| 摘要 |
<p>A high-performance objective optical system adaptable to image pick-up elements with a large number of pixels enables focusing according to the variation of the objective point distance and causes less variation of the angle of field when such focusing is carried out. The objective optical system is configured from at least three groups (G1, G2, G3). Since at least one lens group (G2) among the groups moves, focusing according to the variation of the objective point distance is possible. The following conditional expressions are satisfied. ?f>60 ··· (1)-1 ?n>60 ··· (1)-2 0.8<?n/?f<1.2 ··· (2) where ?f is the maximum half angle of field (°) in the case of far-distance objective point observation, and ?n is the maximum half angle of field (°) in the case of near-distance objective point observation.</p> |
