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针对无透镜傅里叶变换全息图数值再现过程的特点 ,提出了一套不同于以往的削弱或消除全息图 0级衍射和孪生像的数字图像处理算法。该算法分为三步。首先 ,对所拍摄的数字全息图通过高通滤波实现衬比度增强预处理 ,以提高全息图的衍射效率并消除再现图像的 0级衍射斑 ;其次 ,对再现图像进行带通及V型滤波 ,以降低背景噪声并使再现视场均匀 ;最后 ,对所得到的再现像进行平滑处理 ,通过小波滤噪和中值滤波进一步提高再现像的信噪比。实验结果表明 ,该方法只需记录一幅数字全息图 ,通过简单的数字图像处理 ,便可明显改善图像质量 ,尤其适用于无透镜傅里叶变换全息图的数值再现 ,并且更加实用化。
Aiming at the characteristics of lensless Fourier transform holographic image reconstruction, a set of digital image processing algorithms which is different from the previous one is to reduce or eliminate hologram zero order diffraction and twin images. The algorithm is divided into three steps. Firstly, the digital hologram is filtrated by high-pass filtering to enhance the contrast enhancement, so as to improve the diffraction efficiency of the hologram and eliminate the 0th-order diffraction spot of the reconstructed image. Secondly, the reproduced image is band-pass and V- So as to reduce the background noise and make the reproduced field of view uniform. Finally, the obtained reconstructed image is smoothed, and the signal-to-noise ratio of the reproduced image is further improved by using wavelet filtering and median filtering. The experimental results show that this method only needs to record a digital hologram, which can obviously improve the image quality through simple digital image processing. It is especially suitable for numerical reproduction of lensless Fourier transform holograms and is more practical.