Research On Rapidly Inspecting Methods Of Image Quality Of Near-to-eye Display Optical System

With the continuous development of the technology of micro-display, design and process of advanced optics and hardware and software, the Near-to-Eye Display(NED) technology is getting mature and has been widely used in expansive fields. The image quality of NED devices has a closely relationship with its optical system, so it is a necessary and significant work to test and evaluate the image quality of system. With the shortcomings such as subjectivity, without quantitative standard and big error, the traditional evaluating methods can’t be applied in NED optical system evaluation. However, few methods that can be used for NED system have high cost, complex operation and consume long time. Method that can rapidly inspect the image quality of NED optical system is proposed in this thesis. The image quality of optical system can be evaluated by MTF curve obtained based on the theory of frequency spectrum. With its simple operation and high efficiency, the method can be applied for rapidly inspecting and evaluating image quality of NED optical system.The first part of the thesis generally introduces traditional evaluating methods of image quality with their characters, as well as the research status of image quality evaluation methods of NED optical system at home and abroad.The second part of the thesis generally introduces theoretical foundation of the optical transfer function(OTF), elaborated the principles and traditional methods of MTF measurement. Relationship between MTF and contrast transfer function(CTF) and the MTF property of cascade system are derived. Those are theoretical basis for the proposal of in the next chapter.In the third part, a experimental scheme is proposed that can rapidly inspect the MTF of NED system. Combined with the characters of NED optical system, experimental equipments are selected. And then establishment of platform and process of image processing are described. In the end, the MTF curve of center field of NED system under test is obtained.In the fourth part of the thesis, the experimental results are compared to the real MTF curve measured by standard MTF instrument. Reasons that may cause the error of measurement are analyzed and methods of reducing the error are discussed, the correction of error analysis is proved experimentally. The algorithm of image processing optimization is generally introduced. After comparing the advantages and disadvantages of the two algorithms, the one that based on extreme value algorithms and assisted by histogram algorithms is defined.The fifth part of thesis discusses the limitation of evaluating methods of optical system by MTF curve. Inspecting method of MTF of off-axis, angle of field, distortion and color reduction are proposed respectively, evaluation standards of NED system image quality are simply discussed.By theoretical analysis, error analysis and algorithm optimization, it shows that the result of experiment agrees well with the one of MTF analyzer. The approach with its simple operation, high efficiency and accuracy, can be applied to the measurement and image quality evaluation in the production of NED optical system.