A method is described for reducing the large error that often occurs in the measurement of three-dimensional (3D) objects using the photometric stereo method when there is a specular component in the reflection characteristics of the object's surface.
First, the change in the luminance distribution caused by the component is estimated based on the correlation between the modeled distribution and a gray-level image of the object, created by numerical experiment.
Next, the shape measurement of the hemisphere object was carried out. Numerical experiment of a hemispherical object showed that the mean error of normal vector can be reduced by as much as 90%. Thismethod is applicable to machine vision, automatic manufacturing, and other industrial processes.