Method for measuring brightness of LED light source

Mar 25, 2019

    A solar street light, the first feeling for the user when lighting at night is how the brightness, light effect. For street lamp manufacturers, a light output test report can be made at the factory. The current solar street light controller integrates the LED constant current source, making it easier for the user to set the output power according to the light output demand. In order to achieve energy-saving purposes and achieve lighting effects, LED lamp manufacturers need to make corresponding countermeasures according to user needs. A test report can be issued when necessary.

    There are some special points to note when measuring LED light output. In terms of light capture, a 6in integrating sphere can meet the demand. Larger integrating spheres can be used as long as the sensitivity is sufficient to ensure the accuracy of measuring the light output of a single LED.

The heat of the LED itself is more difficult, and the heat will cause the luminous flux to continue to drop until it reaches a thermal equilibrium state. Even if the LED is mounted on a large heat sink, the junction temperature will rise by 10-20 °C at the moment of measurement, resulting in a measurement of luminous flux that is a few percentage points worse than the measurement at room temperature. LED manufacturers use 25ms current pulses to drive the LEDs to keep the junction temperature at room temperature. Unless a dedicated device is used, it is impossible to obtain the same luminous flux measurement as in the data sheet.