共查询到20条相似文献,搜索用时 0 毫秒
1.
N. Demoli 《Optics & Laser Technology》1994,26(2)
The dependence of the output correlation signal on the filter parameters, filter types, and signal types in matched filtering is discussed. On the basis of the established filter criteria—the signal-to-noise ratio, peak-to-sidelobe ratio, and diffraction efficiency—a new measure is introduced giving an overall estimate of the feasibility of filters. According to that single measure, various filter types are compared and selected by numerical experiments. 相似文献
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A polychromatic correlation detection technique by complex spatial filtering is presented. This technique utilizes a diffraction grating and three co-lineared (red, green, and blue) coherent sources. The technique of complex spatial filter synthesis for the polychromatic corelation detection is demonstrated. This technique offers true color correlation detection which is very suitable for color signal recognition and identification. The correlation diffraction efficiency with this technique is generally higher than that of the wavelength-multiplexed technique. Several interesting experimental demonstrations of this color signal correlation detection scheme are provided. Finally we note that this color signal detection technique is a simple and versatile processing technique which has broad range of applications of complex color signal detection, recognition and identification. 相似文献
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The synthesis of a matched spatial filter based on holographic methods requires that the spatial frequency band in which the holographic fringe pattern with the best modulation is formed be tuned to the appropriate weighting at the Fourier transform plane of the spatial frequencies of the input object to be studied. For this purpose both the spectral intensity distribution of an input object at the Fourier transform plane and the intensity distribution of a reference beam at that plane must be accurately known beforehand. A two-dimensional diffraction pattern sampling system has been constructed which enables the Fourier spectral intensity distribution of the input object and the reference beam intensity distribution to be faithfully recorded. A preliminary experimental study shows the usefulness of this system. 相似文献
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Results of theoretical and model studies of the probabilistic characteristics of signal detection by a spatial correlation filter are described. A mathematical model of signal processing in the spatial correlation filter is presented. Expressions for estimating the detection probability, missed detection probability, false alarm probability, and threshold level, as well as expressions for choosing the optimal filter parameters to obtain preset probability characteristics, are derived on the basis of this model. Results of computer simulation of the probabilistic characteristics of signal detection by spatial correlation filters with random arrays are shown to corroborate the theoretical findings obtained within the model. 相似文献
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In this paper we demonstrate image processing techniques such as edge enhancement and phase contrast by using an optically addressed liquid crystal spatial light modulator (OASLM) in the frequency plane of an optical 4f processor. The transfer function of the device is derived on the basis of the Jones formalism. Faced with a lack of a general theory for such non-linear optical processors, we show that an analogy to the propagation of optical pulses in fibres is helpful for the understanding of the image processing operation. 相似文献
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An optimized strain demodulation method based on dynamic double matched fiber Bragg grating filtering 总被引:2,自引:0,他引:2
Biqiang Jiang Jianlin Zhao Chuan Qin Zhao Huang Fan Fan 《Optics and Lasers in Engineering》2011,49(3):415-418
An optimized strain demodulation method based on dynamic double matched fiber Bragg grating (FBG) filtering driven by a piezoelectric transducer (PZT) is proposed and experimentally demonstrated. Using an optimized triangular waveform to drive PZT, the nonlinear effect is eliminated, and extraction and processing of the peak signals are more convenient. Furthermore, taking advantage of double matched-FBGs and strain amplification structure to demodulate the Bragg wavelength, the wavelength scanning range can be extended to 6.3 nm, so that a large-scale and high-precision strain measurement can be achieved. The experimental results show that in the strain range of 0-3800με, the linearity of the relationship between strain and scanning time-difference is greater than 99.8%, and the stability of repeated measurements is up to 99.5%. This demodulation method can be widely applied in the FBG measurement system. 相似文献
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We demonstrate experimentally >3 dB extinction ratio improvement at the output of SOA-based delayed-interference signal converter (DISC) using optical off-centered filtering. Through careful modeling of the carrier and the phase dynamics, we explain in detail the origin of sub-pulses in the wavelength converted output, with an emphasis on the time-resolved frequency chirping of the output signal. Through our simulations we conclude that the sub-pulses and the main-pulses are oppositely chirped, which is also verified experimentally by analyzing the output with a chirp form analyzer. We propose and demonstrate an optical off-center filtering technique which effectively suppresses these sub-pulses. The effects of filter detuning and phase bias adjustment in the delayed-interferometer are experimentally characterized and optimized, leading to a >3 dB extinction ratio enhancement of the output signal. 相似文献
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Estimation of the far-field centre is carried out in beam
auto-alignment. In this paper, the features of the far-field of a
square beam are presented. Based on these features, a phase-only
matched filter is designed, and the algorithm of centre estimation
is developed. Using the simulated images with different kinds of
noise and the 40 test images that are taken in sequence, the
accuracy of this algorithm is estimated. Results show that the error
is no more than one pixel for simulated noise images with a 99%
probability, and the stability is restricted within one pixel for
test images. Using the improved algorithm, the consumed time is
reduced to 0.049s. 相似文献
14.
P. Cielo 《Optics & Laser Technology》1983,15(3):145-149
Some optical techniques for surface inspection applications are described. Paper texture is analyzed by a frustrated-total-internal-reflection method followed by spatial filtering of the diffracted pattern. Fibre-optics and micro-lenses are used to obtain a rugged and flexible sensor. Similar sensors are used for defect monitoring of roughly-polished surfaces. The practical aspects of sensor manufacture, speckle and vignetting considerations are discussed. 相似文献
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基于矩孔光学傅里叶变换的匹配滤波器缩放比例标定方法研究 总被引:1,自引:1,他引:0
为了使待识别目标的傅里叶变换频谱与匹配滤波器频谱分布严格重合,提出了一种基于矩孔图像光学傅里叶变换的匹配滤波器缩放比例标定方法。针对范德卢格特型光学相关器,在分析场景空间光调制器傅里叶变换频谱分布的基础上,以矩孔图像的频谱间距作为基准标定匹配滤波器的缩放比例;并利用焦距为400mm的傅里叶透镜作为一个实例,计算出其匹配滤波器缩放比例为1.068,对标定结果进行了实验验证。结果表明,此方法适用于范德卢格特型光学相关器中匹配滤波器的缩放比例标定,能够有效提高相关峰的能量和信噪比。 相似文献
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The capabilities of a one-dimensional filtering method for the detection of defects in periodic structures are derived by
a detailed theoretical analysis. The signal-to-noise ratio is evaluated as a function of system parameters and a way is described
to overcome the disturbing effect of phase defects. Finally, an extremely simple system is described which demonstrated the
detection of defects below 2 μm. This demonstrated detection capability was limited by the available test mask and not by
the detection system.
This work was partially supported by “Kulso” Ltd. 相似文献
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We present a novel way to produce squeezed light in an optical cavity. The main idea is to transfer vibrational squeezing from the motion of a trapped ion to the photons in a cavity. We use the dipolar coupling of the motion of a three-level ion with one cavity mode and two different kind of pumps. The first pump is an oscillating electric field that drives the ion into a vibrational squeezed state. The second pump consists of two lasers resonant with the ionic levels that makes the transfer possible. 相似文献
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《Optics Communications》1987,64(2):89-93
In thermal lens spectroscopy, the application of a circular stop can result in reducing the constant background illumination of a detector, while only slightly affecting the thermal lens signal. Improvement of the signal to background ratio in the filtered detection of thermal lensing is estimated and its relation to S/N in thermal lens spectrometer is discussed. An experiment with nearly threefold increase of useful signal to constant background ratio is reported. 相似文献