Olympus Optical Company, Ltd.

Minoru Oshikiri

Juro Kikuchi

Toshihide Nozawa

A zoom lens system which enables favorable image quality to be obtained even when it is focused on an object at a short distance. The zoom lens system has a 1-st lens unit (G1) of positive power, a 2-nd lens unit (G2) of positive power, and a 3-rd lens unit (G3) of negative power. Zooming from the wide end toward the tele end is effected by increasing the spacing between the 1-st lens unit (G1) and the 2-nd lens unit (G2) while reducing the spacing between the 2-nd lens unit (G2) and the 3-rd lens unit (G3). The 2-nd lens unit (G2) of positive power is composed of a negative sub-lens unit (G2N) and a positive sub-lens unit (G2P), and an aperture stop is disposed between the 1-st lens unit (G1) and the 2-nd lens unit (G2) (as shown by S') or between the negative sub-lens unit (G2N) and the positive sub-lens unit (G2P) (as shown by S). When focusing is to be effected on an object at a short distance at, at least, the wide end, the negative sub-lens unit (G2N) and the positive sub-lens unit (G2P) are simultaneously moved toward the object side in parallel to the optical axis with the spacing therebetween gradually enlarged.

Zoom lens system

A wide-angle zoom lens system having a high vari-focal ratio comprising, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a negative refractive power and a third lens unit having a positive refractive power, and configured so as to change a magnification thereof by varying at least one airspace reserved between the first lens unit and the second lens unit. Owing to a fact that a distance as measured between principal points of the first lens unit and the second lens unit is defined within a certain definite range, the zoom lens system has a wide field angle of 70.degree. or larger, a high vari-focal ratio of approximately 4, a telephoto ratio of approximately 1.5 at a tele position thereof and a compact size, and can be manufactured at a low cost.

Wide-angle zoom lens system having a high vari-focal ratio

A taking optical system capable of trimming photography, wherein as the trimming magnification increases, the lens performance for the central area of an image frame on a negative film improves, thereby enabling photographs of excellent image quality to be obtained over the entire photography mode range, from ordinary photography to trimming photography. The taking optical system includes a plurality of lens groups arranged to enable at least two photography modes to be changed over from one to the other, the photography modes including a first mode in which a first image forming area is set for photography, and a second mode in which a second image forming area smaller than the first image forming area is set for photography. When the photography mode shifts from the first mode to the second mode, the spacing between the lens groups is changed, thereby effectively correcting aberrations in the second image forming area. Similar aberration correction can also be made by adjusting at least one of the surface configuration, refractive index and refractive index distribution of an optical element of the taking optical system.

Taking optical system capable of trimming photography

The invention provides a compact zoom lens system which has an angular coverage from wide angle to moderate telephoto and makes a relatively bright and parallax-free TTL finder possible and in which a first unit 11 having a positive power as a whole is located on the side proximate to the object. The lens system includes a reflective means 13c located more closely to the image side than the first unit 11 for guiding incident light to a finder subsystem and a movable lens unit that moves for zooming. The movable lens unit comprises a sub-unit 13a having a positive power as a whole and located on the object side of the reflective means 13c and a sub-unit 13b having a negative power as a whole and located on the images side of the reflective means 13c, or alternatively a sub-unit having a negative power as a whole and located on the object side of the reflective means and a sub-unit having a positive power as a whole and located on the image side of the reflective means. The movable lens unit has an aperture stop located therein or adjacent thereto.

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Tokyo, Japan

Minoru Oshikiri