Imaging Column Circuit Reference Selection for Accurate ADC Correction
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Solution Overview
Problem
Imaging devices with AD converter circuits face increased correction errors due to varying parasitic capacitances when switching reference signals for correction value calculation and readout, especially when columns are powered on or off.
Innovation Solution
The imaging device employs a selector circuit that selectively uses either a first or second reference signal, with column circuits operating in different drive modes to manage current usage and parasitic capacitance, ensuring consistent reference signal slopes during correction value calculation and readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reference signals are switched between correction value calculation and readout, then different incident light amounts can be handled, but parasitic capacitance varies causing slope changes and correction errors
Solution Approach 1:
The patent applies local quality by making the second column circuit (driven by smaller current) select the same reference signal in both drive modes, while the first column circuit (driven by larger current) can switch reference signals. This localized differentiation resolves the contradiction by maintaining consistent parasitic capacitance for the second column circuit, ensuring correction accuracy, while allowing the first column circuit to adapt to different light amounts.
Solution Approach 2:
The patent changes the operating parameter (reference signal selection) based on the drive mode and current level. Specifically, the second column circuit maintains the same reference signal selection across both drive modes to keep parasitic capacitance constant, while the first column circuit changes reference signals to handle different incident light amounts, thus resolving the contradiction through parameter adaptation.
2Loss of energy
If column circuits are powered on or off selectively, then power consumption is reduced, but parasitic capacitance difference increases causing larger correction errors
Solution Approach 1:
The patent applies local quality by differentiating the behavior of column circuits based on their current drive level. The second column circuit (smaller current) is designed to select the same reference signal in both drive modes to maintain consistent parasitic capacitance, while the first column circuit (larger current) can switch reference signals. This localized approach allows power savings from selective column operation while minimizing correction errors through consistent reference signal selection in the second column circuit.
3Adaptability or versatility
If different reference signals are used for correction calculation and readout, then dynamic range is improved, but slope consistency deteriorates
Solution Approach 1:
The patent applies local quality by making the second column circuit select the same reference signal in both drive modes, ensuring slope consistency for that circuit. Meanwhile, the first column circuit can switch reference signals to handle different incident light amounts and expand dynamic range. This localized differentiation resolves the contradiction by maintaining slope consistency where needed while allowing dynamic range expansion where possible.
Data Source
AI summary
According to the present disclosure, column circuits operate selectively in a first drive mode to output a comparison signal or a second drive mode to acquire a correction value of a first reference signal and a second reference signal, and a selector circuit of a second column circuit selects the same reference signal out of the first reference signal and the second reference signal in the first drive mode and the second drive mode.