Solid-State Imaging Device Pixel Reset Synchronization
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Solution Overview
Problem
Conventional solid-state imaging devices with n-pixel one-cell configurations experience image quality deterioration due to reset-state differences between rows, leading to afterimages and horizontal lines, especially when using a front curtain electronic shutter synchronized with a rear curtain mechanical shutter.
Innovation Solution
A solid-state imaging device with a row scanning unit that performs simultaneous pixel reset operations for all n pixels within a unit cell, using a shared reset transistor and floating diffusion, and adjusts timing based on the mechanical curtain shutter's running quality to ensure consistent reset states across rows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sequential pixel reset scanning is performed row by row in conventional n-pixel one-cell configuration, then device complexity is reduced by sharing reset transistor and floating diffusion, but image quality deteriorates due to reset-state differences between rows
Solution Approach 1:
The imaging device divides pixels into multiple independent cell groups, where each cell group contains n pixels that share a reset transistor and floating diffusion. By segmenting the pixel array into independent cell groups rather than having all n pixels share resources across the entire array, the patent maintains uniform reset timing within each cell group while reducing overall device complexity through resource sharing at a localized level.
Solution Approach 2:
The patent implements dynamic control of reset timing by independently controlling the reset timing for each cell group based on the mechanical shutter curtain speed. The control unit adjusts the reset timing of each cell group to ensure that exposure ends simultaneously across all cell groups, compensating for the sequential scanning nature and maintaining uniform reset states without requiring simultaneous resetting of all pixels.
2Weight of moving object
If front curtain electronic shutter is implemented with sequential reset scanning, then mechanical shutter weight is reduced, but afterimages and horizontal lines appear due to reset-state differences
Solution Approach 1:
The control unit receives feedback about the mechanical shutter curtain speed and uses this information to dynamically adjust the reset timing for each cell group. By monitoring the shutter operation and adapting the reset timing accordingly, the system ensures that exposure timing is synchronized with the mechanical shutter movement, preventing reset-state differences that cause afterimages and horizontal lines.
Solution Approach 2:
The patent performs preliminary adjustment of reset timing for each cell group based on predicted or measured mechanical shutter curtain speed. Before the mechanical shutter completes its traversal, the system pre-configures the reset timing for each cell group to ensure uniform exposure termination, preventing the generation of afterimages and horizontal lines before they can occur.
3Area of moving object
If n pixels share one reset transistor and floating diffusion, then photodiode area per pixel is increased, but reset-state differences cause deterioration in image quality
Solution Approach 1:
The patent segments the pixel array into multiple independent cell groups, with each cell group containing n pixels that share a reset transistor and floating diffusion. This segmentation limits the scope of resource sharing to small, manageable groups, ensuring that reset-state differences do not propagate across the entire array. Each cell group operates semi-independently, maintaining uniform reset states within the group while preserving the photodiode area benefits of resource sharing.
4Device complexity
If pixel reset scanning is performed sequentially row by row, then device complexity is reduced, but exposure timing synchronization with mechanical shutter becomes difficult
Solution Approach 1:
The patent implements dynamic timing control that adapts to the mechanical shutter curtain speed. The control unit independently adjusts the exposure timing and reset timing for each cell group based on the actual shutter operation, enabling synchronization with the mechanical shutter while maintaining sequential row-by-row scanning. This dynamic adaptation allows the system to accommodate different shutter speeds and maintain proper exposure timing without increasing device complexity.
Solution Approach 2:
The system performs preliminary configuration of exposure timing for each cell group based on the mechanical shutter curtain speed before exposure begins. By pre-calculating and setting the timing parameters for each cell group in advance, the patent enables proper synchronization with the mechanical shutter while maintaining the simplicity of sequential scanning operation during actual exposure.
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 reduces image quality deterioration by eliminating reset-state differences between rows, allowing for improved image capture without afterimages and horizontal lines, even in mechanical curtain shutter synchronous modes.
Implementation Method 1
each including a photodiode which converts incident light into electric charges
Data Source
AI summary
A solid-state imaging device simultaneously completes pixel reset operation on all of pixels included in a unit cell when performing pixel reset scanning in a curtain shutter synchronous mode. The pixel reset operation is processing in which a photodiode corresponding to one of transfer transistors is reset. The pixel reset scanning is processing in which the pixel reset operation is performed on a row basis. The curtain shutter synchronous mode is a mode in which exposure of an imaging region to incident light is started by the pixel reset scanning and ended by blocking the incident light by a mechanical curtain shutter provided on an optical path of the incident light.