Ambient Light Estimation Using Display Color Vector Projection
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Solution Overview
Problem
Ambient light sensors positioned behind display screens struggle to accurately measure ambient light due to the inclusion of screen brightness in their readings, as they detect a sum of ambient light and screen light, necessitating a method to estimate and subtract the screen's lux contribution.
Innovation Solution
Estimating the display screen's color above the ambient light sensor and using prior information about the screen's brightness settings and color contributions to determine the ambient light by projecting measured light vectors onto known RGB vectors, thereby isolating the ambient light component from the total light measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If an ambient light sensor is positioned behind the display screen to enable automatic brightness adjustment, then the device can automatically adapt to ambient light conditions, but the sensor reading includes both ambient light and screen light making accurate ambient light measurement impossible
Solution Approach 1:
The patent segments the total light measurement into two distinct components: screen light contribution and ambient light contribution. By separately estimating the screen's lux contribution based on display parameters (brightness level, color content, backlight characteristics) and subtracting it from the total sensor reading, the system isolates the ambient light component. This segmentation enables both automatic brightness adjustment and accurate ambient light measurement to coexist.
Solution Approach 2:
The patent introduces an intermediary calculation model that estimates the screen's light contribution based on intermediate parameters such as display brightness settings, color gamut information, and backlight characteristics. This intermediary estimation acts as a bridge between the total sensor reading and the pure ambient light value, allowing the system to derive accurate ambient light measurements while maintaining automatic brightness adjustment capability.
2Device complexity
If the sensor measures total light (ambient + screen) to simplify the sensing mechanism, then the device structure remains simple, but the ambient light measurement becomes inaccurate due to screen light contamination
Solution Approach 1:
The patent maintains the simple single-sensor configuration but introduces an intermediary computational layer that estimates screen light contribution based on display parameters. This intermediary model processes the total light reading and separates the ambient component, preserving structural simplicity while achieving measurement accuracy without requiring additional sensors or complex hardware modifications.
3Measurement precision
If individual color values of the display screen are considered in the estimation process, then the accuracy of ambient light measurement is improved, but the computational complexity increases
Solution Approach 1:
The patent applies local quality by focusing computational effort on the specific color regions where the display emits light. Rather than analyzing all possible wavelengths, the system concentrates on estimating the screen's color content in the relevant spectral bands, using colorimetric data and color space transformations. This localized approach improves accuracy where it matters most while limiting computational complexity to essential color parameters.
Solution Approach 2:
The patent transforms the color analysis problem into a parameter-based estimation using color space coordinates (such as XYZ or RGB values) and chromaticity information. By changing from raw spectral analysis to parameter-based colorimetry, the system achieves accurate color-dependent lux estimation with computationally efficient mathematical operations involving color matching functions and transformation matrices.
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 provides a superior estimation of ambient light by accurately accounting for the screen's color and brightness contributions, improving the accuracy of ambient light measurements compared to methods that do not consider individual color values.
Implementation Method 1
An ambient light sensor may be positioned behind the display screen of a device. In this case, the signal picked up by the ambient light sensor is a sum of the ambient light coming from the surrounding environment and the light generated by the display screen itself.
Data Source
AI summary
A method for estimating ambient light at a display screen of a device. The method comprises determining one or more expected colour values of display screen output light, detecting light with a sensor positioned behind the display screen, determining one or more colour values of the detected light, determining a difference between the one or more expected colour values of the display screen output light and the one or more colour values of the detected light, and, from the determined difference, estimating a first portion of the detected light corresponding to the display screen output light and a second portion of the detected light corresponding to ambient light.