The nonuniform distribution of interference spectrum in wavenumber k-space is a key issue to limit the imaging quality of Fourier-domain optical coherence tomography(FD-OCT).At present,the reconstruction quality at di...The nonuniform distribution of interference spectrum in wavenumber k-space is a key issue to limit the imaging quality of Fourier-domain optical coherence tomography(FD-OCT).At present,the reconstruction quality at different depths among a variety of processing methods in k-space is still uncertain.Using simulated and experimental interference spectra at different depths,the effects of common six processing methods including uniform resampling(linear interpolation(LI),cubic spline interpolation(CSI),time-domain interpolation(TDI),and K-B window convolution)and nonuniform sampling direct-reconstruction(Lomb periodogram(LP)and nonuniform discrete Fourier transform(NDFT))on the reconstruction quality of FD-OCT were quantitatively analyzed and compared in this work.The results obtained by using simulated and experimental data were coincident.From the experimental results,the averaged peak intensity,axial resolution,and signal-to-noise ratio(SNR)of NDFT at depth from 0.5 to 3.0mm were improved by about 1.9 dB,1.4 times,and 11.8 dB,respectively,compared to the averaged indices of all the uniform resampling methods at all depths.Similarly,the improvements of the above three indices of LP were 2.0 dB,1.4 times,and 11.7 dB,respectively.The analysis method and the results obtained in this work are helpful to select an appropriate processing method in k-space,so as to improve the imaging quality of FD-OCT.展开更多
Sampling is a bridge between continuous-time and discrete-time signals,which is import-ant to digital signal processing.The fractional Fourier transform(FrFT)that serves as a generaliz-ation of the FT can characterize...Sampling is a bridge between continuous-time and discrete-time signals,which is import-ant to digital signal processing.The fractional Fourier transform(FrFT)that serves as a generaliz-ation of the FT can characterize signals in multiple fractional Fourier domains,and therefore can provide new perspectives for signal sampling and reconstruction.In this paper,we review recent de-velopments of the sampling theorem associated with the FrFT,including signal reconstruction and fractional spectral analysis of uniform sampling,nonuniform samplings due to various factors,and sub-Nyquist sampling,where bandlimited signals in the fractional Fourier domain are mainly taken into consideration.Moreover,we provide several future research topics of the sampling theorem as-sociated with the FrFT.展开更多
本文将先进的DASP(Data Alias-free Signal Processing)抗混叠信号采样技术运用到现代测试仪器平台中。通过恰当地选取采样点位置和改进信号处理算法,解决了信号采样中以较少点重构高频信号的问题,该技术抗混叠和消除混叠频谱噪声的特...本文将先进的DASP(Data Alias-free Signal Processing)抗混叠信号采样技术运用到现代测试仪器平台中。通过恰当地选取采样点位置和改进信号处理算法,解决了信号采样中以较少点重构高频信号的问题,该技术抗混叠和消除混叠频谱噪声的特点允许它能准确检测到各个不同幅度的信号。研究表明DASP技术融入测试平台能以较低的采样率有效地提取高频信号,提高了测试精度和效率。展开更多
针对伪随机(PN)码调制的多普勒激光雷达中固有的对外差信号不能等间隔采样的问题,提出一种新的非均匀采样信号的离散傅里叶变换(DFT)方法。首先,给出距离速度同步测量多普勒激光雷达系统模型,指出对外差信号不能等间隔采样的原因;然后,...针对伪随机(PN)码调制的多普勒激光雷达中固有的对外差信号不能等间隔采样的问题,提出一种新的非均匀采样信号的离散傅里叶变换(DFT)方法。首先,给出距离速度同步测量多普勒激光雷达系统模型,指出对外差信号不能等间隔采样的原因;然后,通过理论推导,提出一种新的非均匀采样信号的频谱分析方法;最后,通过仿真验证该方法可用于分析非等间隔采样信号的频谱。结果表明,在道路运动目标产生的多普勒频率范围内,接收信号信噪比(SNR)为0 d B的情况下,该方法仍可有效分析出不等间隔采样多普勒信号的频率。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61575205 and 62175022)Sichuan Natural Science Foundation(2022NSFSC0803)Sichuan Science and Technology Program(2021JDRC0035).
文摘The nonuniform distribution of interference spectrum in wavenumber k-space is a key issue to limit the imaging quality of Fourier-domain optical coherence tomography(FD-OCT).At present,the reconstruction quality at different depths among a variety of processing methods in k-space is still uncertain.Using simulated and experimental interference spectra at different depths,the effects of common six processing methods including uniform resampling(linear interpolation(LI),cubic spline interpolation(CSI),time-domain interpolation(TDI),and K-B window convolution)and nonuniform sampling direct-reconstruction(Lomb periodogram(LP)and nonuniform discrete Fourier transform(NDFT))on the reconstruction quality of FD-OCT were quantitatively analyzed and compared in this work.The results obtained by using simulated and experimental data were coincident.From the experimental results,the averaged peak intensity,axial resolution,and signal-to-noise ratio(SNR)of NDFT at depth from 0.5 to 3.0mm were improved by about 1.9 dB,1.4 times,and 11.8 dB,respectively,compared to the averaged indices of all the uniform resampling methods at all depths.Similarly,the improvements of the above three indices of LP were 2.0 dB,1.4 times,and 11.7 dB,respectively.The analysis method and the results obtained in this work are helpful to select an appropriate processing method in k-space,so as to improve the imaging quality of FD-OCT.
基金supported in part by the National Natural Foundation of China(NSFC)(Nos.62027801 and U1833203)the Beijing Natural Science Foundation(No.L191004).
文摘Sampling is a bridge between continuous-time and discrete-time signals,which is import-ant to digital signal processing.The fractional Fourier transform(FrFT)that serves as a generaliz-ation of the FT can characterize signals in multiple fractional Fourier domains,and therefore can provide new perspectives for signal sampling and reconstruction.In this paper,we review recent de-velopments of the sampling theorem associated with the FrFT,including signal reconstruction and fractional spectral analysis of uniform sampling,nonuniform samplings due to various factors,and sub-Nyquist sampling,where bandlimited signals in the fractional Fourier domain are mainly taken into consideration.Moreover,we provide several future research topics of the sampling theorem as-sociated with the FrFT.
文摘本文将先进的DASP(Data Alias-free Signal Processing)抗混叠信号采样技术运用到现代测试仪器平台中。通过恰当地选取采样点位置和改进信号处理算法,解决了信号采样中以较少点重构高频信号的问题,该技术抗混叠和消除混叠频谱噪声的特点允许它能准确检测到各个不同幅度的信号。研究表明DASP技术融入测试平台能以较低的采样率有效地提取高频信号,提高了测试精度和效率。
文摘针对伪随机(PN)码调制的多普勒激光雷达中固有的对外差信号不能等间隔采样的问题,提出一种新的非均匀采样信号的离散傅里叶变换(DFT)方法。首先,给出距离速度同步测量多普勒激光雷达系统模型,指出对外差信号不能等间隔采样的原因;然后,通过理论推导,提出一种新的非均匀采样信号的频谱分析方法;最后,通过仿真验证该方法可用于分析非等间隔采样信号的频谱。结果表明,在道路运动目标产生的多普勒频率范围内,接收信号信噪比(SNR)为0 d B的情况下,该方法仍可有效分析出不等间隔采样多普勒信号的频率。
