Development of white light confocal microscopy with innovative fringe projection for full-field micro surface profilometry

An innovative full-field three-dimensional micro surface profilometer using digital fringe projection with digital micromirror device (DMD) technology and confocal principle is presented in the article. In viewing the fact that conventional laser confocal measurement method not only easily encounters undesired irregular scattering problems being introduced by object´s surface discontinuities, but also lack scanning efficiency due to its single-point type measurement, the newly developed profilometer deploys a DMD chip to project spatially encoded digital fringe patterns with dynamic light intensity control, onto the object to obtain excellent measurement performance. A novel digital fringe pattern design with sinusoidal intensity modulation was developed for active confocal microscopy, to obtain optimized depth resolution with a micrometer lateral resolution. Some of important semiconductor components have been measured to attest the feasibility of the developed approach. The depth measurement resolution can reach better than 0.1mum and the maximal measured error was verified to be within 1% of the vertical full-scale measurement range.