Les Wright of the YouTube channel Les’ Lab has figured out how to remove the Bayer filter from a Raspberry Pi camera. By doing so, Les expanded the sensitivity of the CCD image sensor for use in a Raspberry Pi-based spectrometer. A spectrometer is an instrument used to analyze the property of light as a function of its wavelength or frequency.
A Bayer array, or Bayer filter, is an array of many tiny color filters that cover an image sensor to allow it to render color information. Without this filter, an image sensor captures more wavelengths of light but cannot accurately render the color information people typically want from a digital camera.
Removing the Bayer filter is no small task. The image sensor has a lot of sensitive circuitry, so removing the filter through brute force damages the sensor. Les and others have also tried chemical solvents like brake fluid and paint stripper. These methods were ineffective. Les eventually leveraged his experience with lasers and used a nitrogen laser to burn off the Bayer filter.
Les built a rig that scans the laser across the sensor using stepper motors. Les describes the rig as something like a CNC machine. In the video below, you can see close-up footage of the process, which looks very cool and is an interesting look at an image sensor.
With the Bayer filter lasered off, Les plugged his improved camera into his homemade spectrometer and tested it outside. The spectrometer can now see further into infrared and ultraviolet wavelengths. It can even detect Fraunhofer lines, which are dips in the Sun’s spectrum due to the absorption of molecules in the atmosphere.
It’s a very cool DIY project, and the result is fascinating. If you like this sort of content, be sure to subscribe to Les’ Labs.