Research On The Measurement Method Of Virtual Image Parameters In Augmented Reality Display

The research and development of augmented reality(AR)display technology has made rapid progress in recent years,but the current AR devices still need to be further improved in terms of user experience.For this reason,the virtual image parameters displayed in AR,such as Virtual Field of View(VFOV),Virtual Image Viewing Distance(VID)and Eyebox,are the main design objectives in the development of the device,and are also important indicators to measure whether the functional quality of the designed AR display system can meet user requirements.Therefore,accurate and convenient measurement of AR display virtual image parameters is an indispensable part of the development and use of AR devices.However,in previous studies,research into the measurement of virtual image parameters has been relatively brief,with problems such as unclear measurement methods and measurement standards,and much reliance on subjective judgement.In this paper,the original measurement method is improved to address these problems,and the design and construction of an AR display virtual image parameters measurement system is completed to achieve measuring VFOV and VID of AR display devices objectively and quantitatively.To address the problem of unclear methods in the process of VFOV measurement,in this paper,the VFOV of AR devices is measured using six types of pixel luminance statistical parameters as the basis for judging the virtual image edge.The experimental results show that,on the one hand,the luminance threshold,which is used as a basis for determining the virtual image edge,is extremely correlated with the VFOV measurement result,and that the difference between the average VFOV measurements obtained with different luminance thresholds is 11°(V)× 7°(H).On the other hand,VID measurement errors in multiple measurements have a much smaller impact on VFOV measurements than the impact of the luminance threshold selection,and the maximum fluctuation range of the measurements due to different VID measurements is 0.95°(V)×1.10°(H).In terms of the stability of the VFOV results under different VID measurement results,using the arithmetic mean of 0.64 times the pixel luminance as the luminance threshold,the resulting VFOV measurement is 23.613±0.228°(V)× 42.936±0.360°(H),with a relative fluctuation of only 0.91%,which is the most stable result and in line with the design expectations for AR lens sample.To address the problem that clear images in VID measurements are mostly dependent on subjective judgement and do not consider the depth of field of the camera system,the relative change in sharpness of the same camera system in the two processes of taking a virtual image and referencing the actual object is quantitatively calculated in this paper,and the measurement of VID is converted into the measurement of the distant view position of the photography system at the corresponding focus position,achieving a more accurate measurement of VID.The measurement error of the designed VID measurement system is 10mm～40mm,which has reduced the theoretical error by 1.6%～6.45%compared with the traditional method,and improved the measurement accuracy of the VID in AR display systems significantly.The AR display virtual image parameter measurement system designed in this paper provides a feasible solution for research institutions and manufacturers to more accurately and conveniently obtain parameters such as VFOV and VID,which is conducive to achieving further improvement of AR devices in terms of user visual experience and wearing comfort,and contributing to the progress of AR device design and production processes.