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 lens system has, from the pupil side and proceeding toward the object side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. At least one of the first lens unit and the second lens unit has at least one aspherical surface, and the eyepiece lens system fulfills the following condition: ##EQU1## where, f represents a focal length of the entire eyepiece lens system;d.sub.0 represents an eye-relief;.phi..sub.1 represents a refractive power of the first lens unit;.phi..sub.2 represents a refractive power of the second lens unit;r.sub.1 represents a radius of curvature of a pupil side surface of the first lens unit;r.sub.3 represents a radius of curvature of a pupil side surface of the second lens unit; andr.sub.5 represents a radius of curvature of a pupil side surface of the third lens unit.

Abstract: The present invention allows one to take an intermediate image formed by a microscope objective lens system and reform a clear image of it, at relatively low magnification, on a film surface. The present invention provides for a lens system which comprises, in order, from the observed object end, a first lens group having a convex surface facing toward the objective lens system end, and having positive refractive power, a second lens group, positioned to the rear of the intermediate image, and having negative refractive power, and a third lens group having positive refractive power. The lenses in the system are set to follow predetermined parameters.

Abstract: An optical system comprising three lenses concentrically housed in a frame is aligned with a screen on which a televisual image of a virtual reality application is displayed. The compact and high power lenses permit the eye of a viewer when placed at eye position to have a wide field of view of the magnified virtual image of the screen. To train the eye of the user along the optical axis of the system the lenses vignette the image on the screen when the eye is not closely aligned with the axis. By plastics moulding one or more of the lenses so that they are of truncated form it is possible for injection points of the mould to be adjacent truncated side faces thereby permitting a balanced generally free flow of material through the mould cavity which results in minimal optical stresses in the finished lens.

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: An eyepiece system includes a single positive lens and a cemented lens assembly having a positive biconvex lens and a negative lens cemented thereto, in this order from the object side. The eyepiece satisfies the relationships defined by d<0.3f, and f.sub.1 >1.5f, wherein "d" represents a distance between the single positive lens and the cemented lens assembly, "f" a focal length of the whole lens system, and "f.sub.1 " a focal length of the single positive lens.

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: A zoom lens system is composed of three lens groups. Arranged in the order from an eyepoint side are a first lens group G.sub.1 having a positive refracting power, a second lens group G.sub.2 having a positive refracting power and movable along an optical axis during the period of zooming, and a third lens group G.sub.3 having a negative refracting power and movable along the optical axis during the period of zooming. In the second lens group G.sub.2, at least one positive lens includes a lens surface composed of an aspheric surface at least on one of its eyepoint side and object side. Not only a sufficient eye relief is ensured but also various aberrations are corrected throughout the whole zooming range.

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: An eyepiece lens comprising, from front to rear, a first lens unit of positive refractive power having a negative lens and a positive lens, a second lens unit of positive refractive power and a third lens unit of positive refractive power, wherein at least one of the lens surfaces in the first lens unit to the third lens unit is made aspherical, and wherein the apparent field of view covers an angle of about 50 degrees, the eye relief is elongated, and the field curvature is corrected well.

Abstract: A reverse Galilean finder in which a front frame, preferably associated with a front element is projected away from the eye by the finder optics without separate frame projection optics to a position such that the distance between the apparent position of the frame to the eye and the rear vertex of the finder divided by the length of the finder is at least 2.2.

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 visual angle of 40.degree. or greater is provided, in succession from the eyepoint side, with a first lens unit G1 having positive refractive power, a second lens unit G2 having positive refractive power, and a third lens unit G3 having positive refractive power. The first lens unit G1 has a positive lens component, the second lens unit G2 has a positive lens component, and the third lens unit G3 has a cemented lens consisting of a positive lens component and a negative lens component. At least one of the lens surfaces of the first to third lens units G1 to G3 is formed into an aspherical shape.

Abstract: An ocular lens includes, sequentially from an object side, a first lens unit G1 exhibiting a negative refracting power on the whole and a second lens unit G2 exhibiting a positive refracting power on the whole. An object-side focal surface of the second lens unit G2 is positioned between the first and second lens units G1, G2. At least one lens surface of the first lens unit G1 is formed in an aspherical shape.

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: A re-imaging objective optical system provides superior optical performance while having a short overall length and a relatively simple composition. The system has, in order from the object side of the optical system, a front lens group (G1) composed of a first lens group having a positive lens component (L1), a second lens group having a biconcave negative lens component (L2) and a third lens group having a positive lens component (L3); and a back lens group G2 composed of a cemented double lens element with components (L4 and L5) and a positive lens component (L6). The spatial or primary image I.sub.1 from the objective optical system is formed on the optical path between the first lens group and the second lens group.

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: A high eye point type viewfinder optical system comprising an eyepiece lens system for observing an image of an object formed on a reticle, and a pentagonal prism and a condenser lens which are disposed between the reticle and the eyepiece lens system in order from the eyepiece lens system; wherein the eyepiece lens system consists, in order from the side of an eye of a photographer, of a first negative lens component, a second positive lens component and a third lens component. This viewfinder optical system is configured so as to permit adjustment of diopter by moving the second and third lens components along an optical axis with the first lens component kept fixed or moving the second lens component along the optical axis with the first and third lens components kept fixed.

Abstract: Eyepiece optical systems having arrangements of surfaces where light is refracted or diffracted provide eyepieces with fewer elements and more compact designs than comparable, conventional eyepiece designs. These eyepiece optical systems have three elements each with positive focussing power, and provide a wide field-of-view of about 70.degree. and an eye relief of approximately 80% of the total focal length of the eyepiece. One embodiment has (from the eye side) a refracting, meniscus, positive element with a surface concave toward the eye, a bi-convex element having a refracting convex surface and a second refracting convex surface, and a refractive/diffractive doublet element with a refracting convex surface and diffracting surface (each element being of positive power).

Abstract: The invention relates to an eyepiece that has an improved image surface flatness even at a wider field angle, is well corrected for various aberrations inclusive chromatic aberration of pupil and is usable with inexpensive microscopes (esp., stereoscopic ones). The eyepiece of the invention is an eyepiece including at least three lens components comprising a cemented lens component consisting positive and negative lens elements and a lens component having a negative refractive power in its entirety, characterized in that the lens component other than the lens components proximate to the object and eye sides is provided with a plastic lens element or elements having at least one aspherical surface.

Abstract: An objective optical system for endoscopes comprising, in the order from the object side, a front negative lens unit, an aperture stop, a positive lens unit comprising at least one positive lens component, and an infrared cut filter arranged immediately before said aperture stop, said objective optical system being adapted so as to allow rays to be incident on said filter at heights lower than the outside circumference of said filter.

Abstract: An ocular system is disclosed which is composed of at least three lens elements for constituting, in order from the eye side, at least first and second lens units. At least one of the lens elements is made of resin. Two of the lens elements are substantially cemented together. In addition, an aspherical plastic lens is effectively used in the system.