Two-dimensional LED arrays for virtual display image sources

The design and fabrication of large-scale two-dimensional (2-D) arrays of visible light emitting diodes (LED´s) is described along with their implementation as image sources for prototype virtual displays. The LED pixels were fabricated in the InGaAlP material system using a double mesa etch process. Pixel characteristics are presented and used to predict display luminance properties. The 10-μm square LED´s produced external quantum efficiencies of 0.5% with an emission spectrum peaked near 650 nm (red). This performance level allowed the target display luminance of 10 fL to be attained with just 2.9 mW of array power consumption. The LED arrays consisted of 240 columns×144 rows (~VGA/8) with pixels on a 20-μm pitch and were driven in a column major matrix addressing mode at 60 frames per second for image display. Pixels were driven at a constant current with pulse width modulation to achieve sixteen levels of gray. An analysis of array luminance uniformity is presented. Sample images of text, graphics, and gray scale images demonstrate the capabilities of the LED arrays as monochrome image sources for virtual displays