“With Paintings Uncovered, users are able to point an infrared flashlight at a digital version of the painting (either a projection or pulled up on a computer screen), and an infrared camera tracks the position of the light to create a circular mask on the painting that "burns through" the top layer. Moving the flashlight onto certain areas then triggers specific questions about the work.”

(Bonus art history knowledge in the 2nd alt text)

https://www.metmuseum.org/perspectives/paintings-uncovered