Zoom lens

Details Zoom lens Zoom lens

1993-08-12

1996-10-22

Nguyen, Thong

Optical: systems and elements

Lens

With variable magnification

359686, 359687, G02B 1514

Patent

active

055683215

ABSTRACT:
A zoom lens of four-unit construction which comprises, in succession from the object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power. During the zooming from the short focus side to the long focus side, the first lens unit and the fourth lens unit are moved toward the object side, the second lens unit is moved so that the air gap thereof with respect to the first lens unit may monotonously increase, and the third lens unit is moved so that the air gap thereof with respect to the second lens unit may monotonously decrease. The fourth lens unit is comprised, in succession from the object side, of a first positive lens having its convex surface of sharp curvature facing the image plane side, and a cemented lens comprising a meniscus positive lens having its concave surface facing the object side and a negative lens having its concave surface of sharp curvature facing the object side, the meniscus positive lens and the negative lens being cemented together.

REFERENCES:
patent: 4299454 (1981-10-01), Betensky
patent: 4632519 (1986-12-01), Takahashi
patent: 4653872 (1987-03-01), Takahashi
patent: 4776680 (1988-10-01), Tanaka
patent: 4789226 (1988-12-01), Ogata
patent: 4890904 (1990-01-01), Ito
patent: 4995707 (1991-02-01), Hashimoto
patent: 5000551 (1991-03-01), Shibayama
patent: 5042927 (1991-08-01), Ogawa et al.
English Abstract of the Japanese reference No. 62-270,910.

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