Proc. SPIE. 7156, 2008 International Conference on Optical Instruments and Technology: Optical Systems and Optoelectronic Instruments
KEYWORDS: Signal to noise ratio, Monochromatic aberrations, Optical transfer functions, Spatial frequencies, Image processing, Wavefronts, Computer simulations, Optoelectronics, Modulation transfer functions, Phase transfer function
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.