Retrofocus type lens

Details Retrofocus type lens Retrofocus type lens

1996-07-29

1997-09-09

Epps, Georgia Y.

Optical: systems and elements

Lens

With field curvature shaping

359717, 359793, G02B 900, G02B 1318, G02B 904

Patent

active

056662289

ABSTRACT:
In a negative first lens group composed of four sheets of lenses and a positive second lens group composed of four sheets of lenses, the lens in each lens group placed closest to the enlargement side is formed as a plastic lens having an aspheric surface, while predetermined conditional expressions are satisfied, whereby various kinds of aberration are made favorable and influence of changes in the plastic lens upon temperature is suppressed. A first lens group comprising a negative first lens (L1) made of a plastic lens having an aspheric surface, a negative second lens (L2), a negative third lens (L3), and a positive fourth lens (L4) and a second lens group comprising, a positive fifth lens (L5) made of a plastic lens having an aspheric surface, a negative sixth lens (L6), a positive seventh lens (L7), and a positive eighth lens (L8) are successively disposed from the enlargement side, while satisfying the following conditional expressions:

REFERENCES:
patent: 5311363 (1994-05-01), Ono et al.
patent: 5319495 (1994-06-01), Yamada

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