Fabrication of multispectral imaging technology driven MEMS-based micro-arrayed multichannel optical filter mosaic

Multispectral imaging is becoming a new powerful tool in a wide range of biological studies by adding spectral, spatial and temporal dimensions to tissue abnormity and the underlying biological processes. A standard spectral imaging setup includes two major components, a band pass selection device (such as liquid crystal tunable filter and diffraction grating) and a scientific-grade monochrome camera. Contemporary multispectral imaging technologies typically use traditional optical filters e.g., filter wheels, a generalized Lyot filter, an electrically tunable filter, multiple-band pass filters or the methods of dispersing light, e.g., optic-acoustic crystals. The instrumented systems are bulky, expensive, require multiple exposures or extensive post-processing to align up multiple images of pure spectral components. Recently a break-through technology has emerged to instrument multispectral imaging technology into handheld real-time devices using miniaturized filter mosaic containing micro-arrayed multiple channel band-pass optical filters. The filter mosaic can be directly placed near the focal plane immediately in front of the imaging sensor of an off-shelf CCD/CMOS camera, with potentially one such micro-filter covers one pixel of the imaging sensor. This paper reveals the technical details of how such a micro-arrayed multi channel optical filter is fabricated using traditional multi-film vacuum deposition and the modern micro-lithography technologies. The selection of different coating materials, their structures and effects to the adhesive forces between film and substrate, the spatial resolution, width of passing band, and the transmittance of the resulting miniaturized optical filter is discussed.