Multispectral imaging, or images making use of wavelengths other than those people in common visible mild, has many apps ranging from earth observation to forgery detection in artwork. For case in point, titanium white and lead white, two pigments used in various historic eras, glimpse equivalent in visible light-weight but have unique signatures in the UV assortment. Similarly, IR imaging can reveal a painting’s inner layers if the pigments made use of are transparent to IR.
Devices for this sort of a niche use is by natural means quite expensive, so [Sean Billups] decided to remodel an older model smartphone into a handheld multispectral digital camera, which can assistance him assess works of artwork without having breaking the bank. It employs the smartphone’s digital camera alongside one another with a filter wheel attachment that enables it to seize distinctive spectral ranges. [Sean] selected to use a Google Pixel 3a, mostly mainly because it is cheaply available, but also mainly because it has a fantastic graphic sensor and digicam computer software. Modifying the digicam to help IR and UV imaging turned out to be a bit of a challenge, on the other hand.
Image sensors are normally sensitive to IR and UV, so cameras usually include things like a filter to block anything but seen gentle. To clear away this filter from the Pixel’s digital camera [Sean] experienced to warmth the digicam module to soften the adhesive, cautiously take away the lens, then glue a piece of plastic to the filter and pull it out after the glue experienced established. Perfecting this system took a bit of trial and error, but after he managed to impact a apparent separation concerning camera and filter it was simply a subject of reattaching the lens, assembling the cellphone and mounting the filter wheel on its again.
The 3D-printed filter wheel has slots for four various filters, which can allow a range of IR, UV and polarized-light imaging modes. In the movie embedded underneath [Sean] demonstrates how the IR reflectography method can assist to expose the underdrawing in an oil portray. The program is made to be extendable, and [Sean] has presently been looking at adding capabilities like IR and UV LEDs, magnifying lenses and even additional sensors like spectrometers.
We’ve noticed a handful of multispectral imaging assignments ahead of this drone-mounted procedure was a contestant for the 2015 Hackaday Prize, whilst this project contains an outstanding primer on UV imaging.
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