Shape Recovery From Images, With Multiple Grey Levels, Generated By Light Sectioning

The measurement of shape by automatic visual inspection tends to be burdened by an excess of image data. An economic method of data reduction is simplification of the object scene. Light sectioning, a form of structured illumination, is widely used in many industrial inspection systems. If the intensity distribution within the thickness of the sectioning light sheet is graded and the corresponding variation of image irradiance is resolved to several grey levels, a substantial increase in measurement accuracy can be achieved. Details and limitations of an image processing technique are described, drawing on the results obtained with an inspection system which measured cross sectional profiles of rails at high train speeds.