Optical wavelet matched filter

A shift-invariant optical continuous wavelet transform is used for pattern recognition. We propose an Voptical wavelet matched filter that performs optical wavelet transforms for edge enhancement and the correlation between two wavelet transforms in a single step. This new bandpass matched filter shows improved discrimination capability with respect to the conventional matched filter and improved signal-to-noise ratio with respect to the phase-only matched filter. The wavelet matched filter provides flexibility of an adaptive choice of the scale factors of the wavelets that permit the selection of size and orientation of the smoothing function used in edge enhancement and the optimization of the performance of the filter. Optical experimental results are shown.     

Constrained digital matched filter method for optimum filter synthesis

We present a new method to directly calculate the optimum filter in presence of any additive stationary noise, with arbitrary time and domain constraints (flat-top, zero-area, etc.). A more concise re-deduction of digital penalized LMS method (DPLMS) is given. This method is fully developed, and synthesis results of a typical situation are given and compared with the DPLMS method. Optimum filter can be synthesized without a prior knowledge of the noise power spectral density, which makes it suitable to be used in adaptive, self-calibrating digital spectroscopy.     

自聚焦DOG子波变换匹配滤波器

为改善图像的相关识别性能,提出一种自聚焦子波变换匹配滤波器。用计算全息制作该匹配滤波器时,引入DOG子波函数,以达到锐化相关峰的目的。模拟计算结果表明,对于不同子波函数,其伸缩因子都存在一个最佳滤波范围,当伸缩因子在最佳因子范围内时,相关峰最尖锐,信噪比是传统相关峰信噪比的5.8倍。引入二次相位因子使匹配滤波器具有自聚焦功能,从而简化了光路。     

Two-channel phototurbidity sensors

Translated from Izmeritel'naya Tekhnika, No. 5, pp. 21–23, May, 1992.     

自适应空域矩阵滤波在匹配场定位中的应用

匹配场定位问题中,为了不影响观测结果,需要抑制观测区域存在的干扰。广义空域滤波在抑制拖曳舰船噪声及类似已知干扰的问题上起到了很好的效果,但对于强干扰或未知干扰声源信息的情况,需要寻找一种新的方法。波束形成目标方位估计问题中的自适应空域矩阵滤波器设计方法可以用来解决这一问题。对自适应空域矩阵滤波器增加稳健性约束处理后,针对匹配定位问题做了大量仿真实验,比较了广义空域矩阵滤波器和自适应空域矩阵滤波器对干扰的抑制效果。实验结果表明,如果选取正确的通带范围,自适应空域矩阵滤波在匹配场定位应用中可以非常有效地抑制未知强干扰。     

Scale-invariant binary phase-only matched filter using a ferroelectric-liquid-crystal spatial light modulator

We describe the implementation of a scale-invariant binary phase-only matched filter using a 128 × 128 ferroelectric spatial light modulator. A 5-dB discrimination was obtained between a 10-image training set of highly correlated characters (E's and F's) over a scale range of 1.0 to 1.5.     

Two-channel sequential single-molecule measurement

Experimental results are given which demonstrate the sequential detection of single molecules with a measurement efficiency of near unity. IR140 dye molecules are detected in sequential probe volumes within a flowing stream through a 9 μm i.d. capillary. The measurement of single molecules was confirmed by means of autocorrelation, photobleaching, visual observation, and cross-correlation analysis. The number of single molecules photobleached prior to being measured in the second probe region was in excellent agreement with the bulk studies described by a photodestruction curve. A cross-correlation peak with a temporal delay corresponding to the interprobe volume transit time and a width in agreement with parabolic flow give a clear indication of sequential detection. The near unity measurement efficiencies for both channels indicates the great potential for rapid quantitative analysis of dilute solutions.     

匹配滤波器中参考目标位置对相关峰位置的影响

针对利用光学相关器识别运动多目标的精确定位问题,提出了参考图像目标置中的匹配滤波器设计方法.该方法根据场景图像中目标位置、匹配滤波器中参考目标位置和相关峰位置之间的关系,采用将目标放置在参考图像中心以克服单一目标和运动多目标识别过程中相关峰的不确定偏移.实验结果表明,在范德卢格特型光电混合相关器中,采用该方法设计匹配滤波器可以使相关峰位置与目标位置一一对应,并且能够直观的实时显示出被识别目标在场景图像中的位置,提高了运动目标的定位准确性和跟踪稳定性.     

Two-dimensional wavelet transform achieved by computer-generated multireference matched filter and Dammann grating

A two-dimensional wavelet transform is optically performed in real time by use of a new multichannel system that processes the different daughter wavelets separately. The system, which is able to handle every wavelet function, relies on a Dammann grating for generating a multichannel array. All channels are processed in parallel by a conventional two-dimensional correlator. Experimental results applying Morlet-wavelet decomposition are presented.     

On improving the performance of a matched filter in a multipath channel

Abstract

In transmitting a signal via a multipath channel, the subsidiary signals carried by this channel could be useful in some applications. In this paper, a general theorem on optimally combining a certain number of related signals using diversity techanique is first cited. An adaptive technique suitable for a matched filter operating in a Rayleigh fading multipath channel is then proposed according to this theorem. This scheme can be further simplified under large output signal‐to‐noise ratio assumption.     

A hybrid multiuser detector for DS-UWB systems with matched filter and error-bit recognizer

In this article, we propose a hybrid algorithm of multiuser detection (MUD) for direct sequence ultra-wideband (UWB) communication systems, based on matched filters (MF) and error-bit recognizers (ER). The ER embraces three steps: bit mapping, K-means clustering, and sign judgment. In this detector, we construct a mapping function and map the output base-band bits from MFs into a one-dimensional feature space to get the amplitude information. After that, we set an initial value and classify the bits into right bits and wrong ones by K-means clustering. Finally, we make the sign judgment to prevent some right bits being picked out as wrong bits and correct the wrong bits to reduce the bit error rate (BER) of the system. Compared to a conventional detector based on MFs and minimum mean square error detector, to a large extent, our detector can improve the BER performance of a system because of high recognition probability of the wrong bits in K-means clustering. What is more, the simulation results show that the proposed hybrid MUD is not sensitive to the number of users. It can achieve a good BER performance and low computational complexity when there are 20 UWB transmitters in the channel.     

Two-channel frequency converter with quartz filters

Conclusion The method described for reproducing phase shifts between two voltages at elevated and high frequencies can be recommended as a beginning in constructing standard phase measuring apparatus.Theoretical investigations have shown that the error in the method can be reduced to 0.04–0.05°.Translated from Izmeritel'naya Tekhnika, No. 3, pp. 60–62, March, 1969.     

Small-scale self-focusing in a tapered optical beam

The analysis of Bespalov and Talanov concerning small scale self-focusing or filamentation effects for plane waves is generalized to a tapered beam case in this paper. A model of nonlinear phase and amplitude perturbations different from Siegman's is suggested. The previous conclusion that self-focusing is very ineffectual for strongly tapered, both divergent and convergent, beams in optical Kerr media as compared to small-scale self-focusing in plane waves is found to be inappropriate. Moreover, the different conditions of phase matching in cases of cylindrical and spherical waves are explicated, which could throw some light on the issue.     

Two-channel self-mixing laser Doppler measurement with carrier-frequency-division multiplexing

We demonstrate real-time two-channel self-mixing laser-Doppler measurement with extreme optical sensitivity using a laser-diode-pumped thin-slice LiNdP4O12 laser. Successful carrier-frequency-division-multiplexed two-channel operations are realized by using one laser, two sets of optical frequency shifters, and a two-channel frequency-modulated-wave demodulation circuit. Simultaneous independent measurements of vibrations of speakers and averaged motions of small Brownian particles in different scattering cells are demonstrated. Self-mixing photon correlation spectroscopy of particle size distributions is also discussed.     

Two-channel interferometer based on inter-laser detection of reflected radiation

A novel laser interferometer is proposed. It successively generates two quadrature output signals at a high carrier frequency, combining a two-beam principle with a point spread function possessing a high slope. The interferometer is based on a dual-mode Zeeman He−Ne laser with a wavelength of 3.39 μm. It is used to present experimental investigations of an erosion capillary discharge in air produced by means of a grind-faced graphite employed as the reflector. Translated from Izmeriell’naya Tekhnika, No. 7, pp. 36–39, July, 1999.