Pixel Array Readout Circuit With Grouped ADC References
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Solution Overview
Problem
Known pixel array read-out circuits suffer from crosstalk issues due to shared reference signals among analog-to-digital converters, leading to artifacts such as smearing and line noise in images, which result in undesirable bands and noise patterns.
Innovation Solution
Organizing analog-to-digital converters into groups with distinct reference signals and using buffer circuits to provide identical reference signals to each group, decoupling them from other groups to prevent signal interference, and employing follower amplifiers to manage impedance and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If all analog-to-digital converters share a common reference signal, then device complexity is reduced, but crosstalk and noise artifacts increase
Solution Approach 1:
The patent divides the analog-to-digital converters into K groups, where each group receives a dedicated reference signal from its own buffer circuit. This segmentation isolates the reference signal paths, preventing crosstalk between groups while maintaining manageable complexity through systematic organization.
Solution Approach 2:
Buffer circuits are introduced as intermediary components between the reference signal source and each group of analog-to-digital converters. These buffers act as mediators that provide impedance matching and electrical isolation, ensuring clean reference signal distribution without direct interference between converter groups.
2Object-generated harmful factors
If buffer circuits are added to provide isolated reference signals to each group, then crosstalk is reduced, but device complexity increases
Solution Approach 1:
Multiple analog-to-digital converters within each group share a common reference signal from a single buffer circuit. This merging approach reduces the total number of buffer circuits needed compared to providing entirely separate reference signals to each converter, while still achieving crosstalk reduction through group-level isolation.
Solution Approach 2:
The patent applies different reference signal configurations to different groups of converters based on their specific requirements. Each group can be optimized independently with appropriate buffer circuit design, allowing localized quality improvements without uniformly increasing complexity across the entire system.
3Object-generated harmful factors
If more groups are created with fewer converters per group, then crosstalk is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the number of groups K and the number of converters per group P by adjusting key parameters such as signal amplitude, impedance values, and buffer circuit characteristics. This allows the system to achieve acceptable crosstalk reduction while maintaining relaxed manufacturing tolerances through parameter optimization rather than extreme segmentation.
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 reduces crosstalk, minimizing smear effects and column noise, resulting in improved image quality with reduced artifacts and noise patterns.
Implementation Method 1
employing follower amplifiers to manage impedance and reduce noise
Data Source
AI summary
The present disclosure relates to a read-out circuit comprising N inputs configured to be connected to N respective outputs of a pixel array of an image sensor, with N being an integer strictly greater than 1; and N analog-to-digital converters organized in K groups, with K being an integer strictly greater than 1 and strictly less than N, and each having a first input coupled to a respective one of the N inputs and a second input. In each group, the second inputs of the analog-to-digital converters of the group are connected together, electrically decoupled from the second inputs of the analog-to-digital converters of the other groups, and configured to receive a first reference signal that is identical for all the analog-to-digital converters of the group.