As a new light source, LED compared with the traditional light source is very different in their structure and luminescence properties. Due to the LED itself since the absorption effect and integrating sphere inside block screen bring out measuring error, continue to use the traditional integrating sphere for measuring leds luminous flux error is bigger. By software simulation data and theoretical calculation proved that LED should be Placed in the inner wall of the integrating sphere with detector probe into 90 degree in the same plane.
The difficulty of Luminous efficacy is in luminous flux testing，Compared with the traditional light source，because of the particularity of the LED，although the international commission on illumination
(CIE) and the United States, Canada and other countries of qualitative research institutions is proposed LED luminous flux testing methods，But now have not methods be recognized by international can be close to simple test method of traditional light source luminous flux yet .
Now the existing problems of LED luminous flux testing method include:1) using photovoltaic detector can’t realize to the LED V (A) the accurate matching in all spectra,Especially the detector exists many error in blue and red wavelengths,thus lead to errors with the measurements;2)use traditional light source of luminous flux testing method placed Block screen in the integrating sphere,Due to test the LED’s integrating sphere is very small,Even only 5 cm in diameter,Integrating sphere theory will not be able to meet, thus resulting in testing the principles of error; 3) if make the standard lamp place in the inner surface of the integrating sphere,Towards in all direction‘s traditional standard lamp will not be able to use,using LED standard lamp ,there exist difficult to achieve spectrum calibrate problems.Above problems, make the LED luminous flux test has not been perfect and unified method,thus influences on the properties of the LED,it is not conducive to the development of LED industry.