UV and IR light can, literally and figuratively, show us the world in a totally different light. One of their common uses is to examine painting for authenticity or damage inspection. Sean Billups made his own tool for inspecting paintings, and it’s actually relatively simple. Using an old Google Pixel 3a phone, a simple 3D-printed part, and lots of patience, he created a multispectral phone camera. By simply turning a small wheel, it reveals the secrets of any painting. And with some patience, you can also do it yourself.
To make this multispectral camera, Sean needed to remove the IR filter first. It’s something you can also do with your camera to convert it to IR, but watch this before you do. Sean says that removing the IR filter took a lot of trial and error before he figured out how to do it successfully.
“For the Pixel 3a camera, I tried using a scalpel to separate the sensor from the lens housing,” he writes, “but this ended up breaking some very tiny solder joins that connected to the autofocus mechanism in the lens housing.” Everything would have been okay if there weren’t for the autofocus, Sean explains, but alas. He then tried soldering those broken joins, but with no success. They were too tiny and as Sean puts it, beyond his soldering skills. Another try involved using a heated 3D printer bed to soften the adhesive around the lens. Sean left the phone lying there for 15 minutes on 60C and then used a small pair of pliers to twist and remove the lens. “This gave me access to the IR filter, which is glued into a square frame just above the sensor,” Sean writes. So far so good. He glued a small section of ABS 3D printer filament to the filter to pull it out – but it ended up breaking. However, Sean managed to salvage the whole thing. “After carefully removing the rest of the broken IR filter, I was able to twist the lens back in place and put the camera module back into the phone without an issue.” Here’s the process he used in case you decide to try it out yourself: When the Pixel’s camera was modified, Sean 3D-printed the filter wheel that attaches to the phone camera. It was designed to house four filters, which enable up to seven types of technical imaging when combined: visible light, raking light, UV fluorescence, UV reflectography, IR reflectography, IR fluorescence, and polarized. To remove the filter, I have been using a small amount of adhesive (superglue or a quick-setting epoxy) on the end of a small section of 3d printer filament. I glue this piece onto the filter itself, allow it to cure, then set the camera back on the printer bed and pull the filter out.” This DIY project even brought Sean the Hack a Day Prize 2022. He posted a video which demonstrates how the camera works, revealing some details beneath the visible coat of an oil painting.
There’s so much to reveal, even if it’s just the paint. “For example, titanium white and lead white, two pigments used in different historical eras, look identical in visible light,” Hack a Day writes, “but have distinct signatures in the UV range.” Similarly, when observing the painting in IR, you can reveal painting’s inner layers if the pigments used are transparent to IR. This reveals if there was a sketch, or even an entire different painting, under the work of art you observe. It also can reveal repairs and tell you more about the materials and the era when they were made. When you think about it, doing all of that with just a smartphone camera and a simple 3D-printed piece is incredible. Sean says that the system is designed to be extendable, and he’s already exploring what else he could add to improve it further. [via Hack a Day]
