Multispectral imaging, or pictures working with wavelengths other than all those in everyday seen light, has many programs ranging from earth observation to forgery detection in art. For case in point, titanium white and guide white, two pigments employed in different historic eras, glance similar in seen gentle but have distinctive signatures in the UV array. Similarly, IR imaging can expose a painting’s internal levels if the pigments employed are clear to IR.
Equipment for such a niche use is in a natural way quite dear, so [Sean Billups] resolved to change an more mature product smartphone into a handheld multispectral digital camera, which can aid him evaluate operates of artwork without having breaking the lender. It employs the smartphone’s camera together with a filter wheel attachment that permits it to seize diverse spectral ranges. [Sean] selected to use a Google Pixel 3a, largely simply because it’s cheaply available, but also since it has a fantastic image sensor and digital camera computer software. Modifying the camera to allow IR and UV imaging turned out to be a little bit of a challenge, nonetheless.
Picture sensors are naturally sensitive to IR and UV, so cameras normally include things like a filter to block something but visible gentle. To take away this filter from the Pixel’s camera [Sean] had to heat the camera module to soften the adhesive, very carefully eliminate the lens, then glue a piece of plastic to the filter and pull it out as soon as the glue had set. Perfecting this course of action took a little bit of demo and error, but at the time he managed to outcome a distinct separation among digicam and filter it was only a subject of reattaching the lens, assembling the mobile phone and mounting the filter wheel on its back again.
The 3D-printed filter wheel has slots for 4 distinctive filters, which can help a wide variety of IR, UV and polarized-light imaging modes. In the video embedded below [Sean] displays how the IR reflectography mode can assist to expose the underdrawing in an oil portray. The technique is created to be extendable, and [Sean] has by now been wanting at including features like IR and UV LEDs, magnifying lenses and even added sensors like spectrometers.
We’ve observed a handful of multispectral imaging projects prior to this drone-mounted process was a contestant for the 2015 Hackaday Prize, although this undertaking incorporates an exceptional primer on UV imaging.