Digital Pixel Memory Layout for Low-Noise Image Sensors
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Solution Overview
Problem
Conventional CMOS image sensors produce analog signals that are prone to noise and coupling during conversion to digital signals, resulting in reduced image quality and inability to process high-resolution images effectively.
Innovation Solution
The implementation of digital pixels within the image sensor device, each comprising a photo detector, analog-to-digital converter, and memory circuit, allows for direct digital signal output at the pixel level, reducing noise susceptibility and enabling high-speed image processing through a pixel driver and digital logic circuit that controls and processes these signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If analog pixels are used to output light signals, then the device complexity is reduced, but the noise susceptibility increases and image quality deteriorates
Solution Approach 1:
The pixel is divided into distinct functional modules: photo detector unit, signal generation unit, and digital processing unit. Each unit performs a specific function, allowing the analog-to-digital conversion to occur at the pixel level rather than requiring separate analog signal transmission, thereby reducing noise susceptibility while maintaining manageable complexity through modular design
Solution Approach 2:
An intermediate signal generation unit is introduced between the photo detector and the digital processing unit. This unit generates digital signals based on the analog light signals from the photo detector, acting as a mediator that converts analog signals to digital signals at the pixel level, eliminating the need for analog signal transmission and reducing noise susceptibility
2Device complexity
If analog signals are transmitted to AD converter, then the device complexity is reduced, but the signal modification and noise increase
Solution Approach 1:
The analog-to-digital conversion is performed preliminarily at the pixel level before signal transmission. The digital processing unit within each pixel converts the analog light signals to digital signals in advance, so that only digital signals need to be transmitted and processed further, preventing signal modification and noise that would occur during analog signal transmission and conversion
3Reliability
If digital pixels with AD converter are implemented, then the noise susceptibility is reduced, but the device complexity increases
Solution Approach 1:
The digital pixel is segmented into three main units: photo detector unit for light detection, signal generation unit for analog-to-digital conversion, and digital processing unit for signal processing. This segmentation allows each unit to be optimized for its specific function while keeping the overall pixel structure manageable and systematic
Solution Approach 2:
The digital processing unit performs multiple functions including analog-to-digital conversion, signal processing, and data output within a single integrated unit. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby managing device complexity while achieving noise-resistant digital signal processing
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 enhances image quality by minimizing signal modification and noise, enabling the processing of high-resolution images with improved speed and reliability, suitable for various electronic devices.
Implementation Method 1
each of the plurality of digital pixels DP may include a photo detector PDT configured to detect incident light and output a detection signal DET
Data Source
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AI summary
An image sensor device including: a first digital pixel including a first photodetector and first memory cells to store a first digital signal corresponding to a first output from the first photodetector; and a second digital pixel including a second photodetector and second memory cells to store a second digital signal corresponding to a second output from the second photodetector, the second digital pixel is adjacent to one side of the first digital pixel, the first memory cells and the second memory cells are connected with a plurality of bit lines, the first memory cells are connected with a first word line and a third word line, the second memory cells are connected with a second word line and a fourth word line, the second word line is between the first and third word lines, and the third word line is between the second and fourth word lines.