A zoom lens forms an intermediate image at a position conjugate to a reduction side imaging plane and forms the intermediate image again on a magnification side imaging plane. The zoom lens includes a plurality of lens groups including at least two movable lens groups, which move by changing spacings between the groups adjacent to each other in a direction of an optical axis during zooming, at a position closer to the reduction side than the intermediate image. Among the plurality of lens groups, a final lens group closest to the reduction side has a positive refractive power, and remains stationary with respect to the reduction side imaging plane during zooming. The zoom lens satisfies predetermined conditional expressions (1) and (2) about the focal lengths of the movable lens groups.

A zoom lens includes a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power, in order from an object side to an image side. During zooming, the first lens unit is not moved, and the second lens unit, the third lens unit, and the fourth lens unit are moved to change an interval between adjacent lens units. A moving amount m2 of the second lens unit during zooming from a wide angle end to a telephoto end, a focal length f2 of the second lens unit, and a focal length fw of a whole system at the wide angle end are each set appropriately.

A variable magnification optical system consists of a first lens-group having negative refractive-power, a stop and a second lens-group having positive refractive-power in this order from an object-side. The first lens-group includes an L11 negative meniscus lens, an L12 negative lens and a C11 cemented lens, in which a biconcave lens and a positive lens are cemented together in this order from the object-side, in this order from the object-side. The second lens-group includes an L21 positive lens that is arranged closest to the object-side and includes at least one aspheric surface, and an object-side surface of which is convex, and only two cemented lenses toward an image-side of the L21 positive lens, and each of which consists of a negative lens and a positive lens cemented together in this order from the object-side. The following conditional expressions (1) and (2) are satisfied:
−1.0<Rf11/Rf12<0.7  (1); and
55.0<νdave1  (2).

A lens apparatus of which an image side part is detachably mountable to an accessory includes a lens unit that includes a lens disposed closest to the image side part and a holding member that holds the lens, and is movable in an optical axis direction, and a restrictor configured to restrict a movement of the lens unit. When the lens unit is located at a first position, the accessory is not mountable to the lens apparatus, and when the lens unit is located at a second position, the accessory is mountable to the lens apparatus. The restrictor restricts the lens unit from moving without bringing the lens unit into contact with the accessory when the accessory is attached to the lens apparatus.

This optical system includes: a device (106) for generating a plane light wave, called a collimated light wave (OL.sub.col); and a device (114) for deviating the collimated light wave so as to provide a light wave, called a test light wave (OL.sub.test), the deviating device (114) having an adjustable focal length.

An image forming lens is formed by sequentially arranging, from an object side to an image side, a first lens group having positive refractive power, an aperture stop, and a second lens group having positive or negative refractive power. The image forming lens satisfies a conditional expression:
0.15<D1a/D1<0.50, where D1a is an air space between the first positive lens and the second positive lens in the first lens group, and D1 is a distance on an optical axis from an object-side lens surface of the first positive lens to an image-side lens surface of the third positive lens in the first lens group.

In one aspect, a light-mixing system is disclosed, which includes a light pipe having an input surface configured for receiving light from a light source, a light-mixing segment optically coupled to the input surface, and an output surface optically coupled to said light-mixing segment through which light exits the light pipe. A putative vector normal to at least one of the input or the output surface forms a non-zero angle relative to a longitudinal axis of the light-mixing segment. In some embodiments, the non-zero angle can be, for example, about 90 degrees.

The invention concerns a reversing system for a sighting telescope, where the reversing system has at least two mutually displaceable lenses in a tube of the reversing system parallel to an optical axis of the reversing system, where displacement of the at least two displaceable lenses modifies the reproduction scale at which an image projected onto a first image plane of the reversing system is shown on a second image plane of the reversing system, where the at least two displaceable lenses are arranged in all positions between the first and the second image plane, where a surface of the inside of a tube facing the optical axis having at least one absorption area with absorption zones for absorbing incident light and with sliding surfaces located between neighbouring absorption zones for bearings of the at least two displaceable lenses, where the total area of the sliding surfaces is smaller than the total area of the absorption zones, where the at least one sliding surface is arranged at a different distance from the optical axis than the at least one absorption zone.

Provided are an imaging device which can simultaneously capture images in different wavelength ranges and can improve a focusing accuracy of each image, an imaging optical system, and an imaging method. An imaging device (1) includes an imaging optical system (10) which has a first pupil region for passing light in a first wavelength range and a second pupil region for passing light in a second wavelength range, in which an axial chromatic aberration of the imaging optical system (10) is reduced based on a relationship between an aberration other than the axial chromatic aberration of the imaging optical system (10) and positions of the first pupil region and the second pupil region in the imaging optical system (10), an imaging element (100) which includes a first pixel receiving the light passing through the first pupil region in the imaging optical system (10) and a second pixel receiving the light passing through the second pupil region in the imaging optical system (10), and a signal processing unit (200) which processes a signal output from the imaging element (100), and generates each of a first image of the first wavelength range and a second image of the second wavelength range based on an output signal of the first pixel and an output signal of the second pixel.

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. The camera optical lens satisfies following conditions: 3.00≤f1/f≤7.00; and 4.00≤R9/d9≤50.00; f denotes a focal length of the camera optical lens; f1 denotes a focal length of the first lens; R9 denotes a curvature radius of an object-side surface of the fifth lens; and d9 denotes an on-axis thickness of the fifth lens. The camera optical lens can achieve a high imaging performance while obtaining a low TTL.