Image Sensor Light Filters for IR Sensitivity and Crosstalk
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Solution Overview
Problem
Image sensors face challenges in accurately sensing infrared light due to interference from other wavelengths and insufficient IR irradiation, limiting their accuracy and applicability.
Innovation Solution
The implementation of image sensors with cell deep trench isolation (CDTI) microstructures and layered light filters, including color bandpass and band-select filters, to enhance infrared light sensitivity and reduce inter-channel crosstalk, thereby improving quantum efficiency and channel separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixels are optimized to respond primarily to IR light, then IR sensitivity is improved, but response to other wavelengths increases causing interference
Solution Approach 1:
The patent divides the light filtering function into multiple segments: a color filter layer with individual filters for each pixel type (including IR-pass filters for IR pixels), and a separate light filter layer with wavelength-selective filters. This segmentation allows each layer to handle specific wavelength ranges, improving IR sensitivity while blocking unwanted wavelengths through coordinated action of multiple specialized filters.
Solution Approach 2:
The patent applies different filter characteristics to different pixel locations. IR pixels are equipped with IR-pass color filters and specific light filters optimized for their wavelength range, while visible light pixels have corresponding visible-optimized filters. This local customization ensures each pixel type responds optimally to its target wavelength while rejecting others, resolving the interference problem.
2Measurement precision
If CDTI microstructures are added to direct light toward IR photodiodes, then quantum efficiency is improved, but inter-channel crosstalk increases
Solution Approach 1:
The patent introduces wavelength-selective light filters as intermediary elements between the CDTI microstructures and the photodiodes. These filters are positioned in the light path to selectively transmit desired wavelengths to IR pixels while blocking wavelengths intended for visible light pixels. This intermediary filtering prevents crosstalk while preserving the light-directing benefits of CDTI structures.
Solution Approach 2:
The patent adds a spectral dimension to the light control by introducing the light filter layer with wavelength-selective filters. This creates a two-dimensional control system: the CDTI microstructures control the spatial/directional dimension by directing light toward photodiodes, while the light filters control the spectral dimension by selecting wavelengths. Together, they resolve both quantum efficiency and crosstalk requirements.
3Measurement precision
If multiple filter layers are implemented, then channel separation is improved, but device complexity increases
Solution Approach 1:
The patent designs the dual-layer filter system to serve multiple functions simultaneously: the color filter layer provides both color selection and initial wavelength filtering, while the light filter layer provides fine wavelength selection and IR-specific filtering. This multi-functionality achieves superior channel separation without requiring additional specialized components, thereby managing complexity while maintaining high precision.
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 configuration significantly increases the quantum efficiency of infrared channels, enhances light capture, and reduces crosstalk, leading to improved sensitivity and accuracy in infrared light detection.
Implementation Method 1
The implementation of image sensors with cell deep trench isolation (CDTI) microstructures and layered light filters, including color bandpass and band-select filters
Implementation Method 2
When IR light is emitted toward and reflected from an object, an IR sensor registers the reflected light
Implementation Method 3
cell deep trench isolation (CDTI) microstructures... to enhance infrared light sensitivity
Implementation Method 4
enhance light capture... significantly increases the quantum efficiency of infrared channels
Implementation Method 5
an IR sensor registers the reflected light... pixels may not receive sufficient IR irradiation to provide a meaningful reading
Data Source
AI summary
Light control for improved near infrared sensitivity and channel separation for an image sensor. In one embodiment, an image sensor includes: a plurality of photodiodes arranged in rows and columns of a pixel array; and a light filter layer having a plurality of light filters configured over the plurality of photodiodes. The light filter layer has a first side facing the plurality of photodiodes and a second side facing away from the first side. The image sensor also includes a color filter layer having a plurality of color filters configured over the plurality of photodiodes. The color filter layer has a first surface facing the second side of the light filter layer and a second surface facing away from the first layer. Individual micro-lenses are configured to direct incoming light through corresponding light filter and color filter onto the respective photodiode.