The system was tested at 4 different spatial frequencies over the range of the system.
Below is a comparison of the combined images for the highest and lowest spatial frequency the system provides.
Note that at the higher spatial frequency, the deeper sheet is much less visible than at the lower spatial frequency.
Clearly, the images require more light, which for our system means longer exposure times. Also, the phase shifts were not exactly 120 degrees, as evidenced by the the lines in the combined images.
Mean Squared Error Analysis
The depth of modulation was measured using mean squared error for one set of phase shifted images. MSE was evaluated at each pixel and plotted as a surface map.