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本文研究了时间相干性对光学信息处理系统噪声演绩的影响.用Wolf的部分相干光理论评价了输出信噪比.用输出信噪比作为信息处理系统噪声演绩的度量.输入及傅里叶平面上记录介质的颗粒噪声及相位起伏作为两个主要的噪声源.结果表明,除了在输入平面上的颗粒噪声外,输出信噪比一般都可以通过使用时间部分相干照明而得到改善 相似文献
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CMOS图像传感器时间域噪声分析及其应用研究 总被引:1,自引:0,他引:1
针对目前CMOS探测器的噪声研究绝大部分采取频率域的分析方法,所得的结果对于实际的探测器应用指导性不强。从时间域出发,构建了全新的探测器噪声模型,分析了在探测器的不同工作时期内噪声量大小同时间的关系。给出了探测器工作时序的优化准则,积分时间越长,系统的信噪比增加,输出信号电压值增大,等效输入端信噪比不变,系统的动态范围减小;复位时间越短,输出噪声量越小,但是图像的滞后效应也就越严重,在对弱小目标进行成像时应该尽可能地减少复位时间,增大积分时间,对于亮目标成像,应该增大复位时间,减少积分时间。 相似文献
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为解决激光相干场成像系统探测器噪声相对总噪声的定量化占比估计问题,分析探测器噪声是否为主要噪声源,提出一种探测器噪声占比权重定量化分析计算方法.基于光电子统计方法得到系统信噪比方程,并引入信噪比中间参数估计方程,建立了探测器噪声相对总噪声的占比权重定量化计算模型.结合理论分析与实验测量进行验证,结果表明:针对构建的相干场成像实验系统,探测器噪声占比权重达52%,进一步分析可知实验在大气相对宁静的夜晚进行,系统受背景光噪声和湍流噪声影响小,探测器噪声是主要噪声源.所提方法可有效估算探测器噪声占比权重,具有便捷、高效的特点,可用于实际相干场成像系统探测器噪声定量化评估测量分析. 相似文献
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输入信号和噪声对单模激光随机共振的影响 总被引:3,自引:1,他引:2
采用色抽运噪声和实虚部间关联的量子噪声驱动的单模激光损失模型,运用线性化近似方法计算了周期性信号加性输入时激光系统的输出光强信噪比,发现用信噪比与量子噪声实虚部间关联系数的关系曲线描述的随机共振现象.在抽运噪声自关联为短时关联情况下,当信号振幅增大和频率增快、抽运噪声色关联时间增大时,系统的随机共振加强;而噪声强度的增加会削弱系统的随机共振.在抽运噪声自关联为长时关联情况下,当信号振幅增大和量子噪声强度减弱时,系统的随机共振加强;而信号频率、抽运噪声强度、抽运噪声色关联时间的变化对系统随机共振的影响很小. 相似文献
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《Optics Communications》1987,61(4):237-242
The effects of phase defects at the input plane of an optical correlator on the performance of the system under partially coherent illumination is investigated. The correlation signal-to-noise ratio (SNR) is evaluated as the criterion for the performance of the optical system. We study the effects of both spatially and temporally partially coherent illumination on the distorted correlation signal. It is shown that the output SNR can be increased by relaxing the coherence requirements of the system. The SNR dependence on noise variation is also investigated. It is found that the correlator becomes less sensitive to noise variations under partially coherent illumination. 相似文献
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《Chinese Journal of Physics (Taipei)》2018,56(4):1588-1598
Stochastic resonance (SR) is a vital approach to detect weak signals submerged in strong background noise, which is useful for mechanical fault diagnosis. The underdamped bistable SR (UBSR) is a kind of the most used SR, however, their potential structures are deficient to match with the complicated and diverse mechanical vibration signals and their parameters are selected subjectively which probably resulting in poor performance of UBSR. To overcome these shortcomings, this paper proposes an underdamped SR with exponential potential (UESR) which is generalized by using a harmonic model and a Gaussian potential (GP) model. The dynamics in UESR system is evaluated by the signal-to-noise ratio (SNR) which represents the effectiveness of noise utilization. Then, the effects of system parameters on system performance are investigated by output SNR versus noise intensity D for different parameters. Finally, the proposed method is used to process bearing experimental data and further perform bearing fault diagnosis. The experimental results demonstrate that a larger output SNR and higher spectrum peaks at fault characteristic frequencies can be obtained by the proposed method compared with the UBSR method, which confirm the effectiveness of the proposed method. 相似文献
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Effect of inertia mass on the stochastic resonance driven by a multiplicative dichotomous noise 下载免费PDF全文
A stochastic system driven by dichotomous noise and periodic signal is investigated in the under-damped case.The exact expressions of output signal amplitude and signal-to-noise ratio(SNR) of the system are derived.Numerical results indicate that the inertial mass greatly affects the output signal amplitude and the SNR.Regardless of whether the noise is symmetric or asymmetric,the inertial mass can influence the phenomenon of stochastic resonance(SR) of the system,leading to two types of resonance phenomenon:one is coherence-resonance-like of the SNR with inertial mass,the other is the SR of the SNR with noise intensity. 相似文献
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The stochastic resonance (SR) behavior for an underdamped bistable system driven by square-wave signal and multiplicative noise is investigated. Under the adiabatic approximation condition, the expression for the system output signal-to-noise ratio (SNR) is obtained. The analysis results show that stochastic multi-resonance phenomenon occurs when the SNR varies with the intensities of the multiplicative and additive noise. SR phenomenon can be observed on the curves of the SNR versus the system bias, versus the amplitude of the dichotomous noise and versus the amplitude of the square-wave signal. Moreover, the SNR varies non-monotonously with the variety of other system parameters. 相似文献
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Improvement of signal-to-noise ratio by stochastic resonance in sigmoid function threshold systems, demonstrated using a CMOS inverter 总被引:1,自引:0,他引:1
Michihito Ueda 《Physica A》2010,389(10):1978-2862
Stochastic resonance (SR) has become a well-known phenomenon that can enhance weak periodic signals with the help of noise. SR is an interesting phenomenon when applied to signal processing. Although it has been proven that SR does not always improve the signal-to-noise ratio (SNR), in a strongly nonlinear system such as simple threshold system, SR does in fact improve SNR for noisy pulsed signals at appropriate noise strength. However, even in such cases, when noise is weak, the SNR is degraded. Since the noise strength cannot be known in advance, it is difficult to apply SR to real signal processing. In this paper, we focused on the shape of the threshold at which SR did not degrade the SNR when noise was weak. To achieve output change when noise was weak, we numerically analyzed a sigmoid function threshold system. When the slope around the threshold was appropriate, SNR did not degrade when noise was weak and instead was improved at suitable noise strength. We also demonstrated SNR improvement for noisy pulsed voltages using a CMOS inverter, a very common threshold device. The input-output property of a CMOS inverter resembles the sigmoid function. By inputting the noisy signal voltage to a CMOS inverter, we measured the input and output voltages and analyzed the SNRs. The results showed that SNR was effectively improved over a wide range of noise strengths. 相似文献
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A linear system driven by correlated asymmetric dichotomous noises and periodic signal was investigated in the overdamped
case. The exact expressions of output signal amplitude and signal-to-noise ratio (SNR) of the system were derived. By means
of numerical calculations, we found that: (i) At some fixed multiplicative noise intensities, the output signal amplitude
with frequency exhibits the structure of a weak peak, even no peak as the dichotomous noise is asymmetric; (ii) In the case
of asymmetric dichotomous noise, the signal frequency can cause non-monotonous behavior of the output signal amplitude with
respect to multiplicative noise intensity; (iii) The curve of SNR with frequency has a weak peak and a trough in the case
of symmetric dichotomous noise, but no peak with asymmetric; (iv) Whether the multiplicative noise is symmetric or asymmetric,
the noise can enhance response of the system; (v) The SNR increases with the correlation strength between the two noises decreasing.
In addition, the plane of multiplicative noise intensity versus noise symmetric parameter was plotted. 相似文献
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Hwaling Harold Szu 《Optics Communications》1980,32(2):229-234
Simultaneous multiple-path looks at a moving object (MO) of low signal to noise ratio (SNR) is proposed using an array of telescopes without using either interferometric or adaptive optics techniques. Instead, proper Affine overlays, of all looks through nonisoplanatic regions, give a better SNR and a better turning view in the real time and image plane, and can be furthermore integrated temporally using Affine transformation to yield new templates of a MO. Thereby a scheme of open, self-taught and therefore smart pattern recognition of MO's becomes possible. The system performance of a multi-opto-sensor-Affine (MOSA) system is generally derived in terms of system parameters and field conditions. Geometric constructions of Affine transformations are shown to be either area-ration preserving among three control picture elements (pixels), which are proved to be sufficient using Euler's theorem of solid body motion, or the first order moment of area-ratio preserving, when more than three pixels are needed due to poor SNR. 相似文献
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太赫兹雷达系统在差频信号频谱分析过程中,干扰噪声影响其测距能力.针对上述问题,提出基于自适应随机共振理论的太赫兹雷达信号检测方法,通过对含噪差频信号进行二次采样,利用自适应随机共振系统提取信号,进行尺度恢复完成测距计算.实验数据显示,不同测量距离时,相较于快速傅里叶变换法,输出信噪比的平均增益为9.684 d B,其中测量距离为1000 mm处,差频信号初始频谱值提高了64.1倍,系统信噪比增益为11.761 d B;相较于滤波法,在测量距离为1000 mm处信噪比增益最大,提高了70.56%;输入噪声强度为1—5 V之间时,输出信噪比曲线的曲率相对于滤波法降低了86.5%,其中噪声强度为5 V时信噪比增益最大,为14.018 d B.实验表明太赫兹雷达系统的测距能力大幅提高. 相似文献
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This paper studies stochastic resonance (SR) phenomenon in a
parallel array of linear elements with noise. Employing the
signal-to-noise ratio (SNR) theory, it obtains the output SNR, and
investigates the effects on the output SNR of the system with
signal-independent noise and signal-dependent noise respectively.
Numerical results show: the curve of the output SNR is
monotone with signal-independent noise; whereas SR appears
with signal-dependent noise. Moreover, the output SNR enhances
rapidly with the increase of N which is the number of elements in
this parallel array linear system. This result may provide smart
array of simple linear sensors which are capable of acting as
noise-aided amplifiers. 相似文献
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Characteristics of piecewise linear symmetric tri-stable stochastic resonance system and its application under different noises 下载免费PDF全文
Gang Zhang 《中国物理 B》2022,31(8):80502-080502
Weak signal detection has become an important means of mechanical fault detections. In order to solve the problem of poor signal detection performance in classical tristable stochastic resonance system (CTSR), a novel unsaturated piecewise linear symmetric tristable stochastic resonance system (PLSTSR) is proposed. Firstly, by making the analysis and comparison of the output and input relationship between CTSR and PLSTSR, it is verified that the PLSTSR has good unsaturation characteristics. Then, on the basis of adiabatic approximation theory, the Kramers escape rate, the mean first-passage time (MFPT), and output signal-to-noise ratio (SNR) of PLSTSR are deduced, and the influences of different system parameters on them are studied. Combined with the adaptive genetic algorithm to synergistically optimize the system parameters, the PLSTSR and CTSR are used for numerically simulating the verification and detection of low-frequency, high-frequency, and multi-frequency signals. And the results show that the SNR and output amplitude of the PLSTSR are greatly improved compared with those of the CTSR, and the detection effect is better. Finally, the PLSTSR and CTSR are applied to the bearing fault detection under Gaussian white noise and Levy noise. The experimental results also show that the PLSTSR can obtain larger output amplitude and SNR, and can detect fault signals more easily, which proves that the system has better performance than other systems in bearing fault detection, and has good theoretical significance and practical value. 相似文献