Optical: systems and elements – Absorption filter – Superimposed or series
Patent
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
Arai Masayuki
Shikano Toru
Shishido Takayasu
Tada Eijiroh
Wakamiya Shunichiro
Asahi Seimitsu Kabushiki Kaisha
Schuberg Darren E.
Spyrou Cassandra
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