Abstract: An endoscope system in which a normal observation image and a near observation image are photographed by a solid-state image sensor upon operation of a focus adjustment device for changing a focal length and a working distance satisfies:

Abstract: A TV observation system for endoscopes has an illumination system including a light source for emitting light to illuminate an object and a light transmitting section for transmitting the light from the light source to the distal end of an endoscope. The light transmitting section is constructed with a single fiber and satisfies a condition:.PHI..sub.1 >.PHI..sub.2where .PHI..sub.1 is the area of the entrance end of the single fiber and .PHI..sub.2 is the area of the exit end thereof.

Abstract: An imaging apparatus for endoscopes includes an endoscope; a TV camera head incorporating, at least, a solid-state image sensor; and a TV photographic adapter incorporating at least one part of an optical system for forming an image obtained by the endoscope on the solid-state image sensor. At least one of the TV camera head and the TV photographic adapter is hermetically sealed by dampproof members so that autoclaving treatment can be received.

Abstract: An optical system for endoscopes which comprises a stop having a variable aperture and is configured so as to produce spherical aberration for preventing an image surface thereof from being shifted in a direction opposite to the object side by narrowing the aperture of the stop, whereby the optical system is free from insufficiency in brightness and degradation in resolution thereof on a side farther from the optical system within a depth of field thereof, and has another side of the depth of field brought close to the optical system.

Abstract: An endoscope apparatus includes an optical system for forming an image of an object; a solid-state image sensor for receiving the image formed by the optical system; an illuminating device for irradiating the object with illuminating light; a light control device for changing the brightness of the illuminating light; a stop device whose aperture is variable, disposed in the optical system; a detecting device for detecting the brightness of the image of the object; and a control device for controlling the stop device and the light control device so that the intensity of a signal output from the solid-state image sensor is kept nearly constant in accordance with brightness information derived from the detecting device. In this way, the endoscope apparatus always maintains the optimum brightness of the image and ensures a practical pan-focus state in which a user's operation load is reduced.

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: 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.