Dual Conversion Gain Transistor for Image Sensor Noise
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Solution Overview
Problem
Current image sensing devices face challenges in producing high-quality images in varying illuminance environments, particularly in low-light conditions due to noise robustness and dynamic range limitations.
Innovation Solution
The implementation of a dual conversion gain transistor in the image sensing device, which adjusts signal gains based on light levels, allowing for improved noise robustness and dynamic range by amplifying signals in low-light conditions and reducing noise through variable gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual conversion gain transistor is added to adjust signal gains based on light levels, then noise robustness and dynamic range are improved, but device complexity increases
Solution Approach 1:
The dual conversion gain transistor serves multiple functions: it acts as a conversion gain transistor for first pixel groups and as a dual conversion gain transistor for second pixel groups. This multi-functionality allows the same transistor structure to provide adaptive gain control for different pixel types, improving noise robustness without proportionally increasing device complexity
Solution Approach 2:
The transistor dynamically adjusts its conversion gain based on incident light levels. In high illuminance conditions, it provides lower gain to prevent saturation, while in low illuminance conditions, it provides higher gain to improve signal-to-noise ratio. This dynamic adaptation resolves the contradiction by making the device more reliable without requiring separate fixed-gain circuits for different lighting conditions
2Adaptability or versatility
If a dual conversion gain transistor is added to expand dynamic range, then image quality in varying illuminance is improved, but device complexity increases
Solution Approach 1:
The same transistor structure is used universally across different pixel groups, serving both as a standard conversion gain transistor and as a dual conversion gain transistor depending on the pixel group type. This universal design enables expanded dynamic range coverage without requiring entirely separate circuit paths for different illuminance conditions
Solution Approach 2:
Different pixel groups are assigned different operational modes: first pixel groups use the transistor in a standard conversion gain mode, while second pixel groups use it in a dual conversion gain mode. This local differentiation allows each pixel group to have optimized characteristics for its specific illuminance range, thereby expanding overall dynamic range while maintaining a relatively simple unified transistor design
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 solution enhances image quality by providing robustness to noise in low-illuminance areas and expanding the dynamic range without introducing separate capacitive elements, thus improving the overall performance of the image sensing device across different lighting conditions.
Implementation Method 1
each imaging pixel structured to detect incident light and to generate a pixel signal
Data Source
AI summary
An image sensing device includes a Bayer pixel group configured include pixels that form a Bayer pattern and are arranged in a 2×2 matrix, a 4SUM pixel group configured to include pixels that correspond to the same colors and are arranged in a 2×2 matrix, a Bayer floating diffusion disposed at a center portion of the Bayer pixel group, a 4SUM floating diffusion (FD) region disposed at a center portion of the 4SUM pixel group, a sensing node, and a gain conversion transistor coupled between the sensing node and any one of the Bayer floating diffusion (FD) region and the 4SUM floating diffusion (FD) region.