Stacked Image Sensor CDS Processing for Low-Noise 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 suboptimal image quality due to the lack of correlated double sampling (CDS) before signal processing.
Innovation Solution
The image sensor design incorporates a laminated structure with a pixel substrate and an arithmetic operation substrate, where correlated double sampling is executed prior to arithmetic operations using digital signals from photoelectric conversion and noise signals, allowing for noise removal and efficient signal processing without increasing chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correlated double sampling is executed before arithmetic operations, then noise signal components can be removed from pixel outputs, but device complexity increases due to additional circuits required for CDS processing
Solution Approach 1:
The patent merges the CDS processing function with the existing arithmetic operation unit. The operation unit generates corrected signals by using reset signals and photoelectric conversion signals, effectively combining noise cancellation functionality into the existing arithmetic processing circuitry rather than adding separate dedicated CDS circuits.
Solution Approach 2:
The arithmetic operation unit is designed to perform multiple functions: it executes arithmetic operations on pixel signals while also generating corrected signals through correlated double sampling. This multi-functional design allows a single unit to handle both arithmetic processing and noise cancellation, reducing overall device complexity.
2Measurement precision
If additional circuits are added for correlated double sampling, then noise removal is enabled, but chip area increases
Solution Approach 1:
The patent integrates the CDS processing functionality into the existing arithmetic operation unit, eliminating the need for separate dedicated CDS circuits. By combining multiple functions within a single unit, the chip area required for additional circuits is minimized.
Solution Approach 2:
The patent utilizes a time-based approach where correlated double sampling is performed sequentially (first generating a first signal, then a second signal after reset) rather than requiring parallel hardware circuits. This temporal multiplexing allows noise removal functionality to be added without proportionally increasing chip area.
3Illumination intensity
If pixel opening ratios are maintained, then light collection efficiency is preserved, but signal processing capability is limited without additional circuits
Solution Approach 1:
The arithmetic operation unit performs self-service by generating corrected signals directly from the photoelectric conversion signals and reset signals. The unit processes signals autonomously without requiring external dedicated CDS circuits, thereby maintaining pixel opening ratios while still providing advanced signal processing capability.
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 high-speed arithmetic operations with improved image quality by removing noise components from individual pixel signals, reducing chip area requirements and maintaining the opening ratio of pixels.
Implementation Method 1
a photoelectric conversion unit that generates an electric charge through photoelectric conversion executed on light having entered therein
Data Source
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.