Stacked Image Sensor CDS Circuit for Noise-Free Pixel Arithmetic
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Solution Overview
Problem
Existing image sensors do not effectively remove noise signal components prior to arithmetic operations, leading to noise in image signals.
Innovation Solution
The image sensor employs a correlated double sampling (CDS) process before arithmetic operations, using a multi-layered structure with substrates for noise signal removal and digital signal conversion, allowing for noise-free signal processing without increasing chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If arithmetic operations are executed using signals from adjacent pixels without prior noise removal, then image processing functionality is achieved, but noise signal components remain in the output signals
Solution Approach 1:
The patent applies preliminary action by implementing the Correlated Double Sampling (CDS) process before arithmetic operations are executed. The CDS circuit removes noise signal components from pixel signals in advance, storing the cleaned signals in memory. This preliminary noise removal ensures that subsequent arithmetic operations using adjacent pixel signals do not propagate noise, thereby improving image processing quality while eliminating harmful noise factors.
2Reliability
If CDS circuit and A/D-conversion circuit are added to remove noise and convert signals, then noise removal capability is achieved, but device complexity increases
Solution Approach 1:
The patent merges the CDS noise removal function and the A/D conversion function into an integrated circuit structure. The CDS circuit is directly coupled with the A/D-conversion circuit, allowing noise removal and digital conversion to occur in a unified processing path. This merging approach achieves effective noise removal capability while reducing overall device complexity compared to having separate, independent circuits for each function.
Solution Approach 2:
The patent implements multi-functionality by designing the circuit to perform multiple operations within a unified structure. The same circuit infrastructure supports both the CDS noise removal process and the A/D conversion process, as well as subsequent arithmetic operations on adjacent pixels. This universal design achieves noise removal capability without proportionally increasing device complexity, as the circuit serves multiple purposes.
3Adaptability or versatility
If pixel memory stores all pixel signals for processing, then complete signal availability is achieved, but memory space requirements increase
Solution Approach 1:
The patent applies local quality by implementing arithmetic operations on a localized basis using signals from adjacent pixels rather than requiring all pixel signals to be stored and processed globally. The circuit performs operations on small groups of neighboring pixels, which reduces the memory space requirement while maintaining sufficient processing flexibility for local image processing tasks such as noise reduction and edge detection.
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 enables efficient noise removal from image signals, reducing chip area requirements and improving image processing quality by executing arithmetic operations with noise-free signals from selected pixels.
Implementation Method 1
a photoelectric conversion unit that converts light into electric charge
Data Source
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AI summary
An image sensor includes: a pixel substrate that includes a plurality of pixels each having a photoelectric conversion unit that generates an electric charge through photoelectric conversion executed on light having entered therein and an output unit that generates a signal based upon the electric charge and outputs the signal; and an arithmetic operation substrate that is laminated on the pixel substrate and includes an operation unit that generates a corrected signal by using a reset signal generated after the electric charge in the output unit is reset and a photoelectric conversion signal generated based upon an electric charge generated in the photoelectric conversion unit and executes an arithmetic operation by using corrected signals each generated in correspondence to one of the pixels.