Research On Photoelectric Test System For LEDs Based On Delphi

Electrical Characteristics and optical properties are the mainly parts of LED performance evaluation. How to make the test rapidly and accurately has always been the hot spot of the industry. With the development of technology, new test methods have promted as well as the precision of the instrument constantly improved. But some theory methods can not be application to experiments. This is because the operating systems of instrument usually could not meet the request of the researchers. And some experiments need to two or more instruments to support the testing. This article developed two sets of electrical characteristics test system, and on this basis to develop a set of complete LED spectrum test system, which inculding the following parts:a) The programmable automation test system for LED electrical characteristics is based on Keithley2400,2510-AT temperature controlling source, the jig LED850of the Instrument System and the GPIB cards of the NI company. Automation system’s main features includes the measurement of LED VI characteristic curve under different temperature, the VT curve and the relation curve between temperature and time under different coefficient of PID.b) The constant current/pulse test system is based on Keithley2611,2510-AT temperature controlling source, the jig LED850from the Instrument System company and the GPIB cards from the NI company. This system allows the user to a fully automatic test about controlling the temperature on computer. Its main features include automatic measurement of testing the dc volt-ampere or pulse volt-ampere characteristic curve under different temperature, the curve of leakage current with time under different reverse voltage, and the curve of forward voltage with time under the fixed input current (dc/pulse). Users only need to set up operation parameters and the required conditions, the system can automatically complete the test.c) HR4000spectrum test system has been completed on the basis of the first two software programming. This system has based on HR4000spectrometer of Ocean Optics, GS610source of Yokogawa and GPIB interface card of National Instruments. In addition to the basic spectrum test function, the system can carry out other operations:1) draw a three dimensional spectrum and support test modes for multiple spectrum tests,2) the spectrometer can control the integration time automatically,,3) the wavelength and optical power calibration function has been added.d) The chromaticity parameters test programming is based on the calculation method of colorimetry. According to several calculation methods for the chromaticity coordinates, CRI, CCT, the dominant wavelength and the peak wavelength, we choose a suitable programming to add the chromaticity parameters test to the HR4000system, which makes the system more perfect. This article exposes relevant programming codes, it may has certain reference value for related programming.e) Based on the test systems above, this article has carried on the test experiment, and compared the result to the current mainstream detection equipment, to verify the validity of the calculation of the system.