Patent ID: 10598911

Abstract:
An objective includes a first lens group that has a positive refractive power and a second lens group that has a negative refractive power. The objective includes a first negative lens and satisfies 0.005≤do1/ho1≤0.1  (1)0.005≤hmin/hl≤0.72  (2)10 mm≤L≤100 mm  (3)0.1≤L/f≤31  (4) when do1 is a thickness of the first negative lens, ho1 is an axial marginal ray height on a lens surface on the object side of the first negative lens, hmin is a minimum value of an axial marginal ray height in the second lens group, hl is a height of an axial marginal ray on a lens surface of the objective that is situated closest to the image side, L is a length of the objective, and f is a focal length of the objective.