Research Of On-line Testing And Sorting System On LED Optoelectronic Parameter

With the expansion of LED's application scope, the user has higher requirements on LED product quality, especially on LED brightness and wavelength consistency. Therefore, the measurement of LED parameters has higher demand. Because of the poor level of equipment matching, low detection accuracy, some enterprises' product performance can not be compared to each other. Some companies rely on the import testing and sorting equipment, thus the cost of production is very high. It will have unfavorable influence on China's LED industry structure and development in the long run. Therefore, researching on fast on-line testing of LED optoelectronic parameters and automatic sorting systems which is significant for promoting china's industrial development and enhancing LED product quality. The major work of this paper are as follow:1. The corresponding relations between the various linear CCD pixel of spectrum tester and LED wavelength is employed to realize the full spectrum measurement at the same time. The LED light source with the conversion of linear CCD and PCI-6023E is sent to computer, and processed to get the spectrum power distribution function P (λ), which can be used to calculate LED light source chromaticity coordinates, purity, peak wavelength and dominant wavelength values.2. LED on-line test circuit is designed, LED electrical parameters can be rapidly measured through the communication between the circuit and PCI data acquisition card. Communications interface circuit between the testing system and automatic sorting system is designed. It can realize automatic production pipelining of LED testing and automatic sorting through the communication between the testing system and sorting system. LED automatic sorting system includes several parts: LED transportation equipment, interval feeding equipment, feeding equipment, electricity clamping equipment and sorting equipment. This paper focuses on on-line testing technology of LED, the sorting system only for brief.3. A least squares polynomial fits LED's peak wavelength and CCD pixel coordinates curve, the analysis of the experimental results shows that: Compared with the linear fitting, Polynomial fitting can effectively improve the precision of the testing results.4. Curve fitting and Look-up successive approximation method are employed to calculate LED's dominant wavelength. Through the comparison of two methods, look-up table method of successive approximation is exported to calculate dominant wavelength, the dominant wavelength measurement error is less than 1 nm.5. Using LabVIEW software development platform, it completes the acquisition, calculation and analysis capabilities of the measured parameter through the combination of application program and hardware. The signal of the LED light, color, electrical parameters for automatic sorting is given by the testing system.Finally, the test results which is obtained by the system are given. The paper analyzes the factors which have impact on the LED testing accuracy, furthermore, a number of improvements and methods are raised.