Malcolm McCormick

Design and analysis of an image transfer system using microlens arrays

Efficient large-aperture lens elements are required for 3-D integral imaging and display systems. A systematic evaluation of the spatial resolution capabilities of microlens optical combinations and the synthesis of a large-aperture objective lens by a segmented lens form is reported. It is shown that by employing an optical combination comprising macrolens arrays in conjunction with microlens focusing screens a suitable transmission element, which retains the required angular and lateral resolution, can be constructed. The advantage of using segmented lenses is their capacity to produce spatially inverted, scaled images suitable for direct orthoscopic capture. The analysis of spatial resolution presented by various authors is examined and evaluated by comparison with collated evidence.

Analytical model of a three-dimensional integral image recording system that uses circular- and hexagonal-based spherical surface microlenses.

A mathematical model for a three-dimensional omnidirectional integral recording camera system that uses either circular- or hexagonal-based spherical surface microlens arrays is derived. The geometry of the image formation and recording process is fully described. Matlab is then used to establish the number of recorded micro-intensity distributions representing a single object point and their dependence on spatial position. The point-spread function for the entire optical process for both close and remote imaging is obtained, and the influence of depth on the point-spread dimensions for each type of microlens and imaging condition is discussed. Comparisons of the two arrangements are made, based on the illustrative numerical results presented.

Adaptive 3D-DCT compression algorithm for continuous parallax 3D integral imaging

Abstract Integral imaging is employed as part of a three-dimensional imaging system, allowing the display of full colour images with continuous parallax within a wide viewing zone. A significant quantity of data is required to represent a captured integral 3D image with high resolution. A lossy compression scheme has been developed based on the use of a 3D-DCT, which make possible efficient storage and transmission of such images, while maintaining all information necessary to produce a high quality 3D display. In this paper, a novel approach to the problem of compressing the significant quantity of data required to represent integral 3D images is presented. The algorithm is based on using a variable number of microlens images (or sub-images) in the computation of the 3D-DCT. It involves segmentation of the planar mean image formed by the mean values of the microlens images and it takes advantage of the high cross-correlation between the sub-images generated by the microlens array. The algorithm has been simulated on several integral 3D images. It was found that the proposed algorithm improves the rate-distortion performance when compared to baseline JPEG and previously reported 3D-DCT compression scheme with respect to compression ratio and subjective and objective image quality.

Continuous parallax in discrete pixelated integral three-dimensional displays

An evaluation of the retention of continuous parallax in pixelated integral three-dimensional image displays is presented. The integral image capture process is first considered, to provide a starting point for the investigation. The complementary display system is then examined in detail. The viewing geometry of the display system is analyzed to provide a foundation for the work to follow, and an experimental investigation and simulations of the characteristics of emitted ray bundles are presented. Next, an analytical model of decoding lenslet array operation is derived, leading to an understanding of the process responsible for production of continuous parallax in replay. It is found that if the lateral resolution of the lenslet is matched to that of the display, continuous parallax is retained in the replayed image, where the finite aberration-limited resolution of the lenslet acts to produce a low-pass reconstruction filter. A condition is derived for optimal continuous parallax in replay, based on a relationship between pixel width and lenslet rms spot size.

Depth Mapping of Integral Images Through Viewpoint Image Extraction With a Hybrid Disparity Analysis Algorithm

Integral imaging is a technique capable of displaying 3D images with continuous parallax in full natural color. It is one of the most promising methods for producing smooth 3D images. Extracting depth information from integral image has various applications ranging from remote inspection, robotic vision, medical imaging, virtual reality, to content-based image coding and manipulation for integral imaging based 3D TV. This paper presents a method of generating a depth map from unidirectional integral images through viewpoint image extraction and using a hybrid disparity analysis algorithm combining multi-baseline, neighborhood constraint and relaxation strategies. It is shown that a depth map having few areas of uncertainty can be obtained from both computer and photographically generated integral images using this approach. The acceptable depth maps can be achieved from photographic captured integral images containing complicated object scene.

The number of electrodes and basis functions in EIT image reconstruction

In electrical impedance tomography, many factors affect the image reconstruction results. Among them are the number of electrodes (NOE) and the number of conductivity basis functions (NOCBF) for image reconstruction. The NOCBF generally reflects the density of the mesh with which images are reconstructed. How and to what extent do these factors affect the image reconstruction and corresponding images? In this area detailed analysis is still lacking. This study aims to address the above question. In this study, image reconstruction and its ill-posed condition were analysed by singular value decomposition (SVD) and spectral expansion theory with different configurations of NOE and NOCBF. The results in this study indicate that for a circular 2D plane object with electrodes evenly located around the boundary: (1) Under certain conditions, increasing the NOE enables us to improve the ill-posed condition in image reconstruction and hence improve the image quality. Generally more improvement is expected near the image periphery than in the image centre. (2) Increasing the NOCBF generally worsens the ill-posed condition. But it enables the solution to be sought in a finer subspace and may be able to improve the image quality on the periphery, while generally the result in image centre depends more on the prior information incorporated in the regularization.

The application and optimization of C-type filter in a combined harmonic power filter

A new construction of hybrid power filters, which needs lower capacity of active component comparing with existing hybrid power filter, is proposed. In order to decrease the rating of active filter, a C-type filter is adopted which is in series with the active filter, for its high impedance at the fundamental frequency while presenting a low impedance at the harmonic frequencies. The most active power filters existed require a large power rating, while this configuration can reduce large rating of active power filter as the C-type filter carries most of the fundamental voltage. In order to be satisfied the criterion of the harmonics compensation and run in an economic way, a parameters optimization of C-type filter is put forwarded. The simulation is made in this paper, which is with the optimized parameters. It is confirmed by analysis and simulation that the combined power filter with optimized C-type filter runs in an effective and economic way in the harmonic compensation.

A novel coding scheme for full parallax 3D-TV pictures

A unique integral imaging system is employed as part of a three dimensional television system, allowing display of full colour 3D images with continuous parallax within a wide viewing zone. A significant quantity of data is required to represent captured integral 3D images with adequate resolution. A a lossy compression scheme is described, based on the use of a three dimensional discrete cosine transform (3D-DCT), which makes possible efficient storage and transmission of such images while maintaining all information necessary to produce a high quality 3D display. The results of simulations performed using the 3D-DCT algorithm are presented and it is shown that the rate-distortion performance is vastly improved compared with that achieved using baseline JPEG, with captured integral 3D image data.

Depth extraction from unidirectional integral image using a modified multibaseline technique

Integral imaging is a technique capable of displaying images with continuous parallax in full natural color. This paper presents a modified multi-baseline method for extracting depth information from unidirectional integral images. The method involves first extracting sub-images from the integral image. A sub-image is constructed by extracting one pixel from each micro-lens rather than a macro-block of pixels corresponding to a micro-lens unit. A new mathematical expression giving the relationship between object depth and the corresponding sub-image pair displacement is derived by geometrically analyzing the three-dimensional image recording process. A correlation- based matching technique is used fo find the disparity between two sub-images. In order to improve the disparity analysis, a modified multi-baseline technique where the baseline is defined as the distance between two corresponding pixels in different sub-images is adopted. The effectiveness of this modified multi-baseline technique in removing the mismatching caused by similar patterns in object scenes has been proven by analysis and experiment results. The developed depth extraction method is validated and applied to both photographic and computer generated unidirectional integral images. The depth estimation solution gives a precise description of object thickness with an error of less than 1.0% from the photographic image in the example.

FPGA fuzzy logic controller for variable speed generators

The research work carried out in the area of design, simulation and implementation of a fuzzy logic controller for a diesel-driven stand alone synchronous generator system is presented. The controller was developed using Very High Speed Integrated Circuit Hardware Description Language (VHDL) and is implemented in a field programmable gate array (FPGA). The advantages of the proposed system, consisting of diesel engine, synchronous generator, power converter and fuzzy controller, are underlined. The experimental results proved the correct operation of the system.