Yuichi Hiroi

Visual guidance (VG) plays an essential role in directing user attention in virtual reality (VR) and augmented reality (AR) environments. However, traditional approaches rely on explicit visual annotations, which often compromise visual clarity and increase user cognitive load. To address this issue, we propose an unobtrusive VG technique based on color vibration, a phenomenon in which rapidly alternating colors at frequencies above 25 Hz are perceived as a single intermediate color. Our work explores a perceptual state that exists between complete color fusion and visible flicker, where color differences remain detectable without conscious awareness of vibration. Through two experimental studies, we first identified the thresholds separating complete fusion, this intermediate perceptual state, and visible flicker by systematically varying color vibration parameters. Subsequently, we applied color vibrations with derived thresholds to natural image regions and validated their attention-guiding capabilities using eye-tracking measurements. The results demonstrate that controlled color vibration successfully directs user attention while maintaining low cognitive demand, providing an effective method for implementing unobtrusive VG in VR and AR systems.

Light Attenuation Displays (LADs) are a type of Optical See-Through Head-Mounted Display (OST-HMD) that present images by attenuating incoming light with a pixel-wise polarizing color filter. Although LADs can display images in bright environments, there is a trade-off between the number of Spatial Light Modulators (SLMs) and the color gamut and contrast that can be expressed, making it difficult to achieve both high-fidelity image display and a small form factor. To address this problem, we propose StainedSweeper, a LAD that achieves both the wide color gamut and the variable intensity with a single SLM. Our system synchronously controls a pixel-wise Digital Micromirror Device (DMD) and a nonpixel polarizing color filter to pass light when each pixel is the desired color. By sweeping this control at high speed, the human eye perceives images in a time-multiplexed, integrated manner. To achieve this, we develop the OST-HMD design using a reflective Solc filter as a polarized color filter and a color reproduction algorithm based on the optimization of the time-multiplexing matrix for the selected primary color filters. Our proof-of-concept prototype showed that our single SLM design can produce subtractive images with variable contrast and a wider color gamut than conventional LADs.

Existing near-eye displays (NEDs) have trade-offs related to size, weight, computational resources, battery life, and body temperature. A recent paradigm, beaming display, addresses these trade-offs by separating the NED into a steering projector (SP) for image presentation and a passive headset worn by the user. However, the beaming display has issues with the projection area of a single SP and has severe limitations on the head orientation and pose that the user can move. In this study, we distribute dual steering projectors in the scene to extend the head orientation and pose of the beaming display by coordinating the dual projections on a passive headset. For cooperative control of each SP, we define a geometric model of the SPs and propose a calibration and projection control method designed for multiple projectors. We present implementations of the system along with evaluations showing that the precision and delay are 1.8 ∼ 5.7 mm and 14.46 ms, respectively, at a distance of about 1 m from the SPs. From this result, our prototype with multiple SPs can project images in the projection area (20 \textmm \times 30 \textmm) of the passive headset while extending the projectable head orientation. Furthermore, as applications of cooperative control by multiple SPs, we show the possibility of multiple users, improving dynamic range and binocular presentation.

Light Attenuation Displays (LADs), a subset of Optical See-Through Head-Mounted Displays (OST-HMDs), enable image display in bright environments by filtering incident light at the pixel level. Although recent methods have proposed single-DMD light attenuation, they do not consider additive color display and background compensation, limiting their applicability in real-world scenarios. We present FactoredSweeper, a single digital micromirror device (DMD) system that incorporates both light attenuation and addition. By synchronizing the DMD, color filter, and light source, our system generates an additive virtual image, light attenuation, and occlusion through time multiplexing. To produce the target image while compensating for the background, we optimize time-multiplexed binary DMD patterns and LED/color filter schedules using perceptually-driven non-negative matrix factorization. Simulations and prototypes demonstrate that our integrated attenuation-addition single-SLM system achieves superior dynamic range and perceptual image quality compared to conventional occlusion-capable OST-HMDs using grayscale occlusion masks.

This paper presents a low-latency Beaming Display system with a 133 μ\mathrms motion-to-photon (M2P) latency, the delay from head motion to the corresponding image motion. The Beaming Display represents a recent near-eye display paradigm that involves a steerable remote projector and a passive wearable headset. This system aims to overcome typical trade-offs of Optical See-Through Head-Mounted Displays (OST-HMDs), such as weight and computational resources. However, since the Beaming Display projects a small image onto a moving, distant viewpoint, M2P latency significantly affects displacement. To reduce M2P latency, we propose a low-latency Beaming Display system that can be modularized without relying on expensive high-speed devices. In our system, a 2D position sensor, which is placed coaxially on the projector, detects the light from the IR-LED on the headset and generates a differential signal for tracking. An analog closed-loop control of the steering mirror based on this signal continuously projects images onto the headset. We have implemented a proof-of-concept prototype, evaluated the latency and the augmented reality experience through a user-perspective camera, and discussed the limitations and potential improvements of the prototype.

This paper proposes focal surface occlusion to provide focal cues of occlusion masks for multiple virtual objects at continuous depths in an occlusion-capable optical see-through head-mounted display. A phase-only spatial light modulator (PSLM) that acts as a dynamic free-form lens is used to conform the focal surface of an occlusion mask to the geometry of the virtual scene. To reproduce multiple and continuous focal blurs while reducing the distortion of the see-through view, an optical design based on afocal optics and edge-based optimization to exploit a property of the occlusion mask is established. The prototype with the PSLM and transmissive liquid crystal display can reproduce the focus blur of occluded objects at multiple and continuous depths with a field of view of 14.6°.

We present DehazeGlasses, a see-through visual haze removal system that optically dehazes the user’s field of vision. Human vision suffers from a degraded view due to aspects of the scene environment, such as haze. Such degradation may interfere with our behavior or judgement in daily tasks. We focus on hazy scenes as one common degradation source, which whitens the view due to certain atmospheric conditions. Unlike typical computer vision systems that process recorded images, we aim to realize a see-through glasses system that can optically manipulate our field of view to dehaze the perceived scene. Our system selectively modulates the intensity of the light entering the eyes via occlusion-capable optical see-through head-mounted displays (OST-HMD). We built a proof-of-concept system to evaluate the feasibility of our haze removal method by combining a digital micromirror device (DMD) and an OST-HMD, and tested it with a user-perspective viewpoint camera. A quantitative evaluation with 80 scenes from a haze removal dataset shows that our system realizes a dehazed view that is significantly closer to the ground truth scene compared to the native view under a perceptual image similarity metric. This evaluation shows that our system achieves perceptually natural haze removal while maintaining the see-through view of actual scenes.

Brightness adaptation is a fundamental ability in human visual system, and adjusts various levels of darkness and light. While this ability is continuously used, and it can mostly handle sudden lighting changes in the environment, the adaptation could still take several minutes. Moreover, during the adaptation, the color perception changes as well. This slow reactivity and perception change of the eyes could lead to mistakes for tasks performed in dazzling or temporally high-contrast environments such as when driving into the sun or during a welding process.We present AdaptiVisor, a vision augmentation system that assists the brightness adaptation of the eye. Our system selectively modulates the intensity of the light coming into the eyes via occlusion-capable Optical See-Through Head-Mounted Displays (OST-HMD). An integrated camera captures highlights and brightness in the environment via high-dynamic range capture, and our display system selectively dims or enhances part of field of views so that the user would not perceive rapid brightness changes. We build a proof-of-concept system to evaluate the feasibility of the adaptation assistance by combining a transmissive LCD panel and an OST-HMD, and test it with a user-perspective, view-point camera. The evaluation shows that the system decreases the overexposed area in a scene to 1/15th, and enhances the color by reducing majorly underexposed area to half. We also include a preliminary user trial and it indicates that the system also works for real eyes for the HMD part and to some extent for the LCD.