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: The invention relates to a zoom lens that enables an optical path to be easily bent and has high optical specification performance such as a high zoom ratio, a wide-angle arrangement, a small F-number and limited aberrations. The zoom lens comprises, in order from its object side, a lens group A (G1) that comprises a negative lens, a reflecting optical element P for bending the optical path and remains fixed upon zooming, a lens group B (G2) that moves in one direction alone upon zooming from the wide-angle end to the telephoto end of the zoom lens and an aperture stop S that remains immovable with respect to position upon zooming. The zoom lens satisfies condition (1) with respect to the degree of change in the magnification of the lens group B from the wide-angle end to the telephoto end.

Abstract: A high-magnification zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group. Upon zooming from the short focal length extremity to the long focal length extremity, at least the positive first lens group, the positive third lens group, the negative fourth lens group, and the positive fifth lens group move from the image side toward the object side. The high-magnification zoom lens system satisfies the following conditions: 0.65<(fw*ft)1/2/f1<0.95 . . . (1); −7.0<(fw*ft)1/2/f2<−4.8 . . . (2); 0.80<X4/X5<0.95 . . .

Abstract: The invention relates to an electronic imaging system such a video camera or digital camera, whose thickness or size is reduced while performance degradation is reduced as much as possible. The system comprises a zoom lens system comprising a first G1, a second G2, a third G3 and a fourth lens group G4 and an aperture stop S, and an electronic image pickup device located on its image side I and covered with a cover glass CG. The image of a subject is formed on the photoreceptive surface of the electronic image pickup device for conversion into electric signals. The system satisfies the following conditions (1) and (2).

Abstract: The invention relates to a high-performance, large-aperture yet wide-angle zoom lens system that can be used with an electronic image pickup device in particular, a method for focusing the same. In particular, the invention is concerned with a high-performance, large-aperture yet wide-angle zoom lens system which has a zoom ratio of the order of 3 at a diagonal field angle of 75° at its wide-angle end, so that it can be used with a single-lens reflex camera using an electronic image pickup device with the number of pixels being of the order of 6,000,000. The zoom lens system comprises a first lens group G1 having negative refracting power, a second lens group G2 having positive refracting power, a third lens group G3 having negative refracting power, a fourth lens group G4 having positive refracting power and a fifth lens group G5 having positive refracting power. Upon movement of an object point, focusing is carried out with the fifth lens group G5.

Abstract: In the zoom lens apparatus, a lens frame for a variable-magnification lens or a correcting lens is configured of an inner frame and an outer frame, and any focus blurring due to variations in wavelength of subject light can be compensated for accurately by shifting the inner frame holding the lens relative to the outer frame. The correcting lens frame for the correcting lens is configured of the inner frame and the outer frame, and the inner frame is shifted according to variations in wavelength of subject light. Any focus blurring can be thereby compensated for steplessly according to variations in wavelength of subject light.

Abstract: A zoom lens having only four lens groups is disclosed. In order from the object side, these are: a first lens group having positive refractive power, a second lens group having negative refractive power that moves for zooming, a third lens group having negative refractive power that moves for correcting a shift in the image surface position when zooming, and a fourth lens group having positive refractive power and formed of front and rear subgroups, with the rear subgroup consisting of a single positive lens element that moves to correct for different back focus lengths that are required when the zoom lens is used in different television cameras. Various conditions are preferably satisfied in order to maintain favorable correction of spherical aberration and astigmatism even when the back focus of the zoom lens is adjusted slightly so as to compensate for manufacturing tolerances.

Abstract: A zoom leas includes a first lens unit of a negative optical power and a second and third lens unit each of a positive optical power. The second lens unit consists of a first and second lens sub unit, each of a positive optical power arranged respectively on an object side and an image side. Zooming is effected by moving the lens units such that the distance between the first and second lens unit is smaller at a telephoto end than at a wide-angle end and that the distance between the second and third lens unit is larger. Focusing is effected by moving the second lens sub unit or the third lens unit where, when focusing on an object at infinity, the distance between the first lens sub unit and the second lens sub unit and the focal length of the entire system satisfy a predetermined condition.

Abstract: A zoom lens includes a first to fourth lens unit. Zooming is performed by moving the lens units so that a spacing between the first and the second lens unit at a telephoto end is larger than the spacing between the first and the second lens unit at a wide-angle end, and so that the spacing between the third and the fourth lens unit at the telephoto end is smaller than the spacing between the third and the fourth lens unit at the wide-angle end. If focal lengths of the first and the fourth lens units are f1 and f4, and if the focal length of entire system at the wide-angle end and the focal length of the entire system at the telephoto end are fw and ft, conditions expressed by 0.2<f1/ft<0.5, −0.2<f4/ft<−0.05 and 3.7<ft/fw<6.0 are satisfied.

Abstract: A zoom lens system includes a first lens group, a second lens group, a third lens group, and a fourth lens group. Zooming is performed by moving each of the first through fourth lens groups in the optical axis direction, and the zoom lens system satisfies the following conditions: 1.1<f23T/f23W<1.8  (1) 0.2<LD23W/fw<0.45  (2) 0.01<(D23W−D23T)/fT<0.

Abstract: A three-group zoom lens includes, in order from the object side, a first lens group of negative refractive power, and second and third lens groups, each of positive refractive power. The first and second lens groups include negative and positive components and the third lens group is a single lens component. All the lens components may be single lens elements. When zooming from the wide-angle end to the telephoto end, the second and third lens groups move toward the object side and all three lens groups move such that the group spacings decrease. The second lens group includes a diaphragm on its object side. A constant axial spacing between the second and third lens groups is maintained when zooming while the zoom lens is focused at infinity, and the third lens group is moved toward the object side when focusing from infinity to a near point.

Abstract: The invention relates to a zoom lens that has high optical performance specifications such as high zoom ratios, wide angles of view, reduced F-numbers and limited aberrations, and enables an optical path to be easily bent. The zoom lens comprises a moving lens group B(G2) that has positive refracting power and moves only toward the object side upon zooming from the wide-angle end to the telephoto end, and a lens group A(G1) remaining fixed during zooming, which is located on the object side of the zoom lens with respect to the moving lens group B and has negative refracting power. The moving lens group B is composed of, in order from its object side, a positive lens element, a positive lens element and a negative lens element, three lens elements in all.

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: The invention relates to a zoom lens with an easily bendable optical path, which has high optical specification performance such as a high zoom ratio, a wide-angle arrangement, a small F-number and reduced aberrations. The zoom lens comprises a first lens group G1 that remains fixed during zooming, a second lens group G2 that has negative refracting power and moves during zooming, a third lens group G3 that has positive refracting power and moves during zooming, and a fourth lens group G4 that has positive refracting power and moves during zooming and focusing. The first lens group comprises, in order from an object side thereof, a negative meniscus lens component convex on an object side thereof, a reflecting optical element for bending an optical path and a positive lens. Upon focusing on an infinite object point, the fourth lens group G4 moves in a locus opposite to that of movement of the third lens group G3 during zooming.

Abstract: A compact zoom lens system maintains sufficient image-formation capabilities at a wide-angle end of greater than 700 and at a zoom ratio of greater than about 10. The zoom lens system comprises a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group. For zooming from a wide-angle end to a telephoto end, the first to fifth lens groups are all movable. The first and third lens groups move toward the object side. Also, the spaces between the first and second lens groups and between the third and fourth lens groups widen. At least the fourth lens group or the fifth lens group makes a non-linear movement, compensating for a fluctuation of an image plane position with zooming. Focusing is carried out by moving the first and second lens groups as an integral unit.

Abstract: The invention relates to a microscope zoom objective lens system having improved optical performance, and comprising a compact optical system with a zoom ratio of at least 3. The microscope zoom objective lens system comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power and a third lens group G3 having positive refractive power. For zooming from a low to a high magnification side, the second and third lens groups G2 and G3 move along the optical axis while the separation between the first lens group G1 and the second lens group G2 becomes wide and the separation between the second lens group G2 and the third lens group G3 becomes narrow. The first lens group G1 comprises at least one doublet having positive refractive power and consisting of a positive lens and a negative lens. The positive lens has an Abbe number defined by &ngr;>80.

Abstract: A three-group zoom lens is provided of negative, positive, and positive refractive power, respectively, in the order from the object side. The first lens group is formed of a negative lens element and a positive lens element, the second lens group includes a stop for controlling the brightness of an image, two positive lens elements, and a negative lens element, and each lens group includes at least one aspherical surface. When zooming from the wide-angle end to the telephoto end, the first lens group is moved nearer the second lens group, and said second and third lens groups are moved continuously toward the object side. When focusing from an object at infinity to an object nearby, the third lens group is moved toward the object side. Specified conditions are satisfied in order to ensure that the exit pupil is an appropriate distance from the image plane for efficient light detection, while providing a zoom lens having an FNO of approximately 2.8 or less and a zoom ratio of 2.

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 comprises a first lens unit having positive refractive power, a second lens unit having negative refractive power, an aperture stop, a third lens unit having positive refractive power and kept fixed during zooming, a fourth lens unit having positive refractive power, and a fifth lens unit having negative refractive power, which are arranged in this order from an object side. In zooming from a wide-angle end to a telephoto end, the second lens unit is moved toward an image plane side such that a spacing between the first lens unit and the second lens unit is increased, and the aperture stop is also moved.

Abstract: A zoom lens system has, from an enlargement side, a first lens unit having a negative optical power, a second lens unit having a positive optical power and disposed on the image side of the first lens unit with a first variable distance secured in between, a third lens unit having a positive optical power and disposed on the image side of the second lens unit with a second variable distance secured in between, a fourth lens unit having a negative optical power, disposed on the image side of the third lens unit with a third variable distance secured in between, and including an aperture stop, a fifth lens unit having a positive or negative optical power and disposed on the image side of the fourth lens unit with a fourth variable distance secured in between, and a sixth lens unit having a positive optical power and disposed on the image side of the fifth lens unit with a fifth variable distance secured in between. Zooming is achieved by varying the first to fifth variable distances.

Abstract: A zoom lens system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. When the lens system is changed from a wide-angle end to a telephoto end, each lens group is moved to the object side such that the separation between the first lens group and the second lens group increases, the separation between the second lens group and the third lens group decreases, and the separation between the third lens group and the fourth lens group decreases. The fourth lens group is composed of four lens elements arranged, in order from the object, a first positive lens element, a first negative lens element, a second positive lens element, and a second negative lens element.

Abstract: The invention relates to a zoom lens system which has a higher wide angle a high zoom ratio with well-corrected aberrations, is fast, and has a large back focus. The zoom lens comprises, in order from its object side, a first lens group G1 having positive refracting power, a second lens group G2 having negative refracting power, a third lens group G3 having positive refracting power and a fourth lens group G4 having positive refracting power. For zooming from a wide-angle end to a telephoto end of the zoom lens system, the second lens group G2 moves toward an image side of the zoom lens system, the third lens group G3 moves toward the object side and the fourth lens group moves toward the object side. A lens located nearest to the image side in the third lens group G3 is a negative lens concave with respect to an image plane of the zoom lens system and a lens located nearest to the object side in the fourth lens group G4 is a negative lens concave with respect to an object.

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 for variation of magnification, a third lens unit for compensating for shift of an image plane caused by the variation of magnification, and a fixed fourth lens unit of positive refractive power, wherein the first lens unit comprises a first lens subunit of negative refractive power fixed during focusing, a second lens subunit having a focusing function, and a third lens subunit of positive refractive power fixed during focusing, and at least one of the first lens subunit and the second lens subunit and the third lens subunit respectively have aspheric lenses.

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: Taking lens device has zoom lens system comprised of plurality of lens units and achieves zooming by varying unit-to-unit distances and image sensor that converts optical image formed by zoom lens system into electrical signal. Zoom lens system comprised of, from the object side, first lens unit having negative optical power, second lens unit having positive optical power, and third lens unit having positive optical power. First, second, and third lens units are each comprised of one lens element, and at least the first and second lens units are moved along the optical axis during zooming. Following conditional formula is fulfilled: 0.2<tW2-3/fW<1.2, where tW2-3 represents optical path length from the most image-side lens surface in second lens unit to the most object-side lens surface in third lens unit at wide-angle end, and fW represents focal length of the entire zoom lens system at wide-angle end.

Abstract: The invention relates to a zoom lens including four lens groups. Starting from the side near objects, the first lens group is a positive refractive power lens group, the second a negative refractive power lens group, the third a positive refractive power lens group, and the fourth a positive refractive power lens group. When the zoom lens varies from the short focal length (wide angle) to the long focal length (telephone lens), the first lens group is fixed, the second lens group is moved from the object plane (closest to the object on the lens) to the image plane, the third and the fourth lens groups are independently moved from the image plane to the object plane to compensate for the image plane shift of the second lens group. Therefore, a clear image can be formed on the image plane even when the zoom lens focuses on objects at different distances. Each of the third and the fourth lens groups contains at least on aspherical 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: The invention provides a zoom lens system much more reduced in size and cost than ever before and best-suited for use on portable information terminals of small size. The zoom lens system comprises, in order from an object side thereof, a first lens group G1 having positive refracting power and designed to be fixed during zooming, a second lens group G2 having negative refracting power and designed to move from the object side to an image plane side of the system for zooming from a wide-angle end to a telephoto end of the system, a third lens group having refracting power and designed to move from the image plane side to the object side for zooming from the wide-angle end to the telephoto end, and a fourth lens group G4 having positive refracting power and designed to be movable during zooming.

Abstract: An object is to reduce damage to the mechanical parts of a moving mechanism unit 5 for moving a retaining mechanism unit 7 and electric power consumption in an apparatus for taking out a molded product. The apparatus comprises a time measuring unit 4 for measuring a return time elapsing between a start of the returning operation of the retaining mechanism unit 7 in a preceding process and the next start of the penetrating operation for taking out a molded product; an arithmetic operation unit 11 for calculating a return moving speed distribution for a process succeeding the preceding process such that the returning operation terminates upon elapse of the return time measured by the time measuring means 4; and a control unit 12 for activating the moving mechanism unit 5 in such a way that the returning operation is carried out according to the return moving speed distribution in the succeeding process.

Abstract: A three-group zoom lens has, from an object side, a first group lens having a positive power, a second group lens having a negative power and a third group lens consisting of a positive lens. The second lens group includes an aperture stop. When a distance to be focused is infinity, only the first lens group and the second lens group move for zooming. At least one positive lens included in the zoom lens has an aspherical surface whose positive power is greater at a portion farther from an optical axis thereof. The zoom lens satisfies the following conditions: −0.85<f2/f1<−0.65 and 5.0<f3/fw<8.0  where, fw represents a focal length when positioned at a wide-extremity, and f1, f2 and f3 respectively represent focal lengths of the first, second and third lens groups.

Abstract: A zoom lens including a second, third and fourth lens groups (12, 13 and 14) wherein at least one surfaces of the first to fourth lens groups has an aspherical surface, wherein the following relations are satisfied: 9.0<f1/fw<10.5 1.2<|f2/fw|<1.6 4.5<f3/fw<6.0 4.0<f4/fw<5.5 where f1 is a composed focal length of the first lens group, f2 is a composed focal length of the second lens group, f3 is a composed focal length of the third lens group, f4 is a composed focal length of the fourth lens group, and fw is a composed focal length of the entire system at a wide-angle end. Thereby, a compact zoom lens having an excellent aberration performance and a high zoom ratio of 20 times or more can be realized.

Abstract: A zoom lens system includes a first lens group, a second lens group, a third lens group, and a fourth lens group.

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: 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 a variation of magnification, a third lens unit arranged to move during a variation of magnification, and a fourth lens unit of positive refractive power, the first lens unit including a first lens subunit of negative refractive power, a second lens subunit of positive refractive power arranged to move during focusing, and a third lens subunit of positive refractive power, wherein the zoom lens satisfies the following conditions: 1.95<&dgr;&bgr;1+&dgr;&bgr;24<2.05 2<|f12/f11|<4.

Abstract: A real image mode finder optical system includes an objective optical system with a positive refracting power, an image erecting optical system having a plurality of reflecting sections for erecting an image formed by the objective optical system, and an ocular optical system for introducing an erected image into an observer's eye. At least one lens of the objective optical system or the ocular optical system is configured to be rotational asymmetrical with respect to the optical axis, and a light-blocking member for blocking reflected light at the end face of the lens is provided adjacent to the lens or spaced away therefrom through air.

Abstract: A zoom lens includes, in order from the object side, a first lens unit with positive refracting power, a second lens unit with negative refracting power, a third lens unit with positive refracting power, and a fourth lens unit with positive refracting power. At least, the second lens unit and the fourth lens unit are moved along the optical axis to change spaces between individual lens units, and thereby the magnification of the zoom lens is changed in the range of the wide-angle position to the telephoto position. In this case, the third lens unit has three positive lens elements and one negative lens element located at the most image-side position.

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 for variation of magnification, a third lens unit for compensating for shift of an image plane caused by the variation of magnification, and a fixed fourth lens unit of positive refractive power, wherein the first lens unit comprises a first lens subunit of negative refractive power fixed during focusing, a second lens subunit having a focusing function, and a third lens subunit of positive refractive power fixed during focusing, and at least one of the first lens subunit and the second lens subunit and the third lens subunit respectively have aspheric lenses.

Abstract: A negative-lead type zoom lens has a diffractive optical element and is led by a lens unit having a negative optical power. In this zoom lens, various kinds of aberration including chromatic aberration are excellently corrected by properly setting the lens configuration of each lens unit so as to achieve high optical performance over the entire range of a variable power while the entire lens system is miniaturized and designed to have a wide angle. The zoom lens according to the present invention is suitable for a zoom lens with a wide angle including a wide-angle region that is a focal length of substantially 28 mm on a 35 mm single lens reflex camera basis.

Abstract: A zoom lens includes a first lens group (1) having a positive refracting force that is fixed, a second lens group (2) having a negative refracting force that is movable along an optical axis and provided with a function of varying magnification, a third lens group (3) having a positive refracting force that is fixed, and a fourth lens group (4) having a positive refracting force that is movable along an optical axis and provided with a function of correcting fluctuations of an image plane resulting from varying magnification or changing an object distance (4), the first, second, third and fourth lens groups being disposed from an object side in this order, wherein the third lens group (3) and the fourth lens group (4) both include a positive glass spherical lens (L5, L8) and a plastic aspherical lens (L6, L7) having weaker refracting power. Thus, a compact zoom lens having a high magnification ratio of 20 times can be obtained at low cost.

Abstract: An ocular zoom lens is formed of three lens groups, of positive, positive, and negative refractive power, in order from the eye-point side. The second and third lens groups are moved along the optical axis in opposite directions during zooming, and the second lens group is formed of, in order from the eye-point side, a biconvex lens and a negative meniscus lens with its concave surface on the eye-point side, with the surfaces of the biconvex lens and the negative meniscus lens that face one another having different radii of curvature and being positioned on-axis with an intervening air space. Various conditions are preferably satisfied in order to ensure sufficient eye relief using a relatively small number of lens elements while providing increased freedom of design and enabling favorable correction of aberrations even for wide image angles.

Abstract: An optical system includes a diffractive optical element in which a phase given to incident light from an optical axis toward the peripheral part in the radial direction is not reversed in an effective area and an absolute value of optical power on the optical axis is made minimum. In the optical system, chromatic aberration of magnification of a high order is satisfactorily corrected and flare caused by additional diffraction light (unnecessary diffraction light) is suppressed to as minimum as possible while maintaining a high imaging performance up to peripheral part of a field angle.

Abstract: A wide-angle zoom lens is disclosed having five lens groups of negative, positive, positive, negative, and positive refractive power, respectively, in sequential order from the magnification side. The first lens group is fixed during zooming and is formed of first and second subgroups, each of negative refractive power. Each subgroup moves relative to the other subgroup, as well as along the optical axis, during focusing. Further, the second, third and fourth lens groups are each moved along the optical axis such that the spacing between these lens groups varies for zooming and correction of what would otherwise be excessive curvature of field caused by zooming, and the fifth lens group is fixed during zooming. Various conditions are satisfied so as to favorably correct aberrations, provide an image angle of about 70° at the wide-angle end, and provide room on the reducing side for the insertion of a beam-combining prism.

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 concave surface or plane directed onto the object side, and a lens having a negative refracting power.

Abstract: A projection zoom lens includes 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, which are arranged in that order from a screen side toward an image plane side along an optical axis. The first and the fourth lens group are kept stationary, and the second and the third lens group are moved along the optical axis to vary power from a limit wide angle power toward a limit telephoto power. The second lens group includes a 2nd-group 1st positive lens, a 2nd-group 1st compound lens formed by joining a 2nd-group 2nd positive lens having a convex surface on the image plane side and a 2nd-group 1st negative lens having a concave surface on the screen side, and a 2nd-group 3rd positive lens arranged in that order from the screen side toward the image plane side.

Abstract: The invention relates to a compact zoom lens system which can be applied to a relatively large image pickup device and can maintain sufficient image-formation capability even at a wide-angle end of 70° or greater and a zoom ratio of about 10 or greater. The zoom lens system comprises a first lens group G1 having positive refracting power, a second lens group G2 having negative refracting power, a third lens group G3 having positive refracting power, a fourth lens group G4 having negative refracting power and a fifth lens group G5. During zooming from the wide-angle end to the telephoto end of the system, the lens groups G1 to G5 are all moving.

Abstract: A variable focal length lens system with an angle of view of more than 80 in the wide-angle end state capable to focusing to a near distant object is provided. According to one aspect, a variable focal length lens system includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a negative refractive power. When the state of lens positions is changed from a wide-angle end state to a telephoto end state, all the lens groups are moved to the object side such that the interval between the first lens group G1 and the second lens group G2 increases, the interval between the second lens group G2 and the third lens group G3 decreases, and the interval between the third lens group G3 and the fourth lens group G4 decreases.

Abstract: The invention relates to a projection lens comprising a lens assembly that has at least one first narrowing of the group of light beams. A lens with a non-spherical surface is located in front of and/or behind the first narrowing.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a negative third lens group. Zooming is performed by moving the first through third lens groups in the optical axis direction.

Abstract: A zoom lens system which includes a positive first lens group, a positive second lens group, and a negative third lens group, in this order from the object, and in which each of the three lens groups is independently moved, along the optical axis, upon zooming so that the distances therebetween become shorter; and the zoom lens system satisfies the following condition: 0.03<(d12W−d12T)/fW<0.15  (1) wherein d12W designates the distance between the most image-side surface of the first lens group and the most object-side surface of the second lens group, at the short focal length extremity; d12T designates the distance between the most image-side surface of the first lens group and the most object-side surface of the second lens group, at the long focal length extremity; and fW designates the focal length of the entire zoom lens system at the short focal length extremity.

Abstract: A lens barrel is provided with a front lens group facing a subject, that moves only during zooming, and an internal focusing lens group, different from the front lens group, moving at least during focusing. A first cam ring having a cam groove for causing the front lens group to move, and a second cam ring that is separate from the first cam ring, is driven by the same drive source as the first cam ring, rotates together with the first cam ring, and has a cam groove for causing lens groups other than the front lens group to move, are also provided.