Under-display sensor light selection layer optical path design
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Solution Overview
Problem
The integration of an illuminance sensor into electronic devices with full-front display designs is challenging due to the difficulty in securing a position for the sensor, as existing solutions either obstruct ambient light detection or are difficult to integrate under the display.
Innovation Solution
An under-display sensor system that includes a light selection layer with distinct optical paths for circularly-polarized and unpolarized light, utilizing a combination of retardation and polarization layers to differentiate and measure ambient light, allowing for accurate brightness detection even when the display occupies the entire front surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a commercially-available proximity-illuminance sensor is placed on the front surface, then ambient light can be detected, but the display cannot occupy the entire front surface
Solution Approach 1:
The sensor is relocated from the front surface to the rear surface of the display, utilizing the z-dimension (depth) rather than the x-y plane. This allows the display to occupy the entire front surface while the sensor operates from the rear, detecting light that passes through the display structure.
Solution Approach 2:
A light guide layer is introduced as an intermediary component between the ambient light source and the sensor. This light guide layer captures and redirects light toward the sensor, enabling effective detection even when the sensor is positioned on the rear surface rather than directly exposed to ambient light.
2Area of stationary object
If the illuminance sensor is located in an area other than the front surface, then the display can occupy the entire front, but ambient light detection may be blocked by the case
Solution Approach 1:
The light guide layer serves as a mediator that captures ambient light from available angles and redirects it to the sensor, bypassing the obstruction caused by the case. This intermediary structure enables light detection even when the sensor is shielded from direct ambient light exposure.
Solution Approach 2:
The light guide layer is implemented as a thin film structure that can be integrated into the display assembly without adding significant bulk. This thin film approach allows light to be guided effectively while maintaining a sleek device profile and avoiding interference from the protective case.
3Area of stationary object
If a light guide layer and sensor are used to detect ambient light from the rear, then the display can occupy the entire front, but the sensor must differentiate between display light and ambient light
Solution Approach 1:
Different regions of the light guide layer are designed with different optical properties. Specifically, certain areas have enhanced light-guiding capabilities that preferentially direct ambient light to the sensor while minimizing display light transmission, enabling spatial differentiation of light sources through localized optical design.
Solution Approach 2:
The optical parameters of the light guide layer are optimized to differentiate between display light and ambient light. By controlling refractive indices, thickness, and patterning of the light guide layer, the system creates distinct optical paths that allow the sensor to distinguish and measure ambient light separately from display-emitted light.
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
Enables effective ambient light measurement and color temperature calculation, providing accurate data for display and camera adjustments without obstructing the display's visibility or requiring additional space.
Implementation Method 1
a light selection layer, having a first optical path and a second optical path through which a display circularly-polarized light generated by an ambient light and an unpolarized light generated by a pixel pass
Implementation Method 2
the first optical path passes all of the display circularly-polarized light and the unpolarized light, wherein the second optical path blocks the display circularly-polarized light and passes the unpolarized light
Implementation Method 3
an optical sensor, having a first receiver configured for measuring light that has passed the first optical path and a second receiver configured for measuring light that has passed the second optical path
Data Source
AI summary
Under-display sensor disclosed. The under-display sensor includes a light selection layer, having a first optical path and a second optical path through which a display circularly-polarized light generated by an ambient light and an unpolarized light generated by a pixel pass, and an optical sensor, having a first receiver configured for measuring light that has passed the first optical path and a second receiver configured for measuring light that has passed the second optical path, wherein the first optical path passes all of the display circularly-polarized light and the unpolarized light, wherein the second optical path blocks the display circularly-polarized light and passes the unpolarized light.