Optical system for non-flexible endoscopes

摘要

A relay lens system used in an observation optical system which is to be disposed in an insert section is disclosed. The relay lens system comprises a plurality of relay lens units at least one of which allows longitudinal chromatic aberration to remain in an undercorrected tendency and at least another of which allows longitudinal chromatic aberration to remain in an overcorrected tendency, thereby correcting longitudinal chromatic aberration favorably in the relay lens system as a whole.