CMOS Pixel Layout for Uniform Noise Distribution
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Solution Overview
Problem
CMOS image sensors experience image distortion and noise issues due to uneven exposure periods and noise components like smear noise, which are challenging to eliminate with existing technologies, especially in moving-image taking operations.
Innovation Solution
A pixel internal layout structure is proposed where the opto-electric conversion section and electric-charge holding section are alternately laid out in each pixel column, with the electric-charge holding sections disproportionately positioned towards one side of the scan direction, and a scan driving section controls the transfer of electric charge from the opto-electric conversion section to the electric-charge holding section simultaneously across all unit pixels, optimizing the electric-charge accumulation period to reduce noise components uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the opto-electric conversion section and electric-charge holding section are laid out alternately in each pixel column, then noise components such as smear noise are reduced, but the device complexity increases due to the specific layout requirements
Solution Approach 1:
The pixel array is divided into multiple pixel columns, with each column containing alternately arranged opto-electric conversion sections and electric-charge holding sections. This segmentation allows independent optimization of each column's layout to reduce smear noise while maintaining overall system manageability.
Solution Approach 2:
Electric-charge holding sections are disproportionately positioned toward one side of the scan direction within each pixel column, creating an asymmetric layout. This asymmetric arrangement optimizes the reduction of inclined light components and smear noise by positioning holding sections away from the primary light incidence direction.
2Stability of the object's composition
If the scan driving section controls the transfer of electric charge simultaneously across all unit pixels, then exposure uniformity is improved, but the device complexity increases due to simultaneous control requirements
Solution Approach 1:
The scan driving section employs periodic control signals to transfer electric charge from opto-electric conversion sections to electric-charge holding sections in a systematic sequence. This periodic action ensures that all pixels within a column are exposed uniformly while maintaining manageable control complexity through regular timing patterns.
3Object-affected harmful factors
If the electric-charge holding sections are disproportionately positioned towards one side of the scan direction, then noise accumulation is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
Electric-charge holding sections are deliberately positioned asymmetrically toward one side of the scan direction within each pixel column. This asymmetric positioning creates greater distance between holding sections and the primary light incidence path, effectively reducing noise accumulation from inclined light components while establishing clear manufacturing positioning targets.
4Object-affected harmful factors
If the opto-electric conversion section and electric-charge holding section are alternately laid out, then the impact of inclined light components is minimized, but the area of each pixel increases
Solution Approach 1:
Each pixel column is segmented into multiple units, with opto-electric conversion sections and electric-charge holding sections alternating within each unit. This segmentation allows compact arrangement of functional elements, minimizing the overall pixel area while maintaining the benefits of alternate layout for reducing inclined light impact.
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 effectively eliminates noise components such as smear noise, ensuring uniform noise levels across all unit pixels and improving image quality by reducing the impact of inclined light components and leak light, thereby minimizing noise accumulation during the electric-charge holding period.
Implementation Method 1
opto-electric conversion section and electric-charge holding section are alternately laid out in each pixel column
Data Source
AI summary
A solid-state image taking device including a pixel section and a scan driving section wherein on each pixel column included in the pixel area determined in advance to serve as a pixel column having the unit pixels laid out in the scan direction, the opto-electric conversion section and the electric-charge holding section are laid out alternately and repeatedly, and on each of the pixel columns in the pixel area determined in advance, two the electric-charge holding sections of two adjacent ones of the unit pixels are laid out disproportionately toward one side of the scan direction with respect to the optical-path limiting section or the opto-electric conversion section.