A Coupled Calibration Method for Dual Cameras-Projector System with Sub-Pixel Accuracy Feature Extraction.

Binocular structured light systems are widely used in 3D measurements. In the condition of complex and local highly reflective scenes, to obtain more 3D information, binocular systems are usually divided into two pairs of devices, each having a Single Camera and a Projector (SCP). In this case, the binocular system can be seen as Dual Cameras-Projector (DCP) system. In the DCP calibration, the Left-SCP and Right-SCP need to be calibrated separately, which leads to inconsistent parameters for the same projector, thus reducing the measurement accuracy. To solve this problem and improve manoeuvrability, a coupled calibration method using an orthogonal phase target is proposed. The 3D coordinates on a phase target are uniquely determined by the binocular camera in DCP, rather than being calculated separately in each SCP. This ensures the consistency of the projector parameters. The coordinates of the projector image plane are calculated through the unwrapped phase, while the parameters are calibrated by the plane calibration method. In order to extract sub-pixel accuracy feature points, a method based on polynomial fitting using an orthogonal phase target is exploited. The experimental results show that the reprojection error of our method is less than 0.033 pixels, which improves the calibration accuracy.

Pressure-Induced Remarkable Spectral Red-Shift in Mn2+ -Activated NaY9 (SiO4 )6 O2 Red-Emitting Phosphors for High-Sensitive Optical Manometry.

To settle the low sensitivity of luminescent manometers, the Mn2+ -activated NaY9 (SiO4 )6 O2 red-emitting phosphors with splendid pressure sensing performances are developed. Excited by 408 nm, the resulting products emit bright red emission originating from 4 T1 (4 G) → 6 A1 transition of Mn2+ , in which the optimal concentration of the activator ion is ≈1 mol%. Moreover, the admirable thermal stability of the developed phosphors is studied and confirmed by the temperature-dependent emission spectra, based on which the activation energy is derived to be 0.275 eV. By analyzing the pressure-dependent Raman spectra, the structural stability of the synthesized compounds at extreme conditions is verified. Furthermore, the designed phosphors exhibit remarkable spectral red-shift at elevated pressure. Especially, as pressure increases from 0.75 to 7.16 GPa, the emission band centroid shifts from 617.2 to 663.4 nm, resulting in a high sensitivity (dλ/dP) of 7.00 nm GPa-1 , whereas the full width at half maximum (FWHM) increases from 83.0 to 110.6 nm, leading to the ultra-high sensitivity (dFWHM/dP) of 10.13 nm GPa-1 . These achievements manifest that the designed red-emitting phosphors are appropriate for ultrasensitive optical manometry. More importantly, the developed manometer is a current global leader in sensitivity, when operating in the band-width mode, that is, FWHM.

Tailoring the Interface with a Multifunctional Ligand for Highly Efficient and Stable FAPbI3 Perovskite Solar Cells and Modules.

Perovskite solar cells (PeSCs) using FAPbI3 perovskite films often exhibit unfavorable phase transitions and defect-induced nonradiative interfacial recombination, resulting in considerable energy loss and impairing the performance of PeSCs in terms of efficiency, stability, and hysteresis. In this work, a facile interface engineering strategy to control the surface structure and energy-level alignment of perovskite films by tailoring the interface between the FAPbI3 film and hole-transporting layer using 4-hydroxypicolinic acid (4HPA) is reported. According to density functional theory studies, 4HPA has prominent electron delocalization distribution properties that enable it to anchor to the perovskite film surface and facilitate charge transfer at the interface. By enabling multiple bonding interactions with the perovskite layer, including hydrogen bonds, PbO, and PbN dative bonds, 4HPA passivation significantly reduces the trap density and efficiently suppresses nonradiative recombination. The obtained perovskite films exhibit superior optoelectronic properties with improved crystallinity, pure α-phase FAPbI3 , and favorable energy band bending. Following this strategy, 4HPA post-treatment PeSCs achieve a champion power conversion efficiency of 23.28% in 0.12 cm2 cells and 19.26% in 36 cm2 modules with excellent environmental and thermal stabilities.

Sandwich-Structured Sn4P3@MXene Hybrid Anodes with High Initial Coulombic Efficiency for High-Rate Lithium-Ion Batteries.

The high theoretical capacity makes metal phosphides appropriate anode candidates for Li-ion batteries, but their applications are restricted due to the limited structural instability caused by the huge volume change, as in other high-capacity materials. Here, we design an integrated electrode consisting of Sn4P3 nanoparticles sandwiched between transition-metal carbide (MXene) nanosheets. Tetramethylammonium hydroxide (TMAOH) plays an essential role in the formation of such sandwich structures by producing negatively charged MXene sheets with expanded layer spacings. The strong C-O-P oxygen bridge bond enables tight anchoring of Sn4P3 nanoparticles on the surface of MXene layers. The obtained Sn4P3-based nanocomposites exhibit high reversible capacity with an initial Coulombic efficiency of 82% and outstanding rate performance (1519 mAh cm-3 at a current density of 5 A g-1). The conductive and flexible MXene layers on both sides of Sn4P3 nanoparticles provide the desired electric conductivity and elastomeric space to accommodate the large volume change of Sn4P3 during lithiation. Therefore, the Sn4P3@MXene hybrid exhibits an enhanced cyclic performance of 820 mAh g-1 after 300 cycles at a current density of 1 A g-1.

Fringe Phase-Shifting Field Based Fuzzy Quotient Space-Oriented Partial Differential Equations Filtering Method for Gaussian Noise-Induced Phase Error.

Traditional filtering methods only focused on improving the peak signal-to-noise ratio of the single fringe pattern, which ignore the filtering effect on phase extraction. Fringe phase-shifting field based fuzzy quotient space-oriented partial differential equations filtering method is proposed to reduce the phase error caused by Gaussian noise while filtering. First, the phase error distribution that is caused by Gaussian noise is analyzed. Furthermore, by introducing the fringe phase-shifting field and the theory of fuzzy quotient space, the modified filtering direction can be adaptively obtained, which transforms the traditional single image filtering into multi-image filtering. Finally, the improved fourth-order oriented partial differential equations with fidelity item filtering method is established. Experiments demonstrated that the proposed method achieves a higher signal-to-noise ratio and lower phase error caused by noise, while also retaining more edge details.

Adaptive Binocular Fringe Dynamic Projection Method for High Dynamic Range Measurement.

Three-dimensional measurement with fringe projection sensor has been commonly researched. However, the measurement accuracy and efficiency of most fringe projection sensors are still seriously affected by image saturation and the non-linear effects of the projector. In order to solve the challenge, in conjunction with the advantages of stereo vision technology and fringe projection technology, an adaptive binocular fringe dynamic projection method is proposed. The proposed method can avoid image saturation by adaptively adjusting the projection intensity. Firstly, the flowchart of the proposed method is explained. Then, an adaptive optimal projection intensity method based on multi-threshold segmentation is introduced to adjust the projection illumination. Finally, the mapping relationship of binocular saturation point and projection point is established by binocular transformation and left camera-projector mapping. Experiments demonstrate that the proposed method can achieve higher accuracy for high dynamic range measurement.

One-dimensional angular-measurement-based stitching interferometry.

In this work, we present one-dimensional stitching interferometry based on the angular measurement for high-precision mirror metrology. The tilt error introduced by the stage motion during the stitching process is measured by an extra angular measurement device. The local profile measured by the interferometer in a single field of view is corrected using the measured angle before the piston adjustment in the stitching process. Comparing to the classical software stitching technique, the angle measuring stitching technique is more reliable and accurate in profiling mirror surface at the nanometer level. Experimental results demonstrate the feasibility of the proposed stitching technique. Based on our measurements, the typical repeatability within 200 mm scanning range is 0.5 nm RMS or less.

Spectral and energy transfer in Bi3+-Ren+ (n = 2, 3, 4) co-doped phosphors: extended optical applications.

Bismuth with [Xe]4f145d106s26p3 electronic configuration is considered as 'a wonder metal' due to its diverse oxidation states and multi-type electronic structures. This review article summarizes the spectral properties of phosphors doped with Bi3+ or co-doped with Bi3+-Ren+ (n = 2, 3, 4), and highlights the critical role of Bi3+ in spectral modification. The energy transfer processes are discussed in detail, including (1) Bi3+ and metal-to-metal charge, (2) Bi3+ and tetravalent cation, (3) Bi3+ and trivalent cation, (4) Bi3+ and divalent cation, and (5) Bi3+ and two kinds of rare earth ions. The most important results obtained in each case are summarized, and the emerging challenges and future development of Bi3+-doped phosphors are discussed. We introduce a method for spectral modification based on the energy transfer between Bi3+ and other cations, with the perspective of development and application in the fields of phosphors, telecommunication, optical temperature sensing, biomedicine, and lasers.

Zonal wavefront reconstruction in quadrilateral geometry for phase measuring deflectometry.

There are wide applications for zonal reconstruction methods in slope-based metrology due to its good capability of reconstructing the local details on surface profile. It was noticed in the literature that large reconstruction errors occur when using zonal reconstruction methods designed for rectangular geometry to process slopes in a quadrilateral geometry, which is a more general geometry with phase measuring deflectometry. In this work, we present a new idea for the zonal methods for quadrilateral geometry. Instead of employing the intermediate slopes to set up height-slope equations, we consider the height increment as a more general connector to establish the height-slope relations for least-squares regression. The classical zonal methods and interpolation-assisted zonal methods are compared with our proposal. Results of both simulation and experiment demonstrate the effectiveness of the proposed idea. In implementation, the modification on the classical zonal methods is addressed. The new methods preserve many good aspects of the classical ones, such as the ability to handle a large incomplete slope dataset in an arbitrary aperture, and the low computational complexity comparable with the classical zonal method. Of course, the accuracy of the new methods is much higher when integrating the slopes in quadrilateral geometry.

One-dimensional stitching interferometry assisted by a triple-beam interferometer.

In this work, we proposed for stitching interferometry to use a triple-beam interferometer to measure both the distance and the tilt for all sub-apertures before the stitching process. The relative piston between two neighboring sub-apertures is then calculated by using the data in the overlapping area. Comparisons are made between our method, and the classical least-squares principle stitching method. Our method can improve the accuracy and repeatability of the classical stitching method when a large number of sub-aperture topographies are taken into account. Our simulations and experiments on flat and spherical mirrors indicate that our proposed method can decrease the influence of the interferometer error from the stitched result. The comparison of stitching system with Fizeau interferometry data is about 2 nm root mean squares and the repeatability is within ± 2.5 nm peak to valley.

Model mismatch analysis and compensation for modal phase measuring deflectometry.

The correspondence residuals due to the discrepancy between the reality and the shape model in use are analyzed for the modal phase measuring deflectometry. Slope residuals are calculated from these discrepancies between the modal estimation and practical acquisition. Since the shape mismatch mainly occurs locally, zonal integration methods which are good at dealing with local variations are used to reconstruct the height residual for compensation. Results of both simulation and experiment indicate the proposed height compensation method is effective, which can be used as a post-complement for the modal phase measuring deflectometry.

Modal phase measuring deflectometry.

In this work, a model based method is applied to phase measuring deflectometry, named modal phase measuring deflectometry. The height and slopes of the surface under test are represented by mathematical models and updated by optimizing the model coefficients to minimize the discrepancy between the reprojection in ray tracing and the actual measurement. The pose of the screen relative to the camera is pre-calibrated and further optimized together with the shape coefficients of the surface under test. Simulations and experiments are conducted to demonstrate the feasibility of the proposed approach.

Controlling X-ray deformable mirrors during inspection.

The X-ray deformable mirror (XDM) is becoming widely used in the present synchrotron/free-electron laser facilities because of its flexibility in correcting wavefront errors or modification of the beam size at the sample location. Owing to coupling among the N actuators of an XDM, (N + 1) or (2N + 1) scans are required to learn the response of each actuator one by one. When the mirror has an important number of actuators (N) and the actuator response time including stabilization or the necessary metrology time is long, the learning process can be time consuming. In this work, a fast and accurate method is presented to drive an XDM to a target shape usually with only three or four measurements during inspection. The metrology data are used as feedback to calculate the curvature discrepancy between the current and the target shapes. Three different derivative estimation methods are introduced to calculate the curvature from measured data. The mirror shape is becoming close to the target through iterative compensations. The feasibility of this simple and effective approach is demonstrated by a series of experiments.

Robust self-calibration three-dimensional shape measurement in fringe-projection photogrammetry.

Commonly, fringe-projection photogrammetry involves two independent stages: system calibration and measurement. The measurement accuracy largely depends on the calibration procedure. However, the results of system calibration may be unstable in different occasions. In this Letter, we propose a robust self-calibration 3D shape measurement in fringe-projection photogrammetry by combining control and measurement points. The control points with known 3D coordinates are provided on the checkerboard, and the measurement points are identified by absolute phase information in the deformed fringes. The introduction of control points in the nonlinear collinearity equations can be regarded as invariant in the optimization procedure, which enhances the measurement robustness. Compared to the binocular model in fringe-projection technique, moreover, multiple-view ray intersection is utilized to reflect the advantage of photogrammetry in the fringe-projection 3D measurement.

Using concentric circles and wedge grating for camera calibration.

This paper presents a method for camera calibration based on the orthogonal vanishing point calibration using concentric circles grating and wedge grating. This method, which we believe is new, uses the high-precision characteristics of phase extraction to obtain the feature points, thus decreasing the calibration errors caused by the traditional marker extraction errors of gray pattern. According to the simulation experiment analysis results, the concentric circles grating was designed with seven periods and the wedge grating was designed with four periods. In the real measuring experiment, the grating target and the similar gray concentric circles target were used to calibrate the camera, respectively. Through comparing the reprojective errors of the two methods, the method proposed is proven to improve the calibration accuracy and robustness for the vanishing point calibration algorithm.

[Study on complex formation of quercetin reacting with Cu2+ using UV-Vis absorption spectroscopy].

Using an intensified spectroscopic detector ICCD, the real-time UV-Vis absorption spectra of quercetin (Q) reacting with Cu2+ under neutral and acid conditions were acquired. The exposure time was 0. 1 ms for each spectrum, and the molar ratio of Cu2+:Q was 0.2, 0.5, 1.0, 2.0, 5.0 and 10.0, respectively. Results indicate that the changes in absorption bands of reaction solutions with different ratio of Cu2+:Q were similar if other conditions were the same, and the greater the molar ratio, the shorter the reaction time; the reaction processes of complex formation were different under neutral and acid conditions. There was an intermediate product with the absorption peak at 428 nm that occurred during the reaction under neutral condition, but the final product was directly formed under acid condition, and the final products under both conditions had the same absorption bands centered at 296 nm; reaction processes with air and without air showed no difference. The present work first observed that there was an intermediate product formed during the complex formation of quercetin reacting with Cu2+ and the absorption band of the final complex was centered at 296 nm. Results obtained here provide useful experimental evidence for the study of complex mechanism of quercetin with Cu2+.

[Transient UV absorption spectra of artemisinin reacting with sodium hydroxide].

UV absorption spectrum of artemisinin and transient absorption spectra of various concentrations of artemisinin reacting with sodium hydroxide were measured by using an intensified spectroscopic detector ICCD. The exposure time of each spectrum was 0.1 ms. Results indicate that artemisinin has an obvious UV absorption band centered at 212.52 nm and can react with sodium hydroxide easily. All absorption spectra of different concentrations of artemisinin reacting with sodium hydroxide have the similar changes, but the moment at which the changes happened is different. After adding sodium hydroxide into artemisinin in ethanol solution, there was a new absorption band centered at 288 nm appearing firstly. As reaction went on, the intensity of another absorption band centered at 260 nm increased gradually. At the end of the reaction, a continuous absorption band from 200 to 350 nm with the peak at 245 nm formed finally. No other transient absorption spectral data are available on the reaction of artemisinin with sodium hydroxide currently. The new spectral information obtained in this experiment provides very important experimental basis for understanding the properties of artemisinin reacting with alkaline medium and is useful for correctly using of artemisinin as a potential anticancer drug.