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Method to Produce Grain-Scale Digital Images of Large Experimental Sedimentary Deposits and Other Imperfectly Flat Stratigraphy

¹ National Center for Earth-surface Dynamics (NCED), St. Anthony Falls Laboratory, 2 Third Ave SE, Minneapolis, Minnesota 55414, U.S.A.
² National Center for Earth-surface Dynamics (NCED), St. Anthony Falls Laboratory, 2 Third Ave SE, Minneapolis, Minnesota 55414, U.S.A.

We describe a novel system for creating high-resolution digital scans of imperfectly flat surfaces of arbitrary size. The system was developed to image experimental stratigraphic sections but could also be adapted to imaging small outcrops, cut sections, or slabbed cores. At the heart of the scanner is a telecentric lens system which maintains constant image size even as distance to the subject changes. This lens is used to collect thousands of small overlapping digital images which, after being corrected for lighting and lens distortions, are then assembled into a single continuous image that contains no trace of the original image boundaries. The telecentric lens allows imaging surfaces that are only approximately flat, e.g., ones with marks and divots created by cutting tools. Arbitrarily large, essentially perfect digital images whose resolution can be made arbitrarily fine by adjusting lens magnification and image frame size are produced by this system. The size of the composite image is limited only by the available computer file system and the size of the camera positioning system. We describe how this method works and how it is applied to the acquisition of images in experimental stratigraphy.

Design details are discussed at the end of the paper. More information including CAD drawings and source code is available to researchers by contacting the authors.