According to IESNA-LM-79-80, when spectroradiometer integrating sphere system tests LED flux, light source’s self-absorption can influence test result, therefore, it usually introduces Auxiliary Lamp. The induction of absorption Auxiliary Lamp can solve the absorption problem of the tested lamp itself.
How to use Auxiliary Lamp correctly? Lisun LPCE-2(LMS-9000A) High precision Spectroradiometer & Integrating Sphere System for LED has 4 steps for measurement, shown as follow:
Step 1: Import the data of standard lamp, light standard lamp for system calibration, save the calibration file;
Step 2: Close standard lamp and don’t remove, light auxiliary lamp, record the standard lamp’s absorption condition and save it as calibration file;
Step 3: Change the standard lamp to the tested lamp, light auxiliary lamp, record the absorption condition of the lamp under test and save it as calibration file. Software can automatically calculate the spectrum self-absorption factor of standard lamp and the lamp under test;
Step 4: Extinct the auxiliary lamp, light the lamp under test, choose the calibration files above to do test. When software calculates the result, it will automatically compensate back the spectrum absorption-factor from Step 3 to get the correct result.
This is the requirements of USA Energy Star LM-79 for Integrating Sphere LED measurement. For a sphere-photometer system, the auxiliary lamp does not have to be limited to incandescent lamps. Rather, it is advantageous to use an auxiliary lamp that has a spectral distribution similar to those of the SSL products typically measured, so that self-absorption is measured accurately especially when the self-absorption is very large (a<0.8) or when the housing of SSL product under test is large and strongly colored. The auxiliary lamp needs to be stable throughout the self-absorption measurement of all SSL products under test. A stable white LED source, for example, may be used.