| 摘要 |
A method and apparatus involve an optical element having a passband with a center wavelength, and filtering radiation having first and second portions that arrive along a path of travel extending to the optical element. The first portion includes radiation inside the passband, and the second portion includes radiation above and below the passband. The optical element transmits one of the first and second portions of the radiation therethrough, and reflects the other of the first and second portions of the radiation therefrom. The optical element is supported for a range of movement relative to the path of travel. As the optical element moves through the range of movement, the center wavelength changes.
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