Abstract: An eyepiece (2) for viewing a flat image, which eyepiece (2) has a wide field of view and which eyepiece (2) comprises a cemented doublet of reflecting and refracting optical components, the reflecting and refracting optical components being such that they are each of a different refractive index whereby chromatic aberrations and spherical aberrations are reduced.

Abstract: A pair of variable-powered binoculars include a pair of objective lens systems; a pair of prism systems, each of the prism system inverting an image that advances through the corresponding objective lens systems, from an inverted image to an erecting image; a pair of concave adjusting lenses, each of the concave adjusting lenses placed between a focus formed by the corresponding objective lens system and the corresponding prism system, so that each of the concave adjusting lenses is movable along the optical axis formed by the corresponding objective lens system and the corresponding prism system; and a pair of ocular lens systems, each of the ocular lens systems placed on the optical axis, so that each ocular lens system is movable along the optical axis closer to or away from the corresponding concave adjusting lens, synchronizing with a movement of the corresponding concave adjusting lens.

Abstract: A real-image finder optical system includes a positive objective optical system, an erecting optical system, and a positive eyepiece optical system, thereby an object image, which is formed by the objective optical system, and is upside down and reversed from left to right, is reinverted by the erecting optical system to the proper orientation. The erecting optical system includes a plurality of reflection surfaces, at least one of which is provided along an optical path on the object side with respect to the position where the object image is formed, and at least another of which is provided along an optical path on the eyepiece side with respect to the position where the object image is formed. The eyepiece optical system includes a positive lens element having a transverse magnification of more than 1.0 provided between the object image (finder image) and the reflection surface provided on the eyepiece side with respect to the position where the object image is formed.

Abstract: A real image type finder optical system includes an objective lens group having positive refracting power and an eyepiece lens group having a positive refracting power. The objective lens group includes a first group consisting of a negative lens, a second group consisting of a positive lens, a third group consisting of a positive lens and a fourth group having a negative refracting power and forming part of an image inverting optical system. Upon zooming from a wide-angle end to a telephoto end, the first and fourth groups remain fixed and the second and third groups move. The eyepiece lens group comprises a fifth group that forms part of the image inverting optical system and a sixth group having positive refracting power. The resulting real image type finder optical system satisfies specific conditions with respect to the back focus of the first to third groups at the wide-angle end.

Abstract: A real image mode finder optical system is constructed to be independent of a photographing optical system and includes, in order from the object side, an objective optical system with a positive refracting power, a field frame located in the proximity of the imaging position of the objective optical system, and an eyepiece optical system with a positive refracting power. The real image mode finder optical system has an image erecting means, and the focal length of the objective optical system can be made shorter than that of the eyepiece optical system. In this case, the real image mode finder optical system satisfies the following condition: 0.52<mh/fe<1 where mh is the maximum width of the field frame and fe is the focal length of the eyepiece optical system.

Abstract: An eyepiece optical system is interposed between the positions of an intermediate image and a pupil in a finder and includes, in order from the intermediate-image side, a first lens unit having a negative lens located at the most intermediate-image-side position and a second lens unit provided with a path-bending optical member and having positive power as a whole, satisfying the following condition: −20<sf1<0 where sf1 is the shaping factor of the negative lens and is expressed as (r11+r12)/(r11−r12), where r11 is the radius of curvature of the intermediate-image-side surface of the negative lens and r12 is the radius of curvature of the pupil-side surface of the negative lens.

Abstract: The invention relates to a display system wherein a Fresnel lens that forms an eyepiece optical system is curved to correct for decentration aberration, whereby a display screen can be wholly observed even in a decentered state. In the display system, an object image is projected via a relay optical system 2 near the eyepiece optical system 1 so that the exit pupil E1 of the relay optical system 2 is projected via the eyepiece optical system 1 onto an observer's pupil position E0. The eyepiece optical system comprises an optical element having a Fresnel surface. The eyepiece optical system 1 and relay optical system 2 are located such that an axial chief ray emerging from the relay optical system 2 is obliquely incident on the eyepiece optical system 1. The axial chief ray is defined by a light ray emerging from the center of the object, and passing through the relay optical system 2 and then through the center of the pupil E1 of the relay optical system 2.

Abstract: An observation optical system comprises an image display element and an eyepiece optical system which introduces an image formed by the image display element to a center of an eye of an observer without forming an intermediate image, so as to allow the observer to observe the image as a virtual image. The eyepiece optical system is constructed and arranged to bend the optical axis using reflecting surfaces so as to be compact. The image observation optical system can be made compact enough to be usable as an image display unit for a cellular phone or a portable intelligent terminal, and can achieve high image definition and wide field angle while controlling chromatic aberration of magnification to be small.

Abstract: An optical magnifier is provided. One general form of one example embodiment includes two lens elements, at least two aspheric surfaces, and at least one diffractive surface. Another general form of another example embodiment includes three lens elements, and at least three aspheric surfaces. At least two of the aspheric surfaces can be simple conics. The optical magnifier, suitable for use in an electronic display system, has an apparent field of view of at least +/−10 degrees; a magnification of at least 15×; a back focal length of at least 5 mm; and an eye relief greater than the effective focal length of the optical magnifier. The lens elements can be made from plastic.

Abstract: A projection lens 2 comprises practically six lenses; a single lens having negative refracting power serving as a first lens 10, a single lens having positive refracting power serving as a second lens 20, a single lens having negative refracting power serving as a third lens 30, a compound lens having positive refracting power, consisting of a first component lens 41 having negative refracting power and a second component lens 42 having positive refracting power and cemented to the first component lens 41, and serving as a fourth lens 40, and a single lens having positive refracting power serving as a fifth lens 50, arranged in that order from the side of a screen toward a display device. A part of the projection lens 2 on the side of the display device is substantially telecentric, and a surface 11, on the side of the display device, of the first lens 10, and a surface 41, on the side of the display device, of the second component lens 42 of the fourth lens 40 are aspherical.

Abstract: A light-projecting device comprises a superimpose-plate, which is put on a focusing glass. A hollow pentagonal mirror has a roof reflecting plane, reflecting a light beam passing through the focusing glass and the superimpose-plate, a third reflecting plane, reflecting the light beam reflected on the roof reflecting plane, and an emergent opening through which the light beam reflected on the third reflecting plane passes. An illumination light beam output from a light source of a light-projecting optical system is reflected on a light-projecting prism, and radiated from the emergent opening to the third reflecting plane. The illumination light beam is reflected on the third reflecting plane and the roof reflecting plane, and is approximately perpendicularly radiated on the superimpose-plate.

Abstract: An optical apparatus includes an optical system for performing variable power by one lens group or integrated lens groups; a variable optical-characteristic element; a drive circuit for driving the variable optical-characteristic element; and a picture element, wherein the apparatus is constructed by providing a predetermined resolution chart with a known distance, feeding drive information to the variable optical-characteristic element in accordance with the distance, photographing images of the resolution chart, and adjusting and fixing the position of the picture element so as to substantially maximize the contrast of the images.

Abstract: An eyepiece lens is constructed with, in order from an entrance side for light to an exit side for light, first, second, third, fourth and fifth lens units of negative, positive, positive, positive and positive refractive powers, respectively. Each of the first, second, third, fourth and fifth lens units of the eyepiece lens is composed only of one lens or a cemented lens, and an intermediate image by an objective lens is formed between the second lens unit and the third lens unit. An objective lens is constructed with, in order from an object side to an image side, first and second lens units of positive and negative refractive powers, respectively. The first and second lens units of the objective lens are composed of one positive lens and of one positive lens and one negative lens, respectively, and the various conditions are appropriately set. An optical apparatus includes the eyepiece lens, the objective lens and an erecting prism.

Abstract: In a scanning display apparatus an image signal source produces an image signal. A light emitter is coupled to the image signal source and responsive to the image signal to emit light. A lensing system receives light from the light emitter and passes exiting light. A scanner scans the image light. A light sensor detects intensity of background light. A controller adjusts intensity of the image light in response to the detected background light intensity.

Abstract: An optical adapter comprises an adapter body and a lens member. The lens member is a cylindrical lens having one or more curved surfaces, and has a function to extend an optical image in a horizontal direction. A taking lens and a viewfinder are arranged vertically, and the optical axes of the taking lens and the viewfinder coincide with each other in the horizontal direction. When the adapter body is attached to the front side of the lens-fitted photo film unit, the front surfaces of the taking lens and the viewfinder are covered with the lens member. The center of the lens member in the horizontal direction coincides with centers of the taking lens and the viewfinder in the horizontal direction.

Abstract: A camera has a rangefinder device having an optical system constituted by a plurality of optical elements and a diopter adjustment mechanism capable of adjusting the observation diopter of the rangefinder device by operation by the user from outside the camera. In addition, there are provided an operating member that operates the diopter adjustment mechanism and an adjustment mechanism that effects adjustment such that the observation diopter of the rangefinder device is at a predetermined value when the operating member is in a prescribed position. By this means, a camera having a diopter adjustment mechanism whereby the relative positional relationship of the operating member and driven member can always be ensured such that the observation diopter gets equal to the predetermined observation diopter that is to be set when the operating member is arranged in the prescribed position. This can be realized by a straightforward construction.

Abstract: A reduction in utilization efficiency of laser beams emitted from laser emission portions of illumination means is limited and an exposure surface is exposed by beam spots with desired spot diameters and spot forms. At an exposure head, first microlenses are arranged in a two dimensional manner so as to correspond to micromirrors at a DMD, and apertures are arranged in a two dimensional manner at back side focusing positions of the first microlenses. With this exposure head, light source images, which are formed to be very small at back side focusing positions of the first microlenses by the first microlenses, are projected onto the exposure surface, and these light source images serve as beam spots BS and expose the exposure surface.

Abstract: An objective lens unit manufacturing apparatus for manufacturing an objective lens unit, with a numerical aperture not less than 0.7, made up by a plurality of lenses, includes a positioning mechanism (31) for positioning one lens (2) in a cylindrically-shaped lens holder (3) of a synthetic resin material, using another lens (1), already mounted and secured to the lens holder, as a reference, and for securing the one lens to the lens holder, for setting relative positions of the one and the other lenses.

Abstract: A real image mode finder optical system is constructed to be independent of a photographing optical system and includes, in order from the object side, an objective optical system with a positive refracting power, a field frame located in the proximity of the imaging position of the objective optical system, and an eyepiece optical system with a positive refracting power. The real image mode finder optical system has an image erecting means, and the focal length of the objective optical system can be made shorter than that of the eyepiece optical system. In this case, the real image mode finder optical system satisfies the following condition: 0.52<mh/fe<1 where mh is the maximum width of the field frame and fe is the focal length of the eyepiece optical system.

Abstract: A viewfinder eyepiece for a camera having a video signal tap, particularly a professional high definition video camera, for viewing the display screen of a display device, such as a CRT, in the viewfinder. The eyepiece includes a negative powered lens on an optical axis and positioned adjacent the display screen, a first positive powered lens on the optical axis is spaced from the negative powered lens is located at an eye-viewing end of the eyepiece, and a second positive powered lens positioned on the optical axis between the negative powered lens and the first positive powered lens. The second positive lens is mounted in the eyepiece to be movable along the optical axis in the space between the negative powered lens and the first positive powered lens for adjusting the focus on the display screen through the eyepiece.

Abstract: When a forming a bevel on a lens, the value of the bevel curve is calculated based on the value of the curve of the concave face, a reference axis of the bevel curve is determined to be in the same direction as the curvature of the concave face, a reference position on the peripheral edge of the lens in the first portion having the minimum thickness is determined based on the thickness of the first portion, a correction for the initial reference axis of the bevel curve is obtained, an angle of inclination from the direction of the initial reference axis of the bevel curve is obtained based on the correction and the locus of the bevel is determined based on the value of the bevel curve, the reference position and the angle of inclination.

Abstract: An observation optical system comprises an image display element 5 and an eyepiece optical system which introduces an image formed by the image display element 5 to a center of an eye of an observer without forming an intermediate image, so as to allow the observer to observe the image as a virtual image. The eyepiece optical system is constructed and arranged to bend the optical axis using reflecting surfaces so as to be compact. The optical axis lies in a plane, with respect to which the optical system is formed symmetric. The optical system includes a prism 3 having an entrance surface 33, a plurality of curved reflecting surfaces 31, 32 and an exit surface 31. The reflecting surface 32 is provided with a volume hologram (HOE) 4.

Abstract: An eyepiece (2) for viewing a flat image, which eyepiece (2) has a wide field of view and which eyepiece (2) comprises a cemented doublet of reflecting and refracting optical components, the reflecting and refracting optical components being such that they are each of a different refractive index whereby chromatic aberrations and spherical aberrations are reduced.

Abstract: An ocular zoom lens is formed of three lens groups, of positive, positive, and negative refractive power, in order from the eye-point side. The second and third lens groups are moved along the optical axis in opposite directions during zooming, and the second lens group is formed of, in order from the eye-point side, a biconvex lens and a negative meniscus lens with its concave surface on the eye-point side, with the surfaces of the biconvex lens and the negative meniscus lens that face one another having different radii of curvature and being positioned on-axis with an intervening air space. Various conditions are preferably satisfied in order to ensure sufficient eye relief using a relatively small number of lens elements while providing increased freedom of design and enabling favorable correction of aberrations even for wide image angles.

Abstract: Eyepiece variable focal length optics comprise, in order from the objective optics, a negative lens group, a positive lens group, a positive lens group and a positive lens group; during variable focal length from longest focal length side to shortest focal length side, the first lens group moves monotonically toward the objective optics, the second lens group moves monotonically toward the eye, and the third lens group moves toward the eye in such a way that the distance from the second lens group is first increased and then decreased; the fourth lens group is stationary. The eyepiece variable focal length optics further satisfies the following condition (1): 0.

Abstract: An eyepiece lens system using an aspherical lens can be formed at a low cost, having an eye relief equivalent to 80% or more of the focal length of the entire eyepiece lens system, with aberrations satisfactorily corrected up to the circumference of the field of view, as well as a telescope, a binocular and a microscope. The eyepiece lens system comprises a cemented lens and a positive lens, and at least one of the lens surfaces is formed aspherical. The aspherical surface is a hybrid type spherical surface formed by applying a synthetic resin layer on a basic spherical surface made of glass. There are also provided a telescope, a binocular and a microscope employing such eyepiece lens system.

Abstract: A head-mounted display device and an eyepiece optical system suitable for use in the head-mounted display device is provided. The eyepiece optical system is capable of enlarging and displaying, to an eye of an observer, an image displayed on a two-dimensional display element. The eyepiece optical system includes, sequentially from the observer's eye, an aspherical resin lens, a spherical glass lens, and a polarization-conversion element disposed between the spherical glass lens and the two-dimensional display element. On a surface of the aspherical resin lens is provided a circularly-polarized-light-selective reflecting-transmitting surface for selectively reflecting and transmitting projection image light from the two-dimensional display element, depending on a rotation direction of circularly-polarized rays of the projection image light.

Abstract: A viewfinder eyepiece for a camera having a video signal tap, particularly a professional high definition video camera, for viewing the display screen of a display device, such as a CRT, in the viewfinder. The eyepiece includes a negative powered lens on an optical axis and positioned adjacent the display screen, a first positive powered lens on the optical axis is spaced from the negative powered lens is located at an eye-viewing end of the eyepiece, and a second positive powered lens positioned on the optical axis between the negative powered lens and the first positive powered lens. The second positive lens is mounted in the eyepiece to be movable along the optical axis in the space between the negative powered lens and the first positive powered lens for adjusting the focus on the display screen through the eyepiece.

Abstract: The invention relates to a compact, high-performance yet wide-field real image type zoom finder comprising a positive objective optical system Ob and a positive eyepiece optical system Ep and further including an image-inverting means for erecting an real image formed by the objective optical system. The objective optical system Ob comprises a plurality of moving groups G2 and G3, and the eyepiece optical system Ep comprises positive reflecting surfaces, at least one of which is defined by a rotationally asymmetric surface, and satisfies conditions 1.25<dEP/fOC<2.0 and 0.5<lOC/fOC<1.3 where dEP is the distance as measured along an axial chief ray from a final surface to an eye point of the eyepiece optical system, fOC is the focal length of the eyepiece optical system, and lOC is the length as calculated on an air basis and measured along an axial chief ray from an intermediate image-formation plane to the final surface of the eyepiece optical system.

Abstract: A viewfinder optical system directs a luminous flux emanating from an image plane to a pupil. The viewfinder optical system has an eyepiece optical system. The eyepiece optical system enlarges an image in order to be viewed by the pupil. The eyepiece optical system has a first lens unit, a second lens unit and a third lens unit. The first lens unit has at least one surface having a positive optical power. The second lens unit has at least one surface having a negative optical power. The third lens unit has a reflecting surface having a positive Optical power.

Abstract: The invention described herein represents a significant improvement for the telescope hobbyist. It provides a remote eyepiece system that enables a user to optically view objects through a telescope while sitting in the comfort of their living room sofa. This is achieved when the user has the present remote wearable mobile eyepiece. An electromagnetic beacon signal communicates the position of the user's eyepiece, software calculates location and how trajectory is needed to send the object light to the user's location, and software instructs micro stepping servomotors to correctly position mirrors accordingly. The components enable the system to track the physical location of the user's eyepiece and to optically direct the light for the object to the user's viewing eyepiece apparatus.

Abstract: In order to provide an eyepiece lens which has a sufficiently long eye relief and a high magnification, there is provided an eyepiece lens for observing an image formed by an objective lens through an erect system, at least comprising a first lens group 4 having a positive refracting power and a second lens group 3 having a negative refracting power in this order from the side of an observer, and satisfying the following condition: −3<SF1<−1  (1) where SF1 indicates a shape factor of the first lens group 4, and SF indicates a shape factor of the lens group, which is defined by: SF=(Rs+RE)/(Rs−RE), where Rs indicates a radius of curvature of a lens surface which is closest to the object side and RE indicates a radius of curvature of a lens surface which is closest to the observer side.

Abstract: An eyepiece, consisting of two lens groups, is lighter in weight and more compact than known previously, yet has aberrations that are favorably corrected despite the eyepiece having a large exit pupil diameter. This is accomplished by including a predetermined diffraction optical element (DOE) surface on one of the optical elements in order to minimize the number of lens elements that are required, while simultaneously ensuring the image is of high quality. Thus, a high quality image may be observed even while walking, riding in a vehicle, or the like. In order from the eye side, the first lens group has positive refractive power with its surface nearest the eye side being convex and its surface farthest from the eye side being concave. The first lens group may be formed of a single lens element or a pair of lens elements that are cemented together. Among the two lens groups, the eyepiece includes at least one negative lens element and at least two positive lens elements.

Abstract: An observation optical system comprises an image display element 5 and an eyepiece optical system which introduces an image formed by the image display element 5 to a center of an eye of an observer without forming an intermediate image, so as to allow the observer to observe the image as a virtual image. The eyepiece optical system is constructed and arranged to bend the optical axis using reflecting surfaces so as to be compact. The optical axis lies in a plane, with respect to which the optical system is formed symmetric. The optical system includes a prism 3 having an entrance surface 33, a plurality of curved reflecting surfaces 31, 32 and an exit surface 31. The reflecting surface 32 is provided with a volume hologram (HOE) 4.

Abstract: An image display apparatus forms illumination light from a light source into image light by using a reflective display device, and directs the image light through an eyepiece optical system to an eye to present a virtual image of the image carried by the image light. To realize an image display apparatus of this type that is compact, affords a sufficiently long eye relief, and offers wide-field, high-quality images, a combiner for making the optical path of the illumination light from the light source overlap with that of the image light is disposed inside the eyepiece optical system, a positive lens is provided in the rear potion of the eyepiece optical system between the display device and the combiner, a concave reflective surface is provided in the front portion of the eyepiece optical system between the combiner and the observation point, and the eyepiece optical system is designed to be overtelecentric as a whole.

Abstract: The invention relates to an image transmission system for endoscopes and similar viewing tubes with at least one rod lens (2) and at least one additional lens system (3). 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 (2) 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: The improved eyepiece variable focal length optics comprises, in order from objective optics with which it is used in combination, a negative first lens group, a positive second lens group and a positive third lens group, the first and second lens groups moving in opposite directions along the optical axis during variable focal length but the third lens group being stationary, and the eyepiece variable focal length optics satisfies the following conditions (1) and (2):

Abstract: The improved eyepiece variable focal length optics comprises, in order from objective optics with which it is used in combination, a negative first lens group, a positive second lens group and a positive third lens group, the first and second lens groups moving in opposite directions along the optical axis during variable focal length but the third lens group being stationary, and the eyepiece variable focal length optics satisfies the following conditions (1) and (2): 2.0<f3/f2<4.0  (1) 7.0<L12/f(h)  (2) where f2 is the focal length of the second lens group, f3 is the focal length of the third lens group, f(h) is the shortest focal length of the overall eyepiece variable focal length optics, and L12 is the axial air gap between the first and second lens groups at the shortest focal length. The eyepiece variable focal length optics achieves a variable power ratio of about three and yet is compact and allows for adequately large apparent visual field and eye relief.

Abstract: A head-mounted display device and an eyepiece optical system suitable for use in the head-mounted display device is provided. The eyepiece optical system is capable of enlarging and displaying, to an eye of an observer, an image displayed on a two-dimensional display element. The eyepiece optical system includes, sequentially from the observer's eye, an aspherical resin lens, a spherical glass lens, and a polarization-conversion element disposed between the spherical glass lens and the two-dimensional display element. On a surface of the aspherical resin lens is provided a circularly-polarized-light-selective reflecting-transmitting surface for selectively reflecting and transmitting projection image light from the two-dimensional display element, depending on a rotation direction of circularly-polarized rays of the projection image light.

Abstract: A lens design form is used for a viewing optical system or magnifier that includes a cemented doublet and a weak aspheric element, for example, made of acrylic, and having a diffractive kinoform surface superimposed on the surface profile of the aspheric element. The design significantly reduces both chromatic aberrations and minimizes most of the monochromatic aberrations of the optical system or magnifier. By allowing the lens design form to produce an image on a curved surface, optical performance is improved further over the prior art systems because this allows the elements in the system to control the image blurring aberrations rather than having to also control field curvature. The human eye can accommodate for the curved field, and thus the curved field does not reduce image quality, but instead allows image quality to be enhanced. The viewing optical system also can be used for image projection.

Abstract: A real image type view finder comprising an objective optical system which has positive refractive power and forms an intermediate image, an image erecting optical system which erects the intermediate image and an eyepiece optical system which leads the intermediate image to an observer's eye, in which the objective optical system comprises a first positive lens unit, a second negative lens unit, a third negative lens unit and a fourth positive lens unit, moves the second lens unit and the third lens unit for a magnification change, has a vari-focal ratio on the order of 4, and has favorable optical performance over an entire zooming region.

Abstract: Eyepiece variable focal length optics comprise, in order from the objective optics, a negative lens group, a positive lens group, a positive lens group and a positive lens group; during variable focal length from longest focal length side to shortest focal length side, the first lens group moves monotonically toward the objective optics, the second lens group moves monotonically toward the eye, and the third lens group moves toward the eye in such a way that the distance from the second lens group is first increased and then decreased; the fourth lens group is stationary.

Abstract: The invention relates to a microscope eyepiece with theoretically reduced astigmatism in a compensating optical system. The inventive eyepiece has 10× magnification, a sight field (SFZ)≦25 and a Petzval sum (SP) of 0.014≦SP≦0.021. Said eyepiece comprises a special field lens placed in front of a field stop and a negative lens in the eye lens section placed behind said field stop. The inventive field lens is embodied in the form of a simple, thick, positively diffracting meniscus which is convex in relation to the field stop and provided with the following field lens factor: 0.95≦beta′≦1.05. The eye lens section can be displaced in relation to the field stop to enable diotropic adjustment. Special, advantageous embodiments of the field lens and examples of embodiments of the microscope eyepiece, complete with structural data, are described.

Abstract: An eyepiece lens system using an aspherical lens can be formed at a low cost, having an eye relief equivalent to 80% or more of the focal length of the entire eyepiece lens system, with aberrations satisfactorily corrected up to the circumference of the field of view, as well as a telescope, a binocular and a microscope. The eyepiece lens system comprises a cemented lens and a positive lens, and at least one of the lens surfaces is formed aspherical. The aspherical surface is a hybrid type spherical surface formed by applying a synthetic resin layer on a basic spherical surface made of glass. There are also provided a telescope, a binocular and a microscope employing such eyepiece lens system.

Abstract: A compact, real-image-type zoom finder having a high zoom ratio and high optical performance is provided. The finder is formed of an objective optical system and an erecting eyepiece. The objective optical system is formed of, in order from the object side, a first lens element having negative refractive power with a concave surface on the object side, a second lens element having positive refractive power, and a third lens element that is a positive meniscus lens with its convex surface on the object side. The erecting eyepiece is formed of an erecting prism having refractive surfaces integrally formed on the input end and output end of the erecting prism. The magnification of the finder is changed by moving the second lens element along the optical axis, and the third lens element is moved along the optical axis in order to adjust for what would otherwise be a shifting in image surface position with the change in magnification.

Abstract: A real image mode finder includes an objective optical system with a positive refracting power, an image erecting optical system with a roof reflecting section, a first planar reflecting section, and a second planar reflecting section, and an eyepiece optical system with a positive refracting power. The image erecting optical system is constructed so that the optical axis does not cross in this optical system and a ray of light from the objective optical system is introduced into the roof reflecting section, the first planar reflecting section, and the second planar reflecting section in this order. The real image mode finder also satisfies the following conditions: 49°<&ggr;<62.5° 20°<&agr;<30° where &ggr; is an angle of incidence of an axial ray of light on the second planar reflecting section and &agr; is an angle of incidence of the axial ray of light on the roof ridgeline of the roof reflecting section.

Abstract: An eyepiece lens is constructed with, in order from an entrance side for light to an exit side for light, first, second, third, fourth and fifth lens units of negative, positive, positive, positive and positive refractive powers, respectively. Each of the first, second, third, fourth and fifth lens units of the eyepiece lens is composed only of one lens or a cemented lens, and an intermediate image by an objective lens is formed between the second lens unit and the third lens unit. An objective lens is constructed with, in order from an object side to an image side, first and second lens units of positive and negative refractive powers, respectively. The first and second lens units of the objective lens are composed of one positive lens and of one positive lens and one negative lens, respectively, and the various conditions are appropriately set. An optical apparatus includes the eyepiece lens, the objective lens and an erecting prism.

Abstract: A negative ocular having a positive eye-side lens element positioned on the side of the user's eye and a positive field lens element positioned on the side of the object whereby an intermediate image formed by an objective lens system is formed between the eye-side lens element and the field lens element, and whereby the eyepiece lens system satisfies the following conditions: 0.8<L(1+S)/{f1(P+S)}<1.05   (1) 0.5<S(1—1/P)/(1+S)   (2) wherein S=&ngr;1/&ngr;2; P=f2/f1; f1 designates the focal length of the eye-side lens element; f2 designates the focal length of the field lens element; &ngr;1 designates the Abbe number of the eye-side lens element; &ngr;2 designates the Abbe number of the field lens element; and L designates the distance between the principal points of the field lens element and the eye-side lens element.

Abstract: A finder optical system for a single lens reflex camera is provided with a photographing optical system, a beam splitter for splitting light passed through the photographing optical system. First light deflected by the beam splitter forms a primary image at a position downstream from the beam splitter. Second light passed through the beam splitter is incident on a CCD. A relaying optical system is arranged on an optical path of the light deflected by the optical element to relay the primary image to form a secondary image. A reflection surface is arranged between the relaying optical system and an eyepiece optical system The reflection surface deflects light, which is directed from the relaying optical system, toward the eyepiece optical system, to proceed in a direction parallel with an optical axis of the photographing optical system. The secondary image is formed between the reflection surface and the eyepiece optical system.

Abstract: A real image finder comprises an objective lens system including a convex lens and having a positive power as a whole, an erect image prism having four reflection surfaces and inverting an inverted image of an object formed through the objective lens system in horizontal and vertical directions, and an eyepiece having a positive power, wherein the erect image prism and the eyepiece lens is integrated by forming an eyepiece surface on the image side of the erect image prism. To provide a fixed magnification finder, the objective lens system consists of a single lens having a positive power and at least one aspherical surface. To provide a zoom finder, the objective lens system comprises a first lens with a negative power and a second lens with a positive power arranged in this order from the object side. The second lens is moved along the optical axis for zooming.