In-line inspection of surface feature and defect

An efficient 3D profile measurement technique is proposed for in-line full-field inspection of surface feature and defect with high resolution. In this technique, a straight-line grating from a digital light processing illumination source was projected onto the surface of a translated substrate. The successive line images of the grating were grabbed and integrated using a fixed linear CCD to reconstruct surface contour of the target substrate. Using a colored CCD allows for three separate sets of contour maps from the RGB lines. These are used to obtain a crucial relationship between object height distribution and surface contour via a phase-shifting algorithm without a phase shifter. Experimental results show measurement accuracy in the order of micrometer and offer high repeatability in the sub-micrometer scale. Since larger specimen can be inspected by increasing either the number of pixels of the CCD or the imaging modules, we demonstrate that this technique is viable for high resolution and high speed full-field inspection of surface features in production lines.