针对传统光谱测油仪存在的环境适应能力弱、 分析速度慢、 测量重复性差等问题, 研制了一种便携式中红外水中油浓度速测仪。 其核心光路采用典型的非对称折叠式M型Czerny-Turner光学结构, 有效缩小仪器体积; 使用周期性转动的斩光器调制红外光源, 并对斩光器转速进行数字PID控制, 调制精度达到±0.5%; 采用固定光栅作为分光元件, 无需光栅扫描装置且不存在转动误差; 利用新型MEMS红外线传感器阵列探测调制后的光谱信号, 显著提高光谱采集速度。 光学仿真及实验结果表明仪器光谱范围为2 800～3 200 cm-1, 光谱分辨率达到6 cm-1（＠3 130 cm-1), 信噪比达到5 200∶1, 谱图采集速度为13 ms·幅-1, 吸光度标准偏差优于3×10-3, 满足了水中油测定国家标准要求。 与已有红外光谱测油仪相比, 该仪器小型便携, 分析速度快, 测量精度高, 抗震防潮性能好, 特别适用于环境监测部门对水中油浓度的现场实时测量, 因此在水质监测领域具有广阔的应用前景。

Aiming at the existing problems such as weak environmental adaptability, low analytic efficiency and poor measuring repeatability in the traditional spectral oil analyzers, the present paper designed a portable mid-infrared rapid analyzer for oil concentration in water. To reduce the volume of the instrument, the non-symmetrical folding M-type Czerny-Turner optical structure was adopted in the core optical path. With a periodically rotating chopper, controlled by digital PID algorithm, applied for infrared light modulation, the modulating accuracy reached ±0.5%. Different from traditional grating-scanning spectrophotometers, this instrument used a fixed grating for light dispersion and avoided rotating error in the course of the measuring procedures. A new-type MEMS infrared linear sensor array was applied for modulated spectral signals detection, which improved the measuring efficiency remarkably. Optical simulation and experimental results indicate that the spectral range is 2 800～3 200 cm-1, the spectral resolution is 6 cm-1 (@3 130 cm-1), and the signal to noise ratio is up to 5 200∶1. The acquisition time is 13 milliseconds per spectrogram, and the standard deviation of absorbance is less than 3×10-3. These performances meet the standards of oil concentration measurements perfectly. Compared with traditional infrared spectral analyzers for oil concentration, the instrument demonstrated in this paper has many advantages such as smaller size, more efficiency, higher precision, and stronger vibration&moisture isolation. In addition, the proposed instrument is especially suitable for the environmental monitoring departments to implement real-time measurements in the field for oil concentration in water, hence it has broad prospects of application in the field of water quality monitoring.