Abstract: A zoom lens includes, in order from the object side to the image side, first, second, third and fourth lens units of positive, negative, positive and positive refractive powers, respectively, wherein at least the second, third and fourth lens units are moved in such a way that an interval between the first and second lens units becomes larger at a telephoto end than at a wide-angle end, the interval between the second and third lens units becomes smaller at the telephoto end than at the wide-angle end, and the interval between the third and fourth lens units becomes larger at the telephoto end than at the wide-angle end, and wherein the following conditions are satisfied: −0.50<M4/(fT−fW)<−0.05 0.03<fW/f1<0.20 0.48<L/fW<1.

Abstract: A zoom lens system has, from the object side, a first lens unit, a second lens unit and a third lens unit. The first lens unit has a negative optical power as a whole. The second and third lens units have a positive optical power as a whole. In the zoom lens system, zooming is achieved by varying the distance between the first and second lens units, and at least one of the lens elements is a plastic lens element.

Abstract: There are provided a zoom lens system comprising, in order from a more distant conjugate point, a first lens unit of a negative refractive power, a second lens unit of negative refractive power which moves during zooming, third, fourth and fifth lens units, and at least one diffraction optical element.

Abstract: An image stabilizing optical lens device including, in order from an object side to an image side of the image stabilizing optical lens device, a first lens unit having positive refractive power, a second lens unit having negative refractive power and being movable along an optical axis of the image stabilizing optical lens device to perform focusing, and a third lens unit having positive refractive power, the third lens unit including a front lens sub-unit having negative refractive power and being movable so as to be decentered with respect to the optical axis and a rear lens sub-unit having positive refractive power.

Abstract: A taking lens device has a zoom lens system having an optical system that is comprised of a plurality of lens units and that achieves zooming by varying the unit-to-unit distances and an image sensor that converts an optical image formed by the zoom lens system into an electric signal. The zoom lens system is comprised of, from the object side, a first lens unit having a positive optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a negative optical power. At least one of the following conditional formula is fulfilled: 1.1<f1/fT<2.5, where f1 represents the focal length of the first lens unit, and fT represents the focal length of the entirety optical system at the telephoto end, and 0.3<D34W/D34T<2.5 where D34W and D34T represent axial distance between the third lens unit and the fourth lens unit at wide-angle end and telephoto end, respectively.

Abstract: A zoom lens comprising, in the order of an increasing distance from an object; a fixed first lens group (1) having a positive refractive power; a second lens group (2) containing an aspherical surface, having a negative refractive power and being in charge of a variable power action by being moved; a fixed third lens group (3) containing an aspherical surface and having a positive refractive power; and a fourth lens group (4) containing an aspherical surface, having a positive refractive power and moving while following up a moving object point; wherein the surface on the image plane side of a lens positioned closest to the image plane in the third lens group (3) has a concave plane having a strong refractive power with respect to the image plane and a relation, 2.0<L/CL1<2.

Abstract: An inner-focusing type super wide-angle zoom lens system consisting of two lens groups, a negative lens group and a positive lens group, with the maximum angle of view of more than 100° and the zoom ratio of 1.7 or more is provided. The zoom lens system includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. Zooming operation is carried out by changing the interval between the first lens group G1 and the second lens group G2. The second lens group consists of, in order from the object side, a front second lens group G2a having a positive refractive power and a rear second lens group G2b having a positive refractive power. Focusing operation from infinity to near object is carried out by moving the front second lens group G2a to the image side. Predetermined conditional expressions are satisfied.

Abstract: The present invention is directed to a compact and lightweight high magnification zoom lens utilizing a 4-element zoom layout of positive, negative, positive, and positive in refractive property, which is approximately 75 degrees in shooting angle of view at a wide-angle end, approximately F/3 to F/4 in F-number at the wide end, approximately F/5 to F/6 at a tele end, and approximately 6 to 7 in zoom ratio. The zoom lens includes first to fourth elements each comprised of a plurality of lenses, and the elements have respective refractive powers of positive, negative, positive, and positive levels in order from the closest to a subject. Only the second element of lenses is moved for focusing while the conditions described as follows are satisfied: 0.065<&phgr;T/|&phgr;2|<0.085  (1) 0.35<&phgr;T/|&phgr;1<0.55   (2) 0.25<&phgr;T/&phgr;4<0.35  (3) 0.75<|&bgr;2T|<0.

Abstract: An optical system for scanning, which can prevent the depth of focus from decreasing when magnification of the optical system is changed, especially when the magnification is increased. In this optical system, a zoom lens and a focus lens are arranged between a light source for emitting light beams and a scanning and focusing surface. In accordance with a desired resolution, an aperture is arranged at a position at which a far-field pattern is formed. When the magnification of the optical system is increased by the zoom lens, a luminous flux is widened, and a converging angle formed by the focus lens is also widened. However, since the aperture shields the luminous flux by an amount by which the converging angle has been widened, the converging angle is the same as that when an image is recorded at low resolution. Hence, the depth of focus can be maintained.

Abstract: An optical system includes a first lens unit, a second lens unit, and a third lens unit. The second lens unit is movable. By moving the second lens unit, astigmatism due to the first lens unit and the second lens unit is corrected and astigmatism due to the second lens unit and the third lens unit is corrected.

Abstract: A zoom lens system includes a positive first lens group and a negative second lens group. In a short-focal-length side zooming, the first and second lens groups are moved towards the object, while the moveable sub-lens group is stationary at the object-side end. At the intermediate switching focal length, the moveable sub-lens group is moved to the image-side end, and the first and second lens groups are moved towards the image plane. In a long-focal-length side zooming range, the first and second lens groups are moved towards the object, while the moveable sub-lens group is stationary at the image-side end. Moreover, the zoom lens system satisfies 0.3<logZi/logZ<0.8 . . . (1); wherein Zi=fm/fw; Z=ft/fw; fw designates the focal length at the short focal length extremity; ft designates the focal length at the long focal length extremity; and fm designates the intermediate switching focal length.

Abstract: A zoom lens disclosed herein, having excellent optical performance within a full zoom range, is appropriate for use as a photographing lens for a lens-shutter camera, a video camera, and a digital still camera. The zoom lens includes at least four lens units from the object side, i.e., a first lens unit of negative refractive power, a second lens unit of positive refractive power, a third lens unit of positive refractive power, and a fourth lens unit of negative refractive power. A zooming operation is performed by axially moving the lens units so that the spacing between the first lens unit and the second lens unit becomes wider at the telephoto end than at the wide-angle end, the spacing between the second lens unit and the third lens unit becomes wider at the telephoto end than at the wide-angle end, and the spacing between the third lens unit and the fourth lens unit becomes narrower at the telephoto end than at the wide-angle end.

Abstract: There is provided a zoom lens system of one aspect of the present invention includes, in order from an object side, a first lens unit of positive refractive power that doesn't move along an optical axis for zooming, a second lens unit of negative refractive power that moves along the optical axis for zooming, a third lens unit of positive refractive power that doesn't move along the optical axis for zooming, the third lens unit including, in order from the object side, a first lens subunit of positive refractive power consisting of one or two positive lens element facing to the object side a convex surface of refractive power that is stronger at the object side than an image side, and a second lens subunit including a cemented lens coupling a concave surface of a negative lens element of refractive power that is stronger at the image side than at the object side, with a convex surface of a positive lens element of refractive power that is stronger at the object side than at the image side, and a fourth lens u

Abstract: A zoom lens system has, sequentially from enlarging side to reducing side, first lens unit having negative optical power; second lens unit having positive optical power, the second lens unit having a positive lens element positioned nearest the reducing side; diaphragm; third lens unit having positive optical power, the third lens unit comprising, sequentially from enlarging side to reducing side, a cemented lens unit having a positive lens element and a negative lens element with a concave surface facing the reducing side, and a positive lens element having a concave surface facing the reducing side; fourth lens unit having negative optical power; and fifth lens unit having positive optical power. The second, third, and fourth lens units move from enlarging side to reducing side when zooming from telephoto end to wide angle end. The zoom lens system satisfies a predetermined condition.

Abstract: The object of the invention is to reduce the thickness of electronic image pickup equipment as much as possible, using a zooming mode having stable, high image-formation capabilities from an object at infinity to a near-by object. The electronic image pickup equipment comprises a zoom lens system comprising a negative, first lens group G1, a positive, second lens group G2 and a positive, third lens group G3. For zooming from the wide-angle end to the telephoto end of the zoom lens system upon focused on an object at infinity, the separation between G2 and G3 becomes wise. By moving G3 toward the object side of the system, the system can be focused on a nearer-by object. In the zoom lens system, the second lens group G2 comprises one positive lens 2a, one negative lens 2b and a lens subgroup 2c comprising at least one lens, and the third lens group G3 comprises one positive lens.

Abstract: A zoom lens comprises first to fifth lens groups successively from the enlargement side. The first lens group is fixed upon changing power and has a negative refracting power and a focusing function. The second and third lens groups having a positive refracting power and the fourth lens group having a negative refracting power are moved with a mutual relationship so as to continuously change power and correct the image surface movement caused by the continuous change in power. The fifth lens group has a positive refracting power and is fixed upon changing power. The first to fifth lens groups satisfy predetermined conditional expressions concerning their focal lengths.

Abstract: A lens having a long focal length that is suitable for photography with a large film size is disclosed having three lens groups of positive, negative, and positive refractive power, in order from the object side, as follows: a first lens group having a positive refractive power and formed of, in order from the object side, one or two positive lens element(s), a negative lens element, and a positive lens element; a second lens group having a negative refractive power and formed of, in order from the object side, a negative lens element and a positive lens element; and a third lens group having a positive refractive power and formed of, in order from the object side, a positive lens element, a negative lens element, and a positive lens element. Focusing is performed by moving the second lens group as one unit along the optical axis.

Abstract: The invention relates to a zoom lens system which is compatible with a TTL optical finder having a diagonal field angle of at least 70° at the wide-angle end and about 7 to 10 magnifications and is fast as represented by an F-number of about 2.8 at the wide-angle end. The zoom lens system comprises a first lens group G1 which is movable along its optical axis during zooming and has positive refracting power, a second lens group G2 which moves toward the image side along the optical axis during zooming from the wide-angle end to the telephoto end and has negative refracting power and rear lens groups G3 to G6 having at least two spacings variable during zooming. In particular, the focal length f1 of the first lens group G1 should meet 6<f1/L<20 where L is the diagonal length of an effective image pickup surface I located in the vicinity of an image-formation plane.

Abstract: A zoom lens includes a first lens band having a positive focal length, a second lens band having a negative focal length, and at least third to fifth lens bands having positive focal lengths. An aperture diaphragm is located in the vicinity of the third lens band. When magnification i.e., zooming is performed from short to long focal point ends, the second lens band smoothly moves toward the third lens band and the fourth lens band simultaneously moves from the fifth lens band side toward a long focal point end so as to share a magnification function together with the second lens band.

Abstract: A zoom lens of the rear-focus type includes, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power. The variation of magnification from a wide-angle end to a telephoto end is effected by moving the second lens unit toward the image side. Shifting of an image plane caused by the variation of magnification is compensated for by moving the fourth lens unit. Focusing is effected by moving the fourth lens unit. The second lens unit consists of, in order from the object side to the image side, a negative lens, a negative lens, a positive lens and a negative lens, the third lens unit comprises a plurality of positive lenses and a negative lens, and the fourth lens unit consists of a negative lens and a positive lens, and wherein the following condition is satisfied: 0.25<(Fm−Fw)/(Ft−Fw)<0.

Abstract: A macro zoom lens system includes at least three lens groups, such as, a positive first lens group, a negative second lens group, and a positive third lens group, in this order from the object. Upon zooming, at least two lens groups are made moveable. On the other hand, upon focusing at any focal length in the focal-length range defined by the short focal length extremity and the long focal length extremity, any one of the lens groups other than the first lens group is made moveable. Furthermore, at the shortest object-to-image distance, an image magnification of more than ½ is obtained at the long focal length extremity.

Abstract: A zoom lens system which includes a first lens unit having negative refractive power, a second lens unit having positive refractive power and a third lens unit having positive refractive power, and is configured to change a magnification from a wide-angle position to a telephoto position by moving the second lens unit along an optical axis on the object side and moving the third lens unit along the optical axis in which said second lens unit consists of four lens elements including, in order from the object side, two positive lens elements and a negative lens element, and which can be focused by moving a third lens unit, and in which each lens unit is thin and which is thin as a whole, and an image pickup apparatus which uses this zoom lens system and has a shallow depth.

Abstract: A zoom lens system includes a plurality of lens groups being relatively moveable in order to vary the focal length, and at least one lens group is arranged to be a switching lens group which includes two or more sub-lens groups, and in which one sub-lens group is made moveable, along the optical axis, with respect to the other sub-lens group. In the first focal-length range of the zooming range of the zoom lens system, the moveable sub-lens group and the other sub-lens group maintain the first distance; and in the second focal-length range which covers the first focal-length range and a range different therefrom, the moveable sub-lens group and the other sub-lens group maintain the second distance which is different from the first one.

Abstract: The invention relates to a zoom lens system of three-group construction, one lens for each group, which is less susceptible to aberration variations even upon zooming and can achieve entire-length reductions, large lens aperture and high zoom ratio. The zoom lens system comprises, in order from an object side thereof, a first lens group G1 consisting of one single lens formed of a homogeneous medium and having positive refracting power, a second lens group G2 consisting of one single lens formed of a homogeneous medium and having negative refracting power, and a third lens group G3 consisting of one single lens formed of a homogeneous medium and having positive refracting power. For zooming from a wide-angle end to a telephoto end of the zoom lens system, at least the second lens group G2 moves from the object side toward an image side of the zoom lens system.

Abstract: A zoom image pickup optical system including, in order from the object side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power and a fourth lens unit having positive refractive power, in which at least the second lens unit and the fourth lens units are moved along an optical axis to change a magnification, in which the third lens unit includes at least two lens components, in which the fourth lens unit includes at least two lens components, and in which radii of curvature on at least one or pairs of surfaces of the third lens unit and the fourth lens unit such as an image side surface of a most image side lens component in the third lens unit and an object side surface of a most object side lens component in the fourth lens unit which correspond to each other with regard to an airspace between the third lens unit and the fourth lens unit have different signs.

Abstract: An electronic picture taking apparatus comprises a zoom lens system and an image pickup device. The zoom lens system has a type of movement suitable for stable, high performance in the range from infinite to near distance and being thoroughly reduced the thickness. The zoom lens system comprises at least four lens units. A foremost first lens unit on the object side of said zoom lens system has a negative refractive power. Each of three consecutive lens units has variable space on the image side thereof between an adjacent lens unit for performing a zooming operation. A rearmost lens unit of the zoom lens system consists of a single positive lens element having an aspherical surface and being fixed during the zooming operation. The zoom lens system includes an aperture stop moving incorporated with the second lens unit which is adjacent to the first lens unit.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group. Upon zooming, the first through fourth lens groups move toward the object so that the distance between the first and the second lens groups becomes longer, the distances among the second, the third and the fourth lens groups become shorter. The third lens group includes a positive 3-1st lens element, a positive 3-2nd lens element, and a negative 3-3rd lens element. The zoom lens system satisfies the following condition: −1.8<Ør3-3-1/Øw<−1.1...  (1) wherein Ør3-3-1 designates the surface power of the object-side surface of the negative 3-3rd lens element of the third lens group; and Øw designates the power of the entire lens system at the short focal length extremity.

Abstract: An objective lens for endoscope comprises, successively from an object side, a first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, and a fourth lens group having a positive refracting power; wherein the third lens group and one of the second and fourth lens groups are movable along an optical axis. The objective lens further satisfies the following conditional expressions: 2.0<&bgr;1T/&bgr;1W<10.0 1.2<fT/fw where &bgr;1T is the magnification of the first lens group at the telephoto end; &bgr;1W is the magnification of the first lens group at the wide end; fT is the focal length of the whole lens at the telephoto end; and fW is the focal length of the whole lens at the wide end.

Abstract: A camera includes a zoom lens having a first lens group having a positive focal length, a second lens group having a negative focal length, an opening iris, a third lens group having a positive focal length, and a fourth lens group having a positive focal length. The first lens group, the second lens group, the opening iris, the third lens group and the fourth lens group are arranged in order from the object side, When zooming from a short focal point end toward a long focal point end, the second lens group moves from the object side toward the image side, and the third lens group first moves from the image side toward the object side, and then, after arriving at a position closest to the object side in an area at a long focal point side beyond an intermediate focal point, moves toward the image side.

Abstract: A three-group zoom lens of negative, positive, and positive refractive power, in order from the object side. The first lens group is formed of two lens elements of negative and positive refractive power, respectively, the second lens group includes an aperture stop on its object side, and at least one surface in each of these lens groups is aspherical. When zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group decreases and both the second and the third lens groups move toward the object side. When changing the focus from an object at an infinite distance to a nearby object the position of the third lens group is shifted. When focused on an object at infinity, the distance between the second lens group and the third lens group is kept substantially constant when zooming from the wide-angle end to the telephoto end. The zoom lens has a zoom ratio of 2.

Abstract: A zoom lens system having multiple lens units including, sequentially in a direction from an enlargement side thereof toward a reduction side thereof, a first lens unit having a negative optical power, a second lens unit having a positive optical power, a third lens unit having a positive optical power, a fourth lens unit having a negative optical power, and a fifth lens unit having positive optical power. Additionally, during a zoom operation from a longest focal length condition to a shortest focal length condition, the zoom lens system can function such that the first lens unit and the fifth lens unit can remain stationary, while the second, third and fourth lens units are able to move.

Abstract: The invention relates to an apparatus for moving an optical functioning element at sufficient accuracy over a long period of use or in a case where the temperature changes, in which a voltage is applied only when moving an optical functioning element, wherein a moving member 4, which moves forward and rearward in one direction by a guiding member 5, and one end of an optical filter main body 41, which is fixed at the moving member 4, are brought into contact with the circumferential surface of a disk-shaped eccentric cam 3 that rotates by an ultrasonic motor 2, and a coil spring 6 is brought into contact with the other end of the optical filter main body 41, whereby pressing the moving member 4 to the eccentric cam 3 side.

Abstract: A zoom lens system includes a positive first lens group, a positive second lens group, and a negative third lens group. Upon zooming from the short toward the long focal length extremities, the three lens groups are moved independently along the optical axis so that the distance between the first and second lens groups increases, and the distance between the second and third lens groups decreases. The first lens group and the second lens group which are independently moved upon zooming are integrally moved upon focusing.

Abstract: A zoom lens, includes, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, wherein a variation of magnification from a wide-angle end to a telephoto end is effected by moving the second lens unit toward the image side, shifting of an image plane due to the variation of magnification is compensated for by moving the fourth lens unit and focusing is effected by moving the fourth lens unit, a stop being disposed on the most object side of the third lens unit, the third lens unit including a positive lens (G3F) disposed on the image side of the stop and just behind the stop and having a convex lens surface facing the object side, at least one of lens surfaces of the positive lens (G3F) being an aspheric surface, and a negative lens (G3R) of meniscus form disposed on the most image side and having a concave surface facing the

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, and a positive third lens group, in this order from the object. Zooming is performed by moving the second lens group and the third lens group, and the zoom lens system satisfies the following conditions: 0.0<Fw/f1<0.15  (1) 0.75<|f2/f3|<1.0  (2) 1.65<LD/Ft<2.25  (3) wherein Fw designates the focal length of the entire lens system at the short focal length extremity; Ft designates the focal length of the entire lens system at the long focal length extremity; 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 LD designates the distance, at the short focal length extremity, from the most object-side surface of the first lens group to the most image-side surface of the third lens group.

Abstract: A zoom lens comprising a first lens group having a positive refracting power and its position fixed, a second lens group having a negative refracting power and displacable mainly for magnification, a third lens group having a positive refracting power and its position fixed, and a fourth lens group having a positive refracting power and displacable mainly for correction of the focal position for magnification and focusing.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power arranged to move during variation of magnification, a third lens unit arranged to move during variation of magnification, and a fourth lens unit of positive refractive power. The first lens unit includes a first lens subunit arranged to be stationary during focusing, and a second lens subunit of positive refractive power arranged to move during focusing. The first lens subunit includes, in order from the object side to the image side, at least one first positive lens, at least one negative lens of bi-concave form, and at least one second positive lens.

Abstract: The object of the invention is to reduce the thickness of electronic image pickup equipment as much as possible, using a zooming mode having stable, high image-formation capabilities from an object at infinity to a near-by object. The electronic image pickup equipment comprises a zoom lens system comprising a negative, first lens group G1, a positive, second lens group G2 and a positive, third lens group G3. For zooming from the wide-angle end to the telephoto end of the zoom lens system upon focused on an object at infinity, the separation between G2 and G3 becomes wise. By moving G3 toward the object side of the system, the system can be focused on a nearer-by object. In the zoom lens system, the second lens group G2 comprises one positive lens 2a, one negative lens 2b and a lens subgroup 2c comprising at least one lens, and the third lens group G3 comprises one positive lens.

Abstract: A variable focal length lens system includes at least three lens groups, in order from an object side, a first lens group G1, a second lens group G2, and a third lens group G3. When the lens group positions are changed from a wide-angle end state to a telephoto end state, each lens group moves from a state focused at infinity to a state focused at near object, in order from a state focused at infinity in the wide-angle end state to a state focused at near object in the telephoto end state. G2 has an aperture diaphragm S, and lens elements are arranged to both object and image side of the aperture diaphragm S.

Abstract: A projection lens of the following structure was invented for the purpose of providing a bright projection optical system with the F-number of approximately 2 or lower while maintaining good optical characteristics, in an image display apparatus. The projection lens is constructed of six lens units, a first lens unit L1 of a negative optical power, a second lens unit L2 of a positive optical power, a third lens unit L3 of a positive optical power, a fourth lens unit L4 of a negative optical power, a fifth lens unit L5, and a sixth lens unit L6 of a positive optical power, in the order named from the enlargement conjugate side, and four lens units (L2 to L5) out of the lens units move toward the enlargement conjugate side during zooming from the wideangle extreme to the telephoto extreme.

Abstract: A rear-focus-type zoom lens having, in order from the object side, four lens groups of positive, negative, positive, and positive power, wherein the first lens group G1 and the third lens group G3 are fixed and the second lens group G2 and the fourth lens group G4 are moved during zooming. Focusing is accomplished by moving the fourth lens group G4. The first lens group G1 is formed of a negative lens element L1 and positive lens element L2 that are joined together, and a positive lens element L3. The second lens group G2 is formed of, in order from the object side, a negative lens element L4 and a lens formed of a negative lens element L5 and a positive lens element L6 that are joined. The third lens group G3 is formed of a single lens element L7, and the fourth lens group G4 is formed, in order from the object side, of positive, negative, positive, and positive lens elements L8-L11, respectively. Further, specified conditions are satisfied.

Abstract: A zoom optical system provides a series of lens units designed to allow for zooming with minimal change in aberration resulting from the movement of the lens units. Each lens unit has a plurality of lens units. One embodiment has, in order from the object 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 and a fourth lens unit having a positive refractive power wherein the second lens unit may have at least one gradient index lens element and the first lens unit is kept stationary during a change of magnification. Additional embodiments have more or fewer lens units and the refractive power of each lens unit is varied. In some embodiments, a lens unit other than the first lens unit is kept stationary.

Abstract: A rear-focusing telephoto lens system includes a positive front lens group, and a positive rear lens group, in this order from the object The front lens group includes at least two positive lens elements, each of which has a large-curvature convex surface facing toward the object, and a negative lens element having a large-curvature concave surface facing toward the image. The rear lens group includes at least one lens element which has a convex surface facing toward the object, and is positioned at the most object-side in the rear lens group. Upon focusing, only the rear lens group moves along the optical axis, and the lens system satisfies the following condition: 0.5<f/fF<0.8  (1) wherein f designates the focal length of the entire lens system; and fF designates the focal length of the front lens group.

Abstract: A compact, real-image-type zoom finder having a high zoom ratio and high optical performance is provided. The finder is formed of an objective optical system and an erecting eyepiece. The objective optical system is formed of, in order from the object side, a first lens element having negative refractive power with a concave surface on the object side, a second lens element having positive refractive power, and a third lens element that is a positive meniscus lens with its convex surface on the object side. The erecting eyepiece is formed of an erecting prism having refractive surfaces integrally formed on the input end and output end of the erecting prism. The magnification of the finder is changed by moving the second lens element along the optical axis, and the third lens element is moved along the optical axis in order to adjust for what would otherwise be a shifting in image surface position with the change in magnification.

Abstract: A zoom lens having both manual mode and auto focus mode of focus adjustment. The zoom lens includes, in order from the object side, a focus portion, a zoom portion, and a main portion. Zooming is accomplished by moving some or all of the lens elements in the zoom portion along the optical axis. What would otherwise be a fluctuation of the image surface with change of object distance is corrected in manual mode by manually moving some or all of the lens elements of the focus portion along the optical axis based on visual observation of the object through the zoom lens as the adjustment is made. In auto focus mode, what would otherwise be a fluctuation of the image surface with change of object distance is corrected by micro-vibrating some or all of the lens elements of a lens group in the light path following the focus portion.

Abstract: The improved inner-focus, wide-angle lens system of retrofocus configuration comprises, in order from the object side, a negative first lens group 10, a positive second lens group 20, and a positive third lens group 30 having a diaphragm; the second lens group 20 moves along the optical axis during focusing and the lens system satisfies the following conditions (1) and (2):

Abstract: A zoom lens includes a first lens unit with a positive refractive power, a second lens unit with a negative refractive power, a third lens unit with a positive refractive power, and a fourth lens unit with a positive refractive power, which are arranged in this order from an object side. At least the first, third and fourth lens units are moved along an optical axis to vary spatial distances of the lens units to thereby change magnification. The third lens unit includes a first lens subunit with a positive refractive power, and a second lens subunit with a negative refractive power, and the second lens subunit is moved to have at least a perpendicular vector component with respect to the optical axis to thereby displace an image.

Abstract: In a zoom lens comprising first to fourth lens groups, the second lens group comprises two meniscus lenses and an achromatic lens. The achromatic lens comprises a cemented lens having a negative refracting power as a whole, and a lens having a positive refracting power with a convex surface directed onto the object side. The cemented lens comprises a meniscus lens or plane-convex lens having a positive refracting power with a convex surface or plane directed onto the object side, and a lens having a negative refracting power.

Abstract: In a short-focal-length side zooming range, a moveable sub-lens group of a zoom lens system is made stationary at one of the object-side and the image-side end. At the intermediate switching focal length, the moveable sub-lens group is moved to the other of the object-side and the image-side end.

Abstract: A zoom lens having only five lens groups of positive, negative, negative, positive and positive refractive power, respectively, in order from the object side. The focal distance is varied by shifting the second and third lens groups, in order from the object side, along the optical axis, and a middle sub-assembly in the first lens group is shifted along the optical axis in order to correct for what otherwise would be a shifting in the image plane as the distance to the object is varied. The first lens group is formed of three sub-assemblies, with the sub-assembly nearest the object side having negative refractive power and being fixed in position, the middle sub-assembly having positive refractive power and shifting as discussed above, and the sub-assembly nearest the image-side having positive refractive power and being fixed in position.