Abstract: The wide angle optical system includes in order from a side of an object in front, a first lens group having a negative refractive power, a second lens group having a catadioptric optical element, an aperture stop, and a third lens group having a positive refractive power, and the catadioptric optical element has a first surface, a second surface, and a third surface, and the first surface has a first transmitting surface and a first reflecting surface, the second surface has a second transmitting surface and a second reflecting surface, and the third surface has a third transmitting surface, and the third transmitting surface is a side surface of a circular truncated cone, and the following conditional expressions (1), (2), and (3) are satisfied: ?p<?n??(1), |?p|<|?n|??(2), and 90°??k<?/2??(3).

Abstract: The wide angle optical system includes in order from a side of an object in front, a first lens group having a negative refractive power, a second lens group having a catadioptric optical element, an aperture stop, and a third lens group having a positive refractive power, and the catadioptric optical element has a first surface, a second surface, and a third surface, and the first surface has a first transmitting surface and a first reflecting surface, the second surface has a second transmitting surface and a second reflecting surface, and the third surface has a third transmitting surface, and the third transmitting surface is a side surface of a circular truncated cone, and the following conditional expressions (1), (2), and (3) are satisfied: ?p<?n??(1), |?p|<|?n|??(2), and 90°??k<?/2??(3).

Abstract: A wide-angle optical system includes a first group having negative and positive lenses, a second group having a catadioptric optical element, and a third group. The catadioptric optical element includes a first surface at an object side, a second surface at an image side, and a third surface. The first surface has a first transmission surface and a first reflection surface disposed therearound. The second surface has a second transmission surface and a second reflection surface disposed therearound. The third surface is a circular conical transmission surface that is disposed between the first surface and the second surface and an apex of which is located at the object side.

Abstract: A wide-angle optical system includes a first group having negative and positive lenses, a second group having a catadioptric optical element, and a third group. The catadioptric optical element includes a first surface at an object side, a second surface at an image side, and a third surface. The first surface has a first transmission surface and a first reflection surface disposed therearound. The second surface has a second transmission surface and a second reflection surface disposed therearound. The third surface is a circular conical transmission surface that is disposed between the first surface and the second surface and an apex of which is located at the object side.

Abstract: An optical system for viewing a front object and a generally side object comprises, sequentially from the front object side, a first lens group having a negative refractive index, a second lens group including a reflective-refractive lens, an aperture stop, and a third lens group having a positive refractive index. The reflective-refractive lens is provided with a first surface formed on the front object side, a second surface formed on an image side, and a third surface formed circumferentially to surround an optical axis between the first surface and the second surface. The first surface is provided with a first transmission surface formed around the optical axis, and a first reflection surface that faces the image side and is formed around the first transmission surface. The first surface is defined by an aspherical surface consisting of a concave surface in the vicinity of the optical axis and a convex surface in the vicinity of the first reflection surface.

Abstract: An optical element of the present invention is provide with a first surface which is formed on the front-object side and upon which light from the front-object side is incident, a second surface formed on the image side, and a third surface which is formed between the first surface and the second surface and upon which light from the generally lateral object side is incident. The first surface is provided with a first transmission surface formed around the optical axis and a first reflection surface which faces the image side and which is formed annularly around the first transmission surface. The second surface is provided with a second transmission surface formed around the optical axis, and a second reflection surface which faces the front object side and which is formed annularly around the second transmission surface.

Abstract: An observation optical system has a negative lens unit placed at the most object-side position; an annular prism placed on the image side of the negative lens, having a reflecting surface on the negative lens side; and an imaging lens unit arranged on the image side of the negative lens and the annular prism.

Abstract: An optical system for observing front and lateral objects includes a negative front group having a reflective refractive element, an aperture stop, and a positive rear group having a moving lens unit that is movable along the optical axis. The reflective refractive element includes a front-object-side first face having a transmitting surface and a reflective surface annularly formed around the transmitting surface, an image-side second face having a transmitting surface and a reflective surface annularly formed around the transmitting surface, and a face formed as a transmitting surface between the first and second faces. The optical system performs focusing onto an object while hardly changing, in the entire observation area, an area in which an image of the front object is formed, by moving the moving lens unit to the extent that the refractive powers of the front and rear groups hardly change relative to each other.

Abstract: An optical system includes a negative front group having a component of first and second lenses cemented together, an aperture stop, and a positive rear group. The component has: a first face, on the front-direction-object side of the first lens, having a first transmitting surface and an annularly-formed first reflecting surface facing the image side; a second face, at the cemented surface, having a second transmitting surface and an annularly-formed second reflecting surface facing the front-direction-object side; a third face as a transmitting surface on the image side of the second lens; and a fourth face as a transmitting circumferential face of the first lens. The component satisfies the conditions: |nd—RL1?nd—RL2|<0.3 |vd—RL1?vd—RL2|<40 where nd—RL1 and nd—RL2 are refractive indices for d line, of the first and second lenses, respectively, and vd—RL1 and vd—RL2 are Abbe's numbers for d line, of the first and second lenses, respectively.

Abstract: An optical system for observation of a front-direction object and a substantially-lateral-direction object includes, in order from the front-direction-object side, a front group with a negative refracting power having a reflecting/refracting optical element, an aperture stop, and a rear group with a positive refracting power having a moving lens component movable along the optical axis. The reflecting/refracting optical element has a first face formed on the front-direction-object side, a second face formed on the image side, and a third face formed as a transmitting surface between the first face and the second face. The first face has a first transmitting surface formed with the optical axis being at a center thereof and a first reflecting surface annularly formed around the first transmitting surface and directed toward an image side.

Abstract: An optical system for observation of a front-direction object and a substantially-lateral-direction object includes, in order from the front-direction-object side, a front group with a negative refracting power having a reflecting/refracting optical element, an aperture stop, and a rear group with a positive refracting power having a moving lens component movable along the optical axis. The reflecting/refracting optical element has a first face formed on the front-direction-object side, a second face formed on the image side, and a third face formed as a transmitting surface between the first face and the second face. The first face has a first transmitting surface formed with the optical axis being at a center thereof and a first reflecting surface annularly formed around the first transmitting surface and directed toward an image side.

Abstract: An optical element of the present invention is provide with a first surface which is formed on the front-object side and upon which light from the front-object side is incident, a second surface formed on the image side, and a third surface which is formed between the first surface and the second surface and upon which light from the generally lateral object side is incident. The first surface is provided with a first transmission surface formed around the optical axis and a first reflection surface which faces the image side and which is formed annularly around the first transmission surface. The second surface is provided with a second transmission surface formed around the optical axis, and a second reflection surface which faces the front object side and which is formed annularly around the second transmission surface.

Abstract: An optical system for viewing a front object and a generally side object comprises, sequentially from the front object side, a first lens group having a negative refractive index, a second lens group including a reflective-refractive lens, an aperture stop, and a third lens group having a positive refractive index. The reflective-refractive lens is provided with a first surface formed on the front object side, a second surface formed on an image side, and a third surface formed circumferentially to surround an optical axis between the first surface and the second surface. The first surface is provided with a first transmission surface formed around the optical axis, and a first reflection surface that faces the image side and is formed around the first transmission surface. The first surface is defined by an aspherical surface consisting of a concave surface in the vicinity of the optical axis and a convex surface in the vicinity of the first reflection surface.

Abstract: The invention relates to an epi-illumination optical system for microscopes which relies upon a Köhler illumination system using a collective lens array, having simplified adjustment function capable of adjusting the image position of a light source to the back focal position of each microscope objective lens in operable association with microscope objective lens replacement. The invention provides an epi-illumination optical system for microscopes, with an objective lens serving as a condenser lens, which comprises a light source, a collimate lens, and a lens array. The epi-illumination optical system further comprises a projection optical system adapted to project an image of light source formed by collective lens array. The projection optical system comprises a partial optical system movable in an optical axis direction, so that the imaging position for the image array of light source is adjustable to the back focal position of the objective lens.

Abstract: An optical system includes, in order from a front-direction-object side, a first group with a negative refracting power having a reflecting/refracting optical element, an aperture stop, and a rear group with a positive refracting power.

Abstract: In an optical system for observing a front object and an approximately lateral object, a front group having a reflective refractive optical element and negative refractive power, an aperture stop, and a rear group having a moving lens group and positive refractive power are arranged in order from the front-object side, where the moving lens group moves in the direction along the optical axis, the reflective refractive optical element includes a first surface which has a first transmitting surface and a first reflective surface and is formed on the front-object side, where the first transmitting surface is formed with the center of the first transmitting surface on the optical axis and the first reflective surface is formed in the shape of a ring and around the first transmitting surface and faces toward the image side, a second surface which has a second transmitting surface and a second reflective surface and is formed on the image side, where the second transmitting surface is formed with the center of the

Abstract: An observation optical system has a negative lens unit including a cemented lens, arranged at the most object-side position; an annular reflecting mirror placed on the image side of the negative lens unit, with a reflecting surface facing the image side; and an imaging lens unit arranged on the image side of the negative lens unit and the annular reflecting mirror.

Abstract: There are provided an illumination optical apparatus and an optical apparatus using this illumination optical apparatus that are capable of efficiently collecting light emitted from a light-emitting section for illumination with less illumination nonuniformity, without having to employ a complicated structure. There are provided a light-emitting sections; a lens system for converting a diverging beam emitted from the light-emitting section into a beam of collimated light; an afocal optical system for adjusting the cross-sectional area of a beam of collimated light obtained by the lens array; a fly-eye lens for forming a plurality of light-source images from the collimated light whose cross-sectional area is adjusted by the afocal optical system; and a Koehler illumination optical system that uses the plurality of light-source images formed by the fly-eye lens as a light source.

Abstract: The invention provides a microscope in which the utilization efficiency of light from light sources is high and which can use a bright, uniform line illumination. The microscope includes a plurality of light sources; a fly-eye lens having a plurality of lens elements arrayed in a rectangular shape corresponding to the light sources, the light sources being disposed at the focal points thereof; a cylindrical lens having a flat surface orthogonal to the optical axis of light emitted from the fly-eye lens, and a cylindrical surface whose longitudinal axis is disposed parallel to the arrayed direction of the fly-eye lens; and an objective lens that illuminates a specimen with light from the cylindrical lens.

Abstract: The invention relates to an epi-illumination optical system for microscopes which relies upon a Köhler illumination system using a collective lens array, having simplified adjustment function capable of adjusting the image position of a light source to the back focal position of each microscope objective lens in operable association with microscope objective lens replacement. The invention provides an epi-illumination optical system for microscopes, with an objective lens serving as a condenser lens, which comprises a light source, a collimate lens, and a lens array. The epi-illumination optical system further comprises a projection optical system adapted to project an image of light source formed by collective lens array.