| 摘要 |
<p>Zoom lens including, from its object side, a first lens unit (U1) being positive which does not move for zooming, a second lens unit (U2) being negative which moves along an optical axis for zooming, a third lens unit (U3) being negative which moves along the optical axis for zooming so as to correct image plane variation due to zooming and a fourth lens unit (U4) being positive which does not move for zooming. The fourth lens unit (U4) includes a two sub-units (U4a, U4b) being positive which are separated by the largest air interval within the fourth lens unit (U4). Abbe constants, partial dispersion ratios, and coefficients of the refractive index variation due to the temperature variation are appropriately set for lens materials forming the third lens unit (U3), the first and the second sub-units (U4a, U4b).</p> |
