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Optical Sensors and Measuring Systems: Design and Applications
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Optical Sensors and Measuring Systems: Design and Applications

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Optical Sensors".

Deadline for manuscript submissions: closed (29 July 2023) | Viewed by 5056

Special Issue Editor

Dr. Sergey Y. Yurish

E-Mail Website
Guest Editor
International Frequency Sensor Association (IFSA), 08860 Castelldefels, Spain
Interests: smart sensors; optical sensors; frequency measurements
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The Special Issue contains extended papers published after the 6th International Conference on Optics, Photonics and Lasers (OPAL' 2023), Funchal (Madeira Island), Portugal, 24-26 May 2023.

The event incorporates three symposia covering a broaden range in optics, photonics, and lasers, and provides an excellent opportunity to exchange ideas and present latest advancements in these areas. The OPAL 2023 is organized by the International Frequency Sensor Association (IFSA)—a professional, non-profit association serving the sensor industry and academy more than 20 years.

The purpose of OPAL 2023 is to bring together leading international researchers, engineers, and practitioners interested in any optical-related technologies, as well as from various application areas, to discuss problems and solutions in this area, to identify new issues, and to shape future directions for research.

This Special Issue will focus on introducing the research and applications in the field of optical, photonic sensors, and instrumentation, such as design, sensing materials, and applications. The topics of interest include, but are not limited to:

  • Optical sensors and instrumentation
  • Fiber optical sensors
  • Micro-opto-electro-mechanical systems (MOEMS)
  • Photonic sensors
  • Photodetectors

Dr. Sergey Y. Yurish
Guest Editor

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. Sensors is an international peer-reviewed open access semimonthly 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 2600 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 sensors
  • fiber optical sensors
  • micro-opto-electro-mechanical systems (MOEMS)
  • photonic sensors
  • photodetectors

Published Papers (5 papers)

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Research

19 pages, 5968 KiB  
Article
Drift Error Compensation Algorithm for Heterodyne Optical Seawater Refractive Index Monitoring of Unstable Signals
by Shiwen Zhang, Liyan Li, Yuliang Liu and Yan Zhou
Sensors 2023, 23(20), 8460; https://doi.org/10.3390/s23208460 - 14 Oct 2023
Viewed by 627
Abstract
The refractive index measurement of seawater has proven significance in oceanography, while an optical heterodyne interferometer is an important, highly accurate, tool used for seawater refractive index measurement. However, for practical seawater refractive index measurement, the refractive index of seawater needs to be [...] Read more.
The refractive index measurement of seawater has proven significance in oceanography, while an optical heterodyne interferometer is an important, highly accurate, tool used for seawater refractive index measurement. However, for practical seawater refractive index measurement, the refractive index of seawater needs to be monitored for long periods of time, and the influence of drift error on the measurement results for these cases cannot be ignored. This paper proposes a drift error compensation algorithm based on wavelet decomposition, which can adaptively separate the background from the signal, and then calculate the frequency difference to compensate for the drift error. It is suitable for unstable signals, especially signals with large differences between the beginning and the end, which is common in actual seawater refractive index monitoring. The authors identify that the primary cause of drift error is the frequency instability of the acousto-optic frequency shifter (AOFS), and the actual frequency difference was measured through experimentation. The frequency difference was around 0.1 Hz. Simulation experiments were designed to verify the effectiveness of the algorithm, and the standard deviation of the optical length of the results was on the scale of 10−8 m. Liquid refractive index measurement experiments were carried out in a laboratory, and the measurement error was reduced from 36.942% to 0.592% after algorithm processing. Field experiments were carried out regarding seawater refractive index monitoring, and the algorithm-processing results are able to match the motion of the target vehicle. The experimental data were processed with different algorithms, and, according to the comparison of the results, the proposed algorithm performs better than other existing drift error elimination algorithms. Full article
(This article belongs to the Special Issue Optical Sensors and Measuring Systems: Design and Applications)
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10 pages, 1624 KiB  
Communication
Structural Design and Verification of an Effective-Area Measurement Device Detection System
by Xiangzi Chen, Ziping Yun, Ting You and Xiangqian Quan
Sensors 2023, 23(19), 8215; https://doi.org/10.3390/s23198215 - 01 Oct 2023
Viewed by 696
Abstract
The effective-area method is a new way to measure aperture area. It defines aperture area by directly using the beam-limiting effect of the aperture in radiometric measurement. Due to the special structure of the measurement device, it is necessary to find a suitable [...] Read more.
The effective-area method is a new way to measure aperture area. It defines aperture area by directly using the beam-limiting effect of the aperture in radiometric measurement. Due to the special structure of the measurement device, it is necessary to find a suitable method to design the detection system. In this paper, the measurement system model is constructed in the TracePro program. The real circumstances of light propagation for the measurement beam are simulated, and the responses of the detector are given. It is proved that the relative change in the detector response is the lowest when the detector is at the position of 132°. And this is the best structure design of the detection system. The experimental results are designed to verify the feasibility of the structure design of the detection system. Full article
(This article belongs to the Special Issue Optical Sensors and Measuring Systems: Design and Applications)
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17 pages, 3858 KiB  
Article
FPGA-Based Feature Extraction and Tracking Accelerator for Real-Time Visual SLAM
by Jie Zhang, Shuai Xiong, Cheng Liu, Yongchao Geng, Wei Xiong, Song Cheng and Fang Hu
Sensors 2023, 23(19), 8035; https://doi.org/10.3390/s23198035 - 22 Sep 2023
Cited by 1 | Viewed by 1111
Abstract
Due to its advantages of low latency, low power consumption, and high flexibility, FPGA-based acceleration technology has been more and more widely studied and applied in the field of computer vision in recent years. An FPGA-based feature extraction and tracking accelerator for real-time [...] Read more.
Due to its advantages of low latency, low power consumption, and high flexibility, FPGA-based acceleration technology has been more and more widely studied and applied in the field of computer vision in recent years. An FPGA-based feature extraction and tracking accelerator for real-time visual odometry (VO) and visual simultaneous localization and mapping (V-SLAM) is proposed, which can realize the complete acceleration processing capability of the image front-end. For the first time, we implement a hardware solution that combines features from accelerated segment test (FAST) feature points with Gunnar Farneback (GF) dense optical flow to achieve better feature tracking performance and provide more flexible technical route selection. In order to solve the scale invariance and rotation invariance lacking problems of FAST features, an efficient pyramid module with a five-layer thumbnail structure was designed and implemented. The accelerator was implemented on a modern Xilinx Zynq FPGA. The evaluation results showed that the accelerator could achieve stable tracking of features of violently shaking images and were consistent with the results from MATLAB code running on PCs. Compared to PC CPUs, which require seconds of processing time, the processing latency was greatly reduced to the order of milliseconds, making GF dense optical flow an efficient and practical technical solution on the edge side. Full article
(This article belongs to the Special Issue Optical Sensors and Measuring Systems: Design and Applications)
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12 pages, 17663 KiB  
Article
Rectangular Amplitude Mask-Based Auto-Focus Method with a Large Range and High Precision for a Micro-LED Wafer Defects Detection System
by Wenjun He, Yufeng Ma and Wenbo Wang
Sensors 2023, 23(17), 7579; https://doi.org/10.3390/s23177579 - 31 Aug 2023
Viewed by 949
Abstract
Auto-focus technology plays an important role in the Micro-LED wafer defects detection system. How to accurately measure the defocus amount and the defocus direction of the Micro-LED wafer sample in a large linear range is one of the keys to realizing wafer defects [...] Read more.
Auto-focus technology plays an important role in the Micro-LED wafer defects detection system. How to accurately measure the defocus amount and the defocus direction of the Micro-LED wafer sample in a large linear range is one of the keys to realizing wafer defects detection. In this paper, a large range and high-precision auto-focus method based on a rectangular amplitude mask is proposed. A rectangular amplitude mask without a long edge is used to modulate the shape of the incident laser beams so that the spot shape distribution of the reflected laser beam on the sensor changes with the defocus amount of the wafer sample. By calculating the shape of the light spots, the defocus amount and the defocus direction can be obtained at the same time. The experimental results show that under the 20× microscopy objective, the linear range of the auto-focus system is 480 μm and the accuracy can reach 1 μm. It can be seen that the automatic focusing method proposed in this paper has the advantages of large linear range, high accuracy, and compact structure, which can meet the requirements of the Micro-LED wafer defects detection equipment. Full article
(This article belongs to the Special Issue Optical Sensors and Measuring Systems: Design and Applications)
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23 pages, 6931 KiB  
Article
Dark Current Analysis on GeSn p-i-n Photodetectors
by Soumava Ghosh, Greg Sun, Timothy A. Morgan, Gregory T. Forcherio, Hung-Hsiang Cheng and Guo-En Chang
Sensors 2023, 23(17), 7531; https://doi.org/10.3390/s23177531 - 30 Aug 2023
Cited by 3 | Viewed by 1144
Abstract
Group IV alloys of GeSn have been extensively investigated as a competing material alternative in shortwave-to-mid-infrared photodetectors (PDs). The relatively large defect densities present in GeSn alloys are the major challenge in developing practical devices, owing to the low-temperature growth and lattice mismatch [...] Read more.
Group IV alloys of GeSn have been extensively investigated as a competing material alternative in shortwave-to-mid-infrared photodetectors (PDs). The relatively large defect densities present in GeSn alloys are the major challenge in developing practical devices, owing to the low-temperature growth and lattice mismatch with Si or Ge substrates. In this paper, we comprehensively analyze the impact of defects on the performance of GeSn p-i-n homojunction PDs. We first present our theoretical models to calculate various contributing components of the dark current, including minority carrier diffusion in p- and n-regions, carrier generation–recombination in the active intrinsic region, and the tunneling effect. We then analyze the effect of defect density in the GeSn active region on carrier mobilities, scattering times, and the dark current. A higher defect density increases the dark current, resulting in a reduction in the detectivity of GeSn p-i-n PDs. In addition, at low Sn concentrations, defect-related dark current density is dominant, while the generation dark current becomes dominant at a higher Sn content. These results point to the importance of minimizing defect densities in the GeSn material growth and device processing, particularly for higher Sn compositions necessary to expand the cutoff wavelength to mid- and long-wave infrared regime. Moreover, a comparative study indicates that further improvement of the material quality and optimization of device structure reduces the dark current and thereby increases the detectivity. This study provides more realistic expectations and guidelines for evaluating GeSn p-i-n PDs as a competitor to the III-V- and II-VI-based infrared PDs currently on the commercial market. Full article
(This article belongs to the Special Issue Optical Sensors and Measuring Systems: Design and Applications)
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