摘要
在曲面光学表面缺陷检测中,光源布局和照明方式对高质量图像的获取至关重要。针对经典环形光源在曲面光学表面缺陷检测照明时存在适应性低和反射光干扰的问题,提出了一种利用调光透镜协同光源结构实现多角度环形均匀照明光源的设计方法。基于Snell定律建立发光二极管与目标面之间的光线映射关系,进一步建立调光透镜表面轮廓母线逐点求解算法,以调控光线的出射角度。按等方位角间隔环形排列配置有调光透镜的单位光源,使其中心对称的单位光源照度叠加互补,通过位移和角度调节机构,最终实现多角度均匀照明。仿真结果表明,调光后光源的发散角控制在±7°之内,当光源工作距离在100 mm至200 mm区间内时,有效照明区域照度均匀度保持在91.94%到93.17%之间,且79.96%的能量集中在有效照明区域;当光源入射角在30°至60°区间内时,有效照明区域照度均匀度稳定在89.50%到91.35%之间。面向曲面光学元件照明结果表明设计环形光源能够实现均匀照明,同时有效减少反射光干扰。通过对配光透镜面形和装调的公差分析,结果表明设计透镜易于加工和装调。
Objective Optical surface defect detection is essential for ensuring the reliability and efficiency of optical systems.Traditional visual inspection methods,however,have become inadequate for modern production demands due to limitations in efficiency and precision.Therefore,automated detection equipment,with machine vision technology at its core,has developed rapidly.Among its components,the illumination source is critical,as an optimized lighting structure and method are key to improving image quality in defect detection.Currently,most defect detection systems use light emitting diode(LED)arrays in an annular configuration.While these light sources can be arranged for multi-angle illumination,their fixed angles limit adaptability to diverse optical element characteristics.In addition,the LED’s large dispersion angle can lead to reflected light interference,particularly problematic in curved surface detection.Therefore,we propose a multi-angle uniform illumination annular light source optimized for detecting defects on curved optical surfaces.Methods In designing an illumination source for detecting defects on curved optical surfaces,achieving uniformity in illumination and controlling the light’s divergence angle are primary considerations.After defining the desired illumination characteristics,an energy mapping relationship between the LED light source and the target surface is established.A planoconvex dimming lens is placed in front of the LED to achieve a narrow divergence angle and uniform illumination.The emitted light undergoes an initial adjustment upon passing through the inner surface of the lens and is further modulated by the outer surface of the lens to precisely focus on the target surface.Based on Snell’s law and energy conservation principles,a point-by-point algorithm for the lens profile bus is developed enabling the construction of a 3D model by fitting and rotating discrete profile points.To meet the requirements for defect detection on optical surfaces,unit light sources with aspheric dimming lenses are arranged in an annular pattern at equal azimuthal intervals,allowing superimposed illumination in centrally symmetric areas.A displacement mechanism enables Z-axis adjustments of the light source,while each unit light source’s incident angle is precisely controlled.This approach achieves multi-angle uniform illumination adaptable to various curved surfaces,effectively reducing reflected light interference and supporting effective dark-field illumination.Results and Discussions After importing the aspherical lens configuration into optical simulation software LightTools,we establish light source parameters and simulation conditions.Simulations verified the illumination effectiveness and the symmetric area superposition approach,confirming that design goals are met(Fig.7).Effective illumination efficiency within the designated area is recorded at 79.96%.In addition,tests at various working distances reveal stable illumination without abrupt changes,with an average uniformity of 92.59%(Table 1).The divergence angle is controlled within±7°(Fig.8).Further analysis of the annular array light source’s performance across planar,concave,and convex surfaces demonstrates uniformity exceeding 90%in all cases(Fig.9 and Fig.11).A comparative analysis with a standard annular light source lacking a dimming lens(Fig.12)shows that the new design significantly reduces reflected light interference.Finally,surface machining and assembly tolerances are analyzed(Fig.13 and Fig.14)by applying periodic error functions to the profile sampling points and adjusting the LED position.The results indicate that illumination distribution remains consistent despite machining and fitting errors.Conclusions By integrating optical dimming lenses with translational and angular adjustment mechanisms,this system achieves multi-angle uniform illumination,offering greater flexibility for inspecting optical elements with varying curvatures.The dimming lens is designed based on the camera’s field of view,narrowing the LED divergence angle to provide uniform illumination over the effective area.The annular light source ensures high uniformity across flat,concave,and convex surfaces through complementary center-symmetric illumination.Adjusting the incident angle within the beam’s effective range enables multi-angle illumination,effectively mitigating the reflective interference common to classical annular sources used on curved optical surfaces.Tolerance analysis shows that with a processing accuracy of 3µm and mounting tolerance of 0.1 mm,the illumination distribution curve remains stable,confirming the design’s ease of processing and assembly.
作者
莫坤
侯溪
邓琥
马梦聪
张帅
李明泽
Mo Kun;Hou Xi;Deng Hu;Ma Mengcong;Zhang Shuai;Li Mingze(School of Information Engineering,Southwest University of Science and Technology,Mianyang 621010,Sichuan,China;Institute of Optics and Electronics,Chinese Academy of Sciences,Chengdu 610209,Sichuan,China)
出处
《光学学报》
北大核心
2025年第2期243-253,共11页
Acta Optica Sinica
关键词
光学设计
缺陷检测
环形光源
非球面透镜
均匀照明
多角度照明
illumination optical design
defect detection
annular light source
aspheric lens
uniform illumination
multi-angle
作者简介
通信作者:侯溪,houxi@ioe.ac.cn。
