ND filter

Details ND filter ND filter

1998-04-22

2000-06-20

Spyrou, Cassandra

Optical: systems and elements

Absorption filter

Superimposed or series

359885, 359888, G02B 522

Patent

active

060784423

ABSTRACT:
In a concentric ND filter in which multi-layered circular ND filter elements whose diameter is decreased stepwise toward the uppermost layer from the lowermost layer are concentrically provided on a first transparent substrate, a surrounding space of the concentrically multi-layered ND filter elements defined by and between the surface of the transparent substrate and the surface of the central ND filter layer of the smallest diameter is filled with a transparent adhesive.

REFERENCES:
patent: 3981565 (1976-09-01), Karasawa
patent: 4298275 (1981-11-01), Chitchlow et al.
patent: 4922280 (1990-05-01), Koshino et al.
patent: 5111343 (1992-05-01), Harrigan

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