Signal Processing Device for Imaging Noise Reduction
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Solution Overview
Problem
In imaging devices, spurious signals occur due to fluctuations in the vertical signal line during A/D conversion, leading to errors in signal reading and noise conversion, which existing techniques like disconnection switches fail to fully mitigate due to charge injection and clock feedthrough issues.
Innovation Solution
A signal processing device that suspends signal supply to the A/D conversion unit during A/D conversion periods, using a control unit and maintenance unit to maintain and supply a stable signal value, and performs correlated double sampling to differentiate between pre-charge and data periods, thereby reducing noise and spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a disconnection switch is provided in the vertical signal line to suppress output fluctuation, then spurious signal occurrence is reduced, but charge injection and clock feedthrough cause signal errors
Solution Approach 1:
The patent introduces a sampling switch as an intermediary component between the vertical signal line and the A/D conversion unit. This sampling switch, controlled by a sampling clock signal, mediates the signal transmission by selectively connecting and disconnecting the vertical signal line from the A/D conversion unit at precise timing moments. The intermediary sampling switch enables controlled signal sampling while isolating the system from harmful fluctuations, thereby reducing spurious signals without causing the charge injection and clock feedthrough issues that would compromise signal accuracy
Solution Approach 2:
The patent implements periodic action through the sampling clock signal that rhythmically controls the sampling switch to connect and disconnect at regular intervals synchronized with the A/D conversion timing. This periodic switching action allows the system to sample signals at optimal moments while maintaining stable operation during A/D conversion, effectively suppressing spurious signals generated by vertical signal line fluctuations without introducing continuous interference that would degrade signal accuracy
2Stability of the object's composition
If signal supply is suspended during A/D conversion period, then signal stability is improved, but timing control complexity increases
Solution Approach 1:
The sampling switch serves multiple functions simultaneously: it acts as a signal transmission gate, a timing synchronization element, and a stability control mechanism. By making the sampling switch multi-functional, the patent achieves signal stability during A/D conversion without requiring separate dedicated control circuits for each function, thereby reducing overall control circuit complexity while maintaining stable signal supply timing
Solution Approach 2:
The patent incorporates timing control that monitors the A/D conversion status and provides feedback to the sampling switch control. This feedback mechanism ensures the sampling switch operates at the correct moments in the signal processing cycle, automatically adjusting its operation based on conversion timing requirements. The feedback-based timing control achieves precise signal stability management without requiring overly complex external control circuitry
Data Source
AI summary
A signal processing device includes a control unit that suspends supplying of a signal to an A/D conversion unit which performs A/D conversion, during an A/D conversion period in which the A/D conversion is performed on the signal that depends on an electric charge read from a pixel; and a maintenance unit that maintains a signal value of the signal in a state where the signal is supplied by the control unit to the A/D conversion unit and that supplies the maintained signal value to the A/D conversion unit in a state where the supplying of the signal to the A/D conversion unit is suspended by the control unit.