A range-spread target(RST)detector is proposed for wideband radar.The detector,referred to as a conjugate multiplication and block thresholding(CMBT)detector,is simple for implementation in existing radar systems and ...A range-spread target(RST)detector is proposed for wideband radar.The detector,referred to as a conjugate multiplication and block thresholding(CMBT)detector,is simple for implementation in existing radar systems and has the advantage of minor calculation.First,the target energy of adjacent stretched echoes is coherently accumulated via conjugate multiplication and Fourier transform operations.It is noted that conjugate multiplication of two complex Gaussian distributed noise is complex double Gaussian distributed,leading to a signal to noise ratio(SNR)loss.Subsequently,considering the sparsity and clustering characteristics of the conjugate multiplication amplitude spectrum(CMAS),the block thresholding method is adopted for denoising,where the noise and cross-terms are adaptively smoothed,and the signal terms can be basically preserved.Finally,numerical simulation results for both synthetic and real radar data validate the effectiveness of the proposed detector,comparing with the conventional integration detector(ID),the spatial scattering density(SSD)detector,and waveform entropy(WE)and waveform contrast(WC)based detectors.展开更多
针对基于非接触式的心率检测方法受光照变化干扰难以准确估计心率的问题,提出一种抑制光照变化的远程心率估计方法。首先采用YCbCr颜色空间的肤色模型,并建立皮肤掩膜,将该皮肤掩膜与原图像相乘提取面部肤色图,可以从复杂背景中过滤掉...针对基于非接触式的心率检测方法受光照变化干扰难以准确估计心率的问题,提出一种抑制光照变化的远程心率估计方法。首先采用YCbCr颜色空间的肤色模型,并建立皮肤掩膜,将该皮肤掩膜与原图像相乘提取面部肤色图,可以从复杂背景中过滤掉大部分非肤色区域,得到稳定的面部感兴趣区域(region of interest,ROI)肤色图像,减轻面部运动伪影干扰。其次,为抑制光照变化影响,将该区域的RGB颜色空间转换到LAB和YCbCr颜色空间,选取描述血容量变化的G、A、Cr 3种颜色信号,并将这3种颜色信号采用改进的完全自适应噪声集合经验模态分解方法(ICEEMDAN)进行去噪,并使用主成分分析(PCA)分离出与血容量变化相关的脉搏波信号。最后,对该脉搏波信号进行快速傅里叶变换(FFT),根据0.7~3.0 Hz频段内最高峰值所对应的频率来估计心率。实验结果表明:该方法在不同光照条件下正常眨眼时计算出的心率与同时用指夹式脉搏血氧仪测出的心率之间的相关系数为0.9823,Bland-Altman统计上下限分别为3.1788次/min和-1.8805次/min,证实了使用多色彩空间从面部视频进行准确和可靠的心率监测的潜力。展开更多
基金supported by the Joint Fund of Aerospace Science and Engineering(76150-41020014)the Regional Joint Fund for Basic and Applied Basic Research of Guangdong Province(2019B1515120009).
文摘A range-spread target(RST)detector is proposed for wideband radar.The detector,referred to as a conjugate multiplication and block thresholding(CMBT)detector,is simple for implementation in existing radar systems and has the advantage of minor calculation.First,the target energy of adjacent stretched echoes is coherently accumulated via conjugate multiplication and Fourier transform operations.It is noted that conjugate multiplication of two complex Gaussian distributed noise is complex double Gaussian distributed,leading to a signal to noise ratio(SNR)loss.Subsequently,considering the sparsity and clustering characteristics of the conjugate multiplication amplitude spectrum(CMAS),the block thresholding method is adopted for denoising,where the noise and cross-terms are adaptively smoothed,and the signal terms can be basically preserved.Finally,numerical simulation results for both synthetic and real radar data validate the effectiveness of the proposed detector,comparing with the conventional integration detector(ID),the spatial scattering density(SSD)detector,and waveform entropy(WE)and waveform contrast(WC)based detectors.
文摘针对基于非接触式的心率检测方法受光照变化干扰难以准确估计心率的问题,提出一种抑制光照变化的远程心率估计方法。首先采用YCbCr颜色空间的肤色模型,并建立皮肤掩膜,将该皮肤掩膜与原图像相乘提取面部肤色图,可以从复杂背景中过滤掉大部分非肤色区域,得到稳定的面部感兴趣区域(region of interest,ROI)肤色图像,减轻面部运动伪影干扰。其次,为抑制光照变化影响,将该区域的RGB颜色空间转换到LAB和YCbCr颜色空间,选取描述血容量变化的G、A、Cr 3种颜色信号,并将这3种颜色信号采用改进的完全自适应噪声集合经验模态分解方法(ICEEMDAN)进行去噪,并使用主成分分析(PCA)分离出与血容量变化相关的脉搏波信号。最后,对该脉搏波信号进行快速傅里叶变换(FFT),根据0.7~3.0 Hz频段内最高峰值所对应的频率来估计心率。实验结果表明:该方法在不同光照条件下正常眨眼时计算出的心率与同时用指夹式脉搏血氧仪测出的心率之间的相关系数为0.9823,Bland-Altman统计上下限分别为3.1788次/min和-1.8805次/min,证实了使用多色彩空间从面部视频进行准确和可靠的心率监测的潜力。
