CMOS Image Sensor Charge Overflow Control via Series Discharge Driving
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Solution Overview
Problem
The existing solid-state image capture elements face challenges in capturing high-quality images due to charge overflow issues, where the potential of the overflow gate needs to be adjusted between still and moving image modes, leading to potential image quality deterioration.
Innovation Solution
A solid-state image capture element with a configuration that includes a photoelectric conversion unit, a discharge unit, and multiple discharge driving units arranged in series, allowing for controlled discharge of charges during still image capture by sequentially reducing the potentials of the discharge driving units to prevent charge backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the potential of the overflow gate is lowered to prevent charge overflow during moving image capture, then charge overflow is suppressed, but the stored charge amount of the PD decreases
Solution Approach 1:
The patent applies dynamics by making the overflow gate potential switchable between two states: a lower potential during moving image capture to prevent charge overflow, and a higher potential during still image capture to maximize stored charge amount. This dynamic adjustment allows the system to optimize for different operational requirements.
Solution Approach 2:
The patent changes the electrical potential parameter of the overflow gate based on the capture mode. By switching the potential between high and low states, the system adapts to different requirements: preventing overflow during moving image capture while maximizing charge storage during still image capture.
2Object-affected harmful factors
If the potential of the overflow drain is lowered to switch the overflow gate potential, then charge overflow is controlled, but charges may flow back from the overflow drain to the PD
Solution Approach 1:
The patent applies preliminary action by discharging any charges that may have accumulated in the overflow drain to ground potential before switching the overflow gate potential to the lower state. This preliminary discharge prevents charge backflow to the PD when the overflow gate potential is lowered.
Solution Approach 2:
The patent applies preliminary anti-action by preemptively discharging charges from the overflow drain before the potential switching occurs. This counteracts the potential harmful effect of charge backflow before it can occur.
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 configuration enables the capture of higher-quality images by preventing charge backflow and maintaining image quality, while allowing for efficient charge management between still and moving image modes.
Implementation Method 1
a photoelectric conversion unit configured to convert incident light into a charge by photoelectric conversion and store the charge
Data Source
AI summary
The present disclosure relates to a solid-state image capture element, a driving method, and an electronic device which are enabled to capture a high-quality image. In the solid-state image capture element, at least two or more of the discharge driving units are arranged in series between the photoelectric conversion unit and the discharge unit. During capturing of a still image, when a reset operation of the photoelectric conversion unit is performed in starting exposure of the pixel, driving is performed such that after potentials of all the discharge driving units arranged in series are reduced and the charge remaining in the photoelectric conversion unit is discharged to the discharge unit, the potential of the discharge driving unit on the photoelectric conversion unit side is returned to an original potential first, and then the potential of another discharge driving unit is returned to an original potential. The present technology can be applied to a CMOS image sensor which performs imaging by, for example, a global shutter method.