Patent ID: 6433940
Filing Date: 2002-08-13
Classification: G02B

Abstract:
A zoom optical system comprising, in order from an object side: a first lens unit having positive refractive power; a second lens unit having positive refractive power; and a third lens unit having negative refractive power, wherein a magnification is changed from a wide position to a tele position by moving the lens units on the object side so as to widen an airspace between said first lens unit and said second lens unit and narrow an airspace between said second lens unit and said third lens unit, and wherein said zoom optical system satisfies the following conditions (1), (2), (3) and (4):fT/fW>3.8â€ƒâ€ƒ(1) 0(fTa)âˆ’S(fW)]/(fTaÂ·fW)<0.2â€ƒâ€ƒ(2) 0.8(fTa)/(fTaâˆ’fW)<1.05â€ƒâ€ƒ(3) 0(G1)/fTa<0.023â€ƒâ€ƒ(4) wherein reference symbols fT and fW represent focal length of the zoom optical system at the wide position and the tele position respectively, a reference symbol fTa designates an optical focal length in a focal length region exceeding 3.8 times of the focal length at the wide position, a reference symbol S(fW) denotes a distance as measured from a most object side surface to a most image side surface at the wide position, a reference symbol S(fTa) represents a distance as measured from a most object side surface to a most image side surface at the focal length of fTa, a reference symbol L(fTa) designates a distance as measured from the most object side surface to image at the focal length of fTa and a reference symbol H(G1) denotes a distance as measured from the most object side surface to a front principal point of the first lens unit G1.