Installation of an industrial camera is simplified. An industrial camera includes an imaging unit that captures an inspection object to generate an inspection target image, a distance measurement unit that measures an installation distance that is a distance to the inspection object, a storage unit that stores a camera parameter of the imaging unit, an interface unit that is able to receive an input of a size of a field of view or a pixel resolution as a required specification from a user, and a calculation unit that automatically calculates an optical condition necessary for realizing the required specification based on the installation distance measured by the distance measurement unit, the camera parameter stored in the storage unit, and the input required specification.

An antireflection film is provided on a substrate and includes an interlayer, a silver-containing metal layer containing silver, and a dielectric layer, which are laminated in this order on a side of a substrate, in which the interlayer is a multilayer film having at least two layers in which a layer of high refractive index having a relatively high refractive index and a layer of lower refractive index having a relatively low refractive index are alternately laminated, the dielectric layer has a surface exposed to air, and the dielectric layer is a multilayer film including a silicon-containing oxide layer, a magnesium fluoride layer, and an adhesion layer provided between the silicon-containing oxide layer and the magnesium fluoride layer and configured to increase adhesiveness between the silicon-containing oxide layer and the magnesium fluoride layer.

There is provided an imaging lens with high-resolution which satisfies demand of wide field of view, low-profileness and low F-number in well balance, and excellently corrects aberrations. An imaging lens comprises, in order from an object side to an image side, a first lens, a second lens having negative refractive power near the optical axis, a third lens having a convex surface facing the image side near the optical axis, a fourth lens and a fifth lens, wherein said first lens has negative refractive power near the optical axis, an image-side surface of said fifth lens has a convex surface facing the image side near the optical axis, and below conditional expressions are satisfied:
3.00<(T4/f)×100<5.90
0.40<f2/f5<1.45
where
T4: a distance along the optical axis from the image-side surface of the fourth lens to the object-side surface of the fifth lens,
f: a focal length of the overall optical system of the imaging lens,
f2: a focal length of the second lens,
f5: a focal length of the fifth lens.

A variable magnification optical system comprising a plurality of lens groups which includes a first negative lens group having negative refractive power, a second negative lens group disposed at a more image side than the first negative lens group and having negative refractive power, a third negative lens group disposed at a more image side than the second negative lens group and having negative refractive power; upon varying a magnification, distances between adjacent lens groups being varied; the first negative lens group being movable to include a component in a direction perpendicular to the optical axis as a vibration reduction lens group; the second negative lens group being moved along the optical axis upon carrying out focusing; and the predetermined conditional expression (s) being satisfied. The variable magnification optical system can attain a high optical performance and be made in small in size.

The present disclosure relates to zoom lenses and optical devices using the same. A zoom lens may include in order from an object side to an image side: a first lens group, a second lens group, a third lens group, a fourth lens group; and a fifth lens group. The zoom lens may satisfy the following conditions: −2.28≤f.sub.2/f.sub.w′≤−1.08, and 0.15≤TTL/(BFL*f.sub.w′)≤0.45, wherein f.sub.2 denotes a focal length of the second lens group, f.sub.w′ denotes a focal length of the zoom lens at a wide angle end, TTL denotes a total track length of the zoom lens, and BFL denotes a back focal length of the zoom lens.

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 lens barrel including a first main shaft and a first sub-shaft that guide the movement of a third front lens group (G3a), a second main shaft and a second sub-shaft that guide the movement of a fourth lens group (G4), a hall element that is used to detect the position of the third front lens group (G3a), and an MR sensor that is used to detect the position of the fourth lens group (G4) are disposed on a straight line passing through an optical axis in a cross section orthogonal to the optical axis. The first main shaft and the second main shaft overlap each other in a direction of the optical axis. In a drive unit for each lens group, a plurality of drive magnets are arranged symmetrically with respect to the straight line.

A zoom lens satisfies Conditional Expression (1) as follows:
−20<Twt/Twm<1,  (1)
Twt is a moving amount of the second lens group during zooming from the short focal-length end to the long focal-length end, a moving amount to the object side being indicated by a positive sign, a moving amount to an image side being indicated by a negative sign, and
Twm is a moving amount of the second lens group during zooming from the short focal-length end to an intermediate focal length, a moving amount to the image side being indicated by a negative sign,
the intermediate focal length being expressed by fm=(fw.Math.ft).sup.1/2, where fw is a focal length of a whole system at the short focal-length end, and ft is a focal length of the whole system at the long focal-length end.

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 lens support mechanism 10 comprises lens group units 23 to 27, a substantially cylindrical rectilinear cylinder 11, and a substantially cylindrical cam cylinder 12. The rectilinear cylinder 11 envelops the lens group units 23 to 27, and has main cam followers 11b protruding outward in the radial direction from the outer peripheral surface, and a sub cam groove 11c. The cam cylinder 12 has main cam grooves 12b and a sub cam follower 12c, and is disposed on the outer peripheral side of the rectilinear cylinder 11. The main cam grooves 12b engage with the main cam followers 11b and are formed substantially parallel to the sub cam groove 11c, and upon rotating relative to the rectilinear cylinder 11, move the lens group units 23 to 27 back and forth in the optical axis direction. The sub cam followers 12c project inward in the radial direction and engage with the sub cam grooves 11c.