Abstract: An optical unit that is configured of a three-group wide-angle lens, that is capable of suppressing optical distortion to a small amount, that has favorable optical characteristics, and that is tolerant of reflow, and an image pickup apparatus are provided. An optical unit 100 includes: a first lens group 110 including a first lens element 111; a second lens group 120 including a second lens element 121, a first transparent member 122, and a third lens element 123 that are arranged in order from object plane toward image plane; and a third lens group 130 including a fourth lens element 131, a second transparent member 132, and a fifth lens element 33 that are arranged in order from the object plane toward the image plane, the first lens group 110, the second lens group 120, and the third lens group 130 being arranged in order from the object plane toward the image plane.

Abstract: An optical imaging lens assembly comprises, 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. There is a stop disposed between the first lens element and the third lens element. The first lens element has negative refractive power, the second lens element has positive refractive power, the third lens element has negative refractive power, and the fourth lens element has positive refractive power. The first lens element has a convex object-side surface and a concave image-side surface. The third lens element and the fourth lens element both have at least one of its object-side surface and its image-side surface being aspheric. With the aforementioned arrangement, the optical imaging lens assembly of the present invention can obtain a larger viewing angle, lower sensitivity and higher resolution.

Abstract: Provided are a wide angle optical system having better optical performance, low in cost, and compact in size, an imaging lens device having the wide angle optical system, a monitor camera, and a digital apparatus. The wide angle optical system (1) has, in order from the object side to the image side, a first lens (11) having a negative optical power, a second lens (12) having a negative optical power, a third lens (13) having a positive optical power, an aperture (15), and a fourth lens (14) having a positive optical power. The wide angle optical system satisfies the conditional expression of 3<f34/f<10, where f34 is the composite focal length of the third and fourth lenses (13, 14) and f is the focal length of the entire system.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power. A distance between the first lens unit and the second lens unit varies during zooming. The first lens unit includes, in order from the object side to the image side, a negative lens and a positive lens of which an object-side lens surface has a convex shape. An Abbe number of a material of the positive lens of the first lens unit, a focal length of the first lens unit, a distance between an image-side lens surface of the first lens unit and an object-side lens surface of the second lens unit at a telephoto end, and focal lengths of the entire zoom lens at a wide-angle end and the telephoto end are appropriately set.

Abstract: With comprising, in order from an object side: a first lens L1 constructed by a negative meniscus lens having a convex surface facing the object side; a cemented lens component CL1 having positive refractive power as a whole constructed by a second lens L2 having positive refractive power and a third lens L3 having negative refractive power; a fourth lens L4 having negative refractive power; a fifth lens L5 having positive refractive power; and a sixth lens L6 having positive refractive power, and the following expression being satisfied: 0.01<d2/(?f1)<0.15 where d2 denotes a distance along an optical axis between the first lens and the second lens, and f1 denotes a focal length of the first lens, a compact lens system having superb optical performance with correcting various aberrations, a wide-angle lens, an optical apparatus equipped therewith, and a method for manufacturing the lens system are provided.

Abstract: Disclosed herein is an imaging lens. The imaging lens according to a preferred embodiment of the present invention includes a first lens having positive (+) power and having both sides formed to be convex, a second lens having negative (?) power and formed to be concave toward a top side, a third lens having positive power and having both sides formed to be convex, a fourth lens having positive (+) power and formed to be convex toward a top side, and a fifth lens having negative (?) power and formed to be concave toward the top side, wherein the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are disposed in order from an object side.

Abstract: A projection lens system includes, in order from a screen-side to an SLM-side thereof, a first lens group of negative refractive power which includes a first lens, and a second lens group of positive refractive power. The second lens group includes a second to fifth lenses in order from the screen-side to the SLM-side of the projection lens system. The projection lens system satisfies the following condition formulas: 1.95<|F1/Fw|<2.15, 0.5<|f4/Fw|<0.7, and 1.05<|f5/Fw|<1.25, where F1 is the effective focal length of the first lens group, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens, Fw is the effective focal length of the projection lens system which is in the wide-angle state.

Abstract: A projection lens system includes, in order from the magnified side to the reduced side thereof, a first lens group with negative refractive power, and a second lens group with a positive refracting power. The first lens group includes a first lens having a negative refracting power. The projection lens system satisfies the following condition: 4.5<|F1|/F<6; wherein F1 is the effective focal length of the first lens; F is the effective focal length of the projection lens system.

Abstract: Provided is a small-sized five-element image pickup lens which ensures a sufficient lens speed of about F2 and exhibits various aberrations being excellently corrected. The image pickup lens is composed of, in order from the object side, a first lens with a positive refractive power, including a convex surface facing the object side; a second lens with a negative refractive power, including a concave surface facing the image side; a third lens with a positive or negative refractive power; a fourth lens with a positive refractive power, including a convex surface facing the image side; and a fifth lens with a negative refractive power, including a concave surface facing the image side. The image-side surface of the fifth lens has an aspheric shape, and includes an inflection point at a position excluding an intersection point with the optical axis.

Abstract: A projection lens system, in the order from a magnified side to a reduced side, includes a first lens group with negative refraction power and a second lens group with positive refraction power. The projection lens system satisfies the formulas: ?1.55<F1/F2<?1.12; wherein F1 is the effective focal length of the first lens group, and F2 is the effective focal length of the second lens group.

Abstract: A projection lens includes, in order from the magnification end to the minimization end thereof: a first lens group of a negative refractive power; and a second lens group of a positive refractive power. The projection lens satisfies the formula: 0.061<F/L<0.078; where F represents the effective focal length of the projection lens and L represent the total length of the projection lens.

Abstract: Provided is a high-performance objective optical system which is compatible with a high-pixel-count image acquisition device, in which focusing can be achieved according to a change in object point distance and which has sufficient depth of field at the individual object point distances. Provided is an objective optical system (1) including, in order from an object side, a first group (G1), a second group (G2), and a third group (G3), in which the first group (G1) includes, in order from the object side, a plano-concave lens (L1) and a meniscus lens (L2) whose convex surface is towards an image side and in which the second group (G2) includes a positive meniscus lens whose convex surface is towards the object side and moves in the direction of an optical axis to perform focusing.

Abstract: This invention provides an imaging optical lens assembly, in order from an object side to an image side comprising: a front lens group, an aperture stop and a rear lens group; wherein the front lens group comprises, in order from the object side to the image side: a first lens element with negative refractive power having a concave image-side surface; a second lens element with negative refractive power; a third lens element with positive refractive power and a fourth lens element with positive refractive power; wherein the rear lens group comprises, in order from the object side to the image side: a fifth lens element with positive refractive power; and a sixth lens element with negative refractive power; wherein the fifth lens element and the sixth lens element are connected to form a doublet. By such arrangement, sufficient field of view is provided, and the aberration of the lens assembly is corrected for obtaining high image resolution.

Abstract: A lens system includes a first lens with negative refraction power, and a second lens with positive refraction power. The first lens includes a surface facing the image side having an optical portion. The lens system satisfies the formulas: (1) Y/Z<1.10;(2) G1R1/F1<?3.10; and (3) G2R2/F2>1.49, wherein Y is a distance between an end point of the optical portion and a center point of the optical portion along a direction perpendicular an optical axis, Z is a distance between the end point of the optical portion and the center point of the optical portion along the optical axis, F1 and F2 are the focal lengths of the first and second lenses, respectively, G1R1 and G2R2 respectively denote the radius of curvatures of a surface of the first lens facing the object side and another surface of the second lens facing the image side.

Abstract: There is provided super wide angle lens module, including: a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having positive refractive power; and a fifth lens having positive refractive power and having a meniscus shape convex toward an image side, wherein the third lens satisfies Equation 1, d3>1.7 ??Equation 1 where Nd3 represents a refractive index of the third lens.

Abstract: A wide angle photographic lens assembly comprises, in order from an object side to an 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 with positive refractive power having a concave object-side surface and a convex image-side surface, a third lens element, a fourth lens element with positive refractive power, a fifth lens element with negative refractive power, and a sixth lens element with positive refractive power. By adjusting the conditions among the above-mentioned lens elements, the wide angle photographic lens assembly can provide a wide-field of view and correct the aberration in order to obtain superior imaging quality.

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: An imaging lens includes a first lens and a third lens having negative refractive power, and a second lens and a fourth lens having positive refractive power. Curvature radiuses of surfaces of the first lens on an object side and an image plane side are positive. A curvature radius of a surface of the second lens on the object side is positive. Curvature radiuses of surfaces of the third lens on the object side and the image plane side are negative. Curvature radiuses of surfaces of the fourth lens on the object side and the image plane side are positive. The first lens has a focal length f1 and the second lens has a focal length f2, so that the following conditional expression is satisfied: ?0.6<f2/f1<?0.

Abstract: A projection lens system includes, in order from the magnified side to the reduced side thereof, a first lens group with negative refractive power, a second lens group with a positive refracting power, and a spatial light modulator. The projection lens system satisfies the following condition: 3.478<BFL/F<3.528. Wherein: BFL is a back focal length of the projection lens system; F is an effective focal length of the projection lens system.

Abstract: An image pickup optical system OP includes first and second prisms P1, P2 for bending incident light at an almost right angle. Optical axis AX at the incident surface of first prism P1 and optical axis AX at the outgoing surface of second prism P2 are almost parallel with each other. There is a lens element forming at least one power group on the optical path between first and second prisms P1, P2, wherein a power group closest to the incident surface of second prism P2 is a positive power group. The incident surface of second prism P2 has a concaved surface shape facing the object side, and the following conditional expressions are satisfied: ?4.2<fp2/f<?0.2 (fp2: a focal length of the second prism, f: is a focal length of the entire image pickup optical system), and 0.2<|f_1p/fp2|<1.5 (f_1p: a focal length of the power group closest to the incident surface of the second prism).

Abstract: A retrofocus wide-angle lens system is provided, wherein the entire the wide-angle lens system is divided at a position that satisfies the following condition (1) between a theoretical front lens group having a negative refractive power, and a theoretical rear lens group having a positive refractive power including the diaphragm, at a minimum focal length, and wherein a flat parallel plate is disposed at the position that satisfies the following condition (1): 1.2<|fF/f|<4.0 . . . (1), wherein fF designates the focal length of the theoretical front lens group having a negative refractive power, and f designates the focal length of the entire the wide-angle lens system.

Abstract: An objective optical system including an objective optical system having a field angle of 140° or larger and including a front group, an aperture stop, and a positive rear group arranged in that order from an object side. The front group has at least one aspherical surface and includes a negative first lens disposed closest to the object side and satisfying the following conditional expression: 0?r2/r1<0.24, 0.1<|g2/g1|<2.2 and ?1.8<f1/fl<?0.8, where r1 denotes the radius of curvature of the object side of the first lens, r2 denotes the radius of curvature of an image side of the first lens, g1 denotes the focal length of the front group, g2 denotes the focal length of the rear group, f1 denotes a focal length of the first lens, and fl denotes the focal length of the entire system.

Abstract: An imaging lens includes a first lens group having a first lens that directs a concave surface to an image plane side and is negative; a second lens group having a second lens that directs a concave surface to an object side and is positive; an aperture; a third lens group having a third lens that is positive; and a fourth lens group having a joined lens that is composed of a fourth lens that is positive and a fifth lens that is negative. In the configuration, when the whole lens system has a focal length f and a composite focal length of the first lens group to the third lens group is Fa, the imaging lens satisfies the following relation: 0.3<f/Fa<1.0.

Abstract: A fixed focus lens system includes a first lens group having a negative refractive power; and a second lens group having a positive refractive power, wherein the first lens group and the second lens group are sequentially arranged from an object side to an image side, and the second lens group includes two lenses having an Abbe's number of 80 or greater.

Abstract: An imaging lens includes a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power, which are disposed in order from an object. The first lens group has a first lens component having a negative refractive power and a second lens component having a positive refractive power, which are disposed in order from the object, and conditions expressed by the expressions 0.12<f/f1<0.47 and 0.016<D12/f<0.079 are satisfied, when f1 is a focal length of the first lens group, f is a focal length of the imaging lens, and D12 is an air distance between the first lens component and the second lens component of the first lens group.

Abstract: Provided are an imaging optical system in which chromatic aberrations are excellently corrected across the entire screen to realize high optical performance, and an optical apparatus including the imaging optical system. In an imaging optical system of which a back focus is longer than a focal length, a lens unit located in a reduction-conjugate side of an aperture stop includes at least one positive lens. A partial dispersion ratio and an Abbe number of the positive lens are set such that a refractive index, a position, and a power satisfy a suitable relationship.

Abstract: The present invention provides an image-capturing optical lens assembly comprising, in order from an object side to an image side, a front lens group, a stop, and a rear lens group. The front lens group 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; and a second lens element with positive refractive power having a convex object-side surface and a concave image-side surface. The rear lens group comprises, in order from the object side to the image side: a third lens element with positive refractive power having a convex object-side surface and a convex image-side surface; a fourth lens element with negative refractive power; and a fifth lens element with positive refractive power having a convex image-side surface.

Abstract: An image taking optical system, sequentially arranged from an object side to an image side along an optical axis comprising: a front lens group, a stop and a rear lens group. The front lens group comprises at least a meniscus front-group first lens element with a convex object-side surface. The rear lens group comprises at least three lens elements. Through the means of field adjustments that result in desirable distorted images, the image taking optical system may shorten the total length while enhancing the ability to create a larger field of view for panorama usages in compact cameras and mobile phones.

Abstract: A projection lens includes, in order from the magnification end to the minimization end thereof: a first lens group of a negative refractive power; and a second lens group of a positive refractive power. The projection lens satisfies the formula: 0.061<F/L<0.078; where F represents the effective focal length of the projection lens and L represent the total length of the projection lens.

Abstract: An optical lens includes a lens group and a diaphragm which is located in front of the lens group. The lens group includes three lenses, respectively the first, the second and the third lens, which are sequentially arranged as a “negative-positive-positive” separated focal power system. The first lens is a double concave negative lens, the second lens is a positive meniscus lens, and the third lens is a double convex positive lens. A concave surface of the second lens is towards the diaphragm, and the focal length of the entire optical system is f, the focal lengths of the first, the second and the third lens are respectively f1, f2, and f3, and which satisfies the following requirement: ?0.7<f1/f<?0.5; 1.0<f2/f<1.3; 0.8<f3/f<1.0.

Abstract: A photographic lens of a photographic apparatus which includes a plurality of lens groups may be manufactured using a method which includes correcting a focus deviation from a designed value generated in one lens group by adjusting a distance between lenses of another lens group. The distance between lenses may be adjusted using a washer. The lenses between which the distance is adjusted may include a positive lens and a negative lens, and the lens group having the lenses between which the distance is adjusted may have a negative refractive power.

Abstract: Provided is an imaging optical system and an image acquisition apparatus that can be suitably used in a small-diameter endoscope while having an ultra-wide angle of view. Provided is an image optical system (1) containing, in order from the object side, a negative front group (FG), an aperture stop (S), and a positive back group (BG), wherein the front group (FG) contains, in order from the object side, a negative first lens (L1) and a negative second lens (L2), and the back group (BG) contains a cemented lens (CL) constituted of at least three lenses (L5, L6, L7) joined together.

Abstract: A zoom lens disposed between an object side and an image side and including a first, second, third, and fourth lens group is provided. The first lens group has a negative refractive power and includes a first lens and a prism arranged in sequence from the object side to the image side. The first lens is an aspheric lens. A distance between the first lens and the prism is L, an effective focal length of the zoom lens at a wide-end is fw, and 1.58<L/fw<1.88. The second lens group disposed between the first lens group and the image side has a positive power and includes a first double cemented lens. The third lens group disposed between the second lens group and the image side has a negative power and includes a second double cemented lens. The fourth lens group has a positive power.

Abstract: A zoom lens includes in order from an object side to an image side and arranged along an optical axis thereof, a first lens unit having a negative refractive power, and a second lens unit having a positive refractive power. A distance between each lens unit changes when zooming from a wide-angle end to a telephoto end. The first lens unit includes a first lens sub-unit including a positive lens element and a negative lens element, and having a negative refractive power, and a second lens sub-unit including a single negative lens element. Focusing is performed by moving the second lens sub-unit in an optical axis direction, a focal length of the second lens sub-unit f1b and a focal length of the entire zoom lens fw at a wide-angle end are suitably set based on predetermined mathematical expressions.

Abstract: An imaging lens includes a first lens having negative refractive power; a second lens having negative refractive power; a third lens; a fourth lens; and a fifth lens. The first lens has a positive curvature radius on an image plane side. The second lens has a sharp convex surface, and a positive curvature radius on the image plane side. The third lens has a positive curvature radius on the object side and a negative curvature radius on the image plane side. The fourth lens has a negative curvature radius on the object side and a positive curvature radius on the image plane side. The fifth lens has a positive curvature radius on the object side and a negative curvature radius on the image plane side, and an aspheric surface.

Abstract: Provided is a simple-structured endoscope objective lens suitable for a compact, high-resolution image acquisition element. Provided is an objective lens constituted of a first negative lens, a second positive lens, an aperture stop, a third positive lens, and a joined lens arranged in that order from an object side, the joined lens being formed of a fourth positive lens and a fifth negative lens and satisfying the expressions (1) and (2), and the objective lens satisfies the expression (3): nn?2.0??(1) 12<(?p??n)<34??(2) 1.52<(f23/fl)<1.75??(3) where nn, ?p, ?n, f23 and fl denote a refractive index at d-line of the fifth lens, an Abbe number of the fourth lens, an Abbe number of the fifth lens, a combined focal length of the second lens and the third lens, and a focal length of the entire, respectively.

Abstract: An imaging lens includes negative first lens, negative second lens having a concave surface facing the image side, positive third lens, aperture stop, positive fourth lens, and fifth lens having a concave surface facing the object side, which are arranged sequentially from the object side. At least one of second lens, fourth lens and fifth lens has at least an aspheric surface. The Abbe number of third lens and the Abbe number of fifth lens are less than or equal to 30, and the Abbe number of fourth lens is greater than or equal to 40. Further, the following formula (1) is satisfied: 1.0<(R3?R4)/(R3+R4)??(1), where R3: the paraxial curvature radius of an object-side surface of second lens, and R4: the paraxial curvature radius of an image-side surface of second lens.

Abstract: The invention provides a superwide-angle imaging or projecting optical system provided that, albeit being a wide-angle optical system having an angle of view exceeding 180°, is of small size and reduced F-number and fast, and has improved f-? performance. The optical system consists only of transmitting surfaces, and has an angle of view of 180° or more. The optical system comprises a front group (Gf) comprising at least one meniscus lens (L1) having a negative focal length, an aperture (S), and a rear group (Gb) comprising at least two lenses having a positive focal length. At least one transmitting surface in the front group is made up of an extended rotation free-form surface.

Abstract: An optical system includes at least one lens unit having a negative refractive power disposed closer to an object side than an aperture portion. The lens unit having a negative refractive power includes at least one positive lens and one negative lens. The ratio between the numbers of positive lenses and negative lenses included in the lens unit having a negative refractive power is appropriately set. The lens unit having a negative refractive power includes a plurality of negative lenses each having an appropriate Abbe number and relative partial dispersion and a positive lens having an appropriate Abbe number. A negative lens having the highest dispersion among the negative lenses is located in an appropriate position.

Abstract: A lens system includes, in order from the subject side to the image side of thereof, a first lens group of negative refractive power, a second lends group of positive refractive power, and an image plane. The first lens group includes a first spherical lens, a second spherical lens, and a third spherical lens arranged in this order from the subject side to the image side of the lens system. The first spherical lens includes a first subject surface and a first image surface. The lens system satisfies the following formula: 8.9<D/F0<9.9, wherein, D is the distance between an apex point of the first subject surface and the image plane along the optical axis of the lens system, F0 is the effective focal length of the lens system.

Abstract: A super-wide-angle lens system for imaging an object on an imaging surface, includes a first lens group with negative refraction power and a second lens group with positive refraction power. The first lens group includes a first spherical lens with negative refraction power, a second spherical lens with negative refraction power, and a third spherical lens with positive refraction power. The first lens has a first surface facing the object side of the first lens group. The second lens group includes a fourth spherical lens with positive refraction power and a fifth spherical lens with negative refraction power. The system satisfies the formulas: 0.01<D/|FG1|<1, and 2<D/FG2<4, where D is the distance from the first surface to the imaging surface, FG1 is the effective focal length of the first lens group, and FG2 is the effective focal length of the second lens group.

Abstract: A wide viewing angle optical lens assembly comprises, in order from an object side to an 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 with positive refractive power having a convex object-side surface, a third lens element with positive refractive power having a convex image-side surface. By adjusting the relationship among the above-mentioned lens elements, the wide viewing angle optical lens assembly can effectively reduce its size, obtain greater angle of view as well as superior imaging quality.

Abstract: The present disclosure relates to a projection lens system for a projector having a spatial light modulator (SLM). The projection lens system includes, in order from the magnified end to the minified end thereof, a first lens group with negative refraction power, a second lens group with positive refraction power, and a third lens group with positive refraction power. The projection lens system satisfies the following formulas: 3<TT/f<3.6, and 0.48<BFL/f; wherein, TT is the overall length of the projection lens system; f is an effective focal length of the projection lens system; BFL is the back focal length of the projection lens system, the back focal length is equal to the distance between the third lens group and the SLM.

Abstract: This invention provides an optical photographing lens assembly comprising, in order from an object side to an image side: a first lens with negative refractive power having a concave image-side surface; a second lens with positive refractive power having a concave object-side surface and a convex image-side surface; a third lens with positive refractive power having a concave object-side surface and a convex image-side surface; a fourth lens with negative refractive power; and a fifth lens with positive refractive power; wherein the optical photographing lens assembly further comprises a stop disposed between the second and third lenses; and wherein the distance on the optical axis between the fourth and fifth lenses is T45, the focal length of the optical photographing lens assembly is f, the number of the lenses with refractive power is N, and they satisfy the relations: 0.10<(T45/f)*10<6.00, 5?N?6.

Abstract: A wide angle photographic lens assembly comprises, in order from an object side to an 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 with positive refractive power having a concave object-side surface and a convex image-side surface, a third lens element, a fourth lens element with positive refractive power, a fifth lens element with negative refractive power, and a sixth lens element with positive refractive power. By adjusting the conditions among the above-mentioned lens elements, the wide angle photographic lens assembly can provide a wide-field of view and correct the aberration in order to obtain superior imaging 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: An imaging lens system includes three lens groups having four lenses including a first lens, a second lens, a third lens, and a fourth lens arranged in order from an object side, and an aperture stop arranged between the first lens and the second lens. The second lens and the third lens are joined each other. The first lens is a negative meniscus lens having a convex surface at an object side. The second lens is a positive lens having a convex surface having a large curvature at an image side. The third lens is a negative lens having a concave surface having a large curvature at an object side. The fourth lens is a positive lens having a convex surface having a large curvature at an image side. The following conditions are satisfied: 1.4<|f1/F|<2.2 0.4<|f1/f23|<1.6 where F is a focal length of the entire imaging lens system, f1 is a focal length of the first lens, and f23 is a combined focal length of the second lens and the third lens which are joined each other.

Abstract: Provided is an optical system for a camera capable of realizing a wide view angle. The optical system for a camera includes a first lens having a negative refractive index and a convex meniscus shape with respect to an object; a second lens having a negative refractive index; a third lens having a positive refractive index and an object-side convex surface with respect to the object; and a fourth lens having a positive refractive index and an image-side convex surface with respect to an image surface, wherein the following Conditional Expression is satisfied: 0.5<v1/v2<1.2??[Conditional Expression 1] here, v1: an Abbe value of the first lens, and v2: an Abbe value of the second lens.

Abstract: A projection lens disposed between an enlarged side and a reduced side and including a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having positive refractive power, and an optical element disposed between the second and the third lens groups is provided. The first lens group includes a first and a second lens sequentially arranged from the enlarged side to the reduced side and respectively having a positive and a negative refractive power. The second lens group between the first lens group and the reduced side includes a third, a fourth, a fifth, and a sixth lens sequentially arranged from the enlarged side to the reduced side. The fifth and the sixth lens respectively have a positive refractive power. The third lens group disposed between the second lens group and the reduced side includes a seventh lens.

Abstract: The invention provides a high-performance objective lens that is capable of implementing focusing relative to an object point distance change with no or little angle-of-view change, and is well compatible with a high-pixel type imaging device. The objective optical system comprises, in order from an object side thereof, a first group of negative power, a second group of positive power, an aperture stop, and a third group of positive power. Only the second group moves thereby implementing focusing relative to an object point distance change, with satisfaction of the following conditions (1)-1, (1)-2 and (8): ?f>60??(1)-1 ?n>60??(1)-2 ?1.2<f1/ff<?0.6??(8) where ?f is a maximum half angle of view (°) upon viewing at a far distance object point, ?n is a maximum half angle of view (°) upon close-up viewing, f1 is a focal length of the first lens group, and ff is a focal length of the whole system upon viewing at a far distance. See FIG. 1.