近红外光谱技术检测速度快，不破坏样品，可在线分析，是血液无创生化分析能够获得应用的最具潜力的方法之一。但是由于人体血液的吸收光谱信号微弱，而常规光谱仪器在近红外无创生化分析中的光能利用率较低，给无创检测技术应用在临床分析上带来了困难。为了解决此问题，利用椭球反射镜的聚光特性，从几何光学角度出发，分析了椭球镜像点位置分布情况，并采用光线追迹方法优化其初始结构，从而将手指漫反射光高效收集到探测器上。通过仿真分析计算，该椭球反射镜的光能利用率比常规无收集装置的利用率提高了近5倍，增强了仪器检测血液吸收光谱信号的能力，有助于提高仪器信噪比。

Near infrared spectroscopy (NIRS) has advantages such as high speed, no destroying the samples, and online analysis. Therefore, NIRS is one of the most prospective ways to be applied in noninvasive biochemical analysis of blood. However, the absorption spectrum of blood is weak, and in near infrared noninvasive biochemical analysis, light energy utilization efficiency of conventional spectral instruments is lower. Thus, it is a little difficult in clinical noninvasive analysis with NIRS. In order to solve this problem, ellipsoidal reflector is used which has the focusing characteristic. The distributions of image points are analyzed according to geometric optics, and initial structure of ellipsoidal reflector is optimized by the method of ray tracing. In this way, the detector receives diffused light of finger which is collected with high efficiency. Through the simulation, light energy utilization efficiency of this ellipsoidal reflector raises nearly five times than that of non-optical collection device. It is beneficial to test the absorption spectra of blood and improve the signal-to-noise ratio(SNR).