基于双色光照明的单曝光同轴数字全息技术

Double Wavelength One-Shot In-Line Digital Holography

提出了一种基于双色光照明的单曝光同轴数字全息技术。在红绿蓝三色中,任选两种波长的光来照射物体,采用彩色CCD记录双色同轴全息图,然后经过三基色分离数字处理,可得到两幅不同波长的同轴全息图。用角谱衍射理论对该技术进行了分析,表明在降低物参光振幅比的条件下,通过对同轴数字全息图求自然对数,可近似得到衍射物光及其共轭之和,其误差与物参光振幅比有关。取两幅不同波长的同轴数字全息图,经自然对数处理后,用传递函数可以很好地重构出物体图像,给出了具体的数字处理算法。用仿真实验,模拟了该技术的全息记录和处理过程,得到重构图像的峰值信噪比(PSNR)为14.2 dB。结果表明该方法可以去除孪生衍射像干扰,可以实现清晰的单曝光同轴全息成像。最后,分析了再现像中噪声产生的原因。该技术可用于基于同轴全息的实时成像与动态测量。

A novel technique of one-shot in-line digital holography based on double wavelength illumination was proposed. Two wavelength beams in color of red,green or blue （RGB） are simultaneously used to illuminate the object and produce the in-line digital hologram （DH）. After recording the hologram by a color CCD,two in-line DHs recorded with different wavelengths can be obtained by separating the color image into RGB channels. The angular spectrum theory of diffraction was applied in the analysis of the proposed technique. On weakening the object wave in comparison to the reference wave,the summation of the diffraction object wave and its conjugation can be approximately obtained by logarithmizing the in-line DH. The approximating error lies on the object and reference wave ratio. Then the object image can be reconstructed from the two in-line DHs of different wavelengths by applying the transfer function. The reconstruction method was presented. Computer simulations and simple experiment were given to demonstrate the technique. The peak signal noise ratio （PSNR） of the reconstructed image is about 14.2 dB. Which shows this method could erase the interference of twin diffraction image. Finally,the noise sources of the reconstructed images were simply analyzed. This technique can be used for real time imaging and dynamic measuring based in-line digital holography.