Image Sensor Readout Circuit Time-Division Multiplexing
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Solution Overview
Problem
Current image sensing devices face challenges in optimizing the readout path of pixel signals, leading to inefficiencies in signal processing and potential issues like dark current, hot pixels, and reduced resolution due to design complexities and the need for additional processes like deep trench isolation.
Innovation Solution
The design incorporates a pixel array with optimized readout paths using a readout circuit, global counter, and storing circuits that manage reset and data signals through time-sharing control signals, allowing for efficient signal transfer and storage, reducing design complexity and eliminating the need for certain isolation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional readout paths are used in image sensing devices, then signal transfer can be achieved, but design complexity increases and additional isolation processes like deep trench isolation are required
Solution Approach 1:
The patent merges the reset signal readout path and data signal readout path into a single shared readout line. The pixel array uses one readout line to sequentially transfer both reset signals and data signals to the readout circuit, eliminating the need for separate dedicated lines for each signal type. This reduces the number of readout lines and simplifies the overall device structure while maintaining proper signal isolation through time-division multiplexing.
Solution Approach 2:
The patent implements dynamic control of the readout line through a line control circuit that selectively connects or disconnects the shared readout line from different pixel groups based on the signal type being transferred. The readout line transitions between different operational states (reset signal mode vs. data signal mode) controlled by timing signals, allowing flexible and adaptive signal routing without requiring permanent separate physical paths.
2Reliability
If separate readout lines for reset and data signals are used, then signal isolation is improved, but the number of readout lines increases and pixel area expands
Solution Approach 1:
The patent combines multiple readout functions (reset signal transfer and data signal transfer) into a single physical readout line. By using time-division multiplexing where the same line handles different signal types at different times, the patent reduces the number of required readout lines from two (separate for reset and data) to one, thereby reducing the area occupied by readout infrastructure in the pixel array.
Solution Approach 2:
The patent employs periodic switching of the readout line's function through time-division multiplexing. The readout line alternates between transferring reset signals during a first time period and transferring data signals during a second time period. This periodic reassignment of the readout line's purpose allows efficient reuse of the same physical infrastructure while maintaining proper signal isolation through temporal separation.
3Productivity
If time-sharing control is implemented for readout lines, then readout path optimization is achieved, but control circuit complexity increases
Solution Approach 1:
The line control circuit is designed with multi-functionality to handle both reset signal routing and data signal routing through the same readout line. Rather than requiring separate control circuits for each signal type, a single universal line control circuit manages both functions by responding to different timing signals (reset timing signal vs. data timing signal), reducing overall control circuit complexity while maintaining efficient signal processing.
Solution Approach 2:
The readout circuit and line control circuit are designed to automatically manage the time-sharing allocation of the readout line based on incoming signal types and pre-established timing protocols. The system self-regulates the switching between reset and data signal modes without requiring external complex control, as the control logic is integrated into the readout circuitry itself which naturally responds to the timing characteristics of different signal types.
Data Source
AI summary
An image sensing device includes a pixel array; a plurality of lines coupled to the pixel array; a readout circuit coupled to the plurality of lines and structured to output a readout reset signal and a readout data; first readout lines coupled to the readout circuit and structured to transfer readout reset signals and readout data signals; a global counter coupled to count the readout reset signals and the readout data signals; a first storing circuit coupled to the first readout lines to receive the readout reset signals and the readout data signals; a line control circuit coupled to the first storing circuit; second readout lines coupled to the line control circuit and structured to transfer the readout control signals received from the line control circuit; and a second storing circuit coupled to the second readout lines to receive the readout control signals.