At present, we should pay special attention to the measurement standards of the LED photoelectric measurement.
The optical radiation of light emitting diode is actually the directional imaging beam, therefore it can not measure and calculate light intensity according to the general photometric measurement(photometric sphere) rules in the textbook. That is to say, in general, the luminous intensity can not be calculated by the inverse ration law of the plane illumination and distance square. CIE 127-1997 ”light emitting diode measurement” publications have identify the LED intensity testing as the concept of average intensity, and stipulate the uniform testing structure, including the size of detector surface and the requirements of the testing distance. This lays the foundation for accurate test comparison on LED. Although the CIE documents are not the international standards, it has been internationally recognized and adopted. The LED industry standards in China are in consistent with the methods of CIE document.