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Abstract Biodegradable optical waveguides are breakthrough technologies to light delivery and sensing in biomedical and environmental applications. Agar emerges as an edible, soft, low-cost, and renewable alternative to traditional biopolymers, presenting remarkable optical and mechanical characteristics. Previous works introduced agar-made optical fibers for chemical measurements based on their inherent response to humidity and surrounding concentration. Therefore, we propose, for the first time, an all-optical, biodegradable electric current sensor. As flowing charges heat the agar matrix and modulate its refractive index, we connect the optical device to a DC voltage source using pin headers and excite the agar sample with coherent light to project spatiotemporally deviating speckle fields. Experiments proceeded with spheres and no-core fibers comprising 2 wt% agar/water. Once the increasing current stimulates the speckles’ motion, we acquire such images with a camera and evaluate their correlation coefficients, yielding exponential decay-like functions whose time constants provide the input amperage. Furthermore, the light granules follow the polarization of the applied voltage drop, providing visual information about the current direction. The results indicate a maximum resolution of $$\sim $$ ∼ 0.4 $$\upmu $$ μ A for electrical stimuli $$\le $$ ≤ 100 $$\upmu $$ μ A, which fulfills the requirements for bioelectrical signal assessment.

The aim of this paper is to investigate the potential of virtual reality images as a means of reducing pain and fear in children, through the use of projection technology. While body-worn immersive displays have been previously suggested for this purpose, head-mounted displays have been found to be unsuitable due to their lack of interactivity. To address this issue, we propose a simple and cost-effective two-screen projection system that can be installed in a hospital room without interfering with communication and without compromising the immersive experience. By projecting onto screens installed on the wall and floor, an immersive digital space can be created visually. Our experiments, in which we measured $\alpha $ -amylase activity in saliva, showed that the proposed two-screen projection significantly reduced stress levels in healthy adults when compared to one-screen projection. Additionally, we conducted an experiment using the KOKORO scale as a subjective measure, which revealed that children with medical complexity experienced a significant reduction in stress levels after viewing the two-screen projection compared to before viewing. These findings suggest that the proposed system could serve as an ideal distraction in pediatric nursing, thereby providing much-needed nursing support to children and their families.

Sign language is designed as a natural communication method to convey messages among the deaf community. In the study of sign language recognition through wearable sensors, the data sources are limited, and the data acquisition process is complex. This research aims to collect an American sign language dataset with a wearable inertial motion capture system and realize the recognition and end-to-end translation of sign language sentences with deep learning models. In this work, a dataset consisting of 300 commonly used sentences is gathered from 3 volunteers. In the design of the recognition network, the model mainly consists of three layers: convolutional neural network, bi-directional long short-term memory, and connectionist temporal classification. The model achieves accuracy rates of 99.07% in word-level evaluation and 97.34% in sentence-level evaluation. In the design of the translation network, the encoder-decoder structured model is mainly based on long short-term memory with global attention. The word error rate of end-to-end translation is 16.63%. The proposed method has the potential to recognize more sign language sentences with reliable inertial data from the device.

Recently, methods of projecting images onto food using a projector have been the subject of various studies because they have the potential to intervene in the visual appreciation of food, and also because such technology has the potential to create new production methods and services related to food. Since projection can be achieved easily using an optical marker, an edible retroreflector made of agar has been proposed; however, an agar retroreflector had the drawback of a short lifetime. In this paper, we propose an edible retroreflector made of candy, which is resistant to drying and can be used for a long time. Two types of retroreflectors, one with single layer and the other with two layers, were proposed and fabricated. The evaluation experiments showed that the proposed retroreflectors had sufficient reflection coefficient $R$ of up to 84.76 for the single-layered prototype and up to 173.05 for the two-layered prototype. These coefficients are comparable to the coefficient 70 of commercially available glass-bead-type retroreflectors, which are strong enough to be used as markers for a camera. The prototype was also able to maintain its functionality for 10 days from the fixed-point observation. Furthermore, dynamic projection mapping on a pancake and motion capture were successfully demonstrated to show the potential applications.

We propose a miniature rotating mirror system using a micro-ultrasonic motor that employs a 45° angle mirror as its rotor for enlarging the angle of view of cameras. The motor assy, measuring 2 mm in diameter and 4 mm in length, is one of the smallest motors and is expected for medical applications such as endoscopes. In this paper, we build a micromirror assembly, install it into a visual feedback system with an optical system, and demonstrate a motor control with a quick and wide angle-of-view observation. The high-speed camera vision embedded in the system measures the quick motion of the motor in real-time and enables accurate positioning of the mirror angle by p-control using burst waves. The proposed system demonstrates the visual feedback control of the miniature rotating mirror to the angle information obtained by the high-speed camera. The feasibility of the mirror system driven by the micro-ultrasonic motor is shown via demonstration.

We developed a temporally coded exposure (TeCE) camera that can cope with high-speed focus variations of a tunable acoustic gradient index (TAG) lens. The TeCE camera can execute a very short exposure multiple times at an arbitrary timing during one shot. Furthermore, by accumulating the photoelectrons generated by each exposure, it is possible to maintain the brightness even with a short exposure time. By synchronously driving the TeCE camera and the TAG lens, different focal planes of an observation target can be acquired at high speed. As a result, high-speed three-dimensional measurement becomes possible, and this can be used for feedback of three-dimensional information. In the work described in this paper, we conducted a focus tracking experiment to evaluate the feedback performance of the TeCE camera. From the experimental results, we confirmed the feedback capability of the TeCE camera.