| The development of the aviation industry has put forward higher requirements for aircraft manufacturing. In the aircraft manufacturing process, the cabin materials forming is particularly critical. The cabin is a special transparent surface material. In the traditional process, the transparent surface forming just simply relies on the engineer’s experience to determine. However, the complexity and security of the aircrafts require us to find a more accurate judgment mechanism. To achieve the high precision measurement, this paper presents an optical measurement for the key points of the transparent surface. This system has three modules, a laser, a CCD(Charge Coupled Device) camera and a computer. They are in charge of emission, receiving and processing respectively. Transparent surface is placed in an enclosed space, growing slowly from low to high. The laser beam is injected to the transparent surface, CCD receives it on the other side. After passing through the transparent surface, the laser spot images on the camera. Once we connect the camera with the computer, we can see the image change in real time. When the transparent surface grows, the shape of the spot will change accordingly. We detect the change to monitor the height change of transparent surface.Image processing includes several steps such as median filtering, binarization and ellipse fitting. We put forward a method to record the change, that is, calculating the effective axial length. The performance of the algorithm is given. It can process ten images per second, achieving the desired processing speed requirements. After measuring and analyzing large amount of data, the relationship between the change of effective axial length and the height of transparent surface is drawn. It can help us to control the growth of the transparent surface better by analyzing the trends of the curve. By calculating, we obtain the measurement error is2.754%. The small error ensures the accuracy of measurement. |
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