LED arrays with pixel numbers of 3×3, 4×4, and 5×5 have been studied in this paper in order to enhance the optical output power and decrease heat dissipation of an AlGaInP-based light emitting diode display device (pixel size of 280×280 µm) fabricated by micro-opto-electro-mechanical systems. Simulation results showed that the thermal resistances of the 3×3, 4×4, 5×5 arrays were 52°C/W, 69.7°C/W, and 84.3°C/W. The junction temperature was calculated by the peak wavelength shift method, which showed that the maximum value appears at the center pixel due to thermal crosstalk from neighboring pixels. The central temperature would be minimized with 40 µm pixel pitch and 150 µm substrate thickness as calculated by thermal modeling using finite element analysis. The modeling can be used to optimize parameters of highly integrated AlGaInP-based LED arrays fabricated by micro-opto-electro-mechanical systems technology.

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.

Images taken by space telescopes typically have a superb spatial resolution, but a relatively poor sampling rate due to the finite CCD pixel size. Beyond the Nyquist limit, it becomes uncertain how much the pixelation effect may affect the accuracy of galaxy shape measurement. It is timely to study this issue given that a number of space-based large-scale weak lensing surveys are planned. Using the Fourier_Quad method, we quantify the shear recovery error as a function of the sampling factor Q, i.e., the ratio between the FWHM of the point-spread function (PSF) and the pixel size of the CCD, for different PSFs and galaxies of different sizes and noise levels. We show that sub-percent-level accuracy in shear recovery is achievable with single-exposure images for Q ≲ 2. The conclusion holds for galaxies much smaller than the PSF, and those with a significant level of noise.