Fourier Transform Hyperspectral Imaging for Cultural Heritage [chapter]

Massimo Zucco, Marco Pisani, Tiziana Cavaleri
2017 Fourier Transforms - High-tech Application and Current Trends  
Hyperspectral imaging is a technique of analysis that associates to each pixel of the image the spectral content of the radiation coming from the scene. This content can be helpful to recognize the chemical nature of the materials within the scene or to calculate their colours under particular conditions. Different solutions of hyperspectral imager have been realized with different spatial resolution, spectral resolution and range in the electromagnetic spectrum. In particular, improving the
more » ... ctral resolution allows discriminating smaller features in the spectrum and the unambiguous detection of the absorption bands characteristic of superficial materials. Hyperspectral imagers based on interferometers have the advantage of having a spectral resolution that can be varied according to the needs by changing the optical path delay of the interferometer. A spectrum for each pixel is obtained with an algorithm based on the Fourier transform of the calibrated interferogram. We present the results of the application of a hyperspectral imager based on Fabry-Perot interferometers to the field of cultural heritage. On different artworks, the hyperspectral imager has been used for pigment recognition, for colour rendering elaborations of the image with different light sources or standard illuminants and for calculating the chromatic coordinates useful for specific purposes. Fabry-Perot hyperspectral imager Our hyperspectral imager (HSI) is based on a Fabry-Perot interferometer (FPI), the optical system is represented in Figure 1 where the scene is firstly imaged in the FPI so that the transmitted intensity is modulated by the interference, and the second image is then formed on the camera sensor by means of the relay lens. A sequence of frames carrying the interference fringe information is acquired synchronized with the scan of the optical path delay (OPD) between the mirrors of the FPI, from contact to the maximal distance of the mirror. For each pixel of the image, the interferogram is extracted from Fourier Transforms -High-tech Application and Current Trends 216 Fourier Transform Hyperspectral Imaging for Cultural Heritage 217 Fourier Transform Hyperspectral Imaging for Cultural Heritage 227
doi:10.5772/66107 fatcat:tuhic5dsgza7dc4tkkp5u5fiwm