Abstract: A mask pattern is repetitively scan-imaged on a number of areas of a substrate by means of a beam of EUV radiation having a circular segment-shaped cross-section. This system, which is easier to manufacture at lower cost than a projection system with six or more imaging mirrors, has only five imaging mirrors with a good numerical aperture and an acceptable image-ringfield width. An EUV lithographic projection apparatus provided with the new projection system has a wafer throughput which is approximately 50% higher than that of an apparatus provided with a six-mirror projection system. Moreover, it has a compact construction.

Abstract: An integrally formed optical element includes an incident surface into which light flux from an object enters, a plurality of reflecting curved surfaces decentered one to the other from which the light flux entered from the incident surface is reflected and an emergent surface from which the light flux from the reflecting curved surfaces is emitted, wherein an antireflection film is applied onto the incident surface and the emergent surface, and wherein the light flux emitted from the emergent surface forms an image.

Abstract: An all-reflective optical system includes an entrance aperture, an exit aperture, and a dichroic beam splitter assembly. The dichroic beam splitter assembly includes an entrance dichroic beam splitter and an exit dichroic beam splitter. The reflected portion of the beam from the entrance dichroic beam splitter passes to a first beam processing array having an odd number of powered mirrors. The transmitted portion of the beam from the entrance dichroic beam splitter passes to a second beam processing array having an odd number of flat mirrors. The second beam processing array and the first beam processing array are circumferentially angularly displaced by about 90 degrees of rotation about an optical reference axis. The dichroic beam splitter assembly, the first beam processing array, and the second beam processing array together comprise a single optical unit rotatable about the optical reference axis, and a bearing set is provided to accomplish the rotation.

Abstract: A catoptric reduction projection optical system (100), a projection exposure apparatus (EX) and a method using same. The catoptric reduction projection optical system is capable of forming a reduced magnification image of an object present on a first surface (R) onto a third surface W. The system includes a first catoptric optical system (10) capable of forming an intermediate image of the object onto a second surface (IM) and comprises a first mirror pair having a first reflective mirror (M1) and a second reflective mirror (M2).

Abstract: A variable magnification optical system comprising four optical units each having a reflecting surface inclined with respect to a reference axis ray which is a ray passing from an aperture center of an aperture stop to a center of a final image plane, the variable magnification optical system being arranged to perform a magnification varying operation by moving at least two of the four optical units along the reference axis ray in such a manner as to vary an optical path length which extends along the reference axis ray from a predetermined position on an object side to the final image plane.

Abstract: An optical imaging system especially for microlithography includes a first imaging system forming an intermediate image of an object, and a second imaging system forming, on a surface, an image of the intermediate image. A reflective surface directs light from the first imaging system to the second imaging system. An aspherical corrective optical surface is located at or near the location of the intermediate image for correcting aberrations such as high-order distortion, aberrations due to accumulation of manufacturing tolerances, and spherical aberration. The first imaging system comprises a positive power refractive element and a concave mirror. The second imaging system comprises refractive elements and no concave mirror.

Abstract: An optical axis correcting system includes a first afocal optical system, an optical deflector which corrects the deviation of an optical axis of light incident upon the first optical system, a second afocal optical system, and a light convergent optical system. The optical axis correcting system satisfies (1) 3.60<.vertline.fp(I)/fN(I).vertline.<5.30, (2) 1.00<.vertline.fp(II)/fN(II).vertline.<2.41, and (3) 0.12 <r1 (II)/f<0.

Abstract: An optical element has a plurality of reflecting regions for reflecting light in succession, each of the plurality of reflecting regions comprises a curved surface, at least two of the reflecting regions has a common reflecting surface, and the optical paths of the light defined by the plurality of reflecting regions intersect with one another.

Abstract: A two-stage optical imaging system which is capable of operating in the infra red and which is compact, the system comprising an objective generally in the form of a Cassegrain system with primary and secondary mirrors A, B together with a relay C which may be reflective, refractive or refractive and diffractive, the relay C being located co-axially between the primary and secondary mirrors A, B.

Abstract: A planetary astrographic telescope of the Cassegrain type having a concave paraboloidal primary mirror and a convex secondary mirror located in the spherical zone between the primary mirror and said primary mirror's focal point. The spherical secondary mirror receives the light reflected from the primary mirror. The secondary mirror, in turn, reflects such light through an aperture in the primary mirror to a focal plane located behind the primary mirror. The spherical secondary mirror and its holder are in combination sized to be not more than twenty percent of the diameter of the primary mirror and positioned in the spherical zone of light reflected from the paraboloidal primary mirror. One embodiment of the present invention is a tube containing the concave paraboloidal primary mirror and convex spherical secondary mirror with said tube attached to and supported on a mount at a height above a support surface.

Abstract: A catoptric reduction projection optical system (8), exposure apparatus (EX) including same, and a method using same for forming in a second plane (WP) a reduced image of an object (R) in a first plane (RP). The projection optical system includes, in order along a folded optical path on in optical axis (AX), from the first plane to the second plane, a first mirror (M1) having a concavely shaped reflecting surface and a first vertex, a second mirror (M2) having a second vertex, a third mirror (M3) having a convexly shaped reflecting surface and a third vertex, a single aperture stop (AS), and a fourth mirror (M4) having a concavely shaped reflecting surface and a fourth vertex. The projection optical system also preferable satisfies a number of design conditions.

Abstract: An all-reflective optical system uses a mirror with a hole to transmit a focused laser beam to an on-axis elliptical mirror. The reflected beam from the ellipse is predominately reflected off the mirror with a hole and focused to a distant adjustable focus. This focus spot can be positioned by X-Y scanning mirrors.

Abstract: An objective lens having a doublet structure and a number of apertures of 0.7 or more and an optical pickup apparatus having the objective lens to be adaptable to a optical recording medium having a high information recording density, the objective lens being structured such that at least one side is formed into a aspheric surface and the lens elements are made of low-diffusion glass having an Abbe's number of 40 or greater.

Abstract: An illuminator system for a film scanner of the type having a linear image sensor, a film gate through which an area of film to be scanned can be positioned, and an aperture at the film gate for defining the area of film to be scanned. The illuminator system includes a light source which produces a light beam; an optical condenser between the lamp and the film gate to condense and shape the beam; and optics adapted to diffuse and direct the light beam so as to produce a uniform line of controlled diffuse illumination at the film gate. A spherical relay lens between the lamp and the optical condenser has a focal length nominally equal to a distance between the relay lens and the optical condenser to constrain the beam within the entrance pupil of the optical condenser. A spectral filter is between the lamp and the film gated to remove unwanted wavelengths of radiation from the light beam.

Abstract: A system and a method of designing and mechanical packaging of a fully integrated multifunctional multispectral miniaturized sight assembly to allow its use on hand-held man-portable units. All the subsystems of the compact sight assembly, namely, a direct view day subsystem, a CCD-based visible TV subsystem, a staring IR night subsystem, an eyesafe laser rangefinding subsystem and a display subsystem for viewing the output of the TV or IR subsystem, are aligned and use a single telescope and eyepiece in order to decrease the size of the assembly. In addition, each sight assembly subsystem operates in a first and a second field of view, preferably in a narrow field of view and a wide field of view, with wavelengths from 0.45 .mu.m to 12 .mu.m, thereby creating a very small but highly powerful sight assembly.

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 ultra-broadband ultraviolet (UV) catadioptric imaging microscope system with wide-range zoom capability. The microscope system, which comprises a catadioptric lens group and a zooming tube lens group, has high optical resolution in the deep UV wavelengths, continuously adjustable magnification, and a high numerical aperture. The system integrates microscope modules such as objectives, tube lenses and zoom optics to reduce the number of components, and to simplify the system manufacturing process. The preferred embodiment offers excellent image quality across a very broad deep ultraviolet spectral range, combined with an all-refractive zooming tube lens. The zooming tube lens is modified to compensate for higher-order chromatic aberrations that would normally limit performance.

Abstract: A variable magnification optical system comprises at least three optical units which are a first moving optical unit, a fixed optical unit and a second moving optical unit. The three optical units are arranged in that order in a propagation direction of light, and a variation of magnification is effected by a relative movement between the first moving optical unit and the second moving optical unit.

Abstract: A lens system particularly suitable for low light, high speed applications has a primary mirror (31, 51) having a spherical reflecting surface and a secondary mirror (37, 52) having a spherical reflecting surface arranged to receive light reflected from the primary mirror. Both mirrors have the same center of curvature. The lens system includes image relay lens (47, 56) and a transfer lens (35, 55) arranged to image the center of curvature to a location at the center of the aperture stop (43, 57) of the image relay lens. This relay lens may include a spherical mirror located so that its center of curvature is coincident with the center of the aperture stop, thus creating a singular optical center of curvature for the whole lens system. The relay lens may include a meniscus corrector lens (33, 41, 42) which is located close to the aperture stop and which is also concentric with the common center of curvature.

Abstract: A reflective or transmissive image display device having a light-transmissive panel to which illuminating light for illuminating pixels is applied. The light-transmissive panel has laminated glass substrates having respective first and second planar microlens arrays. The glass substrates have their thicknesses adjusted by grinding to equalize focal lengths and other parameters of the first and second planar microlens arrays to preset values. Lenses of the first and second planar microlens arrays are formed by etching recesses in fire-finished surfaces of the glass substrates and filling the recesses with a synthetic resin having a high refractive index.

Abstract: An optical image field splitting system which is adapted to allow a single camera to be used to view two or more images or object scenes of a single object or one or more images from a plurality of objects is disclosed. The optical image field splitting system includes a camera, a mirror pair, a lens, and a third mirror spaced apart from the mirror pair. The mirror pair includes a first mirror defining a first reflective planar surface and a second mirror defining a second reflective planar surface. The first reflective planar surface is oriented at a first predetermined angle relative to the second reflective planar surface. The lens is coupled to the camera and disposed in an optical path defined between the camera and the mirror pair. The third mirror defines a third reflective planar surface oriented at a second predetermined angle relative to the second reflective surface of the second mirror. An optical path length is defined between the third mirror and the second mirror.

Abstract: An apparatus for separating solar radiation into a longer wavelength component and a shorter wavelength component includes a concentrator of solar radiation, the concentrator having a focal point F.sub.1, and a mirror for selectively reflecting either the longer or the shorter wavelength component of the solar radiation spectrum. The mirror is positioned in the light path of solar radiation from the concentrator, the mirror having a focal point F.sub.2. The mirror includes a spectrally selective filter to make the mirror transparent to the non-reflected component of the solar radiation spectrum, thereby to allow the non-reflected component to pass through the mirror to a first receiver located at the focal point F.sub.1, and the mirror is appropriately curved in order to selectively concentrate and direct the reflected longer or shorter wavelength component to a second receiver located at the focal point F.sub.2.

Abstract: A dual field optical system [20] comprises an objective [A, B,] which forms an intermediate image [10] and a relay [E, F,] which transfers radiation to a focal plane [12]. The objective [A, B] comprises a primary mirror [A] and a secondary mirror [B] arranged in the form of a Cassegrain system and is rendered dual-field by the provision of an alternative primary mirror [A.sup.1 ] which is axially movable between in-use and out-of-use positions. The primary mirror [A] forms part of a housing [J] for a linear actuator [15] which is connected by co-axial rods [14] to the alternative primary mirror [A.sup.1 ] so that the system is both compact and of low mass due to symmetry.

Abstract: A liquid-filled variable focus lens unit, particularly useful in eyeglasses, comprised of a generic variable focus capsule to which a fixed-focus rigid lens is attached. The capsule has a preestablished optical power at its distance setting, which may be the same for all capsules of a given style, and a variable optical addition. The rigid lens, which is attached to a completed capsule, includes a surface having a shape related to the visual acuity of an intended user so that the combination of a generic capsule and the rigid lens results in a lens unit having a net optical power which matches the refractive prescription of the intended user at all distances.

Abstract: An optical system having a selected one of a pair of fields of view. The optical system includes a primary reflector; a secondary reflector; a refractive optical system; and a drive. The drive orients the secondary reflector to a first region in optical alignment with the primary reflector to provide the optical system with one of the pair of fields of view and for reorienting the secondary reflector to a second region out of optical alignment with the primary reflector and orienting the refractive optical system at the first region to provide a refractive optical system with a second one of the pair of fields of view. The optical system includes a detector and a second refractive optical system disposed between the first region and the detector. The detector comprises an array of detector elements.

Abstract: A FLIR system having a refractive FLIR optical configuration including a substantially spherical housing and an optical window disposed in and extending to the outer housing surface. The window aperture diameter exceeds the housing radius and is a near dome-shaped, relatively high dispersive negative lens forming a part of the FLIR optical system and is disposed adjacent a positive relatively low dispersive lens. A first optical system extends to a first housing window for receiving light and is within a hemispherical housing portion comprises an afocal lens system of a first pair of lenses, one lens disposed at a housing wall, a first mirror disposed within the hemisphere and reflecting light passing through the first pair of lenses, a second mirror for receiving the light reflected from the first mirror and reflecting the light along a path parallel to the light impinging upon the first mirror and a further plurality of lenses for transmission of the light reflected from the second mirror.

Abstract: A scanner transmits a generally collimated beam of radiation such that the beam rotates about an axis to form a conical scanning pattern. The scanner comprises a concave parabolic reflector having a geometric axis and a focus, a rotation mechanism for effecting rotation of the concave parabolic reflector about a rotation axis which is angularly offset with respect to the geometric axis of the concave parabolic reflector, an opening formed in the concave parabolic reflector proximate the rotation axis thereof, and a convex parabolic reflector disposed along the rotation axis of the concave parabolic reflector and having a focus which is approximately co-located with the focus of the concave parabolic reflector.

Abstract: A large aperture light-weight space borne telescope is provided which may be launched by a relatively small launch vehicle. A 6 to 8 meter primary telescope composed of, e.g., 30 segments arranged in two concentric rings is provided. Supplemental outer mirror segments are stowed behind and substantially perpendicular to the main mirror which is usable in the absence of supplemental mirror deployment. Deployment of outer mirrors segments provides a large aperture telescope with a large field of view. Other deployable components include a secondary mirror, a bus, deployable with respect to the optics portion, and one or more sun shade sheets or panels.

Abstract: A laser beam condensing device which can be manufactured at low cost by using reflecting mirrors which can be machined at low cost. The device is capable of condensing a laser beam to a high energy density while eliminating any optical path difference, even if the optical axis of the incident beam strays. This device includes a first and a second reflecting mirror. An incident laser beam is deflected by these mirrors in the same direction. One of the two mirrors is a toroidal mirror, while the other is a spherical, cylindrical or toroidal reflecting mirror. The mirror surfaces of the two reflecting mirrors are machined so that the second reflecting mirror can cancel out any wave front aberrations of the laser beam reflected by the first reflecting mirror.

Abstract: A wide angle large reflective unobscured system includes a primary reflective element for receiving a broad range of energy, a secondary reflective element for reflecting the energy from the primary reflective element to reimage a virtual entrance pupil at a real aperture stop. A beamsplitter element is provided for reflecting a first portion of the energy, such as visible energy, to a first tertiary reflective mirror, while transmitting a second portion of the energy, such as IR light, to a second tertiary reflector. Each tertiary reflector is capable of focusing the received energies to dual focal planes wherein a compact detector array assembly can convert the images to electronic signals.

Abstract: Telescope comprising two or more reflecting elements, wherein a light beam impinging on a first reflecting element leaves through a second reflecting element, in which the shape of the reflecting surface of the second reflecting element is concave. The shape of the reflecting surface of the first reflecting element is concave. An entrance pupil is arranged in the light path in front of the first reflecting element and the first reflecting element images the entrance pupil nearly in the focus of the second reflecting element.

Abstract: An imaging sensor has multiple fields of view of the same scene that may be selected by the user for viewing through mechanical movements. The imaging and selection are accomplished entirely with reflective optical components (mirrors) and without the use of any refractive optical components (lenses). A movable field-shifting mirror selects between a direct view and a modified-of-view image of the scene. The modified-view image is accomplished using a multi-mirror afocal telescope. Additional field-shifting mirrors may be used to select other fields of view and reference sources, as desired, or between various detectors.

Abstract: An optical projection reduction system used in photolithography for the manufacture of semiconductor devices having a first mirror pair, a second field mirror pair, and a third mirror pair. Electromagnetic radiation from a reticle or mask is reflected by a first mirror pair to a second field mirror pair forming an intermediate image. A third mirror pair re-images the intermediate image to an image plane at a wafer. All six mirrors are spherical or aspheric and rotationally symmetrical about an optical axis. An annular ring field is obtained, a portion of which may be used in a step and scan photolithography system. In another embodiment, weak refracting elements are introduced to further reduce residual aberrations allowing a higher numerical aperture. In the catoptric embodiment of the present invention, a numerical aperture of 0.25 is obtained resulting in a working resolution of 0.03 microns with electromagnetic radiation having a wavelength of 13 nanometers.

Abstract: A FLIR staring array detector system for imaging an object scene using catadioptric optics has a cold shield efficiency approaching unity. The system provides a full format image of the object scene. The catadioptric optics include reflective objective optics for providing an intermediate image of the object scene and refractive relay optics for providing the full format image. The system further includes a staring detector for receiving the full format image.

Abstract: A multiple reflection optical instrument including a housing; a main field mirror fixedly mounted on a mount which is disposed at one longitudinal end of the housing and has a light beam inlet window; an auxiliary field mirror fixedly mounted on the mount which is adjacent to the main field mirror; a light beam outlet window formed in the mount; and first to fourth objective mirrors arranged at the other longitudinal end of the housing opposite to the field mirrors, wherein an image matrix is formed on the main and auxiliary field mirrors by a plurality of reflection spots of the light beam passing through the inlet window into the housing, and a position of a center of curvature of each of the first to fourth objective mirrors, which is projected onto the main field mirror, is adjusted such that the finally reflected light beam toward the outlet window is a maximum even-numbered coming and going reflection reflected from the third objective mirror in the image matrix.

Abstract: A head-mounted image display apparatus (HMD) including an ocular optical system, which has an F-number of 1.5 to 3 and enables a flat and clear image to be observed at a view angle of up to 60.degree. or more with substantially no aberration. The HMD has at least two, surfaces and each having a concave surface directed toward the pupil. The two surfaces are disposed so that light rays from an image display device are reflected by the first surface, and the reflected light rays are reflected by the second surface and pass through the first surface to enter an observer's eyeball.

Abstract: An illumination system for an image transfer system having a gate at which an original image to be transferred can be positioned, to provide a transfer region of illumination at the gate, comprising:(a) a light source;(b) an optical assembly positioned to receive light from the light source and direct and shape the light to form a first region of illumination, the optical assembly including at least one integrator assembly which provides improved spatial uniformity of the light without diffusing the light;(c) a diffuser in the path of light from the optical assembly to increase optical divergence of the first region of illumination to form the transfer region of illumination.

Abstract: A lens system particularly suitable for low light, high speed applications has a primary mirror (31, 51) having a spherical reflecting surface and a secondary mirror (37, 52) having a spherical reflecting surface arranged to receive light reflected from the primary mirror. Both mirrors have the same center of curvature. The lens system includes image relay lens (47, 56) and a transfer lens (35, 55) arranged to image the center of curvature to a location at the center of the aperture stop (43, 57) of the image relay lens. This relay lens may include a spherical mirror located so that its center of curvature is coincident with the center of the aperture stop, thus creating a singular optical center of curvature for the whole lens system. The relay lens may include a meniscus corrector lens (33, 41, 42) which is located close to the aperture stop and which is also concentric with the common center of curvature.

Abstract: A high efficiency, high performance full color projection system. The system includes a one-to-one relay and a refractive projection lens system. The one-to-one relay combines the outputs from two different spectral image sources, such as blue and red image sources. The refractive projection lens further combines the output from a third spectral image source, such as a green image source, with the combined images from the other two image sources relayed through the one-to-one relay to produce a single output. The one-to-one relay includes three modules, a spherical primary module, a spherical secondary module and a spectral combining module. The refractive projection lens system includes a beam combiner and a projection optics.

Abstract: A line light source illuminator for a film scanner of the type having a linear image sensor, a film gate through which an area of film to be scanned can be positioned, and an aperture at the film gate for defining the area of film to be scanned. The illuminator includes a light source which produces a light beam; an optical condenser between the lamp and the film gate to condense and shape the beam; and optics adapted to diffuse and direct the light beam so as to produce a uniform line of controlled diffuse illumination at the film gate. A spherical relay lens between the lamp and the optical condenser has a focal length nominally equal to a distance between the relay lens and the optical condenser to constrain the beam within the entrance pupil of the optical condenser. A spectral filter is between the lamp and the film gated to remove unwanted wavelengths of radiation from the light beam.

Abstract: An objective has a first group of lenses with a first optical axis and a second group of lenses with a second optical axis. The optical axes are offset from and parallel to one another. A pair of Porroprisms is disposed between the first lens group and the second lens group and serves to rotate images. The Porroprisms cause a shift in optical axis, and the first and second optical axes are spaced from each other by a distance corresponding to this shift. The arrangement is such that light travelling along the optical axis of one lens group can enter the Porroprisms for reflection to the optical axis of the other lens group. The first lens group has negative refractive power while the second lens group has positive refractive power. A rhomboidal prism is located on the side of the second lens group remote from the Porroprisms and functions to cause a shift in optical axis equal but opposite to the shift caused by the Porroprisms.

Abstract: An optical system is provided for a FLIR mounted in a cylindrical turret ch has five folding mirrors, two doubling as scanning mirrors, numerous lenses with aspherical surfaces and different refractive indices, and a rotatable head mirror. Some of the lenses and mirrors being mounted on remote controlled electrically powered focusing or scanning means.

Abstract: An optical illumination system according to the present invention is provided with an optical reflector for illuminating a surface to be illuminated in the shape of arc or annulus. A reflective plane of the optical reflector is shaped in a special curved surface. Specifically, an arbitrary parabola with a first axis passing through the vertex and the focus of the parabola is rotated about a second axis passing through a point located on the opposite side of the directrix of the parabola with respect to the focus and being parallel to the directrix. The rotation of the parabola yields a parabolic toric surface. The reflective plane of the optical reflector has the curved surface constituting at least a part of the parabolic toric surface. The reflective plane so shaped reflects a light source image emitted from a light source system to illuminate the surface to be illuminated in the shape of arc or annulus.

Abstract: A multiple reflection optical instrument including a housing; a main field mirror fixedly mounted on a mount which is disposed at one longitudinal end of the housing and has a light beam inlet window; an auxiliary field mirror fixedly mounted on the mount which is adjacent to the main field mirror; a light beam outlet window formed in the mount; and first to fourth objective mirrors arranged at the other longitudinal end of the housing opposite to the field mirrors, wherein an image matrix is formed on the main and auxiliary field mirrors by a plurality of reflection spots of the light beam passing through the inlet window into the housing, and a position of a center of curvature of each of the first to fourth objective mirrors, which is projected onto the main field mirror, is adjusted such that the finally reflected light beam toward the outlet window is a maximum even-numbered coming and going reflection reflected from the third objective mirror in the image matrix.

Abstract: A catadioptric optical system includes, in succession from the object side, a first partial optical system having positive refractive power and for forming the primary image of an object, and a second partial optical system having positive refractive power and for forming a secondary image by light from the primary image, and at least one aperture stop may be provided in the optical path of the first partial optical system and at least one aperture stop may be provided in the optical path of the second partial optical system.

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 concentric optical system usable as either an imaging optical system or an ocular optical system, which has an F-number of 1.5 to 3 and enables a flat and clear image to be photographed or observed at a view angle of up to 60.degree. or more with substantially no aberration. The concentric optical system includes at least two semitransparent reflecting surfaces (2) and (3) each having a center of curvature disposed in the vicinity of a pupil (1) and a concave surface directed toward the pupil. The semitransparent reflecting surfaces are disposed so that each semitransparent reflecting surface passes each particular bundle of light rays at least once and reflects them at least once, thereby providing a flat image surface (4).

Abstract: A doublet lens is optically passively athermalized by choosing two lens materials that have approximately the same Abbe number and substantially different thermal coefficients of refractive index. The ratio of the powers of the lens elements is designed to provide the desired passive athermalization. A diffractive surface is used on one of the lens elements to correct for chromatic aberration. Because the Abbe numbers are approximately the same for the two lens materials, the chromatic correction does not significantly change with temperature. This allows the ratio of the powers of the lens elements to control the focal length of the doublet with temperature being independent of chromatic correction.

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: Pseudoscopic, dual-path optical systems employing plane mirror arrangements for cross coupling the optical paths to reverse the left and right perspectives of object space are provided. Advantageously, the cross coupled path arrangements permit the systems to be manufactured inexpensively because low-cost reflective components can be used and assembled with alignment requirements that are significantly relaxed compared with customary requirements found in uncoupled systems utilizing high-cost prisms or mirror arrangements for similar purposes.