A novel depth-from-hybrid-focus method for surface morphology with depth discontinuity

A novel depth-from-hybrid-focus (DFHF) method is proposed for the reconstruction and inspection of surface morphology with high depth discontinuity. Multiple laser stripes and their hybrid focus are incorporated in DFHF. First of all, a calibration table for estimating rough depth information is generated in DFD. The calibration table means a correlation between the depth of a reference block and the width of laser stripes. Secondly, the rough depth information can be speedily computed using the calibration table, after the width of laser stripes is extracted in only one defocused image of a surface with depth discontinuity. Finally, depth-from-focus (DFF) with a fine step interval is applied to the vicinity of the rough depth information from DFD, in order to make an accurate measurement. Through the fusion of DFD and DFF, the novel DFHF improves highly problems of two previous methods in high depth discontinuity simultaneously. Experiments show that DFHF gives more accurate and reliable results than DFD and more speedy responses than DFF.