Diffraction efficiency restoration method for a single-plane diffractive element considering machining errors

Diffractive optical elements (DOE) are crucial in the simplified development of optical systems. However, machining errors in diffractive elements are inevitable, and the diffraction efficiency degradation caused by these errors can affect the final image quality. In this study, the relationship between the machining errors of diffractive microstructures and diffraction efficiency is derived, and a point spread function (PSF) model with consideration of the machining errors is proposed. The processed microstructures are measured using a PGI optical profilometer, and the actual energy distribution matrix for each order, considering the machining error is obtained, and then, a diffraction efficiency imaging blur correction model is developed. The accuracy of the constructed model is quantitatively validated through actual diffraction efficiency measurements of the single-plane diffractive elements (SPDOE). The proposed method is finally validated through the actual scenario imaging and restoration. The peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) of the actual scenario images using the correction model are improved by 2.62 dB and 0.0556, respectively, compared to the restored images without considering the machining errors. Compared with images acquired by traditional refractive systems under the same image quality, the differences in PSNR and SSIM of real-world images processed using the corrected model remain within 2%. The blur effect induced by the reduction in diffraction efficiency is completely eliminated. This study provides a theoretical foundation for high-quality imaging of SPDOE and offers new insights for improving machining accuracy control and diffraction efficiency restoration techniques in related fields.