A Non-Calibration Nonlinear Errors Correction Method for Phase-Shifting Patterns

To reduce phase errors caused by nonlinear responses in the measurement system, we propose a non-calibration correction method for nonlinear errors in phase-shifting patterns. First, the captured grating fringes are transformed using a Fourier transform to convert the images from the gray scale to the frequency domain. The first harmonic frequency is then determined using an appropriate method. Second, the appropriate filter cutoff frequency is calculated by combining the phase-shift algorithm's sensitivity to different harmonics with frequency response curves. Low-pass filtering is then performed on the phase-shift patterns to suppress high frequencies caused by nonlinear responses, thus reducing phase errors in the actual measurement process. Finally, the standard plane and other irregularly shaped objects were reconstructed using the proposed method and other techniques. Measurement errors under different conditions were then compared. Experimental results show that the proposed method significantly suppresses gamma nonlinear responses and achieves high measurement accuracy and efficiency.