Early multispectral imaging devices generally adopted external optical splitting structures: prisms and rotating filter wheels switch different bands, resulting in bulky size, complex mechanical structures and slow scanning speed. They could only be used in laboratories and large‑scale industrial equipment, unable to be integrated into miniature terminals such as smartphones, wearables and automotive cameras.
With the maturity of nano‑coating and semiconductor photolithography processes,Pixel‑Level Filter Array (PLFA)has become a revolutionary technology in the global multispectral field. During CMOS wafer fabrication, it deposits nanoscale narrow‑band optical filter films corresponding to specific bands precisely above each pixel photodiode via Physical Vapor Deposition (PVD) and photolithography etching, realizing chip‑level spectral splitting of “one pixel, one band” without any external optical components.
Its technical evolution is divided into three generations. The first generation is theBayer‑style RGB‑NIR arraywith 4 fixed bands, mostly used for consumer‑grade health detection. The second generation is thecheckerboard multi‑band filter arraywith 8–16 bands, suitable for mid‑range automotive and industrial scenarios. The third generation is thecustomized high‑density narrow‑band filter array, up to 41 bands (e.g. Sony IMX454) with precise 10nm band intervals for industrial‑grade material identification.
Compared with traditional solutions, PLFA has three core advantages:ultra‑miniaturizationdown to millimeter‑level chips;high‑frame‑rate snapshot imagingwith complete spectra output in one single frame without mechanical movement;low‑cost mass productioncompatible with standard CMOS processes. Currently, Imec, Sony and onsemi all adopt this technical route, pushing multispectral technology from large professional equipment to full scenarios including consumer electronics, automotive perception and miniature industrial inspection.
