We provide the first perceptual quantification of user's sensitivity to radial optic flow artifacts and demonstrate a promising approach for masking this optic flow artifact via blink suppression. Near-eye HMDs allow users to feel immersed in virtual environments by providing visual cues, like motion parallax and stereoscopy, that mimic how we view the physical world. However, these systems exhibit a variety of perceptual artifacts that can limit their usability and the user's sense of presence in VR. One well-known artifact is the vergence-accommodation conflict (VAC). Varifocal displays can mitigate VAC, but bring with them other artifacts such as a change in virtual image size (radial optic flow) when the focal plane changes. We conducted a set of psychophysical studies to measure users' ability to perceive this radial flow artifact before, during, and after self-initiated blinks. Our results showed that visual sensitivity was reduced by a factor of 10 at the start and for ~70 ms after a blink was detected. Pre- and post-blink sensitivity was, on average, ~0.15% image size change during normal viewing and increased to ~1.5-2.0% during blinks. Our results imply that a rapid (under 70 ms) radial optic flow distortion can go unnoticed during a blink. Furthermore, our results provide empirical data that can be used to inform engineering requirements for both hardware design and software-based graphical correction algorithms for future varifocal near-eye displays. Our project website is available at https://gamma.umd.edu/RoF/.

翻译：我们首次定量测量了用户对径向光流伪影的感知灵敏度，并展示了一种通过眨眼抑制来掩盖该光流伪影的有效方法。近眼头戴式显示器通过提供模拟真实世界视觉的线索（如运动视差与立体视觉），使用户能沉浸于虚拟环境中。然而，这类系统存在多种感知伪影，可能限制其可用性及用户在虚拟现实中的临场感。一个众所周知的伪影是辐辏调节冲突。变焦显示器可缓解辐辏调节冲突，但会引入其他伪影，例如焦平面变化时虚拟图像尺寸的径向光流变化。我们开展了一系列心理物理实验，测量用户在自主眨眼前、中、后对径向光流伪影的感知能力。结果表明，视觉灵敏度在眨眼开始后约70毫秒内降低至原来的1/10。正常观看时，眨眼前后的平均灵敏度约为0.15%的图像尺寸变化，而眨眼期间增至约1.5%-2.0%。这一结果意味着，在眨眼期间，快速（70毫秒以内）的径向光流畸变可被忽略。此外，我们的实验数据可为未来变焦近眼显示器的硬件设计与基于软件的图形校正算法提供工程需求参考。项目网站：https://gamma.umd.edu/RoF/。