Projection mapping (PM) enables augmented reality (AR) experiences without requiring users to wear head-mounted displays and supports multi-user interaction. It is regarded as a promising technology for a variety of applications in which users interact with content superimposed onto augmented objects in tabletop workspaces, including remote collaboration, healthcare, industrial design, urban planning, artwork creation, and office work. However, conventional PM systems often suffer from projection shadows when users occlude the light path. Prior approaches employing multiple distributed projectors can compensate for occlusion, but suffer from latency due to computational processing, degrading the user experience. In this research, we introduce a synthetic-aperture PM system that uses a significantly larger number of projectors, arranged densely in the environment, to achieve delay-free, shadowless projection for tabletop workspaces without requiring computational compensation. To address spatial resolution degradation caused by subpixel misalignment among overlaid projections, we develop and validate an offline blur compensation method whose computation time remains independent of the number of projectors. Furthermore, we demonstrate that our shadowless PM plays a critical role in achieving a fundamental goal of PM: altering material properties without evoking projection-like impression. Specifically, we define this perceptual impression as ``sense of projection (SoP)'' and establish a PM design framework to minimize the SoP based on user studies.

翻译：投影映射（PM）技术能够在不要求用户佩戴头戴式显示器的情况下实现增强现实（AR）体验，并支持多用户交互。该技术被视为一种前景广阔的技术，可应用于远程协作、医疗保健、工业设计、城市规划、艺术创作及办公等多种场景，使用户能够在桌面工作空间中与叠加在增强物体上的内容进行交互。然而，传统PM系统在用户遮挡光路时常出现投影阴影问题。现有采用多个分布式投影仪的方法虽可补偿遮挡，但会因计算处理带来延迟，从而降低用户体验。本研究提出一种合成孔径PM系统，该系统在环境中密集布置数量显著增多的投影仪，无需计算补偿即可为桌面工作空间实现无延迟、无阴影的投影。针对因叠加投影间亚像素错位导致的空间分辨率下降问题，我们开发并验证了一种离线模糊补偿方法，其计算时间与投影仪数量无关。此外，我们证明了无阴影PM在实现PM根本目标——在不引发类投影感知印象的前提下改变材料属性——方面起着关键作用。具体而言，我们将这种感知印象定义为“投影感（SoP）”，并基于用户研究建立了最小化SoP的PM设计框架。