Yafei Xing

Vector lifting scheme for phase-shifting holographic data compression

Abstract. With the increasing interest in holography in three-dimensional imaging applications, the use of hologram compression techniques is mandatory for storage and transmission purposes. The state-of-the-art approach aims at encoding separately each interference pattern by resorting to common still-image compression techniques. Contrary to such an independent scheme, a joint hologram coding scheme is investigated in this paper. More precisely, instead of encoding all the interference patterns, it is proposed that only two sets of data be compressed by taking into account the redundancies existing among them. The resulting data are encoded by applying a joint multiscale decomposition based on the vector lifting concept. Experimental results show the benefits that can be drawn from the proposed hologram compression approach.

Adaptive nonseparable vector lifting scheme for digital holographic data compression

Holographic data play a crucial role in recent three-dimensional imaging as well as microscopic applications. As a result, huge amounts of storage capacity will be involved for this kind of data. Therefore, it becomes necessary to develop efficient hologram compression schemes for storage and transmission purposes. In this paper, we focus on the shifted distance information, obtained by the phase-shifting algorithm, where two sets of difference data need to be encoded. More precisely, a nonseparable vector lifting scheme is investigated in order to exploit the two-dimensional characteristics of the holographic contents. Simulations performed on different digital holograms have shown the effectiveness of the proposed method in terms of bitrate saving and quality of object reconstruction.

Compression of computer generated phase-shifting hologram sequence using AVC and HEVC

With the capability of achieving twice the compression ratio of Advanced Video Coding (AVC) with similar reconstruction quality, High Efficiency Video Coding (HEVC) is expected to become the newleading technique of video coding. In order to reduce the storage and transmission burden of digital holograms, in this paper we propose to use HEVC for compressing the phase-shifting digital hologram sequences (PSDHS). By simulating phase-shifting digital holography (PSDH) interferometry, interference patterns between illuminated three dimensional( 3D) virtual objects and the stepwise phase changed reference wave are generated as digital holograms. The hologram sequences are obtained by the movement of the virtual objects and compressed by AVC and HEVC. The experimental results show that AVC and HEVC are efficient to compress PSDHS, with HEVC giving better performance. Good compression rate and reconstruction quality can be obtained with bitrate above 15000kbps.

Comparative study of scalar and vector quantization on different phase-shifting digital holographic data representations

For compression of digital holographic data, choosing an appropriate representation of the holographic information is always a main target. The effectiveness of the representation needs to be studied before applying further compression method for reducing storage and transmission burden. In this paper, we investigate the effectiveness of using amplitude-phase information of the complex object wave and the difference information between different phase-shifted holograms by scalar and vector quantization. The experiments show that the amplitude-phase representation is more suited when applying intra compression, whereas holograms are more suited for inter compression.

Compression of digital holographic data: an overview

Holography has the potential to become the ultimate 3D experience. Nevertheless, in order to achieve practical working systems, major scientific and technological challenges have to be tackled. In particular, as digital holographic data represents a huge amount of information, the development of efficient compression techniques is a key component. This problem has gained significant attention by the research community during the last 10 years. Given that holograms have very different signal properties when compared to natural images and video sequences, existing compression techniques (e.g. JPEG or MPEG) remain suboptimal, calling for innovative compression solutions. In this paper, we will review and analyze past and on-going work for the compression of digital holographic data.

Vector quantization for computer generated phase-shifting holograms

Concerning the reconstruction quality, phase-shifting scheme has been proved to be efficient for digital holography. As a benefit from three differently phased reference waves, the reconstructed object image does no longer suffer from the zero-order image or twin image. In order to reduce the obvious storage and transmission burden brought in by extra holograms, in this paper, vector quantization (VQ) based on LGB algorithm (LBG-VQ) for computer generated phase-shifting holograms (CGPSHs) is proposed. The interference patterns at the hologram plane is generated by Fresnel transformation in phase-shifting digital holography (PSDH) scheme. Meanwhile, the performance of adaptive scalar quantization using Lloyd Max algorithm on effective holographic information is also investigated. Simulation results indicate that LBG-VQ outperforms adaptive scalar Lloyd Max quantization.

Sparse based adaptive non separable vector lifting scheme for holograms compression

Digital holography offers appealing features for microscopic and 3D imaging applications. Thus, the growing interest of digital holographic data has led to the constitution of huge amounts of data. Therefore, in order to efficiently store and transmit this data, the design of hologram compression schemes becomes a crucial issue. In this paper, we propose to encode two sets of data, referred to as shifted distance information, by applying a non separable vector lifting scheme. The idea consists in exploiting the redundancies existing between the two sets and building a content-adaptive hologram compression scheme by resorting to a sparse optimization technique. Experimental results show that the proposed method outperforms the state-of-the-art ones.

Chapter 3 – Basic Compression Tools

In this chapter, we first briefly introduce basic compression tools. Generally, compression techniques are classified into two categories: lossy and lossless techniques. A typical image compression scheme incorporates three fundamentals steps: transformation, quantization, and entropy coding. Indeed, the JPEG 2000 image coding framework is commonly used for holographic compression because of its modular and extendable architecture. These three steps will be discussed in more detail hereafter. We shall focus especially on wavelet-based schemes, as they offer appealing features for holographic data. Furthermore, as a special case of wavelet-based schemes, we shall also introduce JPEG 2000, which has been applied efficiently for the compression of holograms.

Chapter 6 – Concluding Remarks

In this book, we presented an overview of existing techniques for the compression of holographic data. Despite the existing body of published research, more efforts are needed. In particular, we can identify the following open issues which need further investigations. First, it is important to carry out systematic and comprehensive investigations in order to understand better the effect of the wide parameters space to generate digital holograms. Second, common datasets are needed in order to allow researchers to compare various approaches meaningfully. Third, better performance assessment methodologies need to be defined. Fourth, it is paramount to consider more complex scenes representative of realistic application scenarios. Finally, another key open issue is to understand at which stage of the processing pipeline compression needs to be performed.

Fundamental Principles of Digital Holography

In order to have a better understanding of holography, this chapter outlines the main aspects relevant for the optical and numerical imaging principles of DH. Two main physical principles—interference and diffraction—of holography are first introduced, which correspond to the procedures of hologram acquisition and its reconstruction. Based on the physical principles, computational methods for generating digital holograms and numerical reconstruction have been developed.