Abstract: An objective optical system includes, in order from an object side: a first group having a negative refractive power; a second group having a positive refractive power; and a third group having a positive refractive power, in which the first group and the third group are fixed and the second group is movable, the first group includes at least two lenses having a negative refractive power, the third group includes, in order from the object side, a 3-1st group having a positive refractive power, a 3-2nd group having a negative refractive power, a 3-3rd group having a positive refractive power, and a 3-4th group having a positive refractive power, and the following conditional expression (1)?? is satisfied: 1.5?Bk/f3?6??(1)??.

Abstract: An objective optical system for endoscope includes a first lens having a negative refractive power, a second lens having a positive refractive power, an aperture stop, a third lens having a positive refractive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, and a sixth lens having a positive refractive power. The second lens is a meniscus lens having a convex surface directed toward an image side and the third lens is a meniscus lens having a convex surface directed toward the image side. A cemented lens having a positive refractive power is formed by the fourth lens and the fifth lens. The sixth lens is cemented to an image sensor, and the following conditional expression (1??) is satisfied: 1?(r3f+r3r)/(r3f?r3r)?5??(1??).

Abstract: An objective optical system includes, in order from an object side: a first group having a negative refractive power; a second group having a positive refractive power; and a third group having a positive refractive power, in which the first group and the third group are fixed and the second group is movable, the first group includes at least two lenses having a negative refractive power, the third group includes, in order from the object side, a 3-1st group having a positive refractive power, a 3-2nd group having a negative refractive power, a 3-3rd group having a positive refractive power, and a 3-4th group having a positive refractive power, and the following conditional expression (1)?? is satisfied: 1.5?Bk/f3?6??(1)??.

Abstract: An objective optical system for an endoscope includes, in order from an object side, a first lens having a negative refractive power, a second meniscus lens having a positive refractive power and having a convex surface directed toward an image side, an aperture stop, a third lens having a positive refractive power, and a cemented lens of a fourth lens having a positive refractive power and a fifth lens having a negative refractive power.

Abstract: An objective optical system for endoscope includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. At a time of focusing, the first lens group and the third lens group are fixed, and the second lens group moves. The third lens group consists of a front group having a positive refractive power and a rear group having a positive refractive power. The front group includes one cemented lens and the rear group includes one single lens, and the following conditional expressions are satisfied: 1?fG3f/fG3r?5, 0.1?dG3fr/dG3r?1, ?8?fc/rc??2, and ?7?fG2/fG3??2.

Abstract: An objective optical system for endoscope includes a first lens having a negative refractive power, a second lens having a positive refractive power, an aperture stop, a third lens having a positive refractive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, and a sixth lens having a positive refractive power. The second lens is a meniscus lens having a convex surface directed toward an image side and the third lens is a meniscus lens having a convex surface directed toward the image side. A cemented lens having a positive refractive power is formed by the fourth lens and the fifth lens. The sixth lens is cemented to an image sensor, and the following conditional expression (1??) is satisfied: 1?(r3f+r3r)/(r3f?r3r)?5??(1??).

Abstract: An objective optical system for endoscope includes, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. At a time of focusing, the first lens group and the third lens group are fixed, and the second lens group moves. The third lens group consists of a front group having a positive refractive power and a rear group having a positive refractive power. The front group includes one cemented lens and the rear group includes one single lens, and the following conditional expressions (1-1), (1-2), (4-1), and (4-2) are satisfied: 1?fG3f/fG3r?5??(1-1) 0.1?dG3fr/dG3r?1??(1-2) ?8?fc/rc??2??(4-1) ?7?fG2/fG3??2??(4-2).

Abstract: An objective optical system for endoscope consists of in order from an object side, a first lens having a negative refractive power, a second meniscus lens having a positive refractive power and having a convex surface directed toward an image side, an aperture stop, a third lens having a positive refractive power, and a cemented lens of a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, and the objective optical system for endoscope satisfies the following conditional expressions (1-1), (1-2), and (1-3). ?0.6?f1/f45??0.18??(1-1) 0.2?(r3f+r3r)/(r3f?r3r)?1??(1-2) 0.15?d34/d4?0.

Abstract: An objective optical system for endoscope includes, in order from an object side: a first lens having a negative refractive power; a second meniscus lens having a positive refractive power with a convex surface thereof directed toward the object side; an aperture stop; a third lens having a biconvex shape, and a cemented lens having a positive refractive power as a whole, in which a fourth lens having a biconvex shape and a fifth lens having a negative refractive power are cemented.

Abstract: There is provided an objective optical system for endoscope which is small-sized, and has a favorable optical performance and fast F-number. An objective optical system for endoscope comprises in order from an object side: a first lens having a negative refractive power; a second meniscus lens having a positive refractive power with a convex surface thereof directed toward the object side; an aperture stop; a third lens having a biconvex shape, and a cemented lens having a positive refractive power as a whole, in which a fourth lens having a biconvex shape and a fifth lens having a negative refractive power are cemented, wherein the objective optical system for endoscope satisfies the following conditional expressions (1), (2), and (9). ?3?f1/Ih??1.2??(1) 0.25?L3_5/L?0.7??(2) 0.2?r2/r3?0.

Abstract: A small-sized objective optical system for an endoscope having in order from an object side, a first negative lens which is planoconcave, a second meniscus lens having a convex surface directed toward an image side, a third positive meniscus lens having a convex surface directed toward the object side, a positive lens unit, and a cemented lens in which, a positive lens and a negative lens are cemented. Focusing is carried out by moving the third positive meniscus lens along an optical axis, and the second meniscus lens is a negative lens.

Abstract: There is provided an objective optical system for endoscope, which is small-sized and has a favorable optical performance. The objective optical system for endoscope includes in order from an object side, a first negative lens which is planoconcave, a second meniscus lens having a convex surface directed toward an image side, a third positive meniscus lens having a convex surface directed toward the object side, a positive lens unit, and a cemented lens in which, a positive lens and a negative lens are cemented. Focusing is carried out by moving the third positive meniscus lens along an optical axis, and the second meniscus lens is a negative lens, and the objective optical system for endoscope satisfies the following conditional expression (1), and satisfies at least one of the following conditional expressions (4-1) and (4-2). 2.3?fp/Ih?5??(1) ?1.5?r2/r3??0.28??(4-1) ?0.2?r2/r4??0.

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 optical unit includes: a plurality of lenses that form an object image on an image plane that is a light-receiving surface of a CCD; an aperture diaphragm; and an infrared absorption filter disposed on the image plane side relative to the aperture diaphragm, the infrared absorption filter including coating surfaces resulting from a YAG laser cut-off film and an LD laser cut-off film that each cut off predetermined laser light being formed respectively, and an F number FNO, a maximum image height IH, and a distance ?d between a paraxial image formation position in a ghost optical path on which a light beam emitted from the aperture diaphragm BI is reflected by the image plane and further reflected by the coating surface and reaches the image plane again and the image plane satisfy (Expression 1): 0.75<|FNO·IH/?d|<2.0??(Expression 1).

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: The invention relates to an image apparatus for endoscopes, which makes sure easier viewing especially at a peripheral portion of a screen while taking care of the observing angle of view and size of an optical system. The image apparatus comprises an optical system adapted to form an optical image of an object, an image pickup device adapted to convert the formed optical image into electric signals to obtain image data, and an image processing means adapted to move and transform a position of the optical image acquired by the image pickup device. A radiation direction magnification is transformable by the image processing means independently from a concentric direction magnification, and a magnification for a conformal object is higher at a peripheral portion than at a central portion of a screen.

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: 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 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.