Abstract: A camera lens group including, a first lens having positive refractive power, a convex object-side surface and a concave image-side surface; a second lens having refractive power, a convex object-side surface and a concave image-side surface; a third lens having negative refractive power and a concave image-side surface; a fourth lens having positive refractive power, a convex object-side surface and a concave image-side surface; a fifth lens having refractive power, a convex object-side surface and a concave image-side surface; a sixth lens having positive refractive power, a concave object-side surface and a convex image-side surface; a seventh lens having refractive power; an eighth lens having refractive power and a convex image-side surface; a ninth lens having refractive power, a concave object-side surface and a convex image-side surface; and a tenth lens having negative refractive power, a concave object-side surface and a concave image-side surface.

Abstract: A lens including a first lens group including three positive singlets and an achromatic doublet for collecting all field rays received at the first lens group while making initial corrections of spherical and color aberrations, a second lens group including a near-symmetrical group including two positive meniscus elements and two negative meniscus elements, wherein the second lens group is configured to correct distortions, a third lens group including two positive lenses with an air gap disposed between the two positive lenses, wherein the third lens group is configured to correct field curvature and astigmatism and a fourth lens group including a triplet and a positive meniscus element, wherein the fourth lens group is configured to correct spherical, coma, axial color and lateral color aberrations, wherein the lens is disposed in an order of the first lens group, the second lens group, the third lens group and the fourth lens group.

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

Abstract: A telephoto lens having an entrance pupil of between 80 and 110 mm includes a lens head and a focusing component. The lens head, as a first optical assembly, consists of four lens elements with a refractive power sequence that alternates in the light direction. The focusing component is a second optical assembly made of at least two lens elements and has a relative aperture of between 1:4.5 and 1:7.

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

Abstract: The application discloses a camera lens assembly, and the lens assembly includes, sequentially from an object side to an image side along an optical axis: a first lens having a positive refractive power, an image side surface of which is a concave surface; a second lens having a refractive power; a third lens having a refractive power; a fourth lens having a refractive power; a fifth lens having a refractive power; a sixth lens having a positive refractive power, an object side surface of which is a concave surface; a seventh lens having a refractive power; and an eighth lens having a negative refractive power, an object side surface of which is a concave surface. A total effective focal length f of the camera lens assembly and an entrance pupil diameter EPD of the camera lens assembly satisfy f/EPD?2.0.

Abstract: The present disclosure relates to the technical field of optical lens and discloses a camera optical lens. The camera optical lens includes, from an object side to an image side: a first lens, a second lens having a positive refractive power, a third lens having a negative refractive power, a fourth lens, a fifth lens and a sixth lens. And the camera optical lens satisfies following conditions: ?5.00?f1/f3??2.50 and ?10.00?R5/R6??2.00, where f1 denotes a focal length of the first lens; f3 denotes a focal length of the third lens; R5 denotes a curvature radius of an object-side surface of the third lens; and R6 denotes a curvature radius of an image-side surface of the third lens. The camera optical lens of the present disclosure can achieve a high imaging performance while obtaining a low TTL.

Abstract: The present disclosure relates to the technical field of optical lens and discloses a camera optical lens. The camera optical lens includes, from an object side to an image side: a first lens having a positive refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, a fourth lens, a fifth lens and a sixth lens. And the camera optical lens satisfies following conditions: ?20.00?f2/f3??8.00 and 2.00?d3/d5?3.00, where f2 denotes a focal length of the second lens; f3 denotes a focal length of the third lens; d3 denotes an on-axis thickness of the second lens; and d5 denotes an on-axis thickness of the third lens. The camera optical lens of the present disclosure can achieve a high imaging performance while obtaining a low TTL.

Abstract: An optical system includes, in order from an object side to an image side, a first lens unit having positive refractive power, and a second lens unit having negative refractive power, wherein the first lens unit moves and the second lens unit does not move during focusing, wherein the first lens unit includes a positive lens arranged closest on the object side of the first lens unit, wherein the second lens unit includes three or more lenses including at least two negative lenses, wherein the first lens unit consists of a first subunit having positive refractive power, a second subunit having negative refractive power, and a third subunit having positive refractive power arranged in order from the object side to the image side, and wherein predetermined conditional expressions are satisfied.

Abstract: An optical system according to an example embodiment includes a first lens unit that has a positive refractive power, and a second lens unit that is disposed on an image side of the first lens unit and that has a positive refractive power. The second lens unit moves when focusing from infinity to an object at near distance. The second lens unit includes, disposed in order from the object side towards an image side, a first positive lens, an aperture stop, and a second positive lens. Anomalous partial dispersibilities of the first positive lens and the second positive lens are defined.

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

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

Abstract: A projection optical system (2) projects from a DMD (7) on a reducing side onto a screen (9) on an enlargement side, and includes: a first refractive optical system (10) that forms a first intermediate image (51) on the enlargement side using light incident from the reducing side; a second refractive optical system (20) that forms the first intermediate image (51) on the reducing side into a second intermediate image (52) on the enlargement side; and a first reflective optical system (30) including a first reflective surface (31a) with positive refractive power that is positioned on the enlargement side of the second intermediate image (52), wherein the second refractive optical system (20) includes a first focus lens group (61) that moves when focusing is carried out, and the first focus lens group (61) includes at least one lens (L13) included in the second refractive optical system (20).

Abstract: Provided is an optical system including, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power configured to move during focusing; and a third lens unit, wherein an interval between each pair of adjacent lens units is changed during focusing, wherein the first lens unit includes a positive lens arranged closest to the object side and an aperture stop, wherein the second lens unit consists of one negative lens, and wherein a distance on an optical axis from a lens surface closest to the object side in the optical system to an image plane, a focal length of the optical system, a refractive index of a material of the one negative lens, and an Abbe number of the material of the one negative lens are appropriately set.

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

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

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

Abstract: An imaging lens is constituted by, in order from the object side to the image side, a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a positive refractive power. The second lens group has at least one positive lens and at least one negative lens. The second lens group moves along the optical axis from the object side to the image side while the first lens group and the third lens group are fixed with respect to an image formation plane to change focus from an object at infinity to an object at a proximal distance. Predetermined Conditional Formulae (1) and (2) are satisfied.

Abstract: A projection optical system (2) projects from a DMD (7) on a reducing side onto a screen (9) on an enlargement side, and includes: a first refractive optical system (10) that forms a first intermediate image (51) on the enlargement side using light incident from the reducing side; a second refractive optical system (20) that forms the first intermediate image (51) on the reducing side into a second intermediate image (52) on the enlargement side; and a first reflective optical system (30) including a first reflective surface (31a) with positive refractive power that is positioned on the enlargement side of the second intermediate image (52), wherein the second refractive optical system (20) includes a first focus lens group (61) that moves when focusing is carried out, and the first focus lens group (61) includes at least one lens (L13) included in the second refractive optical system (20).

Abstract: An optical system SL installed in a single-lens reflex camera includes, in order from an object side, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. The second lens group G2 is disposed movably in a direction including a component perpendicular to an optical axis, and a given conditional expression is satisfied, thereby providing an optical system having excellent optical performance with excellent vibration reduction performance, an optical apparatus equipped with the optical system, and a method for manufacturing the optical system.

Abstract: A zoom lens consists of four or five lens groups, consisting of, in order from the object side, a positive first group a negative second group, one or two middle groups including a positive mp group, and a positive rearmost group at the most image-side position of the entire system. Zooming is effected by changing all distances between the adjacent groups. The rearmost group consists of, in order from the object side, a positive front group, a negative middle group, and a positive rear group. Air spaces between the front and middle groups, and between the middle and rear groups are constant during zooming and focusing. The front group includes two positive lenses and one negative lens. Image stabilization is effected by shifting the middle group perpendicularly to the optical axis. The rear group includes one positive lens and two negative lenses. The zoom lens satisfies a given condition expression.

Abstract: An imaging lens consists essentially of, in order from the object side, a first lens group having a positive refractive power, a stop, and a second lens group having a positive refractive power. The first lens group includes, in order from the object side, two successive positive lenses, and a negative lens having a concave surface toward the image side. The second lens group includes, in order from the object side, a lens having at least one aspheric surface, and a three-lens cemented lens. The three-lens cemented lens has a positive refractive power, and is formed by cementing three lenses consisting of, in order from the object side, a positive lens having a convex surface toward the image side, a negative lens, and a positive lens.

Abstract: An inner focus lens system comprising a first lens unit and subsequent lens units, wherein the first lens unit: is fixed with respect to an image surface in focusing; and includes a first positive lens element located closest to the object side and a second positive lens element, the subsequent lens units include only a first focusing lens unit located closest to the object side and a second focusing lens unit, at least one of the first focusing lens unit and the second focusing lens unit is composed of two or less lens elements, and the subsequent lens units include an image blur compensating lens unit.

Abstract: An imaging optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, an aperture stop, and a third lens unit having a positive refractive power. The second lens unit moves toward the image side during focusing from a far object to a near object. The third lens unit includes, in order from the object side to the image side, two lenses having concave surfaces that face each other with a largest air gap in the third lens unit provided therebetween, and a positive lens. A focal length of the entire imaging optical system and a focal length of the second lens unit are appropriately set.

Abstract: A telephoto lens system and an electronic apparatus having the same are provided. The telephoto lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group. The third lens group includes a (3-1)-th lens group having a positive refractive power, a (3-2)-th lens group having a negative refractive power, and a (3-3)-th lens group having a positive refractive power.

Abstract: An image forming lens system includes an aperture stop, and an image-side lens unit group which is disposed on an image side of the aperture stop. The image-side lens unit group includes a first image-side lens unit having a negative refractive power, a second image-side lens unit having a positive refractive power, and a third image-side lens unit having a negative refractive power. Any one of the first image-side lens unit, the second image side lens unit, and the third image-side lens unit is a focusing lens unit which moves along the optical axis at the time of focusing, and the following conditional expression (1) is satisfied: 0.06<|ffo/f|<0.4 ??(1) where, f denotes a focal length of the image forming lens system at the time of focusing at an object at infinity, and ffo denotes a focal length of the focusing lens unit.

Abstract: A compact telephoto lens system that may be used in a small form factor cameras. The lens system may include five lens elements with refractive power. Alternatively, the lens system may include four lens elements with refractive power. At least one of the object side and image side surfaces of at least one of the lens elements is aspheric. Total track length (TTL) of the lens system may be 6.0 mm or less. Focal length f of the lens system may be at or about 7.0 mm (for example, within a range of 6.5-7.5 mm). Lens elements are selected and configured so that the telephoto ratio (TTL/f) satisfies the relation 0.74<TTL/f<1.0. Materials, radii of curvature, shapes, sizes, spacing, and aspheric coefficients of the lens elements may be selected to achieve quality optical performance and high image resolution in a small form factor telephoto camera.

Abstract: A single focal length lens system includes a front lens unit having a positive refractive power, and a rear lens unit. The front lens unit includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and both the first lens unit and the second lens unit include a positive lens and a negative lens. The rear lens unit includes a focusing lens unit and a first predetermined lens unit. The first predetermined lens unit has a refractive power having a sign different from a refractive power of the focusing lens unit, and does not move at the time of focusing. The front lens unit does not include a lens which moves, and the rear lens unit does not include a lens which moves except at the time of focusing.

Abstract: A telephoto lens system including a first lens group having a positive refractive power and including a negative lens that is disposed closest to an object side and has a meniscus shape that is convex toward the object side; a second lens group having a negative refractive power and including a single negative lens that moves along an optical axis and performs focusing; and a third lens group having a positive refractive power, wherein the first through third lens groups are disposed sequentially from the object side toward the image side, and the telephoto lens system satisfies the following condition, 0.5<|f2/f|<0.81, wherein, f2 denotes the focal length of the second lens group, and f denotes the focal length of the telephoto lens system.

Abstract: An apparatus has a plate having a length, a width and an attachment interface, two clamping mechanisms, each having a cross piece fastened orthogonally to the elongated plate, a bumper block formed under the cross piece, an inflexible strap joined the cross piece on one side of the elongated plate, and a first tightening mechanism enabled to draw the strap joined to the cross piece on an opposite side of the elongated plate. The attachment interface allows the cross piece of the clamping mechanisms to be assembled at a plurality of different positions along the length of the elongated plate, such that a distance between the two clamping mechanisms is adjustable, allowing the clamping mechanisms to be joined to a tubular barrel at two different positions of equal or differing diameter.

Abstract: An apparatus has a plate having a length, a width and an attachment interface, two clamping mechanisms, each having a cross piece fastened orthogonally to the elongated plate, a bumper block formed under the cross piece, an inflexible strap joined the cross piece on one side of the elongated plate, and a first tightening mechanism enabled to draw the strap joined to the cross piece on an opposite side of the elongated plate. The attachment interface allows the cross piece of the clamping mechanisms to be assembled at a plurality of different positions along the length of the elongated plate, such that a distance between the two clamping mechanisms is adjustable, allowing the clamping mechanisms to be joined to a tubular barrel at two different positions of equal or differing diameter.

Abstract: A first lens group having positive refractive power and a second lens group are arranged in this order from an object side, and only the first lens group moves in the optical axis direction while focusing. The first lens group substantially consists of a positive 1-1 lens, a positive 1-2 lens, a positive 1-3 lens, a negative 1-4 lens, an aperture stop, a negative 1-5 lens, a positive 1-6 lens, and a positive 1-7 lens. The 1-3 lens and the 1-4 lens are cemented to each other, and the 1-5 lens and the 1-6 lens are cemented to each other. The second lens group substantially consists of a negative 2-1 lens and a positive 2-2 lens. Only the first lens group moves in the optical axis direction while focusing.

Abstract: A fixed-focus projection lens has a first lens group and a second lens group in sequence along an optical axis from a screen side to a light modulator side. The first lens group has a positive refractive power, and the second lens group has a positive refractive power. The first lens group has two lenses, and the refractive powers of the lenses are negative and positive. The second lens group has five lenses, and the refractive powers of the lenses respectively are negative, negative, positive, positive, and positive. The fixed-focus projection lens has the features of small size and high optical performance.

Abstract: A telephoto lens system includes a first lens group having a positive refractive power, and comprising at least three positive lenses and one negative lens; a second lens group having a negative refractive power, and which moves along an optical axis to perform a focusing operation; a third lens group having a positive refractive power, and comprising a cemented lens in which a positive lens having a convex surface toward the object side and a positive lens having a convex surface toward the image side are bonded to each other, a bi-convex positive lens, and a negative lens having a concave surface toward the object side, and the first through third lens groups are disposed sequentially from the object side to the image side.

Abstract: A telephoto lens system and an electronic apparatus having the same are provided. The telephoto lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group. The third lens group includes a (3-1)-th lens group having a positive refractive power, a (3-2)-th lens group having a negative refractive power, and a (3-3)-th lens group having a positive refractive power.

Abstract: A first lens group having positive refractive power and a second lens group are arranged in this order from an object side, and only the first lens group moves in the optical axis direction while focusing. The first lens group substantially consists of a positive 1-1 lens, a positive 1-2 lens, a positive 1-3 lens, a negative 1-4 lens, an aperture stop, a negative 1-5 lens, a positive 1-6 lens, and a positive 1-7 lens. The 1-3 lens and the 1-4 lens are cemented to each other, and the 1-5 lens and the 1-6 lens are cemented to each other. The second lens group substantially consists of a negative 2-1 lens and a positive 2-2 lens. Only the first lens group moves in the optical axis direction while focusing.

Abstract: An achromatic lens system is provided with a cemented resin lens having positive refractive power constructed by a resin lens L11 having positive refractive power cemented with a resin lens L12 having negative refractive power, and a close-contact multi-layer type diffractive optical element L11E, the diffractive optical element L11E being disposed to an image side of the cemented resin lens, the diffractive optical element L11E being constructed by cementing two diffractive element members DE11, DE12 each made of different optical materials with each other, and the cemented surface thereof being a diffractive optical surface Gf on which grooves of a diffraction grating are formed, there by being lightweight and easily manufactured, capable of excellently correcting chromatic aberration and spherical aberration at the same time.

Abstract: The disclosed internal focusing large-aperture medium telephoto lens has as lens groups a positive first lens group, a positive second lens group, and a third lens group, in that order from the object side. When focusing on nearby objects, the first lens group and the third lens group have a fixed position relative to the image surface, and the second lens group displaces toward the object side. The second lens group has only one negative lens, and, in order from the object side, has at least a positive lens, a negative lens, and a positive lens. The following expression is fulfilled: ?0.5<(R1+R2)(R1?R2)<?0.1 (wherein, R1: radius of curvature of the object side surface of the negative lens in the second lens group; R2: radius of curvature of the image side surface of the negative lens in the second lens group).

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, each lens unit being moved during zooming, wherein the second lens unit includes two positive lenses, a negative lens, a positive lens in order from the object side to the image side, and an average refractive index Nd2p for d-line of materials of the positive lenses in the second lens unit and a refractive index Nd2n for d-line of a material of the negative lens in the second lens unit are appropriately set.

Abstract: An image pickup optical system includes, in order from an object side to an image side, a first lens unit that does not move for focusing and has a positive optical power, a second lens unit that moves during focusing, an aperture diaphragm, and a third lens unit that does not move for focusing. The image pickup optical system includes a diffractive optical element, and an optical element NLF made of a solid material on the object side of an intersection between a paraxial chief ray and an optical axis. The predetermined conditional expressions are satisfied.

Abstract: A large-aperture telephoto lens system includes a positive first lens group, a negative second lens group, and a positive third lens group, in that order from the object side, wherein the second lens group serves as a focusing lens group which is moved during focusing on an object at infinity to an object at a finite distance, wherein the following conditions (1) and (2) are satisfied: ?4<f/f2<?3??(1), and 1.3<f/f3<2.3??(2), wherein f designates the focal length of the entire large-aperture telephoto lens system, f2 designates the focal length of the second lens group, and f3 designates the focal length of the third lens group.

Abstract: An imaging lens includes, sequentially from an object side, a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a negative refractive power. The third lens group is configured by a single lens element, and is moved along an optical axis, whereby focusing is performed.

Abstract: An optical system includes a first lens unit fixed during a focusing operation and having a positive refractive power, a second lens unit moving in an optical axis direction during the focusing operation and having a negative refractive power, a third lens unit positioned at the image side relative to the second lens unit and having a positive or negative refractive power, the first lens unit is configured by first, second, and third partial lens units, the first partial lens unit is configured by two positive lens components, the second partial lens unit is configured by one cemented lens having a negative combined refractive power, the third partial lens unit is positioned between the second partial lens unit and the second lens unit and has a positive refractive power as a whole, and each lens unit is configured so as to meet an appropriate condition.

Abstract: A reflective type telephoto lens and a photographing apparatus including the reflective type telephoto lens are provided. The reflective type telephoto lens includes: a first lens that receives an incident flux of light from an object side; a main mirror including a reflective unit that reflects light transmitted through the first lens toward the object side, and a transmission portion disposed on a center portion thereof; a sub-mirror group including a sub-mirror that reflects light from the main mirror toward an image side; and a focusing lens group that focuses the light reflected by the sub-mirror.

Abstract: An optical system for imaging an object on an image acquisition unit includes a first lens unit, a second lens unit, a third lens unit, a fourth lens unit, a fifth lens unit, and a sixth lens unit disposed from the object in the direction of the image acquisition unit. The second lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: ??g F>0.025. The third lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: ??g F<?0.0015. The fifth lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: ??g F<?0.005. According to the disclosed system, the secondary spectrum is reduced and a relative aperture is sufficient so that the optical system is usable in a telescopic sight.

Abstract: There is provided a zoom lens which is suitable for a digital still camera and a video camera and includes a small number of lenses, especially a zoom lens which has an angle of view of 75° or more at the wide-angle end and a variable power ratio of about ×10. The zoom lens includes a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and, a fourth lens group with positive refractive power. The zoom lens varies power by changing an interval of each neighboring lens groups. The first lens group is composed of a negative lens and a positive lens. The third lens group is composed of an aperture stop, a cemented lens formed by a positive lens in a biconvex shape and a negative lens, and a positive lens.

Abstract: A telephoto lens system including a first lens group having a positive refractive power and including a negative lens that is disposed closest to an object side and has a meniscus shape that is convex toward the object side; a second lens group having a negative refractive power and including a single negative lens that moves along an optical axis and performs focusing; and a third lens group having a positive refractive power, wherein the first through third lens groups are disposed sequentially from the object side toward the image side, and the telephoto lens system satisfies the following condition, 0.5<|f2/f|<0.81, wherein, f2 denotes the focal length of the second lens group, and f denotes the focal length of the telephoto lens system.

Abstract: A teleconverter includes a master lens apparatus-side mount on which a master lens apparatus is mounted, a camera body-side mount on which a camera body is mounted, and a converter lens unit that has a negative refracting power for mounting the master lens apparatus thereon to obtain a lens system having a focal length longer than that of the master lens apparatus, the converter lens unit including a first lens group on the master lens apparatus side and a second lens group on the camera body side with an on longest air separation interposed between them, the first lens group has positive refracting power, and the second lens group has negative refracting power, with satisfaction of the following condition (1): ?1.53<f1/f<?0.66??(1) where f is the focal length of a whole system of the converter lens unit, and f1 is the focal length of the first lens group.

Abstract: A tele-side converter lens including a first unit having a positive refractive power and a second unit having a negative refractive power, in which: the first unit includes one or two positive lenses; the second unit includes one negative lens and one or two positive lenses; and average Abbe constant and partial dispersion ratio of materials of positive lenses constituting the first unit, average Abbe constant and partial dispersion ratio of materials of positive lenses constituting the second unit, an Abbe constant and a partial dispersion ratio of materials of the negative lenses constituting the second unit, combined Abbe constants of materials of the lenses constituting the respective first and second units, focal lengths of the first and second units, a refractive index of a material of a positive lens disposed closest to the object side, and a magnification of the tele-side converter lens are appropriately set, respectively.

Abstract: A telephoto lens system includes a first lens group having a positive refractive power, and comprising at least three positive lenses and one negative lens; a second lens group having a negative refractive power, and which moves along an optical axis to perform a focusing operation; a third lens group having a positive refractive power, and comprising a cemented lens in which a positive lens having a convex surface toward the object side and a positive lens having a convex surface toward the image side are bonded to each other, a bi-convex positive lens, and a negative lens having a concave surface toward the object side, and the first through third lens groups are disposed sequentially from the object side to the image side.