Each unit houses a near-infrared (NIR) LED and monochrome CCD camera sensor, so as the red pigment in blood (hemoglobin) absorbs NIR light, veins appear as dark lines on the resulting image.
手指静脉识别仪包括近红外线LED灯和黑白相机传感器。 近红外LED灯发出近红外射线，当近红外射线穿透手指时，手指静脉的血红蛋白将吸收近红外光，因此，图像中静脉将变为黑色。
With NIR spectra, the analytical information is contained in small spectral variations and usually dominated by the features such as light scattering, background noise and baseline drift.
近红外光谱不但包含着物质成分信息，而且这些信息完全掩盖在众多复杂背景当中（包括光散射、背景噪声以及背景漂移）。
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