Image Sensor Dark Pixel Noise Correction Architecture
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Solution Overview
Problem
Existing image sensors face challenges in efficiently utilizing space while effectively correcting for pixel noise, as dark pixels are necessary for noise correction but occupy valuable area.
Innovation Solution
Incorporating a minimal number of dark pixels, either in a single row or multiple rows, that are shielded from light to generate noise reference levels, which can be used to correct for noise across all imaging pixels, thereby reducing the overall space required for noise correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dark pixels are added to correct pixel noise, then noise correction capability is improved, but sensor area is reduced
Solution Approach 1:
The patent combines multiple functions into the same pixel structure: imaging pixels perform both noise generation (when shielded) and light detection (when unshielded), while dark pixels serve dual purposes as both reference pixels and potential imaging pixels. This merging eliminates the need for separate dedicated dark pixel arrays, thereby improving noise correction capability without proportionally reducing sensor area.
Solution Approach 2:
The patent introduces dynamic control through selectable shielding mechanisms that can switch between shielded and unshielded states. Pixels can dynamically change their function between imaging and dark pixel modes based on operational requirements, allowing the sensor to adapt its configuration and reduce the permanent area dedicated to dark pixels while maintaining noise correction capability.
2Measurement precision
If more dark pixels are used for accurate noise correction, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses a minimal number of dark pixels (e.g., one per column or a small dedicated array) rather than requiring dark pixels for every row and column. This partial action approach provides sufficient noise correction accuracy for practical applications while avoiding the excessive complexity that would result from comprehensive dark pixel coverage across the entire sensor array.
Solution Approach 2:
The patent makes pixels universal by enabling them to serve multiple functions: imaging pixels can function as dark pixels when shielded, and dark pixels can contribute to imaging when unshielded. This multi-functionality reduces the need for specialized dedicated dark pixel structures, thereby improving noise correction accuracy without proportionally increasing device complexity.
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 allows for accurate noise correction with a reduced number of dark pixels, minimizing space usage and improving the efficiency of image sensor design.
Implementation Method 1
Typical image pixels contain a photodiode for generating charge in response to incident light
Implementation Method 2
The dark pixels may include photodiodes that are shielded to prevent the dark pixel photodiodes from being exposed to incident light
Data Source
AI summary
An imaging sensor may include an array of imaging pixels and at least two rows of dark pixels. Each imaging pixel may include a photodiode that generates charge in response to incident light. Each dark pixel may include a photodiode that is shielded from incident light by shielding material. The at least two rows of dark pixels may be sampled simultaneously and averaged to obtain an average dark pixel charge level. The average dark pixel charge level may be subtracted from each imaging pixel charge level to correct the imaging pixel charge levels for noise. Each column of dark pixels may include a column line that is coupled to first and second readout circuits. Each column line may be coupled to first and second current sources. Each column line may be coupled to at least one capacitor.