Abstract: The present disclosure discloses an optical lens assembly including a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens, which are arranged sequentially from an object side to an image side along an optical axis. The first lens has negative refractive power, an object-side surface thereof is convex, and an image-side surface thereof is concave. The second lens has negative refractive power, an object-side surface thereof is convex, and an image-side surface thereof is concave. The third lens has positive refractive power, and both of an object-side surface and an image-side surface thereof are convex. The fourth lens has refractive power. The fifth lens and the sixth lens are cemented to form a cemented lens. The seventh lens has positive refractive power, and both of an object-side surface and an image-side surface thereof are convex.

Abstract: An imaging optical system has an image circle defined on an imaging element. The imaging optical system includes: lens elements arranged from an object side to an image plane side, and a diaphragm arranged between two of the lens elements. The lens elements include freeform lens elements, each having a freeform surface that is an asymmetrical surface with respect to a long side direction and a short side direction which cross with each other with a first diameter of the image circle in the long side direction being larger than a second diameter of the image circle in the short side direction. At least two of the freeform lens elements are located on an object side of the diaphragm. The imaging optical system satisfies a condition based on a summation for freeform surfaces of freeform lens elements located on the object side of the diaphragm.

Abstract: A camera optical lens includes first to eighth lenses that are arranged sequentially from an object side to an image side. At least one of the first lens to the eighth lens has a free-form surface, and the camera optical lens satisfies: 1.30?f4/f?5.00; and 0?(R9+R10)/(R9?R10)?4.50, where f denotes a focal length of the camera optical lens, f4 denotes a focal length of the fourth lens, R9 denotes a curvature radius of an object-side surface of the fifth lens, and R10 denotes a curvature radius of an image-side surface of the fifth lens. The camera optical lens has a wide angle and is ultra-thin, as well as having excellent optical performance, and can effectively correct aberration and improve the performance of the optical system.

Abstract: The disclosure provides an optical imaging lens assembly, which sequentially includes from an object side to an image side along an optical axis: a first lens with a positive refractive power; a second lens with a refractive power; a third lens with a refractive power; a fourth lens with a refractive power; a fifth lens with a positive refractive power; a sixth lens with a negative refractive power; a seventh lens with a refractive power; an eighth lens with a positive refractive power; a ninth lens with a refractive power; and a tenth lens with a negative refractive power; wherein an effective focal length f of the optical imaging lens assembly and a maximum field of view FOV of the optical imaging lens assembly satisfy f×tan(½FOV)>6.0 mm.

Abstract: An imaging lens includes a first lens having positive refractive power; a second lens having negative refractive power; a third lens having negative refractive power; a fourth lens having positive refractive power; a fifth lens; a sixth lens; a seventh lens; an eighth lens; and a ninth lens having negative refractive power, arranged in this order from an object side to an image plane side. The ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape having an inflection point.

Abstract: An optical imaging lens, in order from an object side to an image side along an optical axis, includes a first lens assembly, an aperture, and a second lens assembly. The first lens assembly has negative refractive power and includes a first lens, a second lens, and a third lens. The first lens has negative refractive power. The second lens has negative refractive power. The third lens has positive refractive power. The second lens assembly has positive refractive power and includes a fourth lens, a fifth lens, and a sixth lens. The fourth lens has positive refractive power. The fifth lens has negative refractive power. The sixth lens has positive refractive power. In this way, the optical imaging lens of the present invention not only could achieve the effect of high image quality and low distortion, but also could reduce the volume of the optical imaging lens.

Abstract: An optical imaging system includes a first lens having an object-side surface that is convex; a second lens having a refractive power and a refractive index of 1.65 or more; a third lens having a refractive power; a fourth lens having a refractive power and an object-side surface that is convex; a fifth lens having a refractive power; a sixth lens having a positive refractive power; and a seventh lens having an object-side surface that is convex, wherein the first lens through the seventh lens are sequentially disposed in numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, and two or more of the first lens and the third lens through the seventh lens have a refractive index of 1.6 or more.

Abstract: Disclosed is a camera optical lens, including nine lenses, and the nine lenses from an object side to an image side are: a first lens with a negative refractive power, a second lens with a positive refractive power, a third lens with a negative refractive power, a fourth lens with a positive refractive power, a fifth lens with a negative refractive power, a sixth lens with a positive refractive power, a seventh lens with a negative refractive power, an eighth lens with a positive refractive power and an ninth lens with a negative refractive power. The camera optical lens satisfies: ?5.50?f1/f??2.00; 3.00?d11/d12?12.00. The camera optical lens has good optical performance, and meets the design requirements of a large aperture, wide-angle and ultra-thin.

Abstract: An objective lens for an endoscope includes only four lens groups as lens groups, and the four lens groups consist of a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group that are arranged in this order from an object side. The first lens group is fixed and the second and third lens groups are moved during focusing on an object positioned at the nearest point from an object positioned at the farthest point. The objective lens for an endoscope satisfies a predetermined conditional expression related to a focal length of an entire system and a focal length of the third lens group.

Abstract: A zoom lens includes a first lens group with a negative refractive power, a second lens group with a positive refractive power, and an aperture stop disposed in and movable with the second lens group. Each of the first lens group and the second lens group moves individually. The zoom lens further includes a doublet lens disposed on a first side of the aperture stop and between the first lens group and the aperture stop, and at most two lenses including at least one aspheric lens are disposed on a second side of the aperture stop.

Abstract: An observation imaging apparatus includes an insertion unit, an imaging lens, and an image sensor. The imaging lens is disposed in such a manner that an axial principal ray of an observation subject side surface of a lens is tilted with respect to a normal line passing through the center of gravity of a section of the insertion unit, the section passing through the center of an effective imaging range of the image sensor and having the smallest area. A point on the axial principal ray at which the distance between the normal line and the axial principal ray is smallest is located on the image side relative to the observation subject side surface of the lens and on the observation subject side relative to the image sensor. The observation imaging apparatus satisfies a predetermined conditional expression.

Abstract: An imaging device includes a free-form lens having a shape in which (i) in a long-side direction of an imaging element, a resolution that changes along an optical axis long-side resolution curve, and the resolution that changes along a distant point long-side resolution curve in a position away from an optical axis, (ii) in a short-side direction, the resolution that changes along an optical axis short-side resolution curve, and the resolution that changes along a distant point short-side resolution curve in the position away from the optical axis, (iii) the distant point long-side resolution curve follows a shape of the optical axis long-side resolution curve, and has a higher resolution than the optical axis long-side resolution curve, and (iv) the distant point short-side resolution curve follows a shape of the optical axis short-side resolution curve, and has a higher resolution than the optical axis short-side resolution curve.

Abstract: An objective optical system consists of, in order from an object side, a first lens group having a negative refractive power, which is stationary all the time, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power, which is stationary all the time. At a time of focusing from an object point at a long distance to an object point at a short distance, the second lens group moves toward the object side and the third lens group moves toward an image side. The following conditional expressions (1), (5), and (7) are satisfied: 2<fG2/f<8??(1) 0.2<(t34f?t34n)/f<0.5??(5) ?8<fG1/f<?2??(7).

Abstract: An optical image capturing lenses includes, 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 includes, in order from the object side to the image side, at least a first lens element and a second lens element. The first lens element has a convex object-side surface and a concave image-side surface. The rear lens group includes, in order from the object side to the image side, at least a third lens element, a fourth lens element, a fifth lens element, and a sixth lens element. The sixth lens element is made of plastic material. The object-side surface and the image-side surface of the sixth lens are aspheric. The sixth 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 imaging optical system including a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; an aperture stop; a fourth lens having positive refractive power; a fifth lens having negative refractive power; and a six lens arranged in that order from an object side. The first lens is a negative lens with a concave surface facing the image side. The second lens is a negative lens with a concave surface facing the object side. The second lens and the third lens are joined together to form a cemented lens have positive refractive power.

Abstract: An optical lens includes two lens groups and an aperture stop. A total number of lenses with refractive power of the two lens groups is larger than three, and the two lens groups includes an aspheric lens with negative refractive power. The aperture stop is disposed between the two lens groups. The optical lens satisfies the following condition: 0.05>[y(?)?(EFL*sin ?)]/(EFL*sin ?)>?0.3, where ? denotes a half field of view, y(?) denotes an image height of an image plane for visible light with respect to the half field of view ?, and EFL denotes an effective focal length for visible light of the optical lens.

Abstract: An optical system includes a first lens having negative refractive power and having two concave surfaces, a second lens having positive refractive power, a third lens having refractive power, a fourth lens having refractive power, a fifth lens having refractive power, a sixth lens having refractive power, and a seventh lens having refractive power. The first to seventh lenses are sequentially disposed from an object side. Whereby an aberration improvement effect may be increased and high resolution and a wide angle may be implemented.

Abstract: The present disclosure discloses a camera optical lens. The camera optical lens including, in an order from an object side to an image side, a first lens, a second lens having a negative refractive power, a third lens having a positive refractive power, a fourth lens, a fifth lens and a sixth lens. The first lens is made of plastic material, the second lens is made of plastic material, the third lens is made of glass material, the fourth lens is made of glass material, the fifth lens is made of plastic material, and the sixth lens is made of plastic material. The camera optical lens further satisfies specific conditions.

Abstract: Disclosed herein is a light field camera, where both a curved shape of a curved microlens array and a curved shape of a curved image sensor are the same as a curved shape of a wide-angle main lens, and a sum of a reciprocal of a vertical distance between the curved microlens array and the curved image sensor and a reciprocal of a vertical distance between the curved microlens array and a virtual image plane of the wide-angle main lens is equal to a reciprocal of a focal length of the curved microlens array, which resolves a problem of poor image quality such as blurring and distortion that is caused when a wide-angle main lens is used in a light field camera and a flat microlens array and a flat image sensor cannot match a curved virtual image plane of the wide-angle main lens.

Abstract: A zoom lens includes, in order from an object side to an image side, 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, a fourth lens unit having a negative refractive power, and a rear unit including at least one lens unit. In the zoom lens, the locus of movement, the focal length, the amount of displacement during zooming, and the shapes of lens surfaces are appropriately set for each lens unit.

Abstract: An embodiment of this disclosure provides an optical lens, which includes, in order from an object side to an image-forming side, a first lens with negative refraction power; a second lens with negative refraction power; a third lens with positive refraction power; a fourth lens with positive refraction power; and a fifth lens with negative refraction power; wherein the second lens has an Abbe number vd2, the fifth lens has a refractive index nd5, and 20?vd2?30 and nd5?1.9.

Abstract: A lens system includes: a plurality of aligned lenses; a first lens having negative refractive power; a second lens having negative refractive power; a third lens with positive refractive power; and, a fourth lens with positive refractive power; a light beam transmitted through the first, second, third and fourth lenses is first diverged by the first and second lenses, collimated by the third lens and focused by the fourth lens to form a small spot at the focal plane.

Abstract: An imaging lens includes, in order from the object side to the image side, a positive first lens group, a stop, a positive second lens group, and a positive third lens group. The first lens group includes, consecutively in order from the most object side thereof, a negative lens and a positive lens. The second lens group is of a three lens configuration and includes a positive lens and a negative lens. The third lens group includes, consecutively in order from the most object side thereof, a negative lens and a positive lens. The imaging lens satisfies Conditional Formula (1): 0<f1/f2<2, which is related to the focal length f1 of the first lens group and the focal length f2 of the second lens group.

Abstract: An image capturing optical lens assembly includes, in order from an object side to an image side, a front lens group, an aperture stop and a rear lens group. The front lens group includes at least two lens elements, wherein one lens element closest to an imaged object of the at least two lens elements has negative refractive power and an image-side surface being concave. The rear lens group includes at least four lens elements, wherein one lens element closest to an image surface of the at least four lens elements has an image-side surface being concave. The image capturing optical lens assembly has a total of eight lens elements.

Abstract: An imaging optical system includes, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power, the first lens unit includes a first negative lens and a first cemented lens, the second lens unit G2 includes a second cemented lens, one or more positive lens components, and a third cemented lens, and the first cemented lens includes a negative lens and has a surface having a concave surface facing toward the reduction side, the second cemented lens has a positive refractive power and has a surface having a concave surface facing toward the enlargement side, and the third cemented lens has a positive refractive power and includes a negative lens on the reduction side.

Abstract: A miniature image pickup lens includes a first lens, a second lens, an aperture, a third lens, a fourth lens, and a fifth lens arranged in sequence along an optical axis from an object side to an image side. The first lens is a negative meniscus lens with a convex surface towards the object side and a concave surface towards the image side. The second lens is a positive lens with a convex surface towards the object side. The third lens is a positive biconvex lens, and the fourth lens is a negative biconcave lens. The fifth lens has a convex surface towards the object side.

Abstract: An objective lens including a first lens group immovable in changing magnification from a normal observation state to a close-up observation state, a second lens group arranged nearer to the image side than the first lens group and moving along the optical axis in the change of magnification, a third lens group arranged nearer to the image side than the second lens group and immovable in the change of magnification, and an aperture stop arranged between the second lens group and an image plane and immovable in the change of magnification, and the objective lens satisfying the following condition: 1.24<|F1f/Fn|<1.8 where F1f denotes the focal length of a lens that is placed nearest to the object side in the first lens group and Fn denotes the focal length of the whole system in the normal observation state.

Abstract: An image-capturing optical system includes: a positive first lens group; and a positive second lens group, wherein the positive first lens group and the positive second lens group are arranged in order from an object side in the image-capturing optical system, the image-capturing optical system focuses on a close object by moving the second lens group as a whole along a light axis toward the object side, a lens closest to the object side in the second lens group has a convex surface facing the object side, a lens closest to an image side in the second lens group is a positive meniscus lens having a convex surface facing the image side, the image-capturing optical system satisfies following condition expressions (1) to (3) 2.2<1Gr_Fl/FL<3.8??(1) 0.9<2Gr_Fl/FL<1.5??(2), and 0.45<1Gr_R_nop/1Gr_Thi<0.85??(3).

Abstract: An imaging lens consists of, in order from the object side, a front group having a negative refractive power, a stop, and a rear group having a positive refractive power. The front group consist of a front-group negative lens group that consists of three negative lenses and has a negative refractive power, and a front-group positive lens group that includes one positive lens and one negative lens and has a positive refractive power, where the negative lens is disposed at the most image-side position. The rear group includes two positive lenses and two negative lenses. The imaging lens satisfies condition expression (1): 0.95<?fAn/f<2, where fAn is a focal length of the front-group negative lens group, and f is a focal length of the entire system.

Abstract: A lens assembly includes a first lens group, a stop and a second lens group, all of which are arranged in sequence from an object side to an image side along an optical axis. The first lens group includes a first lens and a second lens, wherein the first lens is with negative refractive power and the second lens is with positive refractive power. The second lens group includes a third lens, a fourth lens, a fifth lens and a sixth lens, wherein the third lens and the fifth lens are with negative refractive power, and the fourth lens and the sixth lens are with positive refractive power. The lens assembly satisfies 0.23?f/TL?0.45, wherein f is an effective focal length of the lens assembly and TL is a distance from an object side surface of the first lens to an image plane along the optical axis.

Abstract: A wide-angle lens is disclosed. The wide-angle lens includes a first lens element L1, a second lens element L2, a third lens element L3, an aperture diaphragm S, a fourth lens element L4 and a fifth lens element L5 arranged from an object plane to an image plane. The first element L1 is a meniscus lens element having a negative focal power and protruding toward the object plane, the second element L2 is a meniscus lens element having a negative focal power and protruding toward the object plane, the third element L3 is a meniscus lens element having a positive focal power and protruding toward the image plane, the fourth element L4 is a meniscus lens element having a negative focal power and protruding toward the object plane, and the fifth element L5 is a lens element having a positive focal power.

Abstract: An imaging lens, consisting of a first lens group, a top, and a second lens group having a positive refractive power, in order from the object side, in which the first lens group is composed of a first front lens group having a negative refractive power and a first rear lens group having a positive refractive power in order from the object side, the first rear lens group is composed of a cemented lens formed of a negative lens and a positive lens, the first front lens group at least includes four negative lenses, and at least two of the negative lenses included in the first front lens group satisfy a conditional expression given below: 70<?d1n??(1).

Abstract: An imaging lens includes: a first lens group; a stop; a positive second lens group; and a negative third lens group which is fixed while focusing, in order from the object side. The first lens group includes at least one positive lens, at least one cemented lens, and a negative meniscus lens having a concave surface toward the image side, in order from the object side. The second lens group includes a cemented lens formed by a biconcave lens and a biconvex lens and a biconvex lens, in order from the object side. The third lens group includes a negative meniscus lens having a convex surface toward the object side, a biconcave lens, and a biconvex lens, in order from the object side. The first lens group, the stop, and the second lens group move integrally along the optical axis to focus from an infinite to a finite distance.

Abstract: A wide angle lens includes a first lens group having negative refractive power, as a whole, a second lens group having positive refractive power, as a whole, and a third lens group having positive refractive power, as a whole, in this order from an object side. The first lens group includes a positive meniscus lens with its convex surface facing the object side and three negative meniscus lenses, each with its convex surface facing the object side, in this order from the object side. The second lens group includes at least one cemented lens. The material of at least one of the three negative meniscus lenses in the first lens group satisfies the following conditional expression (1), and the material of at least one of the other negative meniscus lenses in the first lens group satisfies the following conditional expressions (2) and (3): ?da>81??(1); ?db<25??(2); and ??gFb>0.015??(3).

Abstract: A single focal length lens system comprising at least a positive first lens unit and a second lens unit, wherein the first lens unit includes a first sub lens unit E which successively comprises a negative lens element A, a positive lens element B, a negative lens element C and a positive lens element D, a second sub lens unit comprising at least one lens element is a focusing lens unit in the second lens unit, and the conditions: 1.0<|fW/fA|<2.2, 0.5<fW/fB<2.0, 0.5<|fW/fC|<1.7, and 0.5<fW/fD<1.8 (fW: focal length of the lens system, fA: focal length of the lens element A, fB: focal length of the lens element B, fC: focal length of the lens element C, fD: focal length of the lens element D) are satisfied.

Abstract: A wide angle lens consists of a first lens group having negative refractive power as a whole, a second lens group having positive refractive power as a whole, and a third lens group having positive refractive power as a whole in this order from an object side. The first lens group consists of a positive meniscus lens with its convex surface facing the object side and three negative meniscus lenses, each with its convex surface facing the object side, in this order from the object side. The second lens group includes at least two cemented lenses. The third lens group consists of a 3a-th lens group consisting of a positive meniscus lens with its convex surface facing the object side and a 3b-th lens group that includes at least two cemented lenses and has positive refractive power as a whole, in this order from the object side.

Abstract: A fish eye lens system and a photographing apparatus including the same, the fish eye lens system including, in an order from an object side to an image side: a first lens group having a negative refractive power; an aperture stop; and a second lens group having a positive refractive power, wherein the first lens group includes, in the order from the object side to the image side, a (1-A)-th lens group having a negative refractive power, a (1-B)-th lens group having a negative refractive power, and a (1-C)-th lens group including at least one positive lens, and wherein the (1-B)-th lens group is moved to perform focusing.

Abstract: In an optical system including, in order from an object side to an image side: a front unit (LF) having a negative refractive power; an aperture stop; and a rear unit (LR) having a positive refractive power, the front unit (LF) includes a meniscus-shaped negative lens (g1) closest to the object side, and a focal length (fw) of the entire optical system, a focal length (fg1) of the meniscus-shaped negative lens (g1), and a curvature radius (R2) of a lens surface on the image side of the meniscus-shaped negative lens (g1) are appropriately set.

Abstract: An imaging lens includes negative first lens, negative second lens, third lens of a plano-convex shape having a convex surface directed toward an object side or of a positive meniscus shape having a convex surface directed toward the object side, and a fourth lens of a plano-convex shape having a convex surface directed toward an image side or of a positive meniscus shape having a convex surface directed toward the image side, which are arranged in this order from the object side. Further, the following conditional formula (6) is satisfied: 0.75?(R8?R9)/(R8+R9)?1.0??(6), where R8: a curvature radius of an object-side surface of the fourth lens, and R9: a curvature radius of an image-side surface of the fourth lens.

Abstract: An imaging lens consists of a negative first lens, a negative second lens, a third lens of a plano-convex shape having a convex surface directed toward an object side or of a positive meniscus shape having a convex surface directed toward the object side, and a fourth lens of a plano-convex shape having a convex surface directed toward an image side or of a positive meniscus shape having a convex surface directed toward the image side, which are arranged in this order from the object side. Further, the following conditional formula (1) is satisfied: 2.25<?d2/?d3??(1), where ?d2: an Abbe number of a material of the second lens for d-line, and ?d3: an Abbe number of a material of the third lens for d-line.

Abstract: An imaging lens consists of a first lens group, a second lens group, an aperture stop and a third lens group that has positive refractive power in this order from an object side. The first lens group consists of an L11 lens having positive refractive power, an L12 lens having negative refractive power, an L13 meniscus lens having negative refractive power with its concave surface facing an image side, an L14 lens having negative refractive power with its concave surface facing the object side and two or three lenses, each having positive refractive power, in this order from the object side. The second lens group consists of an L2p lens having positive refractive power and an L2n lens having negative refractive power.

Abstract: A wide angle lens includes a first lens group having negative refractive power, as a whole, a second lens group having positive refractive power, as a whole, and a third lens group having positive refractive power, as a whole, in this order from an object side. The first lens group includes a positive meniscus lens with its convex surface facing the object side and three negative meniscus lenses, each with its convex surface facing the object side, in this order from the object side. The second lens group includes at least one cemented lens. The material of at least one of the three negative meniscus lenses in the first lens group satisfies the following conditional expression (1), and the material of at least one of the other negative meniscus lenses in the first lens group satisfies the following conditional expressions (2) and (3): ?da>81??(1); ?db<25??(2); and ??gFb>0.015??(3).

Abstract: A wide angle lens consists of a first lens group having negative refractive power as a whole, a second lens group having positive refractive power as a whole, and a third lens group having positive refractive power as a whole in this order from an object side. The first lens group consists of a positive meniscus lens with its convex surface facing the object side and three negative meniscus lenses, each with its convex surface facing the object side, in this order from the object side. The second lens group includes at least two cemented lenses. The third lens group consists of a 3a-th lens group consisting of a positive meniscus lens with its convex surface facing the object side and a 3b-th lens group that includes at least two cemented lenses and has positive refractive power as a whole, in this order from the object side.

Abstract: An imaging lens formed of 4 lenses, in which a negative first lens having a meniscus shape with a convex surface on the object side, a biconvex positive second lens, a negative third lens having a concave surface on the image side, and a positive fourth lens having a convex surface on the object side, arranged in order from the object side, and the imaging lens satisfies conditional expressions (1): L12/f<0.82; (2): 2.3<L12×R2F2/f2<10.0; (5): ?1.3<f1/f<?0.9; and (6): 48<v1 simultaneously, where, L12 is the air equivalent distance between the first lens and the second lens, f is the focal length of the entire lens system, R2F is the radius of curvature of the object side lens surface of the second lens, f1 is the focal length of the first lens, and v1 is the Abbe number of the first lens with respect to the d-line.

Abstract: An optical system includes, in order from object side: a positive first lens unit; and a positive second lens unit moving during focusing. The second lens unit includes, in order from object side, a front unit, an aperture stop, and a positive rear unit. The first unit includes a negative lens that has a convex surface facing object side and is arranged closest to object side, and three or more positive lenses on image side of the negative lens. A distance, on optical axis, from a lens surface on object side of a second positive lens counted from image side of the three or more positive lenses to a lens surface closest to image side of the first unit, and a distance, on optical axis, between a lens surface closest to object side and that closest to image side of the first unit are each appropriately set.

Abstract: Provided is an optical system having, in order from an Object, a first lens group (G1) having negative refractive power and a second lens group (G2), wherein the first lens group (G1) includes, in order from the object, a first negative lens (L11) and a second negative lens (L12) having a concave surface facing the object, and the following conditional expression (1) is satisfied: 7.94?(?fn12)/f<48.00??(1) where fn12 denotes a focal length of the second negative lens (L12), and f denotes a focal length of the entire optical system.

Abstract: An imaging lens includes a negative first lens, a negative second lens, a third lens of a plano-convex shape having a convex surface directed toward an object side or of a positive meniscus shape having a convex surface directed toward the object side, and a fourth lens of a plano-convex shape having a convex surface directed toward an image side or of a positive meniscus shape having a convex surface directed toward the image side, which are arranged in this order from the object side. Further, the following conditional formula (4) is satisfied: 1.0<D2/f<2.5??(4), where f: a focal length of an entire system, and D2: a distance on an optical axis between the first lens and the second lens.

Abstract: To allow placement of optical members by providing a long back focus, make aberrations less subject to manufacturing errors, and reduce variations in aberrations during focusing. An endoscopic objective optical system includes, in order from an object side, a front group with negative refractive power, a focusing lens, and a rear group with positive refractive power, wherein: the endoscopic objective optical system satisfies conditional expressions (1) to (4) below: 4<FB/FL??(1) FL/|Fc|<0.1??(2) ?3<F—F/FL<?0.9??(3) 2.5<F—R/FL<5??(4) where FB is back focus of the entire system, FL is a focal length of the entire system, fc is a focal length of the focusing lens, |fc| is an absolute value of fc, F_F is a focal length of the front group, and F_R is a focal length of the rear group.

Abstract: An objective lens for an endoscope performs focusing from a farthest point object to a nearest point object by moving, along optical axis Z, at least one lens group excluding a most object-side lens group. The following conditional formulas (1) and (2) are satisfied: 1.2?ft/fw??(1); and 0.0<(fm?fw)/(ft?fw)?0.5??(2), where ft: a focal length of an entire system when the objective lens has been focused on the nearest point object, fw: a focal length of the entire system when the objective lens has been focused on the farthest point object, dt: an object distance to the nearest point object, dw: an object distance to the farthest point object, dm, which is represented by dm=(2×dw×dt)/(dw+dt): an object distance to a middle point object, and fm: a focal length of the entire system when the objective lens has been focused on the middle point object.

Abstract: An imaging lens assembly comprises a fixing diaphragm and an optical set including five lenses. An arranging order from an object side to an image side is: a first lens; a second lens; a third lens having a lens with a positive refractive power defined near the optical axis and a convex surface directed toward the image side; a fourth lens having a lens with a positive refractive power defined near the optical axis and a convex surface directed toward the image side; and a fifth lens having a concave surface with a corrugated contour directed toward the image side and disposed near the optical axis. At least one surface of the five lenses is aspheric. By the concatenation between the lenses and the adapted curvature radius, thickness, interval, refractivity, and Abbe numbers, the assembly attains a big diaphragm with ultra-wide-angle, a shorter height, and a better optical aberration.