Two-dimensional LED arrays for virtual display image sources

The design and fabrication of large-scale two-dimensional (2-D) arrays of v isible light emitting diodes (LED's) is described along with their implemen tation as image sources for prototype virtual displays. The LED pixels were fabricated in the InGaAIP material system using a double mesa etch process . Pixel characteristics are presented and used to predict display luminance properties. The 10-mu m square LED's produced external quantum efficiencie s of 0.5% with an emission spectrum peaked near 650 nm (red), This performa nce 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 co lumns x 144 rows (similar to VGA/8) with pixels on a 20-mu m pitch and were driven in a column major matrix addressing mode at 60 frames per second fo r image display. Pixels were driven at a constant current with pulse width modulation to achieve sixteen levels of gray. An analysis of array luminanc e uniformity is presented. Sample images of text, graphics, and gray scale images demonstrate the capabilities of the LED arrays as monochrome image s ources for virtual displays.