An ultra-high spatial resolution multi-spectral macro-imager for geological samples, Devdigvijay Singh, UG '24 (2263070)
Feature detection in optical imagery relies on color and textural differences between objects of interest and their surroundings. For fifty years, satellite remote sensing has leveraged multispectral imaging, combining information in visible, near infrared, and shortwave infrared channels to better differentiate features such as vegetation or rock types. However, there is a trade-off between spectral and spatial resolution, where higher spectral resolution requires larger pixels that can gather enough light from narrow wavelength bands. Furthermore, at short focal distances, chromatic aberration makes it difficult to capture focused images simultaneously at multiple wavelengths. We describe a new multispectral macro-photography setup that can acquire 1:1 magnification images with 150 megapixel spatial resolution, 8-band (470-940~nm) spectral resolution, and ultraviolet (365~nm) activation. Furthermore, we develop a image deconvolution pipeline using optimized blur kernels to sharpen all images individually. The macro setup is integrated with the Grinding, Imaging, and 3D Reconstruction Instrument (GIRI), so that thousands of multispectral images can be acquired in an automated way, as GIRI grinds through a specimen as thick as 21.5~cm, and/or mosaics over a specimen as large as 20x26~cm. As an example, we demonstrate how multispectral information is crucial for accurate segmentation of features such as archaeocyathid reefs.