Multispectral imaging, or photography working with wavelengths other than these in normal visible gentle, has many apps ranging from earth observation to forgery detection in art. For illustration, titanium white and guide white, two pigments employed in unique historic eras, appear similar in obvious gentle but have distinctive signatures in the UV range. Likewise, IR imaging can reveal a painting’s internal layers if the pigments made use of are transparent to IR.
Products for this sort of a specialized niche use is obviously really expensive, so [Sean Billups] decided to completely transform an more mature design smartphone into a handheld multispectral digicam, which can aid him examine functions of art with no breaking the bank. It uses the smartphone’s camera collectively with a filter wheel attachment that permits it to seize unique spectral ranges. [Sean] chose to use a Google Pixel 3a, largely mainly because it’s cheaply out there, but also due to the fact it has a good impression sensor and digicam software package. Modifying the digital camera to enable IR and UV imaging turned out to be a bit of a challenge, having said that.
Picture sensors are by natural means delicate to IR and UV, so cameras typically contain a filter to block just about anything but seen light-weight. To take away this filter from the Pixel’s digital camera [Sean] had to heat the camera module to soften the adhesive, very carefully remove the lens, then glue a piece of plastic to the filter and pull it out as soon as the glue had established. Perfecting this procedure took a bit of demo and error, but once he managed to result a obvious separation in between camera and filter it was simply just a subject of reattaching the lens, assembling the cellphone and mounting the filter wheel on its back.
The 3D-printed filter wheel has slots for four diverse filters, which can allow a selection of IR, UV and polarized-light-weight imaging modes. In the movie embedded below [Sean] exhibits how the IR reflectography manner can assist to reveal the underdrawing in an oil portray. The process is designed to be extendable, and [Sean] has already been seeking at adding functions like IR and UV LEDs, magnifying lenses and even additional sensors like spectrometers.
We have viewed a handful of multispectral imaging assignments prior to this drone-mounted program was a contestant for the 2015 Hackaday Prize, even though this job contains an superb primer on UV imaging.