An accurate phase-height mapping algorithm by using a virtual reference plane

Abstract

In the phase measurement profilometry, the phase-height mapping is to calibrate the system by the height and phase of several known planes. The four planes method, which only needs the four references, is widely used due to its least amount of data. But for its height reconstruction, a large reconstructed height error will be introduced when the phase difference is close to 0. An improved phase-height mapping method, which is to create a virtual reference plane with a known height along the original reference plane, is proposed. Then the coefficient tables a, b, c, which are capable to suit for the whole calibration space, will be calculated and can improve the accuracy of 3D object reconstruction as well as the efficiency. The experimental results show that the mapping height errors can be significantly reduced. The RMS error of the reconstructed object is less than 4.8μm with the proposed method, while that of the traditional method is 350μm.