光谱学与光谱分析, 2014, 34 (4): 977, 网络出版: 2014-04-09   

基于微机电系统红外光源的长光程气体检测

Long Optical Path Gas Detection Based on MEMS Infrared Light Source
杜彬彬 1,2,*张鹏 1,2高文宏 1,2石云波 1,2朱林泉 1,2
作者单位
1 中北大学电子测试技术国家重点实验室, 山西 太原 030051
2 中北大学仪器与动态测试重点实验室, 山西 太原 030051
摘要
针对红外气体传感器对光源的要求, 选用了一种宽波长、 高调制频率、 低功耗的小体积微机电系统(micro-electro-mechanic system, MEMS)红外光源作为辐射源, 其各项性能均能很好的满足红外传感系统对于光源的要求。 由于其面光源的朗伯辐射特性, 整形之后的红外光数值孔径仍然很大, 采用传统的长光程气室结构很难实现长光程从而提高系统的检测灵敏度。 本文结合双波长单光路的差分检测方法, 设计了一种基于积分球特性的吸收气室, 有效地解决了MEMS红外光源在高灵敏度气体检测应用中难于实现长光程的问题; 并运用光在传输过程中光通量守恒的原理, 推导了此积分球吸收气室的等效光程, 解决了积分球气室等效光程计算的难题; 同时采用FPGA主控芯片对MEMS红外光源进行高频调制并处理探测器的输出信号, 使得外围电路的设计更加简单、 灵活。 设计中, 使用直径为5 cm的积分球吸收气室便可实现166.7 cm的等效光程, 研究结果显示系统可测得的最小甲烷浓度达0.001×10-6, 极大地提高了红外检测系统的灵敏度。
Abstract
According to the requirements of infrared gas sensor for the light source, a broad wavelength, high modulation frequency, low power consumption and small size MEMS infrared light source is chosen as the radiation source, whose performance meets the requirements of infrared sensing system for the light source greatly. However, the infrared light source with the lamberation radiation characteristics is a surface light source, which is still with a large numerical aperture after shaping. It is difficult to increase the detection sensitivity by using a traditional long optical gas cell in a MEMS infrared light source detection system. Based on the dual-wavelength single beam differential detection method, an integrating sphere as the gas cell for long optical path is designed, which is able to realize long optical path for high sensitivity gas detection. The physical dimension is deduced for the equivalent optical path according to the flux conservation principle in the process of light transmission, solving the calculation problem of equivalent optical path of the integrating sphere cell. Using FPGA control chip, the MEMS infrared light source is droved at high frequency modulation and the detector output signal is processed, which makes the external circuit design much simple and flexible. It turns out that 166.7 cm equivalent optical path and the minimum concentration of methane of 0.001×10-6 are achieved by the use of a 5 cm diameter integrating sphere in the research, improving the sensitivity of infrared detection system greatly.

杜彬彬, 张鹏, 高文宏, 石云波, 朱林泉. 基于微机电系统红外光源的长光程气体检测[J]. 光谱学与光谱分析, 2014, 34(4): 977. DU Bin-bin, ZHANG Peng, GAO Wen-hong, SHI Yun-bo, ZHU Lin-quan. Long Optical Path Gas Detection Based on MEMS Infrared Light Source[J]. Spectroscopy and Spectral Analysis, 2014, 34(4): 977.

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