Multispectral imaging, or photography applying wavelengths other than those in ordinary obvious light-weight, has a variety of applications ranging from earth observation to forgery detection in art. For illustration, titanium white and direct white, two pigments made use of in distinctive historical eras, seem similar in visible light-weight but have distinctive signatures in the UV range. Similarly, IR imaging can reveal a painting’s interior levels if the pigments made use of are transparent to IR.

Gear for this sort of a area of interest use is by natural means rather pricey, so [Sean Billups] resolved to transform an older design smartphone into a handheld multispectral digicam, which can support him review will work of art without breaking the lender. It uses the smartphone’s camera collectively with a filter wheel attachment that enables it to capture various spectral ranges. [Sean] selected to use a Google Pixel 3a, mostly mainly because it is cheaply offered, but also due to the fact it has a good picture sensor and digicam software package. Modifying the camera to empower IR and UV imaging turned out to be a little bit of a obstacle, on the other hand.

Picture sensors are the natural way delicate to IR and UV, so cameras typically include a filter to block just about anything but obvious light. To take away this filter from the Pixel’s digital camera [Sean] had to heat the digital camera module to soften the adhesive, carefully take away the lens, then glue a piece of plastic to the filter and pull it out once the glue had established. Perfecting this system took a little bit of trial and mistake, but at the time he managed to outcome a obvious separation involving digital camera and filter it was basically a make a difference of reattaching the lens, assembling the phone and mounting the filter wheel on its back.

The 3D-printed filter wheel has slots for four distinctive filters, which can help a wide variety of IR, UV and polarized-gentle imaging modes. In the video clip embedded below [Sean] shows how the IR reflectography manner can assistance to expose the underdrawing in an oil painting. The procedure is designed to be extendable, and [Sean] has previously been looking at incorporating functions like IR and UV LEDs, magnifying lenses and even further sensors like spectrometers.

We have observed a handful of multispectral imaging assignments prior to this drone-mounted program was a contestant for the 2015 Hackaday Prize, while this venture contains an superb primer on UV imaging.

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