Transmissive filter for correcting illuminance distribution

Details Transmissive filter for correcting illuminance distribution Transmissive filter for correcting illuminance distribution

1988-06-20

1990-03-06

Sugarmann, Scott J.

350438, 350448, G02B 520

Patent

active

049060813

ABSTRACT:
A transmissive filter for correcting illuminance distribution is positioned between a lens for forming an image of an illuminated original on an image forming surface and the image forming surface, or between the original and the image forming lens, and having transparent areas for passing light therethrough and opaque areas for blocking light, for correcting illuminance irregularities on the image forming surface. The transmissive filter has lowest transmittance around an effective pupil formed by projecting an exit pupil of the lens onto the filter when the filter is disposed between the lens and the image forming surface, or lowest transmittance around an effective pupil formed by projecting an entrance pupil of the lens onto the filter when the filter is disposed between the original and the lens. The transmittance is progressively higher concentrically in a stepwise manner toward an axial center and an outer periphery of the filter.

REFERENCES:
patent: 3669528 (1972-06-01), Richardson
patent: 3728009 (1973-04-01), Fedotowsky et al.
patent: 4030817 (1977-06-01), Westell
patent: 4457593 (1984-07-01), Yokota

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