纹影法是进行流场测量的重要手段之一。在高速纹影法测量过程中,照明的质量将对测量结果产生重要影响。为了获得照度分布均匀、光能利用率高、价格便宜、控制方便的照明系统,提出了发光二极管(LED)照明方式。对纹影系统的结构及光学扩展量进行了分析,并结合成像设备计算出实际测量面所需光通量。根据光通量的要求,对LED进行选型、布局,并设计采用开普勒式望远镜结构进行准直。针对工程中常用的反射式纹影仪,利用Tracepro建立光学模型,并计算出纹影仪测量面的照度分布及光通量。计算结果表明,采用LED照明系统可以很好地满足纹影仪照明要求。

Schlieren device is an important method for the measurement of transient flow field. The illumination effect serves as a vital role for its measuring result. A lighting system based on light emitting diode (LED) was designed to solve the problem of schlieren′s illumination. The structure and etendue of schlieren device was analyzed,and the light flux of the object plane was calculated. According to the calculated result,the type of LED was selected,the layout and the optical collimating system were designed. The model of the lighting system was built through Tracepro,the illuminance distribution and light flux were analyzed. The calculated result indicated the lighting system based on LED met the challenge of schlieren device.