Radiation Sensor with Dual Pixel Filters for Proximity and Light Sensing
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Solution Overview
Problem
Current ambient light and proximity sensors require separate chips and sensor windows, leading to increased footprint and cost in mobile devices, as existing materials are not suitable for integrating both functions on a single chip with different spectral responses.
Innovation Solution
A radiation sensor with first and second pixels, where the first pixel has a radiation absorption filter and an interference filter, allowing the second pixel to detect radiation within specific pass-bands, enabling combined proximity and ambient light sensing on a single chip by subtracting signals from both pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate ambient light and proximity sensors are used, then each sensor can be optimized for its specific function, but the combined footprint and number of sensor windows increase
Solution Approach 1:
The patent combines ambient light sensing and proximity sensing functions into a single radiation sensor chip. The chip includes first pixels with both radiation absorption filter and interference filter for proximity sensing, and second pixels with only interference filter for ambient light sensing. This merging eliminates the need for separate sensor chips and reduces the combined footprint while maintaining optimized spectral response for both functions through carefully designed filter combinations.
2Area of stationary object
If a single chip is used for both ambient light and proximity sensing, then footprint is reduced, but achieving different spectral responses requires complex filter materials that are not currently suitable
Solution Approach 1:
The patent employs composite filtering approaches where different pixel types combine different filter materials to achieve the required spectral responses. First pixels use both radiation absorption filter (for infrared transmission) and interference filter (for visible light blocking), while second pixels use only interference filter. This composite material strategy enables a single chip to provide both ambient light and proximity sensing with optimized spectral characteristics without requiring a single complex material to perform all functions.
3Measurement precision
If pixels detect broad spectral ranges, then sensitivity to ambient light is improved, but saturation occurs in high ambient light conditions
Solution Approach 1:
The patent applies different spectral filtering characteristics to different pixel groups on the same chip. First pixels are configured with both radiation absorption filter and interference filter to detect reflected infrared radiation for proximity sensing while blocking visible ambient light. Second pixels use only interference filter to detect visible ambient light for ambient light sensing. This local differentiation of spectral response properties allows each pixel type to operate within its optimal range without saturation from unwanted spectral components.
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 solution reduces the combined footprint of sensors, improves sensitivity, and prevents saturation in high ambient light conditions, allowing for accurate ambient light and proximity sensing with a single sensor chip and window, optimizing device design and functionality.
Implementation Method 1
a radiation absorption filter positioned over the first pixel, the combined spectral response of the absorption filter and the first pixel having a first pixel pass-band and a first pixel stop-band
Implementation Method 2
an interference filter positioned over both the first and second pixels, the interference filter having a first interference filter pass-band substantially within the first pixel pass-band and a second interference filter pass-band substantially within the first pixel stop-band
Data Source
AI summary
A radiation sensor includes first and second pixels with a radiation absorption filter positioned over the first pixel and an interference filter positioned over both the first and second pixels. The combined spectral response of the absorption filter and the first pixel has a first pixel pass-band and a first pixel stop-band. The interference filter has a first interference filter pass-band substantially within the first pixel pass-band and a second interference filter pass-band substantially within the first pixel stop-band.