Imaging Device Floating Diffusion Reset for Charge Saturation
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Solution Overview
Problem
Existing imaging devices fail to set individual accumulation periods for each pixel group, leading to residue charge in the floating diffusion, which results in differences between actual object imaging and image data due to charge saturation and storage capacity limitations.
Innovation Solution
The imaging device includes a plurality of imaging elements with a light-receiving element, floating diffusion, charge transfer switch, reset switch, and source follower, where the reset switch resets the floating diffusion multiple times and the charge transfer switch transfers charge multiple times for each pixel group within a single image data acquisition period, ensuring accurate charge transfer and storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charge is transferred to a floating diffusion that still has residue charge and is not in a reset state, then the floating diffusion cannot store more charge than the storage capacity, but charge remains in the photodiode and residue charge is added to newly generated charge in the next accumulation period, resulting in differences between actual object imaging and image data
Solution Approach 1:
The patent applies preliminary action by resetting the floating diffusion to a predetermined level before charge transfer occurs. The control unit resets the floating diffusion in advance using the reset switch, ensuring it is in a known state with zero or predetermined charge level before receiving charge from the photodiode. This prevents residue charge from affecting subsequent measurements and ensures accurate image data acquisition.
Solution Approach 2:
The patent uses parameter changes by dynamically adjusting the voltage level of the floating diffusion through controlled resetting operations. The control unit changes the charge state of the floating diffusion from an unknown residue state to a predetermined reset state by applying reset voltages, thereby controlling the electrical parameters to ensure accurate charge transfer and measurement.
2Device complexity
If the floating diffusion is not reset before charge transfer, then the device complexity is reduced, but charge saturation occurs and the floating diffusion cannot store more charge than the storage capacity
Solution Approach 1:
The patent applies self-service by enabling the floating diffusion to automatically reset itself to a predetermined charge level before each charge transfer operation. The reset switch and control unit work together to autonomously restore the floating diffusion to its initial state, eliminating the need for external manual intervention and ensuring consistent operational conditions without adding significant system complexity.
3Measurement precision
If multiple reset and charge transfer operations are performed for each pixel group in a single image data acquisition period, then pixel sensitivity differences among groups are corrected and charge saturation is prevented, but the operation time increases
Solution Approach 1:
The patent applies periodic action by performing reset and charge transfer operations at regular intervals during the image data acquisition period. The control unit systematically resets each pixel group's floating diffusion and transfers charge multiple times throughout the acquisition period, ensuring uniform sensitivity correction across all pixel groups while maintaining efficient timing through periodic rather than continuous operations.
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 corrects differences in pixel sensitivity among groups and reduces the influence of charge generated during non-imaging periods, ensuring accurate image data acquisition by preventing charge saturation and optimizing charge transfer.
Implementation Method 1
a light-receiving element, configured to generate charge from received light by photoelectric conversion
Data Source
AI summary
An imaging device includes a plurality of arranged imaging elements each including: a light-receiving element configured to generate charge from received light by photoelectric conversion, a floating diffusion configured to convert the charge generated by the light-receiving element into voltage, a charge transfer switch configured to transfer the charge from the light-receiving element to the floating diffusion, a reset switch configured to reset the voltage of the floating diffusion, and a source follower configured to amplify the voltage of the floating diffusion. The reset switch is configured to reset the voltage of the floating diffusion a plurality of times for each of predetermined pixel groups in a single image data acquisition period. The charge transfer switch is configured to transfer the charge from the light-receiving element to the floating diffusion a plurality of times for each of the pixel groups in the single image data acquisition period.