In this work, a novel tunable diaphragm structures are designed as sensing diaphragms for ultrasonic sensors. The natural frequency and sensitivity of the new structure diaphragms is simulated by finite element method. The proposed membrane structures is outer-ring clover (ORC) structure. Typically, an increase in membrane sensitivity is accompanied by a decrease in its natural frequency. However, this can be significantly mitigated by the proposed structures, which can exhibit notable structural optimization effects by simultaneously enhancing sensitivity and minimizing the reduction of the natural frequency. The simulation results indicate that, when the outer diameter and thickness remain unchanged, the sensor can achieve a maximum sensitivity improvement of 3.5 times and a reduction of 1.25 times in the natural frequency compared to the circular diaphragms (CD). Furthermore, ORC can be fabricated by micro-electromechanical systems (MEMS) technology, making it feasible for practical manufacturing and production. The sensing membrane is expected to be applicable in detection fields such as ultrasound partial discharge and underwater acoustics.
A Fiber Bragg Grating (FBG) based force sensor with high-sensitivity and temperature compensation capability. It can be used to accurately measure the contact force (CF) between medical equipment and tissues or organs in minimally invasive surgery (MIS). To achieve temperature compensation, a novel design incorporating dual elastomer-based dual FBGs is employed, and its effectiveness is verified through finite element simulation. After temperature compensation, the developed sensor has a sensitivity of 54 pm/N, a resolution of 0.019 N, and a root-mean-square error (RMSE) of 0.064 N. The utilization of temperature disturbances for measuring distal contact force demonstrates a substantial enhancement compared to direct measurement methods. Additionally, in vitro experiments are conducted using a silicone vascular model, demonstrating the sensor’s capability to detect certain alterations in vascular pathways. Finally, a simulated palpation liver experiment confirmed that the designed force sensor can preliminary detect of the relative hardness of the tissue based on the magnitude of the CF. In vitro experiments have proved that the designed FBG force sensor has a practical value in MIS.
To mitigate the failure of a Hilbert transform-based fixed-threshold multi-peak demodulation algorithm in distributed Fiber Bragg Grating (FBG) sensing systems with light noise, an adaptive multi-peak demodulation algorithm based on the Hilbert transform is proposed in this paper. The algorithm adopts the thought of Divide and Conquer, including reflection spectrum segmentation and single peak detection. Multiple sub-spectra of the FBG multi-peak spectrum is segmented by the Hilbert transform and calculating adaptive threshold method, and then the Gaussian fitting algorithm is used to achieve the precise positioning of the spectral peaks. Theoretical analyses and simulation results show that the algorithm using an adaptive threshold as a threshold of splitter can greatly improve the portability of the algorithm in complex situations, and improve the algorithm’s noise resistance, demodulation speed, and accuracy. It shows that the algorithm provides a new way of demodulation for distributed FBG sensing systems.
Robot grasping and manipulating objects rely on sensors for force magnitude and spatial detection entirely. The pressure sensor is one of the most basic sensors. Most of the existing pressure sensors are composed of rigid materials, relying on resistance, piezoelectricity, and capacitance principles. The sensors are sensitive to electromagnetic fields, which limits their applications largely. Simultaneously, the resolution of pressure sensors plays an essential role in precise measurements. Hence, we designed a flexible optical pressure sensor with high spatial resolution using flexible silicone as substrate, optical fibers for transmitting light, and a camera as the receiver of images. This optical sensor is not affected by electromagnetic fields, while the flexible materials achieve soft properties of the sensor. Deep learning can decipher pictures. As a result, the better Root Mean Square Error (RMSE) for localization is about 0.1 mm order of magnitude, and the normal force (Fz) is around 0.67 N. This work has contributed to sensors for flexible electronics and robotics.
Aiming at the much measurement error caused by spectral superposition in a high-speed sampling of GaAs optical fiber temperature sensing technology, a concept of equivalent wavelength based on the local area of the reflection spectrum is proposed. The principle of shifting the absorption edge of the gallium arsenide semiconductor materials' reflection spectrum to a longer wavelength with the increase of temperature is the basis of this concept. This paper proposes a new temperature demodulation method and data processing flow based on the analysis of the equivalent wavelength. The standard temperature measurement system in this paper has verified the accuracy and stability of the demodulation method. The experimental results show that the measurement error is less than ±0.2°C; in the temperature range of -20°C~60°C. In the temperature range of 60°C~250°C, the measurement error is less than ±0.5°C.
We propose and demonstrate an interferometric sensor based on visibility modulation. In the interferometric sensor, a section of
polarization maintain (PM) fiber is spliced into one arm as the sensing head. Due to the interference between the two beams in the two
arms, respectively, an interferometric fringe can be obtained. The birefringence of the PM fiber splits the beam in the sensing arm,
yielding a visibility envelop in the interferometric fringe. Strain applied on the PM fiber can be demodulated by measuring the
visibility change in a given wavelength. Experimental result shows that the sensor can achieve resolution of up to 28 nano-strain. This
demodulation scheme is immunity to the wavelength shift and power fluctuation of OSA, thus improving the accuracy of the sensor.
This type of sensor can be improved by using a wavelength-swept laser or a mode-locked fiber laser.
This paper develops a promising low-priced optical fiber arcing detection system for measuring pantograph-catenary contact-loss. The system collects the ultraviolet light by UV lens. The filter cuts off visible light to reducing environmental disturbance. Ultraviolet light of arcing is transformed to visible one by fluorescent material, which is packaged on the fiber endface and has a high transforming efficiency in ultraviolet band. This optical fiber arcing detection system is equipped with self-checking pulsed light to monitoring the status of the detection system. The arcing energy is estimated by the relationship between the intensity of ultraviolet light and the output voltage signal.
Abstract—This paper describes a MEMS-based tunable Fabry-Perot filter that can be directly integrated on a detector. The Fabry-Perot filter consists of two parallel mirrors and lets the light with particular wavelength pass through. The wavelength depends on the gap between the mirrors. The gap of the micromechanical Fabry-Perot filter can be changed by applying a voltage to the mirrors, an electrostatic force inducing an attraction between the substrate and the top mirror. Based on the comprehensive analysis of the working principle of the micro F-P cavity filter, the optimum tuning scheme of micro F-P cavity filter is established. A simulation of the mechanical behavior was performed based on finite elements, using ANSYS software. We finally establish the L-arm type cantilever to support cavity structure, the micro-bridge can achieve a considerable range of tuning; relatively high fill factor, filter light leakage is avoided; the high abilityto keep parallel can achieve high precision filtering effect; structural stability, it can resist the residual stress of manufacture. This MEMS F-P tunable filter can be a potential application in spectroscopic sensing and optical communication system.
This paper proposed a solution about low cost multi-channels Gallium Arsenide (GaAs) absorption-based fiber optic
temperature sensing system, which can get specific channel temperature information at pre-set time slots by combining
time division multiplexing technology and fiber optic multiplexing module. Established an seven channels fiber optic
temperature sensing system using only one spectrum analysis unit and achieved -/+ 1°C temperature resolution, 2Hz
measuring frequency at temperature range from 0°C to 150°C.
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