Abstract: An optical system includes a diffractive optical element in which a phase given to incident light from an optical axis toward the peripheral part in the radial direction is not reversed in an effective area and an absolute value of optical power on the optical axis is made minimum. In the optical system, chromatic aberration of magnification of a high order is satisfactorily corrected and flare caused by additional diffraction light (unnecessary diffraction light) is suppressed to as minimum as possible while maintaining a high imaging performance up to peripheral part of a field angle.

Abstract: A wide-angle lens is disclosed having only three lens groups of negative, positive, and positive refractive power, in order from the object side, and having only six lens elements with refractive power. The first lens group is formed of a meniscus lens with its convex surface on the object side, the second lens group is formed of a biconvex lens, and the third lens group is formed of, in order from the object side, a biconcave lens element, a positive lens element having a convex surface on the image side, a positive lens element having a convex surface on the image side, and a positive lens element having a convex surface on the object side. A diaphragm is arranged between the second lens group and the third lens group. Furthermore, specified conditions are satisfied in order to provide a compact wide-angle lens that is well corrected for aberrations and has a sufficient back focal length to insert additional optical components.

Abstract: An image capture lens and an image capture apparatus in which various kinds of aberrations are corrected and optical performance suitable for capturing images is obtained. Successively from an object side provided are a first lens group including a negative meniscus lens, a second lens group including a positive lens directing its convex to the object side, a third lend group including a first cemented lens composed of a bi-convex positive lens and a bi-concave negative lens, the first cemented lens having positive refractive power and directing its concave to the object side, a fourth lens group including a second cemented lens composed of a bi-concave negative lens and a bi-convex positive lens, the second cemented lens having negative refractive power and directing its convex surface to an image side, a fifth lens group including a positive lens directing its convex to the image side and a sixth lens group including a negative lens directing its concave to the object side.

Abstract: An imaging lens is disclosed having two lens groups, both of positive refractive power, a diaphragm positioned between the lens groups, and five or fewer lens elements with no aspherical surfaces. The imaging lens provides a high resolution over a wide image angle. During focusing, only the position of the rear lens group is adjusted relative to the image surface, enabling a low-cost shutter mechanism to be employed as the diaphragm. The front lens group includes, in order from the object side, either a plano-concave or a biconcave lens element and, in addition, a biconvex lens element. The rear lens group includes, in order from the object side, a positive meniscus lens element with its convex surface on the image side, a negative meniscus lens element with its concave surface on the image side, and a biconvex lens element. By having the ratio of the focal length of the positive meniscus lens element of the rear lens group divided by the focal length of the imaging lens be greater than 1.4 and less than 4.

Abstract: Successively from an object side, a negative lens having a concave surface directed onto an image surface side, a positive meniscus lens having a convex surface directed onto the image surface side, a positive lens having a convex surface directed onto the image surface side, a negative lens having a concave surface directed onto the image surface side, and a biconvex lens are disposed, thereby yielding a photographic lens for electronic still camera which can favorably correct distortion while attaining a compact size and a wide angle of view. Successively disposed from the object side are a negative first lens L.sub.1 having a concave surface directed onto the image surface side, a second lens L.sub.2 made of a positive meniscus lens having a convex surface directed onto the image surface side, a third lens L.sub.3 made of a biconvex lens whose surface with a stronger curvature is directed onto the image surface side, a negative fourth lens L.sub.

Abstract: The invention provides an inexpensive wide-angle lens system which is well corrected for longitudinal chromatic aberration and chromatic aberration of magnification without recourse to any anomalous dispersion glass while a long enough back focus is fully ensured. The wide-angle lens system comprises a front lens group comprising at least one positive lens and having negative power as a whole, an aperture stop 10, and a rear lens group comprising at least one negative lens and a diffractive optical element 11 having a diffractive surface of positive power, and having positive power as a whole, and satisfies 0.005<f/f.sub.DOE <0.03 where f is a focal length of the wide-angle lens system and f.sub.DOE is a focal length of the diffractive surface provided that f.sub.DOE is free of power of a substrate.

Abstract: This invention relates to a compact wide-angle lens which consists of five members. The first member and the last member are each divergent lenses of low deviation, which consist of low refractivity crown glass. The second member and the third member are convergent lenses made of high refractivity crown glass. The fourth member, which is the final member of the lens according to the invention, consists of a convergent lens and a divergent lens which are cemented to each other. Type of glass are used for this cemented member which have a very low difference in refractive index but a very high difference in dispersion. The convergent lens has a low dispersion and the divergent lens has a high dispersion. One of the two glass/air surfaces of the cemented member is aspherical. A lens such as this according to the invention has a maximum aperture ratio of at least 1:5.6 and an image angle of 105.degree.. The chromatic correction is well defined and is very substantially independent of the distance of the object.

Abstract: A first lens group having a four-lens configuration of positive, negative, negative, and positive lenses and a second lens group comprising at least two lenses are disposed successively from the object side, while these lenses are made of at least two kinds of glass materials having a difference in dispersion therebetween smaller than 0.0055, thereby yielding an imaging lens with a high brightness and a wide field angle which can favorably correct various kinds of aberration. From the object side, the first lens group, in which a positive first lens L1, a negative second lens L2, a negative third lens L3, and a positive fourth lens L4 are successively arranged, and the second lens group comprising three lenses L5, L6, and L7 are disposed. The difference in dispersion between the materials forming the lenses L1 to L7 is made smaller than 0.0055, while the lenses are configured so as to satisfy the following conditional expressions:-0.2<F/F1<1.0, -0.1<F/F2<1.4, 0.8<F/fa<2.0,0.5<.vertline.

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 objective lens device comprising in order from the lens closest to an object side, a negative meniscus first lens whose concave side faces the object side; a positive second lens; a positive meniscus third lens whose convex side faces an image side; a negative meniscus fourth lens whose concave side faces the object side; a negative meniscus fifth lens whose convex side faces the object side; and a positive sixth lens. The fifth and sixth lenses are cemented together to form a cemented lens subunit. The objective lens device contains six lenses in its entire lens structure, has a long back focus, and provides excellent optical properties over an entire field.

Abstract: A wide angle lens system comprises a front lens group and a rear lens group having positive refractive power. The front lens group includes in the order from the object side, a negative meniscus lens component having a convex surface facing the object side, a cemented lens component having a negative lens element and a positive lens element and a convex cemented surface facing the object side. The rear lens group includes a cemented lens component having a positive lens element and a negative lens element and a convex surface facing the object side. The rear lens group is moved toward the object side for focusing operation from the infinite object distance to the shortest object distance.

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 projection lens system for projecting an enlarged image onto a display screen front an image appearing on a faceplate of a cathode ray tube utilizes at least six lens groups. The first lens group, from an end closest to the display screen, is in a form of a meniscus having a negative power. The second lens group has a weak positive power and a convex surface towards the display screen. The third lens group has a strong positive power. The fourth lens group is bi-convex and has a strong positive power. The fifth lens group has a weak positive power. The sixth lens group has a negative power and a pronounced concave surface away from the display screen. The second and fifth lens groups each are made with plastic lenses with at least aspheric surfaces on one side.

Abstract: An objective lens is corrected for spherical aberration at both an operating wavelength and a measurement wavelength, such that the amount of spherical aberration to develop at the operating wavelength is substantially equal to the amount of spherical aberration to develop at a measuring wavelength. The method of lens performance measurement then uses a light source emitting at a wavelength different from the operating wavelength.

Abstract: A zoom lens system, for use in a copying apparatus, is provided with, from the object side, a first lens unit of a negative power including a negative lens element, a second lens unit of a positive power including a positive lens element and a negative meniscus lens element concave to the image side, an aperture stop, a third lens unit arranged symmetrically with the second lens unit with respect to the aperture stop, and a fourth lens unit arranged symmetrically with the first lens unit with respect to the aperture stop. The second lens unit and the fourth lens unit are moved in a same direction in association with each other so that the total length of the zoom lens system is minimum at unity magnification. The aperture stop moves so that the symmetry of the entire zoom lens system is maintained. An object-image distance is maintained constant by moving the entire zoom lens system.

Abstract: The invention provides an ultra-wide field eyepiece for microscopes, in which such off-axial aberrations as the curvature of field, astigmatism and coma are well-enough corrected at a field number as large, as 26.5, and in which the flatness of the image surface is degraded even when the entrance pupil position varies, and which comprises, in order from the entrance side, a first lens unit G1 of negative refracting power, a second lens unit G2 of positive refracting power, a third lens unit G3 of negative refracting power, a fourth lens unit G4 of positive refracting power and a fifth lens unit G5 of positive refracting power with the surface having a stronger curvature facing the entrance side, said third to fifth lens units being located in the rear of an intermediate image plane.

Abstract: A lens system operable with two or three colors comprises a front lens system disposed on the object side relative to a stop and a rear lens system disposed on the image side relative to the stop. The front lens system includes first to third lens groups, while the rear lens system includes fourth to sixth lens groups. Each of the front and rear lens systems includes two meniscus lenses. The meniscus lenses have a concave surface and a negative power. Accordingly, average image points with respect to two or three wavelengths substantially coincide with each other, while the image fields coincide with each other within the range from the vicinity of the optical axis to image peripheral portion.

Abstract: A diffraction limited, f/6.0, 71.0 mm focal length telecentric scan lens which is color-corrected for 780 nm, 830 nm and 890 nm wavelengths. The lens includes, in succession from a side of incident light:a first negative meniscus lens element, concave toward the incident light side;a second positive meniscus lens element, concave toward the incident light side;a first plano-convex lens element, convex away from the incident light side;a second plano-convex lens element, convex toward the incident light side;a first cemented doublet including bi-concave and plano-convex lens elements, the cemented surface convex toward the incident light side; anda second cemented doublet including plano-concave and plano-convex lens elements, the cemented surface convex toward the incident light side.