By monolithically integrating a tiled array of optical interference filters on top of standard CMOS image sensors, imec (Leuven, Belgium) has developed a compact, high-resolution “snapshot” multispectral camera. The prototype device can acquire multispectral image cubes (256 × 256 pixels at 32 wavelengths from 600 to 1000 nm) at a speed of approximately 30 spectral cubes per second (30 frames/s) at daylight conditions and as many as 340 frames/s using higher illumination levels that are typical for machine-vision applications.
The 32 spectral filters are integrated with a 2 Mpixel CMOS image sensor; commercially available microlens arrays and optical components complete the OEM sensor module by duplicating the scene simultaneously onto each of the filter elements. The tiled filter array is comprised of individual Fabry-Perot filters made of a transparent layer (cavity) with two mirrors on each side. The length of the cavity defines the central wavelength of the optical filter and the reflectivity of the mirrors defines the full-width half-maximum (FWHM) bandwidth of the filter, which is about 10 nm for the filters in the prototype design. The snapshot imager can resolve the sharp reflectance-spectra absorption spikes in an erbium oxide wavelength calibration standard, indicating its utility in spectral characterization applications. Contact Andy Lambrechts at [email protected].
