Accurate Measurement of Virtual Image Distance for Near-Eye Displays Based on Auto-Focusing

Virtual Reality (VR) and augmented reality (AR) are able to project virtual images to human eyes at a certain depth distance. This virtual image distance can be adjusted by controlling the diopter of the near-eye display. However, it is difficult to be measured accurately and continuously since this virtual image distance spans a large range. In this work, we propose a method to accurately determine the virtual image distance of commercial VR/AR equipment. The measurement apparatus is built and calibrated to validate the feasibility. The focal distance of the focus-tunable lens can be automatically adjusted via the step motor by cooperating with the image sharpness analyzing program. Compared with other proposed methods, ours provides an effective means to achieve high accuracy, wide and continuous testing range, and automatic evaluation of virtual image distance for compact near-eye displays.