| 摘要 |
The filter provides uniform contrast over a whole frame and no luminance difference between center and edges of a frame. The manufacturing method includes the steps of; (A)forming a black coated layer(2) of which density becomes lower as the distance from center of the filter base becomes far off; and (B) forming a protective layer(3) so that the beam is transmitted uniformly at the center and the edge of the black coated layer.
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