Design And Verification Of The TFT-LCD Flicker Testing And Adjustment System

TFT-LCD is one of the core hardware of display technology and the flicker is one of the most important performance indexes in the industry.In the manufacturing process of TFT-LCD,it is necessary to measure and debug the flicker of every piece of LCD in order to ensure that its quality would satisfy the consumers' needs.At present,the main instruments used for flicker measurement in the industry are Minolta CA310 and Klein K8.Their prices are so high(CA310 is about 100,000 RMB,K8 is about 40,000 RMB)that the cost of production is too large to be widely used.Every manufacturer is in sore need of developing a set of flicker measurement system and adjustment tools with low cost and high efficiency.Based on the above background,a flicker testing and adjustment system for TFT-LCD is elaborated in this paper.A photosensitive sensor used to collect the flicker light signal of the LCD can convert the light signal into electric signal.After amplified via the amplification circuit,this analog electric signal is converted into digital signal via the A/D conversion module in the MCU.By means of the flicker analysis and testing software algorithm,the minimum value of Flicker Modulation Amplitude(FMA)is found in a pile of collected digital signals and the auto testing and adjustment of flicker is realized.The main contents of this paper are as follows:1.The cause of TFT-LCD flicker is analyzed.The FMA defined under the contrast method is adopt as the measurement parameter of LCD flicker.This provides a theoretical basis for the development of LCD flicker testing and adjustment system.2.The characteristics of the existing manual/automatic flicker testing and adjustment system are compared and analyzed with the CA310 and Klein K8.The reasons for low accuracy of present flicker measurement are explored.Based on these research results,a new flicker testing and adjustment system has be implemented.3.Implement the overall and circuit design of the new testing and adjustment system.The 2-D and 3-D simulation design of the whole system are carried out with the aid of CAD and Solid works software to ensure the overall size,working distance,parallelism between the photosensitive surface and the monitored display screen and the length of the measuring manipulator meet the practical requirements.According to the design results,the physical device of flicker testing and adjustment system has been fabricated.4.A comparative study of flicker analysis and testing algorithms has been implemented.An algorithm of ADC interleaved sampling and scanning is proposed and integrated into the new testing and adjustment system that realize full-order scanning during a fixed scanning time(about 300ms per 10-order scanning time).5.Debugging and verifying of the reliability and consistency of the new flicker testing and adjustment system are carried out.Comparing with the testing results of CA310,the accuracy of the new measurement system is verified preliminarily.Furthermore,the flicker of 10 pieces of TFT-LCD screens selected randomly using different types of testing systems and by different operators in different work time is measured.A comprehensive testing data is obtained with Minitab software.The data show that:the overall variance(%SV)of the new measurement system is 2.05%,which is less than the standard and requirement of acceptable%SV(%SV is less than 10%).This result proves that the new measurement system has good repeatability and reproducibility.6.On-line verification of TFT-LCD module has been executed by using a new testing and adjustment system.The results show that the new measurement system solves the problem of measurement deviation caused by subjective judgment of human eye in manual system.Compared with the existing automatic measurement system,the average time of one-piece flicker detection of the new measurement system is reduced by 8.3 seconds,with a decrease of 68.6%.The success rate of one-time adjustment is increased from 86.4%to 98.3%,which meets the requirements of automation,high efficiency and reliability of the flicker measurement system.