| 摘要 |
An imaging optical system includes in order from an object side thereof a front lens unit having a negative refracting power, an aperture stop, and a rear lens unit having a positive refracting power, and the front lens unit having a negative refracting power includes in order from the object side, a first lens having a negative refracting power, and the rear lens unit having a positive refracting power includes in order from the object side, a second lens which is a positive lens, a third lens which is a negative lens, and a fourth lens which is a positive lens, and the imaging optical system satisfies the following conditional expressions (1) and (2) <?in-line-formulae description="In-line Formulae" end="lead"?>1.6<|fG1|/FA<5 (1)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>1.2<fG2/FA<5 (2)<?in-line-formulae description="In-line Formulae" end="tail"?> where, FA denotes a focal length of the overall imaging optical system, fG1 denotes a focal length of the front lens unit having a negative refracting power, and fG2 denotes a focal length of the rear lens unit having a positive refracting power.
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