A High-Resolution Multispectral Macro-Imager for Geology and Paleontology

Abstract

Accurately assessing the shape, size, and modality of features in rock samples is a longstanding problem in geology. Recent advances in machine learning have introduced the possibility of performing these tasks through automated image analysis. To leverage these methods for geological and paleontological applications, we first need a way to acquire high-resolution images of polished slabs and thin sections with a field of view large enough to fit samples containing crystals, fossils, bedforms, etc. We describe a new multispectral setup that can acquire images at ~3.76 mm per pixel spatial resolution over a 21 cm 2 field of view, equipped with 8-band (470-940 nm) spectral resolution, plus a band for ultraviolet (365 nm) fluorescence. Additionally, we present a 5-band (470-940 nm) light table with automated rotating polarizers, which allows use of the camera as a high-throughput transmitted light thin section imager. The use of color bands outside the visible spectrum, as well as the registration of multiple cross-polarized rotations, encode rock properties that heighten image contrast and improve the accuracy of machine learning models. Our setup and methods provide an efficient way to (1) build reproducible image archives of rock specimens to complement field observations, (2) classify and segment those images, and (3) quantitatively compare lithofacies and fossil assemblages.

A Novel Technique for Producing Three-Dimensional Data Using Serial Sectioning and Semi-Automatic Image Classification

“…3a,11,12). Both the lighting and camera system can be upgraded independently of the MSG-818PC-NC, enabling GIRI to take advantage of future advances, including, but not limited to, improved optics, higher spatial or spectral resolution data capture, and/or nonoptical fluorescence (e.g., Manzuk et al, 2022). Typically, lighting is provided by two Lowel Blender adjustable LED lamps (Fig.…”

“…The lamps are fitted with polarizing film inserts, which help reduce glare. To leverage sample response to different wavelengths of illumination, multiple Smart Vision LED Brick Lights, each emitting a specific wavelength of light, can be utilized instead (e.g., Manzuk et al, 2022). In such instances, each light is actuated independently via serial communication and multiple photographs (each with exposure times tailored to the specific lighting conditions) are captured (Manzuk et al, 2022).…”

“…The RCam is equipped with an 80 megapixel Phase One digital back that has a camera sensor measuring 4.04 × 5.37 cm and comprising pixels that are each 5.2 × 5.2 μm in size. If utilizing multiple wavelengths of light, the RCam instead is equipped with an achromatic 150 megapixel Phase One digital back, which has a camera sensor measuring 4.04 × 5.37 cm and comprising pixels that are each 3.76 × 3.76 μm in size (Manzuk et al, 2022). Lenses are coupled to the digital back with a Schneider Kreuznach electronic shutter that is controlled using serial commands delivered over USB.…”