Assessment of varying width illumination in hyperspectral push-broom system for scattering anisotropy measurements

摘要

Various illumination geometries are being used in push-broom hyperspectral systems (PB-HSI), where a specific choice of the geometry might affect the imaging results, especially when imaging turbid samples. In this study, the effect of the illumination line width on the reflected radiance is explored. Since the PB-HSI images a very narrow line on the sample, the hypothesis is that by varying the illumination line width tissue optical parameters can be assessed because of their effects on mean free transport path in the tissue. A numerical simulation of light propagation within tissue samples was performed by a 3D CUDA Monte Carlo (MC). A custom MC allowing various illumination geometries and different scattering phase functions was developed. Sets of realistic tissue optical properties, including different scattering phase functions, are used to simulate a bulk tissue. For each set of optical properties, reflectances are computed for illumination line widths varying between 0.1 to 20 mm in the 400-1000 nm spectral range. A prominent effect of the line width on the reflected fraction of photons in correlation with the optical properties was found. This study results demonstrated that the illumination geometry, namely the illumination line width, significantly affects the PB-HSI images of turbid samples. Thus, the geometry should be considered when performing the imaging and analyzing the obtained images. In addition, by varying the illumination line width during the imaging, scattering anisotropy of a sample and other optical properties could be assessed.