New Simple Large Depth of Field Fringe Projection Profilometry System Using Laser Projector

Fringe Projection Profilometry (FPP) is a widely used non-contact technique for 3D measurements in different fields such as reserve engineering, quality assurance and security systems. Traditional FPP systems suffer from many problems i.e., limited working distance and large phase error. These problems exist due to the limited depth of field of the optical element of the systems components and nonlinear gamma response. This paper introduces large depth of field FPP system utilizing focus-free laser projector. Nonlinear gamma effect of red, blue, and green channels is studied, and phase error is calculated for each. Also, the focus-free projection of the projector at different distances up to 1725 mm is studied. Large depth of the field and the working distance of the system equal to 300 mm within the distance from 800 to 500 mm were proved with improved phase error. The large depth of field and working distance of the system are demonstrated by phase map calculation of cylindrical surface at four different distances equal to 800, 700, 600 and 500 mm.