Tatsuo Shiina

Background/Objectives: Dental biofilm formation on prosthetic materials contributes to oral diseases and material degradation. This pilot study evaluated the feasibility of combining time-domain optical coherence tomography (TD-OCT) and non-contact atomic force microscopy (NC-AFM) to characterize biofilm-associated optical and surface changes in dental prosthesis materials following antiseptic treatment. Methods: Acrylic resin, composite resin, and stainless-steel specimens were inoculated with Streptococcus mutans biofilms and exposed to water, Orahex, and Watsons mouthwash. TD-OCT was used to obtain extinction coefficient (EC) and optical thickness measurements, while NC-AFM was performed on Orahex-treated specimens to assess nanoscale surface morphology. EC distributions were analyzed descriptively from valid TD-OCT A-scans. Results: Within the examined specimens, EC distributions varied following biofilm formation and antiseptic treatment, with material-dependent responses. Composite resin exhibited the clearest reduction in EC following Watsons treatment, whereas acrylic resin and stainless-steel specimens showed more variable responses. Physical thickness remained relatively stable, while NC-AFM observations of the Orahex-treated specimens supported the TD-OCT findings by demonstrating corresponding surface morphological changes. Conclusions: This pilot study demonstrates the preliminary feasibility of integrating TD-OCT with NC-AFM for non-destructive evaluation of biofilm-associated optical and surface changes in dental prosthesis materials. The findings are descriptive and exploratory, highlighting the potential of TD-OCT for monitoring prosthetic materials while emphasizing the need for future studies incorporating independent biological replicates and complementary biological validation techniques.

A portable OCT scanner usable for dental applications is designed to be compact (B4 notebook size), lightweight, and capable of DC battery operation, enabling chairside use and mobility in home medical care. TD-OCT faces the challenge of a slower measurement speed compared to SD/SS-OCT. In this study, by utilizing multiple rotating reflectors and combining them with a 3 × 3 fiber coupler, a measurement range of over 10 mm and a measurement speed of 1000 scans per second were achieved. Additionally, the dental intraoral probe was designed to ensure high accessibility, allowing free positioning within the oral cavity, with an ingeniously compact optical system. A cylindrical probe with a diameter of 6 mmϕ and a length of 10 mm was developed to enable tooth measurement. This study demonstrated the capability to evaluate attenuation coefficients derived from material properties, starting with measurements of caries and gums.

Wind measurements in the near-surface region are challenging due to small spatiotemporal scales and strong influence from terrain and man-made structures. To address this issue, a low-coherence Doppler lidar (LCDL) was developed for high-resolution short-range wind measurements. The system uses a low-coherence light source with a coherence length of 1 m, enabling range-selective detection with high spatial resolution. A coaxial optical configuration improved sensitivity by 50 dB compared with the previous system, and the measurement range was estimated to be approximately 20 m. Wind tunnel experiments showed good agreement between the LCDL and an anemometer in the 0–10 m/s range. The system achieved 1 m spatial resolution by sequentially switching measurement ranges. These results demonstrate that the LCDL is a promising technique for high-resolution near-surface wind sensing with potential engineering applications.

Injection molding is essential for mass-producing soft contact lenses, yet molding-induced deformation remains a decisive factor for optical quality. This study systematically evaluated the impact of resin mold design factors (optical zone (OZ) radius of curvature and resin mold thickness) and injection molding parameters (holding pressure and injection speed) on the properties of a dry-state lens (dry lens) using an L18 orthogonal array. The results demonstrated that optimizing the resin mold thickness to 0.9 mm reduced astigmatism by approximately 95%, while high holding pressure and low injection speed improved structural stability. Notably, the findings suggest that the refractive power of the dry lens is more strongly governed by macro-level curvature fluctuations and internal stress distributions arising from the resin mold thickness and shape than by the wavefront aberrations of the resin mold itself. Designs with a smaller radius of curvature (R = 6.5 mm) exhibited substantial power deviations of up to +2.8 D, whereas deviations remained within ±0.2 D for designs with a larger radius of curvature (R = 8.5 mm). For high-precision lens manufacturing, it is indispensable to incorporate a resin mold design that accounts for deformations induced during molding. This study provides comprehensive guidelines for achieving high-quality products by detailing the relationship between injection molding and design.

The use of Vegetation Indices (VIs) is important in remote sensing for inferring biophysical parameters and monitoring environmental processes. Since VIs are derived from reflectance measurements, the scale and platform of acquisition-satellite, commercial multispectral drone, or simulation model—can potentially influence their derived values and inter-relationships. This study addresses this influence by presenting a multiscale comparison of four common indices: MPRI, NDVI, NDWI, and OSAVI. Data were sourced from three distinct platforms: Sentinel-2 satellite imagery, high-resolution data acquired via a multispectral drone, and a simulated spectral library generated using the PROSPECT-4 via ARTMO software. The core objective was to assess the consistency of the correlational structure among these VIs across the three scale measurements. Results indicate a statistically significant similarity in the overall correlational pattern of the indices, suggesting that the intrinsic mathematical relationships between these VIs are largely scale-invariant. However, the study identifies a critical need to standardize the data acquisition and processing protocol for drone measurements to match the known consistency of the Sentinel-2 mission and the rigorous parameters of the PROSPECT-4 simulation. This standardization is essential for future multi-sensor integration and calibration efforts.

Recent advances in molding technology have enabled the fabrication of plastic molded components with complex geometries. In contact lens (CL) manufacturing, a double-sided molding process using resin molds is employed, in which the front and back surfaces of the lens are replicated through injection molding. However, thermal deformation during polymerization can alter the mold shape, thereby affecting the optical characteristics of the final lenses. This study proposes a high-precision optical evaluation method for resin molds used in contact lens (CL) manufacturing, utilizing a reflective wavefront sensor and optical coherence tomography (OCT). The wavefront sensor demonstrated high measurement accuracy (≈1/100λ) and reproducibility (≈1/200λ) as confirmed using reference samples, and yielded values of approximately 0.012–0.015 μm for the resin molds. Five mold designs with radii of curvature ranging from 6.500 to 8.500 mm were evaluated, revealing that Zernike coefficients varied depending on design and thermal treatment conditions. In particular, astigmatism (Z04) and coma aberrations (Z07) exhibited pronounced trends. A strong correlation was also observed between the Zernike coefficient Z07 and the mold thickness asymmetry measured by OCT. When the thickness difference increased by 2.3 times due to thermal treatment, Z07 increased to 1.9 times. In contrast, Z04 showed no consistent trend and exhibited significant variability (standard deviation > 0.5 μm) after polymerization. The proposed method enables precise detection of subtle shape variations and aberrations, providing valuable feedback for optimizing molding conditions and improving the quality of contact lens production. Furthermore, this method can also be applied to the quality evaluation of other optical components.

This study explores the relationship between nutrient concentration (NC) and epidermal thickness (d) of the leaves of hydroponically grown Brassica rapa and its attenuation coefficients (m) using portable Time-Domain Optical Coherence Tomography (TD-OCT), which is a non-invasive imaging technique that uses low-coherence interferometry to generate axial scans of plants’ leaves by measuring the time delay and intensity of backscattered light. The portable TD-OCT system in this study has an axial and lateral resolution of 7 m and 3 m, respectively, a scanning depth of 12 mm, and a 1310 nm Super Luminescent Diode (SLD). Several studies suggest that the differences in d and m are related to nutritional, physiological, and anatomical status. The study used the Kratky method, a simple non-circulating hydroponic system, to cultivate Brassica rapa with varying NC (25%, 50%, 75%, 100% (control), and 125%). Each treatment group used two plants. The TD-OCT sample probe was placed on a fixed holder and was oriented vertically so that light was directed downward onto the leaf’s surface to obtain the depth profile (A-scan). The distance between the probe and the leaf was adjusted to obtain the optimum interference signal. Five averaged A-scans were obtained per leaf on the 7th, 18th, and 21st days post nutrient exposure. The logarithm of the averaged A-scan is linearly fitted to extract m. The results showed a positive correlation between NC and m, which suggests that plants produce more chlorophyll and develop denser cells and increase m. There was no correlation obtained between NC and d. The study demonstrates the potential of TD-OCT as a non-destructive tool for assessing plant health and monitoring growth dynamics in hydroponic systems and m as a sensitive indicator of plant health as compared to d. The continued exploration of TD-OCT applications in agriculture can contribute to improving crop management strategies and promoting sustainable food production practices.

Precision agriculture is one of the emerging technologies that is promising to solve the problem of food insecurity worldwide. These focus on collecting, analyzing, and taking actions based on data available from the crop and its environment. Building low-cost and reliable plant health-related sensors is critical and helpful in the agriculture industry. This study builds a leaf reflectance sensor comprising a white LED source and an S1133 photodiode detector. The angle between the source and detector varied from 30°, 45°, 60°, and 90° to determine the angle at which it would have an optimal reflectance value. The white LED source was connected to a 3-volt and 0.3-ampere power supply, while the S1133 photodiode detector was connected to an oscilloscope to measure the response voltage. Different green intensities were used using an RGB color scheme that imitates the color of the leaf that characterizes its health status. Reflectance intensities were calibrated using white standard reflectance. The result shows that the 45° angle between the source and detector gives the highest R-squared value (R² = 0.958). This study provides an overview of the effects of varying detection angles for crop reflectance sensors that can be used to assess plant health status and help improve crop yield in the agricultural sector.