Patent ID: 7457047
Filing Date: 2008-11-25
Classification: G02B

Abstract:
1. A zoom optical system comprising, in order from an object side: a first lens unit with positive refracting power; a second lens unit with negative refracting power; a third lens unit with positive refracting power; a fourth lens unit with positive refracting power; and an aperture stop interposed between the second lens unit and the fourth lens unit, at least, the first lens unit, the second lens unit, and the third lens unit being moved upon zooming so that spacings between individual lens units are varied, the first lens unit being composed of at most two lens elements, a focal length of the whole zoom optical system being changed at least 3.5 times, the following conditions being satisfied: where Tt is a total length of the zoom optical system at a telephoto position, the total length of the zoom optical system being a distance from a first surface of the zoom optical system to an image plane of the zoom optical system, Tw is a total length of the zoom optical system at a wide-angle position, fw is a focal length of the zoom optical system at the wide-angle position, and en30 is a position of an entrance pupil relative to an angle of view of 30° at the wide-angle position.