Pixel Sharing Architecture for Global Shutter Image Sensors
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Solution Overview
Problem
CMOS solid-state image capture devices with global shutter functions face challenges in miniaturization due to the difficulty in implementing a pixel-sharing system, which is hindered by signal mixing in floating diffusion sections and CCD-type charge-holding capacitor sections, leading to distorted images of fast-moving subjects and reduced pixel density.
Innovation Solution
An electronic apparatus with a pixel array and a mechanical shutter, where pixels share photoelectric conversion sections, transistors, and charge accumulation sections, allowing simultaneous exposure and readout of all pixels, and employing a mechanical shutter for still-image shooting to achieve a global shutter function while enabling miniaturization through pixel-sharing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a pixel-sharing system is used to reduce pixel size, then pixel density increases, but signal mixing occurs in floating diffusion sections and CCD-type charge-holding capacitor sections preventing global shutter function
Solution Approach 1:
The pixel circuit is divided into multiple independent charge accumulation sections: a first charge accumulation section (floating diffusion section) and a second charge accumulation section (CCD-type capacitor). Each section independently stores signal charges from different pixels without mixing, allowing multiple pixels to share the same pixel circuit while maintaining signal integrity for global shutter operation.
Solution Approach 2:
A transfer gate is introduced as an intermediary component between the photoelectric conversion section and the charge accumulation sections. This transfer gate controls the flow of signal charges, enabling selective transfer to different accumulation sections and preventing signal mixing while maintaining the pixel-sharing architecture.
2Quantity of substance
If floating diffusion sections are used as charge-holding capacitor sections to increase saturation electrons, then charge storage capacity increases, but signal mixing occurs making pixel sharing impossible
Solution Approach 1:
Multiple charge accumulation functions are merged into a single pixel circuit by incorporating both a floating diffusion section and a CCD-type charge-holding capacitor section. This combination allows the circuit to handle signals from multiple pixels simultaneously without mixing, enabling both high charge storage capacity and pixel-sharing capability.
Solution Approach 2:
The charge accumulation function is extended from a single two-dimensional floating diffusion region to a multi-dimensional structure combining floating diffusion and CCD-type capacitor sections. This dimensional expansion allows independent charge storage paths for multiple pixels within the same pixel circuit area.
3Device complexity
If sequential readout is used to simplify circuit structure, then device complexity decreases, but exposure timing differences cause distortion of fast-moving subjects
Solution Approach 1:
Signal charges from all pixels are accumulated simultaneously in the charge accumulation sections during the exposure period before readout begins. This preliminary simultaneous accumulation ensures that all pixels capture the same temporal moment, preventing distortion of fast-moving subjects while allowing sequential readout to simplify the circuit structure.
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
The solution allows for simultaneous exposure and readout of all pixels, enabling both moving-image and still-image shooting with a global shutter, reducing pixel size and achieving miniaturization of the electronic apparatus while maintaining image quality.
Implementation Method 1
pixels including photoelectric conversion sections that generate signal charges corresponding to amounts of light
Data Source
AI summary
An electronic apparatus includes: a pixel array section in which pixels including photoelectric conversion sections that generate signal charges corresponding to amounts of light, charge accumulation sections that receive the signal charges from the corresponding photoelectric conversion sections and that are shared thereby, and pixel transistors that read out the signal charges generated by the corresponding photoelectric conversion sections and that are shared thereby are two-dimensionally arranged in a matrix; a solid-state image capture device including a scanner that can drive the pixels so that exposure periods of all of the pixels are simultaneously started, that can drive the pixels so that the exposure periods of all of the pixels are simultaneously ended, and that sequentially selects and scans the pixels in readout periods; and a mechanical shutter that determines an end of the exposure periods for still-image shooting.