Ambient Light Sensor Spectral Decomposition for Display Interference
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Solution Overview
Problem
Ambient light sensors placed behind smartphone screens face distorted readings due to on-screen content, particularly white displays that increase light hitting the sensor, leading to overestimation of ambient lux levels.
Innovation Solution
The method involves spectral decomposition of raw light measurements into independent sources, such as red, green, and blue components of an OLED display, and using reference data to adjust measurements, allowing for accurate ambient light determination independent of screen content. This is achieved through an electronic control unit that processes data from multiple optical channels and subtracts the display's spectral power distribution from the collected spectral response data to generate a more accurate ambient light measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the ambient light sensor is placed behind the display screen to maximize screen area, then the screen to body ratio is improved, but the measurement precision deteriorates due to distorted readings from on-screen content
Solution Approach 1:
The patent segments the spectral response data into distinct components by separating the display light contribution from the ambient light contribution. By dividing the measurement into spectral channels and identifying which channels are affected by display content versus ambient light, the system can independently process each component to achieve accurate ambient light measurement despite the sensor's location behind the screen.
Solution Approach 2:
The patent introduces spectral decomposition as an intermediary processing step between the raw sensor data and the final ambient light measurement. This intermediary technique mathematically separates the display light interference from the ambient light signal, allowing the system to eliminate the distorting effect of on-screen content while preserving the accurate ambient light measurement.
2Measurement precision
If spectral decomposition is applied to separate display components from ambient light, then the measurement precision is improved, but the device complexity increases due to additional processing requirements
Solution Approach 1:
The patent performs preliminary characterization of the display screen's spectral response by measuring and storing reference data for the display's red, green, and blue components. This preliminary action allows the complex spectral decomposition to be performed using pre-computed reference values rather than requiring complex real-time analysis, reducing the computational burden during actual measurements.
Solution Approach 2:
The patent transforms the measurement problem by changing from a single intensity parameter to multiple spectral parameters across different wavelength channels. By expressing both the display light and ambient light in terms of their spectral distributions across multiple channels, the system can use linear algebra operations to separate the components, making the complex separation problem more manageable through parameter transformation.
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 enables precise ambient light measurement and identification of light sources, allowing for appropriate adjustments to screen settings or camera functions, thereby improving the accuracy of ambient light detection and utilization in smartphone devices.
Implementation Method 1
an ambient light sensor disposed behind a display screen and operable to sense light
Implementation Method 2
Each of the eleven optical channels may be configured to filter light for a specific portion of the visible light spectrum
Data Source
AI summary
The present disclosure describes a method and apparatus that can be used to adjust for distorted ambient light readings caused by the ambient light sensor being located behind the display screen. The strategy of the disclosure relies, at least in part, on spectral decomposition of ambient light measurements into independent sources (e.g., red, green, and blue display components of an Organic Light Emitting Diode (“OLED”) display screen and ambient light). Following the spectral decomposition technique, a more accurate ambient light measurement can be obtained in some instances. This technique enables determinations such as ambient lux and correlated color temperature independent of the content displayed on the screen.