Research On Key Technology Of Defect Detection Based On Fringe Reflection

In the field of industrial production and product maintenance,product surface defect detection is an important link.With the increasing demand for electronic products and the improvement of product quality in today's society,how to quickly detect and locate product surface defects and their locations has always been a major problem for contemporary electronic product manufacturers and repairers.Traditional human eye detection has many drawbacks,which is difficult to meet the needs of manufacturers.Therefore,a non-contact,automated,accurate and efficient detection method that can replace manual defect detection is a research hotspot at present.This paper mainly studies defect detection technology based on fringe reflection and proposes a modulation degree analysis defect detection method which combines phase measurement deflection and modulation measurement profilometry.This technique is suitable for defect detection of mirror and mirror-like objects.The specific research of this article can be summarized into the following aspects:Firstly,several methods that can be used to characterize defects in the fringe reflectance method are studied.The advantages and disadvantages of different characterization methods are analyzed.Through analysis and experiments,it is concluded that the modulation degree detection method is comparable to the phase,gradient,and curvature detection methods.The defect area is clearly distinguished and the detection effect is the best and stablest.This paper studies acquisition methods of modulation degree information that mainly include Fourier transform method and phase shift method.The Fourier transform method obtains fringe modulation in real time,and only one fringe can be used for defect detection.But the accuracy is low.In contrast,the phase shift method has strong stability and anti-noise ability,which is more suitable for defect detection.Secondly,several factors that affect the detection accuracy of modulation defects are analyzed.To break the limitation of traditional stripe defect detection,a modulation defect detection method based on sector fringe is proposed.Experimental results demonstrate that the detection method of the modulation degree of the sector fringe is not affected by the direction of the defect,which can detect the defect more completely and has higher sensitivity and accuracy.The influence of nonlinear error propagation on the modulation degree is discussed and the fringe is nonlinearly corrected by the gray-scale compensation algorithm.As the result shows,this method can eliminate the influence of nonlinear error on the modulation degree map,which is more conducive to the follow-up defect detection.Thirdly,this paper studies the defect image processing algorithm and put forward the quality map for defect identification.This method is different from the traditional binarization method of defect identification.The modulation degree-phase shave deviation quality map is introduced to identify and locate the defects.The simulation and experimental verification are carried out.Finally,an experimental platform for the defect detection system based on fringe reflection is built.The platform can detect defects on the smooth surface of the notebook shell and the rolling surface of industrial bearing rollers.Experiments show that the device can detect defects with a minimum size of 0.07 mm,and the device has good stability.The noise is stable within-2to +2 gray levels,which indicates that the defect detection method based on fringe reflection proposed in this paper has a certain feasibility.