| The measurement system of LED photoelectric parameter is the coreof the LED sorting equipment. It directly determines the speed and accuracy of LEDsorting. At present, LED sorting equipment send data to PC by using spectral cardand electrical parameter card after data collection. And PC will calculate and displaythe optical parameters and electric parameters. With LED production capacitycontinues to expand, the speed and price of the existing LED sorting equipment isincreasingly threatened. Therefore, in the process of LED photoelectric parametersmeasurement, it’s very necessary to further dig on measurement speed and furtherdepress on cost. This issue is carried out base on the above two reasons.First, this paper elaborated on testting principle and method of LED luminousmechanism, main electrical parameters, optical parameters and colorimetryparameters. In accordance with the relevant principle and method, the wholestructure of the rapid LED photoelectric parameters measurement system is designed.The system is divided into light parameter detection module (homemadespectrometer) and the electrical parameter testing and displaying module with twopieces of Cotex-M3chip of NXP company (LPC1768, hereinafter referred to as the"M3") as processor. The two modules only transfer the data which is calculation forcolorimerty parameters through the USB. It’s saving the time.Light parameter detection module is a homemade, low-cost fiber spectrometer.The optical system realize rapid spectral measurement in350-1000nm range base oncross asymmetric (Czerny-Turner) imaging system with high sensitivity, low cost ofCCD as light sensors. After testing, the instrument integration time is1ms-65s. Thespectral resolution is better than1nm (at the blaze wavelength). And the pixelresolution is0.372nm/pixel.Electrical parameter testing and displaying module take M3chip as control core, too. In order to measure the LED electrical parameters, programmable constantcurrent constant voltage source and the forward voltage and reverse leakage currentmeasurement circuit are designed. It can obtain the corresponding electricalparameter values cooperating with AD conversion circuit. At the same time, theman-machine interface based on the M3has been designed by using the combinationof UCOS-II and UCGUI. It can realize the displaying of main parameter. The M3of light parameters module calculated colorimetric parameter that detection requiresbase on measured spectral data when the light parameter module is triggered by theUSB port. And the data is passed to the electrical parameter module via USB. Thenthe display module of electrical parameter module will display the data inman-machine interface. The design of man-machine interface makes this system canbe completely divorced from PC. It can shorten the time of data transmissionbetween photoelectric parameter module and display terminal. And it may alsopromote the system’s convenience and testing speed while the cost of system isreduced.The testing results basically meet the requirements by using the LEDphotoelectric parameters measurement system for actual test. At the same time, onthe premise that isolate from LED sorting machinery control, the system enhance thetesting time of photoelectric parameters. At the premise of isolation from the LEDsorting machinery, the system can enhance the testing time of photoelectricparameters. In practical applications, this system can get LED photoelectricparameters quickly and has higher sensitivity and convenience. It may meet the... |
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