Abstract: A converter lens according to an exemplary embodiment of the present invention is a converter lens that has a negative refractive power and increases a focal length of an entire system. The converter lens includes a front group having a positive refractive power and a rear group having a negative refractive power, and the front group is a lens unit having a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by combining a refractive power of each lens in order from the lens closest to an object toward an image side. At this time, a focal length of the front group, a focal length of the converter lens, and a lateral magnification of the converter lens when the converter lens is disposed on an image side of a master lens are determined as appropriate.

Abstract: A zoom lens includes a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a rear lens group including one or more lens units. The zoom lens includes an aperture stop. The rear lens group includes a focus lens unit having negative refractive power that is moved to an image side in focusing from an infinite to a close distance and at least one lens unit arranged on the image side of the focus lens unit. The first lens unit includes three or more negative lenses. The focus lens unit includes a cemented lens or a single lens. The zoom lens satisfies a predetermined inequality.

Abstract: A converter lens (RCL) has a negative refractive power, which is disposed on an image side of a master lens (ML) to make a focal length of an entire system longer than that of the master lens alone. The converter lens comprises a most image-side lens element (LT) disposed closest to an image side in the converter lens, wherein the most image-side lens element has a lens surface having a convex shape toward an image side, a lens disposed closest to an image side in the converter lens has a positive refractive power, and mN<mP and 0.0?LR2/AR2<1.0 are satisfied.

Abstract: A converter lens according to an exemplary embodiment of the present invention is a converter lens that has a negative refractive power and increases a focal length of an entire system. The converter lens includes a front group having a positive refractive power and a rear group having a negative refractive power, and the front group is a lens unit having a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by combining a refractive power of each lens in order from the lens closest to an object toward an image side. At this time, a focal length of the front group, a focal length of the converter lens, and a lateral magnification of the converter lens when the converter lens is disposed on an image side of a master lens are determined as appropriate.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a rear unit including one or more lens units. Distances between adjacent lens units change during zooming. The first lens unit includes a negative lens made of resin. The rear unit includes a positive lens made of resin. A predetermined condition is satisfied.

Abstract: A zoom lens includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and two or more additional lens units. In zooming, the first lens unit moves, and an interval between adjacent lens units changes. The refractive index of a negative lens A disposed on a most object side of negative lenses included in the first lens unit is higher than or equal to 1.89, and the negative lens A and a lens B disposed adjacent to an image side of the negative lens A satisfy a predetermined relationship.

Abstract: A converter lens has negative refractive power, and is disposed on an image side of a master lens so that a focal length of an entire system becomes greater than a focal length of the master lens alone. The converter lens includes a first lens element closest to an object and a second lens element next to an image side of the first lens element with a space between the first lens element and the second lens element. A focal length of the converter lens, a focal length of an air lens formed by the first lens element and the second lens element, the shape of an image-side lens surface of the first lens element, and the shape of an object-side lens surface of the second lens element are determined as appropriate.

Abstract: A converter lens has negative refractive power, and is disposed on an image side of a master lens so that a focal length of an entire system becomes greater than a focal length of the master lens alone. The converter lens includes a first lens element closest to an object and a second lens element next to an image side of the first lens element with a space between the first lens element and the second lens element. A focal length of the converter lens, a focal length of an air lens formed by the first lens element and the second lens element, the shape of an image-side lens surface of the first lens element, and the shape of an object-side lens surface of the second lens element are determined as appropriate.

Abstract: An optical system consists of a front unit and a rear unit. The front unit consists of a first lens having a positive refractive power, a second lens disposed on an image side of the first lens and having a positive refractive power, and a third lens. Each of the first lens and the second lens has a refractive index of 1.7 or higher for d-line. The rear unit consists of two or more and four or fewer lenses and includes a fourth lens having a positive refractive power and a fifth lens adjacent to the fourth lens and having a negative refractive power. Each of the fourth lens and the fifth lens is made of an organic material. A predetermined condition is satisfied.

Abstract: A converter lens (RCL) has a negative refractive power, which is disposed on an image side of a master lens (ML) to make a focal length of an entire system longer than that of the master lens alone. The converter lens comprises a most image-side lens element (LT) disposed closest to an image side in the converter lens, wherein the most image-side lens element has a lens surface having a convex shape toward an image side, a lens disposed closest to an image side in the converter lens has a positive refractive power, and mN<mP and 0.0?LR2/AR2<1.0 are satisfied.

Abstract: An observation optical system according to the present invention includes a Fresnel lens and a lens LP with a positive refractive power provided on a light incident side or a light emitting side of the Fresnel lens. A length in a direction of an optical axis from a surface vertex of a central annular section of the Fresnel lens to an end portion of the central annular section is defined as h0, and a length in the direction of the optical axis of a grating wall surface of a first annular section adjacent to the central annular section is defined as h1. The lengths h1 and h0 are set to appropriate values, respectively.

Abstract: A converter lens according to an exemplary embodiment of the present invention is a converter lens that has a negative refractive power and increases a focal length of an entire system. The converter lens includes a front group having a positive refractive power and a rear group having a negative refractive power, and the front group is a lens unit having a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by combining a refractive power of each lens in order from the lens closest to an object toward an image side. At this time, a focal length of the front group, a focal length of the converter lens, and a lateral magnification of the converter lens when the converter lens is disposed on an image side of a master lens are determined as appropriate.

Abstract: A converter lens (RCL) has a negative refractive power, which is disposed on an image side of a master lens (ML) to make a focal length of an entire system longer than that of the master lens alone. The converter lens comprises a most image-side lens element (LT) disposed closest to an image side in the converter lens, wherein the most image-side lens element has a lens surface having a convex shape toward an image side, a lens disposed closest to an image side in the converter lens has a positive refractive power, and mN<mP and 0.0?LR2/AR2<1.0 are satisfied.

Abstract: A converter lens according to an exemplary embodiment of the present invention is a converter lens that has a negative refractive power and increases a focal length of an entire system. The converter lens includes a front group having a positive refractive power and a rear group having a negative refractive power, and the front group is a lens unit having a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by combining a refractive power of each lens in order from the lens closest to an object toward an image side. At this time, a focal length of the front group, a focal length of the converter lens, and a lateral magnification of the converter lens when the converter lens is disposed on an image side of a master lens are determined as appropriate.

Abstract: A lens apparatus includes two different optical systems. Each of the two optical systems includes a front lens unit having negative refractive power, an intermediate lens unit, and a rear lens unit disposed in this order from an object side to an image plane side. Each of the intermediate lens units in the two optical systems includes a first reflecting member for bending an optical path at a position adjacent to the front lens unit, and a second reflecting member for bending the optical path at a position adjacent to the rear lens unit. The following conditional expression is satisfied: 0.05<Dout/Din<0.50, where Din is a distance between surface vertexes of lenses closest to an object in the two optical systems, and Dout is a distance between surface vertexes of lenses closest to an image plane in the two optical systems.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a rear unit including one or more lens units. Distances between adjacent lens units change during zooming. The first lens unit includes a negative lens made of resin. The rear unit includes a positive lens made of resin. A predetermined condition is satisfied.

Abstract: A converter lens (RCL) has a negative refractive power, which is disposed on an image side of a master lens (ML) to make a focal length of an entire system longer than that of the master lens alone. The converter lens comprises a most image-side lens element (LT) disposed closest to an image side in the converter lens, wherein the most image-side lens element has a lens surface having a convex shape toward an image side, a lens disposed closest to an image side in the converter lens has a positive refractive power, and mN<mP and 0.0?LR2/AR2<1.0 are satisfied.

Abstract: Provided is an observation optical system used for observing an image displayed on an image display surface. The observation optical system includes, in order from an observation surface side to the image display surface side, a first lens having a positive refractive power, and a second lens having a positive refractive power. The first lens is a Fresnel lens, and a focal length f1 of the first lens and a focal length f2 of the second lens are each appropriately set.

Abstract: A converter lens has negative refractive power, and is disposed on an image side of a master lens so that a focal length of an entire system becomes greater than a focal length of the master lens alone. The converter lens includes a first lens element closest to an object and a second lens element next to an image side of the first lens element with a space between the first lens element and the second lens element. A focal length of the converter lens, a focal length of an air lens formed by the first lens element and the second lens element, the shape of an image-side lens surface of the first lens element, and the shape of an object-side lens surface of the second lens element are determined as appropriate.

Abstract: A converter lens according to an exemplary embodiment of the present invention is a converter lens that has a negative refractive power and increases a focal length of an entire system. The converter lens includes a front group having a positive refractive power and a rear group having a negative refractive power, and the front group is a lens unit having a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by combining a refractive power of each lens in order from the lens closest to an object toward an image side. At this time, a focal length of the front group, a focal length of the converter lens, and a lateral magnification of the converter lens when the converter lens is disposed on an image side of a master lens are determined as appropriate.