| 摘要 |
A detector for detecting polarised radiation (24) comprising means (10, 18, 20) for modulating the polarisation of incoming radiation as a function of time which modulating means (10, 18, 20) has one or more opaque regions (19, 22), means (14) for detecting said modulated radiation, means (17) for deriving a reference signal indicative of the frequency of modulation applied to the modulating means (10, 18, 20), which reference signal is derived as a result of said one or more opaque regions (19, 22) on the modulating means (10, 18, 20), and means for ensuring that the reference signal and the resultant polarisation signal are in phase.
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