A new compact and rugged hyperspectral camera with broad spectral coverage and resolution for low-light applications in cultural heritage

Abstract

Hyperspectral imaging (HSI) is a novel non-invasive analytical technique based on spectroscopy. It measures the light spectrum from each point of a scene of interest. It generates an accurate digital record for documentation and archiving in art conservation. This information can be used for diagnostics by monitoring changes, degradation or damages to paintings, for supporting in artwork restoration, for artist s material identification and pigment mapping, as well as for discovering the history of a piece of art by e.g. revealing underdrawings and retouchings. HSI measures the continuous spectrum of the light as a function of the wavelength λ for each pixel of the scene at coordinates (x, y) with fine spectral resolution, thus building the so-called 3-dimensional hyperspectral image. This data cube contains an extensive amount of information. Therefore, many numerical methods and algorithms have been developed to enable the extraction of quantitative parameters related to the physicochemical properties of the imaged objects from congested scenes. Here we present HERA, a novel and compact hyperspectral camera by NIREOS. The device, based on the Fourier-transform approach, combines high delay precision, long-term stability, insensitivity to vibrations and broad spectral coverage. It can measure absolute reflectance and fluorescence with very high spectral accuracy and resolution (≈3-nm, comparable to best commercial push-room systems) in the visible and near-infrared. HERA does not require any scanning of the object under analysis. This feature makes it extremely flexible and applicable to the study of works of art of different nature and size. Potential applications range from the on-site study of museum paintings, to the assessment of the conservation status of large monuments and historic buildings, to the documentation of small objects using standard macro photography lenses. In this paper, we will present a series of application examples in the field of conservation science to demonstrate its versatility.