Study on the Virtual Image Distance Measuring Device for Near-Eye Display Based on Autofocus
XU Hao1a,1b, LIANG Haowen1a,1b, LI Shu2, MENG Xiangfeng2
1. a. State Key Laboratory of Optoelectronic Materials and Technologies; b. School of Physics, Sun Yat-sen University, Guangzhou
Guangdong 510275, China; 2. Institute for Medical Devices Control, National Institutes for Food and Drug Control, Beijing 102629, China
Abstract：Objective Virtual reality (VR) and augmented reality (AR) can render and project virtual images to human eyes. The virtual
image distance can be adjusted by controlling the diopter of near-eye display, the virtual image distance can be adjusted, thus adapting
to the viewing of people with different vision. However, due to the wide range of virtual image, it is difficult to achieve continuous
and accurate measurement. To propose a virtual image distance measuring device for near-eye based on autofocus in this paper to
solve this problem. Methods This paper proposed a method to accurately determine the virtual image distance of VR/AR devices.
The device was composed of an adjustable focus lens, a stepper motor, a firmware tool and an adaptive program. The focal length
of the adjustable focus lens was automatically adjusted by the stepper motor and the adaptive program of image definition analysis.
The inspection accuracy and test range of the device were analyzed. Results Compared with the traditional method (global scanning
method), the mountain climbing search method in this paper was used to determine the moving direction and moving step length of
the motor by comparing the Laplace values before and after. The focus time of the automatic focusing method based on the mountain
climbing algorithm was shorter, the efficiency was improved with better performance of the test device. The device automatically
completed the whole measurement process in only 4 min. The accuracy of the experiment was 0.001 m. Under the degree of +2D
to -4D, the virtual image distance of the commercial VR glasses varies from 0 to 13.830 m. And it can be obtained according to the
distance calibration curve that the virtual image distance can be measured by the device at more than 17 m. Conclusion The virtual
image distance measurement method and device based on autofocus proposed in this paper can carry out high-precision, large-stroke
and automatic measurement of the depth distance of virtual images, and accurately calibrate the virtual image depth distance of neareye
display devices, and effectively improve the test performance.
徐豪1a,1b，梁浩文1a,1b，李澍2，孟祥峰2. 基于自动聚焦的近眼显示虚像距离测试装置研究[J]. 中国医疗设备, 2023, 38(8): 11-15.
XU Hao1a,1b, LIANG Haowen1a,1b, LI Shu2, MENG Xiangfeng2. Study on the Virtual Image Distance Measuring Device for Near-Eye Display Based on Autofocus. China Medical Devices, 2023, 38(8): 11-15.
