Abstract: A wide-angle lens consists of, in order from an object, a front lens group GF consisting of a first front lens group GF1 that consists of a negative meniscus lens L11 having a concave surface facing an image, a second front lens group GF2 that consists of a negative lens L12 having a concave surface facing the image, and a third front lens group GF3 that 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 GB1 that consists of a cemented positive lens constructed by a negative lens L14 and a positive lens L15, and a second rear lens group GB2 having 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.

Abstract: A wide-angle lens consists of, in order from an object, a front lens group GF consisting of a first front lens group GF1 that consists of a negative meniscus lens L11 having a concave surface facing an image, a second front lens group GF2 that consists of a negative lens L12 having a concave surface facing the image, and a third front lens group GF3 that 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 GB1 that consists of a cemented positive lens constructed by a negative lens L14 and a positive lens L15, and a second rear lens group GB2 having 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.

Abstract: A fisheye lens, comprising a front group made up of a total of three groups, which are two concave lenses 1 and 2 whose concave surfaces are directed toward the image side, and a compound lens 3 whose 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 4, 5, and 6, 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 lens 1 of 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.

Abstract: A fisheye lens, comprising a front group made up of a total of three groups, which are two concave lenses 1 and 2 whose concave surfaces are directed toward the image side, and a compound lens 3 whose 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 4, 5, and 6, 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 lens 1 of 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.

Abstract: 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:-1.5<.PHI..sub.1 /.PHI..sub.2 <-0.8-1.1<.PHI..sub.1 /.PHI..sub.23 <-0.2where .PHI..sub.1 is the refracting power of the first lens group, .PHI..sub.2 is the refracting power of the second lens group, and .PHI..sub.

Abstract: 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.

Abstract: 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;0.05 mm.ltoreq..phi..ltoreq.0.5 mm (1)and0.5.mu..ltoreq.h.ltoreq.3.mu. (2)where the diameter of the aperture of the low refractive-index portion is represented by .phi. and the height or depth between the light-transmitting surface and the top of the lens-shaped curved portion of the low refractive-index portion is presented by h; and the ratio S of the area of the plurality of low refractive-index portions to the area of the light-transmitting surface is defined as follows:5%.ltoreq.S.ltoreq.35% (3)The soft-focus optical element may be attached on an image-focusing lens.

Abstract: 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:(1) 0.28f<.SIGMA.d<0.36f(2) 1.58<n2<1.745(3) n1<n2(4) 0.24<n3-n4<0.30(5) 0.6f<f1<1.0f(6) 0.30f<-r6<0.40f(7) f<-r7<2f(8) 10<.nu.4-.nu.3<25(9) 2<(d5+d6)/d3<9.9(10) 0.18f<d1+d5+d6<0.24f(11) 0.28f<r1<0.31fwhere.SIGMA.

Abstract: 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 asQ.sub.W =(rw.sub.2 +rw.sub.1)/(rw.sub.2 -rw.sub.1)Q.sub.

Abstract: 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.

Abstract: 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.

Abstract: 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:0.5<.phi..sub.2 /.phi..sub.6 <1.40.8f<f.sub.3 <1.5f0<f/f.sub.R <0.50.8f<r.sub.2 <1.5wherein f is the image-side focal length of the total system, .phi..sub.2 and .phi..sub.6 are refractive powers of the second and the sixth components, f.sub.3 is the focal length of the third component, f.sub.R is the composite focal length of the fourth to the sixth components and r.sub.2 is the radius of curvature of the image-side lens surface of the first component.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A great aperture ratio lens includes a first lens which is a positive meniscus lens having its convex surface facing the object side, a second lens which is a positive meniscus lens having its convex surface facing the object side, a third lens which is a negative meniscus lens having its convex surface facing the object side, a fourth lens which is a negative lens having its concave surface facing the object side, a fifth lens which is a positive lens having its convex surface facing the image side, a sixth lens which is a positive meniscus lens having its convex surface facing the image side, and a seventh lens which is a positive lens. The fourth lens and the fifth lens are cemented to each other. The great aperture ratio lens satisfies certain conditions.

Abstract: A compact wide angle lens comprises, in succession from the object side, a first component which is a positive meniscus lens having its convex surface facing the object side, a second component which is a biconcave lens, a third component which is a positive lens having its surface of sharper curvature facing the object side, a fourth component which is a positive lens, and a fifth component which is a negative meniscus lens having its convex surface facing the image side.