Abstract: There is provided: an optical system including a focus lens group having positive refractive power and configured to move along an optical axis when focusing from an infinite-distance object to a short-distance object, and satisfying predetermined conditional expressions; and an imaging device including the optical system. The focus lens group includes a lens subgroup A, an aperture stop, and a lens subgroup B in order from the object side. The lens subgroup A includes a negative lens, a positive lens, and a positive lens in order from the image side. The lens subgroup B includes a negative lens and a positive lens in order from the object side.

Abstract: An image forming apparatus includes a light source that irradiates an observation target with excitation light; an imaging part that separately receives short wavelength-side NIR light and SWIR light from the observation target; and an image processing unit that generates a composite image having both a density of a short wavelength-side NIR light image and a definition of an SWIR light image.

Abstract: A zoom lens includes, in order from an object side, a first lens group that is positive, a second lens group that is negative, a third lens group that is positive, and a fourth lens group that is positive. During zooming from a wide angle end to a telephoto end, at least the first lens group and the third lens group are fixed and an interval on an optical axis of an adjacent lens group relative thereto is changed. In the zoom lens, the fourth lens group includes at least one positive lens and satisfies a predetermined conditional expression. In addition, an imaging device includes the zoom lens and an image sensor.

Abstract: There is provided: an optical system including a focus lens group having positive refractive power and configured to move along an optical axis when focusing from an infinite-distance object to a short-distance object, and satisfying predetermined conditional expressions; and an imaging device including the optical system. The focus lens group includes a lens subgroup A, an aperture stop, and a lens subgroup B in order from the object side. The lens subgroup A includes a negative lens, a positive lens, and a positive lens in order from the image side. The lens subgroup B includes a negative lens and a positive lens in order from the object side.

Abstract: There is provided: an optical system including a focus lens group having positive refractive power and configured to move along an optical axis when focusing from an infinite-distance object to a short-distance object, and satisfying predetermined conditional expressions; and an imaging device including the optical system. The focus lens group includes a lens subgroup A, an aperture stop, and a lens subgroup B in order from the object side. The lens subgroup A includes a negative lens, a positive lens, and a positive lens in order from the image side. The lens subgroup B includes a negative lens and a positive lens in order from the object side.

Abstract: There are provided an optical system and an imaging device including the same. The optical system includes: in order from an object side to an image side, a first lens group having refractive power; and a second lens group having positive refractive power. A variable distance that varies during focusing between the first lens group and the second lens group is closer to an object than a variable distance that varies during focusing between other lenses. The first lens group includes a positive lens and at least one or more negative lenses in order from the image side. The second lens group includes a lens subgroup 2A having positive refractive power, an aperture stop, and a lens subgroup 2B having positive refractive power in order from the object side. The lens subgroup 2B includes a negative lens and a positive lens in order from the object side and satisfies a predetermined Conditional Expression.

Abstract: There are provided an optical system and an imaging device including the same. The optical system includes: in order from an object side to an image side, a first lens group having refractive power; and a second lens group having positive refractive power. A variable distance that varies during focusing between the first lens group and the second lens group is closer to an object than a variable distance that varies during focusing between other lenses. The first lens group includes a positive lens and at least one or more negative lenses in order from the image side. The second lens group includes a lens subgroup 2A having positive refractive power, an aperture stop, and a lens subgroup 2B having positive refractive power in order from the object side. The lens subgroup 2B includes a negative lens and a positive lens in order from the object side and satisfies a predetermined Conditional Expression.

Abstract: A zoom lens includes, in order from an object side, a first lens group that is positive, a second lens group that is negative, a third lens group that is positive, and a fourth lens group that is positive. During zooming from a wide angle end to a telephoto end, at least the first lens group and the third lens group are fixed and an interval on an optical axis of an adjacent lens group relative thereto is changed. In the zoom lens, the fourth lens group includes at least one positive lens and satisfies a predetermined conditional expression. In addition, an imaging device includes the zoom lens and an image sensor.

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: 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.