Abstract: In order to perform a superior observation, in which halation is less likely to occur, by achieving uniform illumination from near sites to far sites and by ensuring a satisfactory light distribution and brightness, both when performing normal observation and when performing near-field observation, an endoscope apparatus includes an observation optical system that is provided at a distal end of an inserted portion of the endoscope apparatus to observe an observation subject and a plurality of illumination optical systems that are provided in the inserted portion and that illuminate the same viewing field by distributing illumination light emitted from a light source over the observation subject, wherein, of the plurality of the illumination optical systems, the distance from the observation optical system to the widest-angle illumination optical system is smaller than the distance from the observation optical system to the narrowest-angle illumination optical system.

Abstract: An objective optical system consists of, from an object side to an image side: a first lens group having positive optical power; a second lens group having negative optical power; and a third lens group having positive optical power, wherein the first lens group includes, from the object side to the image side, a first lens having negative optical power and a second lens having positive optical power, and the second lens group is moved according to a change in an object distance to perform focusing, and the following conditional expressions are satisfied: ?19<f2/f1<?3.5 0.5<v/f<1.1 where f2 is a focal length of the second lens, f1 is a focal length of the first lens, v is an amount of movement of the second lens group, and f is a focal length of an entire system during the most distant view observation.

Abstract: An endoscope tip part has impact resistance even when applied to a thin endoscope, and the light distribution characteristics thereof can be improved even at a wide angle of view. An endoscope tip part includes a tip part main body that is attached to the tip of an insertion section of an endoscope and a positive-power transparent-plastic tip lens that is integrated with the tip part main body through two-color molding. The tip lens is a lens that is located closest to an object, among optical elements constituting an illumination optical system of the endoscope, and the tip part main body is provided with an insertion hole into which two positive-power rear lenses that will be disposed behind the tip lens are inserted.

Abstract: An endoscope includes an observation optical system that allows a magnified observation close to a subject, and illumination optical systems. In a close observation, ITM is a maximum brightness within an observation view field angle, and ITC is a center brightness. In a normal observation IWC is a center brightness, and IWS is a brightness at a position of 80% of a maximum view angle. The following is satisfied: 0.3<ITC/ITM<0.45 0.15<IWS/IWC<0.25 0.3<fLfT/?LIH<0.6 where fL is a focal length of each of the entire illumination optical systems, fT is a focal length of the entire observation optical system in a maximum magnification, ?L is an outer diameter of a lens that is farthest on an object side of each illumination optical system, and IH is a maximum image height of the observation optical system.

Abstract: An objective optical system consists of, from an object side to an image side: a first lens group having positive optical power; a second lens group having negative optical power; and a third lens group having positive optical power, wherein the first lens group includes, from the object side to the image side, a first lens having negative optical power and a second lens having positive optical power, and the second lens group is moved according to a change in an object distance to perform focusing, and the following conditional expressions are satisfied: ?19<f2/f1<?3.5 0.5<v/f<1.1 where f2 is a focal length of the second lens, f1 is a focal length of the first lens, v is an amount of movement of the second lens group, and f is a focal length of an entire system during the most distant view observation.

Abstract: Provided is an endoscope objective optical system that is constituted of, in order from the object side, a positive first group, an aperture stop, and a positive second group, wherein the first group is constituted of a negative first lens whose surface on the object side is flat and a positive second lens; the second group is constituted of a combined lens formed of a positive third lens and a negative fourth lens; and Conditional Expressions (1) to (3) are satisfied. F31, F32, and f are the focal lengths of the third lens, the fourth lens, and the entire system, respectively; and R3 and R4 are the radii of curvature at the object-side surface and the image-side surface of the second lens, respectively. 1.2<f31/f<1.55 . . . (1), ?2.8<f32/f<?1.98 . . . (2), and 0.38<|R4+R3|/|R4?R3|<0.77 . . . (3).

Abstract: An endoscope tip part has impact resistance even when applied to a thin endoscope, and the light distribution characteristics thereof can be improved even at a wide angle of view. An endoscope tip part includes a tip part main body that is attached to the tip of an insertion section of an endoscope and a positive-power transparent-plastic tip lens that is integrated with the tip part main body through two-color molding. The tip lens is a lens that is located closest to an object, among optical elements constituting an illumination optical system of the endoscope, and the tip part main body is provided with an insertion hole into which two positive-power rear lenses that will be disposed behind the tip lens are inserted.

Abstract: An endoscope system has a light source apparatus and an endoscope including an illumination optical system and an objective optical system. At least the objective optical system of the endoscope is provided with an adjustable diaphragm, and in a light path in one of the light source apparatus, the illumination optical system, and the objective optical system, an insertable/retractable filter for observation for special light is provided. The adjustable diaphragm performs a closing operation or an opening operation only when the filter for observation for special light is inserted into the light path.

Abstract: Provided is a high-performance objective optical system which is compatible with a high-pixel-count image acquisition device, in which focusing can be achieved according to a change in object point distance and which has sufficient depth of field at the individual object point distances. Provided is an objective optical system (1) including, in order from an object side, a first group (G1), a second group (G2), and a third group (G3), in which the first group (G1) includes, in order from the object side, a plano-concave lens (L1) and a meniscus lens (L2) whose convex surface is towards an image side and in which the second group (G2) includes a positive meniscus lens whose convex surface is towards the object side and moves in the direction of an optical axis to perform focusing.

Abstract: An objective optical system including an objective optical system having a field angle of 140° or larger and including a front group, an aperture stop, and a positive rear group arranged in that order from an object side. The front group has at least one aspherical surface and includes a negative first lens disposed closest to the object side and satisfying the following conditional expression: 0?r2/r1<0.24, 0.1<|g2/g1|<2.2 and ?1.8<f1/fl<?0.8, where r1 denotes the radius of curvature of the object side of the first lens, r2 denotes the radius of curvature of an image side of the first lens, g1 denotes the focal length of the front group, g2 denotes the focal length of the rear group, f1 denotes a focal length of the first lens, and fl denotes the focal length of the entire system.

Abstract: An illumination optical system includes a prism disposed on an incident optical axis and a lens that is disposed between the light source and an incident surface of the prism or between an emitting surface of the prism and an illuminated object, at least one of the reflection surfaces being a transmission/reflection surface. Additionally, an illumination optical system includes a prism having a surface that is disposed so as to obliquely intersect with an incident optical system, that transmits a part of the entering light to be emitted therefrom, and that deflects at least part of the rest of the light in a direction that intersects with the incident optical axis to be emitted therefrom. Furthermore, an illumination optical system has a rod lens that is disposed so that a longitudinal direction thereof is inclined with respect to an incident optical axis is provided.

Abstract: A system includes a first prism pair that converts beams emitted from a subject and having two substantially parallel optical axes arranged side-by-side in one direction into beams arranged side-by-side in a direction intersecting the aforementioned side-by-side direction; and a second prism pair that performs conversion to reduce the distance between the optical axes of the two beams converted by the first prism pair and that has exit surfaces arranged side-by-side in a direction perpendicular to the side-by-side arrangement direction before entering the first prism pair. The first prism pair includes a first parallelogram prism that reflects, twice, the beam containing one of the two optical axes in a first plane containing one of the optical axes, and a second parallelogram prism that reflects, twice, the beam containing the other of the two optical axes in a second plane containing the other optical axis and parallel to the first plane.

Abstract: Provided is an imaging optical system and an image acquisition apparatus that can be suitably used in a small-diameter endoscope while having an ultra-wide angle of view. Provided is an image optical system (1) containing, in order from the object side, a negative front group (FG), an aperture stop (S), and a positive back group (BG), wherein the front group (FG) contains, in order from the object side, a negative first lens (L1) and a negative second lens (L2), and the back group (BG) contains a cemented lens (CL) constituted of at least three lenses (L5, L6, L7) joined together.

Abstract: An objective optical system including an objective optical system having a field angle of 140° or larger and including a front group, an aperture stop, and a positive rear group arranged in that order from an object side. The front group has at least one aspherical surface and includes a negative first lens disposed closest to the object side and satisfying the following conditional expression: 0?r2/r1<0.24, 0.1<|g2/g1|<2.2 and ?1.8<f1/fl<?0.8, where r1 denotes the radius of curvature of the object side of the first lens, r2 denotes the radius of curvature of an image side of the first lens, g1 denotes the focal length of the front group, g2 denotes the focal length of the rear group, f1 denotes a focal length of the first lens, and fl denotes the focal length of the entire system.

Abstract: The invention provides a high-performance objective lens that is capable of implementing focusing relative to an object point distance change with no or little angle-of-view change, and is well compatible with a high-pixel type imaging device. The objective optical system comprises, in order from an object side thereof, a first group of negative power, a second group of positive power, an aperture stop, and a third group of positive power. Only the second group moves thereby implementing focusing relative to an object point distance change, with satisfaction of the following conditions (1)-1, (1)-2 and (8): ?f>60??(1)-1 ?n>60??(1)-2 ?1.2<f1/ff<?0.6??(8) where ?f is a maximum half angle of view (°) upon viewing at a far distance object point, ?n is a maximum half angle of view (°) upon close-up viewing, f1 is a focal length of the first lens group, and ff is a focal length of the whole system upon viewing at a far distance. See FIG. 1.

Abstract: An illumination optical system includes a prism disposed on an incident optical axis and a lens that is disposed between the light source and an incident surface of the prism or between an emitting surface of the prism and an illuminated object, at least one of the reflection surfaces being a transmission/reflection surface. Additionally, an illumination optical system includes a prism having a surface that is disposed so as to obliquely intersect with an incident optical system, that transmits a part of the entering light to be emitted therefrom, and that deflects at least part of the rest of the light in a direction that intersects with the incident optical axis to be emitted therefrom. Furthermore, an illumination optical system has a rod lens that is disposed so that a longitudinal direction thereof is inclined with respect to an incident optical axis is provided.

Abstract: Provided is an imaging optical system and an image acquisition apparatus that can be suitably used in a small-diameter endoscope while having an ultra-wide angle of view. Provided is an image optical system (1) containing, in order from the object side, a negative front group (FG), an aperture stop (S), and a positive back group (BG), wherein the front group (FG) contains, in order from the object side, a negative first lens (L1) and a negative second lens (L2), and the back group (BG) contains a cemented lens (CL) constituted of at least three lenses (L5, L6, L7) joined together.

Abstract: The inventive objective lens for endoscopes has independently a zooming function and a focusing function, and is capable of magnified viewing. The objective lens has an angle of view (2?) of 100° or greater, and comprises a positive first group G1, a negative second group G2 and a positive third group G3. The third group G3 comprises a positive first (3-1) subgroup G31 and a positive second (3-2) subgroup G32. A subgroup in at least the second group G2 moves to (1) bring about a change in the focal length of the whole system and (2) correct an image position for movement in association with a focal length change, and one subgroup in the second group G2 and the third group G3 moves to the image side from a longer side toward a shorter side of the working distance (WD) to (3) correct the focal position for movement in association with a working distance change.

Abstract: A system includes a first prism pair that converts beams emitted from a subject and having two substantially parallel optical axes arranged side-by-side in one direction into beams arranged side-by-side in a direction intersecting the aforementioned side-by-side direction; and a second prism pair that performs conversion to reduce the distance between the optical axes of the two beams converted by the first prism pair and that has exit surfaces arranged side-by-side in a direction perpendicular to the side-by-side arrangement direction before entering the first prism pair. The first prism pair includes a first parallelogram prism that reflects, twice, the beam containing one of the two optical axes in a first plane containing one of the optical axes, and a second parallelogram prism that reflects, twice, the beam containing the other of the two optical axes in a second plane containing the other optical axis and parallel to the first plane.

Abstract: Provided is a high-performance objective optical system which is compatible with a high-pixel-count image acquisition device, in which focusing can be achieved according to a change in object point distance and which has sufficient depth of field at the individual object point distances. Provided is an objective optical system (1) including, in order from an object side, a first group (G1), a second group (G2), and a third group (G3), in which the first group (G1) includes, in order from the object side, a plano-concave lens (L1) and a meniscus lens (L2) whose convex surface is towards an image side and in which the second group (G2) includes a positive meniscus lens whose convex surface is towards the object side and moves in the direction of an optical axis to perform focusing.