The optical detector of formaldehyde designed for sensing cancer biomarkers in air exhaled from human lungs with possible application in free atmosphere is described. The measurements were performed at wavelengths ranging from 3595.77–3596.20 nm. It was stated that at the pressure of 0.01 atm this absorption band exhibits the best immunity to typical interferents that might occur at high concentration in human breath. Multipass absorption spectroscopy was also applied. The method of optical fringes quenching by wavelength modulation and signal averaging over the interferences period was presented. The application of such approaches enabled the detection limit of about single ppb to be achieved.

中文翻译：

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光学检测3.6 µm范围内的空气中的甲醛

描述了甲醛的光学检测器，该检测器设计用于感测从人肺呼出的空气中的癌症生物标志物，并可能在自由大气中应用。在波长3595.77–3596.20 nm范围内执行测量。据指出，在0.01 atm的压力下，该吸收带对可能在人的呼吸中高浓度出现的典型干扰物表现出最佳的免疫力。多通吸收光谱法也被应用。提出了在干涉周期内通过波长调制和信号平均来淬灭光学条纹的方法。这种方法的应用使得可以实现大约单个ppb的检测限。