Research On Lighting System For Defect Detection Of Molded Lens

Molded plastic lens is widely used in security lens because of its strong plasticity,easy production and low cost.In some large-scale lens factories,the monthly production can reach more than 10 million pieces.Some lenses will inevitably have defects,which will reduce the light transmittance of the lenses and affect the imaging quality of optical products.At present,most enterprises still use artificial visual inspection to detect the lens defects one by one.This traditional detection method has poor accuracy and low efficiency.In order to solve the problem of lens detection,the machine vision detection technology with the advantages of objectivity,non-contact and continuity can be used in industrial production detection,which can improve the efficiency and accuracy of defect detection.As the premise of machine vision imaging,lighting system can enhance the contrast of defect part,simplify image processing algorithm and improve detection accuracy and efficiency.In this paper,a back lighting system for the detection of 35 10 mm molded lenses in a 80mm×60mm lens tray is designed,and the contrast experiments of different lighting systems are carried out.Experimental results show that the illumination can provide high uniformity and high contrast.This paper introduces the machine vision detection system.In order to detect the defects with scratch width of 60μm and equivalent diameter of bubbles and pits of 400μm and obtain high-definition images,a 2/3-inch CCD camera and an optical lens with focal length of 15 mm are selected.In the lighting system,the light source and lighting mode are studied and analyzed,and the secondary optical design based on LED is carried out.In this paper,the object of illumination is the transparent molded lens.Combined with the material of lens and the habit of human eye detection,the back lighting mode is selected to carry out the lighting optical design of the combination of strip light source and face light source.Firstly,the 3D model of combined light source is built in SolidWorks,then the model is imported into LightTools and OptisWorks for optical simulation.The simulation results show that when the distance between the target illumination surface and the combined light source is 80 mm and the mixing distance is 16 mm,the uniformity of illumination is 91.5%,the uniformity of brightness is 92%,and the light distribution curve is Lambertian distribution,which meets the uniformity requirements of industrial detection.Build lighting system and carry out experiments to obtain relevant experimental images.Through comparative analysis,the combined light source has advantages over the ring light source,the parallel light source and the face light source.It can not only provide high uniformity and contrast,but also meet the detection of a variety of defects.The image obtained by the combined light source is processed,which reduces the difficulty of image processing and makes the detection of lens defects more accurate and easy.