Microlens LED Pixel Layout for Subpixel Light Uniformity
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Solution Overview
Problem
Existing display apparatuses using LEDs as pixels face challenges in achieving high light uniformity between subpixels due to variations in luminous efficiency across different color-emitting LED cells, particularly those emitting longer wavelengths.
Innovation Solution
The design includes LED cells with varying widths and quantum well layer configurations to match luminous efficiency, with wider areas and adjusted quantum well layers for higher wavelength-emitting cells, and microlenses to enhance light convergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LED cells of uniform width are used across all subpixels, then manufacturing is simplified, but light output uniformity deteriorates due to varying luminous efficiency at different wavelengths
Solution Approach 1:
The patent applies local quality by configuring LED cells with different widths according to their specific wavelength requirements. Red LED cells are made wider than green and blue LED cells to compensate for their lower luminous efficiency at longer wavelengths. This localized structural adjustment ensures that each subpixel type produces comparable light output, resolving the uniformity issue while maintaining a relatively simple manufacturing process.
2Illumination intensity
If wider LED cells are used for longer wavelength emission, then light output uniformity is improved, but device complexity increases due to varied cell configurations
Solution Approach 1:
The patent employs parameter changes by systematically varying the width parameter of LED cells based on their emission wavelength. Red LED cells operating at longer wavelengths are assigned larger widths, while green and blue LED cells at shorter wavelengths use smaller widths. This controlled parameter variation achieves light output uniformity across different subpixel types while maintaining a predictable and manageable device structure.
3Productivity
If microlenses are added to enhance light convergence, then light efficiency is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent introduces microlenses as intermediary optical elements positioned above the LED cells. These microlenses serve as mediators that focus and direct the light emitted by the LED cells, improving light extraction efficiency and convergence. By placing this optical enhancement layer uniformly across all subpixels, the patent achieves improved light efficiency while keeping the manufacturing process relatively straightforward through a standardized additional fabrication step.
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 significantly reduces light output variations among subpixels, ensuring improved light uniformity and efficiency in color reproduction.
Implementation Method 1
a reflective layer on the passivation layer, the reflective layer configured to emit light toward upper surfaces of the plurality of LED cells
Implementation Method 2
a plurality of microlenses respectively on the plurality of subpixels
Data Source
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AI summary
A display apparatus includes a circuit board (200) including a driving circuit, a pixel array on the circuit board (200) and including unit pixels (PX), each of the unit pixels (PX) including a plurality of subpixels (SP1, SP2, SP3), and a plurality of microlenses (180R, 180G, 180B) respectively on the plurality of subpixels (SP1, SP2, SP3), where the pixel array further includes a plurality of light-emitting diode (LED) cells each respectively including a first conductivity-type semiconductor layer (112), an active layer (114R, 114G, 114B), and a second conductivity-type semiconductor layer (116) that are sequentially stacked, a passivation layer (120) on side surfaces and lower surfaces of the plurality of LED cells, a reflective layer (160) on the passivation layer (120), the reflective layer (160) configured to emit light toward upper surfaces of the plurality of LED cells, a gap-fill insulating layer (141) on the side surfaces and lower surfaces of the plurality of LED cells, and a first connection electrode (130) on the gap-fill insulating layer (141), and connected to the first conductivity-type semiconductor layers (112).