End-to-end (e2e) latency in head-mounted displays (HMD) is the time delay between a physical change in the world (e.g., a user's head movement) and the moment the display updates to reflect that change. Tracking, rendering, and other computation in real systems invariably introduce some amount of e2e latency to all HMDs. In modern devices this latency is usually in the range of 12-60 milliseconds which is partially addressed through pose prediction and late stage reprojection which means that perceptual studies and user experience evaluations cannot explore latencies below these values. Here, we introduce a video passthrough HMD, called Camsicle, which is capable of 2-millisecond e2e latency and, additionally, uses a catadioptric design to achieve perspective-correct passthrough without reprojection. This platform enables naturalistic user studies to interrogate the impacts of latency on user experience, preference, and performance. Across two user studies and 57 participants we find that 2 and 14.3 millisecond latencies are preferred over 23 and 29 milliseconds when attempting to catch a ball. Additionally, we compare individual latency preferences in this naturalistic ball-catching task to psychophysical thresholds for latency detection in a reference-grade system with zero latency to investigate how psychophysical thresholds may relate to subjective evaluations in naturalistic scenarios.

翻译：头戴式显示器（HMD）的端到端（e2e）延迟是指现实世界中的物理变化（例如用户头部运动）与显示器更新以反映该变化之间的时间差。实际系统中的追踪、渲染及其他计算不可避免地会给所有HMD引入一定程度的e2e延迟。在现代设备中，这种延迟通常在12-60毫秒范围内，部分通过姿态预测和后期重投影技术进行补偿，这意味着感知研究和用户体验评估无法探索低于这些值的延迟。本文介绍了一款名为Camsicle的视频透视式HMD，其端到端延迟可达2毫秒，并采用折反射光学设计实现无需重投影的透视校正透传。该平台支持开展自然场景用户研究，以探究延迟对用户体验、偏好和表现的影响。通过对57名参与者的两项用户研究发现，在尝试接球任务中，2毫秒和14.3毫秒的延迟比23毫秒和29毫秒更受青睐。此外，我们将这种自然场景接球任务中的个体延迟偏好，与零延迟参考级系统中的延迟检测心理物理阈值进行比较，以探究心理物理阈值如何关联自然场景中的主观评价。