Optical design for three wavelength snapshot imaging using a single monochrome camera

Multispectral imaging plays a crucial role in a range of fields, including combustion diagnostics by enabling the measurement of spectral properties within a single exposure. However, a beam-splitting optical configuration enabling three-wavelength snapshot imaging using a single monochrome camera has not yet been reported. Existing approaches typically rely on custom multispectral sensor arrays or multiple synchronized cameras, both of which introduce limitations such as high cost, reduced spatial resolution, or parallax and scaling mismatches. In this work, we present a compact and versatile optical design housed in a 3D-printed enclosure that splits incoming light into three spectral channels using dichroic and turning mirrors, allowing a single monochrome camera to perform custom three-channel imaging across visible and near-infrared bands. The design ensures pixel-level spatial alignment through equal optical path lengths and eliminates parallax errors. We demonstrate its application using the spectral soot emission technique on an ethylene–air co-flow diffusion flame at three detection wavelengths (520, 660, and 840 nm) to infer soot temperature and soot volume fraction distributions.