OLED Display Back Cover Structure for Polarization-Based Dark Spot Reduction
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Solution Overview
Problem
The integration of optical devices such as light sensors under the display in mobile devices causes undesirable distortions and dark spots due to light reflection and scattering, which interferes with the intended luminance of the OLEDs.
Innovation Solution
Incorporating a reflection attenuating layer, comprising quarter wave plates and linear polarizers, to reduce light reflection at the interface between the display panel and the air gap, thereby minimizing interference with pixel circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a light sensor is positioned under the display to expand display area, then display coverage is improved, but light reflection and scattering cause dark spots and visual distortions
Solution Approach 1:
A reflection attenuating layer is introduced as an intermediary component between the display panel and the air gap. This layer includes a first quarter wave plate, a linear polarizer, and a second quarter wave plate arranged in sequence, which together attenuate reflected light before it reaches the sensor opening, thereby reducing dark spots while preserving display area coverage
Solution Approach 2:
The patent changes the optical parameters of the light path by introducing polarizing elements and wave plates. The first quarter wave plate converts linearly polarized light from OLEDs into circularly polarized light, the linear polarizer blocks reflected light based on polarization orientation, and the second quarter wave plate converts circularly polarized light back to linearly polarized light, thereby controlling light reflection characteristics
2Object-affected harmful factors
If a reflection attenuating layer with multiple optical components is added, then light reflection is reduced and dark spots are prevented, but device structure complexity increases
Solution Approach 1:
Multiple optical components (first quarter wave plate, linear polarizer, second quarter wave plate) are merged into a single reflection attenuating layer assembly that is integrated within the display panel structure. This consolidation achieves effective reflection attenuation while maintaining a compact and manageable structural configuration
Solution Approach 2:
The reflection attenuating layer serves multiple functions simultaneously: it attenuates reflected light to prevent dark spots, maintains display luminance characteristics, and integrates within the existing display panel architecture without requiring separate structural modifications
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
Prevents unintended dark spots by reducing light reflection, ensuring consistent OLED luminance and maintaining the display's intended appearance.
Implementation Method 1
The first quarter wave plate can include a PET film layer
Implementation Method 2
the linear polarizer is located between the first and second quarter wave plates
Implementation Method 3
the second quarter wave plate can include a partially-transmissive, partially-opaque layer
Implementation Method 4
The display panel can include an active matrix organic light emitting diode (AMOLED) display
Data Source
AI summary
A mobile computing device includes an emissive display panel configured to emit light from a front surface of the display panel, with the display panel having a plurality of transparent layers and an opaque back cover layer. The mobile computing device also includes a light sensor located behind the opaque back cover layer, and the opaque back cover layer includes an opening through which light from outside the display that is transmitted through the transparent layers of the display can pass to reach the sensor. An air gap separates the light sensor from the transparent layers of the display panel. The plurality of transparent layers includes a reflection attenuating layer on a back side of the display panel configured to attenuate the reflection of light from an interface between a transparent layer of the display panel and the air gap.