Modeling and compensation of phase error in projection moiré

Abstract

The phase error caused by the non-sinusoidal characteristics of the projector and reference grating seriously reduces the measurement accuracy of projection moiré, yet relevant research is lacking. This work presents a phase error model and a phase compensation method to address this issue. The model is established by considering the multiple error sources and phase-solving principles. By employing the phase error model difference, the method accurately fits the model parameters from the non-ideal phase error. With these parameters, the phase error is iteratively extracted and eliminated from the measured phase. Due to its comprehensive consideration of the impacting factors, the model can clarify the phase error mechanism. The method not only significantly enhances the measurement accuracy but also requires only relatively few images for calibration. Experimental results demonstrate an improvement in the morphology measurement accuracy by up to 50%.