Minolta Company, Ltd.

Minolta Camera Co., Ltd.

Masakuni Tai

Hideki Nagata

Soh Ohzawa

Hiroyuki Matsumoto

Katsuhiro Takamoto

A variable magnification optical system for projecting images from a small-sized, high-resolution display device consists of, from the projection side, a first lens unit having a positive optical power, a second lens unit having a negative optical power, a third lens unit having a negative optical power, and a fourth lens unit having a positive optical power and kept in a fixed position during magnification adjustment. The optical system achieves magnification adjustment by moving at least the second and third lens units along the optical axis, and has at least one negative lens element in the second lens unit, at least one negative lens element in the third lens unit, and at least one positive lens element in the fourth lens unit made of lens materials having predetermined anomalous dispersions and predetermined Abbe numbers.

Variable magnification optical system

A zoom lens system of the invention is double telephoto type zoom lens system having a positive/negative/positive/negative refractive power arrangement. During zooming from the wide angle side toward the telephoto side, the first through fourth lens units move such that the distance between the first and second lens units increases and the distance between the third and fourth lens units decreases. The refractive power of the first lens unit and the refractive power of the fourth lens unit are appropriately prescribed so that an adequate back focal lens distance is preserved.

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Machida, Japan

Masakuni Tai