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Grinding Imaging and Reconstruction Instrument (GIRI)


Images of a fossil slab, the lab facility behind Guyot Hall, and a 3D image produced from scan series.


Thanks to funding from Princeton University and the National Science Foundation, the Geosciences lab that houses GIRI (Grinding Imaging and Reconstruction Instrument) opened in February 2013. The lab is dedicated to the digital reconstruction of objects hidden in solid materials through serial grinding and imaging.

GIRI originally was conceived when strange but ubiquitous two-dimensional fossil forms were found in approximately 640 million year old stromatolite reefs from the Trezona Formation in South Australia.  The forms were thought to be part of larger three-dimensional objects, but could not be imaged via X-ray computed tomography scanning techniques because of the very weak density contrasts (both the fossils and matrix are made of calcite).  Manual serial grinding and imaging of these Trezona objects led to the 3D reconstruction of sponge-like organisms suggested to be the oldest body fossil record of animals.

Trezona Formation

GIRI was designed and built to automate the task of grinding and imaging materials like stone and metal, and then using the archive of images to reconstruct 3D models of complex forms hidden in these materials.  The instrument works by employing an automated routine of serial sectioning and imaging.  A precision CNC grinder removes small layers of material.  Then an integrated 80-megapixel camera acquires high-resolution images of the layer.  This process destroys the sample while creating a permanent digital archive of serial images.  Computer vision routines using color and textural isolation algorithms find complex structures and objects.  Hundreds of these segmented slices are combined to create 3D mathematical models.  Quantities such as porosity and permeability can be computed directly from the models.  Models also can be used for hydrodynamic simulations, morphological analysis, and a variety of other computational simulations and analyses. Using GIRI, the lab can resolve 1-micron details over samples as large as 20 x 25 x 40 cm.

In one day, a 5 cm thick sample can be completely imaged at 25-micron horizontal and vertical resolution without human supervision.  Some of the initial projects in the queue include the digital reconstructions of early animal fossils, 3D sedimentary bedforms, chondrules in chondritic meteorites, and targets for geological carbon sequestration.  

For more information on the Princeton Grinder Lab,

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Research at Princeton Spotlight: The Grinding and Imaging Instrument

Maloof, A.C.
, Rose, C.V., Beach, R., Samuels, B.M., Calmet, C.C., Erwin, D.H., Poirier, G.R., Yao, N. and Simons, F.J. 2010, Possible animal-body fossils in pre-Marinoan limestones from South Australia, Nature Geoscience, 3, pp. 653-659, doi:10.1038/ngeo934.   [pdf]