Stereo Vision (Computer Vision)

Interocular velocity difference contributes to stereomotion speed perception

by Kevin Brooks

Brooks, K. R. (2002a). Interocular velocity difference contributes to stereomotion speed perception. Journal of Vision, 2, 218-231, http://journalofvision.org/2/3/2/, doi:10.1167/2.3.2.

Two experiments are presented assessing the contributions of the rate of change of disparity (CD) and interocular... more Two experiments are presented assessing the contributions of the rate of change of disparity (CD) and interocular velocity difference (IOVD) cues to stereomotion speed perception. Using a two-interval forced-choice paradigm, the perceived speed of directly approaching and receding stereomotion and of monocular lateral motion in random dot stereogram (RDS) targets was measured. Prior adaptation using dysjunctively moving random dot stimuli induced a velocity aftereffect (VAE). The degree of interocular correlation in the adapting images was manipulated to assess the effectiveness of each cue. While correlated adaptation involved a conventional RDS stimulus, containing both IOVD and CD cues, uncorrelated adaptation featured an independent dot array in each monocular half-image, and hence lacked a coherent disparity signal. Adaptation produced a larger VAE for stereomotion than for monocular lateral motion, implying effects at neural sites beyond that of binocular combination. For motion passing through the horopter, correlated and uncorrelated adaptation stimuli produced equivalent stereomotion VAEs. The possibility that these results were due to the adaptation of a CD mechanism through random matches in the uncorrelated stimulus was discounted in a control experiment. Here both simultaneous and sequential adaptation of left and right eyes produced similar stereomotion VAEs. Motion at uncrossed disparities was also affected by both correlated and uncorrelated adaptation stimuli, but showed a significantly greater VAE in response to the former. These results show that (1) there are two separate, specialised mechanisms for encoding stereomotion: one through IOVD, the other through CD; (2) the IOVD cue dominates the perception of stereomotion speed for stimuli passing through the horopter; and (3) at a disparity pedestal both the IOVD and the CD cues have a significant influence.

Stereomotion speed perception is contrast dependent

by Kevin Brooks

Brooks, K. (2001). Stereomotion speed perception is contrast dependent. Perception, 30, 725-731.

The effect of contrast on the perception of stimulus speed for stereomotion and monocular lateral motion was... more The effect of contrast on the perception of stimulus speed for stereomotion and monocular lateral motion was investigated for successive matches in random-dot stimuli. The familiar `Thompson effect' - that a reduction in contrast leads to a reduction in perceived speed - was found in similar proportions for both binocular images moving in depth, and for monocular images translating laterally. This result is consistent with the idea that the monocular motion system has a significant input to the stereomotion system, and dominates the speed percept for approaching motion.

Stereomotion suppression and the perception of speed: Accuracy and precision as a function of 3D trajectory

by Kevin Brooks

Brooks, K. R. & Stone L. S. (2006). Stereomotion suppression and the perception of speed: accuracy and precision as a function of 3D trajectory. Journal of Vision, 6, 1214-1223, http://journalofvision.org/6/11/6, doi:10.1167/6.11.6

The precision and accuracy of speed discrimination performance for stereomotion stimuli were assessed for several... more The precision and accuracy of speed discrimination performance for stereomotion stimuli were assessed for several receding 3D trajectories confined to the horizontal meridian. It has previously been demonstrated in a variety of tasks that detection thresholds are substantially higher when subjects observe a stereomotion stimulus than when simply viewing one of its component monocular half-imagesVa phenomenon known as stereomotion suppression (C. W. Tyler, 1971). Using monocularly visible motion in depth targets, we found mean speed discrimination thresholds to be higher for stereomotion,
compared with monocular lateral speed discrimination thresholds for equivalent stimuli, demonstrating a disadvantage for binocular viewing in the case of speed discrimination as well. Furthermore, speed discrimination thresholds for motion in depth were not systematically affected by trajectory angle; hence, the disadvantage of binocular viewing persists even when there are concurrent changes in binocular visual direction. Lastly, there was a tendency for oblique trajectories of stereomotion to be perceived as faster than equally rapid motion receding directly away from the subject along the midline. Our data, in addition to earlier stereomotion suppression observations, are consistent with a stereomotion system that takes a noisy, weighted difference of the stimulus velocities in the two eyes to compute motion in depth.

Multi–modal matching applied to stereo

by Nicolas Pugeault

Surface Reconstruction from Aerial Images in Dense Urban Areas

by Ugur Murat Leloglu

Maxim Fradkin, Michel Roux, Henri Maître, Uğur M. Leloğlu, Surface Reconstruction from Aerial Images in Dense Urban Areas, IEEE Conference on Computer Vision and Pattern Recognition (CVPR’99), Fort Collins, Colorado, USA, June 23-25, 1999.

Dense Stereo Correspondence Using Elastic Nets

by Ugur Murat Leloglu

Uğur M. Leloğlu, Dense Stereo Correspondence Using Elastic Nets, Second Turkish Artificial Intelligence and Artificial Neural Networks Symposium (TAIANN’93), Boğaziçi University, İstanbul, Turkey, June 24-25, 1993.

Dense Urban DEM with Three or More High-Resolution Aerial Images

by Ugur Murat Leloglu

Uğur M. Leloğlu, Michel Roux, Henri Maître, Dense Urban DEM with Three or More High-Resolution Aerial Images, ISPRS Commission IV Symposium: GIS-Between Visions and Applications, Stuttgart, Germany, September 7-10, 1998.

Multi-Image Region Growing for Integrating Disparity Maps

by Ugur Murat Leloglu

Uğur M. Leloğlu, Uğur Halıcı, Multi-Image Region Growing for Integrating Disparity Maps, 8th International Conference on Computer Analysis of Images and Patterns (CAIP’99), Ljubljana, Slovenia, September 1-3 1999.

The SmartVision Navigation Prototype for Blind Users

by Hugo Fernandes

Authors: du Buf J.M.H., Barroso J., Rodrigues J.M.F., Paredes H., Farrajota M., Fernandes H., José J.T.P.N., Teixeira V., Saleiro M.

The goal of the Portuguese project "SmartVision: active vision for the blind" is to develop a small,... more The goal of the Portuguese project "SmartVision: active vision for the blind" is to develop a small, portable and cheap yet intelligent and reliable system for assisting the blind and visually impaired while navigating autonomously, both in- and outdoor. In this article we present an overview of the prototype, design issues, and its different modules which integrate GPS and Wi-Fi localisation with a GIS, passive RFID tags, and computer vision. The prototype addresses global navigation for going to some destiny, by following known landmarks stored in the GIS in combination with path optimisation, and local navigation with path and obstacle detection just beyond the reach of the white cane. The system does not replace the white cane but complements it, in order to alert the user to looming hazards. In addition, computer vision is used to identify objects on shelves, for example in a pantry or refrigerator. The user-friendly interface consists of a four-button hand-held box, a vibration actuator in the handle of the white cane, and speech synthesis. In the near future, passive RFID tags will be complemented by active tags for marking navigation landmarks, and speech recognition may complement or substitute the vibration actuator.

Fiducials marks detection to assist visually impaired people navigation

by Hugo Fernandes

Authors: Costa. P, Fernandes H., Vasconcelos V., Coelho P., Barroso J., Hadjileontiadis L.

Assistive technology enables people to achieve independence in the accomplishment of their daily tasks and enhance... more Assistive technology enables people to achieve independence in the accomplishment of their daily tasks and enhance their quality of life. Visual information is the basis for most navigational tasks, so visually impaired individuals are at disadvantage due to the lack of information or given unsufficient information about their surrounding environment. With the recent advances in inclusive technology it is possible to extend the support given to people with visual disabilities during their mobility. In this context we propose and describe the SmartVision project, whose global objective is to assist visually impaired people in their navigation through unknown indoor and outdoor environments. This paper is
focused mainly on the Computer Vision module of the SmartVision prototype, were we propose a new algorithm to recognise fiducials marks suitably placed on sidewalks, revealing to be a promising solution.

Fiducials Marks detection to Assist Visually Impaired people Navigate

by Hugo Fernandes

Authors: Paulo Costa, Hugo Fernandes, João Barroso, Paulo Coelho, and Leontios J. Hadjileontiadis

Assistive technology enables people to achieve independence in the accomplishment of their daily tasks and enhance... more Assistive technology enables people to achieve independence in the accomplishment of their daily tasks and enhance their quality of life. Visual information is the basis for most navigational tasks, so visually impaired individuals are at disadvantage due to the lack of information or given unsufficient information about their surrounding environment. With the recent advances in inclusive technology it is possible to extend the support given to people with visual disabilities during their mobility. In this context we propose and describe the SmartVision project, whose global objective is to assist visually impaired people in their navigation through unknown indoor and outdoor environments. This paper is focused mainly on the Computer Vision module of the SmartVision prototype, were we propose a new algorithm to recognise fiducials marks suitably placed on sidewalks, revealing to be a promising solution.

The SmartVision Navigation Prototype for the Blind

by Hugo Fernandes

Authors: J.M.H. du Buf, J. Barroso, J.M.F. Rodrigues, H. Paredes, M. Farrajota, H. Fernandes, J. José, V. Teixeira, M. Saleiro

The goal of the project "SmartVision: active vision for the blind" is to develop a small and portable but... more The goal of the project "SmartVision: active vision for the blind" is to develop a small and portable but intelligent and reliable system for assisting the blind and visually impaired while navigating autonomously, both outdoor and indoor. In this paper we present an overview of the prototype, design issues, and its different modules which integrate a GIS with GPS, Wi-Fi, RFID tags and computer vision. The prototype addresses glob-al navigation by following known landmarks, local navi-gation with path tracking and obstacle avoidance, and object recognition. The system does not replace the white cane, but extends it beyond its reach. The user-friendly interface consists of a 4-button hand-held box, a vibra-tion actuator in the handle of the cane, and speech syn-thesis. A future version may also employ active RFID tags for marking navigation landmarks, and speech recognition may complement speech synthesis.

Landmarks detection to assist the navigation of visually impaired people

by Hugo Fernandes

Authors: Paulo Costa, Hugo Fernandes, Verónica Vasconcelos,
Paulo Coelho, João Barroso and Leontios Hadjileontiadis

Assistive technology enables people to achieve independence in the accomplishment of their daily tasks and enhance... more Assistive technology enables people to achieve independence in the accomplishment of their daily tasks and enhance their quality of life. Visual information is the basis for most navigational tasks, so visually impaired individuals are at disadvantage due to the lack of information or given insufficient information about their surrounding environment. With the recent advances in inclusive technology it is possible to extend the support given to people with visual disabilities during their mobility. In this context we propose a new algorithm to recognize landmarks suitably placed on sidewalks. The proposed algorithm uses a combination of Peano-Hilbert Space Filling Curves for dimension reduction of image data and Ensemble Empirical Mode Decomposition (EEMD) to pre-process the image, resulting on a fast and efficient recognition method and revealing a promising solution.

Stereo vision in blind navigation assistance

by Hugo Fernandes

Authors: Fernandes, H., Costa, P., Filipe, V., Hadjileontiadis, L., Barroso, J.

Visual impairment and blindness caused by infectious diseases has been greatly reduced, but increasing numbers of... more Visual impairment and blindness caused by infectious diseases has been greatly reduced, but increasing numbers of people are at risk of age-related visual impairment. Visual information is the basis for most navigational tasks, so visually impaired individuals are at disadvantage because appropriate information about the surrounding environment is not available. With the recent advances in inclusive technology it is possible to extend the support given to people with visual impairment during their mobility. In this context we propose a system, named SmartVision, whose global objective is to give blind users the ability to move around in unfamiliar environments, whether indoor or outdoor, through a user friendly interface. This paper is focused mainly in the development of the computer vision module of the SmartVision system.

Image segmentation in systems of stereo vision for visually impaired people

by Hugo Fernandes

Authors: Penedo, Andreia; Costa, Paulo; Fenandes, Hugo; Pereira, António; Barroso, João

According to the World Health Organization in 2002 more than 161 million people were visually impaired.
The... more According to the World Health Organization in 2002 more than 161 million people were visually impaired.
The mobility of the visually impaired reveals itself to be a rather complex task, even with the support of inclusive technologies. Currently, the most widespread and used means by the visually impaired people are the white stick and the guide dog, however both show some difficulties in their mobility. The white stick only detects obstacles at the ground level, whilst obtaining a guide dog correctly trained in Portugal is an expensive and slow solution, given that the communication between the visually impaired person and the dog is limited.
If the blind person had access to reliable information, and in real time, about the environment in which he lives, it certainly would be safer for him to move around it.
Thus, more and more, with the increasing development of the technologies, there is the possibility of creating systems that assist the visually impaired people in their task of detecting the obstacles and subsequent orientation.
The objective of this article is to create a system that allows the capture of images in real time and that accomplishes the segmentation resorting to the information with disparity. Later on, the result of the image segmentation will be used in a system that offers the visually impaired person information on the environment that surrounds him.
The image acquisition is done through a system of stereo vision that captures images from the surrounding environment as the user moves around.

Parallax cues in the design of graphics used in technical education to illustrate complex spatial problems

by Ramon Rubio

The explanation of certain 3D concepts is based on 2D drawings. These drawings should contain certain depth cues, such... more The explanation of certain 3D concepts is based on 2D drawings. These drawings should contain certain depth cues, such as perspective and overlapping. Until recently, parallax has not been used as a depth cue. Nevertheless, new technologies allow it to be incorporated. This forms the background to our study of the design of interactive educational resources and stereoscopic graphics. The results obtained demonstrate that (1) the use of parallax cues improves the interpretation of the figures and (2) that the assistance they afford is most appreciated by the students with less highly developed spatial perception.

Hysteresis effects in stereopsis and binocular rivalry

by Athena Buckthought

Interaction between binocular rivalry and depth in plaid patterns

by Athena Buckthought

A matched comparison of binocular rivalry and depth perception with fMRI

by Athena Buckthought

Development of a Multi-AUV SLAM Testbed at the University of Michigan

by Hunter Brown