CMOS Imaging Pixel Voltage Circuit for Compact Endoscopes
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Solution Overview
Problem
Existing imaging devices, particularly CMOS imagers, require a negative voltage to improve pixel characteristics, necessitating external negative voltage generation circuits, which are complex and hinder miniaturization.
Innovation Solution
The imaging device operates using a power source voltage and a reference voltage lower than the ground voltage, with a voltage generation circuit generating a positive voltage higher than the reference but lower than the power source voltage, eliminating the need for a negative voltage and its generation circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative voltage generation circuit is added to provide negative voltage to the gate electrode, then pixel characteristics such as dark current are improved, but device complexity increases and miniaturization is hindered
Solution Approach 1:
The invention extracts the negative voltage generation function from a separate external circuit and integrates it into the power source circuit itself. The power source circuit now directly outputs both positive voltage (for the well) and negative voltage (for the gate electrode), eliminating the need for a dedicated negative voltage generation circuit and its associated complexity.
Solution Approach 2:
The invention merges the negative voltage generation function with the power source circuit. Instead of having separate circuits for positive voltage supply and negative voltage generation, both functions are combined in a single power source circuit, reducing overall device complexity while maintaining the required pixel characteristics.
2Reliability
If a negative voltage generation circuit is added to provide negative voltage to the gate electrode, then pixel characteristics such as dark current are improved, but the device size increases
Solution Approach 1:
The invention removes the separate negative voltage generation circuit from the device architecture and integrates its functionality into the existing power source circuit. This extraction and integration approach eliminates the additional space that would be required for a dedicated negative voltage generation circuit, enabling device miniaturization while preserving improved pixel characteristics.
Solution Approach 2:
By merging the negative voltage generation capability into the power source circuit, the invention reduces the total device volume. The combined circuit occupies less space than separate circuits would require, facilitating miniaturization of the imaging device while maintaining the enhanced pixel performance.
3Reliability
If a negative voltage generation circuit is added, then the pixel can operate with improved characteristics, but noise increases
Solution Approach 1:
The invention extracts the voltage generation functions and consolidates them in a single power source circuit, which can be designed with optimized noise characteristics. This centralized approach allows for better noise control compared to multiple separate circuits, reducing the overall noise generated in the pixel operation.
Solution Approach 2:
By merging the positive and negative voltage generation into a single power source circuit, the invention reduces the number of circuit interfaces and potential noise sources. The unified circuit design enables better shielding and grounding strategies, thereby reducing noise while maintaining improved pixel characteristics.
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 reduces noise, increases charge storage, and enables miniaturization by eliminating the need for a negative voltage generation circuit, enhancing the imaging device's performance and suitability for applications like endoscopes.
Implementation Method 1
The photodiode is configured to generate an electric charge through photoelectric conversion
Data Source
AI summary
An imaging device includes a pixel and a voltage generation circuit. The pixel is configured to operate based on a power source voltage and a reference voltage that is lower than the power source voltage and is higher than or equal to a ground voltage. The voltage generation circuit is configured to generate a predetermined positive voltage that is higher than the reference voltage and is lower than the power source voltage. A transfer transistor of the pixel is formed on a well. The predetermined positive voltage is applied to the well. The transfer transistor is configured to operate based on the power source voltage and the reference voltage.