Stereovision for Real-Time Measurement of the Depth of Non-Contrastive 3-D Space by Projecting Random Patterns
Reported here is an active type stereovision system that we developed for the real-time depth measurement of a three-dimensional space by projecting certain random patterns. The system can measure non-contrastive environments an objects in three-dimensional space. We call the system “ SVRP (Stereo Vision with Random Pattern Projection)”.
The system consists of a standard stereovision unit composed of 2 lenses and 2 CCD cameras, and a projector to project random patterns.
The internal processing of the system enables almost real-time processing using a unique method which we call “ Laminated Difference Method (LDM).”
The basic principle of this method is to determine corresponding points by comparing the lightness of each picture element in the right and left pictures as the basic information. This then allows the achieving of high-speed processing and the avoiding of occlusion problems. This method does not use the conventionally suggested method of determining corresponding points by calculating the correlation between domains of a certain size.
To reduces the vagueness of the correspondence relationship that occurs when only comparing lightness to determine corresponding points, we retrieve corresponding points using heuristic geometrical relationships among object in a space, or increase the corresponding points and further clarify correspondence by projecting ramdom patterns onto objects.
The random patterns projected are slit patterns of about 90 slit beams of random lightness for a CCD(256 x 256) plane.
Projecting random patterns offers an advantage in that the projected patterns are almost unaffected by the active patterns projected by other mobile robots.
Also, this visual sense system can be used for visual sensing by mobile robots during nighttime.
This system can process 256 horizontal scanning lines in 1.7 seconds using 10 MHz NEC PC Pascal language, that is, from the taking in of a picture to the obtaining of a measurement result of the depth in a visual field.
KeywordsMobile Robot Scanning Line Random Pattern Stereo Vision Pattern Beam
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