A spherical mask to compensate for cos(3) and cos(4) illuminance variation.
A dyed or pigmented gelatin mask cast in a shallow spherical mold cavity can provide excellent compensation for the cos(3)alpha or cos(4)alpha fall-off of illuminance on a flat surface. Computed data are shown for the imperfection of correction under a variety of geometric conditions, and some typical applications are described.
De Palma
J J
JJ
Research Laboratories, EastmanKodak Company, Rochester, New York, USA.
Pickering
R D
RD