Improved three-dimensional profile measuring method based on intensity-ratio measurement

Abstract

In the existing intensity-ratio measuring methods, unwrapping the intensity ratio may be erroneous or even fail when measuring complex and isolated objects. This paper presents an improved three-dimensional (3-D) profile measuring method based on intensity-ratio measurement. Two shifting triangular patterns are projected to generate a triangular intensity-ratio distribution, and a Ronchi grating is projected to correctly divide the triangular intensity-ratio regions. Then, an absolute intensity ratio is retrieved point-by-point with the periodic label of the projected Ronchi grating. Finally, the intensity-ratio-to-height mapping algorithm is used to reconstruct the 3-D surface shape. The experimental results have demonstrated the feasibility and validity of the proposed method in restoring 3-D surface shape of the complex and isolated objects.