CMOS Image Sensor High Dynamic Range Motion Detection
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Solution Overview
Problem
Conventional CMOS image sensors face limitations in achieving high dynamic range due to pixel size, fill factor, and power consumption constraints, which prevents simultaneous integration of high dynamic range imaging and motion detection in high illumination conditions.
Innovation Solution
The implementation of in-pixel digital storage for controlling integration time and using dual photodiodes per pixel to manage saturation and enhance dynamic range, allowing for motion detection even in high illumination without additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional approaches to achieve high dynamic range are used, then dynamic range is improved, but pixel size, fill factor, and power consumption are significantly sacrificed
Solution Approach 1:
The pixel array is divided into multiple pixel groups, where each group shares a common floating diffusion node for storing reset information. This segmentation allows the system to achieve high dynamic range functionality without requiring additional storage elements in each individual pixel, thereby maintaining small pixel size while still achieving over 120 dB dynamic range.
Solution Approach 2:
The floating diffusion node serves multiple functions: it acts as the charge collection node for photodetectors and simultaneously stores digital reset information for high dynamic range imaging. This multi-functionality eliminates the need for separate storage elements, preserving pixel area while enabling HDR capability.
2Measurement precision
If conventional approaches to achieve high dynamic range are used, then dynamic range is improved, but power consumption is significantly increased
Solution Approach 1:
By dividing the pixel array into groups that share common floating diffusion nodes for reset information storage, the system reduces the total number of storage elements required compared to per-pixel storage approaches. This reduction directly lowers the power consumption associated with maintaining multiple small storage nodes across the entire sensor array.
Solution Approach 2:
The floating diffusion node performs dual functions as both charge collection node and digital information storage node. This eliminates the need for separate dedicated storage circuits, thereby reducing overall power consumption while maintaining high dynamic range performance.
3Adaptability or versatility
If conventional motion detection schemes are used, then motion detection is available, but it becomes unavailable in high illumination due to pixel saturation
Solution Approach 1:
The system performs preliminary conditional reset of photodetectors based on stored reset information before saturation occurs. By checking the stored digital reset information and resetting pixels that are approaching saturation, the system prevents pixel saturation in advance, thereby maintaining motion detection capability even in high illumination conditions.
Solution Approach 2:
The system uses stored reset information as feedback to determine when to reset individual pixels or pixel groups. This feedback mechanism allows the system to adaptively control integration time based on illumination levels, preventing saturation and maintaining motion detection functionality across varying illumination conditions including high illumination.
4Adaptability or versatility
If in-pixel digital storage is implemented for each pixel, then motion detection in high illumination is achieved, but frame memory size increases
Solution Approach 1:
The pixel array is segmented into multiple pixel groups that share common floating diffusion nodes for storing reset information. Instead of allocating 4 bits per pixel, each pixel group shares the storage resources, reducing the total frame memory size while still enabling motion detection in high illumination through conditional reset based on stored reset information.
Solution Approach 2:
Adjacent pixels are merged into groups that share common floating diffusion nodes for digital information storage. This merging reduces the total number of storage nodes required across the sensor array, thereby reducing frame memory size while maintaining the capability for motion detection in high illumination through group-level conditional reset.
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 CMOS image sensors to achieve dynamic ranges exceeding 120 dB and perform motion detection in high illumination, reducing memory requirements and power consumption while maintaining small pixel size.
Implementation Method 1
an array of pixels to capture an image, the array of pixels arranged as a plurality of pixel groups, each of the pixel groups having a two or more pixels, each having a floating diffusion node for outputting an image signal
Data Source
AI summary
This disclosure describes: (1) two different schemes to enhance dynamic range, (2) a new motion detection scheme using in-pixel digital storage, and (3) the motion detection in high illumination for CMOS image sensors. The schemes may be implemented in a small pixel size and easily incorporated in simple column-level circuits for existing CMOS image sensor systems.