Solid-State Image Sensor Noise Immunity via Transfer Line Segmentation
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Solution Overview
Problem
Conventional solid-state image pickup apparatuses face challenges in maintaining noise immunity when pixel output fluctuates during readout periods, especially as the number of pixels increases, due to the deletion of capacitive elements for downsizing.
Innovation Solution
The apparatus employs a configuration with first and second transfer lines, inter-transfer-line capacitive elements, and readout switches to hold and manage noise and signal-noise sum voltages, allowing for accurate noise removal and high noise immunity by shortening the time difference between noise and signal-noise sum signal outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If capacitive elements provided for columns are deleted for downsizing, then device size is reduced, but noise immunity deteriorates when pixel output fluctuates during readout period
Solution Approach 1:
The patent divides the transfer line function into two separate lines: a first transfer line for holding noise voltages and a second transfer line for holding signal-noise sum voltages. This segmentation allows independent management of noise and signal paths, maintaining noise immunity while enabling compact design without traditional column capacitive elements.
Solution Approach 2:
The patent introduces inter-transfer-line capacitive elements as intermediary components connecting the first and second transfer lines. These capacitive elements enable voltage transfer and coupling between lines, facilitating noise removal through capacitive coupling while maintaining a compact structure without requiring traditional column capacitors.
2Device complexity
If capacitive elements are deleted for downsizing, then device complexity is reduced, but measurement precision of noise removal deteriorates
Solution Approach 1:
The patent segments the voltage holding function into two distinct transfer lines with dedicated functions. The first transfer line exclusively holds noise voltages while the second holds signal-noise sum voltages, enabling precise differential measurement for noise removal without requiring complex column capacitive elements.
Solution Approach 2:
The patent implements a feedback mechanism where noise voltages are read out from the first transfer line, and the same noise component is subtracted from the signal-noise sum voltages in the second transfer line. This feedback-based noise cancellation maintains high measurement precision while simplifying the overall circuit structure.
3Reliability
If readout period is extended to read both noise and signal-noise sum signals, then noise removal capability is maintained, but pixel output fluctuation increases
Solution Approach 1:
The patent performs preliminary action by holding both noise voltages and signal-noise sum voltages simultaneously in the respective transfer lines before readout. This allows both signals to be captured at the same moment, eliminating pixel output fluctuations that occur during extended sequential readout while maintaining noise removal capability through subsequent differential processing.
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 output of signals with high noise immunity even during pixel output fluctuations, simplifying the readout process and reducing the need for complex circuits, while allowing for downsizing without compromising image quality.
Implementation Method 1
inter-transfer-line capacitive elements connecting the second transfer lines and the first transfer lines; the plurality of first transfer lines being capable of holding voltages based on signals outputted from the output terminals
Implementation Method 2
an optical-electrical conversion element performing optical-electrical conversion of an incident light
Implementation Method 3
a reset switch resetting each of the second transfer lines to a reset voltage
Data Source
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AI summary
Even if pixel output fluctuates during a readout period, a signal with a high noise immunity is outputted. There is provided a solid-state image pickup apparatus provided with: a plurality of two-dimensionally arrayed unit pixels (9), each of the unit pixels including a PD (11) performing optical-electrical conversion of an incident light; an FD (13) and an output terminal (8) provided for each of a plurality of pixel groups, each pixel group including one or more unit pixels (9), the output terminal (8) being capable of outputting a noise signal and a signal-noise sum signal separately; a plurality of first transfer lines (6a) to which the output terminals (8) are connected in common, the plurality of first transfer lines being capable of holding voltages based on signals outputted from the output terminals (8); a plurality of second transfer lines (6b) provided in parallel with the first transfer lines (6a), the plurality of second transfer lines (6b) being capable of holding a voltage; inter-transfer-line capacitive elements (20) connecting the second transfer lines (6b) and the first transfer lines (6a); a reset switch (16b) resetting each of the second transfer lines (6b) to a reset voltage; a readout switch (19) provided for each of the second transfer lines (6b); and a third transfer line (7) to which the second transfer lines (6b) are connected in parallel via the readout switches, respectively.