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A team of scientists at the National Research Council of Canada have released results of a 3D, color laser scan they did of Leonardo da Vinci’s famed painting, the Mona Lisa.rnrn
The laser scanner is mounted on a high-precision linear translation stage, which moves the scanner across the surface to acquire successive scan bands 4 cm in width.
The Canadian team built a portable version of the scanner specifically for this project and tested it on a few Renoir paintings before taking it to the Louvre in Paris. They also developed new algorithms for the project, in order to handle the Mona Lisa’s gradually changing shades of color.
The study is the first high-resolution, archival quality 3D digital model of the masterpiece, and it has given researchers critical clues into the background of the painting.
The researchers also looked into the painting’s state of preservation. With a depth resolution of one-hundredth of a millimeter, the scan was able to provide the most detailed analysis to date of the painting’s craquelure, or surface cracks. “What our results show, and this corroborates the other studies, is that the paint layer itself, despite all its craquelure, is very well bonded to the poplar substrate,” said researcher John Taylor. “We didn’t see any sign of paint lifting. So for a 500-year-old painting it’s very good news.”rnrn
The data was collected after the museum had closed on two October nights in 2004. The painting was returned to its environment-controlled chamber by the museum’s curator before doors opened to visitors in the morning. The data then took more than a year to analyze.
Pictured here is NRC scientist Marc Rioux with a 3D model of the painting using a multiresolution display system also developed at the NRC.rnrn
The scan revealed that the model, Lisa Gherardini, the wife of a Florentine merchant, was wearing a thin, nearly transparent veil when she sat for the painting. The veil was typically worn by women of the time who were pregnant or had recently given birth.
It is now believed that the painting was done to commemorate the birth of the woman’s second son, putting the date of origin around 1503.
This image of the painting shows where there is a convex warp in the poplar wood that’s about 12 millimeters higher than the outside of the painting.rnrn
Not only was the depth resolution sufficient to see differences in the height around cracks, it could also resolve differences in the thickness of the varnish and even beyond to reveal the master’s first conception of the Mona Lisa.
“The 3D imaging was able to detect the incised drawing to provide us with DaVinci’s general conception for the composition,” says Dr. Christian Lahanier, Head of the Documentation Department of the Centre de Recherche et de Restauration des Musees de France, which organized the study.
Amazingly, even at that resolution, scientists could find no brush strokes or fingerprints to help solve the mystery of how da Vinci managed to apply such thin layers of paint.
The scanning technology, camera and processing software have been licensed to nine Canadian companies. Among these, an Ottawa-based company has used the technology to create a 3D camera currently onboard the NASA space shuttle Atlantis. This camera serves to examine the changing state of the shuttle’s heat tiles during a voyage. Another licensee uses the technology for cutting-edge film animation, including work on the “Lord of the Rings” trilogy and the “Matrix” sequels.