Multicolor fringe projection system with enhanced 3-D reconstruction of surfaces

Most optical topology systems use a single wavelength laser for projection, using a swept spot, a moving line, or a projected grating. In a typical projected grating system, the gratings are shifted and a series of images are used to recover the 3-D shape of the target. When the series of images is analyzed in the normal phase shift manner, the resulting 2-D phase map typically has phase unwrapping problems due to noise and Nyquist limits. Surfaces with large vertical discontinuities present the biggest problem in 3-D shape recovery. This paper looks at simultaneously projecting multiple wavelengths onto a surface to help avoid problems in unwrapping the 2-D phase map. Using multiple wavelengths, the interferometer mirror does not have to be rotated to change the grating pitch and some operations can be done in parallel which reduces scanning time. Limitations and improvements in the current system will be discussed.