On-Chip IR and Color Interference Filters for Light Sensors
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Solution Overview
Problem
Existing light sensors in electronic devices are influenced by infrared light, leading to inaccurate ambient lighting detection, as they typically employ external infrared blocking filters that reduce sensitivity to infrared light.
Innovation Solution
Integration of an infrared interference filter and at least one color interference filter on-chip within the light sensor, allowing the IR filter to block infrared light while passing visible light to photodetectors, and enabling clear photodetectors to detect ambient light without filtration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If external infrared blocking filters are used in light sensors, then infrared light is blocked, but sensitivity to infrared light is reduced
Solution Approach 1:
The patent combines the IR blocking filter and color pass filter into a single integrated on-chip filter structure. This merging allows the filters to work together in close proximity, enabling the IR filter to block infrared light while the color pass filter simultaneously passes specific visible wavelengths to the photodetector, resolving the contradiction between blocking IR and maintaining sensitivity
Solution Approach 2:
The color pass filter acts as an intermediary between the IR blocking filter and the photodetector. It selectively transmits desired visible light wavelengths while the IR blocking filter handles infrared rejection, creating a coordinated filtering system that maintains both IR blocking capability and infrared sensitivity for proximity detection
2Measurement precision
If infrared light is blocked from photodetectors, then ambient lighting detection accuracy improves, but proximity sensor functionality deteriorates
Solution Approach 1:
The patent segments the filtering function into two distinct components: an IR blocking filter for wavelength selection and a color pass filter for spectral refinement. This segmentation allows each filter to perform its specific function independently, enabling accurate ambient light detection while preserving proximity sensor functionality through the clear photodetector path
Solution Approach 2:
The patent applies different filtering characteristics to different photodetectors. Color-filtered photodetectors receive spectrally refined light for accurate ambient lighting detection, while clear photodetectors receive unfiltered light including infrared wavelengths for proximity sensing. This local differentiation resolves the contradiction by providing tailored optical paths for different detection functions
3Area of stationary object
If multiple filters are integrated on-chip, then device miniaturization is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple filter functions (IR blocking and color passing) into a single integrated on-chip structure. This consolidation reduces the overall sensor footprint by eliminating separate filter components and their mounting infrastructure, achieving device miniaturization while the filters are fabricated together using compatible semiconductor manufacturing processes
Solution Approach 2:
The patent employs thin-film deposition techniques to create the filters with precisely controlled optical parameters. By adjusting film thickness, composition, and layer structure during manufacturing, the filters achieve their specific spectral characteristics (IR blocking and color passing) through parameter optimization rather than complex mechanical assembly, simplifying the manufacturing process
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
Enhances the sensitivity of light sensors to infrared light and improves the accuracy of ambient lighting detection, allowing for better control of device functions like display brightness.
Implementation Method 1
An IR interference filter is disposed over the photodetectors. The IR interference filter is configured to filter infrared light from light received by the light sensor to at least substantially block infrared light from reaching the photodetectors
Implementation Method 2
At least one color interference filter is disposed above or below the IR interference filter. The color interference filter is configured to filter visible light received by the light sensor to pass light in a limited spectrum of wavelengths
Implementation Method 3
Typical light sensors employ photodetectors such as photodiodes, phototransistors, or the like, which convert received light into an electrical signal
Data Source
AI summary
A light sensor is described that includes an IR interference filter and at least one color interference filter integrated on-chip. The light sensor comprises a semiconductor device (e.g., a die) that includes a substrate. Photodetectors are disposed proximate to the surface of the substrate. An IR interference filter is disposed over the photodetectors. The IR interference filter is configured to filter infrared light from light received by the light sensor to at least substantially block infrared light from reaching the photodetectors. At least one color interference filter is disposed proximate to the IR interference filter. The color interference filter is configured to filter visible light received by the light sensor to pass light in a limited spectrum of wavelengths (e.g., light having wavelengths between a first wavelength and a second wavelength) to at least one of the photo detectors.