Abstract: A multiple instrument distributed aperture sensor (“MIDAS”) science payload system mounted on a spacecraft, including a spacecraft interface ring affixing the MIDAS science payload system to the spacecraft, and a multiple telescope array (“MTA”) further including a mechanical subsystem further including an optical bench, an optical subsystem mounted upon the mechanical subsystem collecting light and merging the light into a passive, actively-sensed or hyperspectral image, and a laser subsystem providing laser illumination for collecting active remote sensing data. The MIDAS science payload system also includes a hexapod in physical communication with and between the spacecraft interface ring and the mechanical subsystem.

Abstract: A telescope has a joint for universally bearing an optical assembly in relation to a housing. The joint is designed as an elastic spring joint.

Abstract: A laser scanner, comprising a mirror rotatably provided, a driving unit for rotating the mirror, a distance measuring unit for projecting a distance measuring light for scanning to a measurement range via the mirror and for obtaining a position data by receiving the reflected distance measuring light via the mirror, a measuring direction observing means for indicating a projecting direction of the distance measuring light, and an operation unit for setting the measurement range by designating at least two measuring directions based on the result of observation of the measuring direction obtained by the measuring direction observing means.

Abstract: An apparatus for enhanced viewing of objects in two separate simultaneous frequency bands of light that is constructed in accordance with the principles of the present invention includes a primary mirror and a moveable secondary mirror that is disposed above the primary mirror to provide a long focal length. A beam splitter splits the optical path into two paths, one for infrared and another path for visible. Various optical elements and devices are described along each path. The secondary mirror is displaced away from its concentric position over the primary mirror to provide shorter focal lengths in IR and visible. Focal Plane Arrays (FPA's) are disposed where desired along both optical paths for real-time viewing and data acquisition. The preferred FPA in visible is a CCD. The preferred FPA in IR is disposed in a Dewar.

Abstract: A beam shaping telescope includes two mirrors having rotationally symmetric curvature inclined to the optical axis of the telescope. By selecting an appropriate curvature, spacing, and inclination of the mirrors, the telescope can be used to transform an astigmatic laser beam having a non-circular cross section into a circular beam having essentially zero astigmatism.

Abstract: A Schiefspiegler telescope with three reflecting surfaces, preferably for observing the earth from space, particularly for imaging radiometers. A novel possibility for realizing a reflector telescope without vignetting which permits a simple construction and a simple adjustment of the reflecting surfaces relative to one another. In a Schiefspiegler telescope with three reflecting surfaces whose mirror axes are arranged within a plane, the primary reflecting surface and tertiary reflecting surface are convex surfaces of identical shape arranged symmetrically with respect to an axis of symmetry. The secondary reflecting surface is arranged symmetric to the primary reflecting surface and tertiary reflecting surface so as to be rotationally symmetric around the axis of symmetry so that all three reflecting surfaces have an axially symmetric mirror arrangement with respect to design in which the optical imaging is transmitted to a receiver in the manner of an off-axis telescope.

Abstract: A display device (4) for a telescope system is disposed between a first image plane (10) and a second image plane (20) of the telescope system. The display device includes a signal emitter (41), a converging lens group (42) positioned adjacent to the signal emitter, and a dioptric imaging lens group (43) positioned adjacent to the converging lens group. The optical signal emitted by the signal emitter is first transmitted through the converging lens group, then incident onto the dioptric imaging lens group, and finally imaged onto the second image after reflection of the dioptric imaging lens group. Therefore, both the image size and brightness of the displayed signal viewed by the observer can maintain unchanged in spite of the magnification variation of the telescope system.

Abstract: A method for eliminating internal reflection signal in a range finding system is disclosed, including the steps of receiving a range-finding signal reflected by an object and an internal reflection signal caused by internal reflection of the range finding system, converting the range finding signal and internal reflection signal, as a combination, into an electrical current signal, cropping the electrical current signal in a time interval for the electrical current signal to pass so as to generate a first electrical signal indicating the internal reflection signal, and subtracting the first electrical signal from the current signal to provide a second electrical signal representing the range-finding signal reflected by the object.

Abstract: The present invention relates to a remote-controlled telescope lens cover and a telescope fitted with the same.

Abstract: The present invention provides a telescope system having enhanced capabilities for configuring and calibrating a telescope, operation and control of the telescope, and viewing of imagines from the telescope. The present invention employs a control system for controlling the position and orientation of the telescope. In one embodiment, the system uses GPS systems and the like to determine the position of the telescope. The system may use either the light detected by the telescope or measurements of stars within the field of view to determine the orientation of the telescope. Following calibration, the user may operate a control system to reorient the telescope to the desired field of view. Further, the user may operate software that allows the user to select stars, constellations, or other objects of interest. Based on this selection, the system operates the telescope to alter its field of view to view the selected object.

Abstract: An optical system includes two lens systems, one that provides viewing of an object with relatively no spherical aberration, and another that provides viewing of the object with significant spherical aberration. Preferably, both lens systems provide viewing of the object with relatively no chromatic aberration. The optical system may have the configuration of binoculars.

Abstract: High-resolution imaging systems are provided. In one embodiment, an imaging system based on a Cassegrain or Schmidt-Cassegrain objective, with coaxial primary and secondary mirrors, is provided with a microdisplacement mechanism acting on the secondary mirror to displace the image on a focusing array. In another embodiment, two co-axial Cassegrain-type objectives are provided one within the other with a common focal plane array, which therefore detects combined wide field-of-view and narrow field-of-view images.

Abstract: A geodetic total station comprising an upper part (1a) provided with a support (2) with at least one support section (2a; 2b), an electronic display control unit (4), a total station data interface (6) provided with electrical contact elements (6a), and a top attachment (20) that is mechanically coupled above the support (2) and the telescope (3), in a detachable manner, by means of at least one mechanical support interface (8a; 8b) and at least one corresponding mechanical top attachment interface (21a; 21b). The total station data interface (6) is arranged on the support section (2a; 2b), and the top attachment (20) receives the peripheral components and has a top attachment data interface (23) which comprises electrical contact elements (23a) and is connected to the peripheral components in a data-transmitting manner.

Abstract: Binoculars having a center-focusing function and an individual-focusing comprise a telescopic base provided at an end thereof with a control sleeve which is connected to a left lens system in a left barrel and a right lens system in a right barrel through an adjusting portion disposed in the telescopic base. When a user pushes the control sleeve so that the control sleeve is forced to shift toward the adjusting portion, the user can rotate the control sleeve to simultaneously actuate the adjusting portion, so as to adjust focuses of the left and right lens systems. When the user pulls the control sleeve so that the control sleeve is forced to shift away from the adjusting portion, the user can rotate the control sleeve to simultaneously actuate the adjusting portion, so as to adjust a parallax between one and the other of the left and right lens systems.

Abstract: An automatic telescope (10) capable of determining an orientation without requiring input from a user or any external source. The telescope (10) preferably includes a database (22) to store astronomical information, a processor (24) to control a drive mechanism (18), a vision device (30) to sense bright stars, and a motion sensor (32) to generate a motion signal. When the vision device (30) is slewed from alignment with a first bright star to a second bright star, the motion signal is preferably representative of a measured angle between the first and second bright stars. This process is preferably repeated for several bright stars to generate several measured angles. The processor (24) can then use the measured angles to identify the bright stars and determine the orientation of the telescope (10).

Abstract: An optical system resembling a modified Gregorian astronomical telescope is disclosed in the specification and drawings. Lenses are used in the inter-focal region to modify the optical characteristics of the system. The use of such inter-focal lenses, can, for example, flatten the image plane of the field thereby increasing the field of view of the telescope.

Abstract: A portable astronomical telescope includes the cylinder body, on which three telescopic legs are hinged through a joint to form a tripod stand. The bottom of aforementioned cylinder body is fixed by means of connection element and mounted with part box. On the bottom end of this part box, a bottom cover is insert-mounted. On the upper end of the part box, limit connection elements of the connected telescopic leg are hinged. Within the aforementioned cylinder body, a guide bush is fixed and installed, inside of which machine base is mounted. On the side of this machine base; a guide pin is established. On the side of the guide sleeve, an L-shaped feed-through slot is established to accommodate the guide sleeve. On the tail end of the above feed-through slot, one guide pin residence slot is connected. The aforementioned machine base is activated by the lug and mounted with bellows. This product can be used without need for separate assembly, and eliminates the need for a separate package.

Abstract: A common-aperture optical system includes a reflective telescope having a common boresight, an entrance pupil, an exit pupil, and a beam path extending from the entrance pupil to and beyond the exit pupil. A beam splitter intersects the beam path so that the beam path is incident upon the beam splitter. A light sensor is positioned to receive an input light beam traveling along the beam path after the beam path intersects the beam splitter and passes the exit pupil of the reflective telescope. A light source produces an output light beam incident upon the beam splitter and positioned to inject the output light beam into an inverse of the beam path and toward the entrance pupil of the reflective telescope. A diverger corrects at least one of the input light beam and the output light beam.

Abstract: A surveying instrument (11) comprises a telescope unit having imaging optics and an array of optical detector elements, orientation sensors detecting an orientation of the telescope unit, rotation drives for rotating the telescope unit about a horizontal and a vertical axis, a controllable distance-measuring unit, and a processing unit. The processing unit comprises a memory storing instructions and calibration data for relating the location of each optical detector element to a sighting direction and a processor for: obtaining target region data; obtaining projection surface data (133) representing a projection surface (135), acquiring a set of pixel data representing a two-dimensional image of a target region, transforming the set of pixel data to a set of projected image data representing a projection of the image to the projection surface using the calibration data, and storing the projected image data as surveying data.

Abstract: A telescopic tube includes an upper section tube and a lower section tube that are provided coaxially with each other. A plurality of connecting rods is provided between the upper and lower section tubes in parallel to the axis of the tube. Via the connecting rods, the upper section tube or the lower section tube can slide telescopically in the axial direction of the tube, thereby extending or retracting the tube.

Abstract: An optical system for the magnification of an object presented to an image receiver. The optical system includes a frame configured to position at least one optical element between the object and the image receiver. The optical element includes a plurality of Galilean telescopes supported on a substrate, each Galilean telescope being composed of a positive lens and negative lens, the positive lens being further distanced from the image receiver than the negative lens when the object element is positioned between the object and image receiver. Each of the Galilean telescopes has an axis substantially parallel to the axis of the other Galilean telescopes in the optical system such that light passing through each of the plurality of Galilean telescopes is substantially collimated. Ideally, each negative lens is positioned on a substrate to be on a spherical radius whose center of curvature is substantially at the image receiver.

Abstract: A rifle scope has a front end receiving light and a rear end passing light to the user eye. The rifle scope has an elevation adjustment; an inside body is hollow and tubular and fitting inside a middle body which is also hollow and tubular shaped and a top angle focus adjustment mounted on the inside body in front of the elevation windage. The top angle focus adjustment has a top angle focus knob, a focus shaft mounted to the focus knob, and a top angle gear mounted to the focus shaft. The top angle focus knob and the focus shaft and the top angle gear are fixed so that they rotate together on an axis of the focus shaft. The inside body focus gear housing has an inside body focus gear meshing with the top angle gear, and the top angle gear rotation rotates the inside body focus gear.

Abstract: An apparatus has structure with a reticle oriented approximately parallel to and adjacent an imaginary plane. The structure includes on one side of the plane a portion transmissive to visible radiation, the portion having a surface that is spaced from and angled with respect to the plane, and that faces away from the reticle. A reticle illumination section emits radiation adjacent the surface. According to a different aspect, a method involves: providing a reticle oriented approximately parallel to an imaginary plane and disposed immediately adjacent the plane; providing on one side of the plane a structural portion that is transmissive to visible radiation; forming on the portion a surface spaced from the plane, oriented at an angle to the plane, and oriented to face away from the reticle; and emitting radiation adjacent the surface.

Abstract: An imaging optical system includes a subtelescope array, with at least two subtelescopes, each having a single entrance pupil and an exit light beam. Each subtelescope has an optical pointing axis, and the pointing axes for the subtelescopes are parallel. An imager forms an image from the exit light beams at an image surface, where there is a sensor such as a focal plane array. Preferably, a phase shifter array includes a phase shifter for each of the subtelescopes. The phase shifter array receives the exit light beam of each of the subtelescopes and has a capability to adjust the phase of at least one of the exit light beams. The imager receives the phase-shifted exit light beams.

Abstract: An automatic telescope (10) capable of determining an orientation without requiring input from a user or any external source. The telescope (10) preferably includes a database (22) to store astronomical information, a processor (24) to control a drive mechanism (18), a vision device (30) to sense bright stars, and a motion sensor (32) to generate a motion signal. When the vision device (30) is slewed from alignment with a first bright star to a second bright star, the motion signal is preferably representative of a measured angle between the first and second bright stars. This process is preferably repeated for several bright stars to generate several measured angles. The processor (24) can then use the measured angles to identify the bright stars and determine the orientation of the telescope (10).

Abstract: A telescope includes an objective lens to receive an optical signal from an object and an electronic signal generator that generates an electronic signal representing for example distance and direction of the object. Both signals travel through a magnification system to from images on a viewer side image plane. The image representing the electronic signal is further transmitted, before reaching the image plane, through a reflector prism, by which the image of the electronic signal is maintained invariable with respect to the variation of magnification factor of the telescope.

Abstract: A laser riflescope includes a laser emitter, a laser receiver, an objective lens group (11) for collecting the visible light from the target to be measured, an eyepiece group (14) adapted for observation by the user of the distance information of the target and defining an optical axis with the objective lens group, a prism group (12) disposed between the objective lens group and the eyepiece group for light beam transmission, and a display element (13) for displaying the distance information of the target. The display element is an OLED having high transmittance to enhance the display brightness of the laser riflescope.

Abstract: A telescope adapter for supporting a camera includes a light beam splitter for receiving light from the telescope and dividing that light into a monitoring bundle of light rays and a recording bundle of light rays, the two bundles of light rays being at angle to each other. The user is permitted to view the monitoring bundle of light rays, and the adapter can support a camera in a position to receive the recording bundle of light rays, so that the user and the camera can receive light from the telescope simultaneously. A first lens system is located between the telescope and the light beam splitter, the first lens system having a total negative power. A monitoring lens system receives and transmits the monitoring bundle of light rays leaving the light beam splitter, and a recording lens system receives and transmits the recording bundle of light rays leaving the beam slitter, both the monitoring and recording lens systems having total positive power.

Abstract: High-resolution imaging systems are provided. In one embodiment, an imaging system based on a Cassegrain or Schmidt-Cassegrain objective, with coaxial primary and secondary mirrors, is provided with a microdisplacement mechanism acting on the secondary mirror to displace the image on a focusing array. In another embodiment, two co-axial Cassegrain-type objectives are provided one within the other with a common focal plane array, which therefore detects combined wide field-of-view and narrow field-of-view images.

Abstract: In an observation device according to the invention, it is possible to coordinate a multiplicity of functions with the device by using and exchanging optical modules. By means of existing optical components in the observation device, transmitted and/or received beams of the modules can be reflected in and/or reflected out. For example, field glasses, binoculars and measuring glassed can be equipped according to the invention with modules. The modules can be produced for special purposes, can be carried in particular as convenient units and can be inserted into the device and removed therefrom an can be exchanged. An optical module may be, for example, in the form of a camera, graphic display or IR laser. The modular multifunctional observation device according to the invention can be designed as a compact and light device by using optical components already present in the “basic system.

Abstract: An image combining viewer transmits a daylight image directly through the viewer, while reflecting at least one wavelength other than visible light towards a sensor. A display for displaying the image received by the sensor in a visible wavelength is reflected by the back surface of the mirror back along the optical path, combining the displayed image with the daylight image so that they appear to be a single image.

Abstract: Embodiments of the present disclosure include presenting data related to image information captured by a telescope on an electronic display, such as, for example, a high definition display. For example, a telescope control system may advantageously output video or other signals to one or more displays in a multi-media or image presentation. In certain preferred embodiments, such display comprises high definition displays, or the like. For example, such display may comprise entertainment, academic or other presentations.

Abstract: A scanning wide-field telescope includes a primary reflecting mirror and a corrector assembly. The corrector assembly corrects light beams for spherical aberration imposed on the light beams by the primary reflecting mirror. The corrector assembly is located between the primary reflecting mirror and a viewing end of the telescope, and is configured to move to multiple optical focal points of the primary reflecting mirror.

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

Abstract: A high precision, high performance optical system and beam pathway design for laser-based distance measuring, or range-finding, devices includes an etched, or etched and filled, aiming reticle in the image plane which does not require daytime use illumination, and only minimal auxiliary illumination during nighttime operation, thereby conserving available battery power. In a preferred embodiment, a low power consuming back-lit liquid crystal display provides high contrast distance or other operational information to a user superimposed upon a black-appearing field stop thereby further providing operational power savings.

Abstract: The light of a broad energy band can be observed by reflecting the light of the broad energy band, for example, the light from the visible light region to the x-ray region at a high reflectance respectively, by a composite telescope including a normal incidence optical system and an oblique incidence optical system. A broadband telescope comprise an oblique incidence optical system unit in which the light is obliquely incident on a surface part for reflecting the incident light, a normal incidence optical system unit in which the light is substantially vertically incident on a surface part for reflecting the incident light, and an analyzer for spectrum analysis of the light reflected by the surface part of the obliquely incidence optical system unit and the light reflected by the surface part of the normal incidence optical system unit.

Abstract: In a first exemplary embodiment of the present invention, an optical device comprises a telescope and a pipescope arranged as a spatial filter to light propagated through the telescope, to confine a field of view to ?DL.

Abstract: Disclosed is a light collimating system for mounting at the primary focus of a Schmidt-Cassegrain telescope (SCT) in place of the secondary mirror. The system comprises a housing containing a plurality of lens elements optimized to reduce optical aberrations. The resulting system has a focal ratio of approximately f/2, a short exposure time for optical imaging, and a wide field of view with very little distortion. The housing is attached to the corrector plate of the SCT by a pair of rings held together by a plurality of screws that further facilitate the alignment and rotation of the light collimating system.

Abstract: A multi-telescope imaging system includes a first telescope and a second telescope, each telescope having an input line of sight, a ray path that is incident upon a focal surface imaging location at a non-normal angle of incidence, and a shutter lying on the ray path. A single common sensor lies at the focal surface imaging location, such that the first-telescope ray path and the second-telescope ray path are alternatingly incident upon the same focal surface imaging location of the sensor. A shutter controller alternatingly opens and closes the two shutters, so that the sensor alternatingly views the scenes imaged by the two telescopes.

Abstract: A structureless space telescope is disclosed. The structureless primary mirror includes a plurality of mirror elements for focusing and reflecting electromagnetic radiation, and the telescope further includes at least one secondary mirror and possibly a tertiary mirror for receiving the focused and reflected electromagnetic radiation from the structureless primary mirror and reflecting the electromagnetic radiation, and at least one focal plane array for receiving the focused and reflected electromagnetic radiation from the secondary mirror or tertiary mirror, wherein the plurality of mirror elements, the secondary mirror and the focal plane array are coordinated and controlled without a physical structure connecting the plurality of mirror elements.

Abstract: A hand-held telescope or binocular built into a bottle or consumable drink container includes a high quality objective lens; an adjustable focus eye lens; and, optionally, a connector ring to form a binocular; a jacket, sleeve or cuzzi containing information regarding, for example, sporting or scientific events; a baffle to minimize extraneous light from disturbing observational clarity; and a holographic bottle label that portrays sporting or scientific figures in three dimensions.

Abstract: At least three incoming light beams (10a-c) are combined partly combined into a null beam and partly into fringe tracking beams. The relative phase difference between the incoming beams (10a-c) is controlled so that a phase relationship between in the null beam corresponds to destructive interference of the main beam components in the null beam. In the fringe tracker beams this leads at least partly to constructive interference between the main beam components, with an intensity that depends on the phase differences. Measurements of the intensities of the fringe tracker beams are used to control the relative phase differences of the incoming beams (10a-c) to realize destructive interference of the main components in the null beam. To form the null beam successively more of the light beams are combined into the null beam in a series of beam combiners (14a, 14 b).

Abstract: An apparatus for the focusing of incident light includes a base assembly that is adapted to support a primary mirror. The primary mirror includes an outside circumference and an inside aperture. An upright member is attached to the base assembly at a first end thereof at a first location that is disposed inside the aperture and at a second location that is disposed outside the primary mirror. The upright member includes a second end that is distally disposed with respect to the first end. The second end is adapted to receive a turret that includes a secondary mirror and is adapted to pivot between two positions. An IMU is attached to the base assembly proximate the primary mirror.

Abstract: An optical sight includes an optical train having an optical path therethrough, an entrance, and an exit. A reticle is visible through the exit of the optical path. An unpowered reticle illumination source has a first light source that illuminates the reticle responsive to the level of ambient light, and a second light source that illuminates the reticle with an unpowered light source. The reticle illumination source preferably has a scintillation material positioned so that ambient light entering the ambient-light receiver is incident upon the scintillation material, whereupon the scintillation material responsively emits secondary light. A light-gathering prism receives the secondary light and has a diffusing surface disposed to illuminate the reticle using the secondary light. An unpowered light source is positioned to emit light through the diffusing surface to be incident upon the reticle. The unpowered light source may be a tritium light source.

Abstract: A common-aperture optical system includes a reflective telescope having a common boresight, an entrance pupil, an exit pupil, and a beam path extending from the entrance pupil to and beyond the exit pupil. A beam splitter intersects the beam path so that the beam path is incident upon the beam splitter. A light sensor is positioned to receive an input light beam traveling along the beam path after the beam path intersects the beam splitter and passes the exit pupil of the reflective telescope. A light source produces an output light beam incident upon the beam splitter and positioned to inject the output light beam into an inverse of the beam path and toward the entrance pupil of the reflective telescope. A diverger corrects at least one of the input light beam and the output light beam.

Abstract: An optical sight includes an optical train with a reticle having a reticle substrate, and a reticle relief pattern in the reticle substrate having a relief surface oriented so that the relief surface faces an output end of the optical sight. A layer of a barrier material that is opaque to visible light is deposited upon the relief surface. There is a wavelength-converting material within the reticle relief pattern that converts a non-visible excitation wavelength to visible light. A light source of the non-visible excitation wavelength controllably illuminates the wavelength-converting material. The optical train prevents the non-visible wavelength from propagating out of the input end of the optical train.

Abstract: A phased-array light telescope includes at least two non-obscured light subtelescopes. Each of the light subtelescopes is aimed along a common boresight. The phased-array light telescope further includes a non-obscured combining imager that receives and combines the output beams of the light subtelescopes.

Abstract: A substantially neutral filter across the white-light spectrum is obtained by minimizing the wavelength-dependent effects of filtering components and of reflective coatings on surfaces. The incoming light is captured by a first prism and directed toward the interface formed by the optical contact of a second prism with a face of the first prism, where the light is partially reflected internally and partially transmitted into the second prism. The reflected light is further reflected internally and directed toward the image surface out of the first prism. The fraction of light transmitted into the second prism is reflected back and redirected out of the system toward the incoming beam. The amount of energy directed toward the image plane is controlled by the judicious selection of the refractive indices in the two materials at the contacting interface of the first and second prisms.

Abstract: A correct image reflecting telescope with zoom capability comprised of a flat mirror, a parabolic primary mirror, and an image correcting system. The flat mirror reflects the incoming light from the telescope aperture into the parabolic primary mirror. The reflected light from the primary mirror passes back through a small centrally located opening in the flat aperture mirror and into an image correcting lens system. The image correcting system repositions the focal point of the primary mirror from a point in front of the flat aperture mirror to a point behind this mirror for observation with an eyepiece. The image correcting system makes the telescope useful in terrestrial as well as celestial applications and it can be moved with respect to the primary mirror such that a zoom feature results. This intrinsic zoom of the telescope allows an observer to use a single eyepiece in place of many, eliminates the need for an additional finder scope, and also makes the telescope useful in spotting scope applications.

Abstract: An infrared telescope utilizes two mirrors in an off-axis, eccentric-pupil, re-imaging configuration. To improve the image quality of traditional two mirror telescopes, the reflective surfaces of both the primary and secondary mirrors are ellipsoidal. The ellipsoidal surface of the primary mirror has a greater eccentricity than the ellipsoidal surface of the secondary mirror. The infrared light entering through the eccentric pupil strikes the ellipsoidal reflective surface of the primary mirror. The light is reflected from the primary mirror to the ellipsoidal reflective surface of the secondary mirror. An intermediate image of the object being viewed is formed between the primary and secondary mirrors. The light is reflected from the secondary mirror to an image plane. An aperture stop is located between the secondary mirror and the image plane. The image plane is typically located within a cold shield, to reduce the likelihood that stray light will reach the image plane.