| Light-emitting diode (LED) and Laser diode (LD) are widely used in everywhere of human life now. When used in medical and national defense field, it requires higher performance of the LEDs in the quality and reliability. While measuring the small change of the device's characteristics in using is most effective mean in predicting its reliability. So it is very sense to studying how to measuring the characteristics of LED and LD exactly and rapidly when in using.This thesis made a detailed introduction of LED/LD's interior structure, light emission mechanism, the meaning and measuring methods of each characteristic. V-I characteristics, P-I characteristics, space power distribution and spectrum of 5mm packaged InGaAlP-based red and yellow LEDs, InGaN-based green and blue LEDs, InGaN-based phosphor-converted white LEDs, PF-LD were measured. Microscopic luminance and junction temperature versus spectrum characteristics of such LEDs, and the polarization ratio of a FP-LD were also measured.There are still few researches on the LEDs's microscopic luminance and junction temperature versus spectrum characteristics. From the result, for the tested LEDs, when the forward current is bigger than 20mA, their microscopic luminance obeys this formula: white LED>yellow LED>green LED>red LED>blue LED.Two methods, namely drive by constant current while change environment temperature and drive by variational current in constant environment temperature, were used to measuring the junction temperature and spectrum of aforementioned LEDs. The results show that for red and yellow LEDs the peak wavelength is proportional to the junction temperature, and for white LEDs the ratio of the total radiant energy (W) to the radiant energy within the blue emission (B) is proportional to the junction temperature. So, for these three types LEDs a noncontact method for determining junction temperature by measuring spectrum is developed, which is very important for un-damaged testing of LED junction temperature. |
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