Laser-Illuminated Display Polarization Layout for Uniform Brightness
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Solution Overview
Problem
Laser-based displays face issues of image non-uniformity and eye-safety due to high brightness requirements, particularly in bright outdoor conditions, and existing technologies struggle to maintain uniformity and safety simultaneously.
Innovation Solution
The display employs a configuration of multiple lasers with specific orientations and scanning patterns, combined with polarization management and depolarization techniques to distribute intensity and reduce flicker and eye-strain, while maintaining brightness and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high brightness is used to ensure visibility in bright outdoor conditions, then visibility is improved, but image non-uniformity and eye-safety issues worsen
Solution Approach 1:
The patent divides the single high-power laser beam into multiple lower-power beams by using multiple lasers (e.g., three lasers for RGB colors) that scan in coordination. This segmentation reduces the intensity concentration that causes eye-safety issues while maintaining overall brightness through additive combination of multiple beams.
Solution Approach 2:
The patent introduces temporal dimension by using sequential scanning of multiple lasers across the display field. Instead of all lasers illuminating simultaneously (spatial dimension only), the system scans lasers in time-multiplexed sequences, distributing energy over time while maintaining perceived brightness through persistence of vision.
2Illumination intensity
If high brightness is used to ensure visibility in bright outdoor conditions, then visibility is improved, but image non-uniformity worsens
Solution Approach 1:
The patent applies different scanning patterns and timing to different regions of the display field to compensate for non-uniformities. By adjusting local illumination characteristics (scan speed, dwell time, beam positioning) in different zones, the system achieves uniform overall brightness despite variations in individual laser contributions.
Solution Approach 2:
The system incorporates feedback mechanisms where the control unit adjusts laser intensity and scanning parameters based on detected image uniformity metrics. This closed-loop control compensates for variations in laser output and optical path differences, maintaining uniform brightness across the display field.
3Object-affected harmful factors
If multiple lasers are used to maintain brightness and safety, then eye-safety is improved, but device complexity worsens
Solution Approach 1:
The patent combines multiple laser beams into a single optical path using beam combining optics, allowing them to traverse the same scanning mirrors and projection optics. This merging approach reduces the number of separate optical channels needed, simplifying the overall device architecture despite using multiple lasers.
Solution Approach 2:
The scanning mirrors and projection optics serve multiple functions: they guide all laser beams through a single optical path, perform spatial scanning, and enable color separation/recombination. This multi-functionality reduces the need for separate components for each laser, thereby reducing overall device complexity.
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
The solution effectively reduces eye-strain and flicker, enhances image uniformity, and increases safety by distributing intensity and broadening the point spread function of blue light, ensuring compliance with eye-safety thresholds without compromising brightness.
Implementation Method 1
The display includes a birefringent material configured to rotate a polarization of blue light generated by the blue laser by 90 degrees
Implementation Method 2
A scanning optical arrangement generates a scanning motion of the red light beam, the green light beam and the blue light beam in a two-dimensional scanning pattern
Data Source
Figure 1A~1B
Figure 2A~2D
Figure 3A~3C
AI summary
A display for displaying an image to a viewer includes an image generator having an illumination subsystem generating illumination of at least a first color, the image generator employing the illumination to generate an image. Projection optics projects illumination from the image for display to the viewer. The illumination subsystem includes a first laser generating a first laser beam of the first color with a first polarization and a second laser generating a second laser beam of the first color with a second polarization. The first and second polarizations are orthogonal at at least one location within the projection optics, thereby projecting a quasiunpolarized image.