Ambient Light Sensor Accuracy via Screen Luminance Control
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Solution Overview
Problem
Ambient light sensors in terminals, such as mobile phones and wearable devices, face inaccuracies in detecting luminance changes due to internal light interference from the screen, especially when moving from bright to dark environments.
Innovation Solution
The terminal adjusts the screen luminance to a value below a threshold within the visual persistence time of human eyes, ensuring that the ambient light sensor detects only external luminance, and uses image data adjustments to minimize internal light interference, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the ambient light sensor detects luminance using transmitted light through the display screen, then the sensor can be positioned below the screen for compact design, but the detection accuracy deteriorates due to internal light interference from the screen
Solution Approach 1:
The system performs preliminary action by temporarily dimming the screen to a luminance below threshold before the ambient light sensor takes measurement. This preparatory step eliminates internal light interference from the display screen, ensuring the sensor detects only external ambient light. After measurement, the screen luminance is restored to its original state.
Solution Approach 2:
The invention changes the luminance parameter of the screen dynamically. The screen luminance is adjusted from its normal operating level to a low level (below threshold) during the measurement window, and then restored. This parameter change allows the ambient light sensor to operate accurately by eliminating the confounding variable of screen-emitted light.
2Measurement precision
If the screen luminance is reduced to improve ambient light detection accuracy, then measurement precision improves, but user visual comfort deteriorates due to screen visibility
Solution Approach 1:
The system employs periodic action by temporarily dimming the screen only during brief measurement intervals when the ambient light sensor is active. The screen luminance is restored immediately after measurement. This periodic dimming-duration-restoring cycle ensures that the screen remains visible to users for the majority of the time while periodically enabling accurate ambient light detection.
Solution Approach 2:
The screen luminance is preliminarily adjusted to a low level before the ambient light sensor performs measurement, and then restored to normal after measurement. This preliminary adjustment ensures that during the measurement window, the screen does not interfere with detection, while the quick restoration maintains user visual comfort.
3Speed
If the ambient light sensor operates continuously to track ambient light changes, then responsiveness to environmental changes improves, but energy consumption increases
Solution Approach 1:
The ambient light sensor operates periodically rather than continuously. The sensor is activated at specific intervals to measure ambient light luminance, and remains inactive between measurements. This periodic operation mode maintains the system's ability to detect ambient light changes while significantly reducing energy consumption compared to continuous operation.
Solution Approach 2:
The system intelligently determines when ambient light measurement is necessary and activates the sensor only at those moments. The processor controls the sensor operation based on system needs, enabling the sensor to serve itself by operating only when required rather than continuously, thus optimizing energy efficiency.
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 method enhances the accuracy of ambient light detection, reducing errors and improving user comfort by accurately reflecting ambient light changes on the screen.
Implementation Method 1
detects an ambient light change using transmitted light
Implementation Method 2
backlight, or light that is obtained after a light ray of the screen is reflected on a surface of the screen
Implementation Method 3
within a visual persistence time of human eyes
Data Source
AI summary
A terminal and a method for detecting luminance of ambient light, where the terminal includes a processor, an ambient light sensor, and a screen. The ambient light sensor and the screen are both coupled to the processor. A light-sensitive element of the ambient light sensor faces the screen and is located on a lower surface of the screen. After the screen is lit up, the processor adjusts first luminance of the screen to a value below a first threshold within a visual persistence time of human eyes. The ambient light sensor detects luminance of first ambient light of the terminal within the visual persistence time of human eyes. The terminal may eliminate non-ambient light that enters the ambient light sensor such that the ambient light sensor may detect luminance of relatively real ambient light.