Large-aperture optics play key roles in the laser beam transmission processes involved in high-power laser facilities. The microtargets (e.g., contaminants, dust, and particles) adhering to the optical surfaces would greatly affect the optical performance and, thus, need to be accurately detected for evaluating the cleanliness quality of optical components. However, due to the limit of camera resolution (the actual size of the target area on the optics surface represented by a single pixel ranges from 50 to 100 $\mu \text{m}$ ), it is of great challenge to accurately detect the sizes of tiny microtargets (roughly 20 $\mu \text{m}$ ). In this work, a novel subpixel size calibration method based on the regression model and the Mie scattering theory was proposed to precisely calculate the actual sizes of the tiny microtargets. The least-squares support vector machine (LSSVM) principle was applied to establish the area calibration model, and the random sampling consistency (RANSAC) algorithm was applied to optimize the selection of training samples and eliminate the outliers at the same time. The results showed that the relative diameter errors of about 90% of the detected microtargets were less than 30%, which is much better than that of the common pixel-level calibration method. The minimum detectable diameter of the microtargets with the proposed size calibration method can reach $15.8~\mu \text{m}$ , which is much smaller than the resolution ( $53.7~\mu \text{m}$ ) of commercial cameras. A similar high calibration accuracy can be achieved in different regions on the optical surfaces although the illumination conditions were different. The proposed subpixel size calibration method can be applied to detect the microtargets with dimensions as small as 20 $\mu \text{m}$ on the large-aperture reflector surfaces, which would greatly save the cost of detection equipment and improve the detection efficiency.
Abstract Smart windows that incorporate photothermal modulators (PMs) can independently regulate solar transmittance and infrared (IR) emissivity to improve building comfort and reduce energy consumption. Herein, a novel all‐solid‐state variable IR emissivity device (VED) is first designed and fabricated with a high visible irradiation transmittance ( T ′ vis = 0.79) and solar irradiation transmittance ( T ′ sol = 0.75) using an ITO/SiO 2 /ITO Fabry–Perot cavity structure. The VED exhibits different IR emissivity (ɛ) values at positive (ɛ P = 0.80) and negative (ɛ N = 0.38) bias, allowing for dynamic regulation of radiation by controlling the electrical conductivity of the indium tin oxide (ITO) layer. Furthermore, an all‐solid‐state PM with a structure of ITO/SiO 2 /ITO/Glass/ITO/NiO/ZrO 2 /Li/WO 3 /ITO, which is capable of independently regulating solar transmittance (Δ T' sol = 0.31) and IR emissivity (Δɛ 2.5–25 µm = 0.42), is fabricated. The multi‐mode smart window incorporating PMs can achieve “bright,” “dark,” “warm,” and “cool” modes, making them suitable for deployment in diverse climate zones. The innovative smart window holds a massive potential for use in reducing building energy consumption.
Abstract The spraying of citrus to kill insects is a necessary part of the citrus planting process. Most of the currently used sprayers are cover sprays, which cannot achieve accurate and low-consumption spraying. Causing a lot of pesticide waste and environmental pollution. Aiming at the difficulty of precise spraying of citrus leaves, this paper proposes a soft spraying manipulator with good bending characteristics and flexible operation ability. The robotic arm consists of 6 joints and 2 arm segments. The two arm segments of the robotic arm are driven by two wire ropes and move in two orthogonal planes respectively. The PD controller design is designed. The joint state observers are constructed to predict joint angles, angular velocities, and other information. The dynamic simulation experiment is carried out, and the relationship between the wire rope tension and the spring elastic force changes with time, and the relationship between each joint angle changes with time. These make the wire-driven precise spray robotic arm potentially useful in agricultural spraying.
Laser-induced ultrasound scanning imaging is proposed and utilized for the detection of the printed circuit board (PCB) delamination defect in this present study. Initially, based on the principle of laser-induced ultrasound scanning imaging, a three-dimensional mathematical model of the ultrasonic excitation by pulsed laser acting on the surface of PCB is established and analyzed. Furthermore, based on the established laser ultrasonic nondestructive testing system, single-point testing is investigated on the PCB specimen. A-scan experiments were carried out by transmission and reflection approaches, respectively. Moreover, the influence of the signal receiving position on the discrimination of defective signals and the effect of wavelet transform denoising parameters on the signal-to-noise ratio were investigated. Eventually, based on the laser-induced ultrasound scanning imaging inspection system, the defects of simulated debonding flat bottom holes are detected and studied. The different algorithms or parameters (Fast Fourier Transform, variance, extremum, and principal component analysis, etc.) are employed to extract the characteristic information are analyzed. The experimental results are compared with the traditional infrared thermal wave imaging (lock-in thermography). The experimental results indicate that laser-induced ultrasound scanning imaging has the advantages of high-resolution imaging for the defect with a small diameter. Therefore, it is of great significance to study a set of feasible laser-induced ultrasound scanning imaging for PCB delamination defect detection.
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