增强现实系统显示技术探讨

增强现实系统的显示技术,是增强现实技术研究的重要部分。在增强现实系统中,使用透视式头盔显示器来实现对现实的增强。该文介绍了增强现实显示常用的两种透视式头盔显示器,在技术、心理因素方面对它们进行了比较,并且给出了一些新的思路和方法。     

光学透视头盔显示器标定技术

光学透视头盔显示器(OSTHMD)标定是增强现实技术研究中一个具有挑战性的关键技术问题. 研究了OSTHMD标定的几种常见技术及其优缺点, 详细论述了当前最常用的OSTHMD标定法: SPAAM法, 同时提出了一种基于图像的快速标定OSTHMD的方法, 从算法复杂度方面对两种标定法进行了对比, 并采用用户自行评估法进行评估, 认为基于图像的快速标定OSTHMD的方法更为快速精准.     

光学透射头盔显示器标定综述

光学透射头盔显示器(OSTHMD)标定是增强现实技术研究中一个具有挑战性的关键技术问题.文中详细阐述了OSTHMD的标定技术,包括标定要求、标定计算模型、标定方法、标定评估、发展趋势和应用前景等,重点介绍了比较实用的基于单点主动对准法和基于图像的标定方法.     

光学透视式增强现实显示系统虚实遮挡问题研究

鉴于增强现实系统中,虚拟物体与真实环境之间是否具有正确的遮挡关系会影响到虚实融合能否取得逼真的效果,为此根据一种新型光学透视式头盔显示器,提出了一种利用OpenGL来绘制虚拟网格遮挡平面,以便使虚拟物体呈现被裁剪的形态,而与真实物体融合后可呈现出实挡虚效果的方法。这种方法,在程序实现方面相对较为容易,且计算量较低,因而更适宜实时系统的使用。通过实验可以看出,采用OpenGL对虚拟物体与真实场景的深度数组进行逐点深度比较来绘制遮挡平面的方法是可行的。     

现代空战中的头盔显示器及其关键技术

首先概述了头盔显示器的基本概念，结构、组成和分类，头盔显示器的主要任务、工作过程以及研制现状和典型产品，之后根据现代空战的特点分析了头盔显示器在现代空战中主要作用，最后对头盔显示器的关键技术和发展趋势作了简要分析。     

头盔显示器发展综述

随着虚拟现实与增强现实技术的快速发展,近年来越来越多的虚拟现实与增强现实相关应用走入大众视野.在众多显示设备中,头盔显示器以其高沉浸感、实时交互性及其广阔的应用领域在虚拟现实与增强现实技术中占据重要地位.文中介绍了头盔显示器光学系统成像原理;分析总结了从不同的技术角度解决的传统头盔显示器体积与质量大、调焦与辐辏不匹配等问题的3种新型头盔显示器,包括自由曲面头盔显示器、波导型头盔显示器和真实立体感头盔显示器,阐述了用户佩戴头盔显示器的视疲劳主观和客观评测方法;最后对头盔显示器的未来发展趋势进行了展望.     

基于视觉增强现实系统的设计与实现

针对目前增强现实领域尚少有人涉足的运动跟踪注册问题,提出了采用四个彩色标志点的光流场估计运动参数,结合刚体的运动特性以及投影透射模型确定运动物体与摄像机间相对位姿的算法。并把该算法用于以光学透射式头盔显示器为主的增强现实系统中。该系统结构简单、轻便、实用性强、易于实现。一般情况下只需四个平面标志物就可实现运动物体的三维跟踪注册;工作范围大,甚至可以应用到室外的增强现实系统中;数值求解过程是线性过程,误差小,可以满足增强现实系统高精度三维注册的要求。     

全数字标定法在称量显示器中的应用

一、概述在现代称量显示器中,采用全数字标定法(即软件式标定法)与传统模拟硬件标定法和较近期采用的模拟数字混合式的标定法相比,不仅大大简化了标定步骤,而且节省了元器件(如电位器和拨码开关等),从而减少了人为因素和元器件质量因素的影响,增加了系统的可靠性,提高了系统精确度。为此,我们在称重显示器的设计中采用了全数字标定法(FDC),使称重显示器构造简单,硬件设计成本下降,操作灵活方便。二、全数字标定法的原理和实现方法 1.设计原理一般来说,在各种电子秤的安装调试过程中,零点和最大称重点的校准,必须用标准砝码(或经     

基于全景成像的增强现实系统

建立完整的基于全景成像的增强现实系统,将全景图像采集系统放置在场景中采集真实图像,佩戴头盔显示器和头部跟踪器的观察者可以在其他地方观看在真实图像中添加了虚拟信息的增强图像,解决图像采集装置与头盔显示器分离时增强现实系统的技术难点。实验结果表明,全景成像方法对于亮度差异较大的图像有较好的拼接效果,适用于室外复杂环境的图像拼接,全景图像的局部增强显示效果良好。     

一种基于视沉的增强现实三维注册算法

为了提高增强现实系统三维注册的精度和效率，提出了一种基于计算机视觉的增强现实三维注射算法，并已将其用于采用透射式头盔显示器的增强现实系统中，该算法有如下特点：（1）构架简单，实用性强，一般情况下只需4个平面标志物就可实现三维注册；（2）工作范围大，甚至可以应用到室外的增强现实系统中；（30数值求解过程最线性过程，误差小，可以满足增强现实系统高精度三维注册的要求，另外，应用这种算法所需要作的图象处理计算量很小，其典型系统包括一个彩色CCD和几个不同颜色的标志点，由于很容易获得标志点的对应像面位置，而且不需要计算图象对，因此实时性好，是一般图形工作站和PC机上的增强现实系统进行实时注册的算法基础。     

仿射变换虚实配准的空间信息增强表达

伴随着移动GIS和可穿戴计算的出现,GIS作业空间被拓展到户外,户外增强现实空间信息表达致力于将虚拟空间信息叠加到真实地理场景上,增强、拓展用户对地理场景的认知。为了有效地降低空间信息增强表达的虚实配准误差,汲取计算机视觉中的算法思想,提出通过建立全局仿射坐标系,解算虚拟物体到真实场景图像的投影坐标,找到获取像素相对深度参数的方法,进而避开相机定标这个复杂过程,最终为户外增强现实系统提供位置相关的信息源,也为空间信息可视化表达提供了新界面。     

Image retrieval based on incremental subspace learning

Many problems in information processing involve some form of dimensionality reduction, such as face recognition, image/text retrieval, data visualization, etc. The typical linear dimensionality reduction algorithms include principal component analysis (PCA), random projection, locality-preserving projection (LPP), etc. These techniques are generally unsupervised which allows them to model data in the absence of labels or categories. In this paper, we propose a semi-supervised subspace learning algorithm for image retrieval. In relevance feedback-driven image retrieval system, the user-provided information can be used to better describe the intrinsic semantic relationships between images. Our algorithm is fundamentally based on LPP which can incorporate user's relevance feedbacks. As the user's feedbacks are accumulated, we can ultimately obtain a semantic subspace in which different semantic classes can be best separated and the retrieval performance can be enhanced. We compared our proposed algorithm to PCA and the standard LPP. Experimental results on a large collection of images have shown the effectiveness and efficiency of our proposed algorithm.     

基于短焦相机的激光笔光点坐标映射方法

在现今的教学、会议以及演讲等众多领域上,投影技术得到了越来越广泛的使用。而大部分投影交互过程中主要使用翻页激光笔等,这种方式交互操作单调,并且不能方便地获取鼠标坐标。针对这些问题,同时考虑到短焦投影技术的发展趋势,提出了一种基于短焦相机的激光笔光点坐标映射方法,将激光点坐标准确地从投影画面映射到操作系统的鼠标坐标,为基于激光笔的短焦投影交互提供了支持。该方法考虑到短焦相机与短焦投影的硬件融合,使用普通分辨率的短焦摄像头采集投影图像,从采集的图像中获取激光点。考虑到短焦镜头畸变大的特点,设计了二次标定的过程,利用第二次标定弥补第一次标定留下的误差,从而确保了坐标映射的精度。提出的方法在基于激光笔的投影交互系统中具有很好的应用前景。     

Projection center calibration by motion

Camera calibration is the first step of three-dimensional machine vision. A fundamental parameter to be calibrated is the position of the camera projection center with respect to the image plane. This paper presents a method for the computation of the projection center position using images of a translating rigid object, taken by the camera itself.

Many works have been proposed in literature to solve the calibration problem, but this method has several desirable features. The projection center position is computed directly, independently of all other camera parameters. The dimensions and position of the object used for calibration can be completely unknown.

This method is based on a geometric relation between the projection center and the focus of expansion. The use of this property enables the problem to be split into two parts. First a suitable number of focuses of expansion are computed from the images of the translating object. Then the focuses of expansion are taken as landmarks to build a spatial back triangulation problem, the solution of which gives the projection center position.     

多投影面沉浸式虚拟环境系统的颜色校正

提出一种颜色校正的函数逼近优化模型来解决多投影面沉浸式虚拟环境系统的颜色校正问题。该颜色校正模型,采用数码相机作为颜色反馈的测量仪器,获得一个基准投影面的亮度和色度转换函数;为其他投影面分别寻找一个亮度修正函数和色度修正函数,使得各投影面与基准投影面的亮度和色度转换函数之间的L2距离最小,进而根据各修正函数来补偿各投影机的输入响应差别以达到它们之间的颜色一致。给出了逼近校正方法的算法及其程序实现,通过一个三通道的试验系统,证明了此方法对解决多投影面沉浸式虚拟环境系统颜色校正问题的有效性。     

The auto‐geometric correction of multi‐projector for cylindrical surface using Bézier patches

Geometric calibration to projection images is an indispensable operation for projection‐based spatial display. In this paper, we propose a new method for correcting images generated in a computer onto a cylindrical surface accurately, which can project a high‐resolution projection image with pixels matching avoiding too much manual operation. Images waiting to be projected are pre‐warped according to the rough correspondence between projectors and physical surface. To solve the errors resulting from unexpected pixel shifts in overlap projection area, we fit the Bézier interpolation to the images and apply the optimization theory with added constraints to correct the projection image accurately. This optimization process, by taking the pixels with specific significance on the images as the basis of calculation, avoids the traditional ways of translating the control points of the Bézier surface directly. The final results achieve a completely accurate projection picture even if the projection surface shape is inaccurate and irregular. We present the details of the proposed accurate calibration algorithm and illustrate our method, which, with its scalability, can achieve perfect projection efficiently and accurately with experiments.     

“数据手套”校准误差的分析与消除

随着虚拟现实技术VR（VirtualReality）的推广和应用，数据手套以其轻巧、方便、灵活和包络面大而成为VR的主要输入／输出工具，然而，由于结构上的原因，”手套校准”容易产生累积性误差。在极端情况下，累积性误差将直接影响应用的精度和效果。如何检测、消除累积性误差是设计数据手套的关键。本文以应用最广泛的数据手套为基础，从结构上分析了核准误差产生的原因，给出了手套校准算法和两种消除误差的实际方案。     

Recent Advances in Projection Mapping Algorithms,Hardware and Applications

This State‐of‐the‐Art‐Report covers the recent advances in research fields related to projection mapping applications. We summarize the novel enhancements to simplify the 3D geometric calibration task, which can now be reliably carried out either interactively or automatically using self‐calibration methods. Furthermore, improvements regarding radiometric calibration and compensation as well as the neutralization of global illumination effects are summarized. We then introduce computational display approaches to overcome technical limitations of current projection hardware in terms of dynamic range, refresh rate, spatial resolution, depth‐of‐field, view dependency, and color space. These technologies contribute towards creating new application domains related to projection‐based spatial augmentations. We summarize these emerging applications, and discuss new directions for industries.     

Natural perspective projections for head-mounted displays

The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.     

A sorting program for orientation analysis of data on a sphere

A program is introduced that sorts data sets in lower hemisphere projection according to domains that can be defined at run time. The package consists of two programs which overlap in their use of subroutines. The first program is adapted for reading universal stage data which are translated into spherical coordinates. It can be adapted easily for other types of data that plot on a sphere. The second one does the sorting and provides three sorting nets at the user's choice. The program is useful especially for detailed microfabric work, for example axial distribution analysis.