Abstract: An optical system for viewing an object has a plurality of lenses and a main optical axis coincident with the centers of the lenses. The optical system further comprises a low magnification optical subsystem that is operative to view the object at a first magnification and a high magnification optical subsystem that is operative to view the object at a second magnification that is higher than the first magnification. The high magnification optical subsystem has a high magnification optical axis along which light rays that are received from the main optical axis are transmitted. A movable element is locatable on the high magnification optical axis and is movable in directions transverse to the axis for receiving and transmitting light rays.

Abstract: An endoscope objective lens is provided and has a front-group divergent lens system, an aperture stop, and a rear-group convergent lens system in this order from the object side. The back focal length Bf of the whole system is longer than 2.5 times the combined focal length f of the whole system. The rear-group convergent lens system includes a cemented lens. The endoscope objective lens satisfies the specific formula.

Abstract: A light receiving optical system includes: a relay optical system for converging light to be measured which has been converged on an image plane of an objective optical system on a view angle defining aperture for incidence through the view angle defining aperture. The light receiving optical system has the relay optical system with a relay lens operable to be selectively switched between a first and a second conjugated positions, and a first and a second light flux limiting aperture members disposed in proximity to the relay lens in the case where the relay lens is selectively switched between the first and the second conjugated positions.

Abstract: A method of displaying, selecting and magnifying multiple micro-images, and a display device and portable terminal using the method. A display device for displaying, selecting and magnifying multiple micro-images, includes: a concave reflector having a radius of curvature and a focal distance; multiple display panels, arranged within the focal distance, displaying the multiple micro-images toward the concave reflector; and a corner-image interrupter, interposed between the multiple display panels and the concave reflector, interrupting a distorted portion of a magnified image generated when one of the micro-images displayed on a display panel is reflected by corners of the concave reflector.

Abstract: A catadioptric projection objective for imaging a pattern provided in an object plane of the projection objective onto an image plane of the projection objective comprises: a first objective part for imaging the pattern provided in the object plane into a first intermediate image; a second objective part for imaging the first intermediate imaging into a second intermediate image; a third objective part for imaging the second intermediate imaging directly onto the image plane; wherein a first concave mirror having a first continuous mirror surface and at least one second concave mirror having a second continuous mirror surface are arranged upstream of the second intermediate image; pupil surfaces are formed between the object plane and the first intermediate image, between the first and the second intermediate image and between the second intermediate image and the image plane; and all concave mirrors are arranged optically remote from a pupil surface.

Abstract: An endoscope has an endoscope tube and a lens system arranged in the endoscope tube. The lens system has endoscope lens components and air gaps between the lens components. An illumination system is arranged within the endoscope tube. The endoscope lens components each have an axial lens length; the endoscope lens components include first lens components and second lens components, wherein the axial lens length of the first lens components is the shortest axial lens length, respectively, and wherein the axial lens length of the second lens components is longer than the shortest axial lens length. The first lens components with the shortest axial lens length are arranged in an area of an axial center of the endoscope tube. The second lens components having the longer axial lens length have a first half and a second half and an air gap arranged between the first and second halves.

Abstract: An illumination optical apparatus guides to an illumination object a light beam emitted from a light source. The illumination optical apparatus includes an enlarging optical system, disposed between the light source and the illumination object, and a reduction optical system, disposed between the enlarging optical system and the illumination object. The enlarging optical system is formed so that an image plane is disposed between the light source and the illumination object.

Abstract: An illumination optical apparatus and a projection type display apparatus capable of enhancing an illumination efficiency; having an ellipsoidal mirror, a light source arranged at a first focal point of the ellipsoidal mirror, a stop arranged closer to said light source side by a predetermined distance from a second focal point of said ellipsoidal mirror, and a positive refractive collimator lens for collimating a light flux emitted from the stop to a parallel light flux. A condition (0.01<L2/L1<0.06) is satisfied where, L1 is a distance from an apex of the ellipsoidal mirror to the second focal point thereof and, L2 (the light source side is a positive distance) is a distance from the second focal point of the ellipsoidal mirror to the stop.

Abstract: The field of the invention is that of optical devices allowing the superposition of an electronic image on an image coming from an external scenery. The subject of the invention is an optical device for superposing images, designed to be positioned in front of an optical module comprising at least an objective and a photosensitive surface positioned in the focal plane of said objective. The device comprises an image source, an optical relay and an optical combiner formed of two optical parts assembled via an approximately plane common face including a weakly reflective coating. The combiner has the general form of a plate with plane parallel faces, the common face being inclined at around 45 degrees to said plane faces. It has an entrance face and a opposing face that are approximately perpendicular to the plane faces, the opposing face having approximately the form of a reflecting spherical surface.

Abstract: The wide angle lens system described herein allows projection devices (e.g., rear projection display devices) to be more compact than would otherwise be possible. The lens system includes a wide angle lens stage and a relay lens stage. When operating as a projection device, the relay lens stage projects a distorted intermediate image to the wide angle lens stage, which projects the image for display. The distortion cause by the relay lens stage compensates (i.e., is approximately equal and opposite) for the distortion caused by the wide angle stage. The distortion can be the image shape and/or the focal plane. When operating as a taking device, the wide angle stage provides a distorted image to the relay lens stage, which compensates for the distortion and provide a less distorted, or even non-distorted image, for capture.

Abstract: An image forming system and lens system including at least one molded chalcogenide lens element and configured to simultaneously image light at the medium wave infrared region (MWIR) and the long wave infrared region (LWIR) at a common focal plane.

Abstract: The present invention relates to a system of applying optical gradient forces to form a plurality of optical traps to manipulate small particles. The system includes a light source for generating a focused beam of light which is directed along an optical axis though a phase patterning optical element having a variable optical surface and which has a virtual lens encoded thereon. The optical element produces a plurality of beamlets that are coverged at a position between the optical element and a single transfer lens, and directed through the transfer lens to overlap at the back aperture of a focusing lens. The focusing lens coverges the beamlets to form a plurality of optical traps in the working focal region where particles to be examined, manipulated, or measured, are disposed.

Abstract: The present invention provides a laser irradiation apparatus and a laser irradiation method which can reduce displacement of entrance point of laser light into a diffractive optical element, when laser light enters the diffractive optical element through a beam expander optical system. When the scale of laser light emitted from a laser oscillator is enlarged through a beam expander optical system including two lenses, and the laser light enters the diffractive optical element, the emission point of the laser light and the first and second lenses are arranged such that the positions of the emission point of the laser light and the second lens are conjugate to each other by the first lens.

Abstract: A relay lens is provided in an illumination system for use in microlithography. The relay lens can be used to uniformly illuminate a field at a reticle by telecentric light beams with variable aperture size. The relay lens can include first, second, and third lens groups. At least one of the second and third lens groups can include a single lens. This can reduce costs and increase transmission by requiring less CaF2 because fewer optical elements are used compared to prior systems.

Abstract: An illumination system includes a light source, first and second cylindrical lens arrays, and a relay lens. The first cylindrical lens array includes a plurality of cylindrical lens cells which divide light emitted from the light source into a plurality of beams. The second cylindrical lens array includes a plurality of cylindrical lens cells which combine the beams divided by the cylindrical lens cells in an identical direction. The relay lens relays beams passed through the second cylindrical lens array so that most of the beams are concentrated on an incident light axis to have a Gaussian distribution. Accordingly, light passed through slits for controlling the divergence angle of incident light or the etendue of an optical system has a Gaussian distribution in a color separation direction or a color scrolling direction.

Abstract: Optical systems for endoscopes, borescopes, dental scopes, and the like which are characterized by having three groups of lenses of positive optical power and an external entrance pupil. Typically, all three groups of lenses are displaced from the pupil and focal planes. As a consequence, the displaced groups take part in the image transfer as well as in the pupil transfer. The optical power requirements can thus be shifted from one group to another, distributing as well as reducing the overall power requirement. Moreover, the aberration correction can also be shared between these groups. The first group, which conventionally has the highest optical power, and consequently a large amount of aberrations to be corrected, can in this way transfer some of the optical aberration correction to the other groups. The sharing of the optical functions and aberration correction results in a fully integrated optical system.

Abstract: An apparatus and method for manipulating small dielectric particles. The apparatus and method involves use of a diffractive optical element which receives a laser beam and forms a plurality of light beams. These light beams are operated on by a telescope lens system and then an objective lens element to create an array of optical traps for manipulating small dielectric particles.

Abstract: A zoom lens system is disclosed. The zoom lens system forms a final image of an object and a first intermediate real image between the object and the final image. The zoom lens system includes a first optical unit located between the object and the first intermediate real image. The first optical unit comprises at least one optical subunit which is moved to change the size (magnification) of the first intermediate real image. The zoom lens system also includes a second optical unit located between the first intermediate real image and the final image, at least a portion of which is moved to change the size (magnification) of the final image. The zoom lens system provides a wide zoom range of focal lengths with continuous zooming between the focal lengths.

Abstract: A projection type display apparatus, wherein a common case can be used for housing an illumination optical system even when a shape of an image display element and an optical path length in a prism are different, is provided: wherein a light source for emitting an illumination light, an image display device, an illumination optical system for irradiating the illumination light from the light source to the image display device, and a projection optical system for projecting an image formed by said image display device are provided; the illumination optical system comprises a first fly-eye lens and a second fly-eye lens arranged at each other's focal points, a first lens group and a second lens group arranged over a mirror for bending an optical path; the first and second lens groups have a same focal length but a different back focus; and predetermined condition formulas are satisfied.

Abstract: Disclosed is an illumination optical system having an imaging optical system for imaging a predetermined object plane upon an image plane, by use of light supplied from an integrator that functions to produce a plurality of light sources using light from a light source. In one preferred form of the invention, the imaging optical system includes, in an order from a light incidence side thereof, a first lens group having a positive power, a second lens group having a negative power, and a third lens group having a positive power, wherein the second lens group includes a concave lens at a light exit side thereof and wherein the third lens group includes a convex lens at a light entrance side thereof. The position of intersection between an optical axis of the imaging optical system and a principal ray of abaxial light is defined between the second lens group and the third lens group.

Abstract: An optical device for viewing an object at a range of working distances. The device comprises a slender tube of a certain length and having a distal end and a proximal end. The device further comprises an imaging system disposed at the distal end and having a wide viewing angle. The device also comprises a telescopic system associated with the proximal end and having a narrow viewing angle. The imaging system is designed to form an image of the object at an image plane located on the device's optical axis and within the tube closer to the distal end than to the proximal end. The telescopic system is designed to enable viewing of the image of the object. The device is especially adapted to function as an endoscope in medical applications and may be disposable.

Abstract: A projection optical unit has two lens groups. A first projection optical unit disposed closest to an image display element, temporarily forms a first enlarged image (magnification: M1) at the image display element side, rather than at a second projection optical unit. The first enlarged image is subsequently projected in an enlarged form (magnification: M2, wherein M2>M1) onto a screen via the second projection optical unit. A field lens group having positive refractive power is disposed between the first projection optical unit and the second projection optical unit. Consequently, the relationship between F2, which is the F-value of the second projection optical unit, and F1, which is the F-value of the first projection optical unit, becomes F2=F1/M1, whereby it is possible to realize very-wide-angle imaging at a field angle exceeding 90 degrees.

Abstract: A multi-aperture high-fill-factor telescope is provided. Specifically a multi-aperture high-fill-factor telescope is provided that includes a plurality of sub-aperture telescopes, each sub-aperture telescope being configured to collect electromagnetic radiation from a scene and including first, second, third, and fourth powered mirrors; a set of combiner optics configured to combine electromagnetic radiation collected by the sub-aperture telescopes to form an image of the scene; and a plurality of sets of relay optics, the sets of relay optics are respectively associated with the sub-aperture telescopes and each set of relay optics includes a first flat fold mirror, a trombone mirror pair, and a last flat fold mirror, wherein the last flat fold mirrors are disposed within about a beam diameter of respective exit pupils of the sub-aperture telescopes.

Abstract: An assembly is described for connection to a borescope to simultaneously provide a virtual image for direct viewing by an observer and a video image for viewing on a display. The assembly (10) comprises a body (12) with a distal end for connection to an insertion tube of a borescope and a proximal end providing an eye piece into which an observer may look. The body contains a relay lens (16) and an ocular lens (18). A beam splitter (28) is mounted in the optical path between the relay lens (16) and the ocular lens (18) and diverts a proportion of light received from the relay lens (16) to an image-to-video conversion device (30) mounted laterally to the optical path. The ocular lens (18), beam splitting device (28) and the image-to-video conversion device (30) are all located in a common mounting (38) which can be translated in a direction parallel to the optical path to allow for focussing.

Abstract: An infrared zoom lens having no aspheric lens elements comprises, six distinct lens groups each having two or less spherical lens elements. The first group has a positive power, the second group has a negative power, the third group has a positive power, the fourth group has a negative power, the fifth has a positive power and the sixth group has either a positive or negative power with the purpose of relaying and focusing the output of the fourth lens group onto the focal plane of the imaging device. The second and fourth groups are axially movable but fixed relative to each other and move as a group relative to stationary groups one and three. The zoom ratio is thus varied, and no additional motion is required to keep the imagery sharp at the output focal plane as the lens is varied from the wide angle to the telephoto position.

Abstract: A stereoscopic microscope is disclosed that includes an objective lens which substantially collimates light from an object of interest, left and right afocal zooming systems, left and right afocal relay systems, and an ocular tube optical system which forms magnified images of the object. The optical axis of the objective lens is substantially normal to a plane that includes the optical axes of the left and right afocal zooming systems, a beam splitter is arranged in each optical path between the left and right afocal zooming systems and said ocular tube optical system, and in each optical path between the left and right afocal zooming systems and the ocular tube optical system, there is at least one region between the beam splitter and the ocular tube optical system where the optical axes of light fluxes from an observation object point intersect. Preferably, there are additional regions of intersecting light.

Abstract: An optical device for viewing an object at a range of working distances. The device comprises a slender tube of a certain length and having a distal end and a proximal end. The device farther comprises an imaging system disposed at the distal end and having a wide viewing angle. The device also comprises a telescopic system associated with the proximal end and having a narrow viewing angle. The imaging system is designed to form an image of the object at an image plane located on the device's optical axis and within the tube closer to the distal end than to the proximal end. The telescopic system is designed to enable viewing of the image of the object. The device is especially adapted to function as an endoscope in medical applications and may be disposable.

Abstract: A space-based multi-aperture telescope is capable of achieving high fill factors, on the order of at least 50% and more preferably at least 80%. High fill factors can be achieved according to the present invention by providing a combiner section that combines the light collected by plural sub-aperture telescopes at the exit pupil of the telescope.

Abstract: The wide angle lens system described herein allows projection devices (e.g., rear projection display devices) to be more compact than would otherwise be possible. The lens system includes a wide angle lens stage and a relay lens stage. When operating as a projection device, the relay lens stage projects a distorted intermediate image to the wide angle lens stage, which projects the image for display. The distortion cause by the relay lens stage compensates (i.e., is approximately equal and opposite) for the distortion caused by the wide angle stage. The distortion can be the image shape and/or the focal plane. When operating as a taking device, the wide angle stage provides a distorted image to the relay lens stage, which compensates for the distortion and provide a less distorted, or even non-distorted image, for capture.

Abstract: The invention relates to an image transmission system for endoscopes and similar viewing tubes with at least one rod lens and at least one additional lens system. In order to produce an image transmission system of simple and economical construction, it is proposed in accordance with the invention that the minimum of one rod lens should be constructed as a plano-convex lens whose length corresponds to the curvature radius of its convex terminal surface. In addition, the invention relates to a process for producing a rod lens for an image transmission system as well as an endoscope equipped with such an image transmission system.

Abstract: A multiple aperture imaging system, that includes: a plurality of imaging elements for capturing light; an optical relay assembly for phasing the captured light; a means for diverting the captured light within the multiple aperture imaging system to produce a plurality of images; and an imaging sensor capable of receiving the captured light from each of the plurality of imaging elements.

Abstract: Optical systems (1-19) for endoscopes and the like are characterized by an integrated design in which the locations of the components and the aberration corrections are no longer tied to the optical functions of the objective (1-6) and the relays (7-19), and in which the relays may depart from symmetry. The power requirements can thus be shifted from one group to another, thereby reducing the overall power requirement. Moreover, the aberration correction can be shared between the optical group of the integrated system.

Abstract: The relay optical system comprises, in order from the intermediate image position I toward the the exit pupil EXP side, a first unit G1 having a negative refracting power and a second unit G2 having a positive refracting power, wherein the distance from the rearmost surface of the second unit to the exit pupil position is at least 30 mm. The relay optical system allows a photographing apparatus to be mounted on a microscope without the microscope and the photographing apparatus excluding each other from their predetermined positions.

Abstract: Improved optical devices and methods transmit optical images along elongate optical paths with relatively limited cross-sectional dimensions using an improved objective, relay, and ocular systems. In a first aspect, at least one intermediate image formed within an optical component, rather than being formed in a gap between optical components. In a preferred embodiment, a first intermediate image is formed within glass of the most proximal objective lens, with the first intermediate image extending axially along a curved image location within the glass. The last intermediate image may similarly be disposed within a distal lens of the ocular system. By making use of a first and/or last intermediate image disposed in this manner within a lens, endoscopes can exhibit a significantly larger Numerical Aperture than known endoscopes having similar cross-sectional dimensions.

Abstract: An aberration-correcting optical relay for an optical system. The relay comprises front and rear converging optical units together with a correcting meniscus or two correcting meniscuses placed symmetrically relative to each other, the meniscus(es) having main faces that are substantially concentric, and preferably exactly concentric, the two converging optical units being placed on a common axis and the correcting meniscus(es) being placed on said axis between the two converging optical units. The front converging optical unit situated upstream from the correcting meniscus(es) is placed in such a manner that the distance from an image point of the portion of the optical system upstream from the optical relay to the front converging optical unit is equal to the focal length of the front converging optical unit, said unit thus transforming a beam coming from said image point into a parallel beam.

Abstract: A zoom eyepiece optical system, which is used with an objective optical system, includes a first lens group which is stationary with respect to the objective optical system, a negative second lens group which is movable upon zooming, a positive third lens group which is movable upon zooming, and a stationary positive fourth lens group, in this order from the objective optical system. Upon zooming from the long focal length extremity to the short focal length extremity of the zoom eyepiece optical system, the negative second lens group and the positive third lens group move away from each other, and an intermediate image is formed between the negative second lens group and the positive third lens group.

Abstract: The wide angle lens system described herein allows projection devices (e.g., rear projection display devices) to be more compact than would otherwise be possible. The lens system includes a wide angle lens stage and a relay lens stage. When operating as a projection device, the relay lens stage projects a distorted intermediate image to the wide angle lens stage, which projects the image for display. The distortion cause by the relay lens stage compensates (i.e., is approximately equal and opposite) for the distortion caused by the wide angle stage. The distortion can be the image shape and/or the focal plane. When operating as a taking device, the wide angle stage provides a distorted image to the relay lens stage, which compensates for the distortion and provide a less distorted, or even non-distorted image, for capture.

Abstract: A remote imaging apparatus such as a borescope or endoscope. The apparatus has an image relay means (4) for relaying an image along the main axis (3) from the distal end of the scope and an annular light pipe (1) for transmitting light to the distal end of the scope to illuminate the object to be viewed. At least the inner or outer surface of annular light pipe (1) is surrounded by air.

Abstract: An apparatus and method for manipulating small dielectric particles. The apparatus and method involves use of a diffractive optical element which receives a laser beam and forms a plurality of light beams. These light beams are operated on by a telescope lens system and then an objective lens element to create an array of optical traps for manipulating small dielectric particles.

Abstract: The relay optical system comprises, in order from the intermediate image position I toward the the exit pupil EXP side, a first unit G1 having a negative refracting power and a second unit G2 having a positive refracting power, wherein the distance from the rearmost surface of the second unit to the exit pupil position is at least 30 mm. The relay optical system allows a photographing apparatus to be mounted on a microscope without the microscope and the photographing apparatus excluding each other from their predetermined positions.

Abstract: A system for multiple mode imaging is disclosed. The catadioptric system has an NA greater than 0.65, and preferably greater than 0.9, highly corrected for low and high order monochromatic aberrations. The system employs unique illumination entrances and optics to collect reflected, diffracted, and scattered light over a range of angles. Multiple imaging modes are possible by varying the illumination geometry and apertures at the pupil plane. Illumination can enter the catadioptric optical system using an auxiliary beamsplitter or mirror, or through the catadioptric elements at any angle from 0 to 85 degrees from vertical. The system may employ a relayed pupil plane, used to select different imaging modes, provide simultaneous operation of different imaging modes, Fourier filtering, and other pupil shaping operations.

Abstract: Optical systems for endoscopes, borescopes, dental scopes, and the like which are characterized by having three groups of lenses of positive optical power and an external entrance pupil. Typically, all three groups of lenses are displaced from the pupil and focal planes. As a consequence, the displaced groups take part in the image transfer as well as in the pupil transfer. The optical power requirements can thus be shifted from one group to another, distributing as well as reducing the overall power requirement. Moreover, the aberration correction can also be shared between these groups. The first group, which conventionally has the highest optical power, and consequently a large amount of aberrations to be corrected, can in this way transfer some of the optical aberration correction to the other groups. The sharing of the optical functions and aberration correction results in a fully integrated optical system.

Abstract: The present invention relates to an optical system of a small-sized portable display apparatus in which the exit pupil position is relatively spaced apart from the optical system and the exit pupil's diameter is large. A display apparatus comprises a display element 3 for displaying an image, and an ocular optical system 32 for enlarging an image displayed on said display element or an intermediated image thereof as a virtual image, and is characterized in that the ocular optical system 32 has rotationally asymmetric Fresnel surfaces 21, 22.

Abstract: An aberration-correcting optical relay for an optical system. The relay comprises front and rear converging optical units together with a correcting meniscus or two correcting meniscuses placed symmetrically relative to each other, the meniscus(es) having main faces that are substantially concentric, and preferably exactly concentric, the two converging optical units being placed on a common axis and the correcting meniscus(es) being placed on said axis between the two converging optical units. The front converging optical unit situated upstream from the correcting meniscus(es) is placed in such a manner that the distance from an image point of the portion of the optical system upstream from the optical relay to the front converging optical unit is equal to the focal length of the front converging optical unit, said unit thus transforming a beam coming from said image point into a parallel beam.

Abstract: The relay optical system comprises, in order from the intermediate image position I toward the the exit pupil EXP side, a first unit G1 having a negative refracting power and a second unit G2 having a positive refracting power, wherein the distance from the rearmost surface of the second unit to the exit pupil position is at least 30 mm. The relay optical system allows a photographing apparatus to be mounted on a microscope without the microscope and the photographing apparatus excluding each other from their predetermined positions.

Abstract: A microscopic optical system which is used in an ultraviolet range of short wavelengths and has good off-axis performance, such as chromatic aberration of magnification. The optical system has an objective optical system for forming an intermediate image of a specimen and a relay optical system for imaging the intermediate image again. The relay optical system has a first lens group and a second lens group, and at least one convex lens of at lease one of the first and second lens groups is formed from quartz.

Abstract: In order to provide a microscope episcopic illumination device and a microscope therewith having simple structure, having an aperture diaphragm and a field stop, and being capable of setting optimum light source magnification in accordance with change of an image surface size required for from eyepiece observation to TV observation. The microscope episcopic illumination device has a light source, a collector lens, an aperture diaphragm, a light source image forming lens portion for forming an image of the light source in the vicinity of the aperture diaphragm, pupil relay lens groups for re-forming the image of the light source formed in the vicinity of the aperture diaphragm in the vicinity of a pupil surface of an objective lens, and a field stop. The lens portion is a lens system with a variable finite focal distance, and varies a projection magnification of a ratio of the re-formed image of the light source in the vicinity of the pupil surface to the light source by changing the focal distance thereof.

Abstract: An endoscopic optics fitted with lens elements and securing device to secure the element positions against shifting in case of being impacted. The securing device is a circumferentially expansible tube that jointly encloses, at least at one abutment surface, the adjoining ends of two lens elements while being of a lesser inside diameter than the outside diameter of the lens elements and being permanently prestressed against them.

Abstract: A direct-view optical microscope system is provided which uses high-energy light from a phenomenon known as non-resonant Raman scattering to illuminate a living biological specimen. One embodiment of the system combines two discrete light sources to form a combined incident light source for the microscope. The system includes a method and apparatus for modulating the intensity of the scattered light when two light waves are combined to produce the incident light. By varying the frequency of the two source light waves, the intensity of the combined Raman-scattered light can be modulated to achieve finer resolution.

Abstract: To use a beam splitting optical system smaller than the conventional beam splitters and to set a longer optical path between a concave, reflective mirror and an image plant. A light beam from an object surface travels through a first converging group to enter a beam splitter, and a light beam reflected by the beam splitter is reflected by a concave, reflective mirror to form an image of patterns on the object surface inside the concave, reflective mirror. A light beam from the image of the patterns passes through the beam splitter and thereafter forms an image of the patterns through a third converging group on an image plane.