Under-Display Ambient Light Sensor for OLED Interference
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Solution Overview
Problem
Conventional ambient light sensors in electronic devices with OLED displays face challenges in accurately sensing ambient light due to the reduced perimeter space and interference from the OLED display's light, especially when disposed under the screen.
Innovation Solution
An ambient light sensing method where an ambient light sensor is positioned under the OLED display, utilizing specific sensing intervals and equations to differentiate between ambient light and OLED display light, allowing for accurate calculation of ambient light intensity by measuring light values during distinct brightness changes in these intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the ambient light sensor is disposed under the OLED display to achieve higher screen-to-body ratio, then the screen-to-body ratio is improved, but the measurement precision of ambient light sensing deteriorates due to interference from OLED display light
Solution Approach 1:
The patent applies periodic action by using the self-refresh characteristic of OLED displays, where pixels periodically turn on and off. The ambient light sensor measures light intensity during specific refresh periods when pixel rows are turned off, thereby separating ambient light measurement from display light interference. This periodic on-off cycle of OLED pixels enables the sensor to capture pure ambient light data at predetermined time intervals.
Solution Approach 2:
The patent implements preliminary action by measuring ambient light intensity during the blanking period before the pixel rows are turned on for display. By performing the ambient light sensing measurement in advance during the period when pixels are still off, the system captures ambient light data before display light interference occurs, ensuring accurate ambient light detection.
2Measurement precision
If the ambient light sensor is disposed in the perimeter area of the screen, then the measurement precision of ambient light sensing is improved, but the screen-to-body ratio deteriorates due to reduced perimeter space
Solution Approach 1:
The patent applies dimensionality change by moving the ambient light sensor from the traditional perimeter area (2D plane) to the area under the display (3D space). This spatial relocation allows the sensor to be positioned in the vertical dimension beneath the OLED display, effectively utilizing the space under the screen to achieve both high screen-to-body ratio and accurate ambient light sensing.
Solution Approach 2:
The patent uses periodic action by exploiting the refresh cycle of OLED displays. During specific periods when pixel rows are turned off for self-refresh, the ambient light sensor can accurately measure ambient light without interference from display emissions, enabling precise sensing despite the sensor's location under the display.
3Speed
If the ambient light sensor measures light continuously, then the responsiveness is improved, but the measurement precision deteriorates due to inclusion of OLED display light in the measurement
Solution Approach 1:
The patent applies periodic action by measuring ambient light only during specific refresh periods when pixel rows are turned off. Instead of continuous measurement, the sensor synchronizes with the OLED refresh cycle and performs discrete measurements at predetermined intervals when display light is absent, thereby maintaining responsiveness while ensuring measurement precision.
Solution Approach 2:
The patent maintains continuity of useful action by performing ambient light measurements at regular intervals synchronized with the OLED refresh rate. Although measurements are discrete rather than continuous, they occur frequently enough to maintain responsiveness while ensuring each measurement occurs during periods when display light interference is eliminated.
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 precise ambient light intensity measurement, effectively overcoming the interference from the OLED display and maintaining high accuracy even with limited space, ensuring optimal screen brightness adjustment.
Implementation Method 1
sensing light by the ambient light sensor to generate a sensing value
Data Source
AI summary
An electronic device includes an OLED display having a plurality of pixels and an ambient light sensor disposed under a first pixel of the plurality of pixels. In a first sensing interval, the ambient light sensor generates a first sensing value. The first sensing interval includes a first period and a second period. The first pixel has a first brightness in the first period and has a second brightness the second period. In a second sensing interval, which has the same time length as the first sensing interval, the ambient light sensor generates a second sensing value. The first pixel has the second brightness in the second sensing interval. The first pixel has an identical hue in the first sensing interval and the second sensing interval. The ambient light sensor acquires an ambient light intensity according to the first sensing value and the second sensing value.