Coarse-phasing-simulation results of JWST-like segmented imaging system. (a) Peak-position extraction. (a1) Configuration of segmented primary mirror with the upper left sub-aperture defined as the reference. (a2) Peak position. (b) Initial state of imaging system before correction. (b1) Initial piston distribution. (b2) Aberrated PSF. (c). Differential spectral-scanning process. The initial PSF and corresponding modulated PSF are shown in (c1) and (c2), the differential MTF and the extracted peak height are shown in (c3) and (c4). (c5) Scanning results and fitted Gaussian function of one non-reference segment. (c6) Residual piston after coarse phasing with average wavefront RMS of 119.8 nm. The corrected PSF and modulated PSF after coarse phasing are shown in (c7) and (c8). The differential MTF and extracted points after coarse phasing are shown in (c9) and (c10).