Under-Display Light Sensor Wavelength Switching for Screen Protection
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Solution Overview
Problem
Current light sensors installed behind display screens can cause irreversible damage and imaging interference when the screen is on due to the use of specific infrared light wavelengths, and they lack sensitivity when the screen is off.
Innovation Solution
A light sensor system with two light-emitting units and two light-sensing units, where the control circuit activates a first light-emitting unit with a longer wavelength (1000-1600 nm) when the screen is on and a second unit with a shorter wavelength (850-1000 nm) when the screen is off, allowing for safe operation and improved sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single wavelength light-emitting unit (850-1000 nm infrared) is used for distance measurement, then sensitivity for distance measurement is improved, but the display screen may suffer from imaging interference (bright spots) and irreversible damage when the screen is on
Solution Approach 1:
The light-emitting unit is segmented into multiple light-emitting diodes with different wavelengths (first light-emitting diode with 850-1000 nm infrared wavelength, second light-emitting diode with visible light wavelength). This segmentation allows selective activation of appropriate wavelengths based on screen status, resolving the contradiction between measurement sensitivity and screen safety.
Solution Approach 2:
The system dynamically selects which light-emitting diode to activate based on the screen status (on or off). When the screen is off, the first light-emitting diode (850-1000 nm) is activated for high sensitivity distance measurement. When the screen is on, the second light-emitting diode (visible wavelength) is activated to avoid screen damage and imaging interference. This dynamic adaptation resolves the contradiction.
2Area of stationary object
If the light sensor is installed behind the display screen (under-display design), then the full-screen design is achieved without compressing display space, but the light may impact screen imaging and cause damage when screen is on
Solution Approach 1:
The system changes the wavelength parameter of the emitted light based on screen status. When the screen is on, visible light wavelength (second light-emitting diode) is used which does not interfere with screen imaging. When the screen is off, infrared wavelength (first light-emitting diode) is used for optimal distance measurement sensitivity. This parameter change resolves the contradiction between under-display installation benefits and screen protection.
3Object-affected harmful factors
If a longer wavelength light (1000-1600 nm) is used when screen is on, then screen safety is improved, but distance measurement sensitivity may be reduced compared to shorter wavelength
Solution Approach 1:
The system dynamically switches between different light-emitting diodes based on screen status. When the screen is on, the second light-emitting diode (visible wavelength) is activated to protect the screen. When the screen is off, the first light-emitting diode (850-1000 nm infrared) is activated for optimal sensitivity. This dynamic switching resolves the contradiction by applying the appropriate wavelength for each operational context.
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
Prevents damage to the display screen while maintaining sensitivity for distance measurement by using appropriate wavelengths based on screen status, ensuring effective operation without interfering with screen imaging.
Implementation Method 1
a first light-emitting unit and a second light-emitting unit... The light wavelength of first light-emitting unit is longer that the second light-emitting unit... While the display screen of an electronic device is at screen-on status, the control circuit activates the first light-emitting unit
Implementation Method 2
measure the distance between it and the object via the intensity of reflective light
Data Source
AI summary
A light sensor and control method thereof, which controls the light sensor comprising a first light emitted element, a second light emitted element, a first light sensing element and a control circuit. The light wavelength of the second light emitted element is greater than the light wavelength of the first light emitted element. The control circuit is coupled to the first and second light elements and the first light sensing element. When the display of an electronic device is in a light-up status, the control circuit switches on the first light emitted element to emit light; when the display of the electronic device is in a light-off status, the control circuit switches on the second light emitted element to emit light. Thus, it will prevent from the influence to the image of the display, and obtained the better sensing ability.