一种无透镜傅里叶变换数字全息的散斑降噪方法

A Speckle Noise Reduction Method for Lensless Fourier Transform Digital Holography

散斑噪声的存在严重降低了数字全息技术再现像的信噪比和空间分辨率。在无透镜傅里叶变换数字全息中,通过对电荷耦合器件(CCD)记录的干涉图进行一次傅里叶变换,就可以重建物光场。根据干涉图上不同的像素点对再现像中散斑噪声强度分布贡献不同的特点,提出了一种新的降噪方法。该方法将CCD输出的干涉图划分为多个区域,并调换各个区域的位置,得到多幅互异的新干涉图,然后将所有新干涉图进行再现处理;对再现像进行叠加平均,就可以得到一幅散斑噪声强度更低的再现像,其等效视数明显提高。相比于空域掩模法,所提方法的处理时间缩短了80%左右,且再现像的边缘保持系数提高了1倍。

The presence of the speckle noise greatly reduces the signal-to-noise ratio and spatial resolution of the digital holographic reconstructed image. In the lensless Fourier transform digital holography, the object light field can be reconstructed by only one step of Fourier transform on the interferogram recorded by the charge coupled device （CCD）. A new speckle reduction method is proposed based on the principle that each pixel in the hologram contributes differently to the distribution of the speckle noise intensity in the reconstructed image in this paper. With this method, we divide the interferogram outputted by the CCD into several regions and exchange the positions of the regions. Many different new reconstruction interferograms are obtained, and then all new interferograms are reconstructed. Then, the reconstructed image with lower speckle noise intensity can be obtained by superimposing and averaging all of the reconstructed images, and the equivalent number of looks improves significantly. Compared with the spatial domain mask method, the proposed method reduces the processing time by 80%, and increases the edge preservation index of the reconstructed image by one times.