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Keywords = opto-mechatronics

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15 pages, 2463 KiB  
Article
Measurement of the Effective Refractive Index of Suspensions Containing 5 µm Diameter Spherical Polystyrene Microparticles by Surface Plasmon Resonance and Scattering
by Osvaldo Rodríguez-Quiroz, Donato Luna-Moreno, Araceli Sánchez-Álvarez, Gabriela Elizabeth Quintanilla-Villanueva, Oscar Javier Silva-Hernández, Melissa Marlene Rodríguez-Delgado and Juan Francisco Villarreal-Chiu
Chemosensors 2025, 13(7), 257; https://doi.org/10.3390/chemosensors13070257 - 15 Jul 2025
Viewed by 333
Abstract
Microplastics (MP) have been found not only in the environment but also in living beings, including humans. As an initial step in MP detection, a method is proposed to measure the effective refractive index of a solution containing 5 µm diameter spherical polystyrene [...] Read more.
Microplastics (MP) have been found not only in the environment but also in living beings, including humans. As an initial step in MP detection, a method is proposed to measure the effective refractive index of a solution containing 5 µm diameter spherical polystyrene particles (SPSP) in distilled water, based on the surface plasmon resonance (SPR) technique and Mie scattering theory. The reflectances of the samples are obtained with their resonance angles and depths that must be normalized and adjusted according to the reference of the air and the distilled water, to subsequently find their effective refraction index corresponding to the Mie scattering theory. The system has an optical sensor with a Kretschmann–Raether configuration, consisting of a semicircular prism, a thin gold film, and a glass cell for solution samples with different concentrations (0.00, 0.20, 0.05, 0.50, and 1.00%). The experimental result provided a good linear fit with an R2 = 0.9856 and a sensitivity of 7.2863 × 105 RIU/% (refractive index unit per percentage of fill fraction). The limits of detection (LOD) and limit of quantification (LOQ) were determined to be 0.001% and 0.0035%, respectively. The developed optomechatronic system and its applications based on the SPR and Scattering enabled the effective measurement of the refractive index and concentration of solutions containing 5 µm diameter SPSP in distilled water. Full article
(This article belongs to the Special Issue Spectroscopic Techniques for Chemical Analysis)
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21 pages, 5073 KiB  
Article
Numerical Simulation of Thermal Cycling and Vibration Effects on Solder Layer Reliability in High-Power Diode Lasers for Space Applications
by Lei Cheng, Huaqing Sun, Xuanjun Dai and Bingxing Wei
Micromachines 2025, 16(7), 746; https://doi.org/10.3390/mi16070746 - 25 Jun 2025
Viewed by 309
Abstract
High-power laser diodes (HPLDs) are increasingly used in space applications, yet solder layer (SL) reliability critically limits their performance and lifespan. This study employs finite element analysis to evaluate SL failure mechanisms in microchannel-cooled HPLDs with two packaging configurations under thermal cycling and [...] Read more.
High-power laser diodes (HPLDs) are increasingly used in space applications, yet solder layer (SL) reliability critically limits their performance and lifespan. This study employs finite element analysis to evaluate SL failure mechanisms in microchannel-cooled HPLDs with two packaging configurations under thermal cycling and vibration. Based on the Anand constitutive model, contour plot analysis revealed that the critical stress–strain regions in both SLs were located at their edges. The stress–strain values along the X-axis of the SLs exceeded those in other axial directions, and SL failure would preferentially initiate from the edges along the cavity length direction. During random vibration analysis with excitation applied along the Z-axis, the equivalent stresses in both SLs exceeded X-/Y-axis levels. However, these values remained far below their yield strengths, indicating that only elastic strain and high-cycle fatigue occurred in the SLs. The calculated thermal fatigue lives of the two SLs were 2851 cycles and 5730 cycles, respectively. Their random vibration fatigue lives were determined as 5.75 × 107 h and 8.31 × 107 h. Using damage superposition under combined thermal-vibration loading, the total fatigue lives were predicted as 14,821 h and 29,786 h, respectively, with thermal cycling-induced damage dominating the failure mechanism. Full article
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16 pages, 4359 KiB  
Article
Nonlinear Imaging Detection of Organ Fibrosis in Minute Samples for Early Stage Utilizing Dual-Channel Two-Photon and Second-Harmonic Excitation
by Bo-Song Yu, Qing-Di Cheng, Yi-Zhou Liu, Rui Zhang, Da-Wei Li, Ai-Min Wang, Li-Shuang Feng and Xiao Jia
Biosensors 2025, 15(6), 357; https://doi.org/10.3390/bios15060357 - 4 Jun 2025
Viewed by 2822
Abstract
Histopathological staining remains the fibrosis diagnostic gold standard yet suffers from staining artifacts and variability. Nonlinear optical techniques (e.g., spontaneous fluorescence, Second Harmonic Generation) enhance accuracy but struggle with rapid trace-level detection of fibrosis. To address these limitations, a dual-channel nonlinear optical imaging [...] Read more.
Histopathological staining remains the fibrosis diagnostic gold standard yet suffers from staining artifacts and variability. Nonlinear optical techniques (e.g., spontaneous fluorescence, Second Harmonic Generation) enhance accuracy but struggle with rapid trace-level detection of fibrosis. To address these limitations, a dual-channel nonlinear optical imaging system with excitation wavelengths at 780 nm and 820 nm was developed, enabling simultaneous spontaneous fluorescence and second-harmonic generation imaging through grid localization. This study applies dual-modality nonlinear imaging to achieve label-free, high-resolution visualization of pulmonary and renal fibrosis at the ECM microstructure scale. Through leveraging this system, it is demonstrated that collagen can be rapidly detected via spontaneous fluorescence at 780 nm, whereas the spatial distribution of collagen fibrils is precisely mapped using Second Harmonic Generation at 820 nm. This approach allows for the rapid and sensitive detection of trace fibrosis in a 5-day unilateral ureteral obstruction mouse model. Additionally, we identify that the elastic fibers, which can also be visualized, provide a foundation for staging diagnosis and delivering accurate and quantitative data for pathological studies and analysis. The research findings underscore the potential of this dual-channel nonlinear optical imaging system as a powerful tool for rapid, precise, and noninvasive fibrosis detection and staging. Full article
(This article belongs to the Section Optical and Photonic Biosensors)
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5 pages, 165 KiB  
Editorial
Introduction to Special Issue on “Advances in 3OM: Opto-Mechatronics, Opto-Mechanics, and Optical Metrology”
by Virgil-Florin Duma, Guillermo Garcia-Torales and Tomohiko Hayakawa
Photonics 2025, 12(6), 557; https://doi.org/10.3390/photonics12060557 - 1 Jun 2025
Viewed by 372
Abstract
The 3OM concept was introduced in 2008 and combines three complementary domains: opto-mechatronics, opto-mechanics, and optical metrology [...] Full article
17 pages, 3624 KiB  
Review
Advances in Distal-Scanning Two-Photon Endomicroscopy for Biomedical Imaging
by Conghao Wang, Biao Yan, Siyuan Ma, Haijun Li, Tianxuan Feng, Xiulei Zhang, Dawei Li, Lishuang Feng and Aimin Wang
Photonics 2025, 12(6), 546; https://doi.org/10.3390/photonics12060546 - 29 May 2025
Viewed by 2693
Abstract
Two-photon endomicroscopy (2PEM), an endomicroscopic imaging technique based on the two-photon excitation effect, provides several technical benefits, including high spatiotemporal resolution, label-free structural and metabolic imaging, and optical sectioning. These characteristics make it extremely promising for biomedical imaging applications. This paper classifies distal-scanning [...] Read more.
Two-photon endomicroscopy (2PEM), an endomicroscopic imaging technique based on the two-photon excitation effect, provides several technical benefits, including high spatiotemporal resolution, label-free structural and metabolic imaging, and optical sectioning. These characteristics make it extremely promising for biomedical imaging applications. This paper classifies distal-scanning 2PEMs based on their actuation mechanism (PZT or MEMS) and excitation–collection optical path configuration (common or separate path). Recent representative advancements are reviewed. Furthermore, we introduce its biomedical applications in tissue, organ, and brain imaging with free-behaving mice. Finally, future development directions for distal-scanning 2PEM are discussed. Full article
(This article belongs to the Special Issue Emerging Trends in Multi-photon Microscopy)
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22 pages, 9215 KiB  
Article
Ensquared Energy and Optical Centroid Efficiency in Optical Sensors, Part 3: Optical Sensors
by Marija Strojnik and Yaujen Wang
Photonics 2025, 12(4), 344; https://doi.org/10.3390/photonics12040344 - 3 Apr 2025
Viewed by 351
Abstract
We previously introduced the concepts of optical centroid efficiency (OCE) and enclosed energy within a rectangular pixel (EOD). We applied them to an ideal lens with and without a central obscuration for two different detector pixel sizes. Also, we [...] Read more.
We previously introduced the concepts of optical centroid efficiency (OCE) and enclosed energy within a rectangular pixel (EOD). We applied them to an ideal lens with and without a central obscuration for two different detector pixel sizes. Also, we analyzed the performance of OCE vs. EOD for the following three Seidel primary aberrations of an ideal lens: spherical, coma, and astigmatism, plus defocus. In this paper, we concentrate on three different optical remote sensing instrument configurations. We burden them with a set of aberrations to mimic realistic generalized error budgets that cover potential ground, lunch, and on-orbit environmental conditions. The shape of the OCE vs. EOD curve depends to a large degree on the dominant aberration. With the proper choice of detector pixel size, OCE increases with EOD when EOD is larger than 0.6. The increased detector pixel size is advantageous for structures that enhance diffraction effects, and for off-axis and asymmetrical configurations. Analytical and experimental tests are proposed for original critical cases. Furthermore, OCE and EOD, as functional figures of merit, may be effectively applied to instruments for monitoring tumors and their evolution to cancerous tissue, leading to timely diagnosis. Full article
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17 pages, 13853 KiB  
Article
Investigation on the Full-Aperture Diffraction Efficiency of AOTF Based on Tellurium Dioxide Crystals
by Zhiyuan Mi, Huijie Zhao, Qi Guo, Zhoujun Zhong and Chengsheng Zhou
Photonics 2025, 12(4), 335; https://doi.org/10.3390/photonics12040335 - 2 Apr 2025
Viewed by 485
Abstract
The influence of acoustic field distribution and temperature variations on the full-aperture diffraction efficiency of non-collinear acousto-optic tunable filters (AOTFs) was investigated based on tellurium dioxide crystals. The strong acoustic anisotropy of the crystal induces non-uniform acoustic energy distribution, limiting the overall diffraction [...] Read more.
The influence of acoustic field distribution and temperature variations on the full-aperture diffraction efficiency of non-collinear acousto-optic tunable filters (AOTFs) was investigated based on tellurium dioxide crystals. The strong acoustic anisotropy of the crystal induces non-uniform acoustic energy distribution, limiting the overall diffraction efficiency. To analyze this effect, the acoustic field distribution within a large-aperture AOTF was simulated, and the diffraction efficiency across different aperture regions was evaluated and experimentally validated. The results demonstrate that sound beam contraction and acoustic energy non-uniformity significantly reduce the peak diffraction efficiency and increase the power required to achieve high diffraction efficiency. Additionally, temperature-induced variations in acoustic velocity alter the acoustic field structure, leading to spatially non-uniform changes in diffraction efficiency. Both simulations and experimental measurements confirm that while the overall impact of temperature on full-aperture diffraction efficiency remains relatively small, localized variations are pronounced, highlighting potential inaccuracies in single-beam-based efficiency measurements. Full article
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28 pages, 11200 KiB  
Article
Development of a Laser Surgical Device with Vibration Compensation: Mechanical Design and Validation of Its Compliant Mechanism
by Emil Ionuț Niță, Daniel C. Comeagă, Dragos A. Apostol and Virgil-Florin Duma
Appl. Sci. 2025, 15(7), 3686; https://doi.org/10.3390/app15073686 - 27 Mar 2025
Viewed by 547
Abstract
Mitigating hand tremors in surgical applications has a critical role in laser-based medical procedures. We report the development of a proof-of-concept 3 degrees of freedom (DOF) hand vibration compensation device that features a compliant mechanical structure with three stack-type piezoelectric actuators. Inspired by [...] Read more.
Mitigating hand tremors in surgical applications has a critical role in laser-based medical procedures. We report the development of a proof-of-concept 3 degrees of freedom (DOF) hand vibration compensation device that features a compliant mechanical structure with three stack-type piezoelectric actuators. Inspired by the Stewart-type mobile platform, the system has the capability to manipulate a laser beam in two directions. In the present work, the mechanical part of the device is designed, and its mathematical model is developed. Also, the manufacturing of the proposed platform is presented, and the precision of its parts is assessed. An in-house developed mechanical stand is designed and utilized in order to perform a static analysis of the linkage amplification mechanism. Both a finite element analysis (FEA) and experimental validations of this mechanism are performed. A good match is obtained between the results obtained with the two methods. An analysis of the errors is made in order to assess the mechanical aspects of the platform. The study lays the foundation for the further development of the mechatronic and optical parts of the system, as well as for its miniaturization. Full article
(This article belongs to the Section Applied Physics General)
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13 pages, 3606 KiB  
Article
A High-Sensitivity Graphene Metasurface and Four-Frequency Switch Application Based on Plasmon-Induced Transparency Effects
by Aijun Zhu, Mengyi Zhang, Weigang Hou, Lei Cheng, Cong Hu and Chuanpei Xu
Photonics 2025, 12(3), 218; https://doi.org/10.3390/photonics12030218 - 28 Feb 2025
Cited by 1 | Viewed by 745
Abstract
In this paper, we propose the use of a monolayer graphene metasurface to achieve various excellent functions, such as sensing, slow light, and optical switching through the phenomenon of plasmon-induced transparency (PIT). The designed structure of the metasurface consists of a diamond-shaped cross [...] Read more.
In this paper, we propose the use of a monolayer graphene metasurface to achieve various excellent functions, such as sensing, slow light, and optical switching through the phenomenon of plasmon-induced transparency (PIT). The designed structure of the metasurface consists of a diamond-shaped cross and a pentagon graphene resonator. We conducted an analysis of the electric field distribution and utilized Lorentz resonance theory to study the PIT window that is generated by the coupling of bright-bright modes. Additionally, by adjusting the Fermi level of graphene, we were able to achieve tunable dual frequency switching modulators. Furthermore, the metasurface also demonstrates exceptional sensing performance, with sensitivity and figure of merit (FOM) reaching values of 3.70 THz/RIU (refractive index unit) and 22.40 RIU-1, respectively. As a result, our numerical findings hold significant guiding significance for the design of outstanding terahertz sensors and photonic devices. Full article
(This article belongs to the Special Issue Photonics Metamaterials: Processing and Applications)
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23 pages, 4143 KiB  
Article
A Low-Cost Optomechatronic Diffuse Optical Mammography System for 3D Image Reconstruction: Proof of Concept
by Josué D. Rivera-Fernández, Alfredo Hernández-Mendoza, Diego A. Fabila-Bustos, José M. de la Rosa-Vázquez, Macaria Hernández-Chávez, Gabriela de la Rosa-Gutierrez and Karen Roa-Tort
Diagnostics 2025, 15(5), 584; https://doi.org/10.3390/diagnostics15050584 - 27 Feb 2025
Viewed by 917
Abstract
Background: The development and initial testing of an optomechatronic system for the reconstruction of three-dimensional (3D) images to identify abnormalities in breast tissue and assist in the diagnosis of breast cancer is presented. Methods: This system combines 3D reconstruction technology with [...] Read more.
Background: The development and initial testing of an optomechatronic system for the reconstruction of three-dimensional (3D) images to identify abnormalities in breast tissue and assist in the diagnosis of breast cancer is presented. Methods: This system combines 3D reconstruction technology with diffuse optical mammography (DOM) to offer a detecting tool that complements and assists medical diagnosis. DOM analyzes tissue properties with light, detecting density and composition variations. Integrating 3D reconstruction enables detailed visualization for precise tumor localization and sizing, offering more information than traditional methods. This technological combination enables more accurate, earlier diagnoses and helps plan effective treatments by understanding the patient’s anatomy and tumor location. Results: Using Chinese ink, it was possible to identify simulated abnormalities of 10, 15, and 20 mm in diameter in breast tissue phantoms from cosmetic surgery. Conclusions: Data can be processed using algorithms to generate three-dimensional images, providing a non-invasive and safe approach for detecting anomalies. Currently, the system is in a pilot testing phase using breast tissue phantoms, enabling the evaluation of its accuracy and functionality before application in clinical studies. Full article
(This article belongs to the Special Issue Advances in Breast Imaging and Analytics)
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4 pages, 175 KiB  
Editorial
Metal-Based Nanomaterials: Fabrications, Optical Properties, and Ultrafast Photonics
by Bo Fu and Vittorio Scardaci
Nanomaterials 2025, 15(3), 186; https://doi.org/10.3390/nano15030186 - 24 Jan 2025
Viewed by 726
Abstract
Metals are known for conductivity and luster due to the abundance of free electrons [...] Full article
11 pages, 1841 KiB  
Article
Complex Refractive Index Spectrum of CsPbBr3 Nanocrystals via the Effective Medium Approximation
by Sang-Hyuk Park, Jungwon Kim, Min Ju Kim, Min Woo Kim, Robert A. Taylor and Kwangseuk Kyhm
Nanomaterials 2025, 15(3), 181; https://doi.org/10.3390/nano15030181 - 24 Jan 2025
Cited by 1 | Viewed by 1692
Abstract
We have estimated the intrinsic complex refractive index spectrum of a CsPbBr3 nanocrystal. With various dilute solutions of CsPbBr3 nanocrystals dissolved in toluene, effective refractive indices were measured at two different wavelengths using Michelson interferometry. Given the effective absorption spectrum of [...] Read more.
We have estimated the intrinsic complex refractive index spectrum of a CsPbBr3 nanocrystal. With various dilute solutions of CsPbBr3 nanocrystals dissolved in toluene, effective refractive indices were measured at two different wavelengths using Michelson interferometry. Given the effective absorption spectrum of the solution, a full spectrum of the effective refractive index was also obtained through the Kramers–Krönig relations. Based on the Maxwell–Garnett model in the effective medium approximation, the real and imaginary spectrum of the complex refractive index was estimated for the CsPbBr3 nanocrystal, and the dominant inaccuracy was attributed to the size inhomogeneity. Full article
(This article belongs to the Special Issue Photonics and Optoelectronics with Functional Nanomaterials)
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12 pages, 10206 KiB  
Proceeding Paper
Portable Biomedical System for Acquisition, Display and Analysis of Cardiac Signals (SCG, ECG, ICG and PPG)
by Valery Sofía Zúñiga Gómez, Adonis José Pabuena García, Breiner David Solorzano Ramos, Saúl Antonio Pérez Pérez, Jean Pierre Coll Velásquez, Pablo Daniel Bonaveri and Carlos Gabriel Díaz Sáenz
Eng. Proc. 2025, 83(1), 19; https://doi.org/10.3390/engproc2025083019 - 23 Jan 2025
Viewed by 1091
Abstract
This study introduces a mechatronic biomedical device engineered for concurrent acquisition and analysis of four cardiac non-invasive signals: Electrocardiogram (ECG), Phonocardiogram (PCG), Impedance Cardiogram (ICG), and Photoplethysmogram (PPG). The system enables assessment of individual and simultaneous waveforms, allowing for detailed scrutiny of cardiac [...] Read more.
This study introduces a mechatronic biomedical device engineered for concurrent acquisition and analysis of four cardiac non-invasive signals: Electrocardiogram (ECG), Phonocardiogram (PCG), Impedance Cardiogram (ICG), and Photoplethysmogram (PPG). The system enables assessment of individual and simultaneous waveforms, allowing for detailed scrutiny of cardiac electrical and mechanical dynamics, encompassing heart rate variability, systolic time intervals, pre-ejection period (PEP), and aortic valve opening and closing timings (ET) through an application programmed with MATLAB App Designer, which applies derivative filters, smoothing, and FIR digital filters and evaluates the delay of each one, allowing the synchronization of all signals. These metrics are indispensable for deriving critical hemodynamic indices such as Stroke Volume (SV) and Cardiac Output (CO), paramount in the diagnostic armamentarium against cardiovascular pathologies. The device integrates an assembly of components including five electrodes, operational and instrumental amplifiers, infrared opto-couplers, accelerometers, and advanced filtering subsystems, synergistically tailored for precision and fidelity in signal processing. Rigorous validation utilizing a cohort of healthy subjects and benchmarking against established commercial instrumentation substantiates an accuracy threshold below 4.3% and an Interclass Correlation Coefficient (ICC) surpassing 0.9, attesting to the instrument’s exceptional reliability and robustness in quantification. These findings underscore the clinical potency and technical prowess of the developed device, empowering healthcare practitioners with an advanced toolset for refined diagnosis and management of cardiovascular disorders. Full article
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13 pages, 2818 KiB  
Article
Two-Dimensional Transition Metal Dichalcogenide: Synthesis, Characterization, and Application in Candlelight OLED
by Dipanshu Sharma, Sanna Gull, Anbalagan Ramakrishnan, Sushanta Lenka, Anil Kumar, Krishan Kumar, Pin-Kuan Lin, Ching-Wu Wang, Sinn-Wen Chen, Saulius Grigalevicius and Jwo-Huei Jou
Molecules 2025, 30(1), 27; https://doi.org/10.3390/molecules30010027 - 25 Dec 2024
Cited by 1 | Viewed by 1366
Abstract
Low-color-temperature candlelight organic light-emitting diodes (OLEDs) offer a healthier lighting alternative by minimizing blue light exposure, which is known to disrupt circadian rhythms, suppress melatonin, and potentially harm the retina with prolonged use. In this study, we explore the integration of transition metal [...] Read more.
Low-color-temperature candlelight organic light-emitting diodes (OLEDs) offer a healthier lighting alternative by minimizing blue light exposure, which is known to disrupt circadian rhythms, suppress melatonin, and potentially harm the retina with prolonged use. In this study, we explore the integration of transition metal dichalcogenides (TMDs), specifically molybdenum disulfide (MoS2) and tungsten disulfide (WS2), into the hole injection layers (HILs) of OLEDs to enhance their performance. The TMDs, which are known for their superior carrier mobility, optical properties, and 2D layered structure, were doped at levels of 0%, 5%, 10%, and 15% in PEDOT:PSS-based HILs. Our findings reveal that OLEDs doped with 10% MoS2 exhibit notable enhancements in power efficacy (PE), current efficacy (CE), and external quantum efficiency (EQE) of approximately 39%, 21%, and 40%, respectively. In comparison, OLEDs incorporating 10% of WS2 achieve a PE of 28%, a CE of 20%, and an EQE of 35%. The enhanced performance of the MoS2-doped devices is attributed to their superior hole injection and balanced carrier transport properties, resulting in more efficient operation. These results highlight the potential of incorporating 2D TMDs, especially MoS2, into OLED technology as a promising strategy to enhance energy efficiency. This approach aligns with environmental, social, and governance (ESG) goals by emphasizing reduced environmental impact and promoting ethical practices in technology development. The improved performance metrics of these TMD-doped OLEDs suggest a viable path towards creating more energy-efficient and health-conscious lighting solutions. Full article
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23 pages, 10390 KiB  
Article
The Influence of Spatial Scale Effect on Rock Spectral Reflectance: A Case Study of Huangshan Copper–Nickel Ore District
by Ziwei Wang, Huijie Zhao, Guorui Jia and Feixiang Wang
Remote Sens. 2024, 16(24), 4643; https://doi.org/10.3390/rs16244643 - 11 Dec 2024
Cited by 1 | Viewed by 718
Abstract
The spectral reflectance measured in situ is often regarded as the “truth”. However, its limited coverage and large spatial heterogeneity often make the ground-based reflectance unable to represent the remote sensing images. Since the spatial scale mismatch between ground-based, airborne, and spaceborne measurements, [...] Read more.
The spectral reflectance measured in situ is often regarded as the “truth”. However, its limited coverage and large spatial heterogeneity often make the ground-based reflectance unable to represent the remote sensing images. Since the spatial scale mismatch between ground-based, airborne, and spaceborne measurements, the applications of geological exploration, metallogenic prognosis and mine monitoring are facing severe challenges. In order to explore the influence of spatial scale effect on rock spectra, spectral reflectance with uncertainty caused by differences in illumination view geometry and spatial heterogeneity is introduced into the Bayesian Maximum Entropy (BME) method. Then, the rock spectra are upscaled from the point-scale to meter-scale and to 10 m-scale, respectively. Finally, the influence of spatial scale effect is evaluated based on the reflectance value, spectral shape, and spectral characteristic parameters. The results indicate that the BME model shows better upscaling accuracy and stability than Ordinary Kriging and Ordinary Least Squares model. The maximum Euclidean Distance of rock spectra caused by spatial resolution change is 6.271, and the Spectral Angle Mapper can reach 0.370. The spectral absorption position, absorption depth, and spectral absorption index are less affected by scale effect. For the area with similar spatial heterogeneity to the Huangshan Copper–Nickel Ore District, when the spatial resolution of the image is greater than 10 m, the rock’s spectrum is less influenced by the change in spatial resolution. Otherwise, the influence of spatial scale effect should be considered in applications. In addition, this work puts forward a set of processes to evaluate the influence of spatial scale effect in the study area and carry out the upscaling. Full article
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