PROBLEM TO BE SOLVED: To realize rapid autofocus in a rigid endoscope system. A rigid endoscope system includes a tube, an objective lens, an eyepiece, an image sensor, a detection light source that emits detection light projected onto an observation target, and a tube that is reflected by the observation target. A light receiving sensor that receives the detection light that has passed through the inside of the eyepiece, a spectroscopic optical element that disperses the light beam emitted from the eyepiece in each direction of the image sensor and the light receiving sensor, and the light received after the detection light is emitted by the detection light source. An arithmetic unit that measures the time until light is received by the sensor and calculates the distance to the observation target, and an imaging optical system that forms an image of a part of the light source emitted from the eyepiece on the imaging sensor. It is provided with a focus adjustment unit that adjusts the focus by moving the focus adjustment lens included in the imaging optical system in the optical axis direction based on the distance calculated by the unit. [Selection diagram] Fig. 1【課題】硬性内視鏡システムにおいて迅速なオートフォーカスを実現する。【解決手段】硬性内視鏡システムは、管体と、対物レンズと、接眼レンズと、撮像センサと、観察対象へ投射される検出光を射出する検出光源と、観察対象で反射し、管体の内部を通過した検出光を受光する受光センサと、接眼レンズから射出される光束を撮像センサと受光センサのそれぞれの方向へ分光する分光光学素子と、検出光が検出光源で射出されてから受光センサで受光されるまでの時間を計測して観察対象までの距離を演算する演算部と、接眼レンズから射出された一部の光束を撮像センサへ結像させるための結像光学系と、演算部で演算された距離に基づいて結像光学系に含まれる焦点調整レンズを光軸方向へ移動させることにより焦点調整を行う焦点調整部とを備える。【選択図】図１
