线光在反射表面形貌测量中的关键技术研究

发布时间：2018-01-14 18:14

本文关键词：线光在反射表面形貌测量中的关键技术研究　出处：《西南科技大学》2016年硕士论文　论文类型：学位论文

【摘要】：表面形貌测量是产品质量控制的关键任务,直接决定产品的外观特征及使用性能。目前测量朗伯表面形貌的技术已日趋成熟,但大多存在逐点测量速度慢、环境要求苛刻、测量范围小、计算量大、具有映射多义性、易出现测量盲区等缺点,难以用于反射表面的形貌测量。针对上述问题,对基于线光测量反射表面形貌的线激光三角法、横向剪切干涉法、同步偏振相移法进行了深入研究,主要研究成果如下:(1)将传统斜射式激光三角法扩展到反射表面形貌测量中,提出了一种高噪声背景下激光条纹亚像素中心提取的方法。线光投射至反射表面,被表面形貌调制并变形,变形光场被屏幕和CCD相机接收后形成激光条纹图像。采用高噪声背景下条纹亚像素中心提取的方法,计算出激光条纹与参考平面条纹的中心偏移量,根据光源、被测表面、设备的三角几何关系,解调出变形光场蕴含的表面形貌信息。实验表明,条纹中心提取的好坏直接影响表面形貌测量的精度,线激光三角法测量反射表面形貌的误差约为±0.25mm。(2)针对线激光三角法测量误差大的问题,对María Frade等的横向剪切干涉三维形貌仪进行改进,设计了不包含柱面镜和透镜、仅包含透镜的两种反射表面形貌测量方案,消除柱面镜和透镜联合使用引起的象散现象。利用Savart双折射晶体横向剪切展开线光,获得干涉条纹图像,采用傅里叶变换解析频率,计算被测表面与设备传感器之间的距离,仅需一帧图像就可测量表面上一条轮廓线的形貌。实验表明,剪切干涉的自比较和共路共线特性增强了反射表面形貌测量的抗环境振动和干扰能力,测量精度优于30μm。(3)利用同步偏振相移技术,解决了傅里叶变换解析图像时测量精度受干涉信号离散、参数选取等因素限制的问题。在横向剪切干涉反射表面形貌测量中,于Savart晶体后加入由1/4波片和偏振片组成的偏振移相装置,用空间位置不同的CCD相机同时采集剪切干涉条纹图像,经四步相移和相位解包裹获得相位斜率后,测量出反射表面的形貌。实验表明,由于剪切干涉抗环境干扰、相移抵消噪声及同步采集消除分时误差等优点,最终测量精度优于20μm,测量出的形貌结果及其变化趋势更接近真实值。
[Abstract]:Surface topography measurement is a key task of product quality control, which directly determines the appearance and performance of products. At present, Lambert surface morphology measurement technology has become more and more mature, but most of them have slow measurement speed point by point. The environmental requirements are harsh, the measurement range is small, the calculation is large, has the mapping polysemy, easy to appear the measurement blind area and so on the shortcoming, is difficult to use in the reflection surface topography measurement. The linear laser triangulation method, transverse shearing interferometry and synchronous polarization phase shift method based on linear light measurement of reflected surface morphology are studied in detail. The main research results are as follows: (1) the traditional oblique laser triangulation method is extended to the measurement of reflected surface topography. In this paper, a method of subpixel center extraction of laser stripes in high noise background is proposed. The line light is projected onto the reflected surface, which is modulated and deformed by the surface morphology. The distorted light field is received by the screen and CCD camera to form the laser stripe image. The center offset between the laser stripe and the reference plane fringe is calculated by using the method of extracting the sub-pixel center of the stripe in the high noise background. According to the triangular geometry of the light source, the measured surface and the equipment, the surface topography information contained in the deformed light field is solved. The experiment shows that the precision of the surface topography measurement is directly affected by the extraction of the fringe center. The error of line laser triangulation is about 卤0.25mm. 2) aiming at the problem that the measurement error of linear laser triangulation is large. In this paper, the transverse shear interferometer of Mar 铆 a Frade is improved, and two measuring schemes of reflecting surface topography without cylindrical mirror and lens are designed. In order to eliminate the astigmatism caused by the combined use of cylindrical mirror and lens, the interference fringe image is obtained by using the Savart birefringent crystal transverse shear to expand the line light, and the frequency is analyzed by Fourier transform. In order to calculate the distance between the measured surface and the device sensor, the profile of a contour line on the surface can be measured by only one frame of image. The self-comparison and collinear characteristics of shearing interferometry enhance the environmental vibration and interference resistance of the reflected surface topography measurement, and the measurement accuracy is better than 30 渭 m 路m3) by using synchronous polarization phase shift technique. It solves the problem that the measurement accuracy is limited by the interference signal discreteness and parameter selection when the Fourier transform is used to analyze the image. A polarization phase shifting device composed of 1/4 wave plates and polarizers is added to the Savart crystal, and the shearing interference fringe images are simultaneously collected by the CCD camera with different spatial positions. After the phase slope was obtained by four-step phase shift and phase unwrapping, the morphology of the reflected surface was measured. The experimental results show that the phase shift cancels the noise and the synchronous acquisition eliminates the time-sharing error due to the anti-environmental interference of the shearing interference. The final measurement accuracy is better than 20 渭 m, and the morphologies and their changing trends are closer to the true values.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TP391.41

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