Image Sensor Pixel Sharing Circuits for Noise Reduction
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Solution Overview
Problem
Existing image sensors face challenges in low light conditions due to signal noise from ambient light, reduced efficiency in space utilization, and limitations in applications requiring temporary signal storage, such as global shutters, especially in backside illumination sensors.
Innovation Solution
An image sensor design incorporating a pair of pixel sharing circuits with specific transistors and a control circuit that operates in different modes based on light intensity, allowing for improved signal-to-noise ratio and efficient space utilization by adjusting transistor states and light source usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal subtraction method is used to eliminate ambient light noise, then signal quality is improved, but time cost increases due to requiring multiple pictures to be taken
Solution Approach 1:
The patent uses a light source to pre-illuminate the scene before the main exposure, allowing the ambient light to be captured and subtracted in a controlled manner. This preliminary lighting action enables noise elimination without requiring multiple separate picture captures, thus reducing time cost while maintaining signal quality
2Area of stationary object
If single photo diode is used for multiple pixels to reduce redundant area, then space utilization efficiency is improved, but optical angle uniformity deteriorates
Solution Approach 1:
The patent divides the pixel array into multiple groups, with each group having its own dedicated photo diode. This segmentation approach ensures that each photo diode serves a specific region with uniform optical characteristics, maintaining optical angle uniformity while improving overall space utilization efficiency through systematic arrangement
3Measurement precision
If backside illumination structure is used to improve quantum efficiency, then light reception efficiency is improved, but shutter efficiency deteriorates due to ambient light affecting signal storage points
Solution Approach 1:
The patent introduces a light source as an intermediary element that provides controlled illumination before the main exposure. This intermediary lighting allows the backside illumination structure to maintain its high quantum efficiency while the light source's controlled timing and intensity enable effective shutter operation, preventing ambient light from degrading signal storage quality
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 enhances signal quality by reducing noise in high ambient light conditions and optimizes space utilization in low light scenarios, improving shutter efficiency and enabling effective image capture across varying light environments.
Implementation Method 1
The photon device is configured to receive optical energy and generate corresponding charge
Data Source
AI summary
An image sensor includes a pair of pixel sharing circuits, a second reset transistor, an amplifier transistor, a readout transistor and a control circuit. The pair of pixel sharing circuits connected to a floating diffusion node, each including a photon device, a first reset transistor, a capture transistor, a holding transistor, a capacitor and a sharing transistor. The control circuit is configured to control the first reset transistor, the first capture transistor, the first holding transistor and the sharing transistor of each of the pair of sharing pixel circuits to be turned on or off.