Filter-based spectrometers lack efficiency due to their high spectral selectivity filters, which cut off most of the incident light intensity before reaching the light detector. This may limit applications with fast acquisition needs. To improve efficiency, several works use beam splitters, at the expense of the complexity and size of the system. To overcome these drawbacks, the authors of this article propose an alternative detection approach based on multiple reflections, using a linear detector combined with dichroic spectral filters and a mirror placed parallel to the surface of the filters. The light rays not transmitted by the first encountered filter for detection purposes are no longer lost, but sent back towards the detector to be reconsidered by the neighboring spectral filter transmitting other wavelengths, and so on. This leads to simple design, low cost and increased efficiency. Two modules are proposed, one with classic discrete spectral filters, and one with a continuous filter for spectrum acquisition between 450 and 825 nm. The second module, based on a linear variable filter, enables an efficiency increase factor of up to 100 times compared to systems with the vertical illumination principle.

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