中文摘要：

为了使光谱仪在分辨率基本不变的同时增宽工作光谱范围,利用非成像原理设计了自由曲面透镜,将光源发出的宽工作谱段的光束准直为两束波长不同、方向不同的平行光,实现探测器上光谱的折叠分布.首先,根据两束入射光线经自由曲面折射前、后的矢量关系,建立自由曲面上点坐标的一阶偏微分方程组;然后,采用Runge-Kutta法对偏微分方程组进行数值差分求解,得到自由曲面离散采样点,进而构建得到自由曲面透镜,将自有曲面透镜导入ZEMAX软件中对光源的双光束准直进行模拟,在Tracepro软件中进行光线追迹分析其照度分布;最后,将自由曲面透镜应用于近红外光谱仪中,将波段为800~2 400 nm的光源准直为两束波长分别为800~1 600 nm和1600~2 400 nm的方向不同的平行光束,经单个光栅色散后由成像透镜组成像在探测器表面,形成两组相互平行且首尾相连的折叠光谱,光谱仪的分辨率优于10 nm.结果表明,采用该自由曲面透镜可以同时实现光谱仪的高分辨率和宽工作光谱范围,且使光谱仪的结构更加紧凑.

英文摘要：

To extend the working spectral range of spectrometer while keeping the resolution the same,a freeform lens was designed based on non-imaging principle,which could collimate the broadband source light into two beams with different wavelengths in different direction,to achieve the spectrum-fold on a two demention array detector.First of all,a first-order partial differential equations set was obtained according to the vector relationship between the incident rays and the refractive rays on the freeform surface.Then Runge-Kutta methods was adopted to get the numerical solution of the partial differential equations which are the discrete points of the freeform surface,and the freeform lens was constructed.The two beam collimating of the source was simulated in ZEMAX software,and the irradiance maps of the two collimated beams were simulated in Tracepro software.Finally,the freeform lens was appllied to a spectrometer to collimate a source with wavelength ranging from 800 nm to 2 400 no into two beams with wavelength from 800 nm to 1 600 nm and from 1 600 nm to 2 400 nm in different direction.After being dispersed by one grating and focused by imaging lens,two paralle and end to end spectra were distributed in the detector,and the spectral resolution was better than lOnm.The simulation results show that,by using this kind of freeform lens,both high resolution and wide working wavelength range can be achieved in one spectrometer,and the structure of the spectrometer becomes much more compact.