Rotatable, oblique-viewing stereoendoscope including a dual-pupil aperture divided to a first pupil and a second pupil, a proximal objective assembly positioned proximally to the dual-pupil aperture, a first image sensor configured to detect a first image focused by the proximal objective assembly and a second image sensor configured to detect a second image focused by the proximal objective assembly, a relay system positioned distally to the dual-pupil aperture and a front optical system positioned distally to the relay system, the front optical system including a folding prism, wherein the front optical system is configured to reimage the dual-pupil aperture at a distal end thereof, thereby producing an image of the first pupil and an image of the second pupil at a distal pupil plane and wherein the stereoendoscope does not include a negative power lens positioned distally to the folding prism.

To provide an image pickup unit that can prevent axis deviation of a movable lens barrel and obtain high-quality picked-up image, a stopper member is positioned and fixed in a state in which the stopper member is abutted against an outer circumferential surface of a rear group lens barrel, movement of a movable lens barrel to a retraction side along a photographing optical axis is restricted by contact of a stopper section of the stopper member and an operation rod, and a movable lens is held in a position for realizing a second focal length.

An optical system for an endoscope includes an objective and a reversal system arranged after the objective. The reversal system includes at least one reversal stage for projecting the distal intermediate image as a proximal intermediate image into a proximal intermediate image plane. The reversal system imprints on the proximal intermediate image a first longitudinal chromatic aberration referred to a predetermined wavelength from the visible spectrum and a predetermined wavelength from the near infrared range. The objective imprints on the distal intermediate image a second longitudinal chromatic aberration referred to the predetermined wavelength from the visible spectrum and the predetermined wavelength from the near infrared range. The second longitudinal chromatic aberration has the opposite sign relative to the first longitudinal chromatic aberration, which reduces the longitudinal chromatic aberration caused by the reversal system in the proximal intermediate image.

An objective optical system for an endoscope consists of a front group, an aperture stop, and a positive rear group in order from an object side. The front group consists of a negative first lens having a smaller absolute value of a curvature radius of a lens surface on an image side than that on an object side, and one or more parallel planar members of which an incidence surface and an emission surface are perpendicular to an optical axis, in order from the object side. The rear group consists of a positive second lens and a cemented lens in which a negative third lens, and a positive fourth lens are joined together in order from the object side and a cemented surface has a concave surface toward the image side. A predetermined conditional expression is satisfied.

The present specification is directed towards endoscopes, such as colonoscopes, that provide a broader field of view and allow extended access of surgical tools and also enable efficient packing of all necessary elements in the tip section, while maintaining their functionality. Also described are methods and systems for capturing and displaying still and video images using an endoscope corresponding to a left-side looking, a front-looking and a right-side looking viewing element of an endoscopic tip generated in a native aspect ratio.

Color information with higher sensitivity than color information in a primary color system is detected. A laser scanning observation apparatus includes at least three light sources, a multiplexer, and a controller. The at least three light sources emit pulsed laser light with different wavelengths within the visible light spectrum. The multiplexer combines the laser light emitted from the at least three light sources. The controller causes different combinations of two light sources among the at least three light sources to emit laser light in sequence and periodically.

An imaging lens assembly includes a dual molded lens barrel and at least one lens element. The dual molded lens barrel includes a light transmitting portion and a light absorbing portion. The light transmitting portion includes an effective optical section. The light absorbing portion is connected to the light transmitting portion, wherein a plastic material and a color of the light absorbing portion are different from a plastic material and a color of the light transmitting portion, and the light absorbing portion includes a barrel section. The lens element is disposed in the barrel section.

An objective optical system for endoscope includes, a first group having a positive refractive power, an aperture stop, and a second group having a positive refractive power, wherein the first group includes a first lens having a negative refractive power, and a second lens having a positive refractive power, the second group includes a cemented lens, and the cemented lens includes a third lens having a positive refractive power and a fourth lens having a negative refractive power, and the following conditional expressions (1), (2), (3), (4), (7) and (9) are satisfied:

0.13≦La/Lb≦0.17   (1),

−2.7≦f4/f≦−2.2   (2),

−0.7≦(ne2×f2)/(ne4×f4)≦0   (3),

2.5≦νd3/νd4≦3.5   (4)

−2.6≦r2o/rcc≦−2   (7), and

−1.2≦r2i/f2≦−0.9   (9).

An objective lens including a first lens group immovable in changing magnification from a normal observation state to a close-up observation state, a second lens group arranged nearer to the image side than the first lens group and moving along the optical axis in the change of magnification, a third lens group arranged nearer to the image side than the second lens group and immovable in the change of magnification, and an aperture stop arranged between the second lens group and an image plane and immovable in the change of magnification, and the objective lens satisfying the following condition:
1.24<|F.sub.1f/F.sub.n|<1.8
where F.sub.1f denotes the focal length of a lens that is placed nearest to the object side in the first lens group and F.sub.n denotes the focal length of the whole system in the normal observation state.

A negative lens, for an oblique-view endoscope objective, has a first face with a first optical surface and a second face with a second optical surface opposing the first optical surface, the second optical surface being a concave optical surface, wherein a recess is formed in the second face adjacent to the concave optical surface. An endoscope objective, that includes a deflection prism having an entrance face and further including a negative lens, the negative lens having a first face with a first optical surface and a second face with a second optical surface opposing the first optical surface, the second optical surface being a concave optical surface. The negative lens is mounted on a distal planar surface of the deflection prism such that a rim encompassing the concave optical surface abuts the distal planar surface of the deflection prism.