Photographic lens of improved near distance performance

Details Photographic lens of improved near distance performance Photographic lens of improved near distance performance

1988-03-30

1989-10-03

Arnold, Bruce Y.

350428, G02B 1522, G02B 964

Patent

active

048712434

ABSTRACT:
A photographic lens comprising, from front to rear, a first lens unit of positive power, a stop, a second lens unit of positive power, a third lens unit of negative power and a fourth lens unit of positive power. The first lens unit has at least one negative lens having a strong concave surface facing the stop, and the second lens unit has at least one negative lens having a strong concave surface facing the stop. When focusing is performed from an infinitely distant object to a close object, the first and second lens units are moved forward in unison, while the third lens unit is moved by a less amount than the amount of movement of the first and second lens units, whereby closeup optical performance is improved.

REFERENCES:
patent: 2537912 (1951-01-01), Reiss
patent: 3815974 (1974-06-01), Momiyama
patent: 4392724 (1983-07-01), Hamanishi
patent: 4553823 (1985-11-01), Kato et al.

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