| 摘要 |
The invention relates to a tuneable filter comprising: at least two coupled Fabry-Perot filters each Fabry-Perot filter having an FP transmission spectrum comprising a plurality of peaks; characterised in that the tuneable filter further comprises a tuning means for altering at least one of the FP spectra until substantial coincidence is achieved between at least one peak from each FP spectrum and wherein the filters each comprise a cavity of differing optical thickness. |
