With occlusion by proximal surfaces,even without self-occlusion,continuously appearing and disappearing parts bring volume perception from motion

Volume perception, that is, perception of a partially enclosed space filled with a medium, can be assessed not only from binocular viewing but also from motion. It was demonstrated that appearing and disappearing parts, which were generated by self-occlusion, play an essential role in volume perception from motion. In this study, we investigated volume perception in partially visible cylindrical and polyhedral objects occluded by proximal surfaces, and found that the ADPs bring volume perception not only in the cylindrical object but also in the polyhedral object, which appears to correspond to BURs for volume perception in binocular viewing.     

Four-dimensional flash trajectory imaging using time-delay-modulated range-gated viewing

We present a four-dimensional flash trajectory imaging method to image object trajectories over time in three-dimensional space. In the method, time-delay-modulated range-gated viewing with multiple exposures is presented so that the time evolution of object trajectories free from background interference is directly given without complicated image processing and the motion parameters of objects can be estimated. The method is demonstrated by a ball oscillating as a pendulum.     

Monocular viewing prolongs reversal interval of perceptual rival figure

The authors examined whether the perceptual reversal rate changes under monocular versus binocular viewing conditions. Our results suggest that the perceptual reversal interval increases during monocular viewing. The ratio of the reversal rate (1/interval) for the two viewing conditions (binocular/monocular) was 1.28 over a wide range of pattern luminance levels. The quoted ratio was 1.40 when the luminance was high. Such a ratio parallels the value of a well-known binocular summation index $(\sqrt 2 )$ , which was derived from the signal detection theory. The binocular summation index shows that the strength of an input signal is enhanced by binocular viewing. However, how the binocular summation shortens the perceptual reversal interval is unclear. This issue can be resolved if the perceptual reversal is derived by integrating the strength of an unconscious image signal. Thus, we discussed the mechanism of perceptual switch by associating two classical, well-studied phenomena, binocular summation and perceptual switch.     

Color Constancy in a Photograph Perceived as a Three-Dimensional Space

It is known that color constancy does not hold in a photograph. This could be because the photograph is recognized as a two-dimensional paper. Based on the concept of the recognized visual space of illumination (RVSI), it is predicted that color constancy holds in the photograph if it is perceived as a 3-D scene. We examined whether the color constancy held under a special viewing condition. A photograph of a room under incandescent illumination was shown under daylight illumination. We tested the neutral color perception of a stimulus on the photograph both with and without a dimension-up viewing box showing the photograph alone monocularly. The results showed good color constancy when a subject observed the photograph with the viewing box. It was also shown that the degree of color constancy decreased for a jumbled photograph without 3-D information. Our results suggest that the recognition of a space and illumination are important in color perception.     

基于立体视觉的空间运动分析

利用摄影测量方法和计算机视觉技术得出了一套完整的、由双目立体序列图像确定场景中目标运动信息的方法与步骤。讨论了双目立体视觉系统的在任检校,相关系数和松弛法相结合基于点特征的物体运动、立体匹配,运动前后三维特征点的对应,以及利用能减少待定变量、降低计算复杂性、提高算法精确性的反对称矩阵分解算法求解运动参数(R和T)等问题。给出了从一组真实图像中获取目标运动参数的计算结果。     

Neon Color Spreading Promoted by Motion Information

We conducted experiments to investigate the effects of head-motion and object-motion to produce a perception of neon color spreading. Our experimental results indicated that a two-dimensional motion of yellow patches promoted the color spreading. A horizontal head-motion with motion parallax and three-dimensional pictorial depth information together with changing the viewing point stimulated the color spreading even, more than the two-dimensional motion. Thus, motion signals appear to offer useful information for the formation of a subjective contour and/or to activate the filling-in effect needed to generate neon color spreading. We also tested whether there was a difference between the effects of vertical and horizontal motion parallaxes for neon color spreading and found that there was none. This suggests that vertical head motion provides information in depth and surface perception equivalent to horizontal head motion.     

3-D distortion of observed images reconstructed from a cylindrical holographic stereogram. (1) laser light reconstruction type

In the case that the image reconstructed from a cylindrical holographic stereogram with laser light reconstruction (LCHS) is observed by binocular vision, the 3-D distortion characteristics of the image are studied. Using an object of a distinctive construction, some examples are calculated and experimental results are also shown, and the optimum condition to synthesize the LCHS is given.     

A study on approaching motion perception in periphery with binocular viewing: Visibility is increased in the absence of one eye’s information

The visibility of an approaching target on the horizontal plane in peripheral vision with binocular viewing was studied. It was found that the perceptual performance for the target moving toward the middle point of the two eyes was remarkably worse; under this circumstance it has rather high performance in the absence of one eye’s target information with occlusion or falling on the blind spot. These facts imply that the conventional change disparity mechanism does not work in the peripheral visual field; while some simple combinations of the monocular information of two eyes, such as the sum of two eyes’ image motion with sign, can be used to detect an approaching motion in the periphery.     

反射式多路投影立体显示系统的研究

设计了一种反射式多路投影立体显示系统,并介绍了该系统的成像原理及特性。系统将12幅视差图同时投影在柱面栅上,观察者仅凭肉眼就可看到具有双眼视差和运动视差的立体图像。系统成像视域较大,可以同时供多人观看。     

非相干成像双目视觉系统的误差分析

影响双目视觉系统测量精度的因素很多,目前系统结构参数对测量精度的影响主要有光轴与基线的夹角、基线距离、水平视角、物距以及透镜焦距等。由于孔径尺寸直接影响成像分辨率,是决定双目视觉测量精度的核心因素,因此依据非相干成像理论,对双目成像过程进行仿真和实验,采用加速鲁棒特征算法对所成的图像对进行特征提取与匹配,获取其视差值,并且计算其视差均方根误差来表征系统误差。研究结果表明,系统误差随着透镜孔径大小的增大而减小,并且趋于饱和。该研究可以为双目系统设计过程中系统参数和孔径尺寸的选取提供理论和实验依据。     

On properties of vacuum axially symmetric spacetime of gravitomagnetic monopole in cylindrical coordinates

We investigate general relativistic effects associated with the gravitomagnetic monopole moment of a gravitational source through the analysis of the motion of test particles and electromagnetic fields distribution in the spacetime around the nonrotating cylindrical NUT source. We consider the circular motion of test particles in the NUT spacetime, their characteristics and the dependence of the effective potential on the radial coordinate for the different values of the NUT parameter and orbital momentum of test particles. It is shown that the bounds of stability for circular orbits are displaced toward the event horizon with the growth of the monopole moment of the NUT object. In addition, we obtain exact analytical solutions of the Maxwell equations for magnetized and charged cylindrical NUT stars.     

One-beam recording in a LiNbO3 crystal

We propose a new way to record images in a photorefractive LiNbO3 crystal. This method involves only a single object light without any reference light. We believe that the recording is attained by fanning holograms that result from interference between the object light and its scattered light. Although volume gratings are involved, the recorded pattern can be viewed not only with a laser light beam that is incident over a certain angular range but also with white light.     

Stereoscopic Full-Color Light Emitting Diode Display Using Parallax Barrier for Different Interpupillary Distances

The viewing areas of stereoscopic full-color light emitting diode (LED) displays using parallax barriers are investigated for viewing by observers with different interpupillary distances. We have developed stereoscopic full-color LED displays using three types of parallax barriers for different interpupillary distances. Experiments on distance perception of stereoscopic targets have been conducted with the stereoscopic LED displays using parallax barriers, as well as a stereoscopic LED display using polarizing eyewear. It was shown that enlargement of the viewing area allows several viewers with different interpupillary distances to view a stereoscopic image. It is suggested that parallax barriers designed for narrower interpupillary distances than the viewer’s own provide a viewer with stereoscopic perception.     

Persistence and phase synchronisation properties of fixational eye movements

When we fixate our gaze on a stable object, our eyes move continuously with extremely small involuntary and autonomic movements, that even we are unaware of during their occurrence. One of the roles of these fixational eye movements is to prevent the adaptation of the visual system to continuous illumination and inhibit fading of the image. These random, small movements are restricted at long time scales so as to keep the target at the centre of the field of view. In addition, the synchronisation properties between both eyes are related to binocular coordination in order to provide stereopsis. We investigated the roles of different time scale behaviours, especially how they are expressed in the different spatial directions (vertical versus horizontal). We also tested the synchronisation between both eyes. Results show different scaling behaviour between horizontal and vertical movements. When the small ballistic movements, i.e., microsaccades, are removed, the scaling behaviour in both axes becomes similar. Our findings suggest that microsaccades enhance the persistence at short time scales mostly in the horizontal component and much less in the vertical component. We also applied the phase synchronisation decay method to study the synchronisation between six combinations of binocular fixational eye movement components. We found that the vertical-vertical components of right and left eyes are significantly more synchronised than the horizontal-horizontal components. These differences may be due to the need for continuously moving the eyes in the horizontal plane in order to match the stereoscopic image for different viewing distances.     

Estimation of curl in paper using a combination of shape measurement and least-squares modelling

Curl is a quality problem that makes paper less suitable for printing. A paper sheet that has structural variations in its thickness such as gradients of fibre orientation, density and filler content, will curl and hence assume a cylindrical shape when its humidity content is changed. We propose a method to measure curl that can be used for automated analysis of the paper quality. The shape of the curled paper is measured using a stereoscopic camera system, which is capable of viewing a random pattern that is projected onto the specimen. The shape of the object is found by calculating the perspective difference in the camera set-up using digital image correlation. The quality parameters that are searched for are the magnitude of curl, which is defined as the inverse of the radius of curvature and the orientation of the curled paper. These parameters are estimated by performing a least-squares fit of a cylindrical shape to the three-dimensional measurement data. The least-squares model is non-linear and an iterative technique based on the Gauss–Newton algorithm is used.     

Perception of heading speed from radial flow depends on visual field

We investigated the effects that the visual field has on the perception of heading speed. The stimulus was a radial flow pattern simulating a translational motion through a cylindrical tunnel. Observers evaluated the perception of heading speed by using a temporal two-alternative forced choice (2AFC) staircase method. In the first experiment, we manipulated the stimulus area by cutting the visual field along the longitudinal direction. The results showed that the perceived heading speed increases with the stimulus area. In the second experiment, we manipulated both the stimulus area and the eccentricity by cutting the visual field along the longitudinal direction. The results showed that the perception of heading speed increases when the stimulus occupies a large portion of the peripheral visual field. These findings suggest that the effect of eccentricity is a consequence of an incorrect translation of two-dimensional visual information into three-dimensional scaling.     

Three-dimensional display with a long viewing distance by use of integral photography

We developed a technique of three-dimensional (3-D) display for distant viewing of a 3-D image without the need for special glasses. The photobased integral photography (IP) method allows precise 3-D images to be displayed at long viewing distances without any influence from deviated or distorted lenses in a lens array. We calculate elemental images from a referential viewing area for each lens and project the corresponding result images to photographic film through each lens. We succeed in creating an image display that appears to have three dimensionality even when viewed from a distance, with an image depth of 5.7 m or more in front of the display and 3.5 m or more behind the display. To the best of our knowledge, the long-distance IP display presented here is technically unique because it is the first report of generation of an image with such a long viewing distance.     

Strain field measurements with dual-beam digital speckle photography

A non-contact strain field measurement technique called dual-beam digital speckle photography is presented. The system facilitates strain measurements in rough environments and at elevated temperatures and can be used on materials where instrumentation of standard strain gauges are difficult. The system uses two symmetrically oriented laser illumination beams and an imaging system oriented normal to the object surface. The laser speckle field for each illumination beam is recorded simultaneously before and after object deformation. From these data sets it is possible to extract one strain component, e.g. _xx, without the need of numerical differentiation. It is shown that the most important criteria is normal viewing but also that deviation from perfect symmetry in the illumination will affect the results. A dynamic strain field, acquired at 15 Hz, illustrates the system performance. The effect of oblique viewing and unstable lasers are also shown.     

The perception of entropy in rapidly moving sparse dot arrays: a nonlinear dynamic perspective

In visual fields composed of dots spatially randomly distributed but moving rigidly, the percept of coherent motion is lost once D_max is exceeded, resulting in an incoherent, random percept. We have investigated this transition both from a psychophysics perspective and in the development of a dynamic model of the visual system based on a spatially coupled array of nonlinear damped mass-springs cells. We present results of experiments using rigidly moving arrays of dots of different levels of sparseness and differing displacement magnitudes. Results show that the perception of randomness can be reliably judged and displays a transition from coherent to non-coherent motion as the motion amplitude is increased. Using standard psychophysical just noticeable difference (JND) judgements, we noted that the threshold JND was a function of displacement magnitude and sparseness and could not be explained by extant spatiotemporal filtering models. Our model qualitatively explains the important features of the data, reproducing the experimental D_max and entropy perception effects with increased stimuli motion amplitude at different spatial sparseness levels. We have then performed some numerical simulations of the model when the masses in the array are randomly distributed. Results show that sparseness plays different role if close or far from D_max in terms of motion coherence discrimination.     

圆柱型层析计算全息技术研究

研究了三维物体圆柱型层析计算全息技术:分别将不同深度三维物体的圆柱截面与对应的点扩展函数进行卷积后叠加获得位于全息面的物光场分布,并与参考光干涉获得计算全息图,再现该全息图可对原物体实现360°观测。首先建立三维物体圆柱型层析计算全息模型,推导系统点扩展函数与不同方向采样间隔所需满足的条件;然后通过理论与实验分析了物体不同圆柱截面半径、波长对空间频率和系统传递函数的影响,采用峰值信噪比和均方误差来评价再现图质量;最后对三维地球模型采用圆柱型层析计算全息编码,再现了不同观察角度与深度的信息。仿真结果表明,该方法对于一般三维物体360°全视场显示具有较高的应用价值。