Sensor Blackout Pulse Control for Under-Display Sensors
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Solution Overview
Problem
In borderless electronic devices with full-face displays, sensors such as cameras and ambient light sensors placed under the display experience performance degradation due to light emitted from the display pixels being reflected back towards them, affecting their functionality.
Innovation Solution
A localized sensor blackout region is created on the display where pixels are prevented from emitting light during sensor operation, using pulse width modulation (PWM) to control the size of this region, and a pixel luminance uniformity compensation circuit adjusts luminance levels to minimize performance impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If sensors are placed under the display stack to achieve borderless display, then display area is improved, but sensor performance deteriorates due to light reflection
Solution Approach 1:
The patent divides the display into two distinct regions: a first region that emits light during normal operation and a second region that remains dark during sensor operation. This spatial segmentation allows the display to provide both full-area coverage and sensor protection simultaneously, resolving the contradiction between display area and sensor performance.
Solution Approach 2:
The patent implements periodic switching between display modes: during normal operation the display emits light, and during sensor operation a second region is activated to block light. This temporal periodic action allows the system to alternate between maximizing display area and protecting sensor performance based on operational requirements.
2Measurement precision
If a blackout region is created to protect sensor performance, then sensor accuracy is improved, but display luminance uniformity deteriorates
Solution Approach 1:
The patent applies local quality by creating a specific second region with different optical properties (dark state) compared to the first region (light-emitting state). This localized modification affects only the necessary area for sensor protection while preserving luminance uniformity in the remaining display area, thus resolving the contradiction between sensor accuracy and overall display uniformity.
3Object-affected harmful factors
If PWM blanking pulses are used to control light emission, then light reflection to sensors is reduced, but display brightness control complexity increases
Solution Approach 1:
The patent applies preliminary action by proactively generating PWM blanking pulses and sensor blackout pulses in advance to create the dark second region before sensor measurement begins. This pre-planned light emission control prevents light reflection to sensors during critical measurement periods while maintaining systematic control over display brightness, resolving the contradiction between reducing harmful light reflection and managing control complexity.
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 solution significantly reduces unwanted light emission towards sensors, enhancing their performance by maintaining display brightness and uniformity, thereby improving sensor accuracy and functionality.
Implementation Method 1
each pixel includes a light-emitting diode and thin-film transistors for controlling application of a signal to the light-emitting diode to produce light
Data Source
AI summary
An electronic device may include a display and a sensor under the display. The display may include pixels having emission transistors that are controlled by emission signals. The emission signals are controlled using a pulse width modulation (PWM) scheme to control the brightness of the display. The emission signals may further include a localized sensor blackout pulse configured to generate a localized sensor blackout region that overlaps with the sensor to reduce any undesired back emission of light emitted from the display. The sensor blackout pulse may be automatically generated periodically or generated in an on-demand basis once per frame, multiple times per frame time, or once every multiple frames. Any luminance degradation caused by the sensor blackout pulse may be compensated by boosting the luminance and/or by extending the duration of each emission on pulse.