Abstract: A reflecting telescope optical system comprises, a main reflecting mirror, a sub reflecting mirror which is disposed at a position facing a reflecting surface of the main reflecting mirror, and a plurality of lens units which is disposed at a position facing a reflecting surface of the sub reflecting mirror. The reflecting surface of the main reflecting mirror is a concave surface, and a reflecting area is formed to be ring-shaped. The reflecting surface of the main reflecting mirror and the reflecting surface of the sub reflecting mirror are mutually facing. The first operation is a movement for focusing at an object positioned between infinity and a near position, and the second operation is a reciprocating movement for changing the focused state after focusing. An amount of movement in the first operation is larger than an amount of movement in the second operation.

Abstract: A zoom lens comprising, in order from the object side to the 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 positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power, wherein the first lens unit is located closest to the object side, the fifth lens unit is located closest to the image side, during zooming from the wide angle end to the telephoto end, the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit move, the fifth lens unit is stationary, and the distances between the lens units vary, the third lens includes a positive lens, and the zoom lens satisfies the following condition (1): 72<?3p<110??(1).

Abstract: A zoom lens comprising, in order from the object side to the 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 positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power, wherein the first lens unit is located closest to the object side, the fifth lens unit is located closest to the image side, during zooming from the wide angle end to the telephoto end, the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit move, the fifth lens unit is stationary, and the distances between the lens units vary, the third lens includes a positive lens, and the zoom lens satisfies the following condition (1): 72<?3p<110??(1).

Abstract: An inner focus lens system includes from the object side, a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power, and a third lens unit. The first lens unit includes a plurality of negative lenses and at least one positive lens, the lens located closest to the object side is a negative lens. The second lens unit includes at least one negative lens and at least one positive lens, and moves toward the object side for focusing from an infinite object distance to a close object distance such that the distance between the second lens unit and the aperture stop decreases and that the distance between the second lens unit and the third lens unit increases. The lens system satisfies the following conditions: 1<f1/f 14 (1), and 0.8<f23/f2<3 (2).

Abstract: A reflecting telescope optical system comprises, a main reflecting mirror, a sub reflecting mirror which is disposed at a position facing a reflecting surface of the main reflecting mirror, and a plurality of lens units which is disposed at a position facing a reflecting surface of the sub reflecting mirror. The reflecting surface of the main reflecting mirror is a concave surface, and a reflecting area is formed to be ring-shaped. The reflecting surface of the main reflecting mirror and the reflecting surface of the sub reflecting mirror are mutually facing. The first operation is a movement for focusing at an object positioned between infinity and a near position, and the second operation is a reciprocating movement for changing the focused state after focusing. An amount of movement in the first operation is larger than an amount of movement in the second operation.

Abstract: A zoom lens comprising, in order from an object side thereof, a first lens group of positive refracting power, a second lens group of negative refracting power, an aperture stop, a third lens group of positive refracting power, a fourth lens group of negative refracting power, and a fifth lens group of positive refracting power. Upon zooming from the wide-angle end to the telephoto end, at least the first lens group and the aperture stop remain fixed in position, the second and third lens groups move in the optical axis direction, and the separation between each of the lens groups and the aperture stop changes. Upon focusing from a focusing-on-infinity state to a close-range-focusing state, the fourth lens group moves in the optical axis direction, with satisfaction of the following: ?0.36<f4/f1<?0.05??(1A), where fl and f4 are the focal lengths of the first and fourth lens groups, respectively.

Abstract: A two-unit zoom lens system which forms an image on an image pickup surface, includes in order from an object side to an image side, a first lens unit G1 having a negative refracting power and a second lens unit G2 having a positive refracting power. At the time of zooming from a wide angle end to a telephoto end, a distance between the first lens unit and the second lens unit is narrowed. The first lens unit includes in order from the object side to the image side, a first lens having a negative refracting power, a second lens having a negative refracting power, and a third lens having a positive refracting power, and the two-unit zoom lens system satisfies predetermined conditional expressions.

Abstract: A zoom lens comprising, in order from an object side thereof, a first lens group of positive refracting power, a second lens group of negative refracting power, an aperture stop, a third lens group of positive refracting power, a fourth lens group of negative refracting power, and a fifth lens group of positive refracting power. Upon zooming from the wide-angle end to the telephoto end, at least the first lens group and the aperture stop remain fixed in position, the second and third lens groups move in the optical axis direction, and the separation between each of the lens groups and the aperture stop changes. Upon focusing from a focusing-on-infinity state to a close-range-focusing state, the fourth lens group moves in the optical axis direction, with satisfaction of the following: ?0.36<f4/f1<?0.05??(1A), where f1 and f4 are the focal lengths of the first and fourth lens groups, respectively.

Abstract: A two-unit zoom lens system which forms an image on an image pickup surface, includes in order from an object side to an image side, a first lens unit G1 having a negative refracting power and a second lens unit G2 having a positive refracting power. At the time of zooming from a wide angle end to a telephoto end, a distance between the first lens unit and the second lens unit is narrowed. The first lens unit includes in order from the object side to the image side, a first lens having a negative refracting power, a second lens having a negative refracting power, and a third lens having a positive refracting power, and the two-unit zoom lens system satisfies predetermined conditional expressions.

Abstract: The invention relates to a focus detection optical system for digital single-lens reflex cameras or the like and an imaging apparatus incorporating the same. A pupil division optical system comprises an aperture stop having a pair of openings with an optical axis of said taking lens held between them, and a pair of re-imaging lenses, each consisting of a double-convex lens having a convex entrance-side surface and a convex exit-side surface.

Abstract: The invention concerns an optical system adapted to split an optical path from a taking optical system into a finder optical system, which has a camera-shake correction function best suited for the finder optical system, and so on. This optical system comprises a taking optical system and a finder optical system. The taking optical system comprises an optical path splitter means operable to split an optical path into the finder optical system, and the finder optical system includes a relay optical system RLS for re-forming a subject image once. Anti-shake is implemented by shifting an optical subsystem RL that forms a part of the finder optical system in a plane vertical to an optical axis.

Abstract: The invention concerns an optical system adapted to split an optical path from a taking optical system into a finder optical system, which has a camera-shake correction function best suited for the finder optical system, and so on. This optical system comprises a taking optical system and a finder optical system. The taking optical system comprises an optical path splitter means operable to split an optical path into the finder optical system, and the finder optical system includes a relay optical system RLS for re-forming a subject image once. Anti-shake is implemented by shifting an optical subsystem RL that forms a part of the finder optical system in a plane vertical to an optical axis.

Abstract: The invention relates to a focus detection optical system for digital single-lens reflex cameras or the like and an imaging apparatus incorporating the same. A pupil division optical system comprises an aperture stop having a pair of openings with an optical axis of said taking lens held between them, and a pair of re-imaging lenses, each consisting of a double-convex lens having a convex entrance-side surface and a convex exit-side surface.

Abstract: The invention relates to an imaging system equipped with an electronic viewfinder suitable for compactness and having a sufficient angle of viewing field and satisfactory optical performance, especially the ability to prevent harmful light. The imaging system comprises an image pickup optical system, an image pickup device for receiving a light beam guided by the image pickup optical system, an image display device for displaying an image thereon, a controller for converting image information obtained from the image pickup device into signals capable of being displayed on the image display device, and a viewing optical system for guiding an image appearing on the image display device to a viewer's eye. The viewing optical system comprises, in order from an image display device side, one negative lens and one positive lens.

Abstract: A zoom lens system comprises, in order from an object side, positive, negative, positive, negative, and positive refractive power lens groups, and while changing the magnification, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fifth lens group increases, and the second lens group moves more towards the object side at the telephoto end than the wide-angle end.

Abstract: The invention concerns an optical system adapted to split an optical path from a taking optical system into a finder optical system, which has a camera-shake correction function best suited for the finder optical system, and so on. This optical system comprises a taking optical system and a finder optical system. The taking optical system comprises an optical path splitter means operable to split an optical path into the finder optical system, and the finder optical system includes a relay optical system RLS for re-forming a subject image once. Anti-shake is implemented by shifting an optical subsystem RL that forms a part of the finder optical system in a plane vertical to an optical axis.

Abstract: A finder optical system includes an eyepiece optical system with a positive refracting power. The eyepiece optical system includes an optical unit with a positive refracting power and a lens unit with a positive refracting power, In the eyepiece optical system, a refracting surface that is located most distant from an eyepoint of the eyepiece optical system has a positive refracting power and is configured as an aspherical surface with a negative refracting power on a periphery thereof.

Abstract: A zoom lens system comprises, in order from an object side, positive, negative, positive, negative, and positive refractive power lens groups, and while changing the magnification, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fifth lens group increases, and the second lens group moves more towards the object side at the telephoto end than the wide-angle end.

Abstract: A finder optical system includes an eyepiece optical system with a positive refracting power. The eyepiece optical system includes an optical unit with a positive refracting power and a lens unit with a positive refracting power, In the eyepiece optical system, a refracting surface that is located most distant from an eyepoint of the eyepiece optical system has a positive refracting power and is configured as an aspherical surface with a negative refracting power on a periphery thereof.

Abstract: A real image mode finder optical system is constructed to be independent of a photographing optical system and includes, in order from the object side, an objective optical system with a positive refracting power, a field frame located in the proximity of the imaging position of the objective optical system, and an eyepiece optical system with a positive refracting power. The real image mode finder optical system has an image erecting means, and the focal length of the objective optical system can be made shorter than that of the eyepiece optical system. In this case, the real image mode finder optical system satisfies the following condition: 0.52<mh/fe<1 where mh is the maximum width of the field frame and fe is the focal length of the eyepiece optical system.