Abstract: A method for fabricating a supermirror for forming a neutron guide. In the method, a neutron supermirror, which is widely used in the formation of thin films in cold neutron guides and the spectrometer field, is fabricated with nickel thin films and titanium thin films, having varying thickness, using a combination of monochromator structures in which nickel thin films and titanium thin films, having the same thickness, are stacked in the form of periodic structures. According to the method, a combination of monochromator structures having a variety of different thicknesses is formed, such that the amount of the overlap of peaks due to the monochromator structures can be adjusted to increase reflectivity, and some of the monochromator structures can be removed during the fabrication of the supermirror to make it easy to extract monochromatic beams, such that it is easy to fabricate a transmission monochromator, rather than a reflection monochromator.

Abstract: An optical system having a novel imaging method of forming an image of a subject of projection in space the same as if the image were being reflected from a mirror where a mirror does not actually exist is provided, the optical system being provided with a light beam redirecting surface that functions to transmit light while refracting the light and form a real image at a plane-symmetric position, and a mirror surface arranged facing the light beam redirecting surface; in which, by transmitting light emitted from the subject of projection through the light beam redirecting surface, reflecting the transmitted light at the mirror surface, and again transmitting the reflected light through the light beam redirecting surface, an image of a subject of projection arranged at a position on an observation side opposite the mirror surface arranged on the other side across the light beam redirecting surface is formed at a position that is plane-symmetric to the mirror surface with respect to the light beam redirecting

Abstract: A projection optical system for use in an image projection apparatus illuminating an image display panel forming an image in accordance with a modulating signal with illumination light from a light source. The projection optical system includes first and second optical systems arranged along an optical path defining an upstream-downstream direction in the order described from upstream to downstream on the downstream side of the image display panel. The first optical system includes at least one dioptric system and has positive power. The second optical system includes at least one reflecting surface having power and has positive power. The image formed by the image display panel is formed as an intermediate image in the optical path, and the intermediate image is magnified and projected.

Abstract: An optical beam homogenizer having an adjustable homogenizer chamber for selectively producing different sized homogenized output beams and related methods in accordance with one or more embodiments is described herein.

Abstract: A two-dimensional wedge shaped UV and IR filter is formed by or substantially same size pieces of glass forming a two-dimensional wedge. The wedge reflects radiation in four different directions.

Abstract: A mirror includes a substrate of transparent material defining a first side and a second side. The second side includes a primary mirror surface defining a first focal axis and a secondary mirror surface defining a second focal axis. The second focal axis is directed in a direction different than the first focal axis.

Abstract: An alignment system for side view mirrors featuring a mirror with regions of diverse curvature, with an upright alignment line in a region of greater curvature. The side view mirror is set up so that the side of a user's vehicle lies entirely on the side of the alignment line closest to the vehicle. This generates a cone of vision to the rear of the vehicle which overlaps with the cone of vision from a rear view mirror such that blind spots are greatly reduced or eliminated.

Abstract: The binoculars of the present invention comprise two optical units; one optical unit for each eye. Each optical unit comprises a first reflective lens element and a second reflective lens element, wherein at least one of the reflective lens elements is a Micromirror Array Lens. The binoculars of the present invention provide focusing and/or zoom functions without or with minimal macroscopic mechanical lens movement.

Abstract: A reflection optical system placed between a light valve 5 and a screen 4, wherein curved surfaces are only three reflection surfaces of first to third mirrors 1 to 3, and satisfies the following: (1) ?L<20 degrees, (2) 25 degrees<?UL<55 degrees, (3) 20 degrees<?M1<55 degrees, (4) 15 degrees<?M2<50 degrees, (5) 8 degrees<?M3<30 degrees, (6) ?L<15 degrees, (7) 30 degrees<?UL and (8) 7.5 degrees<|?F|, where ?L: minimum angle which a light beam of pupil center forms with respect to the enlargement side image surface; ?UL: difference between maximum and minimum angles which a light beam of pupil center forms with respect to the enlargement side image surface; ?M1, ?M2 and ?M3: deviation angles of the light beam of pupil center passing the center of the reduction-side image surface in first to third mirrors 1 to 3; and ?F: reduction-side pupil divergent angle.

Abstract: An observing device for observing a flow field in a detection space is provided. The observing device includes a light source generating a light beam, a light-deflecting device deflecting the light beam, and a light sheet-generating component receiving the light beam deflected by the light-deflecting device and generating a light sheet in the detection space corresponding to the deflected light beam.

Abstract: A terrestrial imaging device includes an objective lens which accepts light within an intrinsic angular field of view onto a focal plane and two pairs of plane mirrors. The first pair of plane mirrors reflects a first light incoming ray sequentially to produce first and second reflected light rays within a roughly horizontal plane, the second reflected ray being focused by the objective lens on the focal plane. The second pair of plane mirrors reflects a second incoming ray sequentially to produce third and fourth reflected light rays within a roughly vertical plane, the fourth reflected light ray being focused by the objective lens on the focal plane.

Abstract: A three-dimensional light reflection plate that can successfully prevent deformation of the light reflection plate, reduce initial cost and product cost, and facilitate increase in size and reflectance. The light reflection plate includes a bottom plate in which a plurality of mutually parallel slit holes are formed on a flat, light-reflective plate material and a mountain plate that is rectangular from a planar view of which a width direction cross-sectional shape is a mountain shape and in which insertion sections are formed in both width-direction end sections. The mountain plate is fixed to the bottom plate by the insertion sections of the mountain plate being inserted into the slit holes of the bottom plate.

Abstract: This invention deals with novel method and apparatus for positioning and motion control of the elements (mirrors) of a Fresnel reflector solar concentrator tracking heliostat array wherein the elements are suspended with the center of mass below the swivel point, or have an internal-swivel. This achieves an advantageous natural vertical stability. The torque to produce angular deflection, and rotational motion is provided separately by an electric wind force due to electrons, ions, and/or neutrals; or in combination with an induced and/or permanent dipole coupling to an electronic grid. Thus forces and torques are produced without the use of internal moving parts such as in motors. The instant invention exceeds the capability of conventional systems. It is ideally suited for maximization of solar energy focused by a low-profile concentrator array onto a receiver. Since there are no internal moving parts, the instant invention provides less costly and greater ease of manufacture.

Abstract: A mirror may have hole(s) in or passing through its viewing surface. A video remote may be associated with the mirror, especially as configured with the hole(s). A gas, typically an inert gas, may be passed about or through the mirror system, for example, through one or more of the hole(s) through the viewing surface. The mirror may be part of a mirror system, which can be combined with a welding torch. Obscured sites may be inspected and/or welded therewith.

Abstract: A displaying method of a digital light processing (DLP) projector includes the steps of: providing a light modulation device including a driver printed circuit board and a digital micromirror device (DMD), wherein the DMD includes a plurality of micromirrors each having a first stable state and a second stable state, and a predetermined light incident direction, the DMD is installed on the driver printed circuit board; providing an illumination light beam being incident on the DMD along an operating direction different from the predetermined light incident direction, modulating the illumination light beam to an imaging light beam by the DMD and directing the imaging light beam to a projection lens for projecting an image. A DLP projector made thereby has a relatively lower manufacturing cost.

Abstract: A system and method for increasing contrast in displays using micromechanical light modulators. Contrast is enhanced by an optical system that uses polarization to discriminate unmodulated light. Contrast obtained from polarization sensitive components of an optical system has a multiplicative effect on contrast already available.

Abstract: A projection system includes a modulator and an Offner relay. The modulator is to modulate light in accordance with sub-frames of a frame of image data. The Offner relay is to differently aim, in accordance with each sub-frame, the light as modulated.

Abstract: A side mirror assembly for a truck has a housing retaining an upper mirror, a central mirror, and a lower mirror, each of which is motorized and independently adjustable. The assembly also includes a chain driven wiper blade that will wipe across all three mirrors, and a dispenser for dispensing washer fluid on the mirrors. Around the perimeter of the housing are one or more connectors to with electrical devices attachable to the mirror housing can be connected.

Abstract: An interferometer system includes an optical bench and at least two mirror structures, being patterned from one or more layers on the optical bench and erected to extend substantially perpendicularly to the bench to define two interferometer arms to provide a Micro-Electro-Mechanical Systems (MEMS) interferometer. The MEMS interferometer is further implemented in a Fourier transform spectrometer, which includes a common housing containing the interferometer and a gas cell, possibly including a preconcentrator.

Abstract: Equalization device for the optical pathways of parallel optical beams (f1, f2) between two planes (P1, P2), including a plane of reflection. These beams have an impact (A1, A2, B1, B2) with the planes. It comprises parallel mirrors each intercepting one of the beams at a point (O1, O2). Each beam has a first section (f11, f12) between the plane of reflection (P1) and a mirror, and a second section (f12, f22) between the mirror and the other plane (P2). Two mirrors and the beam sections they intercept allow the two points (O1, O2) to be separated by a distance (d?), parallel to a distance (d?) separating two auxiliary beams (f1?, f2?) symmetric to one of the first sections relative to a normal to the plane of reflection at the associated impact, and allow angle (?) of the mirrors with the beams to verify: d?(1?cos 2?)=d?[sin 2?(tg??sin 2?)?cos 2?]? being the angle between the sections and a normal to the plane of reflection at the impact.

Abstract: A system and method are used to pattern light using an illumination system, an array of individually controllable components, and a projection system. The illumination system supplies a beam of radiation. The array of individually controllable elements patterns the beam. The array of individually controllable elements comprises mirrors having first and second steps on opposite edges. The projection system projects the patterned beam onto a target portion of an object. In various examples, the object can be a display, a semiconductor substrate or wafer, a flat panel display glass substrate, or the like, as is discussed in more detail below.

Abstract: The present invention provides a reflector having a light-diffusing property which suppresses inter-object reflection over a wide angle, and giving particularly high reflectance in an intended range of viewing angle; and to provide a reflection type liquid crystal display device using the same. The reflector includes a plurality of light-reflective concave portions. Each of the concave portions is formed so that an inclination angle (an angle between a plane tangential to a point on a concave surface and the surface of the base material) is maximum on a side portion of the curved surface, and so that the direction of the side portion having the maximum inclination angle is on a far side from a view point of an observer.

Abstract: The invention relates to a projection system for guiding light with wavelengths ?193 nm from an object plane to an image plane, comprising at least a first mirror (M1), a second mirror (M2), a third mirror (M3), a fourth mirror (M4), a fifth mirror (M5) and a sixth mirror (M6) centered around an optical axis and being arranged along the optical axis, with the light traveling from the object plane to the first mirror, then from the first mirror (M1) to the second mirror (M2), then from the second mirror (M2) to the third mirror (M3), then from the third mirror (M3), the fourth mirror (M4), then from the fourth mirror to the fifth mirror (M5) and then from the fifth mirror (M5) to the sixth mirror (M6), The invention is characterized in that the first mirror (M1) is arranged along the optical axis (HA) geometrically between the fifth mirror (M5) and the sixth mirror (M6), and the third mirror (M3) is a convex mirror.

Abstract: A method, structure, system of aligning a substrate to a photomask. The method comprising: directing light through a clear region of the photomask in a photolithography tool, through a lens of the tool and onto a set of at least three diffraction mirror arrays on the substrate, each diffraction mirror array of the set of at least three diffraction mirror arrays comprising a single row of mirrors, all mirrors in any particular diffraction mirror array spaced apart a same distance, mirrors in different diffraction mirror arrays spaced apart different distances; measuring an intensity of light diffracted from the set of at least three diffraction mirror arrays onto an array of photo detectors; and adjusting a temperature of the photomask or photomask and lens based on the measured intensity of light.

Abstract: A polygon mirror includes a mounting portion and a plurality of reflective surfaces. The mounting portion is mounted on a rotating body having a support surface. The mounting portion has the shape of a polygonal plate. The plurality of reflective surfaces are arranged around the rotating body so as to surround the rotating body. A plurality of protrusions configured to abut against the support surface of the rotating body are arranged on one side of the mounting portion.

Abstract: In a projection optical system for obliquely performing enlargement projection of an image formed on a display device surface onto a screen surface, a plurality of reflective surfaces are provided, at least one of which is a curved reflective surface having an optical power. Letting the curved reflective surface, out of said at least one curved reflective surface, having the largest effective optical region be the largest curved reflective surface, the reflective surface other than the largest curved reflective surface is slightly decentered with the largest curved reflective surface kept in a fixed state so as to perform pixel shift on the screen surface in a vertical direction, or a horizontal direction, or an oblique direction, or vertical and horizontal directions within the range of a pixel pitch.

Abstract: A non-contact connector (10), having a rotation-side light-emitting element (13) and a rotation-side light-receiving element (14), positioned on a rotating body (1) which rotates about a rotation axis (4), a fixed-side light-emitting element (23) and a fixed-side light-receiving element (24), positioned on a fixed body (2), and a first partial ellipsoidal reflecting mirror (8) installed on the fixed body (2) and a second partial ellipsoidal reflecting mirror (6) installed on rotating body (1), [each] with one focal point positioned on the rotation axis (4).

Abstract: An optical system includes a cylindrical side emitter lens, a reflector and a cylindrical Fresnel lens to produce a substantially uniformly illuminated exit plane with well collimated light in the forward direction. The cylindrical side emitter lens redirects light from a light source, such as a number of light emitting diodes placed in a straight line, into side emitted light along an optical axis that is parallel with the exit plane. The reflector may be a stepped multi-focal length reflector that includes multiple reflector surfaces with different focal lengths based on the surfaces distance to the light source and height to redirect light from the cylindrical side emitter lens to illuminate the exit plane and collimate the light along one axis in the forward direction. The cylindrical Fresnel lens is used to collimate the light along an orthogonal axis in the forward direction.

Abstract: In one embodiment, an electronic device is provided and methods for making the same, as well as devices and sub-assemblies including the same. For example, such an electronic device (FIG. 4) may include a first electronic component (172) designed to be photoactive to a first radiation having a first wavelength, a second electronic component (174) designed to be photoactive to a second radiation having a second wavelength, a first mirror stack (30) adjacent to the first and second electronic components, where the first mirror stack includes a first pair of layers designed to reflect the first radiation and a second mirror stack (40) adjacent to the first and second electronic components, where the second mirror stack includes a second pair of layers designed to reflect the second radiation.

Abstract: A system architecture for large concentrated solar power applications that increases heliostat utilization efficiency and land utilization efficiency is described. Embodiments of the invention include a large heliostat field in which are distributed a number of receiving locations, and wherein there is the assignment of heliostats to receiving locations is dynamic. Embodiments of the invention include dynamically targeting heliostats to receiving locations wherein the target determination process is performed frequently during operation and wherein such dynamic targeting can be utilized to various ends. Embodiments of the invention include configurations wherein cosine losses associated with heliostat pointing are significantly reduced, wherein heliostats may be closely packed without incurring substantial shadowing and blocking losses thereby significantly increasing land utilization, and wherein other benefits are realized.

Abstract: A manufacturing process for enhancing a light reflective rate in a reflective type display device is provided. The manufacturing process comprises steps of: forming a first conductive layer and a first dielectric layer over a substrate; etching the first dielectric layer; polishing the etched first dielectric layer; forming a second conductive layer over the substrate; and patterning the second conductive layer to form a concave mirror on the surface of the second conductive layer.

Abstract: Substrate-guided relays that employ light guiding substrates to relay images from sources to viewers in optical display systems. The substrate-guided relays are comprised of an input coupler, an intermediate substrate, and an output coupler. In some embodiments, the output coupler is formed in a separate substrate that is coupled to the intermediate substrate. The output coupler may be placed in front of or behind the intermediate substrate, and may employ two or more partially reflective surfaces to couple light from the coupler. In some embodiments, the input coupler is coupled to the intermediate substrate in a manner that the optical axis of the input coupler intersects the optical axis of the intermediate substrate at a non-perpendicular angle.

Abstract: A light collecting device adapted for a projection apparatus is provided. The light collecting device at least comprises a light collecting rod that has a body, a longitudinal direction, an incident end, and an emergent end. The incident end comprises an incident surface and a reflecting surface, in which the incident surface is adjacent to the reflecting surface to form an included angle therebetween. The emergent end is opposite to the incident end. Thus, a first light beam passes through the incident surface of the incident end and travels along the body of the light collecting rod towards the emergent end along the longitudinal direction when a second light beam enters into the body of the light collecting rod. The second light beam is reflected by the reflecting surface of the incident end towards the emergent end along the longitudinal direction.

Abstract: Providing a head-up display apparatus capable of receiving a mirror, which projects from a line of an instrument panel when in use, without increasing a receiving section and spoiling a beauty of the instrument panel, and a mirror unit used in the same, a mirror is rotated about an axis perpendicular to a reflecting surface of the mirror so as to project a part of the mirror from the opening when in use, and take in the projected part of the mirror down within the opening when not in use. Thus, the whole mirror can be received in the receiving section only by rotational motion.

Abstract: The present invention provides for a method of producing an optical device by means of electron beam lithography and including the step of varying the characteristics of the electron beam spot during formation of the device and also an apparatus for producing diffractive optical devices and/or holographic devices by means of electron beam lithography and including an electron beam lithograph, controlling and processing means, means for varying the characteristics of the electron beam spot during formation of the device, and wherein the processing means is arranged for compiling and pre-processing data and for providing optimization and allocation control and to optical devices such as those produced thereby.

Abstract: An optical architecture for a high-energy laser that directs a collimated laser beam through an aperture stop at a desired angle. In one embodiment, the optical architecture includes a single tilt mirror and three stationary mirrors that direct the laser beam in one dimension. The laser beam is reflected off of the mirrors in the same plane and is reflected off of the tilt mirror three times. The first two reflections off of the tilt mirror translate the beam and the third reflection causes the beam to be directed at the desired angle. In another embodiment, the optical architecture includes a single tip-tilt mirror and eight stationary mirrors that direct the beam in two dimensions. The laser beam is reflected off of the mirrors in two planes and is reflected off of the tip-tilt mirror three times. The first two reflections off of the tip-tilt mirror translate the beam and the third reflection causes the beam to be directed at the desired angle.

Abstract: The invention concerns an external mirror arrangement comprising a front mirror of the Group of the Directive 2005/27/EG for the visual transmission of a first field of view and for the visual transmission of a second field of view contains a safety mirror. In accord with the invention, the front mirror and the safety mirror are integrated in one mirror head.

Abstract: Disclosed is a mirror unit for a vehicle, which includes a mirror case (10) having a receiving space formed therein; a pivoting bracket (20) axially coupled to an inside of the mirror case (10); a first operating unit (30) installed to a predetermined position in the mirror case (10) to rotate the pivoting bracket (20) as much as 180 degrees by one touch; and front and rear mirrors (40)(45) systematically attached and detached freely to/from both sides of the pivoting bracket (20).

Abstract: A multiple aperture optical system is provided that overcomes many limitations of wide field of view imaging systems. A basic component of the multiple aperture optical system is an “eye strip”, which comprises an array of imaging apertures physically mounted onto a flexible circuit strip and a master processor. Each imaging aperture generates an aperture output based on the imaging aperture's field of view. The master processor takes as input the aperture outputs generated by the apertures on the eye strips, and generates an output in response. In one embodiment, the multiple aperture optical system enables obtaining an omnidirectional image in a structure that is thin and can be physically conformed to an underlying structure.

Abstract: A vehicle side mirror that can visually confirm the blind spot of the main mirror without providing a prism or a fresnel lens on the window glass is provided. The vehicle side mirror is equipped with mirror housing attached to the side of the vehicle body and main mirror attached to the rear surface of mirror housing. The first sub-mirror that reflects the blind spot at the front side of the vehicle is provided on the side surface of mirror housing so as to face the vehicle body and second sub-mirror that reflects the blind spot at the center side of the vehicle is provided at the bottom portion of the rear surface of mirror housing.

Abstract: The present invention is a multipass unipoint optical cell used for the improved analysis of samples by transmission, reflection, Raman or fluorescence spectroscopy by the multiple reimaging of light through the same analysis point. The cell comprises two or more identical optical reimaging elements each consisting of two symmetrically opposing, identical, confocal, and coaxial parabolic reflective surfaces with the property to refocus any ray of light coming from the common focal point onto one of the parabolic surfaces, back to the same focal point by the other parabolic surface at an angle to the incoming ray. Two or more of these reimaging optical elements can be configured around the common focal point to form different multipass unipoint optical cell configurations, all the passes crossing in the analysis point where a sample is brought to interact with light, the effect of said interaction being enhanced in proportion to the number of passes.

Abstract: An improved mirrored bird toy is provided that includes an interior multiple reflecting capacity that can reflect multiple reflections of a pet bird in multiple directions. Exterior exposed edges of the various mirrors may be plastic coated for safety. The lower or bottom mirror may include a cut-out whereby the bird can gain better access to the toy. The toy is mountable, within a cage, to the cage bars using a screw and nut. An orienting gage is disposed on the reverse side below the screw nub.

Abstract: A hitch mirror assembly removably mounted onto a top edge of a vehicle's tailgate, comprising a housing assembly, a mirror assembly within the housing assembly, battery-powered illumination means and a clamp assembly. The vehicle has a hitch ball for towing a trailer that has a hitch ball coupler. When the hitch mirror assembly is mounted, a person is able to view the hitch ball from inside the vehicle's cab with the mirror assembly, while backing up the vehicle to align the hitch ball underneath the hitch ball coupler. The illumination means illuminate the hitch ball if required and reflective strips mounted to the hitch ball coupler reflect the light projecting from the illumination means to make the hitch ball coupler more visible from the driver's position. The clamp assembly removable secures the housing assembly to the vehicle's tailgate and includes an elongated member, a telescopic housing and a clamp member.

Abstract: There is provided an optical module for an objective. The optical module includes (a) a first holding device with an inner circumference, which extends in a first circumferential direction, (b) at least one first supporting device for supporting a first optical element and being fixed at said inner circumference of said first holding device, (c) an annular circumferential first assembly space being defined by displacing said first supporting device once in a revolving manner along said first circumferential direction, (d) at least one second supporting device being provided for supporting a second optical element and being fixed at said inner circumference of said first holding device, and (e) an annular circumferential second assembly space being defined by displacing said second supporting device once in a revolving manner along said first circumferential direction. The first assembly space intersects the second assembly space.

Abstract: In a portable terminal having a photographic function for receiving photographic light from a camera subject and obtaining image data, the portable terminal comprises an optical member receiving photographic light from the camera subject, and a cover member mounted on a slidable basis. The cover member selectively opens and shuts to cover said optical member in accordance with a sliding operation. The cover member has a mirror on a surface of the cover member.

Abstract: A vehicle interior mirror device disposed in a passenger compartment for reflecting a state of rear seats and traffic conditions behind a vehicle. The interior mirror device has reflection restricting means notched in a lower end of the interior mirror device to prevent a face of a passenger from being reflected, so that eyes of passengers seated in seats other than the driver's seat do not meet.

Abstract: A discretely controlled micromirror array lens (DCMAL) consists of many discretely controlled micromirrors (DCMs) and actuating components. The actuating components control the positions of DCMs electrostatically. The optical efficiency of the DCMAL is increased by locating a mechanical structure upholding DCMs and the actuating components under DCMs to increase an effective reflective area. The known microelectronics technologies can remove the loss in effective reflective area due to electrode pads and wires. The lens can correct aberrations by controlling DCMs independently. Independent control of each DCM is possible by known microelectronics technologies. The DCM array can also form a lens with arbitrary shape and/or size, or a lens array comprising the lenses with arbitrary shape and/or size.

Abstract: There is provided an optical system, including a mechanical body (110), a light-transmitting substrate (20) having two major surfaces and edges, embedded in the mechanical body, an optical element (90) for coupling light into the substrate by total internal reflection and a plurality of partially reflecting surfaces (22) carried by the substrate, wherein the partially reflecting surfaces are parallel to each other and are not parallel to any of the edges of the substrate. The system also includes an image capturing device (112), a display source (4), and an image-processing unit (114). The image-capturing device (112) is connected via the image-processing unit (114) to the display source (4).

Abstract: A polygon mirror includes a reflective surface group having n number of reflective surfaces (M(1), . . . , M(n)) formed individually as outer peripheral side faces, a flat portion which shuts one end portion of the reflective surface group, and n number of pin gate traces (L(1), . . . , L(n)) which are provided on the flat portion, correspond to the n number of reflective surfaces, individually, and are kept individually at distances from edge portions at which the reflective surfaces cross the flat portion. There are conditions DM(1)>DL(1)/2, . . . , DM(n)>DL(n)/2 and DM(1)>DL(n)/2, . . . , DM(n)>DL(n?1)/2, where DM(n) is a shortest distance from an edge portion at which the reflective surface M(n) and the flat portion cross each other to the pin gate trace L(n) and DL(n) is a shortest distance between the pin gate trace L(n) and the pin gate trace L(1).

Abstract: According to the present invention, light from a taking lens is reflected by a quick return mirror in a lateral direction of a body unit. Then, after passing through a screen, the light is reflected toward an upper side of the body unit by a second mirror except part of the light. The light reflected by the second mirror is reflected by a third mirror in a direction opposite to a direction in which the light is reflected by the quick return mirror, and is further reflected by a fourth mirror toward an eyepiece located on a back side of the body unit. Part of the light which passing though the screen is taken by an AF sensor unit provided in rear of the second mirror, and an image formation position of an optical image is detected.