Image Sensor Pixel Array Single Capacitor Charge Readout
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Solution Overview
Problem
Conventional image sensing pixel structures require multiple sets of capacitors to read out and store charges from sensing and reset signals, leading to a large circuit size and high costs, which is not suitable for smaller size circuit designs.
Innovation Solution
The image sensor and sensing pixel array incorporate a novel design with each sensing pixel unit featuring a photodiode, row reset transistor, buffer transistor, storage capacitor, and column control transistor, allowing charges to be output one by one using a single set of capacitors, reducing the need for multiple capacitor sets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple sets of capacitors are used to store sensing signal charges and reset signal charges, then the charge storage function is improved, but the circuit area increases
Solution Approach 1:
The patent merges the charge storage function into a single capacitor that is shared across multiple sensing pixel units. Instead of allocating separate capacitors to each pixel unit, one capacitor serves multiple pixels by sequentially storing sensing signal charges and reset signal charges from different pixels, thereby reducing the total circuit area while maintaining adequate charge storage capability
Solution Approach 2:
The single capacitor is designed to perform multiple functions: it stores sensing signal charges from one pixel, then subsequently stores reset signal charges from the same or different pixels. This multi-functional design allows the same hardware resource to serve multiple purposes across different pixel units, eliminating the need for dedicated capacitors for each pixel
2Productivity
If multiple sets of capacitors are used to read out charges from different sensing pixel units, then the charge reading capability is improved, but the device complexity increases
Solution Approach 1:
The patent combines the charge reading function into a unified circuit architecture where a single capacitor and shared readout path serve multiple sensing pixel units. The same capacitor and readout circuitry are reused sequentially for different pixels, reducing the number of independent reading paths and simplifying the overall device complexity
Solution Approach 2:
The system employs periodic sequential reading operations where charges from different pixel units are read out in a time-multiplexed manner. The single capacitor alternates between storing sensing signals and reset signals from different pixels in a periodic sequence, enabling multiple pixels to be serviced by a single reading resource without requiring simultaneous dedicated reading circuits for each pixel
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 design achieves a smaller circuit size and lower costs by enabling the use of only one set of analog receiving circuitry to handle charges from multiple sensing and reset signals, improving efficiency and reducing manufacturing costs.
Implementation Method 1
The photodiode is configured for converting light to generate a sensing signal
Data Source
AI summary
A sensing pixel array used in an image sensor includes sensing pixel units each including a photodiode, a row reset transistor, a buffer transistor, and a column control transistor at least. Photodiode converts light into a sensing signal. Row reset transistor is coupled to a reference reset signal and photodiode, and is controlled by a row reset signal. Buffer transistor is coupled to the output of photodiode to receive and buffer the sensing signal. Column control transistor is electrically connected to the control end or the output of the buffer transistor and is used as a switch which can be closed or open according to a column control signal to control whether to transfer charge of the reference reset signal to a capacitor when the row reset transistor becomes conductive.