Due to their subjective nature, conventional virtual image viewing distance (VID) measurement methods in AR optical systems are easily disturbed by field depth of the photography system. To mitigate this issue, this study proposes a method to stabilize object distances between virtual images and actual reference objects using the field depth property based on the measurement principle of VID. In our experimental analysis, the edge-based spatial frequency response is used to measure the relative change of image sharpness in shooting virtual images and reference objects by the same photography system. During this process, the VID is converted into view distance at the corresponding focus position, and a corresponding quantitative measurement is returned. Experimental results show that the VID measurement result generated in this study (1397 mm) matches the theoretical design value of the AR waveguide lens sample (1400 mm), which demonstrates the measurement system's validity. Furthermore, a measurement error of 10-40 mm is observed, which is 1.6%-6.45% of that generated by conventional measurement methods. Because this method enables VID measurement in common experimental optical systems, it is highly applicable across AR-equipped devices, which in turn should help advance these devices' design and production.