| 摘要 |
A multi-element grating beam splitter with a reflection grating for use in providing a front facet detector signal in an optical system. The multi-element grating beam splitter includes first, second, third, and fourth grating elements for separating a return beam reflected and diffracted from a data track on an optical storage medium into first, second, third and fourth portions, respectively. The grating beam splitter also includes a fifth grating element, which is preferably a reflection grating, for directing a portion of an incident radiation beam onto a front facet detector. The front facet detector signal may be subtracted from a data signal resulting from detection of the first, second, third and fourth portions of the return beam in order to limit the effect of optical source noise on the data signal.
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