| 摘要 |
An optical system includes at least one of a movable lens unit movable in an optical axis direction and a fixed lens unit that is not movable in the optical axis direction. The at least one lens unit includes a plurality of refractive optical elements. The refractive optical elements are made of resin and have focal lengths of the same sign. When phii is a refractive power, with respect to d-line, of the ith refractive optical element from an object side, phiG is a refractive power of a negative lens in the lens unit including the refractive optical elements, and phia is an average refractive power, with respect to d-line, of the refractive optical elements, phii, phiG, and phia are adequately set.
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