针对数字全息再现像存在的散斑噪声干扰严重、对比度低等问题，提出了基于散斑去噪各向异性扩散(SRAD)模型及非下采样Contourlet变换(NSCT)的数字全息再现像像质改善方法。采用SRAD模型消除再现像中的散斑噪声，然后进行NSCT分解，产生一个低频子带和若干高频子带。基于非线性增益函数和图像分割方法调整低频子带系数，并利用改进的NSCT模极大值法对高频子带进行边缘增强。大量实验结果表明，与近年来提出的非线性扩散去噪方法及NSCT增强方法相比，所提出的方法能更有效地消除散斑噪声、提升再现像的对比度，并得到光滑清晰的边缘，从而提高后续数字全息识别与测量的准确度。

Reconstructed image of digital holography has problems such as serious interference of speckle noise, low contrast and so on. Thus a method based on speckle reducing anisotropic diffusion (SRAD) model and nonsubsampled contourlet transform (NSCT) is proposed for improving reconstructed image quality of digital hologram. SRAD model is adopted to eliminate speckle noise of reconstructed image. After NSCT decomposition, a low-frequency sub-band and several high-frequency sub-bands are produced. Low-frequency sub-band coefficients are adjusted based on a nonlinear gain function and an image segmentation method. In high-frequency sub-bands, edges are enhanced using a NSCT modulus maximum edge detection method. A large number of experimental results show that, compared with nonlinear diffusion denoising methods and NSCT enhancement methods proposed recently, the proposed method can more effectively eliminate speckle noise and improve the contrast of reconstructed image. Furthermore, the edges are smooth and clear. As a result, the accuracy of recognition and measurement in digital holography can be improved.