| 摘要 |
A half tone screen of a graphic camera is uniformly exposed by a pinhole light projector positioned off axis with respect to the main optical projection axis. A light diffuser is positioned intermediate a light source and the pinhole has a variable density light attenuator pattern consisting of a plurality of circular lines for attenuating the light passing through the diffuser and aperture in a manner to produce uniform illumination of the half tone screen.
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