Abstract: There is provided an imaging lens with high-resolution which satisfies demand of the wide field of view, the low-profileness and the low F-number, and excellently corrects aberrations.

Abstract: A wide-angle lens assembly includes a front lens group and a rear lens group. The front lens group includes a first lens having negative refractive power and a second lens having negative refractive power, wherein the first lens is a meniscus lens and the second lens includes a concave surface facing an image side. The rear lens group includes a third lens having positive refractive power, a fourth lens having positive refractive power, and a fifth lens having negative refractive power, wherein the fifth lens includes a concave surface facing an object side. The wide-angle lens assembly satisfies: 13.6 mm?fK?f1?25.2 mm; wherein fK is an effective focal length of a lens third close to the image side and f1 is an effective focal length of the first lens.

Abstract: Various lens designs for use in Time of Flight (ToF) sensor systems are discussed. Improvements to a ToF sensor system may be realized by, for example, incorporating a lens having particular features, such as a relatively short track length, fast lens speed (e.g., low f-number), low telecentricity, relatively flat field illumination, and fairly low cost. In some examples, such a lens of a ToF sensor system may be a lens assembly having a fixed focal length and that avoids use of lenses having aspheric surfaces so as to achieve relatively low cost.

Abstract: A six-piece optical lens system includes, in order from the object side to the image side: a stop, a first lens element with a positive refractive power, a second lens element with a negative refractive power, a third lens element with a refractive power, a fourth lens element with a negative refractive power, a fifth lens element with a positive refractive power, and a sixth lens element with a negative refractive power. Such arrangements can provide a miniaturized six-piece optical lens system having a big stop and high image quality.

Abstract: The present disclosure relates to the field of optical lenses and provides a camera optical lens. The camera optical lens includes, 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 camera optical lens satisfies following conditions: ?5.00?f1/f2??2.00; and ?20.00?(R1+R2)/(R1?R2)??2.00. The camera optical lens can achieve a high imaging optical imaging performance while obtaining a low TTL.

Abstract: An imaging lens system may include a first lens; a second lens; a third lens; a diaphragm; a fourth lens; a fifth lens; a sixth lens; and a seventh lens. The first lens may be a positive meniscus lens. The second lens may be a negative meniscus lens. The third lens may be a meniscus lens comprising. The fourth lens may be a positive lens. The fifth lens may be a positive lens. The sixth lens may be a negative lens comprising a sixth lens concave surface facing the image side. The seventh lens may be a positive lens comprising a seventh lens convex surface facing the object side. The fifth lens may be a glass lens. The second, third, fourth, sixth and seventh lenses may be plastic lenses. The sixth lens concave surface may be joined to the seventh lens convex surface with an adhesive.

Abstract: An optical imaging system includes a first lens group having a first group of lenses. A foremost lens of the first group of lenses is a lens closest to an object side and has a positive refractive power. The optical imaging system also includes a second lens group having a second group of lenses. A rearmost lens of the second group of lenses is a lens closest to an imaging plane and has convex surfaces. The first and second lens groups are sequentially disposed from the object side to an imaging plane. An expression TL/f1<2.0 is satisfied, where TL represents a distance from an object-side surface of the foremost lens to the imaging plane and f1 represents a focal length of the foremost lens.

Abstract: A wide-angle lens 100 includes a first lens 10, a second lens 20, a third lens 30, a diaphragm 72, a fourth lens 40, and a fifth lens 50. The first lens 10 is a negative meniscus lens whose lens surface on an image side Lb is a concave curved surface. The second lens 20 is a negative lens whose lens surface on the image side Lb is a concave curved surface and whose lens surface on the object side La is convex curved surface. The third lens 30 is a positive lens whose lens surface on the image side Lb is a convex curved surface. The fourth lens 40 is a negative lens whose lens surface on the image side Lb is a concave curved surface. The fifth lens 50 is a biconvex lens. A refractive index n1 of the first lens 10 satisfies a conditional expression.

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 positive refractive power, a third lens having a negative 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 plastic 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: An optical lens including, in order from an object side to an image side, a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, and a sixth lens having a positive refractive power, wherein the second lens has a concave object side surface.

Abstract: An optical imaging lens includes first, second, third, fourth, fifth and sixth lens elements arranged in order from the object side to the image side. The object-side surface of the fourth lens element has a convex portion in a vicinity of a periphery of the fourth lens element. The fifth lens element has negative refractive power. The effective focal length of the optical imaging lens EFL and the sum of all air gaps from the first lens element to the sixth lens element along the optical axis AAG of the optical imaging lens satisfies the relation: 0.9?EFL/AAG?2.6.

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 positive 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 glass material, the third lens is made of glass material, the fourth lens is made of plastic 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: An imaging apparatus includes a lens, a mask, and an image sensor. The mask includes a first aperture and a second aperture on which light passing through the lens is incident. The image sensor performs photoelectric conversion on first light that passes through the first aperture and second light that passes through the second aperture, the first light and the second light being irradiated on an optical detection surface of the image sensor.

Abstract: An optical system has, in order from an object: a first lens having negative refractive power; a second lens having positive refractive power; a third lens having positive refractive power; a fourth lens having negative refractive power; a fifth lens having negative refractive power; and a sixth lens having positive refractive power, wherein the following conditional expression (1) is satisfied: 1.52<L3R1/f3 - - - (1), where L3R1 denotes a radius of curvature of an object side lens surface of the third lens L3, and f3 denotes a focal length of the third lens L3.

Abstract: A lens module includes a first lens, a second lens, and a third lens comprising a convex object-side surface and a convex image-side surface. The lens module also includes a fourth lens including a concave object-side surface and a concave image-side surface, a fifth lens including a concave object-side surface, and a sixth lens including an inflection point formed on an image-side surface thereof. The first to sixth lenses are sequentially disposed from an object side to an image side.

Abstract: Disclosed are a high-performance imaging lens which has a comparatively wide angle and in which, in particular, distortion is satisfactory corrected, and an imaging apparatus including the imaging lens. The imaging lens consists of, in order from an object side, a first lens L1 having negative refractive power, a second lens L2 having negative refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5, and a sixth lens L6. One of the fifth lens L5 and the sixth lens L6 has positive refractive power, and the other lens has negative refractive power. The following conditional expressions (1) and (2) are satisfied. ?0.37<f?/f1<?0.13??(1) 1.8<t3/f?<3.

Abstract: An imaging optical system includes a positive or negative first lens group including a negative lens element closest to the object, a diaphragm, and a positive second lens group. The negative lens element closest to the object has an object-side aspherical surface including a paraxial convex surface, a paraxial curvature that is the greatest within the effective aperture, and a portion within the effective aperture having a curvature less than ½ of the paraxial curvature. These conditions are satisfied: R1/f<1.35 D1/f>0.4 ?2.5<f1/f<?1.3 V>56 “f” designates the overall focal length; f1, R1 and D1 respectively designate the focal length, paraxial radius of curvature of an object-side surface, and thickness, of the negative lens element closest to the object; and V designates the Abbe number regarding the d-line of a lens element, within the second lens group, closest to the diaphragm.

Abstract: A wide angle lens includes a first to a third lenses, a diaphragm, a fourth to a sixth lenses disposed in order from an object side. The fourth lens is a glass lens, and the second lens, the third lens, the fifth lens and the sixth lens are plastic lenses. The fifth lens and the sixth lens constitute a cemented lens. When a center curvature radius on an image side face of the fourth lens is “R42” and a focal length of an entire wide angle lens is “f0”, the center curvature radius “R42” and the focal length “f0” satisfy the conditional expression: 2×f0?|R42|?5×f0. When a center curvature radius on an object side face of the fourth lens is “R41”, the center curvature radii “R41” and “R42” may satisfy the conditional expression: |R41|?|R42|.

Abstract: An imaging lens is constituted by, in order from the object side to the image side: a negative first lens having a concave surface toward the image side; a positive second lens having a convex surface toward the image side; a negative third lens having a concave surface toward the image side; a positive biconvex fourth lens; a positive biconvex fifth lens; and a negative sixth lens having a concave surface toward the object side. Conditional Formula (1) related to the combined focal length f12 of the first lens and the second lens and the focal length f of the entire lens system is satisfied: ?5<f12/f<?2??(1).

Abstract: A wide angle six-piece lens includes a first lens having a negative refractive power and an image side as a concave surface, a second lens having a positive refractive power and an object side as a convex surface, an aperture, a third lens having a positive refractive power and an image side as a convex surface, a fourth lens having a positive refractive power and an object surface and an image surface as convex surfaces, a fifth lens having a negative refractive power and an object side as a concave surface, and a sixth lens having a positive refractive power and an object side as a convex surface. The overall effective focal length of the wide angle six-piece lens is f, the focal length of the third lens is f3, and an equation 0.29<f/f3<0.36 is satisfied. As such, a wide angle system is formed and aberration is eliminated.

Abstract: An imaging optical system includes a positive or negative first lens group including a negative lens element closest to the object, a diaphragm, and a positive second lens group. The negative lens element closest to the object has an object-side aspherical surface including a paraxial convex surface, a paraxial curvature that is the greatest within the effective aperture, and a portion within the effective aperture having a curvature less than ½ of the paraxial curvature. These conditions are satisfied: R1/f<1.35 D1/f>0.4 ?2.5<f1/f<?1.3 V>56 “f” designates the overall focal length; f1, R1 and D1 respectively designate the focal length, paraxial radius of curvature of an object-side surface, and thickness, of the negative lens element closest to the object; and V designates the Abbe number regarding the d-line of a lens element, within the second lens group, closest to the diaphragm.

Abstract: An optical imaging lens includes first, second, third, fourth, fifth and sixth lens elements arranged in order from the object side to the image side. The first lens element has an image-side surface with a concave part in a vicinity of its periphery, the second lens element has an image-side surface with a concave part in a vicinity of the optical axis, the third lens element has positive refractive power, the fourth lens element has an object-side surface with a convex part in a vicinity of its periphery, the fifth lens element has an object-side surface with a concave part in a vicinity of the optical axis, the sixth lens element has an image-side surface with a concave part in a vicinity of the optical axis. The second lens element has negative refractive power. The sixth lens element has positive refractive power.

Abstract: An optical system which forms an optical image on an image pickup element, comprising in order from an object side, a first lens unit having a positive refractive power, which includes a plurality of lenses, a stop, and a second lens unit which includes a plurality of lenses, wherein the first lens unit includes a first object-side lens which is disposed nearest to an object, and the second lens unit includes a second image-side lens which is disposed nearest to an image, and the first lens unit includes a negative lens, and a positive lens which is disposed on the object side of the negative lens, and the following conditional expressions are satisfied: ???1.1??(15) 0.08<NA??(16) 1.0<WD/BF??(19) 0.5<2×(WD×tan(sin?1NA)+Yobj)/?s<4.0.

Abstract: An imaging lens consists of a negative first lens, a positive second lens, a negative third lens, a positive fourth lens, a positive fifth lens, and a negative sixth lens in order from the object side. The Abbe number of the material of the sixth lens with respect to the d-line is less than or equal to 30. When the radius of curvature of the object side surface of the third lens is taken as R3F, the radius of curvature of the image side surface of the third lens is taken as R3R, and the Abbe number of the material of the third lens with respect to the d-line is taken as ?d3, the following conditional expressions are satisfied: 1.35<(R3F+R3R)/(R3F?R3R)<6.0??(1) ?d3<30.0??(2).

Abstract: A wide-angle lens assembly includes a first lens, a second lens, a third lens, a first stop, a fourth lens, a fifth lens and a sixth lens, all of which are arranged in sequence from an object side to an image side along an optical axis. The first lens is with negative refractive power. The second lens is with negative refractive power. The third lens is with positive refractive power. The fourth lens is with positive refractive power. The fifth lens is with negative refractive power. The sixth lens is with positive refractive power. The fifth lens satisfies 16.1?Vd5?23.9, wherein Vd5 is an Abbe number of the fifth lens.

Abstract: An imaging lens consists essentially of six lenses in the following order from the object side: a negative first lens; a positive second lens; a negative third lens; a positive fourth lens; a positive fifth lens; and a negative sixth lens. An aperture stop is disposed more toward the object side than the image-side surface of the fourth lens. Conditional expression (4) is satisfied, where f is the focal length of the entire system, and f56 is the combined focal length of the fifth lens and the sixth lens: f56/f<?6.4??(4).

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44 ??(1); and 38.1<?d3+?d5<45.1 ??(6).

Abstract: An imaging 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, a fourth lens element, a fifth lens element, and a sixth lens element. The first lens element with negative refractive power has an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof. The second lens element has an object-side surface being concave in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof. The third lens element has an object-side surface being convex in a paraxial region thereof. The fourth lens element has negative refractive power. The fifth lens element has positive refractive power. The sixth lens element has an image-side surface being concave in a paraxial region thereof.

Abstract: An imaging lens consists of negative first lens having a concave image-side surface, positive second lens, negative third lens, positive fourth lens, positive fifth lens having a convex image-side surface, and negative sixth lens, which are in this order from an object side. In the imaging lens, all of the lenses constituting the lens system are single lenses, which are not cemented lenses, and a stop is arranged closer to the object side than an image-side surface of the fourth lens is arranged. When a refractive index of a material of the third lens for d-line is Nd3, the following formula (1-1) is satisfied: Nd3<1.65??(1-1).

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44??(1); and 38.1<?d3+?d5<45.1??(6).

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44??(1); and 38.1<?d3+?d5<45.1??(6).

Abstract: A fixed-focus lens including a first lens group and a second lens group is provided. The first lens group having a negative refractive power includes a first lens, a second lens and a third lens arranged in sequence from an object side to an image side, in which refractive powers of the first, second and third lenses are negative, negative and positive in sequence. The second lens group having a positive refractive power is located between the first lens group and the image side, and the second lens group includes a fourth lens, a fifth lens and a sixth lens arranged in sequence from the object side to the image side, in which refractive powers of the fourth, fifth and sixth lenses are positive, negative and positive in sequence. The first, second, third, fourth, fifth and sixth lenses are separated from each other.

Abstract: An imaging lens substantially includes six lenses, constituted by: a first lens having a negative refractive power, which is of a meniscus shape having a concave surface toward an image side; a second lens; a third lens; a fourth lens; a fifth lens having a positive refractive power; and a sixth lens having a negative refractive power, a concave surface toward the image side, and at least one inflection point in the surface toward the image side; provided in this order from an object side. The imaging lens satisfies a predetermined conditional formula.

Abstract: An imaging lens substantially includes six lenses, constituted by: a first lens having a negative refractive power; a second lens having a positive refractive power; a third lens having a positive refractive power; a fourth lens having a negative refractive power; a fifth lens having a positive refractive power; and a sixth lens having a negative refractive power, a concave surface toward an image side, and at least one inflection point in the surface toward the image side; provided in this order from an object side. The imaging lens satisfies a predetermined conditional formula.

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. An object-side surface of the second lens has a shape having negative refractive power at a center, and including a part having positive refractive power in an area between the center and an effective diameter edge, and having negative refractive power at the effective diameter edge (concave shape facing the object side), and the refractive power at the effective diameter edge being weaker than the refractive power at the center. Further, an object-side surface of the third lens is convex toward the object side. Further, a predetermined conditional formula about a combined focal length of the first lens, the second lens and the third lens is satisfied.

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44??(1); and 38.1<?d3+?d5<45.1??(6).

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 image forming lens including an aperture stop, a first lens group, and a second lens group having a positive power, the first lens group including a first F lens group having a negative power and a first R lens group having a positive power, the first F lens group including at least two negative lenses, the first R lens group including at least one positive lens, the second lens group including a second F lens group having a positive power and a second R lens group, the second F lens group including a first positive lens, a first negative lens, a second negative lens, and a second positive lens, and the second R lens group including at least one lens.

Abstract: A monofocal photographing 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, a fourth lens element, a fifth lens element and a sixth lens element. The first lens element with negative refractive power has a concave image-side surface. The second lens element has refractive power. The third lens element has refractive power. The fourth lens element has refractive power. The fifth lens element has negative refractive power. The sixth lens element with positive refractive power has a convex image-side surface.

Abstract: A single focus lens system and a photographing apparatus including the single focus lens system are disclosed. A single focus lens system is provided that includes a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power, sequentially arranged in order from an object side, wherein the first lens group comprises first and second air lenses having a negative refractive power, a meniscus shape and a convex surface toward the object side, and the second lens group comprises a lens that has a positive refractive power, is disposed closest to the object side, and has a convex surface toward the object side.

Abstract: An imaging lens consists of negative first lens having a concave image-side surface, positive second lens, negative third lens, positive fourth lens, positive fifth lens having a convex image-side surface, and negative sixth lens, which are in this order from an object side. In the imaging lens, all of the lenses constituting the lens system are single lenses, which are not cemented lenses, and a stop is arranged closer to the object side than an image-side surface of the fourth lens is arranged. When a refractive index of a material of the third lens for d-line is Nd3, the following formula (1-1) is satisfied: Nd3<1.65??(1-1).

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: Provided is a zoom lens, including in order from a magnification conjugate side to a reduction conjugate side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; a third lens unit having a positive refractive power; a fourth lens unit having a negative refractive power; a fifth lens unit having a negative refractive power; and a sixth lens unit having a positive refractive power. The first and sixth lens units do not move for zooming, while the second to fifth lens units move to the magnification conjugate side during zooming from a wide-angle end to a telephoto end. Each of the second and third lens units is composed of a single positive lens. Movement amounts of the second, third and fourth lens units during zooming from the wide-angle end to the telephoto end satisfy appropriate relationships.

Abstract: An image forming lens including an aperture stop, a first lens group arranged on the object side relative to the aperture stop, and a second lens group having a positive power arranged on an image side relative to the aperture stop, the first lens group including a first F lens group having a negative power and a first R lens group having a positive power arranged in this sequence from the object side with the widest air space between the first F lens group and the first R lens group, the first F lens group including at least two negative lenses, the first R lens group including at least one positive lens, the second lens group including a second F lens group having a positive power and a second R lens group arranged in this sequence from the object side, the second F lens group including a first positive lens, a first negative lens, a second negative lens, and a second positive lens arranged in this sequence from the object side, and the second R lens group including at least one lens.

Abstract: An imaging lens includes a first lens that is a negative meniscus lens having a concave surface facing the image side of the imaging lens, a second lens that is a positive lens having a convex surface facing the object side of the imaging lens, a third lens that is a negative lens having a concave surface facing the image side, a fourth lens that is a double-convex lens, a fifth lens that is a negative meniscus lens having a concave surface facing the object side, and a sixth lens that is a negative lens, which are arranged in this order from the object side.

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: 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 is provided and includes, in order from the object side, a front group having a negative power, a stop, and a rear group having a positive power. The front group includes, in order from the object side, a first negative lens having a meniscus shape with a concave surface on an image side, a second negative lens, and a third positive lens. The rear group includes, in order from the object side, a fourth positive lens, a fifth negative lens having a meniscus shape with a concave surface on the object side, and a sixth positive lens. An Abbe number of each of the first lens, the second lens, the fourth lens, and the sixth lens at the d-line is equal to or larger than 40, and an Abbe number of each of the third lens and the fifth lens at the d-line is equal to or smaller than 40. Each lens constituting the front group and the rear group is a single lens.

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: A negative first lens having a concave surface facing the reduction side of a lens for projection, a positive second lens having a convex surface facing the magnification side of the lens for projection, a negative third lens having a concave surface facing the magnification side, a positive fourth lens having a convex surface facing the reduction side, a positive fifth lens, and a positive sixth lens are arranged in this order from the magnification side, and the reduction side of the optical system is telecentric. Further, the following formula (A) is satisfied: 1.2?Bf/f?2.5??(A), where Bf: back focus in air of the entire lens system of the lens for projection, and f: focal length of the entire lens system.