KEYWORDS: Fluorescence, Temperature metrology, Design, Temperature sensors, Data processing, Signal filtering, Signal attenuation, Optical fibers, Tunable filters, Optical engineering
Optical fiber temperature sensors based on fluorescence lifetime are widely utilized in a multitude of fields. The integral ratio method (IRM) and fast Fourier transform (FFT) method are the most commonly employed techniques for obtaining fluorescence lifetime. However, both methods have been found to have insufficient precision to varying degrees. We employed the extended Kalman filter (EKF) algorithm to fit the fluorescence attenuation curve, and the weighted linear least squares method is utilized to obtain a more accurate fluorescence lifetime. A comprehensive hardware system is fabricated for verification purposes. The software simulation demonstrates that the EKF algorithm enhances the precision of the fluorescence attenuation curve by up to 96.469%. The results of the test demonstrate that the temperature sensor we proposed has a resolution of 0.07°C. In comparison to the IRM and FFT methods, we enhanced the average accuracy of the fluorescence lifetime by 17.819% and 4.626%, respectively, whereas the average deviation of the temperature is reduced by 80.224% and 54.701%, respectively. We provide an effective way for the algorithm design of high-accuracy optical fiber temperature sensors based on fluorescent lifetime.
A single-photon avalanche photodiode (SPAD) is a type of photodiode that operates using the avalanche effect to detect light down to the single photon level. When SPAD detects photons, it generates a massive avalanche of charges which can damage the diode. The quenching circuit prevents these problems by quickly limiting the current flowing through the diode and reducing the avalanche effect. This paper designs an improved SPAD active quenching circuit model. This model introduces an avalanche self-sustaining module to increase the quenching time of SPAD, so that the reverse bias voltage can be well quenched. The simulation results of the improved circuit model and the traditional quenching circuit model are compared in detail by using Cadence PSpice. Set the photon incident time to 500ps, and the reverse bias voltage to 73V. Simulation results show that the improved model can be quenched to 70.051V, unfortunately, the traditional model can only be quenched to 72.848V. Thus, the improved active quenching equivalent circuit model has short recovery time and better quenching effect. It can be used to simulate SPADs with high temporal resolution.
The online temperature monitoring of high voltage switchgear is of great significance to the safe operation of power system. However, the sensitive signal of the traditional active temperature sensor is electrical signal, which is susceptible to the interference of external electromagnetic signals, resulting in a decrease in accuracy. The sensitive signal of fluorescent optical fiber temperature sensor is optical signal, which is completely insulated from the external electromagnetic signal. In addition, the optical signal is safer than the electrical signal in the high-voltage field. Therefore, the fluorescence optical fiber temperature sensor based on the principle of photoluminescence for high-voltage switchgear is realized in this paper. The Fast Fourier Transform (FFT) algorithm is used by the sensor to calculate the fluorescence lifetime. The experimental data show that when the temperature increases from 29 ℃ to 102 ℃, the fluorescence lifetime decreases from 2.6864 ms to 2.2246 ms, and the temperature sensitivity is about 6 us/℃. The fluorescence lifetime has a good linear relationship with temperature. In summary, the fluorescent optical fiber temperature sensor has application value in the field of high voltage switchgear.
For traditional active temperature sensors, the accuracy is reduced under strong electromagnetic conditions, and in high voltage situations, there may be dangers such as electric sparks exploding. Therefore, a fluorescence lifetime optical fiber temperature sensor capable of operating in a series of complex environments such as strong electromagnetic, high voltage, and deep sea has been developed. This paper mainly introduces the system structure and data processing algorithm of the fluorescent fiber optic temperature sensor, and completes the experimental prototype. After preliminary calibration test, accurate measurement of 20-60°C has been achieved with an accuracy of ±0.6°C, and it has good stability and repeatability. It is well suited for use in the medical field, providing a reliable, low-cost solution for temperature sensing in the medical field.
In this paper, an improved photodetector structure, finger-interdigitated MOS type composite optoelectronic photodetector is designed. We did not change the original structure of the MOS device. The back gate effect of the MOS structures and the electronic current of the photodiode is used in an ingenious combination. Compared with conventional multi-finger diodes, It has higher responsiveness and simpler readout circuitry
KEYWORDS: Time of flight cameras, Sensors, Binary data, Near infrared, Image restoration, Cameras, 3D-TOF imaging, Electronic imaging and signal processing, Amplitude modulation, Modeling and simulation, Active optics
Time-of-flight cameras use the flight time of light to obtain accurate depth information, but its accuracy is affected by multipath interference. In the penalty function method adopted in this study, the best initial iteration point is obtained by cross-correlation of a pseudo-random binary sequence and its displacement sequence, and a continuous and non-segmented exponential penalty (obstacle) function is constructed, which can be used for sparse decomposition of high-dimensional vectors. These two improvements make the penalty function method applicable to sparse decomposition in the multipath separation process. Moreover, under the same measurement times and operation speeds, the improved penalty function method is nearly twice as accurate as the orthogonal matching pursuit algorithm in multipath separation.
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