Research On The Method Of Measuring The Surface Shape Of High Reflection Objects Based On Fringe Reflection Technique

With the rapid development of modern manufacturing industry, the requirements for the size and quality of industrial products are also increasing, especially for mirror and mirror-objects. Highly reflective optical products have played a pivotal role in automobile manufacturing, aerospace technology, defense industry and medical science. High-precision shape measurement can greatly improve the production efficiency of industrial production. Although with high measurement accuracy, the traditional contact measurement method may be time-consuming, and can also damage the surface shape of the object, otherwise, the optical interferometry method is usually with small measurement range. Thus, high-precision, non-contact, large with high-reflection object shape measurement has become a focus of study in the world. In this paper, a high-reflection object shape measurement method based on fringe reflection technique is studied. This method is widely used because of its high precision, non-contact, and a wide measuring range. Based on the fringes of the reflection technique, this paper innovative proposed a method with binary defocus stripes instead of the traditional sinusoidal coding stripes, to solve the defocusing problem of sinusoidal fringe image on the standard plane and high reflection surface and the gamma effect of LCD display. The principle of this method is that using LCD display projection to project binary coding stripes on horizontal and vertical directions, and the strips are projected to the standard plane and highly reflective object, respectively. Then CCD camera receives the distortion stripe modulated by the standard plane and high-reflection surface, and acquires the phase information of the high-reflection surfaces by phase-unwrapping and fringe image demodulation. Through the correspondence between the gradient and the phase, the gradient information of the measured reflector surface can be obtained in the x axis and y axis directions. Finally, the shape measurement of the high-reflection object can be reconstructed with gradient numerical integration methods. This paper mainly studied these contents,1. Studying the measurement principle of high-refection objects based on fringe reflection method, analyzing the correspondence between the phase information and the gradient. And then, acquire the 3D information of the high-refection object with its gradient. Also, built the high-refection object measurement system base on fringe reflection method.2. The measurement system calibration, include the distance d from each pixel on the LCD monitor to the standard planar, and CCD camera calibration, which laid the foundation for the high-accuracy recovery of high-refection objects.3. An improved method with stripe reflection is studied, which uses binary fringe instead of the traditional sinusoidal. Since the CCD camera is focused on the object surface, so the deformed fringe image of high reflective surfaces which captured by CCD camera are blurred. So this paper uses LCD display projection to project binary stripes, through appropriate defocus, easy to get the images with standard sinusoidal fringe and solve the gamma effect of LCD display, as well as the high-accuracy phase information. Finally, the shape reconstruction accuracy is improved.4. Conducting relative measurement experiments for high-refection standard block and concave. Experimental results show that the improved measuring method has improved the measurement accuracy to some extent compared with the traditional method, and laid a solid foundation for industrial production and line testing.