Multispectral imaging, or images using wavelengths other than people in ordinary seen mild, has many programs ranging from earth observation to forgery detection in art. For case in point, titanium white and guide white, two pigments utilised in unique historic eras, search equivalent in noticeable gentle but have distinctive signatures in the UV variety. Similarly, IR imaging can expose a painting’s interior levels if the pigments utilised are transparent to IR.
Equipment for this kind of a market use is naturally very pricey, so [Sean Billups] resolved to completely transform an older model smartphone into a handheld multispectral camera, which can assistance him assess functions of art without having breaking the lender. It utilizes the smartphone’s camera alongside one another with a filter wheel attachment that permits it to capture various spectral ranges. [Sean] chose to use a Google Pixel 3a, largely due to the fact it’s cheaply available, but also simply because it has a good graphic sensor and digicam program. Modifying the camera to permit IR and UV imaging turned out to be a little bit of a obstacle, however.
Image sensors are normally sensitive to IR and UV, so cameras normally incorporate a filter to block anything but obvious light-weight. To eliminate this filter from the Pixel’s digital camera [Sean] experienced to warmth the digital camera module to soften the adhesive, thoroughly get rid of the lens, then glue a piece of plastic to the filter and pull it out at the time the glue experienced set. Perfecting this system took a little bit of trial and mistake, but once he managed to influence a obvious separation concerning camera and filter it was basically a make a difference 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 diverse filters, which can enable a range of IR, UV and polarized-light imaging modes. In the video clip embedded beneath [Sean] shows how the IR reflectography method can help to reveal the underdrawing in an oil portray. The process is designed to be extendable, and [Sean] has currently been searching at including features like IR and UV LEDs, magnifying lenses and even additional sensors like spectrometers.
We have observed a handful of multispectral imaging projects in advance of this drone-mounted method was a contestant for the 2015 Hackaday Prize, whilst this venture contains an excellent primer on UV imaging.