Signal collection spectrometer

A spectrometer for measuring frequency components of light from a sample, comprising:

• a light guide for receiving light from the sample, wherein the light guide has an entrance surface disposed for the light from the sample to enter the light guide, and an exit surface for the light to exit the light guide, the light guide has a longitudinal direction and the exit surface extends on a side of the light guide along the longitudinal direction;
• a linear variable filter disposed alongside the light guide and adjacent to the exit surface of the light guide, wherein the light exiting the light guide through the exit surface passes through the linear variable filter and is filtered by the linear variable filter, the linear variable filter comprises an array of bandpass filters having different filtering wavelength bands that depend on positions of the bandpass filters in the linear variable filter;
• a detector array comprising a plurality of photodetectors, the detector array being disposed adjacent to the linear variable filter to receive the light passing through and filtered by the linear variable filter.