Abstract: A zoom optical system (ZL) comprises: a first lens group (G1) disposed closest to an object and having a positive refractive power; an aperture stop (S) disposed closer to an image than the first lens group (G1); a positive lens component disposed so as to oppose the image side of the aperture stop (S); and a lens group (G3) having the positive lens component, wherein a distance between the first lens group (G1) and the lens group (G3) having the positive lens component changes during zooming, at least one lens surface of the positive lens component has an aspherical surface, and the following conditional expression, 0.40<fp/fGp<3.60 is satisfied, where fp: a focal length of the positive lens component, and fGp: a focal length of the lens group (G3) having the positive lens component.

Abstract: A rear conversion lens includes: a chassis including two opposite ends, the chassis including light-transmitting holes on the ends, respectively; a first coupler configured to detachably couple one of the ends of the chassis with an image field side of an image-pickup lens of a three-chip camera including three first image sensors, the image-pickup lens being designed based on an assumption that the image-pickup lens is to be used with a color-separation prism in combination; a second coupler configured to detachably couple the other end of the chassis with a single-chip color camera including a second image sensor, the second image sensor including an image field larger than an image field of the first image sensors of the three-chip camera; and an optical system including a first lens group, a second lens group, and a third lens group arranged in the chassis in this order from an object side, the first lens group having a negative compound focal length, the second lens group being configured to correct a sp

Abstract: An optical image capturing system, sequentially including a first lens element, a second lens element, a third lens element and a fourth lens element from an object side to an image side, is disclosed. The first lens element has positive refractive power. The second lens element, the third lens element and the fourth lens element have refractive power respectively. At least one of the image side surface and the object side surface of each of the four lens elements are aspheric. The optical lens elements can increase aperture value and improve the imagining quality for use in compact cameras.

Abstract: A compact, wide view-field imaging lens with a small F-value which corrects aberrations properly. Its elements are arranged in order from an object side to an image side: an aperture stop, positive first lens having convex surfaces on the object and image sides, negative second lens having a concave object-side surface near an optical axis, positive meniscus third lens having a convex image-side surface, and negative meniscus double-sided aspheric fourth lens having a concave image-side surface near the optical axis. Its F-value is smaller than 2.4 and it satisfies conditional expressions (1) to (3) below: 0.15<f12/f34<0.5 ??(1) 0.1<|r1/r2|<0.5 ??(2) 1.0<f1/f3<1.6 ??(3) where f1: first lens focal length f3: third lens focal length f12: composite focal length of the first and second lenses f34: composite focal length of the third and fourth lenses r1: curvature radius of the first lens object-side surface r2: curvature radius of the first lens image-side surface.

Abstract: Provided is a zoom lens, including, in order from an object: a first lens group (G1) having positive refractive power; a second lens group (G2) having negative refractive power; a third lens group (G3) having positive refractive power; and a fourth lens group (G4) having positive refractive power. The first lens group (G1 includes only, in order from the object, a cemented lens of a negative lens (L11) and a positive lens (L12), and a positive meniscus lens (L13) having a convex surface facing the object, an aperture stop (S) for determining brightness is disposed to the object side of the third lens group (G3), and upon zooming, all of the four groups (G1 to G4) move and the aperture stop (S) moves together with the third lens group (G3), and the conditional expression ?dp1>85.0 is satisfied, where ?dp1 denotes an Abbe number of the positive lens (L12), which is disposed closest to the object in the first lens group (G1), at the d-line as a standard.

Abstract: An optical lens assembly for image taking includes a first lens element, a second lens element, a third lens element and a fourth lens element. The first lens element with positive refractive power includes a convex object-side surface at a paraxial region. The second lens element with negative refractive power includes a concave object-side surface at a paraxial region. The third lens element with refractive power includes a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region. The fourth lens element made of plastic with negative refractive power includes a concave object-side surface at a paraxial region and an image-side surface. Both of the object-side surface and the image-side surface of the fourth lens element are aspheric, and the image-side surface of the fourth lens element is concave at a paraxial region and convex at a peripheral region.

Abstract: An optical system includes, in order from an object side to an image side, a first lens unit of a positive refractive power, an aperture diaphragm, and a second lens unit of a positive refractive power. The first lens unit includes, in order from the object side to the image side, a cemented lens Lp1 made by joining a first lens of a positive refractive power and a second lens of a negative refractive power with each other, and a third lens of a positive refractive power which has a meniscus shape. The predetermined conditions are satisfied.

Abstract: To provide a projection lens that is compact, lightweight, low-cost, and readily portable, a first lens having a positive power and at least one surface that is an aspheric surface; a second lens having a negative power and having a concave surface on the magnification side; a third lens having a positive power and having a convex surface on the reduction side; and a fourth lens having a positive power are arranged in order from the magnification side. In addition to arranging the lenses telecentrically on the reduction side, the following formulas are satisfied simultaneously, and images formed on the conjugation surface on the reduction side are enlarged and projected on the conjugation surface on the magnification side: formula (A) 0.8<Bf/f; formula (B) 1.1<f1/f<1.6; formula (C) Nd1<1.7, formula (D) vd1<35.

Abstract: There is provided a zoom lens including a first focus lens group having negative refractive power and moving in orientation to an image side along an optical axis in focusing from a long distance to a short distance, and a second focus lens group having positive refractive power, the second focus lens group being arranged on a closer side to an image relative to the first focus lens group and moving along the optical axis in focusing. The first and second focus lens groups move in association with each other.

Abstract: In a zoom lens including a positive first lens unit, negative second lens unit, positive third lens unit, and positive fourth lens unit, the fourth lens unit includes a 41 lens group, a 42 lens group, and a 43 lens group. the lateral magnification of the third lens unit at a wide-angle end when an infinite object is focused, the focal length of the fourth lens unit, the lens configuration length of the fourth lens unit, the air interval between the 41 and 42 lens groups, the air interval between the 42 and 43 lens groups, the focal length of the 42 lens group, the average values of the Abbe constants and partial dispersion ratios of positive lens of the 42 lens group, the average values of the Abbe constants and partial dispersion ratios of negative lenses of the 42 lens group, and the like are appropriately set.

Abstract: A zoom lens includes a first lens unit, a second lens unit, a third lens unit and a fourth lens unit that includes a 41 lens group and a 42 lens group. The 41 lens group includes a 411 lens group and a 412 lens group. A lens surface on a most image side of the 411 lens unit has a shape convex to the image side and a lens surface on the most object side of the 412 lens unit has a shape concave to the object side. A curvature radius r411 of the lens surface on the most image side of the 411 lens unit, a curvature radius r412 of the lens surface on the most object side of the 412 lens unit, and lateral magnification ?3w of the third lens unit at a wide-angle end are respectively appropriately set.

Abstract: An image capturing lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element. The first lens element with positive refractive power has a convex object-side surface in a paraxial region thereof and a convex image-side surface in a paraxial region thereof. The second lens element with negative refractive power has a concave object-side surface in a paraxial region thereof and a convex image-side surface in a paraxial region thereof. The third lens element with positive refractive power has a concave object-side surface in a paraxial region thereof and a convex image-side surface in a paraxial region thereof. The fourth lens element with refractive power has a concave image-side surface in a paraxial region thereof. The image capturing lens assembly has a total of four lens elements with refractive power.

Abstract: A real-image variable-magnification viewfinder substantially consists of, in order from the object side: an objective lens system substantially consisting of a positive first lens, a negative second lens, a positive third lens, and a positive fourth lens; an erect optical system formed by a plurality of optical members; and a positive eyepiece lens system. The first lens and the third lens are fixed relative to the optical axis direction during magnification change, and the second lens and the fourth lens are moved in the optical axis direction during magnification change. All optical surfaces of all the optical members forming the erect optical system are planar surfaces. At least one of the optical members forming the erect optical system is made of a glass material. A predetermined conditional expression is satisfied.

Abstract: A zoom lens includes, in order from an object side to an image side: a positive first lens unit; a negative second lens unit; a positive third lens unit; and a positive fourth lens unit, wherein the first lens unit includes a positive first lens subunit, which does not move for focusing, a positive second lens subunit, which moves during the focus adjustment, and a positive third lens subunit, which does not move for focusing; and focal lengths of the first lens unit, the second lens unit, the third lens unit, a magnification of the third lens unit U3 at a wide angle end, focal lengths of the first lens subunit, the second lens subunit appropriately satisfy certain relations.

Abstract: A zoom lens includes, in order from an object side to an image side, a positive first lens unit, a negative second lens unit, an aperture stop, a positive third lens unit, and a positive fourth lens unit. The third lens unit includes, in that order, a positive first lens sub-unit, and a negative second lens sub-unit. The second lens sub-unit is movable in a direction having a component perpendicular to an optical axis to change an image forming position in a direction perpendicular to the optical axis. A distance on the optical axis between the aperture stop and the third lens unit at a wide-angle end, a composite focal length of the first lens unit and the second lens unit at the wide-angle end, a focal length of the first lens sub-unit, and a focal length of the second lens sub-unit are appropriately set.

Abstract: A zoom lens includes first to third lens units having positive, negative, and positive refractive power, respectively, and a rear lens group having positive refractive power. An aperture stop is arranged between a lens surface of the second lens unit closest to the image side and a lens surface of the third lens unit closest to the image side. The third lens unit includes first and second positive lenses each including an aspheric surface, and a negative lens. In the third lens unit, a refractive index of the first positive lens, and an Abbe number and relative partial dispersion of the second positive lens are appropriately set.

Abstract: A high zoom-ratio zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group. Upon zooming, the distance between the first and second lens groups increases, the distance between the second and third lens groups decreases, and the distance between the third and fourth lens groups increases. The first lens group includes a negative lens element, and two positive lens elements. The absolute value of the radius-of-curvature of the image-side surface of the negative lens element within the first lens group is smaller than the absolute value of the radius-of-curvature of the object-side surface of the positive lens element on the object side within the first lens group. The following condition (1) is satisfied: 1.95<n11??(1), wherein n11 designates the refractive index at the d-line of the negative lens element within the first lens group.

Abstract: Provided is an imaging lens including a fixed first lens group having a positive refractive power and including a plurality of lenses, a second lens group serving as a focus group and including a negative lens, and a third lens group having a positive refractive power that are arranged sequentially from an object side to an image side. A stop is disposed between predetermined lenses of the first lens group, and, on an assumption that a lens group located closer to the object side than the stop of the first lens group is a 1ath lens group and a lens group located closer to the image side than the stop is a 1bth lens group, Condition Equation (1) below is satisfied: 0.7<f/f1b<2.0,??(1) where f is a focal distance of an entire system and f1b is a focal distance of the 1bth lens group.

Abstract: An optical image capturing lens system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element. The first lens element with positive refractive power has a convex object-side surface. The second lens element has negative refractive power. The third lens element has positive refractive power, wherein an object-side surface and an image-side surface of the third lens element are aspheric. The fourth lens element with refractive power is made of plastic material and has a concave image-side surface, wherein an object-side surface and the image-side surface of the fourth lens element are aspheric, and the fourth lens element has at least one inflection point formed on at least one of the object-side surface and the image-side surface thereof.

Abstract: An image lens, in order from an object side to an image side thereof, includes a first lens including a first surface and a second surface, a second lens including a third surface and a fourth surface, a third lens including a fifth surface and a sixth surface, a fourth lens including a seventh surface and a eighth surface, and an image plane. The image lens satisfies the following formulas: D/TTL>1.11; D/L>1.13; Z/Y>0.076; wherein D is the maximum image diameter of the image plane; TTL is a total length of the image lens; L is a distance from an outermost edge of the eighth surface to an optical axis of the image lens; Z is a distance from a central point of the sixth surface to an outermost edge of the sixth surface; and Y is a distance from the outermost edge of the sixth surface to the optical axis.

Abstract: A zoom lens system, in order from an object side to an image side, comprising a positive first lens unit, a negative second lens unit, a positive third lens unit, and a positive fourth lens unit, wherein the first lens unit is composed of a cemented lens element of one object side negative lens element and one image side positive lens element, the fourth lens unit is composed of one lens element, in zooming, the first to fourth lens units are individually moved along an optical axis so that air spaces between the respective lens units vary for magnification change, and the conditions: vdL12<43.50 and fT/fW?6.0 (vdL12: an Abbe number of the positive lens element in the first lens unit, fT and fW: focal lengths of the entire system at a telephoto limit and a wide-angle limit) are satisfied; an imaging device; and a camera.

Abstract: A zoom lens includes a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power. The first to fourth lens units move during zooming. The first lens unit includes a cemented lens obtained by cementing negative and positive lenses, the second lens unit includes negative, negative, and positive lenses, the third lens unit includes positive and negative lenses, and the fourth lens unit includes a positive lens. Movement amounts M1 and M3 of the first and third lens units, respectively, during zooming from the wide-angle end to the telephoto end and focal lengths f1 and f3 of the first and third lens units, respectively, are appropriately set based on predetermined mathematical conditions.

Abstract: A zoom lens includes a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, a third lens unit of a positive refractive power, and a fourth lens unit of a positive refractive power, wherein the first lens unit does not move for zooming, at least the second and fourth lens units are moved during zooming, the first lens unit includes at least one positive lens, and an Abbe number and a relative partial dispersion of a material of the positive lens, an average refractive index of materials of negative lenses included in the second lens unit, a movement amount of the second lens unit for zooming from a wide-angle end to a telephoto end, a focal length of the second lens unit, and a focal length of the entire zoom lens at the telephoto end are appropriately set.

Abstract: Providing for a fixed focus optical system exhibiting extended depth of field is provided herein. By way of example, a compact and fast optical system that yields an asymmetric modulation transfer function (MTF) is disclosed. In some aspects, the asymmetric MTF results in extended depth of field for near field objects. Such a response can be particularly beneficial for small handheld cameras or camera modules having high resolution. According to some disclosed aspects, the resolution can be about 8 mega pixels. Additionally, the optical system can comprise four lenses in one aspect and five lenses in another, while remaining below about 5.3 mm total track length (TTL) for the respective systems. In at least one application, the disclosed optical systems can be employed for a high resolution compact camera, for instance in conjunction with an electronic computing device, communication device, display device, surveillance equipment, or the like.

Abstract: A zoom lens optical system includes a first lens unit having a positive refractive index, a second lens unit which is arranged behind the first lens unit and has a negative refractive index, a third lens unit which is arranged behind the second lens unit and has a positive refractive index, and a fourth lens unit which is arranged behind the third lens unit and has a positive refractive index. An aperture is arranged within the third lens unit to prevent reduction of shutter speed due to large diameter of the zoom lens optical system.

Abstract: An imaging lens includes a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; and a fourth lens having positive refractive power, arranged from an object side to an image plane side. In the first lens, a curvature radius on an object-side surface is positive and a curvature radius of an image-side surface is negative. In the second lens, curvature radii of an object-side surface and an image-side surface are both positive. In the third lens, curvature radii of an object-side surface and an image-side surface thereof are both negative. When the whole lens system has a focal length f and a distance from the object-side surface of the first lens to an image-side surface of the fourth lens is L14, the imaging lens satisfies the following expression: 0.5<L14/f<0.

Abstract: An imaging lens, although compact, has satisfactorily corrected aberrations. The imaging lens is configured by disposing, in sequence from the object side, a stop (ST); a first lens (L1), which has a double convex shape near the optical axis; a meniscus-shaped negative second lens (L2) which has near the optical axis a convex surface facing the object side; a meniscus-shaped positive third lens (L3) which has near the optical axis a concave surface facing the object side; and a positive fourth lens (L4) which has a double convex shape near the optical axis. In the configuration, the refractive power of the first lens (L1) is greater than the refractive power of each of the second lens (L2), the third lens (L3), and the fourth lens (L4).

Abstract: Provided is a zoom lens for imaging an object on an imaging surface. The zoom lens includes, in the order from an object side to an image side thereof, a first lens group with positive refraction power, a second lens group with negative refraction power, a third lens group with positive refraction power, and a fourth lens group with positive refraction power. The first lens group includes a first surface. The zoom lens satisfies the formula: 0.15<|L3|/Lt<0.25, where L3 is a distance of the movement of the third lens group along an optical axis of the zoom lens when the zoom lens is switched between a wide-angle state and a telephoto state, and Lt is a distance from the first surface to the imaging surface.

Abstract: A photographing optical lens assembly includes, in order from an object side to an image side, a first lens element with positive refractive power having a convex object-side surface, a second lens element with negative refractive power having a concave object-side surface and a convex image-side surface, a third lens element with positive refractive power having a convex object-side surface and a convex image-side surface, and a fourth lens element having a convex object-side surface and a concave image-side surface with both surfaces thereof being aspheric.

Abstract: An optical image lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element. The first lens element with positive refractive power has a convex object-side surface. The second lens element has refractive power. The third lens element with refractive power is made of plastic material, wherein an object-side surface and an image-side surface of the third lens element are aspheric. The fourth lens element with negative refractive power is made of plastic material, and has a concave image-side surface, wherein an object-side surface and the image-side surface of the fourth lens element are aspheric, and the fourth lens element has at least one inflection point formed on at least one of the object-side surface and the image-side surface thereof.

Abstract: A zoom lens comprising, in order from an object side: a first lens group G1 having positive refractive power; a second lens group G2 having negative refractive power; and a third lens group G3 having positive refractive power; each distance between said lens groups adjacent to each other changing upon zooming from a wide-angle end state to a telephoto end state, said first lens group G1 having a cemented lens including a negative lens L11, and said third lens group G3 having a cemented lens L32 and L33, and a given conditional expression being satisfied, thereby providing a downsized zoom lens having high optical performance.

Abstract: An optical lens for image pickup, sequentially arranged from an object side to an image side, comprising: the first lens element with positive refractive power having a convex object-side surface, the second lens element with negative refractive power having a convex object-side surface and a concave image-side surface, the plastic third lens element with positive refractive power having a concave object-side surface and a convex image-side surface with both being aspheric, the plastic fourth lens element with positive refractive power having a convex object-side surface and a concave image-side surface with both being aspheric. By such arrangements, the optical lens for image pickup satisfies conditions related to reduce the sensitivity and to shorten the total length for use in compact cameras and mobile phones with camera functionalities.

Abstract: This invention provides an optical imaging lens system in order from an object side to an image side including: a first lens element with positive refractive power having a convex object-side surface and a concave image-side surface, a second lens element with negative refractive power having a convex object-side surface and a concave image-side surface, a third lens element with positive refractive power, and a fourth lens element having a concave image-side surface, and at least one of the object-side and image-side surfaces thereof being aspheric; wherein the optical imaging lens system further comprises an aperture stop and an electronic sensor on which an object is imaged, and the aperture stop is positioned between an object and the first lens element; wherein there are four lens elements with refractive power. By such arrangement, total track length and photosensitivity of the optical imaging lens system can be effectively reduced while retaining high image quality.

Abstract: An image pickup optical system having five lenses includes in order from an object side, a first lens having a biconvex shape, and a positive refractive power, a second lens having a negative refractive power, a third lens having a meniscus shape with a concave surface thereof directed toward the object side, and a negative refractive power, a fourth lens having a meniscus shape with a concave surface thereof directed toward the object side, and a positive refractive power, and a fifth lens having a negative refractive power. The third lens and the fourth lens are cemented, and the negative refractive power at a central portion of the third lens increases gradually toward a peripheral portion thereof, and the positive refractive power at a central portion of the fourth lens decreases gradually toward a peripheral portion thereof.

Abstract: A high-performance zoom lens system which is compact and has a wide view angle at a wide-angle limit and a high zooming ratio in a balanced manner, in order from an object side to an image side, comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein the first lens unit is composed of at most two lens elements, the second lens unit is composed of two lens elements, the third lens unit is composed of three lens elements, in order from the object side to the image side, including an object side lens element having positive optical power, a lens element having negative optical power, and an image side lens element having positive optical power, and the conditions: ?2.0<f2/fW<?1.1, fT/fW>6.

Abstract: A zoom lens including, in a sequence from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a succeeding lens group having an overall positive refractive power, and having a high zoom magnification and a compact size.

Abstract: An image pickup apparatus having a simple configuration and being capable of performing switching between an image pickup mode based on a light field photography technique and a normal high-resolution image pickup mode is provided. The image pickup apparatus includes an image pickup lens 11, a microlens array section 12 where light passing through the image pickup lens 11 enters, and an image pickup device 13 sensing light emitted from the microlens array section 12, and the focal length of each of microlenses constituting the microlens array section 12 is variable in response to an applied voltage.

Abstract: A zoom optical system in which: a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group are arranged in that order from the object side and magnification is changed by properly changing distances between these lens groups; the first lens group consists of only one lens element and the most object-side surface of the first lens group has a convex shape which faces toward the object side; the second lens group includes, in order from the object side, a negative single lens, a negative cemented lens, and a positive single lens; and the following condition (1) or (2) is satisfied: 0.2??Dw-w10/Lt?0.

Abstract: A lens system includes, in order from an object side, a first lens group with positive refractive power, a second lens group with negative refractive power that moves during zooming, a third lens group with positive refractive power, and a fourth lens group with positive refractive power that moves during zooming and focusing adjustments. The first lens group includes a lens with positive refractive power and an Abbe number vd1x that satisfies a following condition (vd1x>80). The second lens group includes a lens with positive refractive power and an Abbe number vd2x and two lenses with negative refractive power and Abbe numbers vd2y and vd2z respectively, the Abbe numbers Vd2x, Vd2y and Vd2z satisfying following conditions (vd2x, vd2y, vd2z<23). The third lens group includes a plurality of lenses with positive refractive power, an average vd3a of the Abbe numbers of the plurality of lenses with positive refractive power satisfies a following condition (77.5<vd3a<82.

Abstract: An imaging lens, although compact, has satisfactorily corrected aberrations. The imaging lens is configured by disposing, in sequence from the object side, a stop (ST); a first lens (L1), which has a double convex shape near the optical axis; a meniscus-shaped negative second lens (L2) which has near the optical axis a convex surface facing the object side; a meniscus-shaped positive third lens (L3) which has near the optical axis a concave surface facing the object side; and a positive fourth lens (L4) which has a double convex shape near the optical axis. In the configuration, the refractive power of the first lens (L1) is greater than the refractive power of each of the second lens (L2), the third lens (L3), and the fourth lens (L4).

Abstract: A zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, which are arranged in this order from the object side of the zoom lens. The focal length of the entire system of the zoom lens is changeable by changing a distance between the second lens group and the third lens group. The first lens group includes two cemented lenses, each composed of a negative meniscus lens and a positive lens cemented together in this order from the object side, and a positive lens, and the two cemented lenses and the positive lens being arranged in this order from the object side. Further, a predetermined formula related to the focal length of the first lens group and the focal length of the entire system is satisfied.

Abstract: A lens system, in order from the object, includes positive first lens, negative second lens, positive third lens, positive fourth lens, and an aperture stop positioned between the third and fourth lens. The second lens includes a first optical portion, a first support portion surrounding the first optical portion with a first surface and second surface. The third lens includes a second optical portion and a second support portion surrounding the second optical portion with a third surface and fourth surface. The fourth lens includes a light stop surface facing the object side of the lens system. The lens system satisfies the formulas: d23<1.1×d34, where the d23 is a distance along the optical axis of the lens system from the second surface to the third surface, and the d34 is a distance along the optical axis from the fourth surface to the light stop surface.

Abstract: An imaging lens includes a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; and a fourth lens having positive refractive power, arranged from an object side to an image plane side. In the first lens, a curvature radius on an object-side surface is positive and a curvature radius of an image-side surface is negative. In the second lens, curvature radii of an object-side surface and an image-side surface are both positive. In the third lens, curvature radii of an object-side surface and an image-side surface thereof are both negative. When the whole lens system has a focal length f and a distance from the object-side surface of the first lens to an image-side surface of the fourth lens is L14, the imaging lens satisfies the following expression: 0.5<L14/f<0.

Abstract: A zoom lens includes, sequentially from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group. During zooming from a wide angle position to a telephoto position, the interval between the first lens group and the second lens group increases, the interval between the second lens group and the third lens group decreases, and an interval between the third lens group and the fourth lens group varies. The fourth lens group includes, sequentially from the object side, a first sub-lens group having a positive refractive power, a second sub-lens group having a negative refractive power, and a third sub-lens group. The second sub-lens group of the fourth lens group is moved along an optical axis to perform focusing.

Abstract: The present invention is a variable power zoom lens that is suitable to APS-format single-lens reflex cameras. The zoom lens has the foremost or first lens group G1 of positive refractivity, the second lens group G2 of negative refractivity, the third lens group G3 of positive refractivity, and the fourth lens group G4 of positive refractivity disposed in sequence from a position closer to the object toward the image plane, and it meets requirements as defined in conditional formulae as follows: 6<Lw/(Ft/Fw)<10 where Lw is the entire length of the lens optics (i.e., from the front surface of the foremost lens piece to the image plane) at the wide-angle end, Ft is a focal length of the lens optics in whole at the telephoto end, and Fw is the focal length of the lens optics in whole at the wide-angle end.

Abstract: There is provided an imaging optical system installed in a mobile communications terminal and a personal digital assistant (PDA) or utilized in a surveillance camera and a digital camera. The imaging optical system including, sequentially from an object side in front of an image plane: a first lens having positive refractive power and two convex surfaces; a second lens having negative refractive power and two concave surfaces; a third lens having positive refractive power and a meniscus shape; and a fourth lens having a concave object-side surface. The fourth lens has a shape satisfying following condition 1: 10<|R8/F|<50??condition 1, where R8 is a radius of curvature of the object-side surface of the fourth lens, and F is an overall focal length of the imaging optical system.

Abstract: An image forming optical system of the present invention includes at least one cemented lens which includes a first lens element (e1), a second lens element (e2), and a third lens element (e3). The first lens element e1 is cemented to a surface on one side of the second lens element e2, and the third lens element e3 is cemented to the other surface of the second lens element e2. The first lens element e1 is a positive lens, and a combined refracting power of the second lens element e2 and the third lens element e3 is negative. The cemented lens satisfies a predetermined conditional expression.

Abstract: A zoom lens comprises a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a rear group including at least one lens unit, in order from an object side to an image side. Each of the lens units is configured to move so that a total lens length at a wide-angle end is longer than that at a telephoto end to perform a zoom operation. A movement amount M1 of the first lens unit at the wide-angle end and the telephoto end with respect to an imaging surface, a focal length f1 of the first lens unit, and focal lengths fw and ft of a whole system at the wide-angle end and the telephoto end are appropriately set.

Abstract: A zoom lens includes, sequentially from an object side, a positive first lens group; a negative second lens group; a positive third lens group; and a positive fourth lens group, where 2.0?D23W/FW?3.0 is satisfied. D23W is an interval, at a wide angle edge, between a lens that among lenses of the second lens group, is farthest on an imaging plane side and a lens that among lenses of the third lens group, is farthest on the object side. FW is a focal length of an optical system of the zoom lens at infinity focus, at the wide angle edge.

Abstract: A vari-focal length lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. In the second lens group, each of the object-side surface of the negative lens arranged on the object side and the object-side surface of the positive lens is formed in an aspherical shape and satisfies the following conditional expression: 2.0<f1/(fw·ft)1/2<2.5 wherein f1 is a focal length of the first lens group, fw is a focal length in the whole lens system in a wide angle end state, and ft is a focal length in the whole lens system in a telephoto end state.