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Photonics
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Optical Technology for Challenging Conditions：Methods and Applications
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Optical Technology for Challenging Conditions：Methods and Applications

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "New Applications Enabled by Photonics Technologies and Systems".

Deadline for manuscript submissions: closed (20 May 2025) | Viewed by 13140

Special Issue Editors

Dr. Xiaobo Li

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Guest Editor
School of Marine Science and Technology, Tianjin University, Tianjin 300054, China
Interests: polarization optics (polarimetry and polarimetric imaging); oceanic optics; deep learning and signal processing
Special Issues, Collections and Topics in MDPI journals
Dr. Jing Wu

E-Mail Website
Guest Editor
College of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350108, China
Interests: optical imaging; optical scattering; photodetectors; optoelectronic imaging; computational imaging; machine vision
Dr. Hongyuan Wang

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Guest Editor
Department of Precision Instruments, Tsinghua University, Beijing 100084, China
Interests: near-field photometry; polarimetric imaging
Dr. Yu Liu

E-Mail Website
Guest Editor
College of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350108, China
Interests: optical imaging; optical scattering; photodetectors

Special Issue Information

Dear Colleagues,

With the ongoing advancements in manufacturing technology and information processing technology, advanced optical imaging/measurement techniques play irreplaceable roles in many fields, such as the biomedical field, neurophotonics, intelligent driving, aerospace exploration, and remote sensing. However, these applications often face complex challenges in terms of application scenarios and environments, such as non-uniform lighting, strong scattering, low light, high noise, and turbulence. Solving the challenges of optical signal attenuation, oscillation, and distortion in complex environments/scenarios is crucial to improving the quality of optical imaging and detection in the aforementioned fields. Consequently, there is a pressing need for the development of cutting-edge optical imaging and detecting systems, coupled with intelligent processing algorithms, to expand the applicability of optical technology in complex environments and bolster its technical resilience.

The purpose of this Special Issue is to provide a platform for researchers to share and discuss their important discoveries, theoretical and experimental advances, technical breakthroughs, methodological innovations, application developments, viewpoints, and perspectives to the community of optical imaging/measurement. All theoretical, numerical, and experimental works related to optical techniques used in complex conditions are accepted. Topics include, but are not limited to, the following:

  • Optics in complex media (scattering tissues, turbid water, cloud, fog, etc.);
  • Imaging in adverse weather conditions;
  • Photometry and lighting technology;
  • Optical remote sensing;
  • Optical super-resolution, dehazing, denoising/despeckling, and deblurring;
  • Target detection in challenging conditions.

Dr. Xiaobo Li
Dr. Jing Wu
Dr. Hongyuan Wang
Dr. Yu Liu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • optical imaging
  • complex media
  • adverse weather conditions
  • wavefront shaping

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Published Papers (9 papers)

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Research

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18 pages, 5909 KiB  
Communication
High-Speed Target Location Based on Photoelectric Imaging and Laser Ranging with Fast Steering Mirror Deflection
by Kui Shi, Hongtao Yang, Jianwei Peng, Yingjun Ma and Hongwei Zhang
Photonics 2025, 12(2), 108; https://doi.org/10.3390/photonics12020108 - 24 Jan 2025
Viewed by 804
Abstract
There is an increasing number of spacecrafts in orbit, and the collision impact of high-speed moving targets, such as space debris, can cause fatal damage to these spacecrafts. It has become increasingly important to rapidly and accurately locate high-speed moving targets in space. [...] Read more.
There is an increasing number of spacecrafts in orbit, and the collision impact of high-speed moving targets, such as space debris, can cause fatal damage to these spacecrafts. It has become increasingly important to rapidly and accurately locate high-speed moving targets in space. In this study, we designed a visible-light telephoto camera for observing high-speed moving targets and a laser rangefinder for measuring the precise distance of these targets, and we proposed a method of using fast steering mirror deflection to quickly direct the emitted laser towards such targets and measure the distance. Based on the principle of photographic imaging and the precise distance of targets, a collinear equation and a spatial target location model based on the internal and external orientation elements of the camera and the target distance were established, and the principle of target location and the method for calculating target point coordinates were determined. We analyzed the composition of target point location error and derived an equation for calculating such errors. Based on the actual values of various error components and the error synthesis theory, the accuracy of target location was calculated to be 26.5 m when the target distance is 30 km (the relative velocity is 8 km/s and the velocity component perpendicular to the camera’s optical axis is less than 3.75 km/s). This study provides a theoretical basis and a method for solving the practical needs of quickly locating high-speed moving targets in space and proposes specific measures to improve target location accuracy. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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14 pages, 2550 KiB  
Article
Backlight Imaging Based on Laser-Gated Technology
by Jinzhou Bai, Hengkang Zhang, Huiqin Gao, Shaogang Guo, Siyuan Wang and An Pan
Photonics 2024, 11(12), 1141; https://doi.org/10.3390/photonics11121141 - 4 Dec 2024
Viewed by 930
Abstract
Backlight imaging refers to the process of capturing images when the light source directly enters the lens of imaging devices or against a high-brightness background, which usually suffers from degraded imaging quality caused by direct or reflected strong light. Traditional backlight imaging methods [...] Read more.
Backlight imaging refers to the process of capturing images when the light source directly enters the lens of imaging devices or against a high-brightness background, which usually suffers from degraded imaging quality caused by direct or reflected strong light. Traditional backlight imaging methods involve reducing light flux, expanding dynamic range, and utilizing avoidance angles. However, these methods only partially address the issue of backlighting, and are unable to effectively extract information from the areas overwhelmed by the backlight. To overcome these limitations, this paper reported a backlight imaging technique based on active illumination laser gated imaging technology (AILGIT), originally applied in underwater scattering imaging. Given that backlight imaging is essentially a form of scattering imaging, this technique is likely applicable to backlight scenarios. The AILGIT employs nanosecond-gated imaging components synchronized with nanosecond pulse laser illumination to spatially slice the target. This method allows the camera to capture target signals within specific slices only, which effectively suppresses ambient light and scattering interference from the medium and achieves high-contrast imaging with strong backlight suppression. Experiments obtained dynamic backlight imaging results for a vehicle with headlight on at night from a distance of 500 m, with 60 frames per second and a 4.2 by 2.8 meters’ field of view, where wheel contours and the license plate can be clearly distinguished. The result not only demonstrates the potential of AILGIT in suppressing strong backlight, but also lays the foundation for further research on laser 3D imaging and subsequent processing techniques for backlight targets. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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11 pages, 1848 KiB  
Communication
Broadband Optical Frequency Comb Generation Utilizing a Gain-Switched Weak-Resonant-Cavity Fabry–Perot Laser Diode under Multi-Wavelength Optical Injection
by Yuhong Tao, Qiupin Wang, Pu Ou, Guangqiong Xia and Zhengmao Wu
Photonics 2024, 11(10), 912; https://doi.org/10.3390/photonics11100912 - 27 Sep 2024
Viewed by 1089
Abstract
We propose and experimentally demonstrate an approach for generating a wideband optical frequency comb (OFC) featuring multiple comb lines and wavelength tunability based on a gain-switched weak-resonant-cavity Fabry–Perot laser diode (WRC-FPLD) under multi-wavelength optical injection. The longitudinal mode interval of the utilized WRC-FPLD [...] Read more.
We propose and experimentally demonstrate an approach for generating a wideband optical frequency comb (OFC) featuring multiple comb lines and wavelength tunability based on a gain-switched weak-resonant-cavity Fabry–Perot laser diode (WRC-FPLD) under multi-wavelength optical injection. The longitudinal mode interval of the utilized WRC-FPLD is about 0.28 nm (35.0 GHz), and its relaxation oscillation frequency is about 2.0 GHz at 1.15 times the threshold current. Under current modulation with a power of 20.00 dBm and a frequency of 2.0 GHz, the WRC-FPLD is driven into the gain-switched state. By further introducing multi-wavelength injection light (MWIL) containing four power equalization comb lines with an interval of 0.56 nm, a wideband OFC featuring multiple comb lines and wavelength tenability can be obtained. The experimental results demonstrate that by gradually increasing the injection’s optical power, the number of produced OFC lines initially increases and then decreases. By meticulously adjusting the wavelengths of the MWIL and carefully selecting the matched injection power, the broadband OFC can be tuned across an extensive spectral range. Under optimized operation parameters, an OFC with 147 lines, and a bandwidth of approximately 292 GHz within a 10 dB amplitude, variation is achieved. In this case, the measured single-sideband phase noise at the fundamental frequency is about −115 dBc/Hz @ 10 kHz, indicating that the comb lines possess good stability and strong coherence. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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14 pages, 24677 KiB  
Article
Rethinking of Underwater Image Restoration Based on Circularly Polarized Light
by Chao Wang, Zhiyang Wu, Zexiong Han, Junguang Wang, Haofeng Hu and Xiaobo Li
Photonics 2024, 11(8), 773; https://doi.org/10.3390/photonics11080773 - 20 Aug 2024
Cited by 5 | Viewed by 1666
Abstract
Polarimetric imaging technology plays a crucial role in de-scattering, particularly in the field of underwater image restoration. Circularly polarized light (or the underlying circular polarization memory effect) has been proven to better preserve the polarization characteristics of detected light. Utilizing circularly polarized light [...] Read more.
Polarimetric imaging technology plays a crucial role in de-scattering, particularly in the field of underwater image restoration. Circularly polarized light (or the underlying circular polarization memory effect) has been proven to better preserve the polarization characteristics of detected light. Utilizing circularly polarized light as illumination can further enhance the effectiveness of polarization de-scattering techniques. After rethinking the advantages of circularly polarized light, this paper proposes a new method for underwater polarimetric imaging restoration that leverages the pre-processing of polarized sub-images and the correlation of polarization characteristics (i.e., the angle of polarization and degree of polarization). Additionally, to address the challenge of selecting scattering light parameters due to uneven light fields in target scenes, an intensity adjustment factor search algorithm is designed. This algorithm eliminates the need for the manual selection of scattering light parameters, effectively solving the problem of uneven illumination in restoration results. A series of experiments demonstrate that, compared to traditional algorithms, the proposed method offers superior detail restoration and higher robustness. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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10 pages, 1954 KiB  
Communication
Real-Time Massive Parallel Generation of Physical Random Bits Using Weak-Resonant-Cavity Fabry-Perot Laser Diodes
by Yongbo Wang, Xi Tang, Zhengmao Wu, Jiagui Wu and Guangqiong Xia
Photonics 2024, 11(8), 759; https://doi.org/10.3390/photonics11080759 - 14 Aug 2024
Viewed by 1176
Abstract
We experimentally demonstrate a scheme for generating massively parallel and real-time physical random bits (PRBs) by using weak-resonant-cavity Fabry-Perot laser diodes (WRC-FPLDs) with optical feedback. By using external optical feedback to modify the nonlinear dynamic behavior of the longitudinal modes in WRC-FPLDs, the [...] Read more.
We experimentally demonstrate a scheme for generating massively parallel and real-time physical random bits (PRBs) by using weak-resonant-cavity Fabry-Perot laser diodes (WRC-FPLDs) with optical feedback. By using external optical feedback to modify the nonlinear dynamic behavior of the longitudinal modes in WRC-FPLDs, the chaotic behavior of each channel can be induced under suitable feedback strength. By filtering these longitudinal modes, a real-time PRBs at 10 Gbits/s can be generated by using field programmable gate array (FPGA) board for the real-time post-processing of a single-channel chaotic signal. Considering the presence of up to 70 longitudinal modes within a broad spectral range exceeding 40 nm, each of these modes can be used to extract chaotic time sequences for random number generation. Therefore, our PRB generation scheme has the potential to achieve a data throughput of over 700 Gbits/s. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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9 pages, 2039 KiB  
Article
Modulated Short-Time Fourier-Transform-Based Nonstationary Signal Decomposition for Dual-Comb Ranging Systems
by Ningning Han, Chao Wang, Zhiyang Wu, Xiaoyu Zhai, Yongzhen Pei, Haonan Shi and Xiaobo Li
Photonics 2024, 11(6), 560; https://doi.org/10.3390/photonics11060560 - 14 Jun 2024
Cited by 2 | Viewed by 1104
Abstract
Analyzing and breaking down nonstationary signals into their primary components is significant in various optical applications. In this work, we design a direct, localized, and mathematically rigorous method for nonstationary signals by employing a modulated short-time Fourier transform (MSTFT) that can be implemented [...] Read more.
Analyzing and breaking down nonstationary signals into their primary components is significant in various optical applications. In this work, we design a direct, localized, and mathematically rigorous method for nonstationary signals by employing a modulated short-time Fourier transform (MSTFT) that can be implemented efficiently using fast Fourier transform, subsequently isolating energy-concentrated sets through an approximate threshold process, allowing us to directly retrieve instantaneous frequencies and signal components by determining the maximum frequency within each set. MSTFT provides a new insight into the time-frequency analysis in multicomponent signal separation and can be extended to other time-frequency transforms. Beyond the analysis of the synthetic, we also perform real dual-comb ranging signals under turbid water, and the results show an approximate 1.5 dB improvement in peak signal-to-noise ratio, further demonstrating the effectiveness of our method in challenging conditions. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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16 pages, 3586 KiB  
Article
Planar Bilayer PT-Symmetric Systems and Resonance Energy Transfer
by Aliaksandr Arlouski and Andrey Novitsky
Photonics 2024, 11(2), 169; https://doi.org/10.3390/photonics11020169 - 10 Feb 2024
Viewed by 1590
Abstract
Parity-time (PT) symmetry provides an outstanding improvement of photonic devices’ performance due to the remarkable physics behind it. Resonance energy transfer (RET) as an important characteristic mediating the molecules that can be tailored in the PT-symmetric environment, too. We study how planar bilayer [...] Read more.
Parity-time (PT) symmetry provides an outstanding improvement of photonic devices’ performance due to the remarkable physics behind it. Resonance energy transfer (RET) as an important characteristic mediating the molecules that can be tailored in the PT-symmetric environment, too. We study how planar bilayer PT-symmetric systems affect the process of resonance energy transfer occurring in the vicinity thereof. First, we investigate the reflectance and transmittance spectra of such systems by calculating reflection and transmission coefficients as well as total radiation amplification as functions of medium parameters. We obtain that reflectance and total amplification are greatest near the exceptional points of the PT-symmetric system. Then, we perform numerical calculations of the RET rate and investigate its dependence on the complex permittivity of the PT-symmetric medium, dipole orientation, frequency of radiation and layer thickness. Optically thick PT-symmetric systems may operate at lower gain at the expense of the appearance of chaotic-like behaviors. These appear owing to the dense oscillations in the reflectance and transmittance spectra and vividly manifest themselves as stochastic-like positions of the exceptional points for PT-symmetric bilayers. The RET rate, being a result of the field interference, can be significantly amplified and suppressed near exceptional points exhibiting a Fano-like lineshape. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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15 pages, 6967 KiB  
Article
Polarization-Based De-Scattering Imaging in Turbid Tissue-like Scattering Media
by Shirong Zhang, Jian Liang, Yanru Jiang and Liyong Ren
Photonics 2023, 10(12), 1374; https://doi.org/10.3390/photonics10121374 - 14 Dec 2023
Cited by 1 | Viewed by 1652
Abstract
In shallow tissues of the human body, pathological changes often occur, and there are several kinds of scattering media, such as mucosa, fat, and blood, present on the surface of these tissues. In such scattering environments, it is difficult to distinguish the location [...] Read more.
In shallow tissues of the human body, pathological changes often occur, and there are several kinds of scattering media, such as mucosa, fat, and blood, present on the surface of these tissues. In such scattering environments, it is difficult to distinguish the location of the lesions using traditional attenuation-based imaging methods, while polarization-based imaging methods are more sensitive to this information. Therefore, in this paper, we conducted experiments using diluted milk to simulate biological tissues with scattering effects, illuminated with non-polarized light sources, and used an optimized robust polarization de-scattering algorithm for image processing. The results were qualitatively and quantitatively analyzed through local intensity comparison and visual fidelity functions, verifying the effectiveness of this algorithm under specific conditions. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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Review

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17 pages, 2624 KiB  
Review
Light Disturbance Analysis and Applications
by Rafaela S. Alves-de-Carvalho, Rute J. Macedo-de-Araújo and José M. González-Méijome
Photonics 2024, 11(10), 905; https://doi.org/10.3390/photonics11100905 - 26 Sep 2024
Cited by 1 | Viewed by 2011
Abstract
This narrative review synthesizes recent basic and clinical research on visual disturbances in low-light environments, highlighting the evaluation techniques for these conditions. It focuses on the degradation of visual acuity under dim lighting, exacerbated by pupil dilation, known as night vision disturbance (NVD). [...] Read more.
This narrative review synthesizes recent basic and clinical research on visual disturbances in low-light environments, highlighting the evaluation techniques for these conditions. It focuses on the degradation of visual acuity under dim lighting, exacerbated by pupil dilation, known as night vision disturbance (NVD). Key contributors to NVD include optical scattering, intraocular diffraction, ocular aberrations, and uncorrected refractive errors, all significantly impacting quality of life and functional abilities. This review also examines the effects of aging, eye disorders, surgical interventions, and corneal irregularities on NVD. It details the definitions, distinctions, and measurement methodologies for various optical phenomena, using both objective and subjective approaches, such as visual function questionnaires, simulators, and the light disturbance analyzer (LDA). The LDA is validated for clinical characterization and quantification of light distortion, proving useful in both clinical and research settings. This review advocates for continued innovation in therapeutic interventions to improve patient outcomes and alleviate the impact of visual disturbances. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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