Research On The Signal Processing Technology Of Scanning Type Phone Screen Defect Detector

With the development of computer technology,signal processing technology has been widely used in the field of optical detection.At present,the quality evaluate of mobile phone screen in the production process mainly rely on the visual method of human,this method is not only easy to cause eye fatigue,but also of low detection efficiency. So that,the purpose of this thesis is to apply signal processing technology to the rapid detection of product quality in the production line of mobile phone screen and improve detection efficiency.This thesis designs a scanning type mobile phone screen defect detection system through the research on the principle of light forward scattering and virtual instrument technology,the system includes hardware part and software part.Firstly,the hardware part is divided into the illumination system,the measured part transmission system,the scattered light collecting system, the signal acquisition and processing system.The illumination system realizes the adjustment of the light energy,the beam shaping and the elimination of stray light,thc measured part transmission system realizes the fixed and one dimensional horizontal motion of the tested parts,the scattered light collecting system realizes the collection and photoelectric conversion,the signal acquisition and processing system realizes the signal acquisition and processing.Then,the software part of the system designs the gain control module of PMT,the step metor control module,the signal acquisition and processing module based on the Lab VIEW platform.The software system realizes the intelligent measurement and display through calling each system module from the man-machine interface.Finally,this thesis designs a defect detection system with good performance based on the integration of software and hardware.This thesis analyzes and discusses the measurement error through the test experiment.The light energy and scanning speed of the system is adjustable,it realizes the detection of mobile phone screen with high signal-to-noise ratio and large dynamic range of internal and external defects at the same time.In this system, the range of scanning speed is v= (5mm～15mm)/s,The range of detectable scattered light power is 0.5×10-8lm～0.25×10-4lm,the acquisition range of the system is O-10V,the voltage resolution reaches 4.96mV.Through the experimental of sample of mobile phone screens detected by the inspector and whose size and type of flaws are known,it differentiates the scratches with the length of 5mm and width difference of 0.04mm,the white and concave point with the diameter difference of 0.05mm,the detection results conform to the evaluate results of inspector.