Research And System Design Of Illumination Method For The Highly Reflective Rotary Surface Defects Detection~1

The highly reflective rotary surfaces are the surfaces of smooth and revolving parts which have very strong reflective properties,almost mirror-reflective,and can clearly reflect the image of the objects,such as the surfaces of bearing steel balls,rollers,precision shafts and so on.It may occur surface defects such as pits,scratches,abrasions,and foreign materials during those parts' processes of production,which cause damage to the performance and longevity,even result in serious accidents and significant economic losses.Therefore,the accurate detection of the highly reflective rotary surfaces' defects is very important.At present,the visual detection method is mainly used.Illumination scheme during visual inspection directly affects the accuracy of defects detection.In view of this,a new adaptive lighting system based on space light modulation is developed by using the technology of precision machinery,photoelectric technology and automatic control in this paper.It provides an effective solution for the vision detection of the highly reflective rotary surfaces' defects.At the same time,the uniform and collimating light source,uniform illumination stripe and adaptive light intensity modulation technology are systematically studied and experimentally verified.Firstly,based on the lighting scheme of the design system,the collimating and uniform system based on LED light source is designed and simulated by using Tracepro software.Based on the analysis and comparison of the currently widely used LED collimating lens design,a freeform surface lens structure was designed.The model was simulated by Tracepro software,and its optical properties were studied to verify the efficiency and feasibility of the collimating lens.Then,two common methods of homogenization of integrator and the fly-eye lens were compared and discussed.The model of fly-eye lens was established by using the Boolean operation in the Tracepro software.Finally,the uniformity of the illumination was simulated using the designed LED collimating lens and fly-eye lens.The result shows that the designed collimating lens and fly-eye lens can achieve the uniformity of the illumination.Secondly,the uniform algorithm of straight stripe and circular stripe was designed in order to meet the requirements of lighting stripes for different shape and radius of curvature radii.The rationality of the selection of the stripes and the correctness of the uniform fringe algorithm were verified in Tracepro,and the projection model of the lighting system was also established.Then,FPGA was used to control the state of DMD micro-mirrors in order to achieve uniform illumination of projected stripe.Finally,adaptive control technology based on CCD feedback mode was developed to control intensity of the middle fringes.Thirdly,an experimental platform for visual inspection system of highly reflective rotary surface defects was built by using the designed optical system.At first,the uniformity of the light source was verified.Then,illumination was realized by uniform fringes,DMD control technology based on FPGA and adaptive light intensity modulation technology.It solved the effect of halo in the visual inspection of highly reflective rotary surface defects.The feasibility of uniform fringe algorithm and intensity adaptive modulation method was verified by experiments.In this paper,a new method of adaptive fringe illumination based on spatial light modulation was implemented,which satisfies the requirement of visual detection for highly reflective rotary surfaces with different curvatures.This method also has important reference value for other visual inspections.