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Multispectral imaging, or images applying wavelengths other than individuals in ordinary visible light-weight, has a variety of applications ranging from earth observation to forgery detection in artwork. For case in point, titanium white and direct white, two pigments used in distinct historical eras, glimpse similar in seen gentle but have distinctive signatures in the UV assortment. In the same way, IR imaging can expose a painting’s internal layers if the pigments used are transparent to IR.
Machines for such a market use is by natural means rather pricey, so [Sean Billups] determined to completely transform an older design smartphone into a handheld multispectral digicam, which can aid him analyze operates of artwork without breaking the bank. It makes use of the smartphone’s digicam with each other with a filter wheel attachment that permits it to capture distinctive spectral ranges. [Sean] selected to use a Google Pixel 3a, mostly for the reason that it’s cheaply readily available, but also simply because it has a excellent impression sensor and digicam application. Modifying the digital camera to permit IR and UV imaging turned out to be a bit of a obstacle, even so.
Picture sensors are normally sensitive to IR and UV, so cameras normally consist of a filter to block anything but visible light-weight. To remove this filter from the Pixel’s camera [Sean] had to heat the digital camera module to soften the adhesive, meticulously clear away the lens, then glue a piece of plastic to the filter and pull it out once the glue had established. Perfecting this process took a little bit of trial and error, but at the time he managed to effect a distinct separation involving camera and filter it was basically a make any difference of reattaching the lens, assembling the cell phone and mounting the filter wheel on its back again.
The 3D-printed filter wheel has slots for 4 diverse filters, which can allow a wide variety of IR, UV and polarized-gentle imaging modes. In the video clip embedded beneath [Sean] demonstrates how the IR reflectography manner can assist to reveal the underdrawing in an oil painting. The program is built to be extendable, and [Sean] has previously been on the lookout at including features like IR and UV LEDs, magnifying lenses and even extra sensors like spectrometers.
We’ve witnessed a handful of multispectral imaging initiatives ahead of this drone-mounted process was a contestant for the 2015 Hackaday Prize, when this undertaking consists of an superb primer on UV imaging.
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