Measurement of dual frequency interference fringe morphologyunder parallel optical wavefront modulation

The grating projection is usually used in traditional profilometry, and the non-sinusoidal of fringe and the limitation of fringe density can affect the accuracy of topography measurement. In order to realize the adjustability of high-density sinusoidal fringe projection, the parallel light interference projection is used to form bright and high contrast sinusoidal fringe, so that the sine distortion of fringes is avoided. In parallel wavefront modulation, the desired fringe frequency is obtained by adjusting the intersection angle of the two beams by phased array, and the adjustable fringe projection is realized, then the modulated dual frequency are applied to improve the phase unwrapping accuracy. The restoration of an object with maximum height of 35.80 mm under the condition of single frequency and dual frequency unwrapping was compared, and the relative error of the highest point recovery was 2.7% and 1.6%, respectively. The experimental results show that the method is effective and feasible, and has high precision.