Abstract: An all reflective telescope system generally includes two spherical mirrors, one mild aspheric mirror and one aspheric mirror all centered about a common telescope axis and imaging on a focal surface for easy manufacture, very long focal length, wide field of view, high resolution, compact volume and low weight particularly well suited for space observations, and in a detailed form includes a sectional concave hyberboloidal primary mirror, a circular mild convex ellipsoidal secondary mirror, a sectional concave spherical tertiary mirror and a sectional convex spherical quaternary mirror for focusing an extended distant object onto a concave cylindrical focal surface having a linear array of charge coupled detectors for high resolution imagery, the telescope having high performance operation near diffraction limits and operating at detector resolution limits.

Abstract: A reflective scanning telescopic system comprises: a primary ellipsoidal mirror for collecting incoming light, a secondary hyperbolic mirror for reflecting the light collected by the primary mirror axially through the primary mirror, a tertiary ellipsoidal mirror, disposed behind the primary mirror for receiving the light from the secondary curved mirror, and a double bounce fold mirror for directing light reflected from the first fold mirror to the tertiary mirror and for reflecting light from the tertiary mirror past the first fold mirror to a light imaging system. Ideally, the telescopic system is mounted on a substantially rigid optical bench on a gimbal for supporting the optical bench and enabling the optical bench to scan in two dimensions by pivoting along roll and pitch axes.

Abstract: A reflection type imaging optical system is provided with at least one reflecting mirror, whose reflecting surface is constructed of a plurality of zone areas different from each other in spectral reflectance characteristics. Further, in the optical system, the spectral reflectance characteristics of each zone area are selected so that an incident angle providing the maximum reflectance when a ray of light of a predetermined wavelength is incident on each zone area has a value between the maximum and the minimum of the incident angle in the zone area. The reflection type imaging optical system thus provides an important advantage in practical use in that the reflection efficiency of each reflecting surface is enhanced to bring about the brightness necessary for the imaging surface.

Abstract: A monochromator for radiant X-rays is composed of a first crystal which has a first surface of incidence having a concave letter V-shaped groove and cooling means for flowing a cooling material behind the first surface of incidence along the letter V-shaped groove, and a second crystal which has a second surface of incidence having a letter V-shaped convex. A parallel pencil of X-rays which impinges on the first surface of incidence elongates to a half-ellipse on the first surface of incidence and reflects in parallel therefrom to the second surface of incidence. Then, a pencil of emissive X-rays having the same size as the initial parallel pencil of X-rays exits the second surface of incidence to become useful light. The monochromator for radiant X-rays which has a high cooling efficiency, is easy to adjust, provides a pencil of emissive X-rays stably and highly accurately. The monochromator is easy to use and economical, and allows easy maintenance.

Abstract: A beam expander suitable for use with laser machining apparatus comprises a convex paraboloidal surface 7 and a concave paraboloidal surface 8 formed from a single metal element 10. The expander has an optional zoom facility provided by a plane mirror 12, moveable along an input-output axis, for altering the position of an incident beam on the convex surface 7 thereby altering the magnification of the system.

Abstract: An automotive rear view mirror system comprises passive optical elements (which may include lenses, but must include one or an odd number of mirrors) configured to provide a wide field of view with a negative optical element having a small width dimension mounted externally and close to the body of the vehicle. In a basic embodiment, a small negative optical element, such as a convex mirror, is mounted outside the vehicle, and a larger positive optical element, such as a convex lens, is placed inside the vehicle. The optical elements are positioned to be substantially confocal, with the distance between them equal to the difference in their focal lengths, so as to cancel the curvature of field generated by the external element. The internal element magnifies the image to a size comparable to that obtained with a standard external flat mirror.

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: A method and apparatus are disclosed for laser treatment of surfaces, such as tissue. In a preferred embodiment, the invention employs a unique reflective optical delivery system which produces an improved beam intensity cross-section which reduces thermal injury, increases the precision of the tissue interaction and allows the creation of craters with decreased sizes. Reflective optics provide precise, single-layer vaporization at low power levels without thermal injury to the underlying papillary dermis. Movable optical elements focus and direct the laser beam in a scanning pattern to treat a large area of the surface.

Abstract: In an infrared (IR) microscope for a Fourier transform (FT) infrared spectrometer with a Cassegrain mirror-lens with which an incident beam (15) can be focused via a convex mirror (16) and a concave mirror (17) onto a first point-shaped region (19) on the surface of a sample (20) under an angle of incidence .beta.<60.degree.

Abstract: An all-reflective multiple field of view optical system has first (10) and a second (12) reflecting assemblies which share a common package volume in a single unit. The first (10) and second (12) reflecting assemblies rotate with respect to one another to provide multiple fields of view utilizing a common entrance pupil region (14) and a viewing plane (16). Likewise, each reflecting assembly provides a multiple field of view.

Abstract: An apparatus for measuring the position of a movable stage by the use of a laser interferometer is of a construction in which covers are provided on respective ones of a beam optical path for reference travelling toward a fixed mirror in the laser interferometer and a beam optical path for measurement travelling toward a movable mirror and temperature-controlled gas is supplied into the covers.

Abstract: A double reflector is described which comprises two spaced apart primary mirrors oriented toward a common focus. The optical system further comprises two separate secondary deflector mirrors as well as tertiary deflector mirrors for beam concentration on a common focus. Both the primary mirrors and the secondary deflector mirrors are so-called off-axis reflectors, i.e. their surface represent surface sectors of a hypothetical big aspherical mirror body. As surface sectors of a hypothetical big hyperbolic mirror, the primary mirrors are inclined at an angle with respect to the common optical axis and each disposed at a given spacing from the same in such manner that the inner marginal rays of the incident radiation which are closest to the optical axis, will converge.

Abstract: The fabrication of an off axis three-mirror telescope on only two substrates allowing two of mirrors to be formed on a common substrate, such as by means of diamond turning. The common substrate configuration is made possible by utilizing a common vertex for both the primary and tertiary mirrors so that alignment subsequent to fabrication requires placement of only two elements. In addition, all three mirrors in this invention share a common optical axis enabling an extremely simple mounting and housing design. The present invention is applicable for use in electro-optical imaging sensors operating from visible wavelengths to long infrared wavelengths. A telescope is formed by the assembly of three off-axis mirrors, including a primary mirror, a secondary mirror and a tertiary mirror. All three mirrors share a common system optical axis.

Abstract: The reflective projection system has a relatively wide field of view that comprises two concave and two convex spherical mirrors, situated in certain non-light-blocking positions with respect to one another, for deriving, with negligible image aberrations, a projected magnified or demagnified image over at least one of a range of magnification or demagnification power values between 3 and infinity that may be zoomed over this range. Such a reflective projection system, utilizing a high-power excimer laser radiation source, may be employed for ablating the surface of a substrate, such as the surface of the coating of a coated wafer, with a demagnified image of an object pattern defined by a mask, the radiation intensity of the demagnified image being sufficiently high to effect this ablation.

Abstract: A multi-spectral optical imaging system comprising first and second facing, reflective surfaces defining a single optical axis, the first reflective surface being integrally formed on a single piece of metallic material, the single piece of metallic material having a central aperture through which the optical axis extends and a plurality of elongate rib members integrally formed thereon which define therebetween a plurality of openings communicating with the central aperture; and the second reflective surface having a focus on the optical axis, whereby radiation impinging on the first reflective surface is reflected therefrom towards the second reflective surface and further reflected from the second reflective surface towards the focus; scanning element associated with the second reflective surface for causing the second reflective surface to undergo scanning motion; beamsplitting element receiving radiation reflected from the second reflective surface; and plural detectors, each operating at a different opt

Abstract: A total reflection measuring apparatus having a cassegrain mirror which has cassegrain primary mirror and cassegrain secondary mirror focuses the light which is reflected by the above secondary mirror and the primary mirror on an object of measurement. A prism which is positioned in lower part of the above cassegrain secondary mirror and a prism lift which moves the prism between a shadow behind the cassegrain secondary mirror and the object. The prism lift positions the prism in the shadow behind the cassegrain secondary mirror when visual observation is required. As a result, the clear observation of object becomes possible.

Abstract: The pre-polygon scanning path length of a raster output scanning system is reduced by replacing a required cylinder lens, or lenses, with two cylindrical mirrors. One mirror with a negative, concave surface and a second positive cylindrical mirror. The first mirror directs the light beam to the second mirror. The second mirror directs the light onto the facets of a rotating polygon to form a focused beam in the vertical axis of the polygon. The function of the two cylindrical mirrors is to act as a telephoto lens to properly focus the image of the laser at the polygon facet while reducing the total pre-polygon path length.

Abstract: A wide angle large reflective unobscured system (10) has a primary (12), secondary (14), tertiary (18) and fold (16) mirror. The primary (12) and secondary (14) mirrors act as a non-reimaging afocal telescope of the Galilean type and relay a virtual entrance pupil to the fold mirror (16) which is positioned at the system aperture stop. The fold mirror (16) directs the energy to the tertiary mirror (18) which acts to direct and focus the energy at a viewing plane. The resulting telescope provides a wide two dimensional field of view which can exceed 20.degree..times.40.degree., and operates at optical speeds about F/1.0.

Abstract: A light intensifying device for use with cameras, telescopes, and other optical devices. The lightweight device can be easily manufactured and assembled from molded components of high durability plastic. When used as an attachment with cameras or telescopes the device will provide greater quantities of of light to allow for greater magnification and better image resolution for distant objects. The device will double the amount of light and can be used in conjunction with a camera focal length doubler which doubles the focal length but decreases the light by one half.

Abstract: The invention is directed to a pancratic mirror objective system for laser focussing and especially for laser machining apparatus. The pancratic mirror objective system preferably includes a convex paraboloid mirror and an ellipsoid mirror. The ellipsoid mirror can be approximated by a toric or spherical form. The focus F.sub.1 of the paraboloid mirror P and the first focus of the ellipsoid mirror E are coincident. By rotating the ellipsoid mirror E about the axis parallel to the incident laser beam through the first focus F.sub.1, the effective image side aperture (for example K=4 to K=8) and the focal length are varied. The track control compensates for the movement of the focus F.sub.2 in laser machining apparatus.

Abstract: We describe a device for aligning optical beams that uses either an elliptically curved or a parabolically curved mirror arranged in the reflected beam path between a rotatable mirror, which is placed at the focus of the curved mirror, and the desired target. With the elliptical mirror, the device provides variable angle, fixed position of incidence of the reflected beam upon a target placed at the second focus of the ellipse. With the parabolic mirror, the device provides variable position, fixed angle of incidence of the reflected beam upon a target. Combinations of these devices may be used to solve a variety of beam steering and/or beam alignment problems. These devices are particularly useful for experiments and applications involving ultrashort optical pulses since the time of flight through either of these devices is a constant independent of the angle of incidence and the position of incidence.

Abstract: An angular viewing device is taught which enables the viewer to see, while looking downward, objects and scenery in front of him, to the right and left and also above and below the horizontal plane of the viewer's eyes. The viewing device and all of its reflective surfaces or mirrors are housed in a casing which is waterproof and also highly aerodynamically wind-resistant. The device is primarily for use as an optical visual aid for mounting on the handle bars of bicycles for forward vision purposes, safety, and easing of muscle strain associated with riding certain types of bicycles, such as English racer types.

Abstract: A mirror collimator has a larger parabolic mirror (11) and a smaller convexly shaped capture mirror (12) arranged at the concave side of the parabolic mirror and on its optical axis (27). A cut-out 15 is formed at the common focal point of the parabolic mirror (11) and of the capture mirror (12) and a photo-element (16) is arranged in the area of this cut-out (15). The capture mirror (12) is secured to the parabolic mirror (11) by at least one carrying device (17) extending alongside the cut-out (15).

Abstract: A reflecting objective system comprising three or more spherical reflecting mirrors arranged symmetrically with regard to an optical axis common thereto and has spherical aberration corrected very favorably. By using a single or plural aspherical surfaces, this reflecting objective system can be modified so as to comprise two or more reflecting mirrors and correct not only the spherical aberration but also the offaxial aberrations.

Abstract: The invention relates to an optical device providing information to the driver of a motor vehicle, which includes a concave mirror (100), located below the lowered line of vision within the field of vision of the exterior, its concavity being directed towards the driver, and an imager (200) designed to direct a light signal to the mirror (100), characterized by the fact that the concave mirror (100) is defined by an O-dome.

Abstract: A Schwarzschild optical system comprising a concave mirror having an opening formed at the center thereof and a convex mirror arranged in opposite to the opening of the concave mirror, and has a numerical aperture of at least 0.25 on the object side, the concave mirror being formed to have an aspherical surface. This Schwarzschild optical system has a relatively large numerical aperture, a relatively large departure between the centers of curvature of the concave mirror and the convex mirror, and favorably corrected aberrations.

Abstract: A reflection reduction optical system comprises a first convex reflective surface R.sub.1, a second reflective surface R.sub.2, a third convex reflective surface R.sub.3, and a fourth concave reflective surface R.sub.4 to reflect light rays from an object surface. The third convex reflective surface R.sub.3 and the fourth concave reflective surface R.sub.4 are concentrically disposed. At least one of the object surface O and an image surface I is of concave sphere with respect to the reduction projection optical system. For practical use, the object surface is formed in a concave sphere with respect to the reduction projection optical system and the image plane in a plane perpendicular to the optical axis. A mask of concave sphere, which is the object surface O, is rotated during light exposure about a center of curvature C.sub.0 thereof located on the optical axis.

Abstract: A reflecting objective system comprising three or more spherical reflecting mirrors arranged symmetrically with regard to an optical axis common thereto and has spherical aberration corrected very favorably. By using a single or plural aspherical surfaces, this reflecting objective system can be modified so as to comprise two or more reflecting mirrors and correct not only the spherical aberration but also the offaxial aberrations.

Abstract: An apparatus for a visual display in a training simulator. A projector illuminates a convex side of a spherical screen. A concave face of a spherical mirror facing the convex side of the spherical screen reflects the image on the spherical screen to a viewer. A second embodiment projects an image on a first mirror. The projected image is reflected onto a convex portion of a spherical screen. The image on the convex portion of the spherical screen is reflected to a concave mirror facing the convex face of the screen. A viewer sees the projected image on the concave mirror. The first mirror and the second mirror can be formed as one mirror.

Abstract: A system for selectably concentrating and projecting electromagnetic radiation utilizes re-entrant reflecting surfaces and multiple internal reflections. The system of the present invention comprises components having a generally-shaped primary reflecting surface which may be used in conjunction with one or more generally-shaped secondary reflecting surfaces to achieve concentration of electromagnetic radiation along the direction of the projected beam for specified spatial radiation and collection patterns.

Abstract: An all reflective multiple field of view optical system has a first (10) and second (12) objective assembly sharing a common eyepiece assembly (16) in a common packaging volume in a single unit. The second objective assembly is movable with respect to the first to provide multiple fields of view utilizing a common entrance pupil region (18) and viewing exit pupil plane (20).

Abstract: The present optical system (20) provides an all-reflective vehicle rear vision optical system. A planar mirror (22), acting like a conventional vehicle rearview mirror, would be positioned to receive a beam. The beam would be provided by an image erecting assembly (30) which, in turn, would reflect the beam into a three-mirror anastigmat telescope (24, 26 and 28) to provide rearward image beam to the first planar mirror and in turn, to the exit pupil (25). The optical system provides a 2X magnification at a wide field of view which substantially eliminates blind spots.

Abstract: Optical mirror systems are provided by cooperative arrangements of a plurality of curved mirrors, preferably of approximately elliptical and hyperbolic shapes. In one arrangement, a convex segment of an hyperbolic primary mirror and a concave segment of an hyperbolic secondary mirror form a forward looking magnification system. In another arrangement, a concave segment of an elliptical primary mirror and a convex segment of an hyperbolic secondary mirror form a microscope.

Abstract: A projection reflection optical system has two mirrors in a coaxial, four reflection configuration to reproduce the image of an object. The mirrors have spherical reflection surfaces to provide a very high resolution of object feature wavelengths less than 200 .mu.m, and preferably less than 100 .mu.m. An image resolution of features less than 0.05-0.1 .mu.m, is obtained over a large area field; i.e., 25.4 mm .times.25.4 mm, with a distortion less than 0.1 of the resolution over the image field.

Abstract: An integrally-formed optical imaging system including at least two facing, reflective surfaces defining a single optical axis and formed on a single piece of material.

Abstract: The present invention is directed to a light transmitting lens for transmitting substantially all of the light emitted by a light source, such as a light emitting diode. The light transmitting lens includes a light transmitting structure having an outer surface disposed between first and second sides. Located on the first side is a tubular concave surface, preferably terminated by a hemispherical convex lens. Located on the second side is an opening, preferably a spherical surface. Located within the opening, preferably at the center of the spherical surface, is the light source, preferably a light emitting diode. Some of the light emitted by the light source is captured by the convex lens and transmitted thereby. The light emitted by the light source but not captured by the convex lens is reflected off the outer surface of the structure and thereby transmitted.

Abstract: An optical mirror is kinematically mounted at its sides on one fixed point and two movable points which points are supported by a frame spaced from the mirror. One of the movable points is a ball on a cantilevered arm which rests in a cone or groove in the mirror, the other movable point is a mechanical flexure prelaod mounting or a pneumatic preload mounting, which mountings serve to apply constant preload to such mirror. The mirror is made of ceramic material, of low thermal expansion or contraction and has water cooling passages therein. The frame is made of metal of higher thermal expansion or contraction. However such mirors, when reflecting a high intensity laser beam can thermally expand relative to the frame and must do so with minimal deformation from the desired optical contour thereof which result is accomplished by the resilient and constant preload mountings of the present invention.

Abstract: An endoscopic mirror laser beam delivery system, e.g., for laser surgery, comprises a beam splitting module (22) for optical connection to a laser beam source (14) which supplies a low-power aiming beam (12) and a high-power surgical beam (10) to the splitting module (22); a two-mirror focusing unit (24) optically connected to the splitting unit (22); and an endoscopic tube (20) for guiding the beams focused by the focusing unit (24) to a target point (P). The system also comprises a method for checking alignment of the optical system by observing the positions of two visible beam spots. In case of misalignment, these two spots do not coincide in a single point, thereby indicating misalignment which can be then corrected. The system and the method eliminate central obscuration and misalignment of the laser beams on an operation site, thereby enabling a surgeon to be able to be confident that the surgeon beam will impinge precisely upon the spot delineated by the aiming beam.

Abstract: An optical system (10) for producing dual fields of view simultaneously. The system (10) includes a first optical system (12) for producing a first field of view image and a second optical system (36) for producing a second field of view image where the angular displacement of the second field of view is different from that of the first field of view. A dichroic beamsplitter (22) is disposed in the present invention so as to reflect light from the first optical system (12). The dichroic beamsplitter (22) is also disposed so as to simultaneously transmit light from the second optical system (36). As a result, the reflected light (20) is primarily composed of light of a first wavelength band and the transmitted light is primarily composed of a second wavelength band. The light from the two different fields of view are then directed to a dual filter (32) which passes the first wavelength band in one portion and passes the second wavelength band in another portion.

Abstract: A spectral imaging system having an integrated filter and photodetector array. The filter has narrow transmission bands which vary in frequency along the photodetector array. The frequency variation of the transmission bands is matched to, and aligned with, the frequency variation of a received spectral image. The filter is deposited directly on the photodetector array by a low temperature deposition process. By depositing the filter directly on the photodetector array, permanent alignment is achieved for all temperatures, spectral crosstalk is substantially eliminated, and a high signal-to-noise ratio is achieved.

Abstract: In a Schwarzschild optical system comprising a concave mirror having an aperture at its center and a convex mirror disposed in face of the concave mirror, the convex mirror is coated with a multilayer film such that an incident angle .theta.02 on the convex mirror at which reflectance is maximized with respect to light of a particular wavelength satisfies the following condition:By such structure, the Schwarzshild optical system of the present invention provides an important advantage in practical use that transmittance efficiency is extremely favorable..alpha.(.theta.02, N.A.).gtoreq.0.5 .alpha..sub.max.theta.1 .sub.min <.theta.01<.theta.1.sub.

Abstract: A reflecting objective system comprising three or more spherical reflecting mirrors arranged symmetrically with regard to an optical axis common thereto and has spherical aberration corrected very favorably. By using a single or plural aspherical surfaces, this reflecting objective system can be modified so as to comprise two or more reflecting mirrors and correct not only the spherical aberration but also the offaxial aberrations.

Abstract: The present optical system provides an all-reflective zoom optical system (10, 12, 14,16 and 60, 62, 64). An imaging mechanism including one or more movable mirrors (12, 14, 16 and 60, 62) is utilized to effect the change in the magnification, field of view or both of the system.

Abstract: An unobstructed four-mirror telescope having tilted components for astronomical observations. Favorite focal ratios are in the range of about F/12 to F/20 and all surfaces are rotationally symmetric. The systems off improved aberration correction and it is possible in special cases:to realize all-spherical 500mm-systems.to eliminate image plane tilt.to eliminate anamorphic distortion.to realize big diffraction limited fields (.phi.>100mm) free from coma, astigmatism and spherical aberration.

Abstract: A method of patterning a photoresist layer to provide an aperture having retrograde sidewalls is described. Illumination may be through a conical prism arrangement or a conical reflecting mirror and cylindrical mirror arrangement. The method includes the step of directing energy towards a mask which selectively exposes portions of a photoresist layer disposed on the substrate. The energy is directed to the mask at an oblique angle with respect to the normal to the surface of the substrate. The underlying photoresist layer is obliquely sensitized by the obliquely directed illumination. The portions of the layer which are obliquely sensitized are removed leaving behind an aperture having retrograde sidewalls. The retrograde sidewalls are a preferred photoresist profile for easy and reliable lift-off of deposited material from the semiconductor substrate.

Abstract: The imaging and illumination system with aspherization and aberration correction by phase steps includes two transparent phase plates within the optical train of a stepper illumination system. The first plate places each ray at the corrected position on the axial stigmatism plate to satisfy the sine condition. The second plate, which is the axial stigmatism plate, ensures that each ray of light focuses at the focal point. The aberration corrected light is reflected by a deformable mirror toward a secondary mirror, a primary mirror and finally onto a wafer to project a single field of large dimension. The secondary and primary mirrors provide aspherization by forming phase steps in the surfaces of the mirrors. The deformable mirror, to permit realtime correction of aberrations and manipulation of the beam for each field imaged by the system. A set of two-dimensional scanning mirrors is placed between the laser light source and a reticle containing to pattern which is to be transferred to the wafer.

Abstract: The present optical system provides an all-reflective afocal reimaging system. A reflective system receives, by means of an entrance aperture, and reflects radiation or light through the system such that the radiation or light is imaged and recollimated as it is reflected through the system. The radiation or light exits at an exit aperture which is an image of the entrance aperture. High quality images of both the collimated scene and reimaged aperture are formed by the optical system. Embodiments are shown by which the optical system can be used as an optical derotation device by the inclusion of two planar mirrors located near the entrance and exit apertures.

Abstract: A reflecting imaging optical apparatus comprises a reflecting spherical optical system including a first spherical reflecting optical system and a second spherical reflecting optical system, and a spherical reflecting mirror disposed near the position of an intermediate image formed by the reflecting spherical optical system. The first and second spherical reflecting optical systems form concentric optical systems, respectively.

Abstract: A cassegrain optical system provides improved collection of off-axis light yet is still characterized by a high concentration ratio. The optical system includes a primary mirror for collecting incoming light and reflecting the light to a secondary mirror which, in turn, reflects the light to a solar cell or other radiation collection device. The primary mirror reflects incoming on-axis light onto an annular section of the secondary mirror and results in the reflection of a substantial amount of incoming off-axis light onto the remainder of the secondary mirror. Thus light which would otherwise be lost to the system will be captured by the collector. Furthermore, the off-axis sections of the secondary mirror may be of a different geometrical shape than the on-axis annular section so as to optimize the amount of off-axis light collected.

Abstract: Disclosed is apparatus, exemplarily semiconductor X-ray lithography apparatus, that comprises a novel projection system. In preferred embodiments the projection system is adapted for use with radiation of wavelength below about 30 nm. The system comprises four or more mirrors that form a finite conjugate "optical" system that is telecentric at the short conjugate. The mirrors can be selected such that an essentially flat, diffraction limited image is formed. The image field can be two-dimensional, exemplarily a 10.times.10 mm square, and the resolution over the image field can be higher than 0.25 .mu.m.Exemplarily, the "optical" system comprises, from long to short conjugate, a convex, a concave, a convex, and a concave mirror, with at least two of the mirrors being aspherics. The radius absolute values of the four mirrors are, in the above order and as a fraction of the system focal length, 2.20, 2.59, 2.51, and 2.13 all to within .+-.5%.