An antireflection film is formed by laminating an interlayer, a silver-containing metal layer containing silver, and a dielectric layer in this order from the substrate, an anchor region including an oxide of an anchor metal is provided between the silver-containing metal layer and the interlayer, a cap region including an oxide of the anchor metal included in the anchor region is provided between the silver-containing metal layer and the dielectric layer, a crystal grain size obtained by X-ray diffraction measurement in the silver-containing metal layer is less than 6.8 nm, and the anchor metal has a surface energy less than a surface energy of silver and greater than a surface energy of a layer of the interlayer closest to the silver-containing metal layer.

There is provided a lens barrel that can stably support movable lens groups with compact configuration and accurately detect the positions of the movable lens groups. A first main shaft (48) and a first sub-shaft (50) that guide the movement of a third front lens group (G3a), a second main shaft (58) and a second sub-shaft (60) that guide the movement of a fourth lens group (G4), a hall element (84) that is used to detect the position of the third front lens group (G3a), and an MR sensor (94B) that is used to detect the position of the fourth lens group (G4) are disposed on a straight line passing through an optical axis (Z) in a cross section orthogonal to the optical axis (Z). The first main shaft (48) and the first sub-shaft (50) are disposed on the radially inner side than the second main shaft (58) and the second sub-shaft (60). The first main shaft (48) and the second main shaft (58) are disposed so as to 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 camera module includes: an optical imaging system including a frontmost lens disposed closest to an object side, a rearmost lens disposed closest to an imaging plane, and at least one middle lens disposed between the frontmost lens and the rearmost lens. An image-side surface of the rearmost lens is concave and an inflection point is formed on the image-side surface of the rearmost lens. 0.2<D/TTL is satisfied, D being a shortest distance between the rearmost lens and the imaging plane, and TTL being a distance from an object-side surface of the frontmost lens to the imaging plane.

A camera module includes: an optical imaging system including a frontmost lens disposed closest to an object side, a rearmost lens disposed closest to an imaging plane, and at least one middle lens disposed between the frontmost lens and the rearmost lens. An image-side surface of the rearmost lens is concave and an inflection point is formed on the image-side surface of the rearmost lens. 0.2<D/TTL is satisfied, D being a shortest distance between the rearmost lens and the imaging plane, and TTL being a distance from an object-side surface of the frontmost lens to the imaging plane.

A lens barrel including a first lens, an actuator that drives the first lens, a first barrel that holds a first cam follower and the actuator and moves in an optical axis direction, a second lens, and a second barrel that holds a second cam follower and the second lens and moves in the optical axis direction, the second barrel having a first hole portion in which the first cam follower is disposed.

A lens barrel in which tilt adjustment can be made depending on the position of a lens unit in the optical axis direction. This lens barrel includes: at least three guide bars provided so as to extend along the optical axis direction; a driving unit that respectively drives the at least three guide bars in the optical axis direction; a lens frame holding unit that holds an image-capturing lens, the lens frame holding unit being attached to at least three guide bars and being driven in the optical axis direction by the at least three guide bars; and a control unit that controls said at least three linear actuators so as to adjust the respective drive amounts in the optical axis direction of the at least three guide bars and to tilt the lens frame holding unit from a direction orthogonal to the optical axis.

A lens apparatus includes zoom lens units configured to move in an optical axis direction for zooming, and a correction lens unit configured to move in the optical axis direction to correct change in a focal position due to change in an atmospheric pressure. The lens apparatus satisfies an inequality 0.4<|fair_t/fw|<6 where fair_t is a composite focal length of an air lens included in one of the zoom lens units having a smallest absolute value of the composite focal length among the zoom lens units and fw is a focal length of the lens apparatus at a wide-angle end.

A lens barrel including a first lens, an actuator that drives the first lens, a first barrel that holds a first cam follower and the actuator and moves in an optical axis direction, a second lens, and a second barrel that holds a second cam follower and the second lens and moves in the optical axis direction, the second barrel having a first hole portion in which the first cam follower is disposed.

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.

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.