| 摘要 |
An apparatus for improved contrast in projection optical systems consists of a polarizing beam splitter (PBS) in combination with two or more waveplates whose fast exes are aligned perpendicular to each other. The apparatus has an effective broadband frequency response that is better than that of the individual retarders acting alone, and through the selection of a birefringence factor and thickness of the individual retarders, wavelength dependencies are minimized.
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