Cheremkhin P A, Kurbatova E A
National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, 115409, Russia.
Sci Rep. 2019 May 17;9(1):7561. doi: 10.1038/s41598-019-44119-0.
Compression of digital holograms allows one to store, transmit, and reconstruct large sets of holographic data. There are many digital image compression methods, and usually wavelets are used for this task. However, many significant specialties exist for compression of digital holograms. As a result, it is preferential to use a set of methods that includes filtering, scalar and vector quantization, wavelet processing, etc. These methods in conjunction allow one to achieve an acceptable quality of reconstructed images and significant compression ratios. In this paper, wavelet compression of amplitude/phase and real/imaginary parts of the Fourier spectrum of filtered off-axis digital holograms is compared. The combination of frequency filtering, compression of the obtained spectral components, and extra compression of the wavelet decomposition coefficients by threshold processing and quantization is analyzed. Computer-generated and experimentally recorded digital holograms are compressed. The quality of the obtained reconstructed images is estimated. The results demonstrate the possibility of compression ratios of 380 using real/imaginary parts. Amplitude/phase compression allows ratios that are a factor of 2-4 lower for obtaining similar quality of reconstructed objects.
数字全息图的压缩使得人们能够存储、传输和重建大量全息数据。有许多数字图像压缩方法，通常使用小波来完成这项任务。然而，数字全息图的压缩存在许多显著特点。因此，优先使用包括滤波、标量和矢量量化、小波处理等在内的一组方法。这些方法结合起来可以使重建图像达到可接受的质量并实现显著的压缩比。本文比较了滤波离轴数字全息图的傅里叶频谱的幅度/相位和实/虚部的小波压缩。分析了频率滤波、所得频谱分量的压缩以及通过阈值处理和量化对小波分解系数进行额外压缩的组合。对计算机生成和实验记录的数字全息图进行了压缩。评估了所得重建图像的质量。结果表明，使用实/虚部时压缩比可达380。对于获得类似质量的重建物体，幅度/相位压缩的比率要低2至4倍。
