Near-Eye Laser Display Modulation for Fringe-Reduced Brightness
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Solution Overview
Problem
Near-eye display technology faces challenges in providing desired display luminance using compact, lightweight, and low-power components, particularly due to etendue and polarization losses in LED illumination and interference fringes caused by coherent laser emission.
Innovation Solution
The use of multiple lasers for primary-color channels with differing cavity lengths and modulated semiconductor lasers to broaden the gain spectrum, combined using a geometric beam combiner, reduces interference fringes and enhances brightness with fewer artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If LED illumination is used for SLM illumination, then the display device can be compact and lightweight, but etendue loss and polarization loss occur reducing display luminance
Solution Approach 1:
The patent changes the illumination parameters by using laser light sources with specific wavelength and coherence properties instead of LED illumination. This allows achieving high display luminance through the SLM while maintaining a compact and lightweight display device structure.
2Illumination intensity
If coherent laser emission is used to illuminate SLM, then display luminance is improved, but interference fringes are generated causing visual artifacts
Solution Approach 1:
The patent segments the laser illumination into multiple wavelength components using a diffuser element. This segmentation of the coherent laser light into multiple wavelengths reduces the visibility of interference fringes while maintaining high display luminance.
Solution Approach 2:
The patent introduces a diffuser element as an intermediary between the laser source and the SLM. This diffuser mediates the coherent laser light by scattering it into multiple wavelengths, thereby reducing interference fringes while preserving brightness.
3Illumination intensity
If multiple lasers with differing cavity lengths are used for primary-color channels, then interference fringes are reduced and brightness is enhanced, but device complexity increases
Solution Approach 1:
The patent combines multiple lasers with differing cavity lengths into a unified illumination system for the primary-color channels. This merging approach reduces interference fringes and enhances brightness while managing the complexity through integrated optical design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables compact, lightweight, and energy-efficient near-eye displays with reduced visual artifacts, achieving high brightness and improved power efficiency.
Implementation Method 1
a laser, a drive circuit coupled operatively to the laser... trigger the emission from the laser
Implementation Method 2
a spatial light modulator (SLM)... configured to receive emission from the laser and to direct the emission in spatially modulated form
Implementation Method 3
drive a periodic current through a gain structure of the laser... the wavelength band of the emission is broader than the wavelength band of emission from the same laser when driven by unmodulated drive current
Implementation Method 4
a pupil-expansion optic... configured to receive the spatially modulated emission from the SLM and to provide an expanded exit pupil
Data Source
AI summary
A near-eye display device comprises a pupil-expansion optic, a laser, a drive circuit coupled operatively to the first and second lasers, a spatial light modulator (SLM), and a computer. The SLM has a matrix of electronically controllable pixel elements and is configured to receive emission from the laser and to direct the emission in spatially modulated form to the pupil-expansion optic. Coupled operatively to the drive circuit and to the SLM, the computer is configured to parse a digital image, trigger the emission from the laser by causing the drive circuit to drive a periodic current through a gain structure of the laser, and control the matrix of pixel elements such that the spatially modulated form of the emission projects an optical image corresponding to the digital image, wherein the periodic current includes plural cycles of modulation driven through the gain structure while the optical image is projected.