Occlusion is a crucial visual element in optical see-through (OST) augmented reality, however, implementing occlusion in OST displays while addressing various design trade-offs is a difficult problem. In contrast to the traditional method of using spatial light modulators (SLMs) for the occlusion mask, using photochromic materials as occlusion masks can effectively eliminate diffraction artifacts in see-through views due to the lack of electronic pixels, thus providing superior see-through image quality. However, this design requires UV illumination to activate the photochromic material, which traditionally requires multiple SLMs, resulting in a larger form factor for the system. This paper presents a compact photochromic occlusion-capable OST design using multilayer, wavelength-dependent holographic optical lenses (HOLs). Our approach employs a single digital micromirror display (DMD) to form both the occlusion mask with UV light and a virtual image with visible light in a time-multiplexed manner. We demonstrate our proof-of-concept system on a bench-top setup and assess the appearance and contrasts of the displayed image. We also suggest potential improvements for current prototypes to encourage the community to explore this occlusion approach.
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