Reflectors In Series Patents (Class 359/730)
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Patent number: 6335837Abstract: An optical element has a first optical member which is a transparent body having two refracting surfaces and a reflecting, curved surface symmetric only with respect to one symmetry plane and a reference axis of which is present in the symmetry plane; and a second optical member which is a transparent body having two refracting surfaces and a reflecting surface and a reference axis of which is not present in the symmetry plane. One refracting surface of the second optical member is coupled to one refracting surface of the first optical member. The reference axis is defined by a ray passing an image center and a pupil center of an optical system including the optical element.Type: GrantFiled: July 26, 2000Date of Patent: January 1, 2002Assignee: Canon Kabushiki KaishaInventors: Michiharu Aratani, Takeshi Akiyama
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Patent number: 6278556Abstract: The invention provides a prism optical system which has an image-forming action and provides a clear yet substantially undistorted image at a wide field angle. In a prism optical system 5 comprising an aperture 1 and having an action on erecting an image formed by an objective, there are provided reflecting surfaces 31, 32, 33, 41, 42, and 43 for image inversion, each of which is constructed of a curved surface having a power, and is in an irrotationally symmetric plane shape having no rotationally symmetric axis both within and outside the surface, so that decentering aberration produced by reflection of light at the curved surfaces can be corrected.Type: GrantFiled: December 13, 1999Date of Patent: August 21, 2001Assignee: Olympus Optical Co., Ltd.Inventor: Takayoshi Togino
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Patent number: 6259564Abstract: The invention provides a real-image type finder optical system which is reduced in size in general and thickness in particular. In order from an object side of the system, the system comprises an objective optical subsystem having a positive refracting power, an image-inversion component for erecting a real image formed by the objective optical subsystem having only one image-formation action to an erect image and an ocular optical subsystem having a positive refracting power, with at least one of reflecting surfaces being defined by a roof surface. The objective optical subsystem comprises at least two reflecting surfaces of reflecting surfaces 12 to 14, each defined by a rotationally asymmetric surface with power imparted thereto.Type: GrantFiled: November 23, 1999Date of Patent: July 10, 2001Assignee: Olympus Optical Co., Ltd.Inventor: Yuji Kamo
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Patent number: 6208473Abstract: A catadioptric projection lens comprising a first lens group (G1) disposed along a first optical axis (16a), a mirror (18) which creates a second optical axis (16b), a beam splitter (20) which creates a third optical axis (16c), a second lens group (G2) including a concave mirror (L22) disposed along the third optical axis on one side of the beam splitter, and a third lens group (G3) disposed along the third optical axis on the side of the beam splitter. The first and third optical axes are parallel, a configuration which reduces aberrations arising from gravitational deformation of the lens elements, when the first and third axes are aligned with the direction of gravity.Type: GrantFiled: April 30, 1998Date of Patent: March 27, 2001Assignee: Nikon CorporationInventor: Yasuhiro Omura
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Patent number: 6178052Abstract: An object of the invention is to provide a compact yet high-performance finder optical system comprising an image inversion optical subsystem having a decentered reflecting surface, which enables a bright, distortion-free image to be observed. This object is achieved by locating a rotationally asymmetric surface in the image inversion optical subsystem forming part of the finder optical system.Type: GrantFiled: December 29, 1997Date of Patent: January 23, 2001Assignee: Olympus Optical Co., Ltd.Inventors: Norihiko Aoki, Takayoshi Togino
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Patent number: 6109756Abstract: 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.Type: GrantFiled: September 21, 1999Date of Patent: August 29, 2000Assignee: Nikon CorporationInventor: Tomowaki Takahashi
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Patent number: 6069749Abstract: A catadioptric reduction optical system capable of imaging an object by scanning in a scanning direction. The system comprises, objectwise to imagewise, a first optical system, a beam splitter, and a second optical system arranged adjacent the beam splitter opposite the image side thereof. The second optical system includes at least one concave mirror. The system also includes a third optical system arranged adjacent said beam splitter imagewise thereof, an aperture stop, and a fourth optical system having positive refractive power. The third and fourth optical systems include a plurality of lens elements preferably comprising of at least two glass types for facilitating the correction of aberrations. The system is designed such that the beam splitter is of a practical size, while allowing for a suitable working distance on the image side, a large numerical aperture, and sub-quarter micron resolution in the ultraviolet wavelength range.Type: GrantFiled: September 14, 1998Date of Patent: May 30, 2000Assignee: Nikon CorporationInventor: Yasuhiro Omura
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Patent number: 6064517Abstract: A system for multiple mode imaging is disclosed herein. The system is a catadioptric system preferably having an NA greater than 0.9, highly corrected for low and high order monochromatic aberrations. This system uses unique illumination entrances and can collect reflected, diffracted, and scattered light over a range of angles. The system includes a catadioptric group, focusing optics group, and tube lens group. The catadioptric group includes a focusing mirror and a refractive lens/mirror element. The focusing optics group is proximate to an intermediate image, and corrects for aberrations from the catadioptric group, especially high order spherical aberration and coma. The tube lens group forms the magnified image. Different tube lens groups can be used to obtain different magnifications, such as a varifocal tube lens group to continuously change magnifications from 20 to 200.times.. Multiple imaging modes are possible by varying the illumination geometry and apertures at the pupil plane.Type: GrantFiled: March 24, 1998Date of Patent: May 16, 2000Assignee: KLA-Tencor CorporationInventors: Yung-Ho Chuang, David Shafer, Bin-Ming B. Tsai, J. Joseph Armstrong
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Patent number: 6061188Abstract: In a projection printing apparatus, illumination light from a lamp housing illuminates a photomask, and a diffracted light beam from the photomask is focused on an exposed substrate via a projection optical system to project a circuit pattern, the projection optical system including first and second halfmirrors and first and second concave mirrors. The first and second halfmirrors are arranged in symmetry or similar symmetry with respect to a normal to an optical axis of a diffracted light beam directed from the first halfmirror to the second halfmirror. Thus, a projection printing apparatus and a projection printing method are obtained in which unevenness in transmissivity in the projection optical system can be compensated for and steric hindrance or degradation of image characteristics is not caused.Type: GrantFiled: December 1, 1997Date of Patent: May 9, 2000Assignee: Mitsubishi Denki Kabushiki KaishaInventor: Kazuya Kamon
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Patent number: 6033079Abstract: An all-refelctive optical system for a projection photolithography camera has a source of EUV radiation, a wafer and a mask to be imaged on the wafer. The optical system includes a first concave mirror, a second mirror, a third convex mirror, a fourth concave mirror, a fifth convex mirror and a sixth concave mirror. The system is configured such that five of the six mirrors receives a chief ray at an incidence angle less than substantially 12.degree., and each of the six mirrors receives a chief ray at an incidence angle of less than substantially 15.degree.. Four of the six reflecting surfaces have an aspheric departure of less than substantially 7 .mu.m. Five of the six reflecting surfaces have an aspheric departure of less than substantially 14 .mu.m. Each of the six refelecting surfaces has an aspheric departure of less than 16.0 .mu.m.Type: GrantFiled: March 15, 1999Date of Patent: March 7, 2000Inventor: Russell Hudyma
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Patent number: 5959784Abstract: The invention pertains to optical projection-exposure apparatus for photolithography that can focus a pattern defined by a mask onto a non-flat substrate. In one embodiment, piezoelectric elements are used as an actuator for adjusting the optical path length between the mask and the substrate. A first reflector reflects a light flux transmitted by the mask. A telecentric optical system then forms an image of the mask in a focal plane. A second reflector reflects the light flux from the telecentric perpendicularly onto the substrate. The actuator moves the first or second reflectors, changing the optical path length of the light flux. A focus sensor detects the height of the sensitized surface of the substrate in a direction perpendicular to the sensitized surface of the substrate and thereby provides a focus signal to the actuator. The actuator then moves the focal plane to the sensitized surface.Type: GrantFiled: April 24, 1997Date of Patent: September 28, 1999Assignee: Nikon CorporationInventors: Masami Seki, Hiroshi Chiba
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Patent number: 5907442Abstract: A reflective optical system includes, in traveling order of light, a correction plate having an aspherical surface and a reflecting mirror for concentrating the light. An image is formed out of an optical path between the correction plate and the reflecting mirror.Type: GrantFiled: January 17, 1997Date of Patent: May 25, 1999Assignee: Canon Kabushiki KaishaInventor: Toru Matsuda
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Patent number: 5835284Abstract: A catadioptric optical system in which a first imaging optical system is constructed of a unidirectional optical apparatus which transmits outgoing light from a first plane in one direction only and a bidirectional optical apparatus for transmitting the light that enters and reflecting the same to form an interim image of the first plane. A light guide guides the light from the interim image to a second imaging optical system through which the interim image is reimaged on a second plane. The unidirectional optical apparatus has an optical axis and at least one lens movable along the optical axis.Type: GrantFiled: June 26, 1997Date of Patent: November 10, 1998Assignee: Nikon CorporationInventors: Tetsuo Takahashi, Yasuhiro Omura
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Patent number: 5835278Abstract: Optical beam-splitting system for partitioning the real image of an object into a plurality of partial images onto image receivers arranged with a distance between them, comprising an objective lens and a plurality of optical elements arranged in the ray path behind the objective lens with each optical element comprising at least one reflecting plane deflecting the path of rays, the optical elements respectively intercepting partial luminous fluxes not interfering with each other, the optical elements being positioned outside of the overlapping region of the rays emanating from the extremities of the object and passing through the objective lens and in front of the image plane of the objective lens.Type: GrantFiled: May 10, 1993Date of Patent: November 10, 1998Inventors: Leoind Borisovich Rubin, Viktor Vladimirovich Lazarev, Alexandr Tursunovich Rakhimov
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Patent number: 5815310Abstract: 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.Type: GrantFiled: December 12, 1995Date of Patent: September 29, 1998Assignee: SVG Lithography Systems, Inc.Inventor: David M. Williamson
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Patent number: 5805356Abstract: A projection exposure apparatus achieves good imaging performance as securing a sufficient working distance. This projection exposure apparatus has a projection optical system for projection-transferring a real-size image of a first object onto a second object, which is disposed between the first object and the second object. This projection optical system has a cemented lens consisting of a plano-convex lens and a first negative meniscus lens, a second negative meniscus lens, and path-bending prisms for guiding light from the first object to the plano-convex lens and for guiding light from the concave mirror to the second object. The present invention is based on finding of appropriate ranges of refractive powers of the first and second negative meniscus lenses and appropriate ranges of Abbe numbers of glass materials for the first and second negative meniscus lenses.Type: GrantFiled: January 31, 1996Date of Patent: September 8, 1998Assignee: Nikon CorporationInventor: Hiroshi Chiba
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Patent number: 5771125Abstract: Catadioptric systems are disclosed for projecting images of an object such as a mask onto a substrate. The catadioptric systems have high numerical apertures and large working distances. The catadioptric systems are useful with short-wavelength illumination and permit the object and substrate to be in parallel planes. Conditional expressions are provided for the catadioptric systems.Type: GrantFiled: June 13, 1997Date of Patent: June 23, 1998Assignee: Nikon CorporationInventor: Toshiro Ishiyama
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Patent number: 5768453Abstract: Methods and apparatus are disclosed for concentrating the energy of a laser diode beam by imaging a first numerical aperture of the beam in one beam plane to a reduced numerical aperture at a focal plane, and by guiding the beam between reflective boundaries to maintain the value of a lesser second numerical aperture in another beam plane at the focal plane. The reduced numerical aperture in the first plane optimally matches the second numerical aperture in the second plane so that the energy can be received into the entrance end of an optical fiber whose numerical aperture also matches the second numerical aperture. The area of this fiber preferably matches that of the image at the focal plane. A coupler that guides the beam to its focal plane preferably utilizes an imaging element, e.g., a cylindrical lens or a cylindrical elliptical mirror, and a pair of spaced reflective walls.Type: GrantFiled: December 13, 1994Date of Patent: June 16, 1998Assignee: Raytheon CompanyInventor: Leland V. Gardner
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Patent number: 5748377Abstract: A headup display including a light emission-type display source, a concave mirror having an spherical reflecting surface and located so as to reflect light emitted from the display source, and a reflection-type hologram located so as to reflect the light reflected on the concave mirror toward an observer in a mobile unit. The concave mirror is configured so that its lateral focal length contributing to lateral enlargement of a displayed image is shorter than its longitudinal focal length contributing to longitudinal enlargement of the displayed image. The reflection-type hologram is configured so that its longitudinal focal length contributing to longitudinal enlargement of the displayed image is shorter than its lateral focal length contributing to lateral enlargement of the displayed image.Type: GrantFiled: June 20, 1996Date of Patent: May 5, 1998Assignee: Fujitsu LimitedInventors: Tsuyoshi Matsumoto, Yoshihiro Mizuno, Keiichi Omata, Shin Eguchi
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Patent number: 5739956Abstract: There is provided an objective lens for focusing a subject light to form a real image on a predetermined focal plane, an eyepiece through which the real image is observed, and the first and second prism assemblies between the objective lens and the eyepiece for erecting an inverted image. The first and second prism assemblies are arranged at a predetermined distance away from each other such that the exit surface of the first prism assembly and the incident surface of the second prism assembly face each other across the focal plane. As a result, the dust on the whole surface of the prism assemblies and the like are made inconspicuous. Moreover, a visual field frame is provided on the focal plane, so that the visual field frame can be prevented from becoming out of focus and the border of the visual field can be seen clearly. Furthermore, a virtual image of a mark such as a target mark is formed in the Albada method.Type: GrantFiled: October 16, 1996Date of Patent: April 14, 1998Assignee: Fuji Photo Optical Co., Ltd.Inventor: Katsuhiro Ohtake
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Patent number: 5691802Abstract: It is an object of the invention to provide a catadioptric optical system with an arrangement for realizing a large numerical aperture and reducing the diameter of a concave mirror while ensuring a sufficient working distance on the image side, and also an exposure apparatus using this catadioptric optical system.A catadioptric optical system according to the invention includes a first imaging optical system for forming an intermediate image of a pattern on a first plane, a second imaging optical system for forming a reduced image of the intermediate image on a second plane, and an optical path deflecting member for guiding a light beam from the first imaging optical system to the second imaging optical system. The first imaging optical system has at least a first optical element group having a positive refracting power, and a second optical element group having a concave mirror and a meniscus lens component with a concave surface facing the first imaging optical system.Type: GrantFiled: November 3, 1995Date of Patent: November 25, 1997Assignee: Nikon CorporationInventor: Tomowaki Takahashi
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Patent number: 5680258Abstract: An optical guide for horizontally aligning two vertically stacked images generated by one or two SLMs. The optical guide has a beam splitter that directs both images along two different paths. A first and a second aligning reflectors each disposed along each path for aligning the images. The beam splitter then redirects the images to the image plane 15. Along both paths, at least the aligning reflectors are optically powered so as to change the width or height of the images.Type: GrantFiled: July 3, 1996Date of Patent: October 21, 1997Assignee: Texas Instruments IncorporatedInventor: Charles H. Anderson
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Patent number: 5677788Abstract: 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.Type: GrantFiled: March 28, 1996Date of Patent: October 14, 1997Assignee: Hughes ElectronicsInventors: Chungte W. Chen, James D. Zimmerman, David A. Ansley
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Patent number: 5644436Abstract: A concentric optical system usable as either an imaging optical system or an ocular optical system, which enables a clear image to be obtained at a field angle of up to about 90.degree. and with a pupil diameter of up to about 10 millimeters with substantially no chromatic aberration. The concentric optical system includes a first optical component having a first semitransparent reflecting surface (2), and a second optical component having a second semitransparent reflecting surface (3). The first and second semitransparent reflecting surfaces (2 and 3) have respective centers of curvature disposed at approximately the same position (1). The first and second optical components are different in dispersion from each other.Type: GrantFiled: March 17, 1995Date of Patent: July 1, 1997Assignee: Olympus Optical Co., Ltd.Inventors: Takayoshi Togino, Kunie Nakagiri
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Patent number: 5627689Abstract: An optical element that produces line bow, for example, a toric or cylindrical mirror or lens, is provided in a light-supplying optical device in addition to a first line-bow-producing optical element already present in the device so that a substantially straight line of light is formed on an original document. The light-supplying optical device also includes a light source that generates illuminating light to illuminate the original document and the first optical element that has a toric surface for collecting the illuminating light onto the original document and that is positioned so that the illuminating light shines at a certain angle relative to its toric surface. With this device, the second optical element having a toric surface is positioned in the optical path of the light source and of the original document so as to offset the curve of the illuminating light that otherwise would be generated on the original document by the first optical element.Type: GrantFiled: April 7, 1995Date of Patent: May 6, 1997Assignee: Nikon CorporationInventors: Nobuhiro Fujinawa, Masayuki Inami, Toshiya Aikawa
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Patent number: 5581413Abstract: An optical guide for horizontally aligning two vertically stacked images generated by one or two SLMs. The optical guide has a channel separator that directs both images along two different paths. A pair of aligning reflectors on each path vertically shift the images with respect to each other so that at least part of the images on the first path are aligned side-by-side with at least part of the images on the second path. The channel separator then redirects the images to the image plane. Along both paths, at least two of the reflecting surfaces of channel separator or aligning reflectors are optically powered so as to change the width or height of the images.Type: GrantFiled: November 30, 1994Date of Patent: December 3, 1996Assignee: Texas Instruments IncorporatedInventor: Charles H. Anderson
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Patent number: 5386316Abstract: An all-reflective optical system has a first (10) and second (12) reflecting assembly. The first reflecting assembly (10) includes an afocal three-mirror anastigmat (18, 20, 22) with one or more apertures (28 A-D) in the tertiary mirror (22) to enable light or energy to pass therethrough. Light or energy reflects from the second reflecting assembly (12) through the apertures (28 A-D) to provide simultaneous viewing of a scene by a plurality of instruments (34). The second reflecting assembly (12) includes a planar mirror which provides pointing and stabilization motions for all of the instruments simultaneously without degrading image quality or pupil registration.Type: GrantFiled: February 8, 1993Date of Patent: January 31, 1995Assignee: Hughes Aircraft CompanyInventor: Lacy G. Cook
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Patent number: 5313326Abstract: A projection unit for a car head-up display comprises a display source, a curved mirror which provides the optical power of the projection unit and, in use, receives light from the display source, and a Fresnel mirror extending generally between the display source and the curved mirror and disposed to receive reflected light from the curved mirror and to reflect that light in a desired direction. The curved mirror and the Fresnel mirror may be disposed on a solid block of transparent material having one curved end coated to provide the curved mirror, the display source being located at an opposite end of the block, and the Fresnel mirror being formed in a block face extending from the opposite end of the block to the curved end of the block.Type: GrantFiled: September 30, 1992Date of Patent: May 17, 1994Assignee: Pilkington plcInventor: Andrew P. Ramsbottom
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Patent number: 5303084Abstract: A new and improved laser light beam homogenizer for transforming a laser beam with spatially inhomogeneous intensity into a beam with a more nearly spatially uniform intensity pattern is presented. The light beam is diverged by a lens and presented to an integrator. The integrator transforms the beam into a beam with a more uniform illumination. The uniform illumination beam is then impinged on control optics to limit the divergence of the uniform beam and control higher order distortion in the system. This beam may then be illuminated at a predetermined distance by a projecting optic lens. The laser light beam homogenizer of this invention is particularly well suited for use in an imaging lidar system.Type: GrantFiled: August 27, 1991Date of Patent: April 12, 1994Assignee: Kaman Aerospace CorporationInventors: Kent P. Pflibsen, Albert N. Stuppi
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Patent number: 5278695Abstract: An apparatus is provided for magnifying the image of distant objects which has the unique feature that, unlike the Galilean telescope, the magnification is largely determined by how far the eye is located from the apparatus. Furthermore, unlike the Loupe, objects to be viewed can be at any arbitrarily large distance from the apparatus. In addition, the apparatus does not require positioning of the eye at the exit pupil of the instrument; it does not require centering of the eye on the optic axis of the instrument; and it does not require refocusing for different object distances. Still, it provides erect, non-inverted images to the viewer. The includes a positive optical element defining an optic axis for the apparatus and having a positive focal length for converging an incoming bundle of rays of electromagnetic radiation.Type: GrantFiled: October 4, 1991Date of Patent: January 11, 1994Assignee: Blue Sky Research, Inc.Inventors: Rolin J. Gebelein, Ronald E. Grubman
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Patent number: 5274498Abstract: An optical system for a night vision video camera having a pair of mirrors with an optical prescription providing f/2.8 speed and 50 line pairs per line millimeter resolution to an image intensifier located between the two mirrors on the common optic axis of the mirrors. The mirror first receiving the image to be viewed is an f/4 parabolic mirror and the second mirror is an f/10 spherical mirror with an external diameter of about forty percent of the diameter of the parabolic mirror (i.e., the obsuration ratio is about 0.40). The second mirror receives the reflected image of the object viewed by the night vision video camera from the first mirror and reflects the image to the image intensifier. The image may be viewed at a external view finder and can also be recorded.Type: GrantFiled: April 14, 1992Date of Patent: December 28, 1993Assignee: Pactylamatic, Inc.Inventors: Arturo R. Rios-Rivera, Michael Palermiti
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Patent number: 5245175Abstract: A focus detecting optical system comprises two imaging optical systems which are composed of an integrally molded prism, and is adapted to perform focus detection on the basis of relative positional relationship between an image of an object formed with one of the imaging optical systems and another image of the object formed with the other imaging optical system. Ineffective optical path regions of the surfaces of the prism which allow transmission or reflection of the rays entering the prism are designed as light diffusing surfaces and/or surfaces coated with a light absorption substance. An aperture stop arranged before each surface of incidence of light is arranged eccentrically with regard to the optical axis of incident rays or each surface of incidence of light has a refractive power asymmetrical with regard to said optical axis so that all the rays incident on the totally reflecting surfaces arranged in the two imaging optical systems are totally reflected.Type: GrantFiled: March 26, 1992Date of Patent: September 14, 1993Assignee: Olympus Optical Co., Ltd.Inventor: Tatsuo Inabata
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Patent number: 5238210Abstract: A system for collecting solar energy includes a space station which receives and concentrates solar light and produces a plurality of collimated beams each diverging toward a common axis and toward a target area on the surface of the earth. On reaching the target area on the earth, each of the collimated beams is superimposed on the other.Type: GrantFiled: May 8, 1992Date of Patent: August 24, 1993Inventor: Albert K. Heitzmann
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Patent number: 5159495Abstract: The present invention relates to an optical element and catadioptric optical systems using the optical element. The optical element has a spherical surface with a reflective layer formed on at least a portion of the surface, and is formed of a radiant energy transmitting material having a radial gradient index of refraction. The catadioptric optical systems include at least two optical elements at least one of which is refractive, and at least one of which has a gradient index therein. One optical system includes first and second optical elements disposed sequentially along a longitudinal axis of the system. The second optical element is the optical element with the gradient index. The first optical element is formed of a homogeneous light transmitting material and includes a spherical surface, and a reflective layer formed on a central portion of one of the spherical surface.Type: GrantFiled: December 11, 1990Date of Patent: October 27, 1992Assignee: Eastman Kodak CompanyInventor: David P. Hamblen
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Patent number: 5136427Abstract: An optical system for use in conjunction with a camera viewfinder having a penta-mirror comprises a positive first lens element and a negative second lens element satisfying predetermined conditions.Type: GrantFiled: July 9, 1990Date of Patent: August 4, 1992Assignee: Asahi Kogaku K.K.Inventor: Saburo Sugawara