Catalogue of Artificial Intelligence Techniques


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Range Finding

Keywords: light striping, phase change, spot range, time of flight, ultrasound

Categories: Vision

Author(s): H.W. Hughes , Ashley Lotto

There are several methods for obtaining image depth information by range finding. In light striping (a form of Structured Lighting), a single plane of light is projected onto a scene. An imaging system is used to detect this reflected light. If the equation of the light plane and the parameters of the imaging system are known then the position in 3D space of each point along the line can be determined. A spot range can be determined by emitting a short burst of light (usually with a laser) and measuring the `time of flight' of the reflected pulse. An alternative approach is to modulate the light and obtain an estimate of the range from the phase change in the returned signal. Instead of light, ultrasound or `sonar' can also be used. Range estimates are normally achieved by `time of flight' but ultrasound has the advantage that, unlike light, it is only partially reflected from boundaries enabling range information to be determined through a column of material. The disadvantage is that most surfaces behave like `sonar mirrors' so that interpreting where you are is like walking in a room full of mirrors.



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