Wide-viewing integral three-dimensional imaging by use of orthogonal polarization switching

A wide-viewing integral three-dimesional (3D) imaging system that adopts orthogonal polarization switching is proposed and demonstrated. In our scheme,the polarizing sheet attached to the lens array and the orthogonal polarization switching of the elemental image array perform elemental lens switching. The experimental results document that the viewing angle becomes remarkably wider than that of the conventional method. The distinguishing feature of our system is that it requires no mechanical moving part. In addition, because a commercially available polarization shutter screen is used for electrical switching, it is easy to implement this as a practical system. We believe that the proposed method facilitates the practical use of this wide-viewing integral 3D imaging system.     

3‐D spatiotemporal subband decomposition of image sequences by mathematical morphology

Abstract

An efficient 3‐D spatiotemporal image sequence decomposition method using mathematical morphology is described in this paper. The method can be used to decompose the spectrum of the input signal into 8 and 4 spatiotemporal subband images. It does this using two different sets of structuring elements. After decomposition, each band image can be decimated and coded for data transmission. This subband pyramid scheme preserves the number of pixels which existed in the original image, has an efficient hierarchical data structure, and allows parallel implementation. Therefore, this scheme has great potential for High Definition Television (HDTV) coding, multimedium video compression, etc. As regards filtering, the unique advantages of morphology over the linear filtering approach are: 1) it utilizes direct geometric interpretations; and 2) it is simple and efficient when used in conjunction with parallel/pipelining hardware. Some image sequence examples are given to show the effectiveness of this approach.     

Image coding based on wavelet feature vector

In this article, an efficient image coding scheme that takes advantages of feature vector in wavelet domain is proposed. First, a multi‐stage discrete wavelet transform is applied on the image. Then, the wavelet feature vectors are extracted from the wavelet‐decomposed subimages by collecting the corresponding wavelet coefficients. And finally, the image is coded into bit‐stream by applying vector quantization (VQ) on the extracted wavelet feature vectors. In the encoder, the wavelet feature vectors are encoded with a codebook where the dimension of codeword is less than that of wavelet feature vector. By this way, the coding system can greatly improve its efficiency. However, to fully reconstruct the image, the received indexes in the decoder are decoded with a codebook where the dimension of codeword is the same as that of wavelet feature vector. Therefore, the quality of reconstructed images can be preserved well. The proposed scheme achieves good compression efficiency by the following three methods. (1) Using the correlation among wavelet coefficients. (2) Placing different emphasis on wavelet coefficients at different decomposing levels. (3) Preserving the most important information of the image by coding the lowest‐pass subimage individually. In our experiments, simulation results show that the proposed scheme outperforms the recent VQ‐based image coding schemes and wavelet‐based image coding techniques, respectively. Moreover, the proposed scheme is also suitable for very low bit rate image coding. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 123–130, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20045     

Generation of three-dimensional integral images from a holographic pattern of 3-D objects

We present a novel approach for generating three-dimensional (3-D) integral images from a fringe pattern of 3-D objects. A recorded hologram of 3-D objects is segmented into a number of subholograms. Then, different views of 3-D objects are reconstructed from them because each subhologram has its own perspective of 3-D objects in the recording process. These locally reconstructed images can be rearranged as the same subimage array of the conventional integral-imaging system and transformed into virtually picked-up elemental images of 3-D objects. From this newly generated elemental image array, 3-D images could easily be reconstructed by using a white light. Experiments with a 3-D test object have been performed and the results have been presented.     

Visibility-enhanced reconstruction of three-dimensional objects under a heavily scattering medium through combined use of intermediate view reconstruction, multipixel extraction, and histogram equalization methods in the conventional integral imaging system

In this paper, we propose an effective approach for reconstructing visibility-enhanced three-dimensional (3D) objects under the heavily scattering medium of dense fog in the conventional integral imaging system through the combined use of the intermediate view reconstruction (IVR), multipixel extraction (MPE), and histogram equalization (HE) methods. In the proposed system, the limited number of elemental images (EIs) picked up from the 3D objects under the dense fog is increased by as many as required by using the IVR technique. The increased number of EIs is transformed into the subimages (SIs) in which the resolution of the transformed SIs has been also improved as much as possible with the MPE method. Subsequently, by using the HE algorithm, the histogram of the resolution-enhanced SIs is uniformly redistributed over the entire range of discrete pixel levels of the image in a way that the subimage contrast can be much enhanced. Then, these equalized SIs are converted back into the newly modified EIs, and consequently a visibility-enhanced 3D object image can be reconstructed. Successful experimental results with the test object confirmed the feasibility of the proposed method.     

Optimization of wireframe model adaptation and motion estimation in a rate-distortion framework

A rate-distortion framework is used to define a very low-bit-rate coding scheme based on wireframe model adaptation and optimized selection of motion estimators. This technique achieves maximum reconstructed image quality under the constraint of a target bit rate for the coding of the vector field and the wireframe representation information. First, a complete scheme is proposed for hybrid two-dimensional (2D) and 3D motion estimation and compensation. The wireframe adaptation and updating is optimized for hybrid motion estimation in the rate distortion sense. A more sophisticated technique, adapted to the requirements of a very low-bit-rate coder is also proposed which considers also the transmission of the prediction error corresponding to the particular choice of the motion estimator for each object in the scene. Experimental results illustrating the performance of the proposed techniques in very low-bit-rate image sequence coding application areas are presented and evaluated. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 238–247, 1998     

Real-time three-dimensional object recognition with multiple perspectives imaging

A novel system for recognizing three-dimensional (3D) objects by use of multiple perspectives imaging is proposed. A 3D object under incoherent illumination is projected into an array of two-dimensional (2D) elemental images by use of a microlens array. Each elemental 2D image corresponds to a different perspective of the 3D object. Multiple perspectives imaging based on integral photography has been used for 3D display. In this way, the whole set of 2D elemental images records 3D information about the input object. After an optical incoherent-to-coherent conversion, an optical processor is employed to perform the correlation between the input and the reference 3D objects. Use of micro-optics allows us to process the 3D information in real time and with a compact optical system. To the best of our knowledge this 3D processor is the first to apply the principle of integral photography to 3D image recognition. We present experimental results obtained with both a digital and an optical implementation of the system. We also show that the system can recognize a slightly out-of-plane rotated 3D object.     

Microlens arrays for integral imaging system

When designing a system capable of capturing and displaying 3D moving images in real time by the integral imaging (II) method, one challenge is to eliminate pseudoscopic images. To overcome this problem, we propose a simple system with an array of three convex lenses. First, the lateral magnification of the elemental optics and the expansion of an elemental image is described by geometrical optics, confirming that the elemental optics satisfies the conditions under which pseudoscopic images can be avoided. In using the II method, adjacent elemental images must not overlap, a condition also satisfied by the proposed optical system. Next, an experiment carried out to acquire and display 3D images is described. The real-time system we have constructed comprises an elemental optics array with 54 H x 59 V elements, a CCD camera to capture a group of elemental images created by the lens array, and a liquid crystal panel to display these images. The results of the experiment confirm that the system produces orthoscopic images in real time, and thus is effective for real-time application of the II method.     

3D multiwavelet based block coding algorithm for compression of volumetric medical images

Three dimensional (3D) medical images possess some specific characteristics that should be utilized by an efficient compression scheme. In this article, one such compression scheme for volumetric 3D medical image data is presented. Two processes involved in this scheme are decorrelation and encoding. Decorrelation of the 3D data is realized through 3D multiwavelet transform with apt prefiltering so as to give good representation of the image which could be exploited by the encoder. Encoding is done through proposed Block Coding Algorithm, which is embedded, block based, and wavelet transform coding algorithm without maintaining any list structures. The idea behind this algorithm is to sort the 3D transform coefficients in to a 1D array with respect to declining thresholds and to use state table to keep track of the blocks and coefficients that has been coded. In the experiment conducted on various 3D magnetic resonance and computed tomography images of human brain with multiwavelets such as Geronimo–Hardin–Massopust, Chui‐Lian, and orthogonal symmetric/antisymmetric (SA4), efficiency of the proposed scheme was weighed against the state of art encoders such as 3D Set Partitioning in Hierarchical Trees, 2D Set Partitioned Embedded BloCK Coder, and No List SPIHT. Attributes used for performance measurements are peak signal to noise ratio, bit rate, and structural similarity index of reconstructed image with respect to original image. © 2014 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 24, 182–192, 2014     

Three-dimensional Dammann vortex array with tunable topological charge

We describe a kind of true 3D array of focused vortices with tunable topological charge, called the 3D Dammann vortex array. This 3D Dammann vortex array is arranged into the structure of a true 3D lattice in the focal region of a focusing objective, and these focused vortices are located at each node of the 3D lattice. A scheme based on a Dammann vortex grating (DVG) and a mirror is proposed to provide a choice for changing the topological charge of the 3D Dammann vortex array. For experimental demonstration, a 5×5×5 Dammann vortex array is implemented by combining a 1×7 DVG, a 1×5 Dammann zone plate, and another 5×5 Dammann grating. The topological charge of this Dammann vortex array can be tuned (from -2 to +2 with an interval of +1) by moving and rotating the mirror to select different diffraction orders of the 1×7 DVG as the incident beam. Because of these attractive properties, this 3D Dammann vortex array should be of high interest for its potential applications in various areas, such as 3D simultaneous optical manipulation, 3D parallel vortex scanning microscope, and also parallel vortex information transmission.     

一种室内视频监控图像序列编码方法

在实际高分辨率室内视频监控中,运动物体构成了视频监控的主要内容.本文基于感兴趣区域的检测与恢复,提出了一种高分辨率室内视频监控图像序列的编码新方法,通过对象提取实现基本层和ROI层双层码流传输,其中基本层实现低分辨率图像内容传输,而ROI层用以进行高分辨率图像恢复.新方法有效地降低了视频编码计算复杂度、提高了编码效率.     

Efficient bit‐plane coding scheme for fine granular scalable video coding

In this paper, we propose a new efficient bit‐plane coding method for fine granular scalable (FGS) video coding. The general structure of the proposed bit‐plane coding method is based on the traditional bit‐plane coding scheme in MPEG‐4 FGS. However, to enhance coding efficiency of bit‐plane encoding, we apply an efficient probability estimation scheme through employing the binary arithmetic coding. For probability estimation, various context models are designed to take advantage of the characteristics of each bit‐plane as well as the correlations of symbols among different bit‐planes. Experimental results show that the proposed FGS coding scheme provides better coding performance, compared to the well‐known FGS coding schemes in MPEG‐4 FGS and JSVM. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 16, 113–120, 2006.     

Three-dimensional Dammann array

We demonstrate a scheme that can produce a three-dimensional (3D) focus spot array in a 3D lattice structure, called a 3D Dammann array, in focal region of an objective. This 3D Dammann array is generated by using two separate micro-optical elements, a Dammann zone plate (DZP) that produces a series of coaxial focus spots and a conventional two-dimensional (2D) Dammann grating (DG). A simple, fast, and clear method is presented to design this binary pure-phase (0,π) DZP in vectorial Debye theory regime. Based on this kind of DZP, one can always obtain a 3D Dammann array both for low and high numerical aperture (NA) focusing objectives. For experimental demonstration, an arrangement combining a DZP, a 2D DG, and a pair of opposing lenses is proposed to generate a 5×5×5 Dammann array in focal region of an objective with NA=0.127 and another 6×6×7 Dammann array for an objective of NA=0.66. It is shown that this arrangement makes it possible to achieve 3D Dammann arrays with micrometer-sized focus spots and focus spacings of tens of micrometers for various practical applications, such as 3D parallel micro- and nanomachining, 3D simultaneous optical manipulation, 3D optical data storage, and multifocal fluorescence microscope, etc.     

Extended coding for optical array logic

We present extended coding for optical array logic (OAL) to avoid the marginal effect. The marginal effect is defined as an effect caused by the finite size of the image region, and it is a problem in massively parallel processing by OAL. OAL is a paradigm of optical computing suitable for optical implementation utilizing image coding and discrete correlation. To avoid the marginal effect in the context of OAL, we propose a new coding rule and consider possible operations with this coding. With extended coding, binary data can be identified from background with the same number of pixels as that used in the original OAL. Simulation results of the operations verify the correctness of the proposed technique.     

Three-dimensional complex image coding using a circular Dammann grating

Recently, optical image coding using a circular Dammann grating (CDG) has been proposed and investigated. However, the proposed technique is intensity based and could not be used for three-dimensional (3D) image coding. In this paper, we investigate an optical image coding technique that is complex-amplitude based. The system can be used for 3D image coding. The complex-amplitude coding is provided by a circular Dammann grating through the use of a digital holographic recording technique called optical scanning holography. To decode the image, along the depth we record a series of pinhole holograms coded by the CDG. The decoded reconstruction of each depth location is extracted by the measured pinhole hologram matched to the desired depth. Computer simulations as well as experimental results are provided.     

Scheme to improve the reconstructed image in parallel quasi-phase-shifting digital holography

We propose a scheme to improve the reconstructed image in parallel quasi-phase-shifting digital holography. Parallel quasi-phase-shifting digital holography is a technique capable of noiseless instantaneous measurement of three-dimensional objects, and it implements four kinds of phase shifting at a time with an array of 2 x 2 phase-shifting devices located in the reference wave. In the phase-shifting calculation in the reconstruction process of the technique, the scheme assigns the 2 x 2 cell configuration for each pixel in the vertical direction and for each 1-pixel interval in the horizontal direction of the hologram recorded by the image sensor. We conduct both a numerical simulation and a preliminary experiment. The results show that the proposed scheme can improve the quality of the reconstructed image calculated by the conventional scheme of parallel quasi-phase-shifting digital holography we previously proposed, and then the effectiveness of the proposed scheme is verified.     

Efficient depth map compression for view rendering in 3D video

Abstract

A depth map represents three-dimensional (3D) scene information, which is used to synthesise virtual views in 3D video coding. Since the quality of synthesised virtual view highly depends on the quality of depth map, efficient depth coding is crucial for the 3D video system. However, depth map is not directly used for display but to generate virtual views. Compressing depth map using existing video coding techniques yields unacceptable distortions in rendered virtual view. Thus, the depth map needs to be compressed in a way that can minimise distortions in the rendered views. To solve this problem, we propose an efficient depth map compression method for view rendering based on view rendering distortion other than depth map distortion itself. Firstly, we derive relationship between distortion in coded depth map and the rendered view. Then, a region-based video characteristic distortion model is proposed to precisely estimate distortion in view synthesis. Finally, a multilateral filtering is applied as an in-loop filter to reduce rendering artefacts. Experimental results show that the proposed method achieves 2 dB coding gain in terms of PSNR and subjective quality improvement of synthesised views.     

自适应六边形-菱形运动估计算法及其在H.264中应用

运动估计是视频图像编码中运算量很大的部分,也是影响系统实时性能的瓶颈。为了减少图像编码的运算量,文章介绍和分析了用于视频编码标准H.264的基于六边形的搜索算法(HS),在此基础上根据H.264多模式的运动估计提出自适应六边形-菱形整像素算法,它体现了粗定位和准确定位的并行处理思想,仿真结果表明在获得与HS快速算法相当的图像质量和信噪比的情况下,可提高H.264视频编码的速度和效率。     

A new shape-vector quantization-based adaptive predictive image coder

In this paper, a new lossless image compression technique, shape-vector quantization (VQ)-based adaptive predictive coder (SAPC), is introduced. In the proposed scheme, the local shape information of the image block is obtained through shape-VQ. This information is utilized by a novel predictive coder, shape-differential pulse code modulation (DPCM), to adaptively select the optimum predictor on a pixel-by-pixel basis. The prediction errors can be further compressed by an error-adjusting process. The proposed scheme achieves a breakthrough in prediction by utilizing the local feature of the image block through shape-VQ, thus improving the accuracy of the prediction while reducing the overhead of the side information. It also simplifies the complicated procedures involved in the computation of the prediction parameters. Although the proposed scheme outperforms many traditional lossless image-coding schemes, it produces comparable results to the newly developed context-based scheme with lower computational complexity. On the basis of the promising compression results, the proposed scheme could be the best candidate for the lossless image coding. © 2000 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 10, 419–426, 1999     

Colour image coding scheme using absolute moment block truncation coding and block prediction technique

Abstract

A predictive colour image compression scheme based on absolute moment block truncation coding is proposed. In this scheme, the high correlations among neighbouring image blocks are exploited by using the similar block prediction technique. In addition, the bit plane omission technique and the coding of quantisation levels are used to cut down the storage cost of smooth blocks and complex blocks respectively. According to the experimental results, the proposed scheme provides better performance than the comparative schemes based on block truncation coding. It provides better image qualities of compressed images at low bit rates. Meanwhile, it consumes very little computational cost. In other words, the proposed scheme is quite suitable for real time multimedia applications.