Abstract: An image forming lens system is provided which has at least three lens groups, wherein diameters of outer most circumferences of all of the lens groups are identical, and wherein positions of at least two of the lens groups in an optical axis direction is determined by direct contact of the two lens groups.

Abstract: An achromatic lens system includes in order, from the object side, a front lens group, a chromatic aberration correcting lens group, and a rear lens group. Aberrations, including spherical aberration, coma, astigmatism, curvature of image, as well as axial chromatic aberration of wavelengths from green to red, are substantially corrected by the front lens group and the rear lens group. The axial chromatic aberration of the wavelength blue, caused by the front lens group and the rear lens group, is corrected by the chromatic aberration correcting lens group.

Abstract: A wide-angle photographic lens system comprising a front lens unit having a positive refractive power, an aperture stop and a rear lens unit having a positive refractive power or a negative refractive power; the front lens unit comprising at least one positive lens component and at least one negative lens component, whereas said rear lens unit consisting of a positive lens component having a convex surface on the image side. This photographic lens system has a short total length (a length as measured from a first surface to an image side surface of the lens system and a small value of .SIGMA.d (a distance as measured from the first surface to a final surface thereof), and is suited for use with collapsible mount type cameras.

Abstract: A microscope objective lens, sequentially from an object-side, comprises a first lens group constructed of a positive lens element, a second lens group constructed of a negative lens element, and a third lens group constructed of cemented lens elements consisting of a negative lens element and a positive lens element and exhibiting a positive refracting power on the whole. Further, the microscope objective lens system satisfies the following conditions:1.5<f/f.sub.1 <1.9-3.8<f/f.sub.2 <3.12.0<f/f.sub.3 <2.70.9<(d.sub.2 +d.sub.3 +d.sub.4 +d.sub.5)/f.sub.1 <1.215<n.sub.1 .multidot.f/d.sub.150<n.sub.2 .multidot.f/d.sub.3wheref : the focal length of the whole system,f.sub.1 : the focal length of the first lens group,f.sub.2 : the focal length of the second lens group,f.sub.3 : the focal length of the third lens group,d.sub.1 : the central thickness of the positive lens element in the first lens group,d.sub.

Abstract: An image pickup optical system having an image pickup lens system having in turn a plurality of lenses arranged in multiple stages for forming an image of an object on an image plane of an image pickup device is disclosed. The image pickup optical system includes a double refraction plate arranged downstream of the image pickup lens system, a diaphragm unit, as a first optical unit, for determining the F-number of the image pickup lens system by a diaphragm aperture, and a second optical unit. When the F-number is equal to a pre-set value Fd or less, the second optical unit operates in conjunction with the double refraction plate for lowering the modulation transfer function (MTF) by the aberration due to an aspherical surface for a range of the spatial frequency not less than the cut-off frequency r.sub.c. Sufficient spurious signal suppressive effects may be obtained even if the optical low-pass filter is constituted by a sole double refraction plate, such as a quartz plate.

Abstract: A Fourier transform lens assembly suited for use in an optical information processor includes a first lens group having a positive power, a second lens group having a negative power disposed on one side of the first lens group, and a third lens group having a positive power disposed on the side opposite to the first lens group with respect to the second lens group. The distance between a front focal plane and a back focal plane of the Fourier transform lens assembly is less than two times a focal length of the Fourier transform lens assembly.

Abstract: An objective for use in photographic compact cameras has a relative aperture of 3.5 and a focal length of 35 mm, and is of the triplet type. The lens element on the object side is a cemented element. In order to achieve an extremely compact structural shape and balanced monochromatic correction, as well as a reduction in the chromatic magnification difference, the color coma and the color astigmatism, four design conditions are specified.

Abstract: The invention provides a compact zoom lens system which has an angular coverage from wide angle to moderate telephoto and makes a relatively bright and parallax-free TTL finder possible and in which a first unit 11 having a positive power as a whole is located on the side proximate to the object. The lens system includes a reflective means 13c located more closely to the image side than the first unit 11 for guiding incident light to a finder subsystem and a movable lens unit that moves for zooming. The movable lens unit comprises a sub-unit 13a having a positive power as a whole and located on the object side of the reflective means 13c and a sub-unit 13b having a negative power as a whole and located on the images side of the reflective means 13c, or alternatively a sub-unit having a negative power as a whole and located on the object side of the reflective means and a sub-unit having a positive power as a whole and located on the image side of the reflective means.

Abstract: A lens system comprising, in order from the object side, a first lens component having a positive refractive power, a second lens component having a negative refractive power and a thrid lens component having a positive refractive power; the first lens component or the third lens component being a radial type graded refractive index lens component. The lens system is composed of the lens component in a number as small as three and has favorable optical performance.

Abstract: An imaging lens system is disclosed which comprises a focusing lens and a correcting lens which has aspherical surfaces on both side. Usually, the focusing lens if located on the object side but the correcting lens may be disposed on the object side.

Abstract: A three-lens objective has the following characteristics: A front lens consists of a first material of relatively low dispersion, a median lens consists of a second material of relatively larger dispersion, and a rear lens consists of a material of relatively low dispersion. The front lens has positive power, the median lens has negative power, and the rear lens has positive power. The spacing between front lens and median lens is substantially smaller than the distance between median lens and rear lens. Each of the lenses has at least one aspherical surface.

Abstract: A zoom lens comprises a first lens unit having a positive refractive power, a second lens group having a negative refractive power, an iris and a third lens unit having a positive refractive power, arranged in this sequence as viewed from an object. The third lens unit comprises a lens unit 3a and a lens unit 3b arranged in this sequence as viewed from the object, with a large air gap therebetween. Zooming from a short focal length end to a long focal length end is effected by moving the second lens group from a unit side to a image side and moving the first lens unit and the third lens unit to depict convex loci toward the object. The zoom lens meets the condition of-0.3<HF.sub.3 /f.sub.3 <0.20.5<l.sub.3 /f.sub.3 <1.5whereHF.sub.3 is a distance between an apex of a lens of the third lens group facing the object and a front principal point of the third lens unit,f.sub.3 is a focal length of the third lens unit, andl.sub.3 is an air gap between the lens unit 3a and the lens unit 3b.

Abstract: A three group, three component lens system comprising, in order from one side a first, positive meniscus lens defining a convex surface directed to an object, a second, biconcave lens, and a third, biconvex lens. At least one of the three lenses is formed of plastic. It is recommended to satisfy the following conditional expression:0.1 f<f1+f2<0.2fwhere f is a focal length of the entire lens system, f1 is a focal length of said first lens, and f2 is a focal length of said second lens.

Abstract: An imaging optical system has a first objective lens movable along the optical axis thereof for focus adjustment and for forming the image of an object at infinity, and a second objective lens for forming the image again at a predetermined position at a predetermined magnification. The second objective lens comprises, in succession from the object side, a positive single lens, a negative single lens and a positive single lens disposed with an air space therebetween, and satisfies the following conditions:0.05f<.SIGMA.d<0.14f0.1f<.vertline.r.sub.M .vertline.<0.35f0.01f<D<0.11fwhere f is the focal length of the second objective lens, .SIGMA.d is the assembly length of the second objective lens, r.sub.M is the radius of curvature of that surface of the lenses constituting the second objective lens which has the greatest positive power, and D is the total of the air spaces between the two positive single lenses and middle negative single lens of the second objective lens.

Abstract: An imaging lens system comprising, in the order from the object side, a first lens component having a convex surface on the object side and a positive refractive power, a second lens component having a concave surface on the image side and a negative refractive power, and a third lens component. Through the imaging lens system is of a triplet or Tessar type, the lens system is designed so as to have a high aperture ratio and favorably corrected coma by arranging a radial GRIN lens element having a concave surface on the image side and a positive refractive power at the most image side location in the third lens component.

Abstract: There is provided a behind stop wide angle lens system which comprises a positive lens L.sub.1 formed by joining a negative meniscus lens L.sub.11 whose convex surface faces an object and a positive meniscus lens L.sub.12 whose convex surface similarly faces the object, a biconcave negative lens L.sub.2, a biconvex positive lens L.sub.3 and an aperture stop S, disposed in this order from the side of the object. The behind stop wide angle camera achieves a wider angle of view and has an excellent imaging performance in spite of a simple structure and a compact size thereof.

Abstract: A photolithographic projection optical system comprising: a source of exposure energy for generating a beam of energy; an optical element located in the path of the beam for receiving the beam of energy and passing the beam therethrough; a refractive lens assembly located in the path of the portion of the beam for receiving and transmitting the beam of energy, the refractive lens assembly comprising at least one meniscus lens, a plano-convex lens, and an air gap disposed between the meniscus lens and the plano-convex lens; a reticle element located in the path of the portion of the beam, the reticle element having a uniform thickness and being positioned for permitting the beam to pass through the thickness and through the lens assembly to the optical element. Alternatively, the air gap of the refractive lens assembly can be replaced with a glass layer having an index of refraction that is lower than both the meniscus lens and the plano-convex lens.

Abstract: A copying lens system of a three-unit/three-element composition that can be made from relatively inexpensive optical materials and which exhibits satisfactory performance at copying ratios ranging from about 0.5 to 2.0. The lens system includes, in order from the object side, a first lens of positive meniscus having a convex surface directed to the object, a negative second lens having a concave surface on both sides, and a positive third lens having a convex surface on both sides. The lens system satisfies the following conditions:(1) 1.70<n.sub.1 +.nu..sub.1 /200.ltoreq.1.93(2) 0.10<n.sub.3 -n.sub.1(3) 0.06<d.sub.t /f.sub.t 0.11(4) 0.60<-r.sub.3 /r.sub.4 <1.05(5) 1.40<-r.sub.5 /r.sub.6 <2.70wheref.sub.t : the focal length of the overall system;n.sub.i : the refractive index of the ith lens at the d-line;.nu..sub.i : the Abbe number of the i.sup.th lens;r.sub.j : the radio of the curvature of the j.sup.th lens; andd.sub.t : the overall length of the system.

Abstract: In one embodiment, a three-element biocular eyepiece system 40 having a first optical element 42 with at least one diffractive surface 44, a second optical element 48 having a refracting convex surface 50 and a refracting concave surface b 52 is provided. A third optical element 54 having a refracting convex surface 56 and a refracting convex surface 58 is also employed. In another embodiment, a four-element biocular system 60 is disclosed as having an optical element 62 having a refracting concave surface 64 and a refracting convex surface 66, a refractive-diffractive hybrid optical element 68 having a diffractive surface 70 and a refracting convex surface 72, an optical element 74 having a refracting convex surface 76 and a refracting concave surface 78, and an optical element 80 having a refracting concave surface 82 and a refracting convex surface 84. The diffractive surfaces 44 and 70 have a kinoform profile 102 a-d or approximated kinoform profiles 112a-d and 122a-d.

Abstract: Disclosed is a lens system for a telescopic camera comprised of a primary lens, a secondary lens and a tertiary lens. The primary lens is a positive lens having a convex front surface and an aspheric back surface which define an optical axis. The secondary lens is a negative lens which has a concave front surface and a concave back. The front surface of the secondary lens is positioned at a predetermined fixed distance adjacent to the back surface of the primary lens and centered with respect to the optical axis. The tertiary lens is a field flattening lens having a convex front surface and a convex back surface. The front surface of the tertiary lens is positioned at a predetermined fixed distance adjacent to the back surface of the secondary lens, wherein the primary, secondary and tertiary lenses have surfaces shaped to focus on an object viewed such that a field of view of about 4.2.degree.