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Ubiquitous throughout the history of photography, white borders on photo prints and vintage Polaroids remain useful as new technologies including augmented reality emerge for general use. In contemporary optical see-through augmented reality (OST-AR) displays, physical transparency limits the visibility of dark stimuli. However, recent research shows that simple image manipulations, white borders and outer glows, have a strong visual effect, making dark objects appear darker and more opaque. In this work, the practical value of known, inter-related effects including lightness induction, glare illusion, Cornsweet illusion, and simultaneous contrast are explored. The results show promising improvements to visibility and visual quality in future OST-AR interfaces. 

Optical see-through Augmented Reality (OST-AR) is a developing technology with exciting applications including medicine, industry, education, and entertainment. OST-AR creates a mix of virtual and real using an optical combiner that blends images and graphics with the real-world environment. Such an overlay of visual information is simultaneously futuristic and familiar: like the sci-fi navigation and communication interfaces in movies, but also much like banal reflections in glass windows. OSTAR’s transparent displays cause background bleed-through, which distorts color and contrast, yet virtual content is usually easily understandable. Perceptual scission, or the cognitive separation of layers, is an important mechanism, influenced by transparency, depth, parallax, and more, that helps us see what is real and what is virtual. In examples from Pepper’s Ghost, veiling luminance, mixed material modes, window shopping, and today’s OST-AR systems, transparency and scission provide surprising – and ordinary – results. Ongoing psychophysical research is addressing perceived characteristics of color, material, and images in OST-AR, testing and harnessing the perceptual effects of transparency and scission. Results help both understand the visual mechanisms and improve tomorrow’s AR systems. 

Augmented reality (AR) combines elements of the real world with additional virtual content, creating a blended viewing environment. Optical see-through AR (OST-AR) accomplishes this by using a transparent beam splitter to overlay virtual elements over a user’s view of the real world. However, the inherent see-through nature of OST-AR carries challenges for color appearance, especially around the appearance of darker and less chromatic objects. When displaying human faces—a promising application of AR technology—these challenges disproportionately affect darker skin tones, making them appear more transparent than lighter skin tones. Still, some transparency in the rendered object may not be entirely negative; people’s evaluations of transparency when interacting with other humans in AR-mediated modalities are not yet fully understood. In this work, two psychophysical experiments were conducted to assess how people evaluate OST-AR transparency across several characteristics including different skin tones, object types, lighting conditions, and display types. The results provide a scale of perceived transparency allowing comparisons to transparency for conventional emissive displays. The results also demonstrate how AR transparency impacts perceptions of object preference and fit within the environment. These results reveal several areas with need for further attention, particularly regarding darker skin tones, lighter ambient lighting, and displaying human faces more generally. This work may be useful in guiding the development of OST-AR technology, and emphasizes the importance of AR design goals, perception of human faces, and optimizing visual appearance in extended reality systems. 

As we gather in the City of Light, consider that everything visible is light. We, color and imaging scientists and practitioners, are masters of light, reproducing light through imaging, creating and utilizing light in our real environment, and augmenting our illuminated reality with advanced displays and optics. Imaging, a core topic of CIC, is about the reproduction of light, which is foremost a question of tone and color reproduction, and we develop and master technologies from reflective pigments to emissive displays. Reality itself is rendered and sensed with light, and as we choose to light our environment with LED illumination, color rendition is a central question for visual quality. Reality and imaging converge in augmented reality – AR – which can insert interactive imagery into our illuminated world. In AR, this mix of real and augmented reveals important questions about adaptation and color perception. Mastering light in real and augmented reality incorporates the newest, evolving technologies, while we rely on the foundations of our predecessors: both the intuitive artists whose paintings we still admire, and the rational scientists whose findings we still trust. 

Head‐mounted virtual reality (VR) and augmented reality (AR) systems deliver colour imagery directly to a user's eyes, presenting position‐aware, real‐time computer graphics to create the illusion of interacting with a virtual world. In some respects, colour in AR and VR can be modelled and controlled much like colour in other display technologies. However, it is complicated by the optics required for near‐eye display, and in the case of AR, by the merging of real‐world and virtual visual stimuli. Methods have been developed to provide predictable colour in VR, and ongoing research has exposed details of the visual perception of real and virtual in AR. Yet, more work is required to make colour appearance predictable and AR and VR display systems more robust. 

Optical see-through AR presents virtual objects to a user through a transparent display that blends them with the real-world environment. This is simultaneously novel and familiar: beam splitters have been used for ghostly visual effects, and yet the mechanism is exactly the same as the reflections in an everyday window. The history of theatrical visual effects leads through a series of vision science experiments and now to research on the perception of transparent AR systems. Still, there is a tension in the perception of AR stimuli: users of AR seem to be able to separate, or scission, the layers of virtual and real, depending on their understanding of the scene and its visual characteristics. 

As the development of extended reality technologies bring us closer to what some call the metaverse, it is valuable to investigate how our perception of color translates from physical, reflective objects to emissive and transparent virtual renderings. Colorimetry quantifies color stimuli and color differences, and color appearance models account for adaptation and illuminance level. However, these tools do not extent satisfactorily to the novel viewing experiences of extended reality. Ongoing research aims to understand the perception of layered virtual stimuli in optical see-through augmented reality with the goal of improving or extending color appearance models. This will help ensure robust, predictable color reproduction in extended reality experiences.