| 摘要 |
<p>This imaging optical system, imaging apparatus, and digital device are provided with an optical system having a positive-negative-positive-negative four-lens configuration, a surface at the maximum effective diameter of a second lens is positioned further toward the object side than a surface apex thereof, a fourth lens has inflection point positioned apart from an intersection point with the optical axis, and the focal length (f1) of the first lens, the focal length (f) of the entire system, the curvature radii (RS1, RS3) of the object-side surfaces of first and second lenses, the curvature radii (RS2, RS4) of the image-side surfaces of the first and second lenses, the distance (d2) on the optical axis between the first and second lenses, the total optical length (TL) of the entire system, the maximum half field angle (W), the Abbe number (nu4) of the fourth lens, and the maximum image height (Y) satisfy the following conditional expressions: 0.7 < f1/f < 5, -0.8 < (RS1 + RS2)/(RS1 - RS2) < 3, -3 < (RS3 + RS4)/(RS3 - RS4) < 2, 0.03 < d2/TL < 0.2, 2W > 72, nu4 > 50, 0.55 < Y/TL < 0.8.</p> |
