SignificanceImaging photoplethysmography (iPPG) is a non-contact measuring technology for several physiological parameters reflecting personal health status without a special sensor. However, the pulse signal obtained using the iPPG usually is contaminated by various noises, and the intensity of the interesting pulse signal is relatively weak compared to the noises, emphasizing the necessity of obtaining high-quality pulse signals to measure physiological parameters correctly.AimVarious regions of the face harbor distinct pulse information. We propose a spatial averaging method based on adaptive weights, which can obtain high-quality pulse signals by applying different weights to facial sub-regions of interest (sub-ROIs; sROIs).ApproachFirst, the facial ROI is divided into seven sROIs and the coarse heart rate (HR) is calculated from them. Next, the signal-to-noise ratio (SNR) of the raw signal obtained from each sROI is calculated using the coarse HR, and then a high-quality pulse signal is obtained by assigning positive or negative weights to each sROI based on the SNRs.ResultsWe compare our method with others through the quality analysis of the obtained pulse signals using the self-collected database and the public database PURE. The comparison results show that the proposed method can provide a better pulse signal compared to other methods under various resolutions and states.ConclusionsThis proposed method can obtain the pulse signal with better quality, which is helpful to accurately measure physiological parameters, such as HR and HR variability.
In this article, we innovatively use Pearson correlation coefficient, etc. to analyze the components of the snowy image (the
snow-free image and the mask image), and then create an effective and accurate snow-free model using the relationship
between the components of the snowy image. For the snow-free model, we innovatively consider the similarity in the
generation of the snow-free image and the mask image; we also consider this relationship in our neural network framework.
We set the generator model in the generative adversarial network as the pseudo-siamese network with the same structure
but the different parameters. Each branch of the pseudo-siamese network adopts the autoencoder and the multi-scale
perception structure. The former can guarantee the acquisition of high-resolution images, and the latter can perceive context
information at different scales. We restore the mask image first and then restore the snow-free image because the mask
image has a simpler background than the snow-free image and the mask image is easier to recover than the snow-free
image. The results show that our (PS-GAN) pseudo-siamese generative adversarial network not only has better
performance on the data set, but also has good results in the real world which greatly improves the effect of using the
yolov5 to detect.
Significance: The measurement of human vital signs based on photoplethysmography imaging (PPGI) can be severely affected by the interference of various factors in the measurement process; therefore, a lot of complex signal processing techniques are used to remove the influence of the interference.
Aim: We comprehensively analyze several methods for color channel combination in the color spaces currently used in PPGI and determine the combination method that can improve the quality of the pulse signal, which results in a modified plane-orthogonal-to-skin based method (POS).
Approach: Based on the analysis of the previous studies, 13 methods for color channel combination in the different color spaces, which can be seen as having potential abilities in measuring vital signs, were compared by employing the average value of signal-to-noise ratio (SNR) and the box-plot in the public databases UBFC-RPPG and PURE. In addition, the pulse signal was extracted through the dual-color space transformation (sRGB → intensity normalized RGB → YCbCr) and fine-tuning on the CbCr plane.
Results: Among the 13 methods for color channel combination, the signal extracted by the Cb+Cr combination in the YCbCr color space includes the most pulse information. Furthermore, the average SNR of the modified POS for all the used databases is improved by 69.3% compared to POS.
Conclusions: The methods using prior knowledge are not only simple to calculate but can significantly increase the SNR, which will provide a great help in the practical use of vital sign measurements based on PPGI.
The polarized light properties of stimulated Raman scattering (SRS) in elliptical core
optical fiber is systematically studied. In experiments, eight- order Stokes lines and two- order
anti-Stokes spectra are observed and some parameters are analyzed such as the polarization,
Raman frequency shift of each-order Stokes spectra under different polarization state of pump
light, and the experiential formula are also provided. The results are in good agreement with the
experimental figures. Experiments indicate that each-order Stokes spectra polarization state of
stimulated Raman scattering in the birefringence optical fiber is related not only with Raman
medium but also with pump light polarization state. The influence of pump light polarization state
on low-order Stokes frequency-shift is lower but higher on the high-order Raman Stokes
frequency shift fluctuation.
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