Abstract: An attachment optical system detachably mounted between a lens system and an image pickup apparatus, includes: a receiver receiving first information for correcting lateral chromatic aberrations caused by the lens system; a computer deriving, based on the first information and optical characteristics of the attachment optical system, second information for correcting lateral chromatic aberrations; and a transmitter transmitting the second information to the image pickup apparatus, in which the first and second information include information for obtaining lateral chromatic aberration amounts under conditions of zoom, focus and f-number, based on ratio of image height to maximum image height, in which the first and second information indicate shift amounts of blue/red relative to green radially about optical axis, and in which the shift amounts of blue/red in the first information and in the second information are properly set as functions of ratio of image height to maximum image height.

Abstract: An attachment optical system detachably mounted between a lens system and an image pickup apparatus, includes: a receiver receiving first information for correcting lateral chromatic aberrations caused by the lens system; a computer deriving, based on the first information and optical characteristics of the attachment optical system, second information for correcting lateral chromatic aberrations; and a transmitter transmitting the second information to the image pickup apparatus, in which the first and second information include information for obtaining lateral chromatic aberration amounts under conditions of zoom, focus and f-number, based on ratio of image height to maximum image height, in which the first and second information indicate shift amounts of blue/red relative to green radially about optical axis, and in which the shift amounts of blue/red in the first information and in the second information are properly set as functions of ratio of image height to maximum image height.

Abstract: A zoom lens includes in order from an object side: a positive first lens unit; a negative second lens unit which moves during zooming; a third lens unit; a stop; and a positive fourth lens unit. The first lens unit includes, in order from the object side, a negative first lens subunit which does not move, a positive second lens subunit which moves during focusing, and a positive third lens subunit which does not move. The first lens subunit is composed of one or more negative lenses, and the second lens subunit includes a positive lens and a negative lens. An average value of Abbe constants of the first lens subunit, an average value of Abbe constants of the positive lenses of the second lens subunit, and an average value of Abbe constants of the negative lenses of the second lens subunit are appropriately set.

Abstract: A zoom lens includes in order from an object side: a positive first lens unit; a negative second lens unit which moves during zooming; a third lens unit; a stop; and a positive fourth lens unit. The first lens unit includes, in order from the object side, a negative first lens subunit which does not move, a positive second lens subunit which moves during focusing, and a positive third lens subunit which does not move. The first lens subunit is composed of one or more negative lenses, and the second lens subunit includes a positive lens and a negative lens. An average value of Abbe constants of the first lens subunit, an average value of Abbe constants of the positive lenses of the second lens subunit, and an average value of Abbe constants of the negative lenses of the second lens subunit are appropriately set.

Abstract: A zoom lens includes, in order from an object side, a positive first lens unit which does not move for zooming, a negative second lens unit which moves in an optical axis direction for zooming, a negative third lens unit which moves in the optical axis direction for zooming so as to correct image plane variation due to zooming, and a positive fourth lens unit which does not move for zooming. The fourth lens unit includes, in an order from the object side, a positive first sub lens unit and a positive second sub lens unit, which are separated by a largest air interval in the fourth lens unit. Abbe constants, partial dispersion ratios, and coefficients of the refractive index variation due to the temperature variation are appropriately set for lens materials forming the third lens unit, the first sub lens unit, and the second sub lens unit.

Abstract: A zoom lens system includes a first unit having a positive refractive power, a second unit having a negative refractive power that moves for magnification-varying, a third unit having one of a positive refractive power and a negative refractive power that moves for magnification-varying, and a fourth unit having a positive refractive power.

Abstract: A zoom lens includes, in order from an object side, a positive first lens unit which does not move for zooming, a negative second lens unit which moves in an optical axis direction for zooming, a negative third lens unit which moves in the optical axis direction for zooming so as to correct image plane variation due to zooming, and a positive fourth lens unit which does not move for zooming. The fourth lens unit includes, in an order from the object side, a positive first sub lens unit and a positive second sub lens unit, which are separated by a largest air interval in the fourth lens unit. Abbe constants, partial dispersion ratios, and coefficients of the refractive index variation due to the temperature variation are appropriately set for lens materials forming the third lens unit, the first sub lens unit, and the second sub lens unit.

Abstract: A zoom lens system includes a first unit having a positive refractive power, a second unit having a negative refractive power that moves for magnification-varying, a third unit having one of a positive refractive power and a negative refractive power that moves for magnification-varying, and a fourth unit having a positive refractive power.

Abstract: A zoom lens 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; a third lens unit having a negative refractive power; an aperture stop; and a fourth lens unit having a positive refractive power and including a front lens subunit and a rear lens subunit in which Abbe numbers of lenses in the rear lens subunit satisfy the following expression, 0.400<?m/(?rp??rn)<0.630, where ?m represents the Abbe number of the material of a first positive lens having the largest dispersion of the positive lenses included in the rear lens subunit, ?rp represents the average Abbe number of materials of positive lenses other than the first positive lens in the rear lens subunit, and ?rn represents the average Abbe number of materials of negative lenses in the rear lens subunit.

Abstract: A zoom lens 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; a third lens unit having a negative refractive power; an aperture stop; and a fourth lens unit having a positive refractive power and including a front lens subunit and a rear lens subunit in which Abbe numbers of lenses in the rear lens subunit satisfy the following expression, 0.400<?m/(?rp??rn)<0.630, where ?m represents the Abbe number of the material of a first positive lens having the largest dispersion of the positive lenses included in the rear lens subunit, ?rp represents the average Abbe number of materials of positive lenses other than the first positive lens in the rear lens subunit, and ?rn represents the average Abbe number of materials of negative lenses in the rear lens subunit.

Abstract: A zoom lens includes a focus unit, a zoom unit, an aperture stop, and an imaging unit having a splitting element that are arranged in that order from an object side to an image side. The splitting element includes an incident surface for a light beam, a half mirror surface for splitting the light beam into reflected light and transmitted light, a splitting exit surface from which the reflected light is emitted, and an exit surface from which the transmitted light is emitted. The incident surface and the exit surface are perpendicular to an optical axis of the zoom lens. The ratio of the distance from the aperture stop to the exit surface and the equivalent air length from the aperture stop to an image plane of the zoom lens and the ratio of the effective diameters of the exit surface and the splitting exit surface are set properly.

Abstract: A zoom lens includes a focus unit, a zoom unit, an aperture stop, and an imaging unit having a splitting element that are arranged in that order from an object side to an image side. The splitting element includes an incident surface for a light beam, a half mirror surface for splitting the light beam into reflected light and transmitted light, a splitting exit surface from which the reflected light is emitted, and an exit surface from which the transmitted light is emitted. The incident surface and the exit surface are perpendicular to an optical axis of the zoom lens. The ratio of the distance from the aperture stop to the exit surface and the equivalent air length from the aperture stop to an image plane of the zoom lens and the ratio of the effective diameters of the exit surface and the splitting exit surface are set properly.

Abstract: Disclosed is an image-taking lens system, with which the optimum image-forming position can be detected accurately regardless of whether an auxiliary lens system is inserted or not, and with little blurring of the image on the output screen during wobbling. The image-taking lens system includes a light amount adjustment stop; a relay lens unit having an image-forming action; a wobbling lens unit arranged within the relay lens unit, the wobbling lens unit being driven by an amplitude in an optical axis direction; and an auxiliary lens system which can be inserted into and removed from the relay lens unit, the auxiliary lens system shifting a focal length of the overall image-taking lens system. The amplitude by which the wobbling lens unit is driven is set depending on whether the auxiliary lens system is inserted or removed.

Abstract: A zoom lens in which a precise focus detection signal can be detected while a user can observe an image to be shoot without being affected by insertion/removal of an extender lens into an optical axis. A relay lens unit stationary during zooming includes lens unit L21 including a branch element, lens unit L22 interchangeable with extender lens unit insertable into/removable from optical path to change focal length range of the entire system and positive lens unit L23 in order from object side to image side, and the zoom lens satisfies specific conditions among distance from an aperture stop to front principal point of L21, distance from rear principal point of L21 to front principal point of L22, distance from rear principal point of L22 to front principal point of L23, refractive power of L21, and refractive power of the entire system of the zoom lens at wide-angle end.

Abstract: A zoom lens in which a precise focus detection signal can be detected while a user can observe an image to be shoot without being affected by insertion/removal of an extender lens into an optical axis. A relay lens unit stationary during zooming includes lens unit L21 including a branch element, lens unit L22 interchangeable with extender lens unit insertable into/removable from optical path to change focal length range of the entire system and positive lens unit L23 in order from object side to image side, and the zoom lens satisfies specific conditions among distance from an aperture stop to front principal point of L21, distance from rear principal point of L21 to front principal point of L22, distance from rear principal point of L22 to front principal point of L23, refractive power of L21, and refractive power of the entire system of the zoom lens at wide-angle end.

Abstract: A lens device having a function of varying a magnification of the lens device and a function of focusing includes, in the order from an object side to an image side, a first lens unit which has a positive optical power and which is fixed during the variation of magnification, a second lens unit which has a negative optical power and which moves during the variation of magnification, and a third lens unit which has a positive optical power and which is fixed during the variation of magnification. The third lens unit includes a first lens sub-unit which is fixed during focusing, a second lens sub-unit which has a positive optical power and which moves during focusing, and a third lens sub-unit which has a positive optical power and which is fixed during focusing, in that order from the object side to the image side.

Abstract: In a zoom lens in/from which a magnification changing optical unit for changing an overall focal length of the zoom lens can be inserted/removed, wherein a wobbling unit which can be slightly amplitude-driven in an optical axis direction to detect a best imaging position is placed closer to an image side than an insertion position of said magnification changing optical unit.

Abstract: A lens device having a function of varying a magnification of the lens device and a function of focusing includes, in the order from an object side to an image side, a first lens unit which has a positive optical power and which is fixed during the variation of magnification, a second lens unit which has a negative optical power and which moves during the variation of magnification, and a third lens unit which has a positive optical power and which is fixed during the variation of magnification. The third lens unit includes a first lens sub-unit which is fixed during focusing, a second lens sub-unit which has a positive optical power and which moves during focusing, and a third lens sub-unit which has a positive optical power and which is fixed during focusing, in that order from the object side to the image side.

Abstract: Disclosed is an image-taking lens system, with which the optimum image-forming position can be detected accurately regardless of whether an auxiliary lens system is inserted or not, and with little blurring of the image on the output screen during wobbling. The image-taking lens system includes a light amount adjustment stop; a relay lens unit having an image-forming action; a wobbling lens unit arranged within the relay lens unit, the wobbling lens unit being driven by an amplitude in an optical axis direction; and an auxiliary lens system which can be inserted into and removed from the relay lens unit, the auxiliary lens system shifting a focal length of the overall image-taking lens system. The amplitude by which the wobbling lens unit is driven is set depending on whether the auxiliary lens system is inserted or removed.

Abstract: In a zoom lens in/from which a magnification changing optical unit for changing an overall focal length of the zoom lens can be inserted/removed, wherein a wobbling unit which can be slightly amplitude-driven in an optical axis direction to detect a best imaging position is placed closer to an image side than an insertion position of said magnification changing optical unit.