编目研究的直观与扩展——基于影像的文物研究系统

利用高精度数字影像技术对藏品进行展示、编目和研究,是近年来数字故宫建设的重要研究方向。本文介绍了故宫基于影像的文物研究系统建设的过程及应用情况,并着重对系统建设中遇到的技术难点进行了探讨。     

A continuous‐viewing‐angle‐controllable liquid‐crystal display using a blue‐phase liquid crystal

Abstract— A continuous‐viewing‐angle‐controllable liquid‐crystal display (LCD) using a blue‐phase liquid crystal is proposed. To realize both wide‐viewing‐angle (WVA) mode and narrow‐viewing‐angle (NVA) mode with a single liquid‐crystal panel, each pixel is divided into a main pixel and a subpixel. The main pixel is for displaying images in both modes. The subpixel is for displaying images in WVA mode and controlling the viewing angle in NVA mode. The device exhibits a good viewing‐angle‐controlling characteristic and high transmittance.     

A common approach to characterizing autostereoscopic and polarization‐based 3‐D displays

Abstract— Autostereoscopic and polarization‐based stereoscopic 3‐D displays recreate 3‐D images by providing different images in the two eyes of an observer. This aim is achieved differently for these two families of 3‐D displays. It is shown that viewing‐angle measurements can be applied to characterize both types of displays. Viewing‐angle luminance measurements are made at different locations on the display surface for each view emitted by the display. For autostereoscopic displays, a Fourier‐optics instrument with an ultra‐high‐angular‐resolution VCMaster3D is used. For polarization‐based displays, a standard Fourier‐optics instrument with additional glass filters is used. Then, what will be seen by an observer in front of the display is computed. Monocular and binocular quality criteria (left‐ and right‐eye contrast, 3‐D contrast) was used to quantify the ability to perceive depth for any observer position. Qualified monocular and binocular viewing spaces (QMVS and QBVS) are deduced. Precise 3‐D characteristics are derived such as maximum 3‐D contrast, optical viewing freedom in each direction, color shifts, and standard contrast. A quantitative comparison between displays of all types becomes possible.     

基于Web的异构CAD协同批注系统的设计与实现

随着协同工作的广泛深入,协同浏览与批注技术作为协同技术的重要组成部分,对产品设计平台异构性支持的需求也越来越迫切.对"基于Web的支持异构CAD数据的浏览与批注技术"和"基于Web的协同技术"等进行了初步研究,并在此基础上开发了一套基于Web的支持异构CAD数据的协同浏览与批注原型系统.研究结果表明,该系统可以实现异构CAD数据基于Web的协同浏览与批注,加快了产品设计进程,提高了设计效率.     

SMIL State: an architecture and implementation for adaptive time-based web applications

In this paper we examine adaptive time-based web applications (or presentations). These are interactive presentations where time dictates which parts of the application are presented (providing the major structuring paradigm), and that require interactivity and other dynamic adaptation. We investigate the current technologies available to create such presentations and their shortcomings, and suggest a mechanism for addressing these shortcomings. This mechanism, SMIL State, can be used to add user-defined state to declarative time-based languages such as SMIL or SVG animation, thereby enabling the author to create control flows that are difficult to realize within the temporal containment model of the host languages. In addition, SMIL State can be used as a bridging mechanism between languages, enabling easy integration of external components into the web application. Finally, SMIL State enables richer expressions for content control. This paper defines SMIL State in terms of an introductory example, followed by a detailed specification of the State model. Next, the implementation of this model is discussed. We conclude with a set of potential use cases, including dynamic content adaptation and delayed insertion of custom content such as advertisements.

Implementation of polarization‐multiplexed tiled projection integral imaging system

Abstract— A 40‐in. tiled projection integral imaging system has been implemented, adopting a polarization‐multiplexing technique. The system is composed of two full‐high‐definition (HD) projectors, a time‐varying polarizer, a polarization preserving screen, polarization films, a lens array, and a control unit. An elemental image set is projected using two full‐HD projectors to enhance the resolution of the system. The viewing region of the system is increased by using a polarization switching method. The polarization state of the elemental image set is changed by the time‐varying polarizer, and the elemental image set is diffused by the polarization preserving screen. The elemental image set with a preserved polarization state forms a three‐dimensional image with increased viewing angle by the integration of a lens array with polarization films. A 60‐in. tiled projection integral imaging system was also demonstrated using four full‐HD projectors.     

What we have learned and will learn from cell ultrastructure in embedment-free section electron microscopy

The limitations inherent in conventional electron microscopy (EM) using epoxy ultrathin sections for a clear recognition of biological entities having electron densities similar to or lower than that of epoxy resin have led to the development of embedment-free sectioning for EM. Embedment-free section EM is reliably performed using water-soluble polyethylene glycol (PEG) as a transient embedding medium, with subsequent de-embedment of PEG by immersion into water, followed by critical point-drying (CPD) of the embedment-free section. The present author has stressed that this approach clearly discloses structures whose contours and/or appearance are accordingly vague and/or fuzzy in conventional EM, but does not reveal any new structures. Based on embedment-free electron microscopy (PEG-EM), this article presents five major findings regarding strand- or microtrabecular lattices which have been clearly revealed to occur in the cytoplasmic matrix-an impossibility with conventional EM. These are (1) the appearance of lattices of different compactness in various cells and in intracellular domains of a given cell; (2) the faithful reproduction from an albumin solution in vitro of strand-lattices with correspondingly increasing compactness following increasing concentrations; (3) the appearance of more compact lattices from gelated gelatin than from solated gelatin at a given concentration in vitro; (4) the appearance of either greater or less lattice-compactness by hyper- or hypotonic pretreatments of cells; and (5) the appearance of certain intracellular proteins confined to the centripetal demilune-domain of centrifuged ganglion cells which is occupied with strand-lattices of a substantial compactness. From these findings, questions now arise as to the biological significance of the individual strand itself in the microtrabecular lattices in PEG-EM. In addition, it may be that the appearance of strand-lattices in a given biological domain represents the presence of soluble proteins; the lattice-compactness indicates the concentration of soluble proteins in the domain, and the aqueous cytoplasm is equivalent to the aqueous solution. Further, the appearance of two contiguous lattice domains exhibiting differing degrees of compactness in a given cell indicates that cytoplasmic proteins are solated in a domain with less compact lattices, whereas they are gelated in the other domain. These proposed interpretations need to be confirmed by further studies. If confirmed, the control mechanisms of the localization and movement of intracellular organelles could then be understood on the basis not only of information about the cytoskeletons but also of cell ultrastructure-related information on the concentration and sol-gel states of intracellular proteins. In addition, possible interpretations of the significance of strand-lattices in PEG-EM are also applicable to the nucleoplasm, especially extra-heterochromatin (euchromatin) areas. Finally, several potential uses/advantages of PEG-EM in the cell-ultrastructure have also been demonstrated, especially in three-dimensional reconstructions of nonmembranous structures including stereo-viewing using a pair of EM images with appropriate tilting as well as electron microscopic tomography.     

Perceptual Evaluation of Color‐to‐Grayscale Image Conversions

Color images often have to be converted to grayscale for reproduction, artistic purposes, or for subsequent processing. Methods performing the conversion of color images to grayscale aim to retain as much information about the original color image as possible, while simultaneously producing perceptually plausible grayscale results. Recently, many methods of conversion have been proposed, but their performance has not yet been assessed. Therefore, the strengths and weaknesses of color‐to‐grayscale conversions are not known. In this paper, we present the results of two subjective experiments in which a total of 24 color images were converted to grayscale using seven state‐of‐the‐art conversions and evaluated by 119 human subjects using a paired comparison paradigm. We surveyed nearly 20000 human responses and used them to evaluate the accuracy and preference of the color‐to‐grayscale conversions. To the best of our knowledge, the study presented in this paper is the first perceptual evaluation of color‐to‐grayscale conversions. Besides exposing the strengths and weaknesses of the researched methods, the aim of the study is to attain a deeper understanding of the examined field, which can accelerate the progress of color‐to‐grayscale conversion.     

Evolution of spatial light modulator for high‐definition digital holography

Since the late 20th century, there has been rapid development in the display industry. Only 30 years ago, we used big cathode ray tube displays with poor resolution, but now most people use televisions or smartphones with very high‐quality displays. People now want images that are more realistic, beyond the two‐dimensional images that exist on the flat screen, and digital holography—one of the next‐generation displays—is expected to meet that need. The most important parameter that determines the performance of a digital hologram is the pixel pitch. The smaller the pixel pitch, the higher the level of hologram implementation possible. In this study, we fabricated the world‐smallest 3‐μm‐pixel‐pitch holographic backplane based on the spatial light modulator technology. This panel could display images with a viewing angle of more than 10°. Furthermore, a comparative study was conducted on the fabrication processes and the corresponding holographic results from the large to the small pixel‐pitch panels.     

Interaction and visual performance in stereoscopic displays: A review

In this paper, authors systematically selected and reviewed articles related to stereoscopic displays and their advances, with a special focus on perception, interaction, and corresponding challenges. The aim was to understand interaction‐related problems, provide possible explanations, and identify factors that limit their applications. Despite promising advancements, there are still issues that researchers in the field fail to explain precisely. The two major problems in stereoscopic viewing are, compared with the real world, objects are perceived to be smaller than they actually are and there are discomfort and visual syndromes. Furthermore, there is general agreement that humans underestimate their egocentric distance in a virtual environment (VE). Our analysis revealed that in the real world, distance estimation is about 94% accurate, but in VE, it is only about 80% accurate. This problem could reduce the efficacy of different sensory motor‐based applications where interaction is important. Experts from human factors, computing, psychology, and others have studied contributing factors such as types of perception/response method, quality of graphics, associated stereoscopic conditions, experience in virtual reality (VR), and distance signals. This paper discusses the factors requiring further investigation if the VR interaction is to be seamlessly realized. In addition, engineering research directions aiming at improving current interaction performances are recommended.