菲涅耳透镜同时具有分光与会聚特性, 且体积小、重量轻和易复制, 使其在光谱检测中得到逐步应用, 但典型光谱成像仪采用菲涅耳透镜沿光轴扫描的方法来获得连续谱线, 不利于光谱仪的稳定性。考虑到气体探测需求, 选用多通道方式来获得多光谱, 提出了一种基于菲涅耳透镜阵列的新型红外气体传感器, 可实现吸收波长在3～5 μm的CO2,CO,CH4,SO2气体的实时检测。利用球面波的传输理论和瑞利判据, 推导了菲涅耳透镜光谱分辨率与透镜结构参数之间的函数关系, 并以光谱分辨率小于50nm为性能指标, 对1μm工艺的8台阶菲涅耳透镜阵列的结构参数进行了计算和误差分析。结果表明, 透镜阵列所需焦距为47.84 mm, 平均数值孔径大于0.4。

Fresnel lens can realize both focus and dispersion of light and it also has the virtues including small volume, light weight and reproducibility, which makes it be widely used in spectral inspection. Typical spectral imaging instrument with Fresnel lens obtains continuous spectral lines by moving Fresnel lens along optical axis and therefore it will greatly decrease the stability of the whole instrument. Considering the requirement of gas detection, multi-channel mode was adopted to obtain multi-spectral and a novel infrared gas sensor based on a Fresnel lens array was presented. The gas sensor can real-time check and inspect of CO2, CO, CH4 and SO2 gases, whose adsorption wavelengths are all within from 3 μm to 5 μm infrared waveband. The relationship of spectrum resolution of Fresnel lens with structure parameters of lens was deduced by use of transmission theory of spherical wave and Rayleigh criterion. Moreover, structure parameters and their fabrication errors for 1 μm fabricated and eight phased Fresnel lens array were calculated when spectral resolution is required to be less than 50 nm. The calculated results show that the focal length of lens array is required to be 47.84 mm and the average numerical aperture can be more than 0.4.