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基于复色共焦法的透明材料厚度检测系统研究
Research on the Measurement System of Transparent Material’s Thickness Based on Polychromatic Confocal Technology
【作者】 张宁;
【导师】 徐熙平;
【作者基本信息】 长春理工大学 , 仪器科学与技术, 2012, 博士
【摘要】 近几年来,随着光学加工、光纤、医药行业的快速发展,透明材料制品如玻璃管、玻璃容器的需求量迅速增长,由于国内企业生产工艺与设备相对落后,其质量与发达国家同类产品相比差距较大,严重影响高端产品生产。透明材料制品特别是精密小型容器对壁厚等参数的精度要求较高,在生产过程中对测量速度的要求也很高,同时这些产品在生产过程中具有高温、红热、脆性大和不易采用接触法检测的特点,因此必须研究非接触在线检测技术实现各参数的测量。采用光电非接触检测技术可以解决透明材料生产质量检测问题,对保证产品的质量、提高产品的国际竞争力有重要意义。复色共焦技术具有多表面层析的特点,以其高质量的尺寸测量性能成为当前光学、光电检测领域最新的研究内容之一。本论文是针对平板玻璃生产、光学零件加工等透明材料相关行业对厚度检测的需求而开展的研究,采用特殊光学系统、高速数据采集技术、先进光谱分析及处理技术,解决透明材料厚度高精度检测的问题。其主要依据光学系统对不同波长光谱产生轴向色散的特性,将连续光谱的轴向色散回波信号由探测器接收,通过上下两个表面返回的波长数据来实现透明材料厚度的检测,该方法克服了以往测量方法只能得到相对结果的现象,可实现透明材料厚度的绝对测量。本文主要研究内容包括四个方面,首先研究复色共焦测量原理,基于复色照明光束,利用光束聚焦的轴向色散特性,分析复色光谱共焦面所产生信号的特点,推导连续光谱中波长信号与透明材料厚度的尺寸模型;然后进行共焦光学系统设计,利用光学设计理论,研究轴向色散光学系统光学参数之间的关系,从理论上对光学系统进行优化;接着研究光谱信号采集原理,在此基础上设计基于CCD的光谱信号采集系统;采集的光谱信号转换成数字信号后经接口电路由采集卡传送给上位机,上位机采用虚拟仪器LabVIEW实现光谱分析软件的设计,将上下表面对应的峰值波长找出来后代入数学模型换算成厚度值;最后采用复色共焦光学系统,结合光纤传输与分光系统以及光谱信号采集系统与分析系统构建原理实验样机装置。根据实验结果,形成完备的透明材料共焦测量原理方案。本文所提出的复色共焦厚度检测方法,通过引入复色照明光束,利用光束聚焦的轴向色散特性,使测量范围扩展到20mm,测量精度达到±0.005mm,配合先进的电子学系统,使测量速度提高至2000次/秒。使用实验样机所测得的一系列数据表明,使用复色共焦法进行较大范围透明材料厚度的高速、高精度在线检测完全可行,具有一定的现实意义和较好的实用价值。
【Abstract】 In recent years, with the rapid development of optical fabrication, optical fiber and Pharmaceuticals industry, the demand for transparent materials productions such as small glass tube and glass container increases rapidly. Because of the productive technology and equipments lags in domestic companies, the qualities of their products are worse than the similar products of developed countries. It is deeply affecting the high-end product. The transparent materials productions need high precise parameters of small precise glass containers, especially the containers’wall thickness and demand for the measure velocity seriously in the producing process. Meanwhile, there are characteristics of hyperthermia, red heat, brittleness and difficult to use contact measurement, so we must research for the non-contact online detecting technology to achieve the parameters’measuring. Using photoelectric can solve the detecting problems of transparent materials productions meanwhile significant to assure the productions’qualities and improve their international competitive abilities.Polychromatic confocal technique has characteristics of multiple surface chromatographic.-Because of the performance of high quality measurement, it is the latest research in the field of photoelectric detection. This thesis researches on the thickness detecting of related products of transparent material such as the plate glass manufacture, optical parts processing and so on. It is to solve the high precision detecting problem of transparent material thickness by utilizing especial optical system, high speed data acquisition technology and advanced analysising and processing technology of optical spectrum. Based on the characteristic that different wavelength optical spectrum produce axial dispersion through optical system, detector accepts axial dispersion echo signal of continous spectrum and then it realizes transparent material thickness detecting by analyzing wavelength data returned from the upper and lower two surfaces. This method overcomes the problem that last method could only get the relative result so that the absolute measurement can be realized. The main contents of study include four aspects. Firstly, it researches the theory of polychromatic confocal. Analyzing the signal characteristics of polychromatic confocal surface and then the wavelength signals and the dimension model of thickness for transparent material in the continuous spectrum are derived, which base on the polychromatic illumination beam and make use of the dispersion characteristic on asis. After that, the confocal’optical system is designed to research the relationship of optical parameters in axial dispersion optical system. The design of optical system is optimized theoretically. Then, we research spectral signal differential acquisiting processing principle and design the spectral signal acquisition system based on CCD according to it. The acquisited spectrum signal is converted digital signal and then delivered from acquisiting card to PC by interface circuit. At last, LabVIEW was used to analysis spectrum and construct software system, and after the wavelength peak value correspounding the upper and lower surfaces being found, it is converted to thickness with math model. At last, The principle prototype of transparent material confocal measurement is constructed by polychromatic confocal optical system combination with optical fiber transmission, optical splitting system and acquisiting and analyzing system of spectrum signal. According to experimental result, the principle scheme of the measurement system is put forward completely.Polychromatic confocal measurement method, utilizing axial dispersion characteristic of focusing light beam by bringing in polychromatic light beam, extend the range to20mm with absolute distinguishability. Confocal transparent material thickness’ measurement method, based on polychromatic lighting, can make distinguishability at±0.005mm. In conclusion, using polychromatic measurement method proposed by this paper to measure extensiveness and successive thickness-changing transparent material at a high speed and high precision online is feasible and meaningful actually and has better practical value.
【Key words】 polychromatic confocal technology; transparent material; thickness measurement; linearCCD; spectral analysis;