Three-dimensional imaging technology has been rapidly evolving as has its use in machine vision. Three-dimensional imaging is used in other fields such as object and space modeling, computer vision, R&D work or autonomous robot guidance; some of the methods used in those fields have had little or no use in machine vision. While the line between other fields and machine vision is often blurred, the emblematic differences of machine vision influence which 3-D technologies get used. These include the need to accomplish repetitive automatic inspection, robot guidance and automated image analysis tasks rapidly with near-100% reliability within reasonably well-defined scenarios.
Certain machine vision methods are able to extract limited 3-D information without actually developing the 3-D image. Examples of these are methods using structured laser illumination or systems that can determine distance from the apparent size of known objects. These are worth noting, however, and this article will highlight methods that form at least partial 3-D images.