Abstract: The oblique-viewing objective optical system includes a front-side lens group having a negative refractive power, an optical path converting element, an aperture stop, and a rear-side lens group having a positive refractive power. The front-side lens group includes a first lens and a second lens, and the rear-side lens group includes a third lens and a cemented lens which includes a positive biconvex lens and a meniscus-shape negative lens. The first lens is a negative lens having a concave surface directed toward an image-plane side, and the second lens is a single lens having a convex surface directed toward the image-plane side or a cemented lens, and the third lens is a positive lens. The following conditional expressions (1) to (3) are satisfied: 1.6<D1/f<4.7??(1), 1.0<D2/f<3.3??(2), and 9.0<L/f<31.0??(3).

Abstract: The oblique-viewing objective optical system includes a front-side lens group having a negative refractive power, an optical path converting element, an aperture stop, and a rear-side lens group having a positive refractive power. The front-side lens group includes a first lens and a second lens, and the rear-side lens group includes a third lens and a cemented lens which includes a positive biconvex lens and a meniscus-shape negative lens. The first lens is a negative lens having a concave surface directed toward an image-plane side, and the second lens is a single lens having a convex surface directed toward the image-plane side or a cemented lens, and the third lens is a positive lens. The following conditional expressions (1) to (3) are satisfied: 1.6<D1/f<4.7 ??(1), 1.0<D2/f<3.3 ??(2), and 9.0<L/f<31.0 ??(3).

Abstract: An oblique-viewing objective optical system includes in order from an object side, a front-side lens group which includes a negative lens, an optical path converting element, an aperture stop, and a rear-side lens group having a positive refractive power, wherein the rear-side lens group includes a positive lens and a cemented lens having a positive refractive power, and the cemented lens includes in order from the object side a positive lens and a negative lens.

Abstract: An oblique-viewing objective optical system includes in order from an object side, a front-side lens group which includes a negative lens, an optical path converting element, an aperture stop, and a rear-side lens group having a positive refractive power, wherein the rear-side lens group includes a positive lens and a cemented lens having a positive refractive power, and the cemented lens includes in order from the object side a positive lens and a negative lens, and the following conditional expressions (1), (2), (3), (4), and (5) are satisfied: ?2.0<fF/f<?1.3??(1), 1.7<fR/f<2.7??(2), 0.63<|fF/fR|<0.88??(3), 2.4<D1/f<4.4??(4), and 1.1<D2/f<1.7??(5).

Abstract: A depth expansion apparatus includes an image-pickup-optical-system and an image-pickup-device (hereinafter, IPS) configured to form and pick up images A and B in different focus positions, and a depth-expanded-image forming section configured to generate, based on the images A and B, a depth-expanded-image that maintains a relation between a distance from an object point to the image-pickup-optical-system and luminance. When an image side NA of the image A is represented as NA?, a resolution determined by the IPS, as R, an optical path interval between image forming surfaces for the images A and B, as d, NA of an image at a near photographing distance among the images A and B, as NAn, and NA of an image at a far photographing distance among the images A and B, as NAf, the IPS satisfy the following conditional expressions (1) and (2): R×NA?/2?d??(1) 0.05?(NAf/NAn)2?0.9??(2).

Abstract: A depth expansion apparatus includes an image-pickup-optical-system and an image-pickup-device (hereinafter, IPS) configured to form and pick up images A and B in different focus positions, and a depth-expanded-image forming section configured to generate, based on the images A and B, a depth-expanded-image that maintains a relation between a distance from an object point to the image-pickup-optical-system and luminance. When an image side NA of the image A is represented as NA?, a resolution determined by the IPS, as R, an optical path interval between image forming surfaces for the images A and B, as d, NA of an image at a near photographing distance among the images A and B, as NAn, and NA of an image at a far photographing distance among the images A and B, as NAf, the IPS satisfy the following conditional expressions (1) and (2): R×NA?/2?d??(1) 0.05?(NAf/NAn)2?0.9??(2).

Abstract: An endoscope for oblique viewing including an image pickup device, a front lens group having a positive refractive power, a prism disposed on the CCD side of the front lens group, and a rear lens group disposed on the CCD side of the prism and having a positive refractive power.

Abstract: An endoscope for oblique viewing including an image pickup device, a front lens group having a positive refractive power, a prism disposed on the CCD side of the front lens group, and a rear lens group disposed on the CCD side of the prism and having a positive refractive power.

Abstract: An illumination optical system disposed in order to diffuse illumination light emitted from a light source, includes at least one optical device having a roughened optical surface, with the arithmetic average roughness of the roughened surface set in a range of 0.05 to 0.75 [?m].

Abstract: An illumination optical system disposed in order to diffuse illumination light emitted from a light source, includes at least one optical device having a roughened optical surface, with the arithmetic average roughness of the roughened surface set in a range of 0.05 to 0.75 [?m].

Abstract: An optical low pass filter consisting of a diffractive optical element consisting of a plurality of regions which have different imaging characteristics and are joined adjacent to one another so that the imaging characteristics are varied discontinuously. This optical low pass filter is to be used for optical instruments using solid-state image pickup devices and so on.

Abstract: An imaging device has an optical low-pass filter and a solid-state image sensor. The optical low-pass filter includes a plurality of birefringent plates. When a plurality of spaced spots formed by the birefringent plates with respect to incident light are located at adjacent positions such as to be regarded as one spot on the birefringent plates, the birefringent plates are constructed so that a phase difference between light waves passing through the plurality of spaced spots with respect to any wavelength in a visible wavelength region is larger than the wavelength. Thus, the imaging device, even when using many quartz filters, makes the intensities of the spaced spots uniform and can secure the optical low-pass filter free of dependence of wavelength.

Abstract: A TV system for endoscopes is configured to connect to a fiber scope using an image guide fiber bundle and a rigid endoscope using a relay lens system. An image is formed by either the fiber scope or the rigid endoscope on a TV monitor. The camera control unit controls a level of the color difference signal in accordance with spatial frequency components contained in the TV signal. A variable switching unit is provided which allows the electrical circuits of the camera control unit to function selectively in accordance with the characteristics of the image transmission system.

Abstract: An imaging optical system for forming images of objects on an image surface. The optical system includes an aspherical surface that functions to reduce spatial frequency response of the optical system when aperture size of the optical system is reduced within a variable range and adapted so as to eliminate spurious signal by the aspherical surface.

Abstract: An imaging optical system for endoscopes used for re-imaging an image formed by endoscopes, comprising in the order from the object side a first lens unit which has a positive refractive power and a focusing function, a second lens unit which has a negative refractive power and is moved in a definite direction along the optical axis so as to progressively enhance magnification of the imaging optical system when the optical system is zoomed from the wide position to the tele position, and a third lens unit which has a positive refractive power and is moved along the optical axis so as to keep the image point constant regardless of variation of focal length, said first lens unit being adapted as to be moved independently of the other lens units for varying diopteric power within a positive-to-negative range taking the diopter at the infinite object distance for the imaging optical system as zero.

Abstract: An optical system for endoscopes so adapted as to be usable with video endoscopes, comprising an imaging lens system equipped with an aperture stop and a field lens component arranged on the image side thereof, and so designed as to prevent the color shading from being produced by selecting an adequate focal length for the field lens component.