Under-Display Ambient Light Sensing With Crosstalk Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ambient light sensors in electronic displays are affected by crosstalk from light emitted by display pixels, leading to inaccurate measurements of ambient light due to residual emissions during blanking periods, especially in rapidly changing environments.
Innovation Solution
Implementing crosstalk compensation techniques that utilize fast sensing integration during emission blanking periods and calculating an emission-off scale factor based on transient behaviors of display pixels to compensate for ambient light sensor measurements, using interpolation for different pixel lines and brightness levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the ambient light sensor is located near the display pixels to enable compact device design, then the device structure is simplified and space is saved, but the sensor detects light emitted from the display itself causing measurement errors
Solution Approach 1:
The patent segments the sensing process into distinct time windows: active emission periods when display pixels are emitting light, and blanking periods when pixels are off. By integrating sensor measurements only during blanking periods, the system separates the desired ambient light detection from the harmful display back-emission, resolving the contradiction between compact placement and measurement accuracy.
2Measurement precision
If the ambient light sensor integrates measurements over longer periods to improve signal accuracy, then measurement precision improves, but the sensor captures residual light emission from display pixels during what should be blanking periods
Solution Approach 1:
The patent implements periodic sensing integration synchronized with the display's emission pattern. The sensor integrates measurements during periodic blanking periods when display pixels are off, rather than using continuous or long-period integration. This periodic approach maintains measurement precision while eliminating capture of residual light emission, as the integration window is precisely timed to coincide with when no display emission occurs.
3Productivity
If the display refreshes rapidly to accommodate dynamic image content, then image quality and responsiveness improve, but the ambient light sensor has insufficient time to complete accurate measurements during blanking periods
Solution Approach 1:
The patent implements a dynamic sensing integration approach where the integration period and timing are adaptively adjusted based on the display's current refresh rate and emission pattern. Rather than using a fixed integration window, the system dynamically synchronizes the sensing integration to match the actual blanking periods at varying refresh rates, ensuring accurate measurements are completed even when the display refreshes rapidly to accommodate dynamic image content.
4Device complexity
If the ambient light sensor is placed close to the display to reduce device size, then manufacturing complexity is reduced, but crosstalk between display emission and sensor detection increases
Solution Approach 1:
The patent extracts the harmful display back-emission component from the sensor measurements by temporally separating the sensing process from the emission process. By integrating measurements only during blanking periods when display pixels are off, the system removes the crosstalk component from the measurement equation, allowing the sensor to be placed close to the display without suffering from emission interference. This extraction approach simplifies the overall device design while maintaining measurement accuracy.
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
Substantially reduces display crosstalk and improves ambient light sensing accuracy by minimizing back-emission interference, accommodating dynamic image content, and ensuring consistent display adjustments across varying lighting conditions.
Implementation Method 1
An ALS senses ambient light and allows the brightness and/or color of the electronic display to be adjusted. The light emitted from the display is not ambient light and could cause the ALS to incorrectly measure the ambient light
Data Source
AI summary
An electronic display includes an ambient light sensor (ALS) located beneath an active area to sense ambient light above the active area. The ALS is synchronized with blanking periods of a display pixel on the active area. An emission-off scale factor is calculated based on an emission profile of the display pixel when the display pixel is turned off. The emission-off scale factor is used with display content to calculate a crosstalk compensation for the ALS.