The next generation of multispectral instruments requires significant improvements in both spectral band
customization and portability to support the widespread deployment of application-specific optical sensors. The
benefits of spectroscopy are well established for numerous applications including biomedical instrumentation, industrial sorting and sensing, chemical detection, and environmental monitoring. In this paper, spectroscopic (and
by extension hyperspectral) and multispectral measurements are considered. The technology, tradeoffs, and
application fits of each are evaluated.
In the majority of applications, monitoring 4-8 targeted spectral bands of optimized wavelength and bandwidth provides the necessary spectral contrast and correlation. An innovative approach integrates precision spectral filters
at the photodetector level to enable smaller sensors, simplify optical designs, and reduce device integration costs. This method supports user-defined spectral bands to create application-specific sensors in a small footprint with
scalable cost efficiencies.
A range of design configurations, filter options and combinations are presented together with typical applications
ranging from basic multi-band detection to stringent multi-channel fluorescence measurement. An example
implementation packages 8 narrowband silicon photodiodes into a 9x9mm ceramic LCC (leadless chip carrier) footprint. This package is designed for multispectral applications ranging from portable color monitors to purpose-
built OEM industrial and scientific instruments. Use of an eight-channel multispectral photodiode array typically
eliminates 10-20 components from a device bill-of-materials (BOM), streamlining the optical path and shrinking the
footprint by 50% or more.
A stepwise design approach for multispectral sensors is discussed – including spectral band definition, optical
design tradeoffs and constraints, and device integration from prototype through scalable volume production. Additional customization options are explored for application-specific OEM sensors integrated into portable devices using multispectral photodiode arrays.