Abstract: A lens unit and a rear-side focus adjustment system for infrared cameras capable of performing rear-side focus adjustments even when the position of the detection surface of an infrared sensor is unknown in an infrared camera. The lens unit is detachably mounted on a camera body that detects infrared light with an infrared sensor and converts the infrared light to an image signal, the lens unit including a focus adjustment lens and controller. The controller calculates a rear-side focus adjustment amount for causing a rear-side focus position to correspond to the detection surface based on an error between an actually measured focused position of the focus adjustment lens relative to an object at a particular object distance and a theoretically focused position of the focus adjustment lens calculated based on the object distance and controls the position of the focus adjustment lens based on the rear-side focus adjustment amount.

Abstract: A variable magnification optical system according to the present invention includes, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a following lens group, wherein at least the second lens group is moved so that a gap between the first lens group and the second lens group increases and a gap between the second lens group and the third lens group decreases when zooming from a wide angle end to a telephoto end, and a predetermined conditional expression is satisfied.

Abstract: The present invention provides a zoom lens that is compact in general and has an F-number to implement brightness even in the telephoto end side, and an imaging apparatus equipped with the zoom lens. The zoom lens includes, in order from an object side: a first lens group having positive refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power. At the time of zooming from the wide-angle end state to the telephoto end state, the third lens group moves so that the distance between the second lens group and the third lens group increases, and the distance between the third lens group and the fourth lens group decreases.

Abstract: An inner focus lens includes sequentially from an object side, a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a negative refractive power. The second lens group is moved along an optical axis, whereby focusing from a focus state for an object at infinity to a focus state for a minimum object distance is performed. A lens group configured by a lens other than a lens that is disposed farthest on the object side is moved in a direction orthogonal to the optical axis to shift an image. The inner focus lens satisfies a conditional expression (1) 0.15?(1??p)×?r?4.50, where ?p is transverse magnification of the orthogonally moved lens group and ?r is composite transverse magnification of a lens group disposed farther on an image side than the orthogonally moved lens group.

Abstract: The optical system of the present invention includes, in order from an object side: a first lens group G1 having positive refractive power; a second lens group G2 having negative refractive power; and a third lens group G3 having positive refractive power, wherein the first lens group G1 and the third lens group G3 are fixed in an optical axis direction, while the second lens group G2 is moved in the optical axis direction to focus on from an object at infinity to an object at a finite distance, the third lens group G3 includes, in order from the object side: an object-side group G3a; an aperture stop S; and an image-side group G3b, and a specified condition is satisfied.

Abstract: A variable magnification optical system according to the present invention includes a C lens group having positive refractive power, a B lens group having negative refractive power, and an A lens group having positive refractive power in order from an image side and includes an N lens group having negative refractive power on an object side in relation to the A lens group, wherein when zooming from a wide angle end to a telephoto end, at least the A lens group, the B lens group, and the N lens group are moved relative to an image plane and a predetermined conditional expression is satisfied.

Abstract: A variable magnification optical system according to the present invention includes, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a following lens group, wherein at least the second lens group is moved so that a gap between the first lens group and the second lens group increases and a gap between the second lens group and the third lens group decreases when zooming from a wide angle end to a telephoto end, and a predetermined conditional expression is satisfied.

Abstract: An anti-reflection coat includes an intermediate layer and a low refractive index layer sequentially stacked on a substrate, and preventing the reflection of incident light by optical interference effect, wherein the low refractive index layer is a film formed on the surface of the intermediate layer by a wet film formation method using a coating liquid including layer-constituting raw materials which includes hollow silica particles adhering each other with a binder, and the intermediate layer is a layer mainly composed of an organometallic compound which adheres well to the binder and having wettability to the coating liquid; and provides an optical device including the anti-reflection coat.

Abstract: A wide angle zoom lens includes sequentially from the object side, a first lens group having a negative refractive power overall and three lenses, including first to third lenses, having a negative refractive power and disposed farthest on the object side; a second lens group having a positive refractive power overall and one or more sets of cemented lenses; and a third lens group having a negative refractive power. This ultra wide angle zoom lens varies intervals between the first lens group, the second lens group, and the third lens group on the optical axis to zoom from the wide angle end to the telephoto end and satisfies given conditions to thereby enable a high zoom ratio, large diameter, and high resolution.

Abstract: An inner focusing lens has sequentially from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a negative refractive power. The first lens group has negative meniscus lenses disposed farthest on the object side thereof. The second lens group is moved along the optical axis whereby focusing from a focus state for an object at infinity to a focus state for the minimum object distance is performed. The inner focusing lens satisfies predetermined conditions and thereby, realizes a compact inner focusing lens having high imaging performance at wide angles, suitable for compact cameras having a function of capturing video.

Abstract: A zoom lens includes a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, a fourth lens group having negative refracting power and a fifth lens group having negative refracting power in order from an object side, in which the lens groups move in magnification change from a wide angle end to a telephoto end such that a gap between the first lens group and the second lens group increases and a gap between the second lens group and the third lens group decreases, a negative lens group disposed closer to an image focusing side than a diaphragm among all lens groups is set as a focusing lens group, and the focusing lens group moves toward the image focusing side at focusing from infinity to a close object, the zoom lens satisfies a conditional expression.

Abstract: An object of the present invention is to provide an anti-reflection film excellent in high-temperature and high-humidity environment resistance and scratch resistance in addition to improved anti-reflection performance of a concave-convex nanostructure. To achieve the object, an anti-reflection film 10 comprises: a base layer 11 as a first optical thin film that is provided on an optical surface 21a of an optical element 21; a concave-convex nanostructure layer that is provided on a surface of the base layer 11 and is composed of a concave-convex nanostructure 12 formed so as to have a pitch width p between the convex parts 12b of shorter than an incident light wavelength; and a cover layer 13 as a second optical thin film that covers peaks of the convex part 12b with a void 14 being provided between the cover layer 13 and concave part 12a constituting the concave-convex nanostructure 12.

Abstract: An inner focus lens includes sequentially from an object side, a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a negative refractive power. The second lens group is moved along the optical axis, whereby focusing from a focus state for an object at infinity to a focus state for a minimum object distance is performed. The inner focus lens satisfies a conditional expression (1) ?29.0?f3/f??5.4, where f3 is a focal length of the third lens group at the focus state for an object at infinity and f is a focal length of the optical system overall at the focus state for an object at infinity.

Abstract: The zoom lens comprises five or more groups of lens pieces, namely, the foremost or first lens group of positive refractive power located the closest to an object, the succeeding second lens group of negative refractive power, the third lens group of positive refractive power, the fourth lens group of positive refractive power, and the fifth lens group all arranged in this order, and if any, the rearmost lens group(s) closer to the imaging plane than the fifth lens group. The zoom lens meets requirements as defined in the conditional expression regarding a combined magnification of the fifth lens group and, if any, the rearmost lens group(s) closer to the imaging plane than the fifth lens group while the zoom lens is taking a telephoto position.

Abstract: An optical system of the present invention includes, in order from an object side: a first lens group G1; a second lens group G2 having positive refractive power; and a third lens group G3 having positive refractive power, wherein the first lens group G1 and the third lens group G3 are fixed in an optical axis direction while the second lens group G2 is moved in an optical axis direction to focus on from an object at infinity to an object at a finite distance, and specified conditions is satisfied.

Abstract: A zoom lens has in order from the object side, at least a foremost, first lens group having positive refractive power, a succeeding, second lens group having negative refractive power, a third lens group having positive refractive power, and a rearmost lens group having negative refractive power. The zoom lens meets requirements as defined in formulas regarding a displacement of the first lens group, a focal length of the zoom lens at the wide-angle end, a focal length of the zoom lens at the telephoto end, a focal length of the first lens group, and a focal length of the third lens group.

Abstract: A zoom lens has in order from the object side, at least a foremost, first lens group having positive refractive power, a succeeding, second lens group having negative refractive power, a third lens group having positive refractive power, and a rearmost lens group having negative refractive power. The zoom lens meets requirements as defined in formulas regarding a displacement of the first lens group, a focal length of the zoom lens at the wide-angle end, a focal length of the zoom lens at the telephoto end, a focal length of the first lens group, and a focal length of the third lens group.