Study on uniform irradiance of micro curved-light-emitting diode array

Abstract

The curved light-emitting diode (LED) array has so many advantages over conventional planar micro LED array such as wider viewing angles, and convenience in its actual applications:curved mobile phone screen, curved smart watch screen, and wide-angle communication illumination light source, etc. Irradiance uniformity is considered to be one of the momentous parameters for evaluating the degree of display or communication lighting devices. In order to improve the untilization of micro-curved LED array in display illumination, we focus on uniform irradiance of cylindrical and spherical micro-LED array by the method of ray-tracing. The calculation results show that the curved radius R and LED radiation parameter m are main factors affecting the uniform irradiance of the cylindrical array. We can improve the energy utilization efficiency by arranging the array pixel positions rationally. The simulation of 1010 cylindrical array with bending radius R=5 cm shows that the uniformity of maximum irradiance can reach 90.5% when detection distance z=300 cm and the detection area is defined as {(x, y)|-100 x 100, -100 y 100}. Furthermore, the irradiance distribution of spherical array is calculated and the results show that the irradiance uniformity of the single spherical array is unrelated to the number of pixels when it surpasses three. The main factors that affect the irradiance distribution of the multi-ring LED array are the ring distribution coefficient K, the normal angle 0, and the luminous flux ratio of each ring . Also the two-ring LED array model is calculated when the pixel number of the first ring is set to be 6 and the second ring is assumed to be 12. And the simulation results show that the maximum irradiance uniformity of the two-ring LED array can reach 94.8% in which the value of 0 is set to be 20, the ring distribution coefficient K=0.5 and the two ring pixel unit luminous flux ratio =20. Experimentally, we adopt the approach of the two micro LEDs to confirm the accuracy of the theory. And the results show that the irradiance distributions of two LEDs with the values of angle =13, 15 and 17 are consistent with the theoretical calculations. Thus, the theoretical and the experimental results in the paper can offer references for curved-LED display and multi-mode intelligent illumination.