Design Of New Compact LED Flux Test System

The application of LED (light emitting diode) in lighting can help to reduce energy consumption in lighting. However, the difference in measured results of LED’s total luminous flux by different organizations is above40%, which is caused by the particularity of LED, while the difference in measured results of traditional light source is below ten percent. Therefore, how to measure the photometric quantities of LED light sources rapidly is one important factor which may depend whether LED can be widely used in efficient lighting in the further.A novel integrated LED luminous flux measurement system based on spectral mismatch correction theory and linear response quality of silicon solar cell is proposed by this paper. First, this measurement system integrates fiber spectrometer to correct the spectral mismatch between measured LED and standard LED. Second, expensive large area silicon photodiode is replaced by low cost solar cell to act as the detector in the system. Third, Compound Parabolic Concentrator (CPC), which is small in volume and has high light collection efficiency, is applied as the concentrator in this system.An amplifying circuit based on OP07which can transform and amplify the short-circuit current signal of solar cell is applied in hardware design. Then, spectral mismatch correction is made based on the amplified photoelectric signal of solar cell and the spectral signal obtained by fiber spectrometer. The final luminous flux after spectral mismatch correction is displayed on LCD screen.To verify the feasibility of this novel measurement system (named Spec-CPC), we measured several groups of LED samples including white LEDs, and a comparison was made to the measurement results of National Institute of Metrology P. R. China (NIM). According to experiment results, the accuracy of total luminous flux measurement is greatly improved by the application of fiber spectrometer in the spectral mismatch correction of different color LEDs. Above all, the total luminous flux of high power LED with only forward intensity distribution can be measured precisely by the Spec-CPC system, the measurement method is easy, the measurement period is short, and the volume of the whole system is relative small, which makes it convenient for rapid measurement in production line.