About a moire-less condition for non-square grids

The moire-less condition is found for non-square grids. The exact solution is found in form of a quartic equation depending on the geometric parameter. The root gives the optimal angle for minimized moires. The approximate solution is also found as well as the upper limit for residual moires. The proximity of the two solutions is proven. Experiments confirm the theoretical findings. The results can be used for minimizing moires in display devices which include several layers of regular grids.