There are a lot of reasons why one might want to have the sensor in their camera modified. We see it all the time for those who wish to shoot infrared or ultraviolet photography. There are even companies out there who will do the whole process for you. Usually, though, it doesn’t involve stripping off the Bayer filter array. Typically it’s just removing the filter that blocks UV and IR.
Well, for Les Wright at Les’ Lab, just removing the blocking filter on his Raspberry Pi camera wasn’t enough. he wanted all the raw data, without any colour interference at all from every pixel on the sensor. So, he went on a mission to figure out away to remove it without killing the sensor. Ultimately, the best method proved to be to burn it off with a laser!
It’s a pretty extreme mod. Probably one of the most extreme modifications I’ve ever seen on a camera sensor – especially when you consider what lasers typically do to camera sensors. And just three weeks ago, Sony issued a warning to not expose your lens to laser beams due to the damage it can cause to your sensor. Of course, sending a laser through your lens and having the absolute control that Les has in his experiment are two different things.
Les says he killed a lot of Raspberry Pi camera sensors trying to figure out the perfect technique to strip the Bayer sensor from the camera sensor. He tried all sorts of abrasive and chemical solvent-based solutions before finally giving it a go with his nitrogen laser. The problem was simply that the circuitry surrounding the sensor is just far too delicate and very easily damaged. And the slightest bit of damage kills the entire module.
Why would anybody want to do this? Well, not everybody uses cameras for their aesthetic abilities. For some, they’re scientific tools. And with the Bayer sensor removed from the sensor, it’s able to see light at wavelengths far beyond the visual spectrum, and even further than many IR and UV-converted cameras, letting him see specific chemicals and emissions present in the scene that would otherwise be undetectable.
To perform the laser surgery, Les built a rig that would allow him to essentially CNC control the movement of the laser over the sensor, along with a vision system using a Raspberry Pi with another PiCam (naturally!) that would let him align everything properly and monitor the progress in real-time. In total, it took about half an hour to perform the removal of the Bayer array, and it opens up a lot of options for both scientific and creative uses of the Pi camera.
I wonder if the Pi Foundation could be convinced to manufacture one that comes shipped without the Bayer filter array or an IR/UV blocker at all? I mean, they already make an infrared camera module, so it wouldn’t be too much of a stretch!