Google Inc.

Aurelien Jean Francois David

Gang He

Carlin Vieri

Patrick F Brinkley

A full color display includes multiple pixels and has a white point, a direction of emission and a solid angle of emission around the direction of emission characterized by a half-cone angle θ. Each pixel includes: a sub-pixel including a red LED having a first geometry emitting red light into a range of emission angles, such that a fraction of the power emitted within the solid angle of emission is at least 1.2*(1−cos(θ)); a sub-pixel including a green LED having a second geometry emitting green light into a range of emission angles, such that a fraction of the power emitted within the solid angle of emission is at least 1.2*(1−cos(θ)); and a sub-pixel including a blue LED emitting blue light into a range of emission angles, such that a fraction of the power emitted within the solid angle of emission is at least 1.2*(1−cos(θ)). The LEDs are configured such that, in any direction within the solid angle of emission, white light emitted by the display has a chromaticity difference Du'v′ from the white point of the display which is less than 0.01.

Light emitting diodes with directional emission and displays including the same

Methods and devices are presented for transforming a layout of a densely packed grid of micro-LED light emitters to a layout of a square rectilinear pixel grid to achieve compatibility with hardware and software used in imaging and display technologies. In particular, a pattern of regular hexagonal emitter cells for fabrication on a III-nitride substrate can be transformed to a square pixel array of irregular hexagonal trichrome pixels that are readily addressable. Separation between adjacent trichrome pixels, and between their constituent emitters, can be established for overlay tolerance, while maintaining a cell packing density of about 70% and a pixel pitch of about 4.0 μm. Wavelength and quantum efficiency properties are shown to depend on optical current density, which can be determined by the emitter area specified in the grid layout.

Trichrome pixel layout

A micro-LED driver applies a low baseline power (i.e., a baseline voltage or current) to pre-charge a micro-LED in a nominally-off (i.e., non-light-emitting) state in addition to applying an operating driving power to drive the micro-LED in a light-emitting state. By pre-charging the micro-LED prior to applying the operating driving power, the micro-LED driver significantly decreases the time between application of the operating driving power and onset of emission of light from the micro-LED. In some embodiments, the micro-LED driver applies an operating driving power having multiple phases of current density to reduce the time between application of the operating driving power and onset of emission of light from the micro-LED.

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San Francisco, CA, United States of America

Aurelien Jean Francois David