摘要
现有的光谱共焦色散物镜存在测量量程小的问题,在工业检测中的应用受到较大的限制。针对这一问题,采用四片球面透镜设计了一种大量程的色散物镜,在500~700 nm波段内,测量量程达到9.962 mm。在大色差的情况下对球差进行了优化,并利用设计的色散物镜搭建了光谱共焦位移测量系统,开展了性能评估实验。实验结果表明,系统实现了10 mm的测量范围,测量标准差为0.5μm,平均绝对误差为0.6μm。另外,对不同材料的样品进行了测量,结果表明,系统对不同材料样品具有一定的适应性。该设计实现了较大的测量范围,可以满足各类复杂对象的工业检测需求。
Objective The development of precision manufacturing puts forward higher requirements for surface flaw detection technology in industrial testing.Because precision devices are easy to scratch,the contact measurement technology based on mechanical probe is no longer suitable for the detection needs of such devices,while the non-contact measurement technology based on optical method begins to highlight its advantages.At present,the commonly used high-precision displacement sensor includes the laser triangle ranging sensor.It has the advantages of simple structure and convenient operation,but the measurement accuracy is influenced by the size and shape of the light spot,environmental light and other factors.Besides,the laser triangle ranging sensor depends on its sample surface scattering light,so it is not suitable for the measurement of high reflection and inclined surface.The chromatic confocal technology has the advantages of high resolution and insensitivity to surface texture,tilt,stray light and other factors,so it is more suitable for the detection needs of precision devices.In order to meet the requirement of a large measurement range in industrial testing,we design a large-range dispersion objective lens.In order to reduce the cost,a traditional spherical lens is adopted.We design a four-piece objective lens and optimize the aberration using the Zemax software.A chromatic confocal displacement measurement system is built with the designed dispersive objective lens.Experiments are designed and carried out to evaluate the displacement measurement error of the system and the measurement performance on different material samples.The results show that the system has certain adaptability to different material samples.Methods A dispersion objective lens is designed by using the traditional spherical lens.According to the linear dispersion condition,we choose suitable materials,compute the initial structure of the objective lens,and then use the Zemax software to optimize the spherical aberration,dispersion range,and light spot size.In the process of optimization,the weight of the large dispersion is increased,and the demand for dispersion linearity is reduced.At the same time,the small spot size and spherical aberration are ensured,and finally the structure of the dispersion objective lens with large axial chromatic aberration is obtained.Using the designed dispersion objective lens,the chromatic confocal displacement measuring system is established.A spectral characteristic normalizing method is designed to eliminate the undesired effects on the spectral signals,resulting from the optical fiber attenuation characteristics,light source spectral distribution characteristics and spectrometer detector responsivity.The evaluation experiment is designed and carried out to figure out the displacement measurement error of the system.In addition,the displacement measurement experiment of different materials commonly used in industrial application is carried out,and the results show that the system has certain adaptability to the measurement of different materials.Results and Discussions Most of the existing studies on the design of chromatic confocal objective lens based on traditional spherical lens have a small measurement range and are greatly limited in the industrial testing.The dispersion objective lens designed in this study has an axial chromatic aberration of nearly 10 mm in the working band,and the spherical aberration of monochromatic wave is well corrected(Fig.5).The chromatic confocal displacement measurement system built with this objective lens can obtain a measurement range of 10 mm,which can better meet the demand for industrial detection with large range(Fig.9).Aiming at the problem that the spectral signal in the system is subjected to extra modulation,a normalized processing method of spectral characteristics is designed(Fig.2),which reduces the adverse effects of the spectral distribution characteristics of light source,the attenuation characteristics of fiber and the response characteristics of spectrometer detector on the spectral signal received by the system and obtains the spectral signal with good characteristic peak(Fig.8).The experimental results show that the system has good adaptability to different material samples(Table 3).Conclusions In this study,according to the basic principle of chromatic confocal displacement sensor and linear dispersion condition,the initial structure of the dispersion objective lens is designed.The light spot size at each wavelength and the monochromatic spherical aberration of the initial structure are optimized by using the Zemax software,and the axial chromatic aberration is controlled at the same time.Finally,a dispersion objective lens with an axial chromatic aberration of 9.962 mm in the 500-700 nm band is designed.A chromatic confocal displacement measurement system is designed by using the dispersion of the objective.In order to eliminate the effects of fiber attenuation characteristics,spectral distribution characteristics of the light source,and the spectrometer detector responsivity,the spectral characteristic normalizing processing method is designed and then the relationship between the peak wavelength and the position is obtained.The built displacement measurement system obtains the 10 mm measuring range,and the standard deviation of measurement is 0.5μm and the mean absolute error of measurement is 0.6μm.In addition,different material samples are measured,and the results show that the system has certain adaptability to different material samples.Compared with the laser triangle ranging sensor,the system is more suitable for high reflection samples.
作者
邵谭彬
郭文平
席英皓
刘子聿
杨克成
夏珉
Shao Tanbin;Guo Wenping;Xi Yinghao;Liu Ziyu;Yang Kecheng;Xia Min(School of Optical and Electronic Infororation,Huazhong University of Science and Technology,Wuhan 430074,Hubei,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2022年第18期56-63,共8页
Chinese Journal of Lasers
关键词
测量
无损检测
位移传感器
光谱共焦
色散
measurement
nondestructive inspection
displacement sensor
chromatic confocal
dispersion
作者简介
通信作者:郭文平,wpguo@hust.edu.cn。
