Abstract: A variable-power eyepiece optical system, which is used in combination with an objective optical system, includes a negative first lens group, a second lens group having a positive first sub lens group and a positive second sub lens group, and a positive third lens group, in this order from the objective optical system. The first lens group, and the first and second sub lens groups of the second lens group are made moveable along the optical axis upon variable power, while the third lens group is made immoveable. At the time of variable power, the first sub lens group and the second sub lens group move independently of each other in a direction opposite to the direction along which the first lens group moves, and thereby the resultant power of the first and second sub lens groups is varied.

Abstract: An image display apparatus has a display unit and an eyepiece optical system. The display unit displays a two-dimensional image. The eyepiece optical system projects the two-dimensional image into an observer's pupil to enable the observer to view an enlarged virtual image of the two-dimensional image. The optical axis of the eyepiece optical system is decentered from the visual axis of the observer's pupil.

Abstract: The present invention provides a projection lens for projecting light from a light source onto a screen to form a magnified image, including two joined lenses, each of which includes a negative lens and a positive lens. The difference in the refractive index and the Abbe number between the negative lens and the positive lens in each of the joined lenses and the partial dispersion ratio of the negative lens and the positive lens of the second joined lens are specified. Thus, a large angle of view and a long back focal length can be achieved while satisfying distortion aberrations, telecentric properties and magnification chromatic aberrations.

Abstract: An eyepiece lens for a display image observation device is disclosed that has only six lens elements with refractive power, in the order from the eye side, as follows: a first lens group G1 formed of two lens elements L1 and L2, both of positive refractive power, with the lens element L1 on the eye side being of positive meniscus shape with its convex surface on the eye side; a second lens group G2 formed of two lens elements L3 and L4 which are either separated by air or cemented together, the first of the lens elements on the eye side (i.e., L3) having negative refractive power and the other having positive refractive power; and a third lens group G3 formed of two lens elements which are either separated by air or cemented together, the first of the lens elements on the eye side (i.e., L5) having positive refractive power and the other having negative refractive power.

Abstract: A viewfinder optical system for conducting light from an object to an observer includes a plurality of reflecting surfaces having optical powers. Optical paths of each ray of a light flux reflected successively by the plurality of reflecting surfaces intersect each other at least twice, and the light from the object forms an image at least twice when passing through the viewfinder optical system.

Abstract: A real-image finder optical system includes a positive objective optical system, an image-erecting optical system and an eyepiece optical system, in this order from the object. The image-erecting optical system includes a pattern display surface having a reflective pattern, and a half mirror surface, transmitting a portion of the light rays incident from the object, and again reflecting the light rays having been reflected from the pattern display surface. The real-image finder optical system forms a real image of the object formed through the objective optical system and a virtual image of a pattern on the pattern display surface formed by an optical system including the half mirror surface so that an operator can simultaneously view both the real image of the object and the virtual image of the pattern through the eyepiece optical system; and the real-image finder optical system satisfies the condition:0<d.sub.1 /f.sub.e .ltoreq.0.1 (1)wherein d.sub.

Abstract: An eyepiece optical system includes the first lens group constituted by a negative single meniscus lens element having a convex surface on the side of a user's eye, and the second lens group having positive power as a whole, in this order from the object, whereby an intermediate image formed by an objective optical system is positioned between the first lens group and the second lens group. The second lens group includes a positive single meniscus lens element having a convex surface on the side of a user's eye, and a cemented sub-lens group having positive power as a whole. The cemented sub-lens group includes a positive lens element and a negative lens element. Furthermore, the eyepiece optical system satisfies the following conditions:-15<f.sub.1 /f.sub.1 <-3.5 (1)-10<f.sub.1 /f.sub.2 <-3.0 (2)whereinf.sub.1 designates the focal length of the first lens group;f.sub.2 designates the focal length of the second lens group; andf.sub.e designates the focal length of the entire lens system.

Abstract: Wide-angle eyepiece lenses for a microscope are disclosed. A representative lens comprises, from the object side to the eye side, a first lens group with positive refractive power, a second lens group with a concave surface facing the object side and a surface (closest to the object side) contacting air, and a third lens group with positive refractive power and at least one surface contacting air. One or both of the surface of the second lens group closest to the object side and the air-contacting surface of the third lens group is aspherical.

Abstract: An eyepiece system comprising, in order from the object side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power, and configured to locate an intermediate image formed by an objective lens system between the first lens unit and the second lens unit: the first lens unit being a negative lens unit having an object side surface which is convex toward the object side. This eyepiece system has a wide visual field and a long eye relief, and corrects aberrations favorably even at marginal portions of the visual field.

Abstract: A wide-field eyepiece, formed of at least four lens groups and five lens elements, is disclosed which satisfies predetermined conditional expressions, so as to provide an eyepiece having an angle of view of at least 65 degrees with less than 6% distortion. The wide-field eyepiece is formed of, in order from the side of an image position 1 formed by an objective lens (not illustrated): a first lens group G.sub.1 of negative refractive power that includes a first lens element L.sub.1 having a concave surface on both sides, a second lens group G.sub.2 of positive refractive power that includes a second lens element L.sub.2 having a convex surface on the side of an observer's eye position, a third lens group G.sub.3 of positive refractive power wherein a lens element surface thereof has a convex surface on both sides and is cemented to a negative lens element having a concave surface on the side nearest the image 1 formed by the objective lens; and a fourth lens group G.sub.

Abstract: An eyepiece system includes a first meniscus lens of positive power having a convex surface located on the object side and a cemented lens element composing of a second and a third lens element of positive power. The eyepiece system satisfies the conditions: (1) 0.2<f.sub.e /f.sub.1 <0.65 and (2) 0.6<f.sub.e /f.sub.23 <1.0, wherein f.sub.1 represents the focal length of the first lens element, f.sub.e represents the focal length of the entire system, and f.sub.23 represents the resultant focal length of the second and third lens elements.

Abstract: An observation optical system whose eye relief is below 25 mm includes an eyepiece lens having a water absorptive antifogging coating applied on one surface thereof, and a member holding the eyepiece lens. Further, an eyeball-characteristic detecting system includes a light source for illuminating the eyeball of an observer, a light receiving element arranged on detection of the reflected light from the eyeball through the eyepiece to produce a signal, an optical member positioned in the path of the light from the light source to the light receiving element and having an antifogging coating on one surface thereof, and a circuit receptive of the signal for detecting the characteristic of the eyeball.

Abstract: A viewfinder optical system has a relay lens system. The relay lens system focuses a primary image to form a secondary image. The relay lens is provided at an optical conjugate point with respect to a pupil. A surface of the relay lens system has an optical power of diffraction. The surface is positioned between the primary image and the optical conjugate point. The surface also has optical power of refraction.

Abstract: An eyepiece including a positive first lens element, a negative second lens element, a positive third lens element and a positive fourth lens element is provided. The first, second, third, and fourth lens elements are spaced from one another and arranged in this order from an object side. At least one of the four lens elements is a plastic lens with at least one aspherical surface satisfying the relationships defined by;d.sup.2 x/dh.sup.2 .ltoreq.{c/(1-0.sub.+ 5c.sup.2 h.sup.2).sup.3/2 }: when c >0; andd.sup.2 x/dh.sup.2 .gtoreq.{(c/1-0.sub.+ 5c.sup.2 h.sup.2).sup.3/2 }): when c<0;wherein"c" represents paraxial curvature;"x" represents sag amount; and,"h" represents a height from an optical axis.

Abstract: An eyepiece lens is disclosed, in which the total number of constituent lenses is reduced but good optical performance is obtained by setting forth proper rules of design for optical parameters.

Abstract: A telescope eyepiece comprising a series of single-element lenses in a combination that cancels chromatism. A negative field lens produces chromatism that is partly cancelled by an intermediate positive lens. The resulting red and blue focal points behind the intermediate lens are exactly matched by the same focal points for parallel rays assumed to originate from behind the eye lens passing forward, thus creating an achromatic system that cancels the remaining chromatism. An additional one or two intermediate positive lenses may be added to increase the field of view and reduce the curvature of field. The eyepiece designer can set the distortion of the system to zero, or can adjust it in a range from minor pincushion to minor barrel distortion as desired. Spherical aberration is corrected by the selection of curves for the field lens. Astigmatism is corrected by the spacing of the field lens from the next intermediate lens.

Abstract: An optical system for a view finder reduced in the overall length without aggravation of the optical performance has a negative power object lens and a positive power eyepiece lens each of which has an asphrical surface at at least one side respectively. The negative power object lens having a concave object side lens surface is comprised of a rectangular-shaped solid lens base with its four corners cut away along periphery of the concave lens surface.

Abstract: An ocular optical system for a viewfinder in a camera for observing object image which is formed on focusing glass or its vicinity via eye point. The ocular optical system includes, in order from the focusing glass side, a negative meniscus lens, which has its convex surface facing the focusing glass side, and a positive lens. Visibility compensation is performed by moving the positive lens along the optical axis without moving the negative meniscus lens.

Abstract: A viewfinder optical system has a relay lens system and an eyepiece optical system. The relay lens system refocuses a primary image as a secondary image. The relay lens system consists of a single lens element which has a surface having optical power of diffraction. The eyepiece optical system magnifies the secondary image and has a surface having optical power of diffraction.

Abstract: An eyepiece lens is disclosed, in which the total number of constituent lenses is reduced but good optical performance is obtained by setting forth proper rules of design for optical parameters.

Abstract: An eyepiece system comprising, in order from the object side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power, and configured to locate an intermediate image formed by an objective lens system between the first lens unit and the second lens unit: the first lens unit being a negative lens unit having an object side surface which is convex toward the object side. This eyepiece system has a wide visual field and a long eye relief, and corrects aberrations favorably even at marginal portions of the visual field.

Abstract: A magnifier lens comprises three lens elements. More specifically, from a front, eye side to a rear, object side there are a front positive lens element, a middle, negative power lens element and a rear, meniscus lens element. The front, positive power lens element has at least one aspheric surface. The front and the middle lens elements, in combination, contain at least one diffractive surface. The rear, meniscus lens element has front and rear refractive surfaces, both of which are concave toward the object side. The rear surface is positioned within 5 mm of an object to be viewed from the eye side. This rear surface is an aspheric surface of negative power that corrects field curvature.

Abstract: An eyepiece includes a biconvex lens, a bonded negative meniscus lens including a negative lens with a concave surface which faces the object, and a positive lens having a convex surface which faces an eyepoint. A biconvex lens and a positive lens having a convex surface which faces the object are also provided. Certain prescribed conditional equations are met by the eyepiece.

Abstract: An eyepiece system which is configured for observing an image formed by an objective lens system and comprises, in order from a side, of the objective lens system, a first lens element having at least one aspherical surface and a concave surface on the side of the objective lens system, at least one biconcave lens element and at least one positive lens element.

Abstract: An optical eyepiece assembly for providing a sixty degree field of view cbility to an image intensifier. The assembly includes first and second air-spaced lens doublets, a first lens, filter element, and second lens.

Abstract: An improved eyepiece for an optical system. In general, the inventive eyepiece (10) includes a refractive element (16) and an optical arrangement for relaying the entrance pupil of the system to the refractive element. In a specific implementation, the optical arrangement includes a concave primary mirror (12) and a secondary mirror (14). The mirrors are mounted to communicate an image from the refractive element (16) to the entrance pupil (40). In the specific implementation, the refractive element (16) is one or more refractive lenses. The use of a reflective optical arrangement allows for the long eye relief. The placement of the entrance pupil close to the pupil of the lens allows for the use of a compact optical arrangement with high ratio of eye relief to effective focal length with a compact optical arrangement. The system affords minimal lateral chromatic aberration and good image quality.

Abstract: An eyepiece with a wide field of view is made up of only a few spherical lenses, has a wide viewing angle, and includes eye relief of extensive length. The intrinsic aberration and the aberration of the pupil are favorably corrected. The eyepiece includes, in order from an object side, a positive meniscus lens having a convex surface which faces an eyepoint, a bonded biconvex lens made up of a biconvex lens and a negative meniscus lens with a concave surface facing the object side, and a positive lens with a convex surface which faces the object side. The bonded surface of the bonded biconvex lens has negative refractivity. The positive lens with the convex surface facing the object side is either a plano-convex lens with a planar side facing the eyepoint side or a positive meniscus lens with a concave surface facing the eyepoint side. Certain prescribed conditional equations are satisfied.

Abstract: A compact eyepiece is disclosed for use with an objective lens in a microscope, binocular, telescope, etc., that favorably corrects optical aberrations over a sufficiently wide apparent field of view and that offers an eye relief that is larger than the focal length of the eyepiece. The eyepiece comprises, in order from the objective side, a negative first lens group G1 and a positive second lens group G2. The second lens group has an objective-side focal plane situated between the first lens group G1 and the second lens group G2. The second lens group G2 comprises, in order from the objective side, a first lens subgroup G21 having positive refractive power and comprising a positive lens element G21A and a positive cemented lens G21B, and a second lens subgroup G22 having positive refractive power and comprising a positive lens element. The eyepiece satisfies certain quantitative conditions.

Abstract: Eyepiece lenses of wide visual field, one of which has a field angle of 75.degree. or wider, and another one of which has a field angle of 60.degree. with a smaller number of constituent lenses than the former has. One of these eyepiece lenses comprises, in the order from the light incidence side, a first lens unit of negative refractive power, a second lens unit of positive refractive power in the meniscus form concave toward the light incidence side, a third lens unit of meniscus form concave toward the light incidence side, a fourth lens unit of positive refractive power, and a fifth lens unit of positive refractive power in the meniscus form convex toward the light incidence side. A middle image plane lies within the second lens unit, or in a space between the second and third lens units.

Abstract: An eyepiece lens is disclosed that corrects aberrations over a wide apparent field of view, and has a short overall length and sufficiently long eye relief (typically at least 150% of overall focal length F). The eyepiece lens comprises, in order from the objective lens side, first and second lens groups having negative and positive refractive power, respectively, with a field stop situated therebetween. The first lens group comprises a cemented negative lens including two lens elements cemented together. The second lens group comprises, in order from the objective lens side, a positive meniscus lens element having a concave surface oriented objectivewise; a cemented lens comprising two lens elements cemented together and in which the most objectivewise lens surface is a concave surface oriented objectivewise; and a lens subgroup having positive refractive power and comprising a positive meniscus lens element having a concave surface oriented eyewise. The eyepiece lens satisfies at least the conditions: -4.5.

Abstract: There is provided an objective lens for focusing a subject light to form a real image on a predetermined focal plane, an eyepiece through which the real image is observed, and the first and second prism assemblies between the objective lens and the eyepiece for erecting an inverted image. The first and second prism assemblies are arranged at a predetermined distance away from each other such that the exit surface of the first prism assembly and the incident surface of the second prism assembly face each other across the focal plane. As a result, the dust on the whole surface of the prism assemblies and the like are made inconspicuous. Moreover, a visual field frame is provided on the focal plane, so that the visual field frame can be prevented from becoming out of focus and the border of the visual field can be seen clearly. Furthermore, a virtual image of a mark such as a target mark is formed in the Albada method.

Abstract: Eyepiece lenses are disclosed that provide a wide apparent field of view (.gtoreq.40.degree.) and that effectively correct optical aberrations even to the periphery of the apparent field of view. The eyepiece lens comprises, in order from the eye side, a first lens group G.sub.1 comprising a positive lens element, a second lens group G.sub.2 having positive refractive power and comprising either a positive lens element cemented to a negative lens element, or a negative lens element cemented to a positive lens element, and a third lens group G.sub.3 having positive or negative refractive power and comprising a positive lens element cemented to a negative lens element. At least one lens surface is aspherical. The eyepiece lens satisfies any of various quantitative expressions.

Abstract: A super wide-angle variable magnification viewfinder includes an objective lens group of a positive refractive power. The objective lens group further includes a fixed first lens unit of a negative refractive power, a movable second lens unit of a negative refractive power for compensating the change of a view angle, a movable third lens unit of a positive refractive power for changing the magnification of the optical system, and a fixed fourth lens unit of a positive refractive power. Also included in the finder is a prism for erecting an image and an eyepiece lens group of a positive refractive power. The objective lens group forms an actual image of an object, and the actual image can be observed through the eyepiece lens group. The view finder satisfies the condition:1.75<L.sub.t /f.sub.T <1.87where f.sub.T is the focal length of the objective lens group at the telephoto position, and L.sub.t is the distance from a first lens surface of the objective lens group to a focus.

Abstract: Eyepiece lenses of wide visual field, one of which has a field angle of 75.degree. or wider, and another one of which has a field angle of 60.degree. with a smaller number of constituent lenses than the former has. One of these eyepiece lenses comprises, in the order from the light incidence side, a first lens unit of negative refractive power, a second lens unit of positive refractive power in the meniscus form concave toward the light incidence side, a third lens unit of meniscus form concave toward the light incidence side, a fourth lens unit of positive refractive power, and a fifth lens unit of positive refractive power in the meniscus form convex toward the light incidence side. A middle image plane lies within the second lens unit, or in a space between the second and third lens units.

Abstract: An optical system for a compound camera includes an equivalent image plane provided at a position substantially optically equivalent to an image plane of the photographing lens system. A condenser lens is provided proximate to the equivalent image plane and a relay lens system is provided behind the condenser lens to form an image of the photographing lens system on an image pickup device. The relay lens system satisfies the requirements defined by -0.1<P<0.09, and S3<0, where P designates the Petzval sum of the whole relay lens system when the focal length of the relay lens system is assumed to be 1.0, and S3 designates the astigmatism coefficient of the whole relay lens system when the focal length thereof is assumed to be 1.0, respectively.

Abstract: In an eyepiece zoom lens having a lens configuration constituted by seven lenses in three groups, predetermined conditional expressions are satisfied so as to realize a zoom ratio of 3 while attaining a sufficient eye relief and ameliorating various kinds of aberration. The first lens group G.sub.1 is made stationary, whereas the second lens group G.sub.2 and the third lens group G.sub.3 are made as movable groups which, when changing the power, respectively move in directions opposite to each other on the optical axis while holding therebetween an object image which is formed between these two lens groups. Further, the eyepiece zoom lens is configured so as to satisfy the following conditional expressions:5<f.sub.1 /f.sub.m <7, 3.5<f.sub.2 /f.sub.m <4.5,-3.7<f.sub.3 /f.sub.m <-3, 0.1<S.sub.12 /f.sub.m <1.0, 6.0<S.sub.23 /f.sub.m <8.0,.nu..sub.1 <35, .nu..sub.2 <35, .nu..sub.

Abstract: An eyepiece having an apparent field of view of 40.degree. or greater which is provided, in succession from the eye point side, with a first lens unit G1 having positive refractive power as a whole, and a second lens unit G2 having negative refractive power as a whole and having a cemented negative lens disposed with a virtual image formed by the eyepiece interposed between itself and the first lens unit G1, satisfies the following conditions:1.0<f1/f<2.0-5.0<f2/f<-2.51.5<D/f<3.0,where f1 is the focal length of the first lens unit G1, f2 is the focal length of the second lens unit G2, D is the principal plane distance between the first lens unit G1 and the second lens unit G2, and f is the focal length of the entire lens system.

Abstract: A binocular optical system has a pair of six lens optical systems. Each system includes one lens (12) defining an optical axis and the remaining lenses (14, 16, 18, 20, 22) centered on the axis. The lens systems (12, 14, 16, 18, 20, 22) collimate the energy passing through them onto an exit pupil (24) positioned a desired eye relief distance (30) away from the last lens (22).

Abstract: A super-wide field eyepiece comprises, in succession from the incidence side of light, a first lens unit including a meniscus lens having its convex surface facing the incidence side and having positive or negative weak refractive power as a whole, a second lens unit including at least one lens surface having negative refractive power and having positive refractive power as a whole, and a third lens unit including at least two positive lenses and having positive refractive power as a whole, and an intermediate image is formed between the first lens unit and the second lens unit.

Abstract: An aspherical eyepiece has a positive lens group and a correction plate positioned on the light incident side of the positive lens group and having an aspherical surface. The correction plate is positioned between the positive lens group and the front side focal plane of the positive lens group or in front of the front side focal plane of the positive lens group. Thus, although the eyepiece is constructed by a reduced number of optical members including an aspherical optical member, distortion can be favorably corrected even with a wide field angle.

Abstract: An apparatus and method for aligning the optical elements of a microscope are disclosed wherein a fixture is provided for locating and mounting a plurality of mirrors for reflecting an object image along an optical path to an adjacent eyepiece connected to the fixture by an eyepiece holder. The eyepiece holder includes an outer sleeve attachable to the fixture, an inner sleeve transversely movable within the outer sleeve for slidably receiving the eyepiece, and positioning means comprising a plurality of angularly spaced screws extending through the outer sleeve for engaging the inner sleeve, whereby the eyepiece may be aligned on the optical path by selectively adjusting the screws.

Abstract: A wide field eyepiece lens system composed, in order from a side of an objective lens system, of a first lens unit which is composed of a plurality of lens elements and has a diverging function, and a second lens unit which is composed of a plurality of lens elements and has a converging function. The eyepiece lens system has an apparent field angle of 75.degree. to 80.degree., an eye relief of 0.95 f or longer and aberrations favorably corrected over an entire range of a visual field thereof including marginal portions, and is configured so as to satisfy the following conditions (1) and (2):-8.0<f.sub.1 /f<-4.8 (1)1.8<D/f<2.

Abstract: Binoculars designed to provide a large aided static field of view are provided. The binoculars are characterized by S/D ratios of above 2.8, where S is the binoculars' aided static field of view calculated by multiplying the binoculars' magnifying power by the binoculars' semi field of view in object space and D is given by tan.sup.-1 [(R.sub.ex +1.5)/13], where R.sub.ex is the radius of the binoculars' exit pupil and where R.sub.ex and the constants 1.5 and 13 are measured in millimeters. As a result of the increased S/D ratio, the binoculars' of the invention minimize the sensation of tunnel vision which normally occurs when binoculars are used and reduce the user's apprehension of missing activities in his or her peripheral vision. In certain embodiments, a movable field lens unit is employed to provide variable power and a negative corrector lens unit is employed for aberration correction and to minimize the size of the binoculars. The binoculars are suitable for mass production and general consumer use.

Abstract: An objective lens assembly provides up to 60 degrees field of view for the NVIS image intensifier goggle. A first lens subassembly positioned on the focal axis faces a external view and substantially corrects pupil aberrations in an aperture stop located after the first subassembly. A second lens subassembly is then located after the aperature stop on the focal axis. Color and field aberration corrections is provided while maintaining substantially high quality focus by a third lens subassembly. A lens element after the third lens subassembly on the focal axis flattens the image plane over the intensifier image format such that there results a format of up to 25 mm with a photocathode resolution for up to a 60 degree field of view.

Abstract: A multiple lens element macrolens system operative as a single lens has a high light transmission value and a wide field of view of an object to be viewed. The macrolens system provides a long object working distance and an extended back focal distance to an image plane. An object group of lens elements is spaced by a substantial axial gap from an image group of lens elements. The gap and the working and back focal distances facilitate inclusion of various auxiliary components into an optical instrument which incorporates the macrolens system.

Abstract: A binocular includes an eye-piece tube, a first lens system associated with the eye-piece tube for providing a base magnification as seen through the eye-piece tube, and an eye-piece module having a second lens system therein which is interchangeably installed in the eye piece tube for changing the position of the first lens system to a position of a preset increase in magnification.

Abstract: A zoom finder of a real image type has an objective lens having positive refracting power and an eyepiece having positive refracting power. The objective lens is constructed by first, second, third and fourth lens groups sequentially arranged from an object side. The first lens group has positive refracting power. The second lens group has negative refracting power. The third lens group has positive refracting power. The fourth lens group has positive refracting power. The zoom finder is constructed such that a real image is focused and formed by the objective lens between the fourth lens group and the eyepiece and is observed through the eyepiece. A magnification of the zoom finder is increased by moving the second lens group from the object side to an eyepiece side. A change in diopter caused by this increase in magnification is corrected by moving the fourth lens group. In accordance with the above structure, an entire length of the zoom finder is short and is not changed in a zooming operation.

Abstract: A device for providing multiple optical ports on an optical gunsight with a minimum impact on eye relief and which preserves full viewing angle is provided. A housing which includes first and second hinged housing portions is clamped about the circumference of the gunsight. A lens assembly is supported by one of the housing portions having an optical axis in line with the gunsight optical axis. A front lens and aspheric optical distortion lens relay a gunsight image to the beamsplitter. The beamsplitter directs first and second images from a gunsight image along axes which are in line an perpendicular to the gunsight axes. The assembly also includes identical third and fourth lenses which produce images of the gunsight exit pupil along each of these axes.

Abstract: An endoscope includes a disposable probe and a non-disposable focusing ocular. The probe includes a transfer module assembly including one or more relay modules, and an objective element including a distal glass window, a molded plastic prism and three molded plastic lenses. Each of the relay modules contains an entry glass rod, an intermediate glass rod, and an exit rod, each having flat end surfaces and two identical molded plastic doublets. The elements of the ocular are all of glass and include an axially movable focusing doublet and two non-movable doublets. The disposable probe introduces certain aberrations into the image. The non-disposable focusing ocular corrects these aberrations. A single curved surface is formed on the distal glass window of the probe; all other curved optical surfaces of the disposable probe are formed on molded plastic members, thereby reducing the cost of the probe sufficiently to be cost-effective for single patient, disposable use.

Abstract: An albada finder comprising an objective lens group, which includes two negative lenses, and an eyepiece lens group, which includes two positive lenses, arranged in this order from the object side. A view frame is formed on the object side surface of the eyepiece lens group, and a half mirror is formed on the eye point side surface of the objective lens group. The finder satisfies the following condition:LD/lf.gtoreq.2 (1)wherein,LD is the lens full length (distance from the 1st surface to the 8th surface), andLf is the eye relief (distance from the 8th surface to an eye point).