Endoscope image pickup optical system

Abstract

An endoscope optical system is capable of obtaining favorable endoscopic images at all times by overcoming the conventional disadvantages that diagnosis is hindered by image quality disturbance due to the increase in pixel density resulting from the reduction in pixel pitch of solid-state image pickup devices and also due to the conventional arrangement of an objective front optical element in an optical system having a short focal length or in an optical system having a large F-number. In an image pickup apparatus using a monochromatic high-density solid-state image pickup device in which the average pixel pitch (H+V)/2 of the pixel pitch H in the horizontal direction and the pixel pitch V in the vertical direction with respect to the monitor scanning line is not more than 4.65 μm, or using an interline type color high-density solid-state image pickup device in which the average pixel pitch (H+V)/2 is not more than 3.1 μm, the volume Vof an air layer between a plane-parallel plate (F) closest to the object side in the image pickup optical system and a piano-concave negative lens (L) satisfies the following condition:mm  ()