| 摘要 |
A polarization insensitive tunable optical filter system combines an interference filter or the like with a quarter wave plate and a retro-reflector. The retro-reflector is situated and aligned to intercept light reflected from the filter, and the quarter wave plate is disposed between the filter and the retro-reflector. Hence, the pass signal reflected off the filter a first time passes through the quarter wave plate a first time, reflects off of the retro-reflector, passes through the quarter wave plate a second time, and reflects off of the filter a second time.
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