| 摘要 |
PURPOSE:To uniform the distribution of light intensity by setting up the format of the change of light transmissivity of the 1st and 2nd ND filter elements so that the increasing directions of displacement from reference positions are reversed each other. CONSTITUTION:The 1st ND filter element 1 is constituted so that the light transmissivity is changed on the basis of a prescribed changing format in accordance with the displacement from a reference position (line S1) in the previously fixed specific arrow X1 direction. In the 2nd ND filter element 2, the format of the change of light transmissivity corresponding to the displacement from a reference position (line S2) is the same as that of the 1st ND filter element 1. The direction (arrow X2) for changing the light transmissibity in said specific direction is reversed to that of the 1st ND filter element 1.
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