| 摘要 |
<p>The imaging optical system has a first positive lens element convex toward the object side, a second negative lens element concave toward the image side, a third lens element having both surfaces with a region, in which the lens section is located on the object side than the intersection with the optical axis, a fourth positive lens element convex toward the image side with at least one surface having an aspherical shape and inflection points, and a fifth negative lens element concave toward the image side.
The optical system satisfies the expressions: 0.5 < f �¢ 1 / f < 0.67 , 0.3 < f �¢ 4 / f < 0.63
The third lens element satisfies the expressions: - 0.4 < f / R �¢ 1 _L �¢ 3 < 0.2 , - 0.6 < f / R �¢ 2 _L �¢ 3 < 0.05
where f, f1, f4 denote focal lengths of the entire system, the first lens element, and the fourth lens element, and R1_L3, R2_L3 denote paraxial diameters of the object-side surface and the image-side surface of the third lens element.</p> |
