| 摘要 |
PROBLEM TO BE SOLVED: To provide a large-aperture zoom optical system which is reduced in size and is capable of providing good image quality over an entire image range by appropriately positioning each lens to correct various aberrations well over an entire zoom range.SOLUTION: An optical system comprises, in order from the object side to the imaging plane side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power. The first lens group comprises, from the object side to the imaging plane side, a front first lens group having negative refractive power and a rear first lens group having negative refractive power, and the second lens group includes, from the object side to the imaging plane side, at least two lenses having positive refractive power and a cemented lens comprising a lens having negative refractive power and a lens having positive refractive power. Zooming and focusing is done in predefined manners. |
