Abstract
This work presents the development of a flexible microscopic chemical imaging platform for cultural heritage that utilizes wavelength-tunable oblique illumination from a point source to obtain per-pixel reflectance spectra in the VIS–NIR range. The microscope light source can be adjusted on two axes allowing for a hemisphere of possible illumination directions. The synthesis of multiple illumination angles allows for the calculation of surface normal vectors, similar to phase gradients, and axial optical sectioning. The extraction of spectral reflectance images with high spatial resolutions from these data is demonstrated through the analysis of a replica cross-section, created from known painting reference materials, as well as a sample extracted from a painting by Pablo Picasso entitled La Miséreuse accroupie (1902). These case studies show the rich microscale molecular information that may be obtained using this microscope and how the instrument overcomes challenges for spectral analysis commonly encountered on works of art with complex matrices composed of both inorganic minerals and organic lakes.
| Original language | English (US) |
|---|---|
| Article number | 27 |
| Journal | Heritage Science |
| Volume | 8 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 1 2020 |
Funding
This collaborative initiative is part of the Center for Scientific Studies in the Arts broad portfolio of activities, made possible by the Andrew Mellon foundation. In addition this work made use of the EPIC and Keck II facilities of Northwestern University\u2019s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. This work also made use of the MatCI Facility supported by the MRSEC program of the National Science Foundation (DMR-1720139) at the Materials Research Center of Northwestern University. We thank Sandra Webster-Cook and Kenneth Brummel at the Art Gallery of Ontario for the motivation to better understand Picasso\u2019s painting materials and methods using a cross-section removed from their painting. The authors also wish to thank Emeline Pouyet for help in preparing the Picasso cross-section through microtomy.
Keywords
- Dictionary learning
- Micro analysis
- Oblique illumination
- Optical sectioning
- Picasso
- Spectral imaging microscopy
- Surface shape
ASJC Scopus subject areas
- Conservation
- Chemistry (miscellaneous)
- Archaeology
- Materials Science (miscellaneous)
- Archaeology
- Computer Science Applications
- Spectroscopy
