Optical system for endoscopic objective lens

The invention discloses an optical system for an endoscopic objective lens. The optical system for the endoscopic objective lens successively comprises a first lens group with negative refractive power, a diaphragm and a second lens group with positive refractive power from an object side to an image side, and meets the following conditional expression: f/H(L1r1)> 2.5, H(L1r1)/IMH< 0.6, wherein fis a focal length of the optical system for the endoscopic objective lens, H(L1r1) is a height corresponding to main light which passes through the surface of the object side of the first lens group and corresponds to the maximum image height when in conventional observation, and IMH is a maximum image height on a corresponding chip light sensing surface when in the conventional observation. The optical system for the endoscopic objective lens has the characteristics of high pixel, quite small aperture and excellent depth of field. 本发明公开了种内窥用物镜光学系统，自物体侧到像侧依次包括具有负光焦度的第透镜组、光阑和具有正光焦度的第二透镜组，满足以下条件式：f/H(L1r1)