Optical filters having spatially variant microreplicated layers

A technique comprising:

• illuminating a sample with a light source to obtain a characteristic light;
• passing the characteristic light through a spatially variant microreplicated layer optically coupled to a wavelength selective filter to transmit filtered characteristic light to each region of a plurality of regions of the wavelength selective filter at a respective incidence angle of a plurality of incidence angles, each respective incidence angle associated with a known narrow band of a plurality of narrow bands;
• sensing a respective intensity of the filtered characteristic light transmitted by each respective region of the wavelength selective filter at a respective sensor element of a plurality of sensor elements;
• and
• comparing the filtered characteristic spectrum sensed by the plurality of sensor elements with a known reference spectrum associated with a species by curve fitting each sensed respective intensity against the known reference spectrum, wherein the curve fitting comprises matching each sensed respective intensity with a respective expected intensity associated with the respective narrow band associated with the respective region that transmitted the respective intensity of the filtered characteristic light;
• and
• determining the presence of the species in the sample based on the comparison.

A technique comprising:

• illuminating a sample with a broad-band light source to obtain a characteristic light;
• passing the characteristic light through an optical filter to transmit filtered characteristic light to a broad-band sensor at each respective predetermined angle of a plurality of predetermined angles;
• determining a cumulative spectral power distribution in angle space of the filtered characteristic light by sensing a respective intensity of the filtered characteristic light transmitted at each respective predetermined angle;
• converting the cumulative spectral power distribution in angle space to a cumulative spectral power distribution in wavelength space based on the angular dispersion of a band edge of the optical filter;
• determining a spectral power distribution of the filtered characteristic light by determining a mathematical derivative of the cumulative spectral power distribution in wavelength space;
• comparing the spectral power distribution to a known reference spectral power distribution of a species;
• and
• determining the presence of the species in the sample based on the comparison.