Evaluation of changes in image appearance with changes in displayed image size

This research focused on the quantification of changes in image appearance when images are displayed at different image sizes on LCD devices. The final results provided in calibrated Just Noticeable Differences (JNDs) on relevant perceptual scales, allowing the prediction of sharpness and contrast appearance with changes in the displayed image size. A series of psychophysical experiments were conducted to enable appearance predictions. Firstly, a rank order experiment was carried out to identify the image attributes that were most affected by changes in displayed image size. Two digital cameras, exhibiting very different reproduction qualities, were employed to capture the same scenes, for the investigation of the effect of the original image quality on image appearance changes. A wide range of scenes with different scene properties was used as a test-set for the investigation of image appearance changes with scene type. The outcomes indicated that sharpness and contrast were the most important attributes for the majority of scene types and original image qualities. Appearance matching experiments were further conducted to quantify changes in perceived sharpness and contrast with respect to changes in the displayed image size. For the creation of sharpness matching stimuli, a set of frequency domain filters were designed to provide equal intervals in image quality, by taking into account the system’s Spatial Frequency Response (SFR) and the observation distance. For the creation of contrast matching stimuli, a series of spatial domain S-shaped filters were designed to provide equal intervals in image contrast, by gamma adjustments. Five displayed image sizes were investigated. Observers were always asked to match the appearance of the smaller version of each stimulus to its larger reference. Lastly, rating experiments were conducted to validate the derived JNDs in perceptual quality for both sharpness and contrast stimuli. Data obtained by these experiments finally converted into JND scales for each individual image attribute. Linear functions were fitted to the final data, which allowed the prediction of image appearance of images viewed at larger sizes than these investigated in this research

Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

Impact of opening geometry on the Indoor Environmental Quality in deep, open-plan, naturally ventilated office typologies in temperate climates

Natural ventilation is one means of enriching internal environmental quality (IEQ) whilst reducing the energy consumption of buildings. In an attempt to increase productivity, offices are often deep and open-plan. The typically large energy demands of this type of building indicates the potential to ascertain significant energy savings and a reduction in carbon dioxide (CO2) emissions. Through careful design, the forces associated with natural ventilation can be harnessed and utilised. These small forces mean opening geometry and building form can determine the internal natural airflow patterns, potentially creating unexpected flow characteristics. In these cases, this could lead to a naturally ventilated space overheating, exposing the occupants to thermal discomfort and, in such events, the supply of fresh air may also be reduced. With respect to an energy conscious environment, some leading architectural firms are beginning to explore the use of high-aspect-ratio (HAR) facade openings to improve the IEQ of these spaces. In addition to this, architects are encouraged by client briefs to design deep, open-plan offices without the typical central core; this being a vital element in any multi-storey building, comprising vertical circulation, services, toilets and lifts. To assist in the ventilation of these spaces, they are often broken-up by impressive atrium/atria. Research suggests, the design of facade openings, atrium and building core may influence the performance of the proposed natural ventilation strategy. The thorough examination of innovative design solutions should address these uncertainties and avoid them where possible. However, there is a lack of detailed evidence and guidance is needed to increase design confidence and the utilisation of optimal office design. To better understand natural ventilation, computer and physical airflow modelling, such as computational fluid dynamics (CFD) and water-bath modelling (WBM) are used. The use of multiple techniques not only allows the opportunity to validate the results from each, but also increases the amount of highly detailed data in various formats. Nevertheless, such physical models are often under-utilised, difficult to construct and operate, and expensive. The investigation of the ventilation performance of HAR openings in a generic office environment was carried out using computational models and a novel WBM. Overall ventilation performance was obtained through the installation of the variants of opening geometries into several office configurations with differing core and atrium designs. The utilisation of multiple validated models improved the examination of ventilation performance, thus, providing reliable results to compliment those from the main body of the study. The parametric study was formed of many CFD cases, enabling the juxtaposition of the ventilation performance of all office configurations. The transient nature of WBM and spatial detail of CFD gave the ability to scrutinize issues associated with IEQ; air velocity and thermal stratification and distribution, mean room air temperatures and ventilation flow rates. Therefore, the acknowledgement of the optimal office design allowed the better performing design variants to be highlighted in terms of ventilation performance, also providing a greater understanding of how the design of the space affects IEQ. To start, an archetypal building, which would be subjected to the alternative design parameters, was established. The WBM's form, enabled multiple experiments to be performed by a relatively cheap and easy to run and maintain WBM, thus, increasing the rigour of the validation process and resultant design guidance. A comparison of the results from both modelling techniques showed them to be working correctly, as errors concerning validation metrics were deemed negligible. Results from the WBM experiments and CFD simulations suggested the supply flow from high-level horizontal (HLH) openings brought warm, potentially stale air down into the occupied zones. Conversely, the flow from mid-level vertical (MLV) openings was shown by the CFD to assist in the formation and lowering of thermal stratification. Nonetheless, significant improvements in ventilation flow rates and cooler air temperatures were possible. Moreover, the ventilation performance of this opening design was independent of the means of air removal. Additional enhancements were achieved by a transition from a typical to a perimeter core, as the prevalence of unventilated areas and excessive air velocities was reduced. Nevertheless, when specific variants of atrium design were employed into the perimeter core cases, further performance improvements were perceived. The conditions pervading the now open floor plate, were shown to be enhanced by an atrium design closely replicating the building's footprint. It could be said, the optimal core location is on the perimeter furthest away from the atrium. This configuration, when used in combination with MLV fa\c cade openings, was shown to form the best performing. Substantial advancements have been proposed in the physical modelling procedure of natural ventilation. Further understanding has also been obtained from the results produced, which formed the foundation of the design guidance. The inclusion of these modelling modifications and evidenced guidance throughout the design stage will alleviate performance uncertainties, making the undertaking of naturally ventilated building projects more attractive, simultaneously enhancing the IEQ of low-energy offices.</div

Motion Parallax in Stereo 3D: Model and Applications

Binocular disparity is the main depth cue that makes stereoscopic images appear 3D. However, in many scenarios, the range of depth that can be reproduced by this cue is greatly limited and typically fixed due to constraints imposed by displays. For example, due to the low angular resolution of current automultiscopic screens, they can only reproduce a shallow depth range. In this work, we study the motion parallax cue, which is a relatively strong depth cue, and can be freely reproduced even on a 2D screen without any limits. We exploit the fact that in many practical scenarios, motion parallax provides sufficiently strong depth information that the presence of binocular depth cues can be reduced through aggressive disparity compression. To assess the strength of the effect we conduct psycho-visual experiments that measure the influence of motion parallax on depth perception and relate it to the depth resulting from binocular disparity. Based on the measurements, we propose a joint disparity-parallax computational model that predicts apparent depth resulting from both cues. We demonstrate how this model can be applied in the context of stereo and multiscopic image processing, and propose new disparity manipulation techniques, which first quantify depth obtained from motion parallax, and then adjust binocular disparity information accordingly. This allows us to manipulate the disparity signal according to the strength of motion parallax to improve the overall depth reproduction. This technique is validated in additional experiments

Methods for reducing visual discomfort in stereoscopic 3D: A review

This work was supported by the EPSRC Grant EP/M01469X/1, “Geometric Evaluation of Stereoscopic Video”

Human operator performance of remotely controlled tasks: Teleoperator research conducted at NASA's George C. Marshal Space Flight Center

The capabilities within the teleoperator laboratories to perform remote and teleoperated investigations for a wide variety of applications are described. Three major teleoperator issues are addressed: the human operator, the remote control and effecting subsystems, and the human/machine system performance results for specific teleoperated tasks

Holoscopic 3D image depth estimation and segmentation techniques

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonToday’s 3D imaging techniques offer significant benefits over conventional 2D imaging techniques. The presence of natural depth information in the scene affords the observer an overall improved sense of reality and naturalness. A variety of systems attempting to reach this goal have been designed by many independent research groups, such as stereoscopic and auto-stereoscopic systems. Though the images displayed by such systems tend to cause eye strain, fatigue and headaches after prolonged viewing as users are required to focus on the screen plane/accommodation to converge their eyes to a point in space in a different plane/convergence. Holoscopy is a 3D technology that targets overcoming the above limitations of current 3D technology and was recently developed at Brunel University. This work is part W4.1 of the 3D VIVANT project that is funded by the EU under the ICT program and coordinated by Dr. Aman Aggoun at Brunel University, West London, UK. The objective of the work described in this thesis is to develop estimation and segmentation techniques that are capable of estimating precise 3D depth, and are applicable for holoscopic 3D imaging system. Particular emphasis is given to the task of automatic techniques i.e. favours algorithms with broad generalisation abilities, as no constraints are placed on the setting. Algorithms that provide invariance to most appearance based variation of objects in the scene (e.g. viewpoint changes, deformable objects, presence of noise and changes in lighting). Moreover, have the ability to estimate depth information from both types of holoscopic 3D images i.e. Unidirectional and Omni-directional which gives horizontal parallax and full parallax (vertical and horizontal), respectively. The main aim of this research is to develop 3D depth estimation and 3D image segmentation techniques with great precision. In particular, emphasis on automation of thresholding techniques and cues identifications for development of robust algorithms. A method for depth-through-disparity feature analysis has been built based on the existing correlation between the pixels at a one micro-lens pitch which has been exploited to extract the viewpoint images (VPIs). The corresponding displacement among the VPIs has been exploited to estimate the depth information map via setting and extracting reliable sets of local features. ii Feature-based-point and feature-based-edge are two novel automatic thresholding techniques for detecting and extracting features that have been used in this approach. These techniques offer a solution to the problem of setting and extracting reliable features automatically to improve the performance of the depth estimation related to the generalizations, speed and quality. Due to the resolution limitation of the extracted VPIs, obtaining an accurate 3D depth map is challenging. Therefore, sub-pixel shift and integration is a novel interpolation technique that has been used in this approach to generate super-resolution VPIs. By shift and integration of a set of up-sampled low resolution VPIs, the new information contained in each viewpoint is exploited to obtain a super resolution VPI. This produces a high resolution perspective VPI with wide Field Of View (FOV). This means that the holoscopic 3D image system can be converted into a multi-view 3D image pixel format. Both depth accuracy and a fast execution time have been achieved that improved the 3D depth map. For a 3D object to be recognized the related foreground regions and depth information map needs to be identified. Two novel unsupervised segmentation methods that generate interactive depth maps from single viewpoint segmentation were developed. Both techniques offer new improvements over the existing methods due to their simple use and being fully automatic; therefore, producing the 3D depth interactive map without human interaction. The final contribution is a performance evaluation, to provide an equitable measurement for the extent of the success of the proposed techniques for foreground object segmentation, 3D depth interactive map creation and the generation of 2D super-resolution viewpoint techniques. The no-reference image quality assessment metrics and their correlation with the human perception of quality are used with the help of human participants in a subjective manner