| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a zoom lens which has a zoom ratio of roughly 16x, F-numbers of 2.0 or less at short and long focal ends, and an inexpensive configuration with roughly 15 to 16 lenses and which offers sufficient aberration correction especially in the near-infrared wavelength range, compactness, and resolution compatible with image sensors with 1 to 5 million pixels.SOLUTION: A zoom lens includes, in order from the object side, a first lens group G1 having positive refractive power, second lens group G2 having negative refractive power, a third lens group G3 having negative refractive power, and fourth lens group G4 having positive refractive power. When zooming from a short focal end to a long focal end, the second lens group G2 moves toward the image side and the third lens group G3 moves, while other lens groups are stationary. The first lens group G1 and fourth lens group G4 have diffractive surfaces. A ratio of focal lengths of diffractive surfaces of the first lens group G1 and fourth lens group G4 to focal lengths of the first lens group G1 and fourth lens group G4 is set within a predetermined range.</p> |
