| 摘要 |
The optical collimator comprises a circular polarisation selector (8) followed by a spherical semi-reflective mirror (9), a quarter-wave plate (10) and a linear reflective polariser (11).In variants of the design the polarisation selector can be in the form of a circular polariser, or a linear reflective polariser followed by a quarter-wave plate, and it can have at least one coating of cholesteric liquid crystals. The collimator can incorporate a mixer in the form of a semi-reflective plate, or a reflective linear polariser and a quarter-wave plate, situated in front of the mirror.The mirror (9) has a holographic treatment so that it does not reflect 50 per cent of the light except in a given frequency range. ADVANTAGE - Reduced dimensions.
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