Integrating eye rotation and contrast sensitivity into image quality evaluation of virtual reality head-mounted...

Visual perception on virtual reality head-mounted displays (VR HMDs) involves human vision in the imaging pipeline. Image quality evaluation of VR HMDs may need to be expanded from optical bench testing by incorporating human visual perception. In this study, we implement a 5-degree-of-freedom (5DoF) experimental setup that simulates the human eye geometry and rotation mechanism. Optical modulation transfer function (MTF) measurements are performed using various camera rotation configurations namely pupil rotation, eye rotation, and eye rotation with angle kappa of the human visual system. The measured MTFs of the VR HMD are inserted into a human eye contrast sensitivity model to predict the perceptual contrast sensitivity function (CSF) on a VR HMD. At the same time, we develop a WebXR test platform to perform human observer experiments. Monocular CSFs of human subjects with different interpupillary distance (IPD) are extracted and compared with those calculated from optical MTF measurements. The result shows that image quality, measured as MTF and CSF, degrades at the periphery of display field of view, especially for subjects with an IPD different than that of the HMD. We observed that both the shift of visual point on the HMD eyepiece and the angle between the optical axes of the eye and eyepiece degrade image quality due to optical aberration. The computed CSFs from optical measurement correlates with those of the human observer experiment, with the optimal correlation achieved using the eye rotation with angle kappa setup. The finding demonstrates that more precise image quality assessment can be achieved by integrating eye rotation and human eye contrast sensitivity into optical bench testing.