Abstract: An endoscope 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, focusing from an object point at a long distance to an object point at a short distance is carried out by moving the second group from the object side to an image side, the first group includes a lens having a negative refractive power, the second group includes a lens which is a meniscus lens having a positive refractive power of which a convex surface directed toward the image side, and the third group includes in order from the object side, a lens having a positive refractive power, and a cemented lens of a lens having a positive refractive power and a lens having a negative refractive power, following conditional expressions (1?), (2), and (3) are satisfied, 8<G2f/FL?17.041??(1?) ?0.16<G1f/G2f<?0.04??(2) 0?(R3?R4)/(R3+R4)<0.

Abstract: An objective optical system consists of in order from an object side to an image side, a first group having a positive refractive power, an aperture stop, a second group having negative refractive power, and a third group having a positive refractive power. Focusing is carried out by moving the second group. The objective optical system satisfies the following conditional expression (1?). ?16.6<G2f/FL<?11??(1?) where, G2f denotes a focal length of the second group, and FL denotes a focal length of the overall objective optical system in a normal observation state.

Abstract: An objective optical system includes, in order from an object side: a positive first group; a negative second group; a negative third group; and a positive fourth group, in which the second group and the third group move together toward an image side to perform focusing from an object point at a long distance to an object point at a close distance, and the following conditional expression (2) is satisfied: 0.2<(t34f?t34n)/F<2 (2), where t34f is a distance between the third group and the fourth group at a time of focusing to the object point at the long distance, t34n is a distance between the third group and the fourth group at a time of focusing to the object point at the close distance, and F is a focal length of the overall objective optical system at a time of focusing to the object point at the long distance.

Abstract: An objective optical system consists of, in order from an object side, a first lens group having a negative refractive power, which is stationary all the time, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power, which is stationary all the time. At a time of focusing from an object point at a long distance to an object point at a short distance, the second lens group moves toward the object side and the third lens group moves toward an image side. The following conditional expressions (1), (5), and (7) are satisfied: 2<fG2/f<8??(1) 0.2<(t34f?t34n)/f<0.5??(5) ?8<fG1/f<?2??(7).

Abstract: The objective optical system 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. Focusing is carried out by moving the second lens group. The third lens group includes a positive lens and a cemented lens, and the cemented lens includes a positive lens and a negative lens. A first sub-unit includes a lens positioned on the object side of a predetermined air space and a second sub-lens group includes a lens positioned on an image side of the predetermined air space. The predetermined air space is the maximum air space among the air spaces in the third lens group.

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: The objective optical system consists of order from an object side, a first group having a positive refractive power, a second group having a negative refractive power, and a third group having a positive refractive power, wherein focusing is carried out by moving the second group, and a lens nearest to image is a planoconvex positive lens having a convex surface directed toward the object side, and a flat surface of the planoconvex positive lens is either affixed directly to an image pickup surface or cemented to a cover glass formed on the image pickup surface, and the objective optical system satisfies the following conditional expression (1). 5<ff/f<8??(1) where, ff denotes a focal length of the planoconvex positive lens disposed nearest to image, and f denotes a focal length of the overall objective optical system at the time of normal observation.

Abstract: An objective optical system consists of, in order from an object side, a first lens group having a negative refractive power, which is stationary all the time, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power, which is stationary all the time. At a time of focusing from an object point at a long distance to an object point at a short distance, the second lens group moves toward the object side and the third lens group moves toward an image side. The following conditional expressions (1), (5), and (7) are satisfied: 2<fG2/f<8??(1) 0.2<(t34f?t34n)/f<0.5??(5) ?8<fG1/f<?2??(7).

Abstract: An objective optical system consists of in order from an object side to an image side, a first group having a positive refractive power, an aperture stop, a second group having negative refractive power, and a third group having a positive refractive power. Focusing is carried out by moving the second group. The objective optical system satisfies the following conditional expression (1?). ?16.6<G2f/FL<?11??(1?) where, G2f denotes a focal length of the second group, and FL denotes a focal length of the overall objective optical system in a normal observation state.

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: The objective optical system 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. Focusing is carried out by moving the second lens group. The third lens group includes a positive lens and a cemented lens, and the cemented lens includes a positive lens and a negative lens. A first sub-unit includes a lens positioned on the object side of a predetermined air space and a second sub-lens group includes a lens positioned on an image side of the predetermined air space. The predetermined air space is the maximum air space among the air spaces in the third lens group, and the following conditional expressions (1) and (2) are satisfied: 1.21<fp/f<2.42??(1), and 0.35<tt/f<0.6??(2).

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: The objective optical system consists of order from an object side, a first group having a positive refractive power, a second group having a negative refractive power, and a third group having a positive refractive power, wherein focusing is carried out by moving the second group, and a lens nearest to image is a planoconvex positive lens having a convex surface directed toward the object side, and a flat surface of the planoconvex positive lens is either affixed directly to an image pickup surface or cemented to a cover glass formed on the image pickup surface, and the objective optical system satisfies the following conditional expression (1). 5<ff/f<8??(1) where, ff denotes a focal length of the planoconvex positive lens disposed nearest to image, and f denotes a focal length of the overall objective optical system at the time of normal observation.

Abstract: An objective optical system includes in order from an object side 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, wherein focusing is carried out by moving the second lens group with respect to a change in an object-point distance, and the following conditional expressions (2) and (3) are satisfied: 3<|?|??(2), and 60°<???(3), where, ? denotes a lateral magnification of the overall objective optical system at the time of focusing to an object point at a close distance, and ? denotes the maximum half angle of view at the time of focusing to an object point at a long distance.

Abstract: The objective optical system includes in order from an object side, a first unit having a positive refractive power, a second unit having a negative refractive power, and a third unit having a positive refractive power, and focusing is carried out by moving the second unit, the first unit and the third unit are fixed at the time of focusing, and the first unit G1 includes in order from the object side, a negative lens L1, one of a positive lens and a cemented lens, and a positive lens, and the third unit includes a positive lens, and a cemented lens of a positive lens and a negative lens, and the objective optical system satisfies the following conditional expression (3) ?20<f2/f<?5??(3) where, f2 denotes a focal length of the second unit, and f denotes a focal length of the overall objective optical system in a normal observation state.

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: This endoscope has an observation optical system provided in a distal end of an inserted portion of the endoscope, for observation of an object, and plural illumination optical systems provided in the inserted portion, for illuminating a certain angle of view, wherein one illumination optical system having the widest light distribution is distant from the observation optical system relative to another illumination optical systems having the narrowest light distribution, and the following conditional expression is satisfied, 0.6?|?S·fW/?W·fS|?1.0??(1) wherein fW is a focal length of the widest light distribution optical system, fS is a focal length of the narrowest light distribution optical system, ?W is an outer diameter of the lens nearest to the object within the widest light distribution optical system, and ?S is an outer diameter of the lens nearest to the object within the narrowest light distribution optical system.

Abstract: An objective optical system includes in order from an object side 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, wherein focusing is carried out by moving the second lens group with respect to a change in an object-point distance, and the following conditional expressions (2) and (3) are satisfied: 3<|?|??(2), and 60°<???(3), where, ? denotes a lateral magnification of the overall objective optical system at the time of focusing to an object point at a close distance, and ? denotes the maximum half angle of view at the time of focusing to an object point at a long distance.

Abstract: The objective optical system includes in order from an object side, a first unit having a positive refractive power, a second unit having a negative refractive power, and a third unit having a positive refractive power, and focusing is carried, out by moving the second unit, the first unit and the third unit are fixed at the time of focusing, and the first unit G1 includes in order from the object side, a negative lens L1, one of a positive lens and a cemented lens, and a positive lens, and the third unit includes a positive lens, and a cemented lens of a positive lens and a negative lens, and the objective optical system satisfies the following conditional expression (3) ?20<f2/f<?5 ??(3) where, f2 denotes a focal length of the second unit, and f denotes a focal length of the overall objective optical system in a normal observation state.

Abstract: This endoscope has an observation optical system provided in a distal end of an inserted portion of the endoscope, for observation of an object, and plural illumination optical systems provided in the inserted portion, for illuminating a certain angle of view, wherein one illumination optical system having the widest light distribution is distant from the observation optical system relative to another illumination optical systems having the narrowest light distribution, and the following conditional expression is satisfied, 0.6?|?S·fW/?W·fS|?1.0??(1) wherein fW is a focal length of the widest light distribution optical system, fS is a focal length of the narrowest light distribution optical system, ?W is an outer diameter of the lens nearest to the object within the widest light distribution optical system, and ?S is an outer diameter of the lens nearest to the object within the narrowest light distribution optical system.