Error simulation of Ronchi gratings

In order to study the effect of grating manufacturing error on the accuracy of Moiré metrology,a transmittance function for Moiré fringes was built based on Fourier optical theory and coordinate conversion.The grating error function was simulated by means of linear superimposition.The grating errors were simulated based on previously received moiré fringe models.The Moiré fringe waveform caused by the short-period errors and long-period errors were obtained.Simulation results were analyzed and verified.Although short-period grating error induces high-order harmonics of Moiré fringe signal,its effect on measurement accuracy can be effectively removed after digital filtering.The long-period grating error can affect the accuracy of a grating test system.