波前编码系统中相位掩膜板的新设计

New design of cubic-phase-modulation phase masks in wavefront coded imaging system

波前编码技术能扩大非相干光学成像系统的景深。根据传统相位掩膜板的设计原理,从两个方面对原有的相位掩膜板表达式进行扩展。由此提出了两种新的设计方案:“多项式”方案和“高次方”方案。前者是在原有的公式中加入了x平方项,而后者是将原有的高次方指数拓展到小数形式。将这两种新系统进行模拟计算,得到了相关的调制传递函数(MTF)数据和三维图,结果显示MTF随离焦量变化很小(当u=1时,均方差分别为0.0027和0.0021),而且不会出现零值,跟传统方案MTF差值分别在0.05和0.04以内。由此说明新方案也能实现扩大光学系统景深的目的。

The scene depth of a incoherent optical imaging system can be extended by wavefront coding technique. The original expression for phase mask plate can be extended according to the design principle of traditional phase mask plate, Then two design schemes, i.e., polynomial design and high-order design, are proposed： The former is to add square term of x in the original formula and the latter is to extend the power of x to real number field. The MTFs and 3D figures of these two new systems are simulated and discussed. The results show that MTFs are insensitive to the off-focus （when u=1, mean-square-deviation is 0.0027 and 0.0021, respectively） and never to be zero. Compared with the traditional scheme, the MTF differences of two new designs are less than 0.05 and 0.04, respectively. According to the discussion above, both designs are effective to expand the depth of field of an optical system.