A new kind of phase mask and its properties using in wavefront coding systems

摘要

The phase mask plays a key role in wavefront coding systems. In order to find the phase coding device with better performance ,a new kind of phase mask - five times phase mask is proposed, based on cubic phase mask in common use, and its coding properties are studied in the paper. First of all, the reason of depressing spherical aberration is analyzed by deriving the asymptotic solution to OTF of the wavefront coding systems with five times phase mask. And then we compare the effects of inhibition of spherical aberration when place the cubic and five times phase mask respectively. Finally, the experimental simulation is done. The results show that on the specific threshold (MTF=0.1) the normalized bandwidth of the system with five times phase mask can be reached 3 times of that with the cubic one; at the same characteristic frequency (u = 0.5), the MTF value is 2 times of that in system with cubic one. Both the MTF consistency in the low frequency region and the PTF consistency in the high frequency region of the system with a five times phase mask are better than those with a cubic one in condition of different spherical aberration. Compared with the cubic phase mask, the five times phase mask performs better in inhibition of spherical aberration.