Light Sensor Crosstalk Reduction via Absorbing Material and Filter Overlap
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Solution Overview
Problem
Existing light sensors face crosstalk issues due to light leakage between neighboring photodiodes, which affects the accurate measurement of light in different wavelength ranges.
Innovation Solution
A light sensor design featuring first and second neighboring photodiodes separated by a space, with a black-colored light-absorbing material above the space and multilayer interference filters configured to pass specific wavelength ranges, where the filters' peripheral portions overlap above the absorbing material to minimize crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If neighboring photodiodes are placed close together to increase sensor density, then productivity and sensor compactness are improved, but crosstalk between photodiodes increases causing measurement precision to deteriorate
Solution Approach 1:
A light-absorbing material is introduced as an intermediary element positioned between neighboring photodiodes. This material absorbs stray light that would otherwise leak from one photodiode to another, thereby eliminating crosstalk while allowing the photodiodes to remain closely spaced for high sensor density.
Solution Approach 2:
The light-absorbing material is selectively placed only in the regions between photodiodes where crosstalk occurs, rather than uniformly across the entire sensor. This localized approach maintains high sensor density while precisely targeting and eliminating the crosstalk problem in specific areas.
2Measurement precision
If filter peripheral portions are extended to overlap above the light-absorbing material to block crosstalk, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The peripheral portions of adjacent filters are merged by extending them to overlap above the light-absorbing material. This merging creates a continuous filtering barrier that enhances wavelength separation accuracy while utilizing the existing light-absorbing material structure, thereby improving precision without proportionally increasing complexity.
3Measurement precision
If light-absorbing material is added between photodiodes to reduce crosstalk, then measurement precision is improved, but manufacturing complexity increases
Solution Approach 1:
The light-absorbing material is formed in advance during the manufacturing process, creating a prepared structure that facilitates subsequent filter deposition. This preliminary action simplifies the overall manufacturing process by establishing the crosstalk-blocking foundation before the more complex filter layers are applied.
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
The design effectively reduces crosstalk by absorbing or reflecting light outside the intended wavelength range, enhancing the accuracy of light measurement in different wavelength ranges.
Implementation Method 1
the light-absorbing material absorbs at least 50%, preferably at least 75%, or even at least 95% of the light power received for wavelengths in the range from 300 nm to 3 μm
Implementation Method 2
a first multilayer interference filter having a central portion vertically above the first photodiode and a peripheral portion at least partly resting on top of and in contact with light-absorbing said material
Data Source
AI summary
A light sensor includes first and second neighboring photodiodes that are separated from each other by a space. A light-absorbing material is positioned at a location which is vertically above the space between the neighboring photodiodes. A first multilayer interference filter includes a central portion located vertically above the first photodiode and a peripheral portion that at least partly extends to rest on top of and in contact with the light-absorbing material.