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Introduction
Vision is probably the most commonly used, complex and flexible sense used by
biological systems to gather information about the environment. Biological vision systems
are capable of extracting many different types of information from the environment. For
example, some can determine colour, some can see in the infra red part of the spectrum,
some can detect changes in polarisation of light passing through the atmosphere while
others can use multiple eyes to determine depth information.
However there is one source of visual information that is believed to be exploited by
all biological vision systems, and that is motion information.
Artificial vision systems have become important in many industrial and commercial
applications, however limitations in computational power have restricted these systems to
using still images. The rapid increase in cheap computing power is now making the
development of real time motion processing systems practical.
The Biotech Imaging Group in the CSIRO Division of Mathematics, Informatics and Statistics is
commencing work in the area of image motion analysis. This page discusses some of the
potential areas of interest.
Potential Applications
There are a number of applications where motion information offers significant
advantages over still image processing.
Video Coding
Motion compensation for video compression is probably the most common form of image
motion processing in commercial use today. Motion compensation improves the compression
rate of video compression systems.
Segmentation
Motion is a very powerful cue for segmentation. In fact the human visual system is
capable of isolating objects by using only motion information. Consider the picture below.
This is an example of perfect camouflage, since the object has a texture that is identical
to the background. Try stopping the animation and notice how quickly it becomes impossible
to segment the object from the background. This is an example of a classical psychological
test used to demonstrate the importance of motion perception in human vision.
Look at the segmented version.
Motion based segmentation can be used as a preprocessing step for many
conventional forms of image processing. Examples include face recognition and vehicle
identification.
Data Fusion
There is a significant amount of interaction between different areas of the human
visual system. For example, information is shared between the stereo and motion
subsystems, and between the stereo and line completion subsystems. It is therefore likely
that robust artificial vision systems will combine motion processing with other forms of
visual processing.
Robotics
Visual motion information is vital to mobile creatures for tasks such as navigation,
obstacle avoidance and limb coordination. Artificial motion processing systems capable of
performing these tasks are likely to be useful in similar roles in robotic systems that
interact with complex and changing environments.
Motion in the visual field that is caused by the motion of the observer can convey
important information about the observer's motion. This information can be used to
stabilise the observer (i.e. to help maintain balance), avoid obstacles and to identify
the direction of heading of the observer. If the observer's motion is known, then the
visual information can be used to infer information about the structure of the
environment. Systems capable of performing these kinds of tasks are likely to be useful
for self navigating robots.
Hand-eye (or limb-eye) coordination in humans and animals is fundamental to many forms
of interaction with the environment. Vision helps to produce a closed loop control system
between the limb and the target. Artificial "visual servo" systems may help to
control more complex, flexible and lower cost robot limbs.
Classification
Motion information is also a useful cue for some forms of classification. In security
systems it is desirable to eliminate false alarms that might be caused by animals or wind.
Distinguishing between shapes in still images can be very difficult, but if motion is used
as an additional cue then more information is available. It seems that humans are very
good at identifying things in this way.
Consider the picture below - this set of eleven points could be almost
anything. Now click on the image to view the animated version, and it becomes immediately
obvious that the points are human in origin.
Gestures and lip reading
Some forms of communication, such as sign language and lip reading, obviously require
motion processing. Both could be important in human-computer interaction.
For more information about this work, contact Richard Beare. |
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