Nippon Kogaku K.k.

Nikon Corporation

Koichi Wakamiya

Hiroshi Wakabayashi

Susumu Sato

Koichi Ohshita

Hidenori Miyamoto

Daijiro Fujie

Hachiro Kanai

Toshio Sousa

A wide-angle lens consists of, in order from an object, a front lens group GF consisting of a first front lens group GFthat consists of a negative meniscus lens Lhaving a concave surface facing an image, a second front lens group GFthat consists of a negative lens Lhaving a concave surface facing the image, and a third front lens group GFthat has a convex surface facing the object and has positive refractive power; and a rear lens group GB consisting of a first rear lens group GBthat consists of a cemented positive lens constructed by a negative lens Land a positive lens L, and a second rear lens group GBhaving positive refractive power; thereby providing a wide-angle lens having a wide angle of view, well corrected aberrations, less ghost images capable of coping with wide luminance difference, and an imaging apparatus equipped therewith.

Wide-angle lens and imaging apparatus equipped therewith

A fisheye lens, comprising a front group made up of a total of three groups, which are two concave lensesandwhose concave surfaces are directed toward the image side, and a compound lenswhose concave surface is directed toward the image side and which has an overall convex or concave refractive power; and a rear group formed by three groups of convex lenses, and, wherein the front group includes at least one compound lens set, the rear group includes one compound lens set, and at least a first surface of a first concave lensof the front group is an aspheric surface, and satisfies specific conditions. As a result, it is possible to obtain a fisheye lens that can realize a foveal optical system with undiminished illuminance all the way to the periphery and with high resolution over the entire field of view, and with which a wide field of view and an extremely compact size can be attained with a single wide-angle optical system.

Fish-eye lens and imaging device

A compound zoom lens optical system includes a variable focal length photographing lens consisting of a first lens group having a positive refracting power, and a second lens group having a negative refracting power from an object side in turn. A conversion lens is separably added to an image side of the variable focal length photographing lens. The conversion lens is simultaneously movable along an optical axis to be interlocked with at least one of the first and second lens groups of the variable focal length photographing lens so as to change a synthesized focal length with said variable focal length photographing lens. The variable focal length photographing lens and the conversion lens satisfy the following conditions:

Compound zoom lens

A variable focal length photo-taking optical system includes a photo-taking objective lens, and a conversion lens removably added to the photo-taking objective lens and relatively movable along the optic axis with at least some lens groups of the photo-taking objective lens to change the combined focal length of the photo-taking objective lens and the conversion lens.

Variable focal length photo-taking optical system

A soft-focus optical element has a light-transmitting surface formed with a plurality of low refractive index portions each in the form of a lens-like curved surface; the size of each low refractive-index portion is within the following range;

Soft-focus optical element

An objective lens having a stop provided most adjacent to the image side comprises, in succession from the object side, a first lens which is a positive meniscus lens having its convex surface facing the object side, a second lens which is a biconcave lens, a third lens which is a biconvex lens, and a fourth lens which is a negative meniscus lens having its convex surface facing the image side and is joined to the third lens and formed into a compositely positive cemented lens. The objective lens satisfies the following conditions:

Objective lens

A viewfinder system capable of changing over the magnification includes an objective lens unit having at least two negative lens elements replaceable with each other for magnification change-over, and an eyepiece unit having a positive refractive power and constituting an inverted Galilean telescope type viewfinder with the objective lens unit. When the radius of curvature of that surface of one negative lens element for low magnification which is adjacent to the object side is rw.sub.1 and the radius of curvature of that surface of said one negative lens element which is adjacent to the eyepiece side is rw.sub.2 and the radius of curvature of that surface of the other negative lens element for high magnification which is adjacent to the object side is rT1 and the radius of curvature of that surface of said other negative lens element which is adjacent to the eyepiece side is rT2 and Q.sub.W and Q.sub.T are defined as

Inverted galilean telescope type viewfinder system capable of changing

A rear conversion lens to be mounted in between an objective lens and a determined image plane to produce a composite focal length longer than the focal length of the objective lens itself comprises, in the order from the object side a first lens component, a second lens component and a third lens component. The first lens component has a positive focal length and the image-side lens surface being convex toward the image side. The second lens component has a negative focal length and the object-side lens surface being convex toward the image side. The third lens component has a negative focal length and is in the shape of a meniscus convex toward the image side.

Rear conversion lens

In an albada finder having index means for indicating the photographable area of an object to be photographed and an albada reflecting surface positioned more adjacent to the object side than the index means and reflecting a light beam from the index means toward the observer side, there is provided a lens in which the albada reflecting surface is formed on the lens surface thereof which is adjacent to the object side.

Albada finder

A wide angle lens having a long back focus substantially equal to the rear focal length of the total lens system comprising six lens components with a stop between the third and fourth components from the object side satisfies the conditions:

Wide angle lens

A camera comprises a photo-taking lens system having an optic axis and movable along the optic axis for focusing, a view finder means including an objective having an optic axis different from the optic axis of the photo-taking lens system, first view field indicating means provided to indicate the range of a photographing picture plane obtained when an object to be photographed lying in a predetermined distance range is photographed within an observation view field formed through the objective, and second view field indicating means provided to indicate the range of a photographing picture plane obtained when an object to be photographed lying outside the predetermined distance range is photographed within the observation view field, and preventing means responsive to movement of the photo-taking lens system to prevent viewing of at least a part of the second view field indicating means when the photo-taking lens system is focused to the object to be photographed lying in the predetermined distance range.

Parallax correcting device in the finder of a camera

A behind stop lens comprises, in succession from the object side, a first lens which is a positive meniscus lens having its convex surface facing the object side, a second lens which is a biconcave lens, a third lens which is a biconvex lens, and a fourth lens which is a negative meniscus lens having its convex surface facing the image side. The third lens and the fourth lens are joined together to form a positive cemented lens. The behind stop lens has a stop at a position most adjacent to the image side.

Behind stop lens

A changeable magnification inverted Galilean finder includes, in succession from the object side, an objective lens group having a negative refractive power, and an eyepiece of positive refractive power disposed at a predetermined distance from the objective lens group. The objective lens group has a first objective lens for low magnification and a second objective lens for high magnification. The first objective lens for low magnification has a first negative lens component having a predetermined negative refractive power. The second objective lens for high magnification has a negative refractive power smaller than the refractive power of the first objective lens for low magnification, and has a second negative lens component and a positive lens component added on the object side of the second negative lens component. A low magnification state in which the objective lens for low magnification is disposed on the same optic axis as that of the eyepiece and a high magnification state in which the objective lens for high magnification is disposed on the same optic axis as that of the eyepiece are selectively constructed.

Changeable magnification inverted galilean finder

A behind stop lens has, in succession from the object side, a first lens which is a positive meniscus lens having its convex surface facing the object side, a second lens which is a biconcave negative lens, a third lens which is a biconvex positive lens, and a fourth lens which is a negative meniscus lens having its convex surface facing the image side, the third lens and the fourth lens being cemented together to form a positive cemented lens. The behind stop lens satisfies the following conditions: ##EQU1## where f represents the total focal length of the entire system, .SIGMA.d represents the distance from the vertex of the object side lens surface of the first lens to the vertex of the image side lens surface of the fourth lens, f.sub.2 represents the focal length of the second lens, r represents the radius of curvature of each lens surface, n and .nu. represent the refractive index and the Abbe number, respectively, of each lens, and the subscript numbers mean the order from the object side.

In a four-unit five-lens system wherein in succession from the object side, each of a first lens and a second lens comprises a positive meniscus lens having its convex surface facing the object side, a third lens comprises a biconcave lens, a fourth lens comprises a biconvex lens, a fifth lens comprises a negative meniscus lens having its convex surface facing the image side, the fourth lens and the fifth lens being cemented together to form a positive cemented lens, and a diaphragm is provided most adjacent to the image side, a behind diaphragm lens satisfies certain conditions.

Growing community of inventors

Tokyo, Japan

Koichi Wakamiya