Concentrating solar power plants use mirrors to redirect solar radiation toward receivers. Mirrors (facets) are suitably shaped to optimize the radiation capture ratio. Because deviations from ideal shape/slope degrade optical efficiency, the availability of reliable instruments for 3D shape measurement is essential. This paper deals with an innovative instrument, named VISproLF, specific for the case of facets for the primary reflector of linear Fresnel collectors. The instrument is simply composed of a LCD screen and a digital camera; to avoid artifacts, the camera must be equipped with a high quality lens and its characteristic matrix and distortion coefficients have to be accurately evaluated. The arrangement of the LCD screen and camera around the facet must follow the simple rule to view from the camera the facet surface entirely covered by the image of the screen. Then, the position and attitude of the camera (first) and LCD screen (second) are accurately evaluated by a simple procedure based on the pinhole camera model, which makes the instrument self-calibrating. The shape and slope of the facet surfaces are obtained by processing five binary images by means of a completely digital method of which a detailed description is given. In the experimental arrangement used to prepare the present paper, the slope accuracy is about 0.2 mrad. With respect to the most common instruments based on the Fringe reflection technology, VISproLF offers two great advantages: full-digital image processing and a self-calibration feature.

中文翻译：

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VISproLF：用于测量线性菲涅耳面的 3D 形状的自校准仪器

聚光太阳能发电厂使用镜子将太阳辐射重定向到接收器。反射镜（小平面）的形状经过适当调整以优化辐射捕获率。由于与理想形状/斜率的偏差会降低光学效率，因此用于 3D 形状测量的可靠仪器的可用性至关重要。本文介绍了一种名为 VISproLF 的创新仪器，专门用于线性菲涅耳收集器的主反射器的刻面情况。仪器由液晶屏和数码相机简单组成；为了避免伪影，相机必须配备高质量的镜头，并且必须准确评估其特征矩阵和失真系数。LCD 屏幕和摄像头在刻面周围的布置必须遵循简单规则，以便从摄像头观察刻面表面完全被屏幕图像覆盖。然后，基于针孔相机模型，通过简单的程序准确评估相机（第一）和液晶屏（第二）的位置和姿态，使仪器自校准。刻面的形状和斜度是通过完全数字化的方法对五幅二值图像进行处理得到的，对此进行了详细说明。在用于准备本文的实验装置中，斜率精度约为 0.2 mrad。相对于基于边缘反射技术的最常见仪器，VISproLF 具有两大优势：全数字图像处理和自校准功能。