Effective selection of the optimal virtual reality (VR) lens interval of VR devices using the test patterns of the different shapes for the left and right eyes

Selection of the optimal virtual reality (VR) lens interval L_I between two convex lenses of a VR device is important for the comfort of viewers. This study examined how the participants selected L_I for two types of test patterns. Twenty-one participants with interpupillary distances (IPDs) of 59–68 mm were selected. When the participants were asked to change the L_I to match specific positions of the test pattern in which the shapes for the two eyes were different, the selected values of L_I did not depend on the initial lens distances. When they were asked to change L_I for their best viewing distances using the test pattern with the same shapes for two eyes, the selected values strongly depended on the initial lens conditions. This dependence can be attributed to the finite range of eye rotation inside which binocular fusion can occur. No noticeable dependence of the selected values on IPD was observed. Excessive eye rotation to enable binocular fusion can cause eye strain. In the former test pattern, binocular fusion does not occur, and each eye is aligned along its fusion-free eye position with little eye strain. Hence, the former test pattern using the different shapes is preferable for controlling the lens interval.