For centuries, the Mona Lisa has beguiled art buffs unable to resist speculating on its origins and meaning. Now a French inventor claims to have some answers, including the fate of the enigmatic subject's famously missing eyebrows and lashes.

Parisian engineer Pascal Cotte says his ultra-detailed digital scans of the painting allow him to effectively burrow through layers of paint to "see" into the past of Leonardo Da Vinci's 16th-century portrait of a Florentine merchant's wife.

Parisian engineer Pascal Cotte made scans of the Mona Lisa, seen here on display at the Louvre, three years ago.
(Associated Press)

The world's most famous painting originally included both brows and lashes, according to Cotte, who says his 240-megapixel scans of the painting reveal traces of Mona Lisa's left brow, obliterated by long-ago restoration efforts.

"With just one photo you go deeper into the construction of the painting and understand that Leonardo was a genius," Cotte said in San Francisco, at the U.S. debut of an exhibit detailing his findings.

As a boy growing up in Paris in the 1960s, Cotte said, he spent hours staring at the Mona Lisa the first time he saw it at the Louvre. He later used his scientific training in light and optics to develop a camera that would let him examine the object of his obsession.

Cotte, 49, estimates he has spent 3,000 hours analyzing the data from the scans he made of the painting in the Louvre's laboratory three years ago.

Using sensors to detect light from both the visible spectrum and the infrared and ultraviolet ranges invisible to the human eye, Cotte said, his camera allowed him to make these and other findings:

• Da Vinci changed his mind about the position of two fingers on the subject's left hand.
• Her face was originally wider and the smile more expressive than Da Vinci ultimately painted them.
• She holds a blanket that has all but faded from view today.

Cotte said his analyses also revealed what he believes are the painting's colours as they looked on Da Vinci's easel.

Age, varnish and restorations performed by later conservators' hands have resulted in a painting that, in its permanent home behind bulletproof glass at the Louvre, appears saturated with heavy greens, yellows and browns.

Working with his 22-gigabyte digital photo, made using 13 different colour filters rather than the typical three or four found in consumer-grade digital cameras, Cotte created a reproduction of the Mona Lisa with the light blues and brilliant whites he thinks represent the painting in its original form.

"For the next generation, we guarantee that forever you will have the true colour of this painting," Cotte said.

Though some art historians have expressed skepticism about Cotte's findings, he hopes his technique can be used as a guide for future restoration work on not just the Mona Lisa, but also on aging art treasures around the world.

Since scanning the Mona Lisa, Cotte has made super-high-resolution photographs of more than 500 paintings, including works by Van Gogh, Brueghel, Courbet and other European masters.

"To communicate our cultural heritage to our kids, we need to provide the maximum of information," Cotte said.