Ambient Light Sensor Using Differential Signal Processing for Infrared Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS-based ambient light sensors struggle to accurately differentiate between infrared and visible light, especially under artificial lighting conditions, due to the limitations of IR blocking filters and the aesthetic requirements of portable electronic devices, which can lead to inaccurate ambient light measurements.
Innovation Solution
A light sensing device with a first filter that blocks visible light and a set of sensors, including at least a color sensor and a clear sensor, calculates ambient light intensity by taking the difference between their output signals to cancel out infrared content, allowing for more accurate visible light measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an IR blocking filter is placed in front of the sensor to reduce IR sensitivity, then the sensor's sensitivity to IR content is reduced, but visible light transmission is also reduced (no more than about 5% transmission)
Solution Approach 1:
The patent segments the light detection function into two separate sensors: a color sensor for detecting visible light and an IR sensor for detecting infrared light. This segmentation allows each sensor to be optimized for its specific function, with the color sensor having high visible light transmission and the IR sensor having high IR sensitivity, thereby resolving the contradiction between blocking IR and transmitting visible light.
Solution Approach 2:
The patent introduces an intermediary processing stage that combines the outputs of the color sensor and IR sensor to calculate the true ambient light level. The intermediary algorithm subtracts the IR sensor reading from the color sensor reading, effectively mediating between the two sensor types to eliminate IR interference while preserving visible light measurement accuracy.
2Shape
If a light transparent cover is made uniformly dark from outside for aesthetic reasons, then the front surface appears dark, but very little visible content passes through to reach the sensor (no more than about 5% transmission)
Solution Approach 1:
The patent segments the light detection function into two separate sensors: a color sensor for detecting visible light and an IR sensor for detecting infrared light. This segmentation allows each sensor to be optimized for its specific function, with the color sensor having high visible light transmission and the IR sensor having high IR sensitivity, thereby resolving the contradiction between blocking IR and transmitting visible light.
Solution Approach 2:
The patent introduces an intermediary processing stage that combines the outputs of the color sensor and IR sensor to calculate the true ambient light level. The intermediary algorithm subtracts the IR sensor reading from the color sensor reading, effectively mediating between the two sensor types to eliminate IR interference while preserving visible light measurement accuracy.
3Productivity
If CMOS-based ALS device is used to measure ambient light, then real-time measurement is provided, but the response is dominated by IR content rather than visible content leading to inaccurate measurements under artificial lighting
Solution Approach 1:
The patent segments the light detection function into two separate sensors: a color sensor for detecting visible light and an IR sensor for detecting infrared light. This segmentation allows each sensor to be optimized for its specific function, with the color sensor having high visible light transmission and the IR sensor having high IR sensitivity, thereby resolving the contradiction between blocking IR and transmitting visible light.
Solution Approach 2:
The patent introduces an intermediary processing stage that combines the outputs of the color sensor and IR sensor to calculate the true ambient light level. The intermediary algorithm subtracts the IR sensor reading from the color sensor reading, effectively mediating between the two sensor types to eliminate IR interference while preserving visible light measurement accuracy.
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 more precise ambient light level determination, improving the accuracy of brightness control and battery management in portable electronic devices by effectively isolating and measuring visible light intensity despite infrared interference.
Implementation Method 1
a first filter that blocks visible light in a light path
Implementation Method 2
a set of sensors to detect the light in the light path, after the first filter
Implementation Method 3
The calculation is based on a difference between an output signal of the first color sensor, and an output signal of the clear sensor
Data Source
AI summary
A light sensing device has a first filter to block visible light in a light path. The light sensing device also has a first color sensor and a clear sensor, to detect light in the light path after the first filter. A light intensity calculator computes a measure of the intensity of visible light in the light path, based on a difference between (a) an output signal of the first color sensor, and (b) an output signal of the clear sensor. Other embodiments are also described and claimed.