The Fabrication Of High Accuracy Phase Computer Generated Hologram By Physical Vapor Deposition

With the development of optical system used in astro-observation and earth observation,more and more off-axis and free-form surfaces are using for its special advantages in light-weight and improving image quality.Computer generated hologram(CGH)testing,a high accuracy and aberrationless technique,plays an important role in the wavefront testing of off-axis and free-form surfaces.CGH is the key element in CGH testing,which includes amplitude CGH and phase CGH.Amplitude CGH has higher accuracy and meanwhile lower efficiency of diffraction,which limits it application.Phase CGH has higher efficiency of diffraction and can be used in many situations.However,the accuracy of phase CGH is limited by the fabrication technique.So,the study of the fabrication technique of phase CGH is important for CGH testing.At present,the main way of fabricating phase CGH is using reactive ion etching,which suffers from low accuracy.To improve the accuracy of phase CGH,physical vapor deposition(PVD)was applied to the fabrication of CGH.The contents of the paper include three parts.1.The theory of phase CGH fabricated by PVD.The wavefront errors of phase CGH fabricated by PVD were analyzed,and corresponding model was developed to verify the high accuracy of phase CGH fabricated by PVD.2.The study of errors induced by laser direct writing systems.To quantitatively determine the influence of errors induced by laser direct writing to CGH,a theoretical model was proposed.We also established an experiment to verify the feasibility of the proposed model.3.The fabrication of phase CGH by PVD.On the basis of the theory and fabrication technique,a phase CGH was fabricated by magnetron sputtering,and the testing results indicate that the accuracy of the CGH is 0.020 ?(root mean square,RMS)and the diffraction efficiency of 1st order is 0.245.