I’ve just updated the openSFDI control software (available here) to address some problems that could cause stripes in the demodulated images.
The issue was that the FLIR camera recommended on this site has automatic gain control and gamma correction enabled by default. The gain control can cause some of the images to be brighter than others which can lead to poor demodulation. The Gamma correction is a little more pernicious because it’s nonlinear, so can add harmonics to the projected sinewaves. Harmonics inevitably lead to stripes in the demodulated images. I didn’t realize these adjustments were applied until I dug through the camera settings menu.
Even if you aren’t using the FLIR camera, make sure you turn any auto exposure or gain settings off, and switch off gamma correction.