with ringfield scanning optics, improves wafer throughput and allows higher semiconductor device density.

Abstract: The invention relates to a slimmed-down yet high-performance image display device which comprises a decentered prism capable of internal reflection and a reflection type image display device such as a reflection-type LCD or DMD and can present bright images to an observer, and provides an image display apparatus comprising a light source 5, a reflection type image display device 3, and an ocular optical system for guiding an image displayed on device 3 into an eyeball position for forming an intermediate image 4. The ocular optical system comprises a prism member 10 comprising an entrance surface 11 and two reflecting surfaces 12 and 13. In a prism, an optical path for connecting the first surface 11 with the second surface 12 intersects a reflecting optical path from the third surface 13. The ocular optical system further comprises a back-coated reflecting surface 23 between the third surface 13 and an observer's eyeball side.

Abstract: According to one aspect of the invention there is provided a panoramic imaging arrangement comprising a transparent component and a reflective material. The transparent component has a first surface about a vertical axis of revolution, a second surface about the axis of revolution, and an opening formed therein to define a third, internal surface about the axis of revolution. The third surface has a concave profile in a plane of the axis of revolution. The reflective material is located on the second surface to provide a reflective surface against the second surface. The first surface, the reflective surface and the third surface are positioned relative to one another so that light from a 360° surrounding panoramic scene enters the transparent component through the first surface, whereafter the light is reflected from the reflective surface, whereafter the light exits the transparent component through the third surface.

Abstract: An optical element integrally has an optically acting surface, which is a rotationally asymmetric, aspherical surface, and a monitor surface for evaluation of whether the optical element is defective or not. The monitor surface is provided in a portion effecting no optical action, except for the optically acting surface.

Abstract: An optical system in which rays of light from an object pass through includes a first lens unit having at least one off-axial curved surface, a second lens unit and a third lens unit having at least one off-axial curved surface in the named order and wherein chiefly the first lens unit and the third lens unit cancel aberrations created by the off-axial curved surfaces with each other so that totally good aberration correction may be effected.

Abstract: A reflecting-type optical system according to the invention includes an optical element composed of a transparent body having an entrance surface, an exit surface and at least three curved reflecting surfaces of internal reflection. A light beam coming from an object and entering at the entrance surface is reflected from at least one of the reflecting surfaces to form a primary image within the optical element and is, then, made to exit from the exit surface through the remaining reflecting surfaces to form an object image on a predetermined plane, In the optical system, 70% or more of the length of a reference axis in the optical element lies in one plane.

Abstract: A high-performance image-forming optical system made compact and thin by folding an optical path using reflecting surfaces arranged to minimize the number of reflections. The image-forming optical system has only one prism member. The prism member has a first surface through which a light beam enters the prism member, a second surface reflecting the incident light beam in the prism member, a third surface reflecting the reflected light beam in the prism member, and a fourth surface through which the light beam exits from the prism member. At least one of the second and third surfaces has a curved surface configuration that gives a power to a light beam. The curved surface configuration has a rotationally asymmetric surface configuration that corrects aberrations due to decentration. A pupil is provided between the first and fourth surfaces, for example, on the second surface.

Abstract: An imaging apparatus for sensing an image of a scene from a substantially single viewpoint, which includes a truncated, substantially paraboloid-shaped reflector positioned to orthographically reflect principal rays of electromagnetic radiation radiating from the scene, the paraboloid-shaped reflector having a focus coincident with the single viewpoint of the imaging apparatus, including the paraboloid-shaped reflector. The imaging apparatus also includes telecentric means, optically coupled to the paraboloid-shaped reflector, for substantially filtering out principal rays of electromagnetic radiation which are not orthographically reflected by the paraboloid-shaped reflector. The imaging apparatus also includes one or more image sensors positioned to receive the orthographically reflected principal rays of electromagnetic radiation from the paraboloid-shaped reflector, thereby sensing the image of the scene.

Abstract: There is disclosed an optical system adapted for use in an image taking device. The optical system comprises an optical element having an entrance surface, a curved internal reflective surface and an exit surface on the surface of a transparent member composed for example glass, in which the light beam from an object is refracted at the entrance surface, thus being incident on the interior of the optical element, then is internally reflected by the reflective surface and refracted at the exit surface, thus emerging from the optical element and focusing on an imaging plane. The internal reflective surface is an off-axis reflective surface, and the entrance surface, the internal reflective surface or surfaces and the exit surface are so designed as to cancel the chromatic aberration generated at the refractive surfaces, while satisfactorily correcting other optical aberrations.

Abstract: A zoom lens comprises a plurality of optical elements each of which includes a transparent body having two refracting surfaces and a plurality of reflecting surfaces and is arranged so that a light beam enters the transparent body from one of the two refracting surfaces, repeatedly undergoes reflection, and exits from the other of the two refracting surfaces, and/or a plurality of optical elements on each of which a plurality of reflecting surfaces made from front surface mirrors are integrally formed, and each of which is arranged so that an entering light beam repeatedly undergoes reflection by the plurality of reflecting surfaces and exits from the optical element.

Abstract: A corrector mirror folds the optical path between the objective and relay portions of a three-mirror anastigmat. The corrector mirror is a non-powered mirror having a nominally flat but higher order aspheric surface. By placing the corrector mirror between the objective portion and an intermediate image formed by the objective portion, the field offset of the anastigmat can be significantly increased. A large field offset makes the off-axis anastigmat ideal for use with an on-axis dewar for infrared imaging applications.

Abstract: An image display apparatus which enables observation of a clear image at a wide field angle with substantially no reduction in the brightness of the image, and which is extremely small in size and light in weight and hence unlikely to cause the observer to be fatigued. The apparatus includes an image display device (6) and an ocular optical system (9) for leading an image of the display device (6) to an observer's eyeball (1). The ocular optical system (9) has a first optical element (7) and a second optical element (8). The first optical element (7) has three surfaces, and a space formed by the surfaces is filled with a medium having a refractive index larger than 1.