Abstract: A projection zoom lens that is suited to projector with a DMD is provided. The projection zoom lens projects, onto a screen, projection light from the DMD and comprises, in order from a screen side, a first lens group with negative refractive power and a second lens group with positive refractive power. The second lens group includes, from the DMD side, a final lens that is a positive lens, a pre-final lens that is a negative biconcave lens positioned next to the final lens, and a stop, and both surfaces of the pre-final lens are aspherical. Using the projection zoom lens, it is possible to realize the compact projector that can project bright images with high resolution that makes full use of the characteristics of the DMD.

Abstract: A projection lens system that is suited to a compact, wide-angle lens system. The projection lens system projects projection light from a light modulator onto a screen, wherein the projection lens system is constructed, in order from a screen side thereof, of a first lens group with negative refractive power and a second lens group with positive refractive power and is non-telecentric on an incident side thereof, and the second lens group includes a pair of cemented doublet lenses with positive refractive power whose cemented surfaces face in opposite directions and a cemented triplet lens with positive refractive power.

Abstract: A zoom lens system for forming an optical image of a subject on the image-sensing surface of an image sensor has three lens units, namely, from the object side thereof, a first lens unit having a negative optical power, a second lens unit having a positive optical power, and a third lens unit having a positive optical power. The lens units each include at least one plastic lens element. The zoom lens system as a whole includes at least one glass lens element that fulfills a prescribed conditional formula.

Abstract: The present invention is directed to provide a telecentric zoom lens capable of attaining a small numerical aperture, a wide angle of view, reduced distortion, high resolution, reduced chromatic aberration, small aperture, and yet avoiding a cost increase and also to provide the telecentric zoom lens that shows a unified imaging ability relative to a varied distance to the screen and has a minimum projection distance to the screen got shorter. The telecentric zoom lens is comprised of a first group of lenses negative in power, a second group of lenses positive in power, and a third group of lenses positive in power, and a focal length fw at a wide angle of view can be given in relation with focal lengths f1, f2 and f3 of the first, second and third groups of lenses respectively, as follows: 2.5?|f1/fw|?1.5, 4?f2/fw?2.5, and 13?f3/fw?3.

Abstract: Disclosed is a zoom lens having a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power arranged in the mentioned order from an object side, wherein the first lens group includes a negative lens and a positive lens having at least one aspherical surface arranged in the mentioned order from the object side and satisfies a following inequality (1): 0.4<D1/fw<0.66 ??(1) where D1 represents a distance, inside the first lens group, between a lens surface closest to an object and a lens surface closest to an image, and fw represents a focal distance with the zoom lens set to a wide-angle position.

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

Abstract: A zoom lens system that includes lens groups G1 to G5 that have negative, positive, positive, negative and positive refractive power respectively in the order from a screen side is provided. The fourth lens group G4 includes a cemented lens made up of a negative lens that is concave on the screen side and a convex lens. The zoom lens system satisfies conditions below 1.15<f2/fw<2.0 50<?vd4<70 where fw is a combined focal length of the zoom lens system at a wide-angle end, f2 is a combined focal length of the second lens group, and ?vd4 is a difference in the respective Abbe numbers vd of lenses composing the cemented lens in the fourth lens group G4.

Abstract: A zoom lens system comprises, successively from the object side, a first negative lens group and a positive second lens group. The first lens group includes a negative meniscus lens and a positive meniscus lens, the negative meniscus lens and the positive meniscus lens each has at least one aspherical surface. The second lens group includes a first positive auxiliary group and a positive second auxiliary group. The refractive power of the first group is 1/f1, the refractive power of the second group is 1/f2, the focal length of the whole lens system fw when the distance between the lens groups is increased, fT is the focal length of the whole lens system when the distance between the lens groups is decreased, and they satisfy the following conditional expressions of: 0.9?|f1|/(fw·fT)1/2?1.1 and 1.15?|f1|/f2?1.35.

Abstract: An object is to provide an ultra-compact zoom lens system suitable for a video camera and a electronic still camera using a solid-state imaging device and the like with securing high optical performance. The zoom lens system includes, in order from an object along the optical axis, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and at least one lens group having positive refractive power. The first lens group is fixed upon zooming from a wide-angle end state to an telephoto end state and focusing. A plurality of lens groups except the first lens group are moved upon zooming from the wide-angle end state to the telephoto end state, respectively. A plurality of lens groups except the first lens group G1 are moved upon focusing, respectively. Given conditional expressions are satisfied.

Abstract: Among a plurality of lens units constituting an optical system, at least one of the plurality of lens units includes a refractive optical element made of a solid material that satisfies the following conditions: 3<?d<30 0.10<?gd<1.25 0.10<?gF<0.60 where ?d is an Abbe number of the solid material and ?gd and ?gF represent partial dispersion ratios of the solid material. The refractive optical element made of the solid material has refractive power with a sign opposite to a sign of refractive power of the lens unit including the refractive optical element.

Abstract: A zoom lens system for forming an optical image of a subject on the image-sensing surface of an image sensor includes at least, from the object side thereof, a first lens unit having a negative optical power and a second lens unit having a positive optical power, and achieves zooming by varying the distances between the individual lens units in such a way that, during zooming from the wide-angle end to the telephoto end, the distance between the first and second lens units decreases. The first lens unit consists of two plastic lens elements.

Abstract: The invention relates to an electronic image pickup system that enables a wide image-pickup, and ensures that even when an image is printed, sufficient image quality and clearness are obtained from the center to as far as the margin of the image and the image of a subject is depicted with a sense of extension. The electronic image pickup system comprises an image-formation optical system 10 for forming an image of a subject and an electronic image pickup device 20 located on an image side of the image-formation optical system for obtaining image information on the image.

Abstract: A miniature zoom lens has, sequentially from an object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power and including a diaphragm, and a third lens group G3 having positive refractive power. The first lens group G1 is formed from a single negative lens L1. The second lens group G2 is formed from, sequentially from the object side, a single positive lens L2 and a single negative lens L3. The third lens group G3 is formed form a single positive lens L4. The first lens group G1 is immovable and the second lens group G2 and the third lens group G3 move in an optical axis direction at variable power. The miniature zoom lens provides a large zoom ratio while keeping a constant total length.

Abstract: A varifocal zoom lens includes: a first lens group having a negative refractive power; a second lens group having a positive refractive power, including a cemented lens component L21 formed by combining a positive lens having a convex surface on the object side and a negative lens having a concave surface on an image side and a positive lens component L22 disposed on the image side with respect to the cemented lens component L21, spaced from the cemented lens component L21 by an air space and having a convex surface on the object side and disposed behind the first lens group with respect to an object side; and a third lens group having a positive refractive power and disposed behind the second lens group with respect to the object side.

Abstract: A wide-angle projection lens includes a first lens group of negative refractive power, the first lens group having at least one aspheric surface. The projection lens also includes a second lens group of substantially zero refractive power and a third lens group of positive refractive power. The projection lens satisfies the following three conditions: |F1/F|<4.0 (Condition (1)), |F2/F|>50 (Condition (2)) and |F3/F|<3.5 (Condition (3)). In these conditions, F is the focal length of the wide-angle projection lens; F1 is the focal length of the first lens group; F2 is the focal length of the second lens group; and F3 is the focal length of the third lens group. The wide-angle projection lens is used in a front projection display device.

Abstract: A super-wide zoom lens system having sufficient zoom ratio and a high speed, capable of obtaining high optical performance. The system includes at least, in order from an object, a first lens group G1 having negative refractive power, and a second lens group G2 having positive refractive power. When zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group G1 and the second lens group G2 varies. The first lens group G1 includes at least one negative lens element and a glass material constructing at least one negative lens element (SL1) in the first group G1 satisfies given conditions.

Abstract: A wide angle projection lens include a first lens group of negative refractive power that has at least one aspheric surface. The wide angle projection lens can output an image at a half field angle of at least 45°, where the image has substantially no distortion and requires little or no keystone correction. The wide angle projection lens can be part of an optical engine that can be implemented in rear projection or front projection display devices.

Abstract: A projection optical system and an image projection apparatus that are small in size and can achieve projection with a wide angle while a good image forming performance is assured includes a first lens group having a negative refracting power and a second lens group also having a negative refracting power. The first and second lens groups are arranged in order from the projection side. The first lens group includes a negative meniscus lens that has a concave surface directed to the projection side and formed as an aspherical reflecting surface.

Abstract: The invention relates to an electronic image pickup system that enables a wide image-pickup, and ensures that even when an image is printed, sufficient image quality and clearness are obtained from the center to as far as the margin of the image and the image of a subject is depicted with a sense of extension. The electronic image pickup system comprises an image-formation optical system 10 for forming an image of a subject and an electronic image pickup device 20 located on an image side of the image-formation optical system for obtaining image information on the image.

Abstract: A zoom lens, including, in order from an object side to an image side (a) a first lens unit of negative optical power, (b) a second lens unit of positive optical power, and (c) a third lens unit of positive optical power, wherein a separation between the first lens unit and the second lens unit and a separation between the second lens unit and the third lens unit are varied to effect variation of magnification, and wherein, during the variation of magnification from a wide-angle end to a telephoto end with an infinitely distant object focused on, the third lens unit moves monotonically toward the image side or moves with a locus convex toward the image side.

Abstract: A zoom lens, including, in order from an object side to an image side (a) a first lens unit of negative optical power, (b) a second lens unit of positive optical power, and (c) a third lens unit of positive optical power, wherein a separation between the first lens unit and the second lens unit and a separation between the second lens unit and the third lens unit are varied to effect variation of magnification, and wherein the zoom lens satisfies the following conditions: ndp3<1.5 and vdp3>70.0, where ndp3 and vdp3 are a refractive index and Abbe number, respectively, of material of the positive lens in the third lens unit.

Abstract: A zoom lens in which when the magnification is changed in the range from a wide-angle position to a telephoto position in infinite object point focusing, spacing between a first lens unit, with negative refractive power as a whole, having a negative lens and a positive lens, and a second lens unit, with positive refractive power as whole, having a positive lens and a cemented lens component constructed with a positive lens and a negative lens, is narrowed and spacing between the second lens unit and a third lens unit, a single positive lens component, is widened, and the zoom lens satisfies the following condition: 2.1<|?2T|<2.8 where ?2T is the magnification of the whole of the second lens unit at the telephoto position in the infinite object point focusing.

Abstract: A wide-angle zoom lens system includes a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group. Upon zooming from the short focal length extremity to the long focal length extremity, the distance between the negative first lens group and the positive second lens group decreases, the distance between the positive second lens group and the negative third lens group increases, and the distance between the negative third lens group and the positive fourth lens group decreases; and the positive second lens group, the negative third lens group and the positive fourth lens group move toward the object. The wide-angle zoom lens system satisfies the following conditions: 1.2<|f(i=1)/fW|<2.0??(1) 1.5<f(i=2)/fW<2.2??(2) 2.5<|f(i=3)/fW|<3.6??(3) 3.2<f(i=4)/fW<4.

Abstract: To realize a zoom lens system, including, in order from an object side to an image side: a first lens unit having a negative optical power; a second lens unit having a positive optical power; a third lens unit having a negative optical power; and a fourth lens unit having a positive optical power, in which: during zooming, an interval between the first lens unit and the second lens unit at a telephoto end is smaller than that at a wide angle end, an interval between the second lens unit and the third lens unit at the telephoto end is larger than that at the wide angle end, and an interval between the third lens unit and the fourth lens unit at the telephoto end is smaller than that at the wide angle end; and specific conditions are satified.

Abstract: An optical system includes in order from an object side, a negative lens having a concave surface directed toward an object side, an aperture stop, a double convex lens, a negative meniscus lens having a convex surface directed toward an image side, and a positive lens. A surface at the object side of the fourth positive lens is constituted with an aspherical surface, a radius of curvature which decreases from a center portion toward a circumferential portion and a surface at the image side of the positive lens an aspherical surface, radius of curvature of which increases from the center portion toward the circumferential portion and the following condition is satisfied: 0.05<?m/?p<0.80 where m represents the power of the positive lens at the position of the maximum light height and p represents the power of the positive lens at the position the praxis.

Abstract: A zoom lens system includes a negative first lens element, a positive second lens element and a positive third lens element, in this order from the object. Upon zooming from the short focal length extremity to the long focal length extremity, the positive second lens element and the positive third lens element move along the optical axis, while the negative first lens element remains stationary. Furthermore, the positive second lens element is directed to move from the image side toward the object side.

Abstract: A zoom lens includes a plurality of lens groups including a first lens group arranged on the foremost side and having negative optical power. Zooming is performed by moving at least one of the plurality of lens groups along a direction parallel to an optical axis of the zoom lens. The first lens group is fixed during the zooming. A first lens arranged on the foremost side, of the first lens group has negative refractive power. When an Abbe constant and a partial dispersion of a material configuring the first lens are respectively represented by ?dn and ?g,Fn, a focal distance of the first lens group is represented by f1, and an air-equivalent back focus upon focusing on an infinity object is represented by bf, the following conditions are satisfied: ?dn<32, 0.008<?g,Fn?(0.644?0.00168×?dn)<0.040, and |f1/bf|<0.9.

Abstract: A zoom lens system in which reductions in the number of lenses and entire lens length are realized is provided. The zoom lens system includes, in order from an object side to an image side, a first lens unit having negative optical power, a second lens unit having positive optical power, and a third lens unit having positive optical power. During zooming from a wide-angle end to a telephoto end, an interval between the first lens unit and the second lens unit reduces and an interval between the second lens unit and the third lens unit changes. An aspherical lens is used for a positive lens element of the first lens unit. Shapes of respective lens elements composing the first lens unit, an interval therebetween, and the like are suitably set.

Abstract: A zoom lens system that has a structure suitable to widen a field angle and realizes high optical performance over the entire zoom range is provided. The zoom lens system includes, in order from an object side to an image side, a first lens unit having negative optical power, a second lens unit having positive optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power. During zooming from a wide-angle end to a telephoto end, an axial interval between the first lens unit and the second lens unit reduces, an axial interval between the second lens unit and the third lens unit increases, and an axial interval between the third lens unit and the fourth lens unit reduces. In the zoom lens system, a back focus and refractive indices of the respective lens units are suitably set.

Abstract: A zooming lens is suitable for projecting images produced by a display device onto a screen. The zooming lens includes a first set of lenses and a second set of lenses, wherein the second set of lenses is disposed in the optical path between the first set of lenses and the display device. The first set of lenses includes first lens, second lens, third lens, and fourth lens sequentially, and the fourth lens is adjacent to the second set of lenses. The second set of lenses includes fifth lens, sixth lens, seventh lens, and composite lens sequentially, and the composite lens is adjacent to a side of the display device. The optical focusing of the lenses, from the first one through the seventh and to the composite lens, are positive, negative, negative, positive, positive, negative, positive value and positive, respectively. The composite lens includes two optical lenses.

Abstract: The pickup lens (1) employing the present invention includes a first lens group (11) having negative power, a diaphragm (12), a second lens group (13) having positive power, and a third lens group (14) having negative power, which are arranged in this order from the side of a subject. When varying optical power, in the pickup lens (1), the first lens group (11) is fixed, and the second lens group (13) is moved along the optical axis together with the diaphragm (12), and the third lens group (14) is moved along the optical axis to correct movement of the image point due to variation of optical power.

Abstract: Provided is a zoom lens system suitably used for, for example, an image taking optical system of a camera including a solid-state image pickup element. The zoom lens system includes a first lens unit having negative optical power, a second lens unit having positive optical power, and a third lens unit having positive optical power. During zooming, an interval between the first lens unit and the second lens unit and an interval between the second lens unit and the third lens unit are changed. The first lens unit consists of a first lens element having negative optical power and a second lens element having positive optical power. The first lens element has an aspherical surface. The first lens element is made of a material having a high refractive index.

Abstract: An optical system of a telephoto type is disclosed, in which a refractive optical element made of a solid material that satisfies?d<30, ?gd<?3.333×10?3·?d+1.40 and ?gF<?2.615×10?3·?d+0.67 is installed, ?d representing an Abbe's number, and ?gd and ?gF representing partial dispersion ratios. A refractive power with adequate sign is given to the refractive optical element in accordance with its location. Thereby, an optical system, which can excellently correct various aberrations such as chromatic aberration, and can be manufactured easily, and has an excellent environment resistance, is realized.

Abstract: A zoom lens includes (i) a negative first lens group having a negative meniscus first lens element and a positive meniscus second lens element; and (ii) a positive second lens group having a positive third lens element, a positive fourth lens element, a negative fifth lens element which is cemented to the positive fourth lens element, and a sixth lens element having a weaker refractive power. Zooming is performed by moving the first lens group and the second lens group along the optical axis. The zoom lens system satisfies TL/fW<1.9; and 0.6<fW/fII<0.77, wherein TL is the sum of the length of the first lens group and that of the second lens group; fW is the combined focal length of the zoom lens at the wide-angle extremity; and fII is the focal length of the second lens group.

Abstract: A projection lens system is comprised of five lens groups. A first lens group forms a negative power lens group, and a second lens group forms a positive power lens group. Third, fourth, and fifth lens groups, when combined, form a positive power lens group, which helps to compensate for aberrations. At least one of the component lenses moves to adjust the system's focus. An image display system that includes such a projection lens system can project digital optical images for projection and other image display applications.

Abstract: A comparatively low f-number, compact two-group zoom optical system that corrects aberrations in the visible and the near-infrared regions includes, in order from the object side, a first lens group of negative refractive power and a second lens group of positive refractive power. The first lens group includes three lens components that are lens elements of negative, negative, negative, and positive refractive power, respectively, in order from the object side. The second lens group includes four lens components that are lens elements of positive, positive, negative, and positive refractive power, respectively, in order from the object side. Aspheric surfaces are disclosed. Certain conditions relating to the focal lengths of the two lens groups, indexes of refraction and Abbe numbers of various lens elements, and radii of curvature of an interior lens element of the second lens group are satisfied to control aberrations in both the visible and the near-infrared regions.

Abstract: A three-group zoom lens includes, in order from the object side, first, second and third lens groups having negative, positive and positive refractive power, respectively. During zooming from the wide-angle end to the telephoto end, the second lens group moves monotonically toward the object side while moving closer to the first lens group and farther from the third lens group, and the first and third lens groups reverse directions to define curved paths. The third lens group is closer to the object side at the wide-angle end and moves toward the object side for close focusing. The focal lengths of the zoom lens and its lens groups, the zoom ratio, the length of the zoom lens, and the half-field angle at the wide-angle end satisfy certain conditions in order to achieve a zoom ratio of at least three with favorable correction of aberrations.

Abstract: A stepwise variable zoom lens system according to the present invention has, in order from an object side, a first lens group of negative refracting power, a second lens group of positive refracting power, and a third lens group of positive refracting power. The first and third lens groups are constructed from a single block. The second lens group includes a positive first lens unit and a negative second lens unit which is also constructed from a single block. The first and third lens groups are fixed, and the second lens group is movable to be selectively disposed in several discrete positions. The focal lengths of the lens groups satisfy the following relations: f 2 · ( 1 + z ) > - f 1 f 2 · ( 1 + 1 z ) > f 3 · f b f 3 - f b wherein f1, f2 and f3 denote the focal lengths of the first, second and third lens groups respectively, fb denotes the back focal length of the stepwise variable zoom lens system, and z denotes the zoom ratio.

Abstract: A projection zoom lens includes, from an image side to an object side, a first lens group having a negative refractive power, consisting of a number of lens elements and being movable along the optical axis of the projection zoom lens; a second lens group having a positive refractive power, consisting of a number of lens elements and being movable along the optical axis of the projection zoom lens; and an aperture stop arranged between two lens elements of the second lens group and being axially movable therewith.

Abstract: A six element fisheye objective lens comprising a first lens element having a convex object surface facing the object and a concave image surface facing the image plane, a second lens element having a convex object surface facing the object and a concave image facing the image plan. A third lens element has a positive power. A positively powered lens group has a positively powered cemented doublet lens pair. A singlet lens element has a positive power, The lens group has an object surface facing the object and an image surface facing the image. The ratio of the total track to the focal length satisfies the condition that 8<TT/fo<15. The fisheye objective lens has an optical axis, the first, second, third and the lens group being coaxially aligned on the optical axis.

Abstract: A zoom lens, including, in order from an object side to an image side (a) a first lens unit of negative optical power, (b) a second lens unit of positive optical power, and (c) a third lens unit of positive optical power, wherein a separation between the first lens unit and the second lens unit and a separation between the second lens unit and the third lens unit are varied to effect variation of magnification, and wherein, during the variation of magnification from a wide-angle end to a telephoto end with an infinitely distant object focused on, the third lens unit moves monotonically toward the image side or moves with a locus convex toward the image side.

Abstract: Disclosed is a zoom lens system including in an order from an object side to an image side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, in which zooming is performed by changing each distance among the first, second, and third lens units. In this zoom lens system, partial charge of a changing magnification between the second and third lens units is suitably set to maintain excellent optical performance over the overall zoom area while a zoom ratio is large.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group. Upon zooming from the short focal length extremity to the long focal length extremity, a distance between the negative first lens group and the positive second lens group decreases, and a distance between the positive second lens group and the positive third lens group increases. When zooming is being performed, the negative first lens group remains stationary, and the positive second lens group and the positive third lens group are moveable along the optical axis of the zoom lens system; and the zoom lens system satisfies the following conditions: 1.5<f3/f2<2.5 ??(1) 0.8<f2/(fw*ft)1/2<1.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group. Upon zooming from the short focal length extremity to the long focal length extremity, a distance between the first lens group and the second lens group decreases, and a distance between the second lens group and the third lens group increases. When zooming is being performed, the third lens group remains stationary, and the first lens group and the second lens group are moveable along the optical axis of the zoom lens system; and the zoom lens system satisfies the following conditions: 3.0<f3/f2<3.5??(1) 1.4<|f1/fW|<2.0??(2) 0.8<f2/fW<1.5??(3) wherein f1 designates the focal length of the first lens group; f2 designates the focal length of the second lens group; f3 designates the focal length of the third lens group; and fw designates the focal length of the entire zoom lens system at the short focal length extremity.

Abstract: The present invention discloses a zoom lens which reduces the size of an entire lens system, effectively corrects various types of aberration accompanying zooming and has good optical performance over the entire screen. The zoom lens comprises, in order from a front side to a rear 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 positive or negative refractive power and a sixth lens unit having a positive refractive power and satisfies the set forth conditions.

Abstract: An objective has a front group, a focus group displaceable along the optical axis and a follow-on lens group having a diaphragm. The front group is arranged at the objective end. The lens group having the diaphragm includes at least two composite lenses and/or two positive lenses and/or the back focus can be adjusted. An objective series is presented wherein all objectives of the series have a uniform appearance and/or the diaphragm is arranged in all objectives proceeding from the image plane at the same location.

Abstract: A pickup lens is provided in which various aberrations are satisfactorily corrected, which can be manufactured at low cost, and which has an optical length of 10 mm or less. This pickup lens is configured by arranging, in order from the object side, a first lens L1 with a meniscus shape with concave surface on the object side and having negative refractive power, an aperture diaphragm S, a second lens L2 with convex surfaces on both sides and having positive refractive power, a third lens L3 with concave surfaces on both sides and having negative refractive power, and a fourth lens L4 with convex surfaces on both sides and having positive refractive power; and with the following conditions satisfied. +5.0<(r2+r1)/(r2?r1)<+7.0??(1) 0.15f<d1<0.

Abstract: An imaging optical system includes a first lens unit located at the most object-side position and at least one of lens units interposed between the first lens unit and an image. At least one of the lens units is moved along the optical axis. The first lens unit includes, in order from the object side, at least one lens with negative refracting power, a deformable mirror, and at least one lens with positive refracting power, and focusing is performed by the deformation of the deformable mirror.

Abstract: A zoom lens includes three lens groups. The first lens group from the object side has negative refractive power and is formed of two lens components. The second lens group from the object side has positive refractive power and is formed of two lens components. The third lens group is formed of one lens component and has positive refractive power. All but one of the lens components may be lens elements. Only the first and second lens groups move along the optical axis for zooming. At least one lens surface of the second lens group has portions with curvatures of different signs. The zoom lens may include as many as five other aspheric surfaces. The aspheric lenses are made of plastic. The zoom lens may be formed of only the three lens groups and satisfies specified conditions to assure that the zoom lens is compact and favorably corrects various aberrations.

Abstract: A negative first group optical system, a positive second group optical system, and a positive third group optical system are sequentially arranged from the object side. A stop moving integrally with the second group optical system is provided on the object side of the second group optical system. The focal length is changed by changing distances between the group optical systems, and the third group optical system is moved on an optical axis. The first group optical system includes a negative meniscus lens, a negative meniscus lens, and a positive lens. The second group optical system includes a cemented lens of a positive lens and a negative lens, a positive lens, and a positive lens. The third group optical system includes one positive lens not including an aspherical surface.