Combined multiphoton fluorescence microscopy and photoacoustic imaging for stratigraphic analysis of paintings

Non-Linear Microscopy: A Well-Established Technique for Biological Applications towards Serving as a Diagnostic Tool for in situ Cultural Heritage Studies

“…The high contrast complementarity provided by this bimodal approach has additionally been enhanced by post-processing analysis of the acquired MPEF signals using a novel algorithm, which is able to discriminate overlapping layers according to the non-linearity order and the optical parameters of the system. In addition, the combined images have been directly compared with cross-sectional bright field observations, validating the capabilities of the proposed diagnostic method in terms of measurement accuracy and imaging specificity [118].…”

“…A low intensity MPEF arose from the layer of dammar, while the painting layer emitted a higher intensity fluorescence signal, as shown in Figure 2. Analysis and discrimination of the recorded MPEF for the precise layer thickness detection was achieved through the use of an image processing algorithm in the MATLAB programming environment [118]. The thickness of the dammar varnish was 82 µm and the thickness of the red led paint layer was 98 µm.…”

Listening to laser light interactions with objects of art: a novel photoacoustic approach for diagnosis and monitoring of laser cleaning interventions

“…Nevertheless, several materials typically met in works of art are optically opaque to such a degree that they do not permit observations beyond a few μm in depth using exclusively optical radiation. To provide an augmented diagnostic approach offering multi-contrast information together with a high penetration capability in opaque media, a combination of PA imaging and NLM has been recently demonstrated [55], with emphasis given on the stratigraphic analysis of painted artworks. Figure 4.1a shows a cross-sectional MPEF image (excitation at 1028 nm) of a canvas painting mock-up, for a XZ region of 1 cm by 385 μm sampled with 200 by 80 pixels respectively.…”

“…Figure 4.2c corresponds to a MAP PA image of the pencil underdrawing, as a result of the selective absorption of infrared radiation (λ = 1064 nm) by the graphite deposition regions. The AC PA diagnostic approach was further compared with NIR imaging [55] and [56] ( Fig. 4.2d) within a similar optical spectral band (central wavelength: 1050 nm, FWHM: 25 nm).…”

Advances in non linear imaging microscopy for tissue and in-vivo biological samples characterization

“…Thus PM is preferable for the correct classification of the recorded non-linear tissue images. 4,8,16,16,32,32 kernels respectively at each layer. SM has one convolution layer less so the number of kernels are 4,8,16,16,32. Finally, CM has 6 convolutional layers, however the number of the kernels in the last convolutional layer is equal to 64 instead of 32 compared to the PM.…”