Monolithic integration of flexible spectral filters with CMOS image sensors at wafer level for low cost hyperspectral imaging

To enable industrial adoption of hyperspectral imaging we have developed a unique integrated hyperspectral filter/imager technology. The spectral filters are monolithically deposited/integrated on top of CMOS imagers at wafer level. The materials of the filters are chosen such that they are compatible with the production flows available in most CMOS foundries. The result is a compact & fast hyperspectral imager made with low-cost CMOS process technology. We have demonstrated this hyperspectral technology on two specific instances – a wedge based linescan hyperspectral imager and a tile based snap-shot imager. The line-scan imager is based on a CMOSIS CMV 4000 image sensor and the spectral specifications are 100 spectral bands in the range of 600-1000nm and the FWHM of each band is around 10nm. The snapshot imager is based on a CMOSIS CMV 2000 image sensor with the following spectral specifications: 32 spectral bands in the range of 600-1000nm and also with FWHM of each band around 10nm. Furthermore, both technology is flexible such that many system parameters like number of spectral bands, layout of the filters, FWHM of the filters and the spectral range can be tuned to match specific application requirements. 1. Integrated Spectral Filter Approach Hyperspectral imaging is an advanced imaging technique which captures and processes multiple narrow band images over a spectral range. Capturing spectral images of an object enables detailed analysis and identification of the objects as often different objects contain unique information at different wavelengths. The potential of hyperspectral imaging has been demonstrated for several applications using laboratory setups, it is currently mostly still a scientific tool. Indeed, many of the commercial hyperspectral cameras available today are targeted for the research market, e.g. remote sensing [1] and food science [2]. The adoption of hyperspectral imaging in mainstream industrial applications like machine vision or biomedical has so far been limited, due to the lack of fast, compact, and cost-effective hyperspectral cameras with adequate specifications. (a) (b) Spectral range 600-1000nm # Spectral bands 100 FWHM < 10nm, using collimated light Filter transmission efficiency ~ 85% Imager CMOSIS CMOS CMV 4000 imager #lines/ spectral band 16 #spatial pixels/line 2048 scan rate in #lines/sec 2880