基于matlab实现干涉显微镜图像重构的相位质量优质度计算函数-　PhaseDerivativeVariance creates a phase quality map by　computing the variance of the partial derivatives of the　locally unwrapped phase. This is then used　to guide the phase unwrapping path. Uses only the 4 nearest　neighbours. The user may also input a binary mask.　 function derivative_variance = PhaseDerivativeVariance (IM_phase, varargin)　Created by BS Spottiswoode on 18/10/2004　Last modified on 06/12/2004　2010/07/19 Carey smith　Corrected a bug on the line before computing dy (dimx, :)