摘要 |
Described herein is a quadrant detector which comprises a holographic optical element (10) and a plurality of detector elements (22, 24, 26, 28). The holographic optical element (10) is designed to have four quadrants (12, 14, 16, 18) each of which directs radiation incident thereon to an associated detect or element (22, 24, 26, 28). Signals from the detector elements (22, 24, 26, 28 ) are processed individually to optimise the performance of each detector element.
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