Solid-State Imaging Differencing Circuit Noise Reduction
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Solution Overview
Problem
Solid-state imaging devices using frame differencing with analog pixel signals suffer from noise degradation, particularly in low-light conditions, which degrades image quality.
Innovation Solution
A configuration of a differencing circuit that incorporates noise reduction techniques, including double sampling and kTC noise reduction circuits, to mitigate noise in frame differencing by successively receiving and processing pixel signals from the same pixel circuit within a row selection interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If frame differencing is performed using analog pixel signals, then motion detection capability is improved, but noise degradation occurs particularly in low-light conditions
Solution Approach 1:
The patent segments the pixel signal processing into multiple temporal samples within the same row selection interval. By dividing the signal acquisition into discrete sampling points (first pixel signal and second pixel signal), the system can perform differencing operations to isolate motion information while canceling out common-mode noise components.
Solution Approach 2:
The patent performs preliminary noise reduction by obtaining a reference pixel signal from a previous row selection interval before processing the current frame. This reference signal is used to pre-compensate for fixed pattern noise and low-frequency interference, allowing the subsequent differencing operation to focus primarily on motion detection while maintaining signal quality.
2Measurement precision
If double sampling is implemented for noise reduction, then image quality is improved, but device complexity increases
Solution Approach 1:
The patent merges the double sampling noise reduction function with the frame differencing operation by using the same pixel circuit and data line infrastructure. The first and second pixel signals are obtained through sequential sampling within the same row selection interval, eliminating the need for separate sampling circuits and reducing overall device complexity while maintaining noise reduction effectiveness.
Solution Approach 2:
The pixel circuit is designed to serve multiple functions: it performs photoelectric conversion, generates pixel signals for intensity readout, and simultaneously provides signals for both double sampling noise reduction and frame differencing operations. This multi-functionality reduces the need for dedicated circuits for each operation, thereby lowering 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
The solution effectively reduces noise in image quality, allowing for improved image processing without elaborate digital processing downstream, enhancing performance in low-light conditions.
Implementation Method 1
Image sensors in solid-state imaging devices include photoelectric conversion elements generating a photocurrent in proportion to the received radiation intensity
Data Source
AI summary
A solid-state imaging device includes pixel circuits, wherein each pixel circuit outputs pixel signals on a data signal line in response to an active row select signal in a row selection interval. Each pixel circuit includes a floating diffusion, wherein a floating diffusion potential of the floating diffusion determines a voltage level of the pixel signals. For each of the pixel circuits, a differencing circuit receives two pixel signals successively transmitted from the pixel circuit on the data signal line within a same row selection interval. The differencing circuit obtains a difference signal from the two pixel signals. The solid-state imaging device controls each pixel circuit to output a previous pixel signal and a new pixel signal in a same row selection interval, wherein the previous pixel signal and the new pixel signal contain image information about an imaged scene at different points in time.