Image Sensor Bias Switching for Low-Noise Fast Readout
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Solution Overview
Problem
Image sensors face challenges in reducing noise components and settling time during readout operations, which affect their operating speed and noise properties.
Innovation Solution
The image sensor employs a bias circuit with multiple current circuits and a switching circuit that maintains transistors in a turn-on state during readout, reducing noise components and settling time by stabilizing bias currents across column lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If transistors are turned off during readout operation to save power, then power consumption is reduced, but noise components increase and settling time increases
Solution Approach 1:
The patent applies dynamics by making the transistor state adjustable rather than fixed. The transistors in the current circuits are maintained in a turn-on state during readout operation through dynamic control of the switching circuit, allowing the system to adapt between power saving mode (transistors off) and low-noise mode (transistors on) based on operational requirements
Solution Approach 2:
The patent changes the operational parameter of the transistors from off-state to on-state during readout operation. By controlling the switching circuit to maintain transistors in a turn-on state, the bias current parameters remain stable, reducing noise components and settling time while managing power consumption
2Use of energy by moving object
If transistors are turned off during readout operation to save power, then power consumption is reduced, but settling time increases
Solution Approach 1:
The patent applies dynamics by making the transistor state adjustable rather than fixed. The transistors in the current circuits are maintained in a turn-on state during readout operation through dynamic control of the switching circuit, allowing the system to adapt between power saving mode (transistors off) and fast-settling mode (transistors on) based on operational requirements
Solution Approach 2:
The patent changes the operational parameter of the transistors from off-state to on-state during readout operation. By controlling the switching circuit to maintain transistors in a turn-on state, the bias current parameters remain stable, reducing settling time while managing power consumption
3Object-generated harmful factors
If separate current circuits are used for each column line to reduce noise, then noise components are reduced, but device complexity increases
Solution Approach 1:
The patent merges multiple column lines into groups that share common current circuits. Instead of providing separate current circuits for each column line, the switching circuit groups column lines and assigns them to shared current circuits, reducing the total number of current circuits while maintaining noise performance through proper switching control
Solution Approach 2:
The patent makes current circuits universal by enabling them to serve multiple column lines through the switching circuit. Each current circuit can be dynamically assigned to different column lines based on the readout operation requirements, allowing one current circuit to perform multiple functions across different time periods
Data Source
AI summary
An image sensor includes a first column line and a second column line configured to extend in a first direction, a plurality of pixel groups configured to connect to the first column line or the second column line and to comprise a plurality of pixels in each of the plurality of pixel groups, a bias circuit configured to comprise a first current circuit and a second current circuit configured to output different bias currents in a first operational mode, and a switching circuit configured to connect the first column line to the first current circuit and connect the second column line to the second current circuit during a first time period, and to connect the first column line to the second current circuit and connect the second column line to the first current circuit during a second time period subsequent to the first time period in the first operational mode.