Specifying Optical Filters

The burgeoning market for high-performance diagnostic and biomedical instruments, such as fluorescence microscopes and Raman spectroscopy systems, is driving up demand for rigorous optical filters. However, this article highlights a crucial cost-saving strategy: developers frequently over-specify filter requirements, unnecessarily increasing manufacturing complexity and product cost.

The high-precision required in biomedical applications—demanding blocking better than OD6 and passband transmission over 90%—results in inherently thick coatings. Achieving the necessary Center Wavelength (CWL) and Full Width Half Maximum (FWHM) tolerances (e.g., ±2 nm) requires a dense coating to prevent detrimental spectral shift caused by humidity or temperature changes. The most efficient deposition technologies for this demanding performance are Advanced Plasma Source (APS) and magnetron sputtering.

To control costs, developers must perform system analysis to determine the actual performance needs. For instance, specifying OD6 blocking when OD4 suffices dramatically increases manufacturing time and cost due to the resulting thicker coating.