Aurally aided visual search in three-dimensional space

We conducted an experiment to evaluate the effectiveness of spatial audio displays on target acquisition performance. Participants performed a visual search task with and without the aid of a spatial audio display. Potential target locations ranged between plus and minus 180 degrees in azimuth and from -70 degrees to +90 degrees in elevation. Independent variables included the number of visual distractors present (1, 5, 10, 25, 50) and the spatial audio condition (no spatial audio, free-field spatial audio, virtual spatial audio). Results indicated that both free-field and virtual audio cues engendered a significant decrease in search times. Potential applications of this research include the design of spatial audio displays for aircraft cockpits and ground combat vehicles.     

Effect of geometric field of view on stereoscopic spatial judgments

Within a stereoscopic display the field of view (FOV) was held constant at 13.86 degrees while the geometric field of view (GFOV) was varied across four levels: 0 degrees (parallel), 13.86 degrees (veridical), 50 degrees and 100 degrees. Participants performed a distance-matching task where they adjusted the distance of a standard track from the centre of the display to match the distance of a target track from the same point. The results indicated that while the least error occurred in the veridical GFOV condition, small variations of GFOV away from the veridical have little effect. Large differences between FOV and GFOV (36 degrees and 86 degrees) increased errors markedly. A trend toward better performance in the veridical GFOV condition relative to the parallel GFOV condition suggests that the use of linear perspective information in a stereoscopic display may facilitate more accurate spatial perception. Actual or potential applications of this work include stereoscopic display design in aviation and non-aviation settings.     

Spatial judgments with monoscopic and stereoscopic presentation of perspective displays.

Spatial judgments with monoscopic and stereoscopic presentation of perspective displays were investigated in the present study. The stimulus configuration emulated a visual scene consisting of a volume of airspace above a ground reference plane. Two target symbols were situated at various positions in the space, and observers were instructed to identify the relative depth or altitude of the two symbols. Three viewing orientations (15, 45, or 90 deg elevation angle) were implemented in the perspective projection. In the monoscopic view, depth cues in size, brightness, occlusion, and linear perspective were provided in the format. In the stereoscopic view, binocular disparity was added along the line of sight from the center of projection to reinforce the relative depth in the visual scene. Results revealed that spatial judgments were affected by manipulation of the relative spatial positions of the two target symbols and by the interaction between relative position and viewing orientation. The addition of binocular disparity improved judgments of three-dimensional spatial relationships, and the enhancement was greater when monocular depth cues were less effective and/or ambiguous in recovering the three-dimensional spatial characteristics.     

Cognitive processes in complex tasks: introduction and discussion

This paper points out that the fusional limits of binocular stereoscopic viewing are an important factor, not only determining the reproduction range of stereoscopic images, but also the conformity between the stereoscopic display and stereoscopic vision. Experimental results showed that fusional limits increase in proportion to the field of view angle, and that they are affected not only by the size of the viewing target, but also by the effects that the environment has on the target. These findings explain the differences between binocular vision in real space and binocular vision in a stereoscopic display. Finally, the conditions under which observers arc able to view images of stereoscopic displays without excessive visual strain are discussed.     

Minimum audible movement angle as a function of the azimuth and elevation of the source.

In the future auditory directional cues may enhance situational awareness in cockpits with head-coupled displays. This benefit would depend, however, on the pilot's ability to detect the direction of moving sounds at different locations in space. The present investigation examined this ability. Auditory motion acuity was measured by the minimum audible movement angle (MAMA): the minimum angle of travel required for detection of the direction of sound movement. Five experienced listeners were instructed to indicate the direction of travel of a sound source (broadband noise at 50 dBA) that moved at a velocity of 20 deg/s. Nine azimuth positions were tested at 0 deg elevation. Five elevations were then tested at 0 deg azimuth. Finally two azimuth positions were tested at an elevation of 80 deg. The position of the source did not significantly affect the MAMA for azimuth locations between +40 and -40 deg and elevations below 80 deg. Within this area the MAMA ranged between 1 and 2 deg. Outside this area the MAMA increased to 3 to 10 deg.     

Visual comfort in 2D/3D modes of glasses‐type stereoscopic displays

In this study, we compared visual comfort in 2D/3D modes of the pattern retarder (PR) and shutter glasses (SG) stereoscopic displays by changing viewing factors and image contents. The viewing factors include ambient illuminance/monitor luminance/background luminance and image contents mainly are determined with different disparity limits. The degrees of 2D/3D visual comfort were investigated by using various combinations of ambient illuminance, monitor luminance, background luminance, and disparity limit. A series of psychological experiments were also performed to compare 2D and 3D viewing experiences for the passive PR and active SG stereoscopic displays and to discover more comfortable conditions under various variable combinations. The experiment results show that the various variable combinations affecting visual comfort in the passive PR and active SG stereoscopic displays were significantly different. Finally, we suggest more comfortable conditions of viewing 2D and 3D images for the PR and SG stereoscopic displays.     

Transformations for stereoscopic visual simulation

Stereoscopic display devices are now standard offerings for graphics workstations. These displays find application in medical, scientific, and engineering visualization. Several geometric models can be used to determine the projections for stereoscopic images. In some circumstances, however, the perceived image may be uncomfortable to view, or it may contain undesirable depth distortions. We present a geometric model for stereoscopic viewing that can accurately model most viewing situations. Using this model, the viewer comfortably perceives realistic size and depth relationships among objects in the stereoscopic image. We relate this model to human visual constraints, and develop the geometric transformations required to use this method on graphics workstations.     

Spatial awareness in synthetic vision systems: using spatial and temporal judgments to evaluate texture and field of view

OBJECTIVE: This work introduced judgment-based measures of spatial awareness and used them to evaluate terrain textures and fields of view (FOVs) in synthetic vision system (SVS) displays. BACKGROUND: SVSs are cockpit technologies that depict computer-generated views of terrain surrounding an aircraft. In the assessment of textures and FOVs for SVSs, no studies have directly measured the three levels of spatial awareness with respect to terrain: identification of terrain, its relative spatial location, and its relative temporal location. METHODS: Eighteen pilots made four judgments (relative azimuth angle, distance, height, and abeam time) regarding the location of terrain points displayed in 112 noninteractive 5-s simulations of an SVS head-down display. There were two between-subject variables (texture order and FOV order) and five within-subject variables (texture, FOV, and the terrain point's relative azimuth angle, distance, and height). RESULTS: Texture produced significant main and interaction effects for the magnitude of error in the relative angle, distance, height, and abeam time judgments. FOV interaction effects were significant for the directional magnitude of error in the relative distance, height, and abeam time judgments. CONCLUSION: Spatial awareness was best facilitated by the elevation fishnet (EF), photo fishnet (PF), and photo elevation fishnet (PEF) textures. APPLICATION: This study supports the recommendation that the EF, PF, and PEF textures be further evaluated in future SVS experiments. Additionally, the judgment-based spatial awareness measures used in this experiment could be used to evaluate other display parameters and depth cues in SVSs.     

A geometric comparison of algorithms for fusion control instereoscopic HTDs

This paper concerns stereoscopic virtual reality displays in which the head is tracked and the display is stationary, attached to a desk, tabletop or wall. These are called stereoscopic HTDs (head-tracked displays). Stereoscopic displays render two perspective views of a scene, each of which is seen by one eye of the user. Ideally, the user's natural visual system combines the stereo image pair into a single, 3D perceived image. Unfortunately, users often have difficulty fusing the stereo image pair. Researchers use a number of software techniques to reduce fusion problems. This paper geometrically examines and compares a number of these techniques and reaches the following conclusions: In interactive stereoscopic applications, the combination of view placement, scale, and either false eye separation or α-false eye separation can provide fusion control that is geometrically similar to image shifting and image scaling. However, in stereo HTDs, image shifting and image scaling also generate additional geometric artifacts that are not generated by the other methods. We anecdotally link some of these artifacts to exceeding the perceptual limitations of human vision. While formal perceptual studies are still needed, geometric analysis suggests that image shifting and image scaling may be less appropriate than the other methods for interactive, stereo HTDs     

Light-field head-mounted displays reduce the visual effort: A user study

Head-mounted displays (HMDs) allow the visualization of virtual content and the change of view perspectives in a virtual reality (VR). Besides entertainment purposes, such displays also find application in augmented reality, VR training, or tele-robotic systems. The quality of visual feedback plays a key role for the interaction performance in such setups. In the last years, high-end computers and displays led to the reduction of simulator sickness regarding nausea symptoms, while new visualization technologies are required to further reduce oculomotor and disorientation symptoms. The so-called vergence–accommodation conflict (VAC) in standard stereoscopic displays prevents intense use of 3D displays, so far. The VAC describes the visual mismatch between the projected stereoscopic 3D image and the optical distance to the HMD screen. This conflict can be solved by using displays with correct focal distance. The light-field HMD of this study provides a close-to-continuous depth and high image resolution enabling a highly natural visualization. This paper presents the first user-study on the visual comfort of light-field displays with a close-to-market HMD based on complex interaction tasks. The results provide first evidence that the light-field technology brings clear benefits to the user in terms of physical use comfort, workload, and depth matching performance.     

Characterizing image quality of autostereoscopic displays by using the maximum luminance at each viewing position

A metric of the 3D image quality of autostereoscopic displays based on optical measurements is proposed. This metric uses each view's luminance contrast, which is defined as the ratio of maximum luminance at each viewing position to total luminance at that position. Conventional metrics of the autostereoscopic display based on crosstalk, which uses “wanted” and “unwanted” lights. However, in case of the multiple‐views‐type autostereoscopic displays, it is difficult to distinguish exactly which lights are wanted lights and which are unwanted lights. This paper assumes that the wanted light has a maximum luminance at the good stereoscopic viewing position, and the unwanted light also has a maximum luminance at the worst pseudo‐stereoscopic viewing position. By using the maximum luminance that is indexed by view number of the autostereoscopic display, the proposed method enables characterizing stereoscopic viewing conditions without using wanted/unwanted light. A 3D image quality metric called “stereo luminance contrast,” the average of both eyes' contrast, is proposed. The effectiveness of the proposed metric is confirmed by the results of optical measurement analyses of different types of autostereoscopic displays, such as the two‐view, scan‐backlight, multi‐view, and integral.     

Depth‐map generation for multi‐view autostereoscopic 3‐D displays based on the SIFT algorithm constrained by boundary

Abstract— A depth‐map estimation method, which converts two‐dimensional images into three‐dimensional (3‐D) images for multi‐view autostereoscopic 3‐D displays, is presented. The proposed method utilizes the Scale Invariant Feature Transform (SIFT) matching algorithm to create the sparse depth map. The image boundaries are labeled by using the Sobel operator. A dense depth map is obtained by using the Zero‐Mean Normalized Cross‐Correlation (ZNCC) propagation matching method, which is constrained by the labeled boundaries. Finally, by using depth rendering, the parallax images are generated and synthesized into a stereoscopic image for multi‐view autostereoscopic 3‐D displays. Experimental results show that this scheme achieves good performances on both parallax image generation and multi‐view autostereoscopic 3‐D displays.     

3D Interaction with the Desktop Bat

Many applications now demand interaction with visualizations of 3D scenes and data sets. Current flat 2D displays are limited in their capacity to provide this not only by the display technology but the interaction metaphors and devices used. The Desktop Bat is a device that has 5 degrees of freedom whilst retaining the simplicity of use o fa mouse. To use it for general 3D interaction several metaphors were created for the tasks of navigation and cursor manipulation and a set of experiments were conducted to determine which metaphors were the most efficient in use. Of these metaphors, a velocity control metaphor was the best for navigation and a metaphor that applied rotations and translations relative to the eyepoint coordinate system was best for object control.     

一种V2V多天线几何去极化信道建模

随着极化相关技术的发展,极化调制在V2V（vehicle-to-vehicle)通信系统中的应用越来越广泛。但由于V2V通信环境复杂,极化调制在V2V通信中会产生去极化效应,从而影响通信质量。为了能够识别去极化效应的大小,提出一种新的基于几何散射理论的V2V多天线极化信道模型。该模型可通过已知的多天线配置、极化场辐射模式及散射体的空间分布,建立去极化效应模型,从而将信道的去极化效应由交叉极化鉴别度——XPD(cross polarization discrimination)的值表示,以拓展极化调制在V2V系统中的使用范围,提高传输速率。实验结果表明,XPD的值受到车辆间距离影响存在阈值,并强烈依赖于到达方位角的分布常数,且当到达方位角的值不同时,改变到达仰角的最大值的大小,XPD值的变化呈固定趋势。因此,本文所提出的多天线几何信道模型,成功的将极化引入多天线的V2V通信,可以为极化域通信的进一步研究奠定基础。     

Multiple two-dimensional displays as an alternative to three-dimensional displays in telerobotic tasks

In this study a multiple-view two-dimensional (2D) display was compared with a three-dimensional (3D) monocular display and a 3D stereoscopic display using a simulated telerobotic task. As visual aids, three new types of visual enhancement cues were provided and evaluated for each display type. The results showed that the multiple-view 2D display was superior to the 3D monocular and the 3D stereoscopic display in the absence of the visual enhancement depth cues. When participants were provided with the proposed visual enhancement cues, the stereoscopic and monocular displays became equivalent to the multiple-view 2D display. Actual or potential applications of this study include the design of visual displays for teleoperation systems.     

Measurement of binocular disparity in polarized based stereoscopic display by using digital camera

This work presents an image displacement measurement by using a box pattern and the edge spread function analysis in the polarized based stereoscopic displays. The measurement determines to identify three factors (i.e., box size, image displacement, and spatial frequency response (SFR)) from the box patterns. The polarized based stereoscopic displays might sacrifice pixels for producing 3D images, which might produce errors in the image displacement and then affect the depth perception indirectly. Based on the measurement, the errors can be quantified by using the three factors. Owing to the light leakage distorting the edge spread function to obtain an inferior SFR, exactly how light leakage affects the edge spread function can be resolved on the basis of the SFR results, especially at a frequency (1/display pixel) of 1.9 in the case of the horizontal displacement. Light leakage also induces the error of the box height in even and odd intervals of the vertical displacements more than 2 pixels and 0.5 pixels, respectively. The image displacement measurement provides a simple and comprehensive means of evaluating the optical characteristics, disparity, and sharpness of the stereoscopic displays, via the three factors.     

Front glass thickness requirements for high resolution polarized stereoscopic displays: A simulation platform

The tendency of the display market is towards displays with higher resolutions. Therefore, patterned retarder‐based stereoscopic displays require smaller front glass thickness to maintain good vertical viewing angle and limited crosstalk. To properly design these stereoscopic displays and quantify these requirements, we developed a simulation platform to predict radiance, polarization profile, and crosstalk over viewing angles and over wavelengths. Tunable parameters such as the distance between the pixels and the patterned retarder, and the optical properties of the patterned retarder are included. The simulation platform has been validated by comparing outcomes of simulations with measurements. We predict crosstalk accounting for both the human eye field of view and the diameter of the pupil. We found that to obtain a vertical viewing angle of at least ± 30° and crosstalk of at most 0.11 for a display with a pixel pitch beyond 0.27 mm, the display should include black absorbers, and the thickness of the front glass should be at most 0.5 mm. For higher resolution displays (pixel pitch no more than 0.21 mm), a front glass thickness at most 0.15 mm is required to produce a vertical viewing angle beyond ± 14° and a minimum viewing distance of 0.3 m.     

A low cost, non-individualized surround sound system based upon head related transfer functions: an ergonomics study and prototype development

This paper reports on the types and magnitudes of localization errors of simulated binaural direction cues generated using non-individualized, head-related transfer functions (HRTFs) with different levels of complexity. Four levels of complexity, as represented by the number of non-zero coefficients of the associated HRTF filters (128, 64, 32, 18 non-zero coefficients), were studied. Experiment 1 collected 1728 data runs that were exhaustive combinations of the four levels of complexity, nine simulated directions of sound (no direction (i.e., diotical-mono), 0 degrees , 45 degrees , 90 degrees , 135 degrees , 180 degrees , 225 degrees , 270 degrees , and 315 degrees azimuth angles at 0 degrees elevation), two repetitions, and 24 participants). Binaural cues generated from HRTFs of reduced complexity (from 128 to 18 non-zero coefficients) produced significantly higher localization errors for the directions of 45 degrees , 135 degrees , 225 degrees , and 315 degrees azimuth angles (p<0.01). From the directions of 0 degrees , 90 degrees , and 270 degrees azimuth angles, the cues produced by HRTFs with reduced complexity did not affect the localization error (p>0.2). Surprisingly, cues produced by HRTFs of 128 non-zero coefficients did not have the lowest number of errors. From 45 degrees , 135 degrees , 225 degrees , and 315 degrees , the lowest numbers of errors were obtained from cues produced by HRTFs of 64, 32, 32, and 64 non-zero coefficients, respectively. Based on these findings, a prototype virtual headphone-based surround-sound (VHSS) system was developed. A double-blind usability experiment with 32 participants indicated that the prototype VHSS system received significantly better surround-sound ratings than did a Dolby stereo system (p<0.02). This paper reports results from an original ergonomics study and the application of these results to the design of a consumer product.     

Siberian silkmoth outbreak pattern analysis based on SPOT VEGETATION data

The spatial pattern of Siberian silkmoth outbreak in south Siberian mountains was analysed based on SPOT VEGETATION data. A digital elevation model (DEM) was also used to relate outbreak area dynamics with topographic elements (elevation, azimuth and slope steepness). To avoid bias of spatial pattern data, areas with a given damage category and with given azimuth, slope steepness and elevation were referenced to the areas with similar parameters within the entire study area. The outbreak began between the elevations of ～430–480 m and on south‐west slopes with steepness <5°; these conditions appear to be the most favourable pest habitat. As the pest searched for food it moved up and down slope, resulting in an elevation distribution split within a range of ～390–540 m and slope steepness up to 15°. In the final phase the azimuth distribution of damaged stands became even, showing that pests at this phase settle in non‐optimal habitat. The final outbreak area was ～20 000 ha, which is in good agreement with on‐ground data. The correlation between the initial phase of infestation and topographic features can be used to prioritize pest monitoring. Data obtained show that the SPOT VEGETATION sensor is applicable for monitoring taiga landscapes vulnerable to Siberian silkmoth outbreaks.     

近地炸点声定位算法研究

针对四元十字阵被动声定位算法存在定位精度受目标方位角影响的问题,提出基于时间差技术的五元十字阵算法;研究了五元十字阵阵元间的几何关系与参数的计算,利用球面坐标法及最小二乘法推导了目标定位计算式,进行了系统误差分析;实验结果表明,该算法提高了炸点的测距与测向精度,改善了目标方位角对弹丸炸点的定位精度的影响;与四元十字阵算法相比,五元十字阵算法在距离、方位角和俯仰角的误差分别是1.33m、0.0003°和0.44°。