Quality Evaluation of RGB Images Reconstructed by Means of Photoacoustic Signals

Recent researches have demonstrated the usefulness of photoacoustics in non-destructive control, in particular, in the monitoring and diagnosis of works of art. Indeed, it is fundamental to preserve the artworks’ integrity by using techniques not involving direct contact or damaging radiation, or pre-treatments. On the other hand, a lot of artistic heritage consists of paintings that are complex systems, where, often, the presence of highly scattering and semi-opaque materials make useless optical techniques. Consequently, in this context photoacoustics represent a powerful tool. This work is aimed to evaluate the quality of reconstructed RGB images of simple test objects examined by means of photoacoustic signals, in order to confirm the potentiality of this promising investigation method. Only a single-wavelength excitation source at 1064 nm was available and so, it has been necessary to perform some preliminary processings on the sample color images. The original images have been decomposed in R, G and B components; each of them has been converted into grayscale code, printed on transparency film and then investigated through photoacoustics. After that, the three generated photoacoustic images have been recombined to produce the reconstructed RGB image. A complete experimental system has been set to analyse dedicated test objects. The resulting images have been compared to the original ones, by using standard image quality parameters. Similar results are expected to be obtained by using three sources of distinct wavelengths (Red, Green, Blue), making the method easier to apply.