Research

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15 pages, 5345 KiB

Open AccessArticle

All-Fiber Pulse-Train Optical Frequency-Domain Interferometer for Dynamic Absolute Distance Measurements of Vibration

by Heli Ma, Cangli Liu, Long Chen, Longhuang Tang, Tianjiong Tao, Jian Wu, Shenggang Liu, Xing Jia, Chengjun Li, Xiang Wang and Jidong Weng

Photonics 2023, 10(12), 1342; https://doi.org/10.3390/photonics10121342 - 05 Dec 2023

Viewed by 775

Abstract

In this paper, we propose an all-fiber co-axial optical frequency-domain interferometer (OFDI) in a pulse-train mode with a sample rate of 9 kHz for measuring the vibrations in an internal structure without any contact. It was subjected to a range of 4.555 mm [...] Read more.

In this paper, we propose an all-fiber co-axial optical frequency-domain interferometer (OFDI) in a pulse-train mode with a sample rate of 9 kHz for measuring the vibrations in an internal structure without any contact. It was subjected to a range of 4.555 mm and had an accuracy level of 0.006 mm, as confirmed by a linear motion experiment. Due to the precise time synchronization for reducing the background light leakage and suppressing the dynamic fuzziness, the proposed OFDI could realize the dynamic absolute distance measurements of the vibration process under harmonic excitation with frequencies ranging from 200 Hz to 1800 Hz. The characteristic parameters of vibration could be analyzed using the acquired distance results. Furthermore, the OFDI system obtained the frequency conversion as the time under anharmonic periodic excitation with a sweeping rate of 3600 Hz/s. The measurement performance for the vibration velocity compared with the displacement interferometer system for any reflector (DISAR) was demonstrated in a harmonic excitation experiment. The proposed method expands the application of all-fiber OFDI technology from static to dynamic scenes. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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16 pages, 9702 KiB

Open AccessArticle

Method and Installation for Efficient Automatic Defect Inspection of Manufactured Paper Bowls

by Shaoyong Yu, Yang-Han Lee, Cheng-Wen Chen, Peng Gao, Zhigang Xu, Shunyi Chen and Cheng-Fu Yang

Photonics 2023, 10(6), 686; https://doi.org/10.3390/photonics10060686 - 14 Jun 2023

Viewed by 850

Abstract

Various techniques were combined to optimize an optical inspection system designed to automatically inspect defects in manufactured paper bowls. A self-assembled system was utilized to capture images of defects on the bowls. The system employed an image sensor with a multi-pixel array that [...] Read more.

Various techniques were combined to optimize an optical inspection system designed to automatically inspect defects in manufactured paper bowls. A self-assembled system was utilized to capture images of defects on the bowls. The system employed an image sensor with a multi-pixel array that combined a complementary metal-oxide semiconductor and a photo detector. A combined ring light served as the light source, while an infrared (IR) LED matrix panel was used to provide constant IR light to highlight the outer edges of the objects being inspected. The techniques employed in this study to enhance defect inspections on produced paper bowls included Gaussian filtering, Sobel operators, binarization, and connected components. Captured images were processed using these technologies. Once the non-contact inspection system’s machine vision method was completed, defects on the produced paper bowls were inspected using the system developed in this study. Three inspection methods were used in this study: internal inspection, external inspection, and bottom inspection. All three methods were able to inspect surface features of produced paper bowls, including dirt, burrs, holes, and uneven thickness. The results of our study showed that the average time required for machine vision inspections of each paper bowl was significantly less than the time required for manual inspection. Therefore, the investigated machine vision system is an efficient method for inspecting defects in fabricated paper bowls. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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18 pages, 12232 KiB

Open AccessArticle

An Aero-Optical Effect Analysis Method in Hypersonic Turbulence Based on Photon Monte Carlo Simulation

by Bo Yang, He Yu, Chaofan Liu, Xiang Wei, Zichen Fan and Jun Miao

Photonics 2023, 10(2), 172; https://doi.org/10.3390/photonics10020172 - 07 Feb 2023

Viewed by 1506

Abstract

Aero-optical effects caused by hypersonic turbulence will affect the accuracy of optical sensors on aircraft. Traditional analysis methods, which do not consider absorption and scattering effects, cannot easily be used to completely describe the transmission process of light in hypersonic turbulence. In this [...] Read more.

Aero-optical effects caused by hypersonic turbulence will affect the accuracy of optical sensors on aircraft. Traditional analysis methods, which do not consider absorption and scattering effects, cannot easily be used to completely describe the transmission process of light in hypersonic turbulence. In this paper, an aero-optical effect analysis method based on photon Monte Carlo simulation (MC-AOEA) was proposed to explain the distortion characteristics of aero-optical effects from the perspective of photon statistics. The energy distribution of photons in the transmission process was determined by taking a photon packet as a unit, and the microscopic statistics of the photon dissipation energy for all photon packets were calculated. The effectiveness of this method was verified by comparing the photon statistical parameters with the traditional optical distortion physical quantities. MC-AOEA was used to analyze the distortion of aero-optical effects at different altitudes and speeds. Additionally, the simulation results showed that, with the reduction in flight altitude and the enhancement of speed, the distortion of aero-optical effects was aggravated, and the energy loss was more serious, which provides a reference for the evaluation of aero-optical effect errors. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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8 pages, 2358 KiB

Open AccessCommunication

Nondestructive Thickness Measurement of Thermal Barrier Coatings for Turbine Blades by Terahertz Time Domain Spectroscopy

by Longhai Liu, Haiyuan Yu, Chenglong Zheng, Dongdong Ye, Wei He, Silei Wang, Jining Li, Liang Wu, Yating Zhang, Jianhua Xie and Jianquan Yao

Photonics 2023, 10(2), 105; https://doi.org/10.3390/photonics10020105 - 19 Jan 2023

Cited by 4 | Viewed by 2127

Abstract

Owing to its high penetrability with dielectric materials, terahertz time domain spectroscopy (THz-TDS) is a promising nondestructive measurement technology. The coating thickness deviation and defect of thermal barrier coatings (TBC) will affect its thermal insulation performance and lifetime. In this work, THz-TDS was [...] Read more.

Owing to its high penetrability with dielectric materials, terahertz time domain spectroscopy (THz-TDS) is a promising nondestructive measurement technology. The coating thickness deviation and defect of thermal barrier coatings (TBC) will affect its thermal insulation performance and lifetime. In this work, THz-TDS was applied to measure the coating thickness distribution of TBC. The refractive index was obtained by THz-TDS transmission mode. To avoid the normal incidence THz signal loss, the THz signal was reflected from the TBC with a 10° incident angle, which also made the measurement result insensitive to the unevenness and tilt of the TBC sample. In the experiment, the yttria-stabilized zirconia (YSZ) TBC was measured by THz-TDS to estimate the thickness distribution. To validate the thickness measurements, metallography was introduced to correlate the TBC thickness result. The measurement deviation was within 12.1 µm, i.e., 3.45% for the THz-TDS and metallography result. A piece of turbine blade was measured by THz-TDS and a eddy current test. The maximum deviation was 8.48 µm, i.e., 2.36% of these two methods. Unlike the eddy current test, the THz-TDS thickness result was not affected by the cooling holes. The effectiveness of the nondestructive thickness measurement of TBC for turbine blades by THz-TDS was verified. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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9 pages, 2749 KiB

Open AccessCommunication

Optimal Design of Segmented Planar Imaging System Based on Rotation and CLEAN Algorithm

by Zhizi Ming, Yang Liu, Shanchuang Li, Mengchen Zhou, Haoran Du, Xiaochun Zhang, Yong Zuo, Jifang Qiu, Jian Wu, Lu Gao and Ze Zhang

Photonics 2023, 10(1), 46; https://doi.org/10.3390/photonics10010046 - 02 Jan 2023

Cited by 1 | Viewed by 1160

Abstract

We propose a parity-baseline segmented planar imaging method with more frequency components by changing different baseline selection to achieve better imaging in the rotational process. A theoretical model of the parity-baseline segmented planar imaging system with rotational operation is built to analyze the [...] Read more.

We propose a parity-baseline segmented planar imaging method with more frequency components by changing different baseline selection to achieve better imaging in the rotational process. A theoretical model of the parity-baseline segmented planar imaging system with rotational operation is built to analyze the imaging effect. The simulation results show that the imaging quality of the parity-baseline segmented planar imaging system has an approximately 20% increase by rotation compared with the conventional system. In addition, the CLEAN algorithm in radio astronomy imaging is also applied to the parity-baseline segmented planar imaging system, and the image quality is further improved by 55%. Such a new imaging method holds great potential toward astronomical observation and detection. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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8 pages, 2406 KiB

Open AccessCommunication

Dynamic Tunable Meta-Lens Based on a Single-Layer Metal Microstructure

by Xiangjun Li, Huadong Liu, Xiaomei Hou and Dexian Yan

Photonics 2022, 9(12), 917; https://doi.org/10.3390/photonics9120917 - 29 Nov 2022

Cited by 1 | Viewed by 1192

Abstract

Ultra-thin focusing meta-lenses based on the metasurface structure with adjustable focal length show important applicant value in compact systems, especially in on-chip terahertz spectroscopy, imaging systems, and communication systems. A stretchable substrate, dynamic focusing meta-lens based on the cross-polarized metal C-shaped split ring [...] Read more.

Ultra-thin focusing meta-lenses based on the metasurface structure with adjustable focal length show important applicant value in compact systems, especially in on-chip terahertz spectroscopy, imaging systems, and communication systems. A stretchable substrate, dynamic focusing meta-lens based on the cross-polarized metal C-shaped split ring resonators (SRRs) is designed and investigated. At the operation frequency of 0.1 THz, the operation characteristics of the unit cell structure and the formed meta-lens are investigated. The phase of the unit cell structures can be modulated by changing the rotation angle, width, and symmetry axis of the C-shaped metal SRRs. When the terahertz wave is incident vertically, the focusing performance can be achieved based on the specific arrangement of the metasurface unit cells. By stretching the flexible substrate of the meta-lens, the dynamic focusing effect can be realized. When the substrate stretches from 100% to 120%, the focal length changes from 59.8 mm to 125.2 mm, the dynamic focusing range is 109.4% of the minimum focal length, and the focusing efficiency changes between 5.5% and 10.5%. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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8 pages, 2189 KiB

Open AccessCommunication

Surface Curvature Sensor Based on Intracavity Sensing of Fiber Ring Laser

by Liang Yi, Zhifei Xue, Yiyun Ding, Min Wang, Zekang Guo and Jia Shi

Photonics 2022, 9(10), 781; https://doi.org/10.3390/photonics9100781 - 20 Oct 2022

Cited by 2 | Viewed by 1149

Abstract

The measurement of surface curvature is of great significance in aerospace, structural health monitoring, energy batteries, etc. In this paper, a fiber-optic surface curvature sensor, based on intracavity sensing of fiber ring laser (FRL), is experimentally demonstrated. A no-core fiber- based filter performs [...] Read more.

The measurement of surface curvature is of great significance in aerospace, structural health monitoring, energy batteries, etc. In this paper, a fiber-optic surface curvature sensor, based on intracavity sensing of fiber ring laser (FRL), is experimentally demonstrated. A no-core fiber- based filter performs as the sensing head of the FRL sensor. The response between the curvature of the NCF and the output wavelength of the FRL was investigated. In the measurement of curvature, the sensor system showed a narrow 3-dB bandwidth of 0.08 nm, with a high signal-to-noise ratio of about 60 dB. The curvature sensitivities were measured as −0.348 nm/m⁻¹ within 0.2 m⁻¹, and −3.185 nm/m⁻¹ from 0.2 m⁻¹ to 0.475 m⁻¹. The performance of the surface curvature sensor was characterized by parameters, including output stability, temperature cross-sensitivity, and detection limit. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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8 pages, 3613 KiB

Open AccessCommunication

Synchronization of Optomechanical Oscillators in Coupled 1D Optomechanical Crystal Nanobeam Cavities

by Yang Liu, Fei Gao, Daquan Yang, Aiqiang Wang, Mengchen Zhou, Shanchuang Li, Lu Gao and Ze Zhang

Photonics 2022, 9(10), 743; https://doi.org/10.3390/photonics9100743 - 09 Oct 2022

Viewed by 1202

Abstract

We proposed a new optomechanical system (OMS) based on parallel suspended one-dimensional optomechanical crystal (1D-OMC) nanobeam cavities for optomechanical synchronization. The optomechanical oscillators (OMOs) were spaced apart by an air-slot gap and coupled through optical radiation fields. The numerical simulation showed that the [...] Read more.

We proposed a new optomechanical system (OMS) based on parallel suspended one-dimensional optomechanical crystal (1D-OMC) nanobeam cavities for optomechanical synchronization. The optomechanical oscillators (OMOs) were spaced apart by an air-slot gap and coupled through optical radiation fields. The numerical simulation showed that the evolution process of 1D-OMC nanobeam cavities to mechanical synchronization could be divided into three clear stages. The synchronization of two mechanical breathing modes at 5.8846 GHz was achieved by using a single laser source. Finally, we investigated the relationship between the threshold power and detuning of an input laser for self-sustaining and synchronization states. Such chip-based structures hold great potential for large-scale synchronized oscillator networks. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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Review

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20 pages, 3590 KiB

Open AccessReview

Fiber Laser Sensor Configurations for Refractive Index, Temperature and Strain: A Review

by D. Jauregui-Vazquez, J. A. Alvarez-Chavez, T. Lozano-Hernandez, J. M. Estudillo-Ayala, J. M. Sierra-Hernandez and H. L. Offerhaus

Photonics 2023, 10(5), 495; https://doi.org/10.3390/photonics10050495 - 26 Apr 2023

Cited by 1 | Viewed by 2054

Abstract

Fiber laser sensors have been present for almost four decades as versatile sensing devices with a simple demodulation process, high sensitivity, and competitive resolution. This work discusses the most representative fiber laser sensor configurations employed for detecting critical parameters such as temperature, refractive [...] Read more.

Fiber laser sensors have been present for almost four decades as versatile sensing devices with a simple demodulation process, high sensitivity, and competitive resolution. This work discusses the most representative fiber laser sensor configurations employed for detecting critical parameters such as temperature, refractive index, and strain. However, essential information about other interesting parameters that have been measured is considered in this manuscript. Concurrently, the sensing elements and principle operation are described. Furthermore, these configurations are analyzed in terms of their principle of operation, sensitivity, gain medium, and wavelength operation range. According to the literature reviewed, fiber laser sensors offer the possibility of new interrogation techniques and simultaneous, independent detection. Considering interferometric fiber sensors, the fiber laser sensors offer high brightness, good output power, and high resolution. As a result, it is demonstrated that fiber laser sensors are a robust alternative for multiple sensing applications. Full article

(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)

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