Rainer, H., Derpanis, K., MacLean, W. J., Verghese, G., Jenkin, M., Milios, E., Jepson, A., and Tsotsos, J. K., SAVI: an actively controlled teleconferencing system, Image and Vision Computing, 19: 793-804, 2001.
A Stereo Active Vision Interface (SAVI) is introduced which detects frontal faces in real world environments and performs particular active control tasks dependent on hand gestures given the by the person the system attends to. The SAVI system is thought of as a smart user interface for teleconferencing, telemedicine, and distance learning applications.To reduce the search space in the visual scene the processing is started with the detection of connected skin colour regions applying a new radial scanline algorithm. Subsequently, in the most salient skin colour region facial features are searched for while skin colour blob is actively kept in the centre of the visual field of the camera system. After a successful evaluation of the facial features the associated person is able to give control commands to the system. For this contribution only visual control commands are investigated but there is no limitation for voice or any other commands. These control commands can either effect the observing system itself or any other active or robotic system wired to the principle observing system via TCP/IP sockets.The system is designed as a perception-action-cycle (PAC), processing sensory data of different kinds and qualities. Both the vision module and the head motion control module work at frame rate on a PC platofrm. Hence, the system is able to react instantaneously to changing conditions in the visual scene.
Ripsman, A., and Jenkin, M., Surface reconstruction of objects in space, Proc. ISAIRAS 2001, Montreal, Quebec, 2001.
The increasing number of objects orbiting our planet necessitates the creation of sensing systems designed to determine the surface structure of such objects. One of the key challenges facing computer vision systems used in space is the presence of specular surfaces on most man-made orbital objects. Such surfaces present a challenge to conventional vision systems due to specular reflections, which may mask the true location of the object and hence lead to incorrect measurements. The incorporation of traditional highpowered illuminants, such as laser beams, in a space-based computer vision system can also be problematic since the instruments inside space structures may be sensitive to various forms of radiation. A properly designed computer vision system could assist in the repair and maintenance of delicate space equipment. This article describes the development of a fixed vision system which can recover the local surface structure of highly specular objects. The system utilizes a commercial trinocular stereo vision system and a low-power twodimensional illuminant. The local surface structure of an object is obtained by projecting coded light patterns onto the object. As space objects are neither fully specular nor fully diffuse, an algorithmhas been developed which recovers local surface structure fromboth the specular and diffuse regions of an object.
Ripsman, A., and Jenkin, M., Local surface reconstruction of orbital objects, IEEE Int. Symposium on Computational Intelligence (CIRA-2001), Banff, Alberta, 2001.
Conventional vision systems designed to reconstruct the surfaces of objects generally handle only diffuse objects or objects with a minimal amount of specularity. The presence of specular reflections produced by highly specular surfaces confuse traditional vision systems and may mask the true location of an object and lead to incorrect measurements. This article describes the development of a fixed vision system which can recover the local surface structure of highly specular objects. The system utilizes a commercial trinocular stereo vision system and a low-power two dimensional illuminant. The local surface structure of an object is obtained by projecting coded light patterns onto the object. As many objects are neither fully specular nor fully diffuse, the statistical method of mixture models is used to divide an object into specular and diffuse components in order to recover local surface structure fromboth specular and diffuse regions. The system was originally designed to assist in the insitu repair and maintenance of man-made orbital objects. One of the key challenges facing computer vision systems used in space is the presence of specular surfaces on virtually all man-made orbital objects. Because it was designed to be used in outer space, the system was designed to operate without traditional high-powered illuminants, such as laser beams, whose radiation can interfere with sensitive space instruments. While the system was designed to operate in outer space, it offers many other practical non-space applications.
Kapralos, B., Jenkin, M., Milios, E., and Tsotsos, J. K., Eyes 'n Ears Face Detection, IEEE Int. Conf. on Image Processing (ICIP-2001), Thessaloniki, Greece, 2001.
We present a robust and portable visual-based skin and face detection system developed for use in a multiple speaker teleconferencing system, employing both audio and video cues. An omni-directional video sensor is used to provide a view of the entire visual hemisphere, thereby allowing for multiple dynamic views of all the participants. Regions of skin are detected using simple statistical methods, along with histogram color models for both skin and non-skin color classes. Regions of skin belonging to the same person are grouped together, and using simple spatial properties, the position of each person's face is inferred. Preliminary results suggest the system is capable of detecting human faces present in an omni-directional image despite the poor resolution inherent with such an omni-directional sensor.
Kapralos, B., Jenkin, M., Milios, E., and Tsotsos, J. K., Eyes 'n Ears: Face detection utilizing audio and video cues, 2nd Int. Workshop on Recognition, Analysis and Tracking of Faces and Gestures in Real-Time Systems (RATFG-RTS 2001). Held in conjunction with ICCV 2001, Vancouver, BC, 2001.
This work investigates the development of a robust and portable teleconferencing system utilizing both audio and video cues. An omni-directional video sensor is used to provide a view of the entire visual hemisphere thereby providing multiple dynamic views of the participants. Regions of skin are detected using simple statistical methods, along with histogram color models for both skin and non-skin color classes. Skin regions belonging to the same person are grouped together. Using simple geometrical properties, teh location of each person's face in the "real world" is estimated and provided to the audio system as a possible sound source direction. Beamforming and sound detection techniques witha small, compact microphone array allows the audio system to detect and attend to the speech of each participant, thereby reducing unwanted noise and sounds emanating from other locations. The results of experiments conducted in normal, reverberant environments indicate the effectiveness of both the audio and video systems.
Redlick, F. P., Jenkin, M., and Harris, L. R., Humans can use optic flow to estimate distance of travel, Vis. Res., 41:213-219, 2001. Copyright Elsevier Science Ltd.
We demonstrate that humans can use optic flow to estimate distance travelled when appropriate scaling information is provided. Eleven subjects were presented with visual targets in a virtual corridor. They were then provided with optic flow compatible with movement along the corridor and asked to indicate when they had reached the previously presented target position. Performance depended on the movement profile: for accelerations above 0.1 m/s/s performance was accurate. Slower optic-flow acceleration resulted in an overestimation of motion which was most pronounced for constant velocity motion when the overestimation reached 170%. The results are discussed in terms of the usual synergy between multiple sensory cues to motion and the factors that might contribute to such a pronounced miscalibration between optic flow and the resulting perception of motion.
Allison, R. S., Harris, L. R., Jenkin, M., Jasiobedzka, J., and Zacher, J. E., Tolerance of temporal delay in virtual environments, Proc. IEEE VR'2001, Yokahama, Japan.Copyright IEEE.
To enhance presence, facilitate sensory motor performance, and avoid disorientation or nausea, virtualreality applications require the percept of a stable environment. End-end tracking latency (display lag) degrades this illusion of stability and has been identified as a major fault of existing virtual-environment systems. Oscillopsia refers to the perception that the visual world appears to swim about or oscillate in space and is a manifestation of this loss of perceptual stability of the environment. In this paper, the effects of end-end latency and head velocity on perceptual stability in a virtual environment were investigated psychophysically. Subjects became significantly more likely to report oscillopsia during head movements when end-end latency or head velocity were increased. It is concluded that perceptual instability of the world arises with increased head motion and increased display lag. Oscillopsia is expected to be more apparent in tasks requiring real locomotion or rapid head movement.
Jenkin, M. and Harris, L. (Eds.), Vision and Attention, Springer Verlag, 2001. Abstract It has become apparent that vision is not a passive process working on the retinal image like a film to record a prefect copy as the perception. Instead, higher-level cognitive processes such as expectancies, memories and experience play a critical, almost overriding role. This book is a review and summary of the tremendous advances that have been made in recent years on the effect of attention on visual perception. A CD-ROM is included that contains color images and movies that add to the various chapter contributions.The book will appeal to vision scientists as well as to people involved in using visual processes in computer animations, display design or the sensory systems of machines. Physiologists and neuroscientists interested in sensory or motor processes will also find this a very useful volume.
Harris, L. and Jenkin, M., Vision and Attention, In M. Jenkin and L. Harris (Eds.) Vision and Attention, pp. 1-17, Springer Verlang, 2001.
The term "visual attention" embraces many aspects of vision. It refers to processes that find, pull out and may possibly even help to define, features in the visual environment. All these processes take the form of interactions between the observer and the environment: attention is drawn by some aspects of the visual scene but the observer is critical in defining which aspects are selected. Although this book is entitled Visual Attention, none of the processes of "visual" attention are exclusively visual: they are neither driven exclusively by visual inputs nor do they operate exclusively on retinal information. In this introductory chapter, we outline some of the problems of coming to grips with the ephemeral concept of "visual attention."
Zikovitz, D. C., Jenkin, M. and Harris, L. R. Comparison of stereoscopic and non-stereoscopic optic flow displays. [Abstract]. J. of Vision, 1: 317a, 2001.
Non-stereoscopic optic flow can evoke vection of an inaccurate magnitude (Jenkin, Redlick, Harris, ARVO 2000). Stereoscopic information can affect vection, shortening its latency and increasing its duration (Palmisano, Percept. Psych. 1996 58: 1168). Does stereoscopic information influence the magnitude of vection? Methods: Subjects wore alternating shutter glasses (96Hz) to view either a non-stereoscopic or a binocular, 3-dimensional virtual corridor projected onto a large display surface comprised of two orthogonal walls with their corner straight ahead at a distance of 3.5m. Subjects viewed a virtual target at between 4-32m which was extinguished before forward self-motion at either constant velocity (0.4m/s-6.4m/s) or acceleration (0.025m/s/s-1.0m/s/s) was simulated. Subjects reported when they perceived they had reached the previously presented target position. Results: When subjects viewed the large, non-stereoscopic display, we reproduced our previous results obtained in a non-stereoscopic HMD. Subjects overestimated their motion at slower accelerations (constant velocity and 0.025-0.4m/s/s), and were accurate at higher accelerations (0.4-1.0 m/s/s). When subjects viewed the display with stereoscopic cues, they overestimated their motion at both slower (0.025-0.4m/s/s) and higher accelerations (0.4m/s/s - 1m/s/s). Conclusion: Adding stereopsis, far from improving the accuracy of distance judgments, surprisingly was associated with overestimation even of high acceleration movements (which were judged accurately in non- stereoscopic displays).
