Central to our approach is the way in which current knowledge from the technical art history community will be combined with our uniquely tunable coherent infrared light sources to inform the design of our investigations. While hyper-spectral imaging of artwork is not new, we seek to demonstrate a “smart” approach using computational compressive sensing where the spectroscopy of pigments featuring in materials and cultural heritage will be used to optimize a basis set of broadband illumination spectra that probe in exactly the right spectral bands to provide maximum discrimination.
Full-field Ultra-broadband Spectral Compressive Imaging
The first of our investigative approaches is full-field, ultra-broadband spectral compressive imaging.
In this method, structured spectral illumination is combined with near-/mid-infrared cameras to provide efficient mapping of pigments in an object. The spectroscopy of pigments found in materials and cultural heritage will be used to construct an optimized basis set of broadband illumination spectra that probe the reflectance of an object to provide maximum discrimination between different pigments. Contemporary reconstructions with known pigment and media distributions will allow us to evaluate and refine this technique.
Adopting suitable basis spectra offers the potential for data reduction of the order of ×100. Given the time, storage and processing burden associated with point-by-point FTIR or wavelength-scanning methods, our proposed method permits a route to high-speed pigment-sensitive imaging.
Infrared Stratigraphic Imaging
The second of our investigative approaches is mid-infrared optical coherence tomography.
In this approach, sensitive and high-resolution VIPA spectroscopy is extended to the mid-IR fingerprint band. By doing so, our approach provides not only the stratigraphy of a painting, but also depth-localized spectroscopy for chemical depth mapping.
Developing these methods to reveal the chemically-specific stratigraphy of an object will be enabled by the provision of ground-truth samples with known structural and chemical properties.