Fig. 1. Relationship curves of LED’s luminous flux and forward working current

Fig. 2. Spectral curves of selected LED

Fig. 3. Structure diagram of integrating sphere

Fig. 4. Overall design block diagram

Fig. 5. Diagram of LED constant current driving circuit

Fig. 6. Simulation results

Fig. 7. Reference voltage source circuit

Fig. 8. Test platform of radiometric calibration light source

Fig. 9. Fitting curve of control voltage and operating current

Fig. 10. Stability of the output spectral