Imaging Device Charge Transfer Channels for High-Speed Operation
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Solution Overview
Problem
Conventional imaging devices face limitations in achieving high temporal resolution due to the time required for charge transfer from photodiodes to floating diffusion, which restricts their high-speed operation, especially in applications like fluorescence-lifetime imaging microscopy and time-of-flight methods.
Innovation Solution
The imaging device incorporates a photoelectric converter, multiple charge transfer channels, and charge accumulation units, along with control electrodes and transfer gates, allowing for independent control of charge transfer and accumulation, enabling faster operation without relying on the saturation speed of charge transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If charge is transferred from photodiodes to floating diffusion in conventional CMOS imaging devices, then charge accumulation and readout can be performed, but the transfer time limits the operating speed and temporal resolution
Solution Approach 1:
The pixel is divided into multiple independent photodiodes (first photodiode and second photodiode) with separate charge transfer channels. Each photodiode can independently transfer charge to its own floating diffusion, allowing parallel operation and eliminating the sequential transfer bottleneck that limits speed in conventional single-channel designs.
Solution Approach 2:
The invention transitions from a single charge transfer path to multiple parallel paths by introducing a second photodiode and second floating diffusion. This multi-dimensional charge transfer architecture enables simultaneous charge accumulation in multiple locations, effectively multiplying the throughput and reducing the time required for complete charge readout.
2Loss of time
If discharge gates are used to release charge from photodiodes, then reset time can be reduced, but the gate switching time still affects temporal resolution
Solution Approach 1:
The invention extracts and eliminates the discharge gate component from the pixel structure. By using direct charge transfer from photodiodes to floating diffusions without intermediate gate switching, the design removes the gate switching time bottleneck that previously limited temporal resolution, achieving faster operation without compromise.
3Productivity
If multiple charge transfer channels are implemented to increase throughput, then charge transfer efficiency improves, but device complexity increases
Solution Approach 1:
The invention merges the charge transfer functionality into the existing photodiode-float diffusion architecture by creating parallel identical structures rather than adding complex new components. Each photodiode-FD pair operates as an independent, simple unit, and their combined effect achieves high throughput without requiring complex control logic or additional gate structures.
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 enhances temporal resolution and allows for higher-speed operation, enabling improved detection capabilities in various imaging applications by distributing charge to accumulation units based on traveling distance and controlling potential gradients for efficient signal transfer.
Implementation Method 1
a photoelectric converter that generates charge
Data Source
AI summary
An imaging device includes a photoelectric converter that generates charge; a first charge transfer channel having a first end electrically connected to the photoelectric converter and a second end, and transferring the charge in a direction from the first end to the second end; a second charge transfer channel diverging from the first charge transfer channel at a first position and transferring a first part of the charge; a third charge transfer channel diverging from the first charge transfer channel at a second position different from the first position in the direction and transferring a part of the second part of the charge; and first and second charge accumulators that accumulate at least a part of the first and second part of the charge respectively. The imaging device does not include a gate that switches between cutoff and transfer of charge, in the first charge transfer channel.