Multi-frequency projected fringe profilometry for measuring objects with large depth discontinuities

A multi-frequency projected fringe profilometry for measuring objects with large-depth discontinuities is proposed. Fringe patterns with multi spatial frequencies are projected onto an object-target. The wrapped phase maps in different spatial frequencies are obtained through a phase shifting method. The height of each point of the object surface can be obtained independently by finding the peak value in the exponential sums of the wrapped phases with different spatial frequencies. Several measured results on real objects are presented. This method avoids phase unwrapping and the height of each point is measured independently. Therefore, it is inherently simple and robust. This approach can be used for objects with complex shapes and large-depth discontinuities.