Shape Measurement and Reconstruction of Solar Concentrator Based on Two-dimensional Phase Shift Method

Deflectometry is used to measure the three-dimensional profile of the solar concentrator because of its high accuracy and short inspection time. In order to obtain the shape of concentrator, two different phases usually have to be computed for a single area. The two phases are calculated by using two sets of the phase-shifting patterns with two-different directions, respectively. In this paper, a new two-dimensional phase shifting method is proposed to obtain two phases with different directions with a single set of 2D phase, which reduces the number of acquired images and increase measurement speed. On the other hand, it is necessary to acquire the shape, which must be calculated from the slopes of the measured object. Existing integration techniques have some drawbacks that render them unusable in many cases. An approximation employing radial basis functions is applied to reconstruct the shape of concentrator, and reconstructs surfaces both locally and globally with high accuracy. Finally, experiments in measuring the shape of RP3 mirror demonstrate the proposed method's performance.