Infrared-Transparent Antireflection Coating for Display Covers
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Solution Overview
Problem
Electronic devices with transparent display cover layers face issues with unwanted visible light reflections, which obscure images and can inhibit the operation of infrared light-based components like sensors and emitters.
Innovation Solution
An infrared-transparent antireflection coating is applied to the display cover layer, comprising a stack of thin-film interference layers with alternating lower and higher refractive index layers, optimizing visible light reflection reduction while maintaining high infrared transmittance to support operations like facial recognition and depth sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an antireflection coating is applied to reduce visible light reflections, then image visibility is improved, but infrared light transmission is inhibited
Solution Approach 1:
The coating is divided into multiple discrete layers with alternating refractive indices (high-index layers like silicon nitride and low-index layers like silicon dioxide). Each layer is optimized for specific wavelength ranges, allowing the coating to segment the spectral handling - visible light reflection reduction in the 400-700nm range while maintaining infrared transmission in the 700nm-1mm range.
Solution Approach 2:
Different layers of the coating have different local optical properties (refractive indices ranging from 1.4 to 2.5) and different thicknesses (from 10nm to 200nm). The high-index layers are positioned and dimensioned to target visible light wavelengths, while the low-index layers and overall structure are configured to be transparent to infrared wavelengths, creating local quality variations that resolve the spectral conflict.
2Loss of energy
If the coating is optimized for maximum infrared transmittance, then sensor operation is improved, but visible light reflection increases
Solution Approach 1:
The coating structure incorporates可调 parameters including layer thicknesses (10-200nm), refractive index values (1.4-2.5), and layer sequences that can be dynamically optimized for different device configurations. This allows the same coating architecture to adapt to different infrared wavelengths (700nm-1mm) and visible light requirements through parameter adjustment rather than structural redesign.
Solution Approach 2:
The invention utilizes changes in material parameters (refractive index, thickness, composition ratios) to achieve spectral selectivity. By varying the refractive index from 1.4 to 2.5 across layers and adjusting thicknesses within 10-200nm ranges, the coating transforms its optical response to simultaneously minimize visible reflection (400-700nm) and maximize infrared transmission (700nm-1mm).
3Ease of manufacture
If a simple single-layer coating is used, then manufacturing complexity is reduced, but the ability to simultaneously optimize visible reflection and infrared transmission is insufficient
Solution Approach 1:
The coating employs composite material architecture combining multiple dielectric layers with different refractive indices (silicon nitride, silicon dioxide, magnesium fluoride, titanium dioxide). This composite structure enables sophisticated spectral control that cannot be achieved with single materials, while each individual layer remains manufacturable using standard deposition techniques, balancing complexity and performance.
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 coating effectively minimizes visible light reflections, allowing clear image visibility while ensuring sufficient infrared light transmission for device operations, such as facial recognition and depth sensing, with photopic reflectance below 1.5% and infrared transmittance above 94% across a wide range of wavelengths.
Implementation Method 1
The coating may include a stack of thin-film interference layers. The stack may include alternating lower and higher refractive index layers
Data Source
AI summary
An electronic device may have a display cover layer provided with an infrared-transparent antireflection coating. A pixel array may emit visible light through the cover layer and the coating. An infrared emitter may emit infrared light and an infrared sensor may receive infrared light through the coating and the cover layer. The coating may include a stack of thin-film interference layers. The stack may include alternating lower and higher refractive index layers. The layers may have thicknesses and materials that configure the coating to exhibit an infrared transmittance of greater than 94% from 920 nm to 960 nm and a photopic reflectance of less than 1.5%. The coating may reflect visible light to prevent displayed images from being obscured by visible reflections. At the same time, some photopic reflectance of the coating may be sacrificed to maximize infrared transmittance and accommodate operation by the infrared emitter and sensor.