Solid-State Imaging Device Dual Reset Mechanism for Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state imaging devices do not effectively remove reset noise from pixels, which is associated with the switch operation for initializing signal charges, and this is not addressed in existing configurations that aim to reduce power consumption.
Innovation Solution
A solid-state imaging device with a configuration that includes pixels with photoelectric conversion elements, charge-voltage conversion terminals, and reset means for switching between conduction and disconnection to reset voltages, allowing for noise signal read-out operations and optical signal read-out operations to be performed while maintaining low power consumption by using floating potential signal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional configuration outputs voltage in response to signal charges accumulated in each pixel as-is to each vertical signal line, then power consumption is reduced by eliminating constant current sources, but reset noise cannot be removed from pixels
Solution Approach 1:
The patent divides the reset operation into two separate reset devices: a first reset device for resetting the charge-voltage conversion terminal (floating diffusion region) and a second reset device for resetting the vertical signal line. This segmentation allows independent control of reset operations, enabling complete removal of reset noise while maintaining the capacitive load configuration that eliminates constant current sources and reduces power consumption.
Solution Approach 2:
The patent performs a preliminary reset operation on the charge-voltage conversion terminal before the signal charge transfer and voltage conversion process. By resetting the floating diffusion region to a known potential beforehand, the system ensures that no residual reset noise remains in the pixel after the imaging operation, while still using the low-power capacitive load configuration.
2Object-affected harmful factors
If reset noise is to be completely removed from pixels, then additional reset devices and operations are needed, but this increases device complexity
Solution Approach 1:
The patent designs the second reset device to serve multiple functions: it resets the vertical signal line to a known potential, provides a reference level for noise subtraction operations, and enables the capacitive load configuration to function properly. This multi-functionality justifies the addition of the reset device while managing overall system complexity.
Solution Approach 2:
The patent introduces a floating diffusion region as an intermediary charge-voltage conversion terminal between the photodiode and the vertical signal line. This intermediary element allows for separate reset control and complete noise removal while maintaining the low-power capacitive load architecture, effectively managing the trade-off between noise removal and complexity.
3Measurement precision
If signal charges are to be completely transferred to the charge-voltage conversion terminal, then all signal charges must be moved, but residual charges remain in conventional configurations preventing complete transfer
Solution Approach 1:
The patent segments the signal path into distinct functional regions: the photodiode for charge generation, the transfer transistor for charge movement, and the floating diffusion region as a dedicated charge-voltage conversion terminal. This segmentation ensures complete charge transfer by providing a clear destination with proper reset control, eliminating residual charges while maintaining a manageable device structure.
Solution Approach 2:
The patent performs preliminary resetting of the charge-voltage conversion terminal before charge transfer, creating a ready state that accepts all signal charges without residual interference. This preliminary preparation ensures complete charge transfer and improves measurement precision while using the same basic device structure.
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 removes reset noise from pixels while maintaining low power consumption, eliminating the need for constant current sources and analog memory, thus downsizing the device and improving signal precision.
Implementation Method 1
each of the pixels includes a photoelectric conversion element for photoelectrically converting incident light so as to accumulate signal charges
Data Source
AI summary
To remove reset noise in pixels while the circuit configuration is kept in low power consumption, a device includes pixels arranged in row and column directions, in which each of the pixels includes a charge-voltage conversion terminal for voltage-converting signal charges transferred from a photoelectric conversion element, and a first reset means for resetting a voltage at the charge-voltage conversion terminal; first signal lines, each of which is connected to the pixels in each column; a scanning means for selecting one row among others; and a second reset means for resetting voltages at the signal lines. In the device, on each selected row, by voltage signals at the charge-voltage conversion terminals and the converted voltage signals from the transferred signal charges are read out to and stored in the signal lines in a floating potential state, and then are output.