Mobile Focus + Context (mF+C) involves using a handheld device as a focus screen for content on an immersive display or mobile projector. In this work we examine how using a focus device can mitigate poor context image quality due to environmental factors. In an exploratory study we compare three techniques for linking focus and context: lens-focus (Lens), where the device works as a mobile lens held parallel to and in front of the context, center-focus (Centered), where the user holds the device in the center of the projection and pans both context and focus by swiping, and marker-focus (Marker), where the focus region is highlighted on the context, and the user pans the focus by swiping. Participants performed searching, tracing, and detail acquisition tasks with maps and electronics diagrams under a range of simulated projection conditions. All techniques were able to mitigate poor projection quality and performed comparably in time and precision, but the effectiveness of each technique was impacted by task type. There was lower variation in time between participants using Lens for tracing tasks versus the other techniques, but wider variation for searching tasks. Tasks completed using sub-optimal projections involved more time spent looking at the context image than tasks with clear projections, however this difference is less pronounced for the Lens technique. We propose a hybrid Lens-Marker approach for mobile Focus+Context applications in dynamic environments.

移动焦点 + 上下文 (mF+C) 涉及使用手持设备作为沉浸式显示器或移动投影仪上内容的焦点屏幕。在这项工作中，我们研究了如何使用聚焦设备来缓解由于环境因素而导致的较差的上下文图像质量。在一项探索性研究中，我们比较了三种连接焦点和上下文的技术：镜头对焦（Lens），其中设备充当与上下文平行并位于上下文前面的移动镜头；中心焦点（Centered），其中用户持有设备位于投影中心，并通过滑动来平移上下文和焦点，以及标记焦点 ( Marker )，其中焦点区域在上下文上突出显示，并且用户通过滑动来平移焦点。参与者在一系列模拟投影条件下使用地图和电子图表执行搜索、追踪和细节获取任务。所有技术都能够缓解较差的投影质量，并且在时间和精度方面表现相当，但每种技术的有效性都受到任务类型的影响。与其他技术相比，使用 Lens 进行跟踪任务的参与者之间的时间差异较小，但搜索任务的时间差异较大。使用次优投影完成的任务比使用清晰投影的任务花费更多的时间来查看上下文图像，但是对于镜头技术，这种差异不太明显。我们提出了一种混合镜头标记方法，用于动态环境中的移动焦点+上下文应用程序。