R. Obana, Y. Takahashi and S. Komatsu: Off-axis imaging characteristics of optimized freeform phase mask for wavefront coding, Technical Digest, MOC'08 (Brussels, Belgium, 2008), 125-126.

We examine the off-axis imaging characteristics of the optimized freeform phase mask (FPM) that was already confirmed to extend the on-axis depth of focus much larger than the conventional cubic phase mask (CPM.). Computer simulation results show that the FPM reveals better performance than the CPM also in the off-axis field.