Abstract: One or more embodiments of an optical system includes a primary mirror configured to reflect light incident thereupon; a secondary mirror facing the primary mirror configured to receive the light reflected from the primary mirror and redirect the light reflected from the primary mirror in multiple channels; and one or more tertiary mirrors of common prescriptions, configured to reflect divergent light rays incident from the secondary mirror in multiple channels.

Abstract: An afocal beam relay has first and second primary concave reflective surfaces and first and second secondary convex toroidal reflective surfaces. The centers of curvature of each of the first and second primary reflective surfaces and first and second secondary reflective surfaces lie on an axis. The first and second secondary convex reflective surfaces face toward the first and second primary concave reflective surfaces and are disposed to relay a decentered entrance pupil to a decentered exit pupil. An aspheric corrector element is disposed in the path of an input beam of light that is directed by the primary and secondary surfaces to the decentered entrance pupil. The directed beam of light between the first and second secondary convex mirrors is collimated in one direction and focused in mid air in an orthogonal direction.

Abstract: A multi-wavelength band imaging system including a beam splitter is provided, allowing image capturing means adapted to specific wavelength bands to be used such as from visible to near infrared, intermediate infrared and far infrared. The system may have a field of view of substantially (360) degrees about an optical axis of the system and may fit into a golf ball sized housing. The imaging system includes a first convex mirror and a second concave mirror. Some embodiments for imaging single or close wavelength bands and not requiring a beam splitter are equally provided. Also provided is a self-righting housing for an imaging system, for example as described above, which self-rights under the action of gravity, thereby disposing the imaging system in an appropriate orientation.

Abstract: An exposure apparatus projects a pattern of an original onto a substrate by a projection optical system to expose the substrate, wherein the projection optical system includes a mirror assembly, and the mirror assembly includes a first mirror member which has a first reflecting surface and is configured to bend an optical axis of the projection optical system, a second mirror member which has a second reflecting surface and is configured to bend the optical axis, a supporting mechanism configured to support the first mirror member and the second mirror member, and the supporting mechanism is positioned to position the first mirror member and the second mirror member while a positional relationship between the first mirror member and the second mirror member is maintained.

Abstract: An optical system includes a primary mirror of a positive-powered concave substantially paraboloidal configuration configured to reflect light incident thereupon; a secondary mirror of a negative-powered convex hyperboloidal configuration facing the primary mirror configured to receive the light reflected from the primary mirror and redirect the light reflected from the primary mirror; a positive-powered tertiary mirror configured to substantially reimage and reflect divergent light rays incident from the secondary mirror; and a powered quaternary mirror configured to receive the reimaged light rays from the tertiary mirror, and to relay the received reimaged light rays to a focal point.

Abstract: In general, in one aspect, the invention features an objective arranged to image radiation from an object plane to an image plane, including a plurality of elements arranged to direct the radiation from the object plane to the image plane, wherein the objective has an image side numerical aperture of more than 0.55 and a maximum image side field dimension of more than 1 mm, and the objective is a catoptric objective.

Abstract: An imaging optics has a plurality of mirrors to image an object field in an object plane into an image field in an image plane. The imaging optics includes a first partial objective to image the object field onto an intermediate image, and the imaging optics includes a second partial objective to image the intermediate image onto the image field. The second partial objective includes a penultimate mirror in the beam path of imaging light between the object field and the image field, and the second partial objective includes a last mirror in the beam path. The penultimate mirror images the intermediate image onto a further intermediate image, and the last mirror images the further intermediate image onto the image field.

Abstract: A chamber apparatus used with a laser apparatus may include a chamber, a beam expanding optical system, and a focusing optical system. The chamber may be provided with at least one inlet, through which a laser beam outputted from the laser apparatus is introduced into the chamber. The beam expanding optical system is configured to expand the laser beam in diameter. The focusing optical system is configured to focus the laser beam that has been expanded in diameter.

Abstract: An apparatus for measuring an image of a pattern to be formed on a semiconductor by scanning the pattern using a scanner, the apparatus including an EUV mask including the pattern, a zoneplate lens on a first side of the EUV mask and adapted to focus EUV light on a portion of the EUV mask at a same angle as an angle at which the scanner will be disposed with respect to a normal line of the EUV mask, and a detector arranged on another side of the EUV mask and adapted to sense energy of the EUV light from the EUV mask, wherein NAzoneplate=NAscanner/n and NAdetector=NAscanner/n*?, where NAzoneplate denotes a NA of the zoneplate lens, NAdetector denotes a NA of the detector, and NAscanner denotes a NA of the scanner, ? denotes an off-axis degree of the scanner, and n denotes a reduction magnification of the scanner.

Abstract: An apparatus for measuring an image of a pattern to be formed on a semiconductor by scanning the pattern using a scanner, the apparatus including an EUV mask including the pattern, a zoneplate lens on a first side of the EUV mask and adapted to focus EUV light on a portion of the EUV mask at a same angle as an angle at which the scanner will be disposed with respect to a normal line of the EUV mask, and a detector arranged on another side of the EUV mask and adapted to sense energy of the EUV light from the EUV mask, wherein NAzoneplate=NAscanner/n and NAdetector=NAscanner/n*?, where NAzoneplate denotes a NA of the zoneplate lens, NAdetector denotes a NA of the detector, and NAscanner denotes a NA of the scanner, ? denotes an off-axis degree of the scanner, and n denotes a reduction magnification of the scanner.

Abstract: An afocal beam relay has first and second primary concave reflective surfaces and first and second secondary convex toroidal reflective surfaces. The centers of curvature of each of the first and second primary reflective surfaces and first and second secondary reflective surfaces lie on an axis. The first and second secondary convex reflective surfaces face toward the first and second primary concave reflective surfaces and are disposed to relay a decentered entrance pupil to a decentered exit pupil. An aspheric corrector element is disposed in the path of an input beam of light that is directed by the primary and secondary surfaces to the decentered entrance pupil. The directed beam of light between the first and second secondary convex mirrors is collimated in one direction and focused in mid air in an orthogonal direction.

Abstract: In general, in one aspect, the invention features an objective arranged to image radiation from an object plane to an image plane, including a plurality of elements arranged to direct the radiation from the object plane to the image plane, wherein the objective has an image side numerical aperture of more than 0.55 and a maximum image side field dimension of more than 1 mm, and the objective is a catoptric objective.

Abstract: The disclosure generally relates to imaging optical systems that include a plurality of mirrors, which image an object field lying in an object plane in an image field lying in an image plane, where at least one of the mirrors has a through-hole for imaging light to pass through. The disclosure also generally relates to projection exposure installations that include such im-aging optical systems, methods of using such projection exposure installa-tions, and components made by such methods.

Abstract: An all-reflecting, non-relayed optical system having an aperture stop and an optical axis and configured to provide images of objects. The system includes a positive power primary mirror configured to receive radiation from the objects, a negative power secondary mirror configured to receive the radiation reflected from the primary mirror and a positive power tertiary mirror configured to receive the radiation reflected from the secondary mirror. The system further includes a focal plane configured to receive the radiation reflected from the tertiary mirror and to form an image of the objects. The aperture stop of the optical system is located between the tertiary mirror and the image plane. Accordingly, the image plane may be cold shielded to prevent or reduce radiation reflected from the optical elements that interferes with the desired image.

Abstract: An imaging system including a back-plane reflector having a concave aspherical reflecting surface and an outer diameter that is no greater than a first distance, with an aperture formed in the back-plane reflector, the aperture for admitting light from a field of view to the imaging system, a fore-plane reflector having a concave aspherical reflecting surface and an outer diameter that is no greater than the first distance, with an aperture formed in the fore-plane reflector, the aperture for discharging the light from the imaging system to an image plane, and a central reflector having a convex aspherical reflecting surface for receiving light from the fore-plane reflector and discharging the light from the imaging system through the aperture in the fore-plane reflector.

Abstract: An apparatus includes a first plurality of concave reflecting surfaces; a second plurality of reflecting surfaces facing the first plurality of concave reflecting surfaces such that a region is defined between the first and second pluralities; and an input for an optical beam to enter the region and an output for the optical beam to exit the region. The first and second pluralities of reflecting surfaces are arranged relative to each other so that the optical beam is re-imaged at a reflecting surface of one of the pluralities after only one reflection from a reflecting surface of the other of the pluralities and so that overlap of two or more optical beams on each of the reflecting surfaces is avoided.

Abstract: The disclosure generally relates to imaging optical systems that include a plurality of mirrors, which image an object field lying in an object plane in an image field lying in an image plane, where at least one of the mirrors has a through-hole for imaging light to pass through. The disclosure also generally relates to projection exposure installations that include such imaging optical systems, methods of using such projection exposure installations, and components made by such methods.

Abstract: A magnifying imaging optical system is disclosed that has precisely three mirrors, which image an object field in an object plane into an image field in an image plane. A ratio between a transverse dimension of the image field and a transverse dimension measured in the same direction of a useful face of the last mirror before the image field is greater than 3. In a further aspect, the magnifying imaging optical system is disclosed that has at least three mirrors, which image an object field in an object plane in an image field in an image plane. A first mirror in the beam path after the object field is concave, a second mirror is also concave and a third mirror is convex. An angle of incidence of imaging beams on the last mirror before the image field is less than 15°.

Abstract: The disclosed embodiments relate to a system and method for medium wide angle projection system. An exemplary embodiment of the present technique comprises an imaging system configured to create an image, at least one lens configured to produce a medium wide-angle representation of the image, and an aperture stop positioned to capture the medium wide-angle representation of the image from the at least one lens.

Abstract: An optical apparatus has a primary optical element having a primary spherical optical surface with a primary center of curvature, wherein the primary spherical optical surface has a peripheral portion that extends outside a usable aperture of the optical apparatus, and a secondary optical element. A mount suspends the secondary optical element spaced apart from the primary optical element, wherein the mount comprises a number of leg sections, each leg section extending between the primary and secondary optical elements. Each leg section terminates in a spherical mating surface that rests against the peripheral portion of the primary optical element. The spherical mating surface has a mating surface center of curvature that is substantially concentric with the primary center of curvature.

Abstract: An reflective imaging optical system of the far pupil type, which is applicable to an exposure apparatus using for example the EUV light, forms on a second plane an image of a predetermined area on a first plane and is provided with first to eighth reflecting mirrors arranged in an order of reflection from the first plane toward the second plane. An entrance pupil of reflective imaging optical system is positioned on a side opposite to the reflective imaging optical system with the first plane intervening therebetween; and the following condition is fulfilled provided that PD represents a distance along an optical axis between the entrance pupil and the first plane, TT represents a distance along the optical axis between the first plane and the second plane, and R represents an angle of incidence of a main light beam coming into the first plane: ?14.3<(PD/TT)/R<?2.5.

Abstract: The invention provides a decentration optical system comprising at least five optical surfaces. The optical surfaces are each decentered with respect to an axial chief ray in the Y-Z plane in the XYZ coordinate space, and at least one surface is decentered in the X-Z plane orthogonal to the Y-Z plane. At least two of the multiple optical surfaces are rotationally asymmetric surfaces, and at least one of the at least two rotationally asymmetric surfaces is a rotationally asymmetric surface having an X odd-numbered degree term.

Abstract: An imaging system including a back-plane reflector having a concave aspherical reflecting surface and an outer diameter that is no greater than a first distance, with an aperture formed in the back-plane reflector, the aperture for admitting light from a field of view to the imaging system, a fore-plane reflector having a concave aspherical reflecting surface and an outer diameter that is no greater than the first distance, with an aperture formed in the fore-plane reflector, the aperture for discharging the light from the imaging system to an image plane, and a central reflector having a convex aspherical reflecting surface for receiving light from the fore-plane reflector and discharging the light from the imaging system through the aperture in the fore-plane reflector.

Abstract: An all-reflective optical system includes a primary mirror of ellipsoidal configuration, a secondary mirror of hyperboloidal configuration facing the primary mirror, and an eye-piece that includes: a positive-powered tertiary mirror having a majority of positive power that is expected in the eye-piece and configured to substantially collimate light rays incident thereon; and a negative-powered near-flat quaternary mirror having lesser power than the tertiary mirror and configured to receive the substantially collimated light rays from the tertiary mirror, further collimate the received light rays and reflect the further collimated light rays to an exit pupil. The primary mirror, the secondary mirror and the eye-piece thereby form an afocal optical system.

Abstract: One or more embodiments of an optical system includes a primary mirror configured to reflect light incident thereupon; a secondary mirror facing the primary mirror configured to receive the light reflected from the primary mirror and redirect the light reflected from the primary mirror in multiple channels; and one or more tertiary mirrors of common prescriptions, configured to reflect divergent light rays incident from the secondary mirror in multiple channels.

Abstract: A planar light source device is provided which has high light extraction efficiency and in which a change in color tone at different viewing angles is small. The planar light source device includes, on a light emitting surface, a concavo-convex structure layer made of a resin composition. In this planar light source device, the concavo-convex structure layer has a cone, pyramid, or prism shape, and the resin composition contains a transparent resin and particles. In particular, in the planar light source device, variations in any of x- and y-chromaticity coordinates in any directions in a hemisphere on the light emitting surface are within ±0.1, the diameter of the particle is 10 ?m or less, and the amount of the particles is 1 to 40 wt % based on the total amount of the resin composition. In addition, the difference in refractive index between the particles and the transparent resin is 0.05 to 0.5.

Abstract: Various embodiments provide an optical system including an optical spectrometer, a first negative power mirror configured and arranged to receive radiation from a far-field object, a second positive power mirror configured and arranged to receive radiation reflected by the first negative power mirror, and a third positive power mirror configured and arranged to receive radiation reflected by the second positive mirror and to direct the radiation towards an entrance slit of the optical spectrometer.

Abstract: A wide-field-of-view (WFOV) optical system includes a negative optical-power primary mirror configured to receive and reflect light from an image scene; a low optical-power secondary mirror configured to receive and reflect light from the primary mirror; a negative optical-power tertiary mirror configured to receive and reflect light from the secondary mirror; and a positive optical-power quaternary mirror configured to receive and reflect light from the tertiary mirror. The primary, secondary, tertiary and quaternary mirrors are configured to maintain an effective focal length (EFL) at edges of the field of view (FOV) of the optical system to be at least equal to a center of the FOV of the optical system so that a spatial resolution of the optical system essentially remains constant across the FOV.

Abstract: Device for collecting a flux of electromagnetic radiation in the extreme ultraviolet (EUV) emitted by a source, including a main, first collector stage, with a concave collector mirror placed in front of the source at a distance of greater than 250 mm and pierced by a central hole, and a convex mirror placed behind the concave mirror level with the source and pierced by a central hole, and at least a second collector stage with a concave collector mirror placed in front of the stage and pierced by a central hole and a convex mirror placed behind the concave mirror.

Abstract: The disclosure generally relates to imaging optical systems that include a plurality of mirrors, which image an object field lying in an object plane in an image field lying in an image plane, where at least one of the mirrors has a through-hole for imaging light to pass through. The disclosure also generally relates to projection exposure installations that include such imaging optical systems, methods of using such projection exposure installations, and components made by such methods.

Abstract: A telescope has an entrance pupil region; a first concave mirror (M1) belonging to a first rotationally symmetric aspheric surface and reflecting light passing through the entrance pupil region; a second convex mirror (M2) belonging to a second rotationally symmetric aspheric surface and reflecting light reflected by the first mirror; a third convex mirror (M3) belonging to a third rotationally symmetric aspheric surface and reflecting light reflected by the second mirror; a fourth concave mirror belonging to a fourth rotationally symmetric aspheric surface and reflecting light reflected by the second mirror to an exit pupil. The first, second, third and fourth rotationally symmetric aspheric surfaces are centered on the symmetry axis of the third mirror. The first, second and fourth mirrors are centered along the first direction perpendicular to the optical axis and off-centered in a second direction perpendicular to the symmetry axis and to the first direction.

Abstract: An optical system is described herein which has a compact, all reflective design that has multiple fields of view for imaging an object. The optical system also has identical viewing directions and can have several different configurations for adding laser range finding and designating components.

Abstract: A field facet mirror for an illumination optics of a projection exposure apparatus for EUV microlithography transmits a structure of an object arranged in an object field into an image field. The field facet mirror has a plurality of field facets with reflection surfaces. The arrangement of the field facets next to one another spans a base plane. Projections of the reflection surfaces of at least two of the field facets onto the base plane differ with respect to at least one of the following parameters: size, shape, orientation. A field facet mirror results which can ensure a uniform object field illumination with a simultaneously high EUV throughput.

Abstract: An imaging optical system of the far pupil type, which is applicable to an exposure apparatus, is provided with six reflecting mirrors and forms an image of a first plane on a second plane. An incident pupil of the imaging optical system is positioned on a side opposite to the imaging optical system with the first plane intervening therebetween. A condition of ?14.3<(PD/TT)/R<?8.3 is fulfilled by a distance PD which is provided along an optical axis between the incident pupil and the first plane, a distance TT which is provided along the optical axis between the first plane and the second plane, and an angle of incidence R (rad) of a main light beam which comes into the first plane.

Abstract: A projection optics for microlithography, which images an object field in an object plane into an image field in an image plane, where the projection optics include at least one curved mirror and including at least one refractive subunit, as well as related systems, components, methods and products prepared by such methods, are disclosed.

Abstract: A projection optical system that receives light from a display element to project an image displayed by the display element onto a screen with enlargement at a varying magnification achieved by varying the projection distance to the screen has: a refractive optical system composed of one or more refractive lenses and having a positive optical power; and a concave-surfaced mirror disposed to the screen side of the refractive optical system and having a plane-symmetric reflective surface. The projection optical system includes at least one optical element designed to be movable for focusing. The projection optical system forms an intermediate image between the refractive optical system and the concave-surfaced mirror. Moreover, a prescribed conditional formula is fulfilled.

Abstract: A reflector for the lighting device and an illumination system of the projection apparatus are provided. The reflector comprises a first reflecting structure and a second reflecting structure disposed on the portion of the first reflecting structure. The reflecting surfaces of the first and second reflecting structures are formed with a distance therebetween. After the first portion of the light is reflected from the first reflecting surface and the second portion of the light is reflected from the second reflecting surface, the second portion of the light is adapted to remove the centrally dimmed area at the opening of the lighting device. Thus, the luminance performance can be improved.

Abstract: An optical system is described herein which has a compact, all reflective design that has multiple fields of view for imaging an object. The optical system also has identical viewing directions and can have several different configurations for adding laser range finding and designating components.

Abstract: A reflaxicon system comprising two or more reflaxicons, either, neither, or both of which can be formed of solid light transmitting material, is provided and described for use and implementation as objectives, relays, and beam expanders. Each reflaxicon features a central substantially cone shaped surface and a distal surface shaped like a truncated cone with both of said surfaces aligned with and symmetrically arranged around a central axis. In the system provided said central axes are aligned and form the optical axis of the system and further curvatures can be provided to any of said surfaces as well as to incident and exiting system surfaces to provide additional optical effects as required for different applications. Further, the conical surfaces forming the central reflectors can each or both be convex or concave, with ease of construction mitigating in favor of dual concave central reflectors as the preferred embodiment.

Abstract: An apparatus for measuring an image of a pattern to be formed on a semiconductor by scanning the pattern using a scanner, the apparatus including an EUV mask including the pattern, a zoneplate lens on a first side of the EUV mask and adapted to focus EUV light on a portion of the EUV mask at a same angle as an angle at which the scanner will be disposed with respect to a normal line of the EUV mask, and a detector arranged on another side of the EUV mask and adapted to sense energy of the EUV light from the EUV mask, wherein NAzoneplate=NAscanner/n and NAdetector=NAscanner/n*?, where NAzoneplate denotes a NA of the zoneplate lens, NAdetector denotes a NA of the detector, and NAscanner denotes a NA of the scanner, ? denotes an off-axis degree of the scanner, and n denotes a reduction magnification of the scanner.

Abstract: An optical apparatus is disclosed that has a convex mirror and a concave mirror with an aperture, wherein, in use, radiation from a radiation emitter passes through the aperture and is incident upon the convex mirror before being incident upon the concave mirror, the optical apparatus arranged to form the radiation into a radiation beam, wherein the concave mirror is translatable towards and away from the convex mirror or the convex mirror is translatable towards and away from the concave mirror, to adjust divergence of the radiation beam.

Abstract: Projection-optical systems are disclosed that reduce OoB radiation doses on the wafer while reducing deterioration of optical properties of the systems. An exemplary system includes a first reflector having a reflectance for light of a second predetermined wavelength, different from light of a first predetermined wavelength, that is less than a predetermined reflectance. The system also includes a second reflector having a reflectance for light of the second wavelength which is greater than the predetermined reflectance. When the reflectors in the system are classified as reflectors having a high percentage of overlap for the reflecting regions corresponding to two different points on the wafer, and reflectors having a low percentage of overlap for the reflecting regions, then, among the reflectors having a lower percentage of overlap for the reflecting regions, the most upstream reflector in the light path of the system is the second reflector.

Abstract: The invention relates to an optical system adapted to project a cylindrical, spherical, conical or other three-dimensional display surface onto every direction in the distance or receive images from every direction at such a three-dimensional imaging surface. The optical system is adapted to project a three-dimensional object surface 3 onto a full circle in the distance, and comprises at least one rotationally symmetric reflective surface 2.

Abstract: In general, in one aspect, the invention features an objective arranged to image radiation from an object plane to an image plane, including a plurality of elements arranged to direct the radiation from the object plane to the image plane, wherein the objective has an image side numerical aperture of more than 0.55 and a maximum image side field dimension of more than 1 mm, and the objective is a catoptric objective.

Abstract: An object is to provide an imaging optical system having a very simple structure that can read image while maintaining excellent image quality without suffering from significant asymmetrical aberrations. An imaging optical system for image reading is adapted to form an image of image information on a surface of an original onto a line sensor while changing a relative position of the original surface and the line sensor to allow the line sensor to read the image information. The imaging optical system includes two off-axial reflecting surfaces, and the two off-axial surfaces are a plus deflecting surface and a minus deflecting surface, or a minus deflecting surface and a plus deflecting surface disposed in the mentioned order from the original surface side, where an off-axial reflecting surface that deflects a reference axis beam clockwise is defined as a minus deflecting surfaces and an off axial reflecting surface that deflects the reference axis beam anticlockwise is defined as a plus deflecting surface.

Abstract: Provided is a compact and bright imaging optical system having a high resolution. The imaging optical system includes three reflectors composed of a first reflector (1), a second reflector (2), and a third reflector (3) that are arranged in this order on an optical path of incident ray so as not to block the incident light. In the imaging optical system, in which light beams reflected by the three reflectors form an image plane (4), a convex mirror is used for any one of the first reflector (1) and the third reflector (3) and a concave mirror is used for the other thereof, and vertexes of a triangular dipyramid (6) are defined in terms of a central chief ray (5) by an appropriate point on the central chief ray (5) that is incident to the first reflection surface, a reflection point of each central chief ray on the first to third reflection surfaces, and an image forming point of the central chief ray.

Abstract: A Mersenne reflector system using parabolic troughs as primary and secondary reflectors, in Cassegrainian and Gregorian configurations, and a Mersenne-like reflector system using truncated parabolic troughs as primary and secondary reflectors in the Cassegrainian configuration, using a variety of combinations of reflector shapes: elliptical primary and circular secondary, rectangular primary and square secondary, elliptical primary and square secondary, and rectangular primary and circular secondary. A method for constructing truncated Cassegrainian systems using truncated troughs.

Abstract: In general, in one aspect, the invention features an objective arranged to image radiation from an object plane to an image plane, including a plurality of elements arranged to direct the radiation from the object plane to the image plane, wherein the objective has an image side numerical aperture of more than 0.55 and a maximum image side field dimension of more than 1 mm, and the objective is a catoptric objective.

Abstract: An 8-mirror reflecting type projection optical system. A first reflecting image forming optical system forms an intermediate image of a first surface and a second reflecting image forming optical system forms an image of that intermediate image on a second surface. The first reflecting image forming optical system has a first reflecting mirror M1, a second reflecting mirror M2, a third reflecting mirror M3, and a fourth reflecting mirror M4. The second reflecting image forming optical system has a fifth reflecting mirror M5, a sixth reflecting mirror M6, a seventh reflecting mirror M7, and an eighth reflecting mirror M8. The first reflecting mirror M1, the fourth reflecting mirror M4, the fifth reflecting mirror M5, and the eighth reflecting mirror M8 have concave reflecting surfaces, and the seventh reflecting mirror M7 has a convex reflecting surface. One of the second reflecting mirror M2 and the third reflecting mirror M3 has a concave reflecting surface, and the other has a convex reflecting surface.

Abstract: A concave mirror optical system for a scanner and a method for compensating image distortion. In this invention, the more expensive lens assembly in a conventional optical system is replaced by a concave mirror made from simple low-cost material so that production cost and chromatic dispersion are reduced. Moreover, different magnifications can be obtained due to a difference in focusing power of the concave mirror along XY axis direction.