Ambient Light Sensor Infrared Compensation
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Solution Overview
Problem
Conventional ambient light sensors using silicon photosensors face challenges in accurately matching the infrared sensitivity of multiple sensors, leading to erroneous visible light readings due to mismatched performance, which complicates the adjustment of display brightness in electronic devices.
Innovation Solution
The implementation of an electronic device with silicon-based photosensors that can measure total ambient light and generate raw sensor outputs, using control circuitry to identify the lighting type by computing signal ratios, color temperature, or modulation frequency, and applying compensation factors from a lookup table to output a visible light reading representative of the ambient light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ambient light sensors use multiple silicon photosensors to detect visible and infrared light, then the display brightness can be adjusted based on ambient light levels, but mismatch in infrared sensitivity between sensors causes erroneous visible light readings
Solution Approach 1:
The patent extracts and removes the infrared light component from the sensor output by using an infrared filter on one of the photosensors. This allows the system to eliminate the harmful infrared interference rather than trying to match the infrared sensitivity of multiple sensors, directly resolving the manufacturing precision issue while maintaining reading accuracy
Solution Approach 2:
The patent introduces an infrared filter as an intermediary element between the photosensor and the ambient light. This filter selectively blocks infrared wavelengths while allowing visible light to pass through, enabling accurate visible light measurement without requiring precise matching of infrared sensitivity across multiple sensors
2Measurement precision
If ambient light sensors compensate for infrared light using multiple photosensors, then visible light measurement accuracy can be improved, but the device complexity increases
Solution Approach 1:
The patent extracts only the necessary visible light information by filtering out infrared light at the sensor level. This eliminates the need for complex multi-sensor arrangements and software-based infrared subtraction, reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent replaces the mechanical/system-level complexity of using multiple photosensors with optical filtering at the sensor level. By using an infrared filter, the system achieves infrared compensation through a simple optical element rather than complex multi-sensor mechanics and processing
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 enhances the accuracy of visible light readings by compensating for infrared content, ensuring display brightness adjustments are based on actual visible light levels, thereby improving the reliability of ambient light sensing in diverse lighting environments.
Implementation Method 1
at least one silicon-based photosensor that can be used to measure a total ambient light level and to generate a corresponding raw sensor output
Data Source
AI summary
An electronic device may have a display with a brightness that is adjusted based on ambient light data from one or more ambient light sensors. An ambient light sensor may include at least one silicon-based photosensor. The silicon-based photosensor may generate a corresponding raw sensor reading. Processing circuitry associated with the ambient light sensor may analyze the raw sensor reading to determine the type of light source that is present by comparing measurements from at least two different photosensors, by determining the color temperature of the light source, and/or by determining the modulation frequency of the light source. A compensation factor may then be selected by referring to a lookup table. The processing circuitry may compute a compensated sensor reading based on the raw sensor reading and the selected compensation factor. The brightness of the display may be adjusted based on the compensated sensor reading computed in this way.