Micro LED Display Optical Sheet for Luminance Direction Control
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Solution Overview
Problem
Micro LED displays face inefficiencies in utilizing light due to diffuse emission from LEDs, leading to suboptimal luminance in the direction of user recognition.
Innovation Solution
Incorporating a light-emitting substrate with a semiconductor layer divided into unit regions and a light-emitting portion, paired with an optical sheet featuring unit lenses arranged in a specific direction, to collect and direct light efficiently towards the user's line of sight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light-emitting diodes are used in micro LED display, then the display can be made small, light, and thin, but the light emission becomes diffuse and light cannot be efficiently used
Solution Approach 1:
The optical sheet is divided into multiple unit lenses corresponding to multiple light-emitting portions. Each unit lens independently collects light from its corresponding light-emitting portion, enabling precise directional control of light while maintaining high light utilization efficiency. This segmentation approach resolves the contradiction by organizing the optical elements to match the spatial distribution of light sources.
Solution Approach 2:
Each unit lens is positioned and sized to match the specific characteristics of its corresponding light-emitting portion. The lens pitch, radius of curvature, and distance from the light-emitting substrate are optimized locally to collect light effectively from each LED while directing it toward the viewing direction. This local optimization ensures high luminance without wasting light.
2Illumination intensity
If light is collected in a predetermined direction to increase luminance, then light utilization efficiency improves, but luminance in shifted directions decreases
Solution Approach 1:
The unit lenses extend in a direction unparallel to the arrangement direction of light-emitting portions, creating a two-dimensional optical control structure. This dimensional approach allows the optical sheet to collect light not only in the primary viewing direction but also in shifted directions, maintaining luminance across multiple viewing angles while preserving light utilization efficiency.
Solution Approach 2:
Each unit lens serves multiple functions: it collects light from the corresponding light-emitting portion, directs light toward the primary viewing direction, and simultaneously provides luminance in shifted directions. This multi-functionality resolves the contradiction by making the optical element adaptable to various viewing conditions without sacrificing efficiency.
3Loss of energy
If unit lenses are arranged to collect light efficiently, then light utilization improves, but the optical sheet becomes more complex
Solution Approach 1:
The optical sheet design optimizes specific parameters including the pitch of unit lenses (0.025 < w/p < 0.65), radius of curvature (0.2 ≤ r/p < 1.5), and distance from light-emitting portions (0.005 < d/p < 0.2). By controlling these parameters within specific ranges, the patent achieves high light utilization efficiency with a relatively simple lens array structure, avoiding excessive complexity.
Solution Approach 2:
The unit lenses extend in a direction unparallel to the light-emitting portion arrangement, creating an extended linear array structure. This dimensional approach simplifies the overall optical design by using a single optical element type (linear array lenses) rather than requiring complex multi-element systems, while still achieving efficient light collection.
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 proposed solution effectively increases luminance in the direction of user recognition while efficiently utilizing light, addressing the inefficiencies of diffuse light emission in micro LED displays.
Implementation Method 1
an optical sheet that faces the light-emitting substrate... multiple unit lenses that are arranged in a first direction and that extend in a second direction unparallel with the first direction
Data Source
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AI summary
[Object] To increase luminance in a direction in which a display device is visually recognized. [Solution] A display device 1 includes a light-emitting substrate 10 that includes a semiconductor layer 11 that is divided into unit regions 10a and light-emitting portions 13 that are disposed in the multiple unit regions 10a, and an optical sheet 20. The optical sheet 20 includes multiple unit lenses 21. The multiple unit regions 10a are arranged in a first direction and a second direction. w/p is less than 0.025, and at least r/p is 0.2 or more and less than 0.525 and an expression (1) is satisfied, r/p is 0.525 or more and less than 1.5 and an expression (2) is satisfied, r/p is 0.2 or more and less than 0.525 and an expression (3) is satisfied, r/p is 0.525 or more and less than 0.725 and an expression (4) is satisfied, or r/p is 0.725 or more and less than 1.5 and an expression (5) is satisfied.