High Accuracy Confocal Full-Field 3-D Surface Profilometry for Micro Lenses Using a Digital Fringe Projection Strategy

A high-accuracy full field 3-D surface profilometer using digital structured fringe projection is presented in the article. In the proposed method, a depth-focus response curve can be established by performing a confocal scanning along the optical axis of the measurement system when a digital fringe is controlled and projected by a digital micromirror device (DMD). To avoid specular light diffusive problems, the developed method projects spatially encoded digital fringe patterns with modulated light intensity onto a shinny lens surface, in order to achieve full field and high accuracy measurement. Some of spherical microlenses have been measured to attest the feasibility of the developed approach. The depth measurement resolution can reach up to 0.1μm and the averaged measurement error was verified to be a submicro scale.