Abstract: An articulated tube structure for use in an endoscope or the like consists of a number of elementary tubes connected in end-to-end relationship. Between the adjacent elementary tubes are provided springs to urge the articulated tube to bend in one direction. The endoscope is provided with a manipulating box to bend the articulated tube in a desired direction. The articulated tube is spring urged in one direction and is manipulated to bend as desired by operation of pull wires extending through the articulated tube and fixed at their end to the head of the endoscope. The springs may be composed of a series of coil springs provided around one pull wire between adjacent elementary tubes. The spring constant of the coil springs may be increased from the manipulating box to the head so as to bend the articulated tube to more extent in the portion closer to the head than the portion remote from the head.

Abstract: An illumination optical system using optical fiber bundles. The optical fiber bundles are assembled to form an illumination optical system. The exit end faces of the fiber bundles are flat and inclined in different directions to effect a diverging illumination light flux as a whole.

Abstract: A light source provided in an endoscope is controlled to provide a constant comparatively low luminance when the object is to be observed, and to provide a first lowered and then gradually increased luminance when the object is to be photographed. The voltage and consequently, the luminance is first further lowered below the comparatively low luminance for observation when the object is to be photographed and the voltage is then increased so that a high luminance results. A control circuit is connected between a shutter release signal generating circuit and a light source to control the voltage across the light source upon receipt of the shutter release signal.