数字全息周期像的产生机理及在抑制零级衍射上的应用

The production mechanism of image periodicity in digital holography and its application in zero-order noise suppression

在数字全息成像中,利用CCD的RGB模式采样全息图时,全息重构像会出现特定的周期性分布.本文从理论和实验上详细研究了这种周期像产生的机理、分布特性和应用.研究结果显示,由于CCD的光谱滤镜会使全息图的RGB三个单色采样阵列出现部分像素信号的缺失,因此,需要通过特定的demosaicing数学算法对缺失的像素信号进行重建以形成完整的单色采样阵列,这是数字全息再现像周期分布产生的根源.而基于demosaicing算法的采样阵列重建会在全息图频谱中引入调制函数,导致物体再现像和零级衍射斑的周期分布差异.本文揭示了全息图的RGB采样、demosaicing算法与全息重构像周期性之间的内在关联.最后,讨论了结合空间移位和图像形态学技术,利用重构像的周期性抑制零级衍射斑的应用.所有理论与实验研究结果完全一致.

An interesting fact in digital holography is that the reconstruction process of the hologram recorded by the color camera may result in some periodic distribution of images in the image plane. In this paper we describe the production mechanism, characteristics and application of image periodicity in digital hologram reconstruction. Our study shows that the image distribution characteristics in the hologram reconstruction are strongly dependent on the option of RGB sampling mode due to a color filter array being used in the CCD camera, and the relevant demosaicing process of the sampling array reconstruction. The image and the dc noise from the hologram reconstruction may be of different distribution patterns due to the modulation function in the inverse Fourier transform of a full monochromatic sampling array （MSA） with demosaicing. Thus, this work reveals the potential relationship between the demosaicing algorithm for a full MSA reconstruction, the sampling frequency in the hologram recording, and the image periodicity in the hologram reconstruction. Finally the application of the image periodicity in zero-order noise suppression is discussed.