Optical Proximity Sensor Pixel Distortion Reduction
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Solution Overview
Problem
Optical proximity sensors located behind OLED displays can cause visible distortions due to the emission of near-infrared (NIR) light, which can pass through the display and result in pixel distortions, even on black screens.
Innovation Solution
Synchronizing the periodic illumination of the NIR light emitter with the vertical synchronization signal of the display driver, introducing a delay to align illumination with the blanking or dimming of display pixels above the sensor, thereby minimizing visual distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the proximity sensor is located behind the OLED display, then the screen-to-body ratio is improved, but visible pixel distortion occurs due to NIR light emission
Solution Approach 1:
The proximity sensor emits NIR light in periodic pulses synchronized with the display's vertical blanking interval rather than continuously. This timing-based periodic action allows the sensor to function while the display pixels are not actively emitting light, preventing visible distortion while maintaining proximity detection capability
Solution Approach 2:
The system prepares by detecting the vertical synchronization signal from the display driver in advance, then schedules the NIR light emission to occur during the upcoming blanking interval. This preliminary synchronization ensures the sensor operates at the optimal moment before the display pixels are dimmed or blanked
2Measurement precision
If NIR light is emitted continuously for proximity sensing, then sensing accuracy is maintained, but display distortion becomes visible under all conditions
Solution Approach 1:
The NIR light emitter operates in periodic pulses rather than continuous emission, synchronizing with the display's vertical blanking interval. This maintains sufficient light emission for accurate proximity sensing while ensuring the light only interacts with the display during periods when pixels are not actively emitting, eliminating visible distortion
Solution Approach 2:
The synchronization mechanism ensures the proximity sensing function continues uninterrupted by aligning the sensor's operation with the display's natural refresh cycle. The useful action of proximity detection is maintained continuously through coordinated periodic pulses rather than being interrupted by display updates
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
This approach effectively reduces or eliminates pixel distortion in OLED displays while allowing the use of NIR light for proximity sensing, even without a bezel, and avoids the need for more expensive solutions like far-infrared emitters or ultrasonic sensors.
Implementation Method 1
emitting near infra-red (NIR) light and measuring any light energy reflected back
Implementation Method 2
OLED displays may permit some light, including NIR light, to pass through the display
Implementation Method 3
obtaining a vertical synchronization signal from a display driver
Data Source
AI summary
A method of operating an optical proximity sensor of a computer device having a display, where the optical proximity sensor is located beneath or otherwise adjacent to the display. The method comprises obtaining a vertical synchronization signal from a display driver, and synchronizing periodic illumination of a light emitter of the optical proximity sensor with the vertical synchronization signal.