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Tremor is a movement disorder that significantly impacts an individual’s physical stability and quality of life, and conventional medication or surgery often falls short in providing a cure. Rehabilitation training is, therefore, used as an auxiliary method to mitigate the exacerbation of individual tremors. Video-based rehabilitation training is a form of therapy that allows patients to exercise at home, reducing pressure on rehabilitation institutions’ resources. However, it has limitations in directly guiding and monitoring patients’ rehabilitation, leading to an ineffective training effect. This study proposes a low-cost rehabilitation training system that utilizes optical see-through augmented reality (AR) technology to enable tremor patients to conduct rehabilitation training at home. The system provides one-on-one demonstration, posture guidance, and training progress monitoring to achieve an optimal training effect. To assess the system’s effectiveness, we conducted experiments comparing the movement magnitudes of individuals with tremors in the proposed AR environment and video environment, while also comparing them with standard demonstrators. Participants wore a tremor simulation device during uncontrollable limb tremors, with tremor frequency and amplitude calibrated to typical tremor standards. The results showed that participants’ limb movement magnitudes in the AR environment were significantly higher than those in the video environment, approaching the movement magnitudes of the standard demonstrators. Hence, it can be inferred that individuals receiving tremor rehabilitation in the AR environment experience better movement quality than those in the video environment. Furthermore, participant experience surveys revealed that the AR environment not only provided a sense of comfort, relaxation, and enjoyment but also effectively guided them throughout the rehabilitation process.

An optical see-through head-mounted display (OST-HMD) can potentially improve the safety and accuracy of ultrasonography (US)-guided fine-needle aspiration. We aimed to evaluate the usefulness of an OST-HMD in US-guided needle-puncture procedures. We conducted a prospective randomized controlled study in which we compared the accuracy and safety of the US-guided needle puncture procedure and the stress on the practitioner when using OST-HMD versus standard US display (SUD). Inexperienced medical students were enrolled and randomly divided into two groups. A breast phantom was used to evaluate the required time and accuracy of the US-guided needle puncture. Practitioner stress was quantified using a visual analog scale (VAS). When the procedure was performed for the first time, the time required to reach the target lesion at a shallow depth was significantly shorter in the OST-HMD group (39.8 ± 39.9 s) than in the SUD group (71.0 ± 81.0 s) (p = 0.01). Using the OST-HMD significantly reduced the unintentional puncture of a non-target lesion (p = 0.01). Furthermore, the stress felt by the practitioners when capturing the image of the target lesion (p < 0.001), inserting and advancing the needle more deeply (p < 0.001), and puncturing the target lesion (p < 0.001) was significantly reduced in the OST-HMD group compared with that in the SUD group. Use of OST-HMD may improve the accuracy and safety of US-guided needle puncture procedures and may reduce practitioner stress during the procedure.

Virtual reality (VR) and augmented reality (AR) have found widespread applications in education, engineering, healthcare, and entertainment. However, these near-eye displays are often bulky and heavy, and thus are not suitable for long-term wearing. Metalenses, with an ultra-thin formfactor, subwavelength modulation scale, and high modulation flexibility, are promising candidates to replace the conventional optics in AR display systems. In this work, we proposed and fabricated a novel reflective dielectric metalens-visor based on Pancharatnam-Berry phase with see-through capability. It achieves diffraction-limited focusing behavior for the reflected red light, while keeping a good transmission spectrum in the visible region. Hence, this single piece metalens-visor can perform the function of two integrated elements simultaneously: an eyepiece and an optical combiner, which in turn greatly reduces the weight and the size of an AR display. We have implemented a proof-of-concept AR display system employing the metalens-visor, and experimentally demonstrated color AR images with good image quality. This work reveals the great potential of multi-functional metasurface devices which enables optical integration in interdisciplinary applications including wearable displays, biological imaging, and aeronautic optical instruments.

Augmented reality (AR) Head-Mounted Displays (HMDs) are emerging as the most efficient output medium to support manual tasks performed under direct vision. Despite that, technological and human-factor limitations still hinder their routine use for aiding high-precision manual tasks in the peripersonal space. To overcome such limitations, in this work, we show the results of a user study aimed to validate qualitatively and quantitatively a recently developed AR platform specifically conceived for guiding complex 3D trajectory tracing tasks. The AR platform comprises a new-concept AR video see-through (VST) HMD and a dedicated software framework for the effective deployment of the AR application. In the experiments, the subjects were asked to perform 3D trajectory tracing tasks on 3D-printed replica of planar structures or more elaborated bony anatomies. The accuracy of the trajectories traced by the subjects was evaluated by using templates designed ad hoc to match the surface of the phantoms. The quantitative results suggest that the AR platform could be used to guide high-precision tasks: on average more than 94% of the traced trajectories stayed within an error margin lower than 1 mm. The results confirm that the proposed AR platform will boost the profitable adoption of AR HMDs to guide high precision manual tasks in the peripersonal space.

In robot-assisted laparoscopic surgery, the first assistant (FA) is responsible for tasks such as robot docking, passing necessary materials, manipulating hand-held instruments, and helping with trocar planning and placement. The performance of the FA is critical for the outcome of the surgery. The authors introduce ARssist, an augmented reality application based on an optical see-through head-mounted display, to help the FA perform these tasks. ARssist offers (i) real-time three-dimensional rendering of the robotic instruments, hand-held instruments, and endoscope based on a hybrid tracking scheme and (ii) real-time stereo endoscopy that is configurable to suit the FA's hand–eye coordination when operating based on endoscopy feedback. ARssist has the potential to help the FA perform his/her task more efficiently, and hence improve the outcome of robot-assisted laparoscopic surgeries.

A Mixed Reality (MR) application using an optical see-through headset was developed to assess short-term spatial memory. A study with 29 participants was conducted. Data from this study were compared to two previous studies using mobile Augmented Reality (AR) and Virtual Reality (VR) with headsets. When comparing the three technologies (MR, AR, VR) for the performance variables, there were no statistically significant differences for either the total number of correctly placed objects or the total number of attempts. However, the MR application required more time than the AR and VR applications in the evaluation phase and more time than the VR application in the learning phase. Our arguments for the longer time are the novelty of the MR application for the participants and the characteristics of the applications. The key results from the MR study include the following: (1) the objects used in the MR application were correctly positioned on a map, which implies that the memory acquired with the MR application is effectively transferred to the user’s mental map; (2) for the performance variables, there were no significant differences in the results by gender; (3) and the usability rating decreased with computer experience. The results show that the MR application is effective for spatial memory assessment and was well rated by the participants. The three technologies, along with suitable hardware, are effective for spatial memory assessment. However, MR using optical see-through headsets offers advantages over mobile AR and VR using headsets, discussed in this publication.

This study investigates ambient-light–induced image-quality degradation in optical see-through (OST) displays and presents a perceptually driven enhancement method. Luma and chroma of input images are adjusted via power-law transformations to compensate for contrast loss and chroma reduction caused by additive mixing with ambient light. The adjustment parameters were empirically derived through psychophysical experiments and modeled using ambient light level (SR, %) and average image luma. Experimental results show that the proposed adjustment significantly improves perceived image quality across various OST viewing conditions. Analysis of observer feedback reveals that preferences are not driven by a simple maximization of brightness. Instead, the selections are guided by specific qualitative criteria, such as maintaining readability in dark regions, preserving highlight textures, and balancing light–dark organization for depth cues. These findings suggest that effective OST image compensation requires an approach that prioritizes these perceptual factors over global intensity adjustments.

For vivid, immersive overlay of virtual images onto background scenes in augmented reality (AR) applications, it is crucial for the display element to achieve controllability of spectral selectivity and transmittance level. At the current stage, the transmittance of self-emissive transparent displays is limited to at most ∼60 %, constrained by the fill factor of emissive regions, restricting their scalability for immersive experiences. Although projection-based transparent screens using frequency-selective scatterers offer a promising alternative, the platforms suffer from spectral broadening and instability originating from color-dependent scattering and inter-scatterer coupling. Here, we present a transparent screen architecture based on multicolor nanoring arrays. By tuning the nanoring’s resonance via inner-aperture size engineering, the architecture enables dense, symmetric RGB arrays with isolated and homogenized scattering responses. For inter-scatterer distances of 100–200+ nm, full-wave simulations confirm the robustness of well-isolated RGB reflections (FWHM < 25 nm), along with exceptional tunability of transmittance (50 % to above 80 %). As a platform for AR displays, we demonstrate the widest reported transparency-control range without any penalty to color balance or spectral selectivity. We also analyze the gamut area of projected images across transmittance levels, achieving a net gamut expansion (+11.0 % p at Λ = 120 nm; +5.5 % p at Λ = 190 nm) from the spectral narrowing of projection sources, and further propose a practical design map linking the maximum allowable transmittance to the ambient-to-source noise ratio. Our nanoring-based architecture provides a robust and scalable platform for next-generation transparent displays under real-world lighting conditions.

In order to align the virtual and real content precisely through augmented reality devices, especially in optical see-through head-mounted displays (OST-HMD), it is necessary to calibrate the device before using it. However, most existing methods estimated the parameters via 3D-2D correspondences based on the 2D alignment, which is cumbersome, time-consuming, theoretically complex, and results in insufficient robustness. To alleviate this issue, in this paper, we propose an efficient and simple calibration method based on the principle of directly calculating the projection transformation between virtual space and the real world via 3D-3D alignment. The proposed method merely needs to record the motion trajectory of the cube-marker in the real and virtual world, and then calculate the transformation matrix between the virtual space and the real world by aligning the two trajectories in the observed view. There are two advantages associated with the proposed method. First, the operation is simple. Theoretically, the user only needs to perform four alignment operations for calibration without changing the rotation variation. Second, the trajectory can be easily distributed throughout the entire observation view, resulting in more robust calibration results. To validate the effectiveness of the proposed method, we conducted extensive experiments on our self-built optical see-through head-mounted display (OST-HMD) device. The experimental results show that the proposed method can achieve better calibration results than other calibration methods.

Augmented reality (AR) is a new technology that provides new awareness by using a computer to extend the real environment perceived by humans. Optical see-through head-mounted displays (OST-HMD) are worn on the head and can faithfully generate an AR image by wearing the device on the head as a spectacle-type device. We developed an ultrasound-guided needle biopsy technique using OST-HMD for breast tumors. Moverio BT-35E (Seiko Epson Corp, Nagano, Japan) was used as the OST-HMD device. This technique involves performing needle biopsy under direct vision via the gap at the bottom of the display while the ultrasound images are projected on the display of the OST-HMD worn on the head. With this technique, needle biopsy can be executed smoothly with no posture restrictions. A flip shade affixed to the OST-HMD has 2% transmittance, which enables clearer projection of the images. This article outlines the ultrasound-guided needle biopsy using OST-HMD. We established a safe and accurate biopsy technique with technological innovations using AR.