Abstract: An optical image capturing system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element. The first lens element with positive refractive power has a convex object-side surface. The second through seventh lens elements all have refractive power. The sixth lens element has an object-side surface and an image-side surface which are both aspheric. The seventh lens element has an object-side surface and an image-side surface which are both aspheric, its wherein the image-side surface of the seventh lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof.

Abstract: A wide angle lens whose field angle exceeds 160 degrees, includes a front group, an aperture stop, and a rear group arranged in this order from an object-side toward an image-side. The front group includes a first lens (negative meniscus) whose convex surface faces the object, a second lens (negative), a third lens (negative), and a fourth lens (positive), arranged in this order from the object-side toward the image-side. The rear group includes a fifth lens (positive), a sixth lens (negative), and a seventh lens (positive), arranged in this order from an aperture-side toward the image-side. The fifth and sixth lenses are combined, forming a cemented lens having positive refractive power. The fifth and sixth lenses are made of materials having Abbe numbers of greater than or equal to 50 and less than or equal to 30, respectively. A surface of the seventh lens facing the image is aspheric.

Abstract: A lens system comprises, on a side closest to an object, a first lens component having a positive refractive power and a second lens component having a positive refractive power in order from the object; and on a side closest to an image, a cemented lens constructed by cementing together a positive lens and a negative lens in order from the object; wherein the lens system satisfies the following conditional expressions: (n1+n2)/2>1.49 (?1+?2)/2>60 where n1 and ?1 denote a refractive index and an Abbe number of the first lens component at d-line, respectively, and n2 and ?2 denote a refractive index and an Abbe number of the second lens component at d-line, respectively.

Abstract: An optical image capturing system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element. The first lens element with positive refractive power has a convex object-side surface. The second through fifth lens elements all have refractive power. The fifth lens element has a convex image-side surface. The sixth lens element with positive refractive power has both of the object-side and image-side surfaces thereof being aspheric. The seventh lens element with negative refractive power has a concave image-side surface and both of the object-side and image-side surfaces thereof being aspheric. The image-side surface of the seventh lens element changes from concave at a paraxial region to convex at a peripheral region.

Abstract: A lens module includes a first lens group with a positive refractive power, a second lens group with a negative refractive power, and a third lens group with a positive refractive power. The first lens group essentially consists of a first lens with a negative refractive power, a second lens with a positive refractive power and a third lens with a positive refractive power arranged in order from a magnified side to a reduced side. The second lens group essentially consists of a fourth lens with a negative refractive power and a fifth lens with a positive refractive power arranged in order from the magnified side to the reduced side. The third lens group essentially consists of a sixth lens with a positive refractive power and a seventh lens with a positive refractive power arranged in order from the magnified side to the reduced side.

Abstract: A first lens unit performing communication with an image pickup apparatus with a first voltage and a second lens unit performing communication with the image pickup apparatus with a second voltage are selectively attached to the image pickup apparatus. The image pickup apparatus includes a controller configured to operate with a third voltage different from at least one of the first and second voltages to output a signal for the communication with the first and second lens units, and a determiner configured to determine the type of the lens unit attached to the image pickup apparatus. The controller is configured to produce, as a voltage of the signal for the communication, from the third voltage, one of the first and second voltages corresponding to a determination result of the determiner.

Abstract: An optical system includes a first lens unit, an aperture stop, and a second lens unit having a positive refractive power. The first lens unit includes a first lens having a negative refractive power and a second lens having a positive refractive power. The second lens unit includes a cemented lens, a fifth lens having a negative refractive power and a concave surface facing an object side, and a sixth lens having a positive refractive power and a convex surface facing an image side. In the cemented lens, a third lens having a positive refractive power and a fourth lens having a negative refractive power are cemented. A distance D1 from an object-side lens surface vertex of the first lens to the aperture stop and a distance Dt from the object-side lens surface vertex of the first lens to an image plane are appropriately set.

Abstract: An endoscope objective lens unit includes a front lens group and a rear lens group with a diaphragm interposed therebetween. The front lens group includes a first lens and a second lens, and the rear lens group includes a third lens, a fourth lens and a fifth lens. The endoscope objective lens unit satisfies following expressions (1A) to (4): (1A) ?3 <SF ?1; (2) ?3 <Fr/Ff <?1.1; (3) ?1.6 <Ff/f <?0.6; and (4) Ff/f1 <1.6, where SF is a shape factor, Ff is a focal length of the front lens group, Fr is a focal length of the rear lens group, f is a focal length of the entire unit, and f1 is a focal length of the first lens.

Abstract: A lens system comprises, on a side closest to an object, a first lens component having a positive refractive power and a second lens component having a positive refractive power in order from the object; and on a side closest to an image, a cemented lens constructed by cementing together a positive lens and a negative lens in order from the object; wherein the lens system satisfies the following conditional expressions: (n1+n2)/2>1.49 (?1+?2)/2>60 where n1 and ?1 denote a refractive index and an Abbe number of the first lens component at d-line, respectively, and n2 and ?2 denote a refractive index and an Abbe number of the second lens component at d-line, respectively.

Abstract: An optical lens system with a wide field of view comprises, in order from the object side to the image side: a first lens element with negative refractive power having a convex object-side surface and a concave image-side surface; a second lens element; a third lens element; a fourth lens element having a concave object-side surface and a convex image-side surface; a fifth lens element with positive refractive power; a sixth lens element with negative refractive power; a seventh lens element, one of an object-side surface and an image-side surface being aspheric. There are seven lens elements with refractive power. By adjusting the arrangement of curvature, refractive power of the respective lens elements and a stop, sufficient field of view can be obtained and the aberrations of the system can be corrected in order to obtain good image quality.

Abstract: An objective lens includes, in order from an object side, a front group having negative refractive power, an aperture stop, and a rear group having positive refractive power, wherein the front group includes, in order from the object side, a first lens which is a negative meniscus lens with a convex surface turned to the object side and a second lens which is a negative lens with a concave surface turned to the object side; the rear group includes, in order from the object side, a positive third lens and a fourth lens made up of a positive lens and a negative lens cemented together, and the objective lens satisfies conditional expression (1) below: ?0.8<f—F/f—R<?0.3 ??(1), where f_F is a focal length of the front group, and f_R is a focal length of the rear group.

Abstract: The invention relates to an reimaging optical system that has a sufficiently enhanced magnification and better performance, and an endoscope using the same. The reimaging optical system 3 is adapted to re-form an image by an image guide 6 on a solid-state imaging device 4 having a diagonal length of 6.5 mm or longer, and satisfies the following condition. 0.6<(D×|?|)/V??(1). Here D is the diameter of the image guide 6, ? is the optical transverse magnification of the reimaging optical system 3, and V in mm is the minor axis direction length of an imaging area of the solid-state imaging device 4.

Abstract: Disclosed is a fisheye lens comprised of the first through the seventh lens elements: wherein a field of view is larger than 180° a calibrated distortion is 10% or less, a relative illumination is 80% or more, all the refractive surfaces of the lens elements are spherical surfaces, the first lens element is a negative meniscus lens element having a convex surface facing an object side, the second lens element is a bi-concave lens element, the third lens element is a positive meniscus lens element having a convex surface facing an image side, a stop is located between the third and the fourth lens elements, the fourth lens element is a bi-convex lens element, the fifth lens element is a bi-concave lens element, the sixth and the seventh lens elements are bi-convex lens elements.

Abstract: A wide angle lens module includes a first lens and a second lens with negative refracting power, a third lens and a fourth lens with positive refracting power, a fifth lens with negative refracting power, a sixth lens with positive refracting power, and a seventh lens with negative refracting power. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are assembled in order from an object side to an image side.

Abstract: An optical system comprising two lens cells, each lens cell comprising multiple lens elements, to provide imaging over a very wide image distance and within a wide range of magnification by changing the distance between the two lens cells. An embodiment also provides scannable laser spectroscopic measurements within the field-of-view of the instrument.

Abstract: Disclosed is a fisheye lens comprised of the first through the seventh lens elements: wherein a field of view is larger than 180° a calibrated distortion is 10% or less, a relative illumination is 80% or more, all the refractive surfaces of the lens elements are spherical surfaces, the first lens element is a negative meniscus lens element having a convex surface facing an object side, the second lens element is a bi-concave lens element, the third lens element is a positive meniscus lens element having a convex surface facing an image side, a stop is located between the third and the fourth lens elements, the fourth lens element is a bi-convex lens element, the fifth lens element is a bi-concave lens element, the sixth and the seventh lens elements are bi-convex lens elements.

Abstract: A photographic lens system includes a positive lens element, a positive lens element, a negative lens element having a concave surface facing toward the image, a diaphragm, a negative lens element having a concave surface facing toward the object, a positive lens element which is cemented to the negative lens element, and two or three positive lens elements, in this order from the object. An intermediate negative lens element, having the weakest negative refractive power out of all of the negative lens elements, is provided between the negative lens element having the concave surface facing toward the image and the negative lens element having the concave surface facing toward the object.

Abstract: A wide angle lens module includes a first lens and a second lens with negative refracting power, a third lens and a fourth lens with positive refracting power, a fifth lens with negative refracting power, a sixth lens with positive refracting power, and a seventh lens with negative refracting power. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are disposed in order from an object side to an image side.

Abstract: An imaging lens of which optical performance does not deteriorate even in a high temperature environment, various aberrations are well corrected, optical length is short, and back focus is sufficiently secured. This imaging lens comprises a first diaphragm S1, a first junction type compound lens 14, a second diaphragm S2 and a second junction type compound lens 16, wherein the first diaphragm, the first junction type compound lens, the second diaphragm, and the second junction type compound lens are arranged in this sequence from an object side to an image side. The first junction type compound lens comprises a first lens L1, a second lens L2 and a third lens L3 arranged in this sequence from the object side to the image side, and the second junction type compound lens comprises a fourth lens L4, a fifth lens L5 and a sixth lens L6 in this sequence from the object side to the image side. The first lens, the third lens, the fourth lens and the sixth lens are formed of a curable resin material.

Abstract: A wide-angle lens module includes a first lens and a second lens with negative refracting power, a third lens with positive refracting power, a fourth lens with negative refracting power, a fifth lens with positive refracting power, a sixth lens with positive refracting power, and a seventh lens with negative refracting power. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are disposed in order from an object side to an image side.

Abstract: A small projection lens includes a first lens, which is a biconvex lens, an aperture, an aperture diaphragm (or an aperture), a second lens, which is a negative meniscus lens having a concave surface facing a magnification side, a third lens, which is a positive meniscus lens having a convex surface facing a reduction side, and a fourth lens, which is a biconvex lens having aspheric surfaces at both sides on an optical axis, arranged in this order from the magnification side. A minimum portion of the length of all lens elements of the small projection lens in a diametric direction vertical to the optical axis is equal to or less than 15 mm, and the small projection lens satisfies the following conditional expression: 2.5<?/S<10.0 (where S indicates the maximum length of a magnification-side image (inch) and ? indicates a magnifying power).

Abstract: The invention is aimed at providing a lens having a wider angle of view, increased relative aperture, and higher quality of images.

Abstract: A method, system and scan lens for use therein are provided for high-speed, laser-based, precise laser trimming at least one electrical element along a trim path. The method includes generating a pulsed laser output with a laser, the output having one or more laser pulses at a repetition rate. A fast rise/fall time, pulse-shaped q-switched laser or an ultra-fast laser may be used. Beam shaping optics may be used to generate a flat-top beam profile. Each laser pulse has a pulse energy, a laser wavelength within a range of laser wavelengths, and a pulse duration. The wavelength is short enough to produce desired short-wavelength benefits of small spot size, tight tolerance, high absorption and reduced or eliminated heat-affected zone (HAZ) along the trim path, but not so short so as to cause microcracking. In this way, resistance drift after the trimming process is reduced.

Abstract: A lens system comprises, on a side closest to an object, a first lens component having a positive refractive power and a second lens component having a positive refractive power in order from the object; and on a side closest to an image, a cemented lens constructed by cementing together a positive lens and a negative lens in order from the object; wherein the lens system satisfies the following conditional expressions: (n1+n2)/2>1.49 (?1+?2)/2>60 where n1 and ?1 denote a refractive index and an Abbe number of the first lens component at d-line, respectively, and n2 and ?2 denote a refractive index and an Abbe number of the second lens component at d-line, respectively.

Abstract: A refractive projection optical system in which a large image side numerical aperture can be ensured by interposing liquid in the optical path to the image plane, and an image having good planarity can be formed while suppressing radial upsizing. The projection optical system comprising a first image forming system arranged in the optical path between a first plane (R) and a point optically conjugate to a point on the optical axis of the first plane, and a second image forming system arranged in the optical path between the conjugate point and a second plane. In the projection optical system, all optical elements having power are refractive optical elements. The optical path between the projection optical system and the second plane is fillable with liquid having a refractive index larger than 1.3.

Abstract: A wide-angle lens module includes a first lens and a second lens with negative refracting power, a third lens with positive refracting power, a fourth lens with negative refracting power, a fifth lens with positive refracting power, a sixth lens with positive refracting power, and a seventh lens with negative refracting power. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are disposed in order from an object side to an image side.

Abstract: Disclosed is a zoom lens, which includes, in sequence from an object side to an image side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, a fifth lens group, a negative sixth lens group and a positive lens group. The first, third, fifth and seventh lens groups are fixed. When the zoom lens is made to zoom from a wide-angle end to a telephoto end, the second and fourth lens groups move toward the third lens group, while the sixth lens group moves toward the seventh lens group. The absolute value of the ratio of the focal distance of the second lens group to that of the sixth lens group is within a range between 0.1 and 0.5.

Abstract: Miniature camera lenses (100, 300) include in order an object side (116, 302) to the image side (118, 304) a first double concave lens (102, 306), a lens group including first convergent meniscus lens (104, 318), a first double convex lens (106, 312), a second convergent meniscus lens (108, 318), a second double concave lens (110, 330), a second double convex lens (112, 336), and a divergent meniscus lens (114, 342). The lenses (100, 300) feature a field of view of about fifty six degrees, low distortion, a relatively long back focal distance, and a relatively low F-number.

Abstract: A fisheye lens system with a half angle-of-view of 90° includes a negative front lens group, a diaphragm, and a positive rear lens group. The negative front lens group includes at least three negative meniscus lens elements each of which has the convex surface facing toward the object; and the three negative meniscus lens elements satisfy the following conditions: 0.2<SF(i=1)<0.6??(1) 0.8<SF(i=2)/SF(i=1)<1.5??(2) 0.8<SF(i=3)/SF(i=1)<2.0??(3) wherein SFi designates the shaping factor of the ith (1?i?3) negative meniscus lens element (SFi=(R1i?R2i)/(R1i+R2i)); R1i designates the radius of curvature of the object-side surface of the ith (1?i?3) negative meniscus lens element; and R2i designates the radius of curvature of the image-side surface of the ith (1?i?3) negative meniscus lens element.

Abstract: A projection lens with a short focal length and high initial aperture is proposed. Such projection lenses are used, for example, in cinema projection. The projection lens is configured such that the sum of the overall length and the back focus (12) is between 2.8 times and 4.5 times the total focal length f?. The entrance pupil is at a distance of between 100 mm and 300 mm from the last lens surface (62; 150), which faces the illuminating mirror. The minimum stop number k of the projection lens is 1.7, and the projection lens is therefore also suitable for illuminating mirrors with a high aperture angle (of up to 17°).

Abstract: An ultraviolet imaging system includes at least two negative lens elements, and at least two positive lens elements. The ultraviolet imaging system satisfies the following conditions: ?3<f(i=330)/r1<?0.5??(1) 65<? (ALL)??(2) 0<?(i=330) (P)??(i=330) (N)<10??(3) wherein f(i=330) designates the focal length of the entire ultraviolet imaging system with respect to a wavelength “i” of 330 nm (base wavelength); r1 designates the radius of curvature of the object-side surface of the most object-side lens element; ? (ALL) designates a reciprocal of a dispersion value, with respect to the d-line, of the glass material of all of the lens elements; ?(i=330) (P) designates the reciprocal of the dispersion value, for the positive lens elements, with respect to the wavelength of 330 nm; and ?(i=330) (N) designates the reciprocal of the dispersion value, for the negative lens elements, with respect to the wavelength of 330 nm.

Abstract: The invention provides a liquid-immersion objective optical system including a first lens group and a second lens group. The first lens group includes a first lens component having positive refractive power, an object side thereof being a flat surface and a convex surface thereof facing an image-plane side; a second lens component having positive refractive power, a convex surface thereof facing the image-plane side; a third lens component having positive refractive power as a whole, formed by cementing a biconvex positive lens and a negative lens; and a fourth lens component formed by cementing a negative lens and a biconvex positive lens. The second lens group includes a fifth lens component formed by cementing a lens having a concave surface facing the object side and a lens having a convex surface facing the image-plane side; a sixth lens component having positive refractive power; and a seventh lens component having negative refractive power.

Abstract: An object of the present invention is to suppress an influence due to temperature change and various aberrations. It is a projection lens which projects an image on a surface of a screen (magnified side). A first group I having a negative refractive power and a second group II having a positive refractive power are arranged in order from a magnified side toward a reduced side. The first group I is configured to arrange a first lens and a second lens in order from the magnified side, and the second group II is configured to arrange a third lens to a seventh lens. The first and second lenses are a negative meniscus lens whose both surfaces are formed by the aspherical surface in which an area near an optical axis of the surface on the magnified side is a concave surface. The third lens is a cemented lens in which a bi-concave lens is cemented to the surface on the reduced side of a bi-convex lens.

Abstract: A lens assembly comprising seven lenses. Each lens includes u greater than or equal to about 12.8°, LEP equal to or from about 100 mm to about 400 mm, &sgr;Rba greater than or equal to about 1°, and &sgr;Rbi less than or equal to about −14°. The outward ray angle slopes and the inward ray angle slopes are positive if the outward ray and the inward ray intersect the optical axis at a location which, when seen from the object, is in an opposite direction to projection. The outward ray angle slopes and the inward ray angle slopes are negative if the outward ray and the inward ray intersect the optical axis at a location which, when seen from the object, is in an opposite direction to projection.

Abstract: An intermediate telephoto lens system includes a first lens group and a second lens group. The first lens group includes a first lens element, a second lens element, a third lens element, an aperture stop, cemented lens elements constituted by a fourth lens element and a fifth lens element, and a sixth lens element. The second lens group includes a seventh lens element and an eighth lens element. Upon focusing, only the first lens group moves along the optical axis. The intermediate telephoto lens system satisfies the following condition: (&ngr;′1-1+&ngr;′1-2)/2>102 . . . (1); &ngr;′1-1: the dispersion ratio of the first lens element; &ngr;′1-2: the dispersion ratio of the second lens element; &ngr;′=(nd−1)/(ng−nF); nd: the refractive index of the d-line for each lens element; ng: the refractive index of the g-line for each lens element n the refractive index of the F-line for each lens element.

Abstract: An image-capturing lens is formed of front and rear lens groups having negative and positive refractive power, respectively, in order from the object side. The rear lens group is formed of, in relative sequential order from the most object side of the rear lens group, a biconvex lens element that is cemented to a biconcave lens element, a biconvex lens element, and a biconvex lens element. A specified condition is satisfied so as to make the cemented lens of the rear lens group insensitive to de-centering errors which may occur either in making the cemented lens or in assembling the image-capturing lens.

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 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 optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, the second lens unit being moved during focusing, wherein the first lens unit has a diffractive optical element of positive refractive power and a first lens subunit of positive refractive power, and the first lens subunit consists of at least one positive lens and at least one negative lens, the optical system satisfying the following conditions: 0.005<&phgr;D/&phgr;1a<0.

Abstract: By satisfying certain specified conditions, a projection lens having six lens groups and a low F-number of 1.4 is disclosed wherein a maximum angle between a principal ray and the optical axis on the reducing side of the projection lens is 2.5.degree. or less. This enables the projection lens to be used with a display which must be illuminated by light that is orthogonal to a display surface (as is the case with a liquid crystal display) without significant loss of light at the periphery of the image. Further, the projection lens can have its aberrations favorably corrected and be compact.

Abstract: In a large-aperture lens for low-illuminance imaging, a Gauss type lens configuration is employed, and a negative lens having a predetermined refracting power is inserted in front of the front-side cemented lens, whereby back focus is secured while compactness is attained, without using an aspherical lens. Successively disposed from the object side are a biconvex lens L.sub.1, a positive meniscus lens L.sub.2 having a convex surface directed onto the object side, a negative lens L.sub.3 having a concave surface with a stronger curvature directed onto the image side, a positive meniscus lens L.sub.4 (cemented with lens L.sub.5) having a convex surface directed onto the object side, a negative meniscus lens L.sub.5 having a concave surface directed onto the image side, a biconcave lens L.sub.6 (cemented with lens L.sub.7) having a surface with a stronger curvature directed onto the object side, biconvex lenses L.sub.7 and L.sub.

Abstract: A standard lens system composed, in order from the object side, of a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power: the first lens unit being composed of at least one positive meniscus lens component which has a convex surface on the object side, and at least one doublet which consists of a positive meniscus lens component and a negative lens component; the second lens unit being composed of at least one cemented doublet which consists of a negative lens element and a positive lens element, and a positive lens component; and the third lens unit being composed of at least one positive lens component and a negative lens component or at least one negative lens component.

Abstract: A compact wide-angle photographic lens system of a retrofocus type includes, from the object side, a first, a sixth, and a seventh meniscus lens group of positive refractive powers, a second and a third meniscus lens group of negative refractive powers, a fourth lens group of a positive refractive power being convex toward an object side, and a fifth cemented lens group of a negative refractive power. The lens system satisfies the conditions, 1.0 f<.vertline.f.sub.(1,2,3,4) .vertline.<2.0 f, f.sub.(1,2,3,4) <0, 0.4 f<d(6)+d(7)<0.6 f, 0.1<f/r(5)<0.2, 0.5<f/r(11)<0.7, 1.65<?n(7)+n(8)!/2<1.75, where f represents a focal length of overall lens system, f.sub.

Abstract: The present invention relates to a both-side telecentric projection optical system and an exposure apparatus equipped with this projection optical system. In particular, the projection optical system has a structure for quite favorably correcting various kinds of aberration such as distortion in particular, while securing a relatively broad exposure area and a large numerical aperture.

Abstract: A rear attachment is provided to permit objective lens systems designated for a certain image format to be used for imaging on a smaller image format. Thus, a 35 mm single lens reflex camera lens can be used to create an image on a smaller format CCD array.

Abstract: A wide-angle fast lens system includes a front lens group having a negative power, a diaphragm and a rear lens group having a positive power. The front lens group consists of a first sub-lens group and a second sub-lens group having a negative power. The lens system satisfies the following relationships:-0.6<f/f.sub.F <-0.2,6.0<.SIGMA.d.sub.F+S /f<12.0,f/.vertline.f.sub.1a .vertline.<0.07, and0.4<h.sub.aF /h.sub.aL <0.65,wherein "f" represents the focal length of the whole lens system, "f.sub.F " represents the focal length of the front lens group, ".SIGMA.d.sub.F+S " represents the sum of the thickness of the front lens group and the distance between the front and rear lens groups, "f.sub.1a " represents the focal length of the first sub-lens group, "h.sub.aF " represents the height of the paraxial rays incident on the first surface of the first sub-lens group, and "h.sub.aL " represents the height of the paraxial rays incident on the last surface of the first sub-lens group.

Abstract: An optical system includes, in the following order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, the second lens unit comprising, in the following order from the object side, a front lens group of a negative refractive power and a rear lens group of a negative refractive power, and a third lens unit having a positive refractive power. In the optical system, focusing to a short-distance object is attained by moving the second lens unit toward the image side, and the optical system satisfies:2.5<f2R/f2F<50.ltoreq.D2/f.ltoreq.0.10.15<1/(.vertline..phi.2F.vertline..multidot.f)<0.25where f2F is the focal length of a negative lens, closest to the object side, in the second lens unit, f2R is the focal length of a negative lens, closest to the image side, in the second lens unit, f is the focal length of the entire optical system, .phi.

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 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: A fast lens system is provided which includes a front lens group having a negative power, a diaphragm, and a rear lens group having a positive power, arranged in this order from a side of an object of the lens system. The lens system satisfies the following conditions:-0.5<f/f,<-0.2; (1)1.0<.SIGMA.d.sub.F+S /f<3.0; (2)ana1.5<.SIGMA.d.sub.R /f<3.0, (3)wherein f represents a focal length of the entire lens system, f.sub.F represents a focal length of the front lens group, .SIGMA.d.sub.F+S represents a sum of the thickness of the front lens group and the distance between the front lens group and the rear lens group, and .SIGMA.d.sub.R represents a thickness of the rear lens group.