3D Image Sensor Pixel Array with Shared Ambient Light Cancellation
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Solution Overview
Problem
Three-dimensional image sensors face challenges in efficiently reducing ambient light components and maintaining a small size while effectively measuring object distances, particularly in varying illuminance conditions.
Innovation Solution
The implementation of a pixel array with a shared ambient light cancellation circuit and depth pixels that operate in response to photo control signals with different phases, allowing for efficient removal of ambient light and improved distance measurement performance through phase interpolation and various operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If each depth pixel has a dedicated ambient light cancellation circuit, then ambient light removal performance is improved, but device size and complexity increase
Solution Approach 1:
Multiple depth pixels share a common ambient light cancellation circuit instead of each pixel having its own dedicated circuit. This merging approach reduces the overall number of circuits in the pixel array, decreasing device complexity and size while still maintaining effective ambient light removal capability through shared resource utilization.
Solution Approach 2:
The ambient light cancellation circuit is designed as a universal component that can serve multiple depth pixels simultaneously. This multi-functional circuit performs the same ambient light removal function for different pixels, reducing redundancy and simplifying the overall pixel array structure while maintaining measurement precision.
2Measurement precision
If more depth pixels are used to improve distance measurement accuracy, then measurement precision is improved, but device area increases
Solution Approach 1:
Adjacent depth pixels are grouped and merged to share common circuits including ambient light cancellation circuits and readout pathways. This merging allows the pixel array to achieve higher measurement precision through multiple pixels while containing the area increase by efficient spatial arrangement and shared infrastructure.
3Measurement precision
If phase interpolation is performed to improve distance measurement in low illuminance, then measurement precision is improved, but calculation complexity increases
Solution Approach 1:
Phase interpolation calculations are performed during the signal processing stage after photo charge collection, rather than requiring complex real-time processing during illumination. This preliminary calculation approach improves low illuminance measurement precision while managing complexity by utilizing processed data from multiple phases.
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 enables efficient ambient light cancellation and improved distance measurement performance in three-dimensional image sensors, enhancing their operational efficiency across different illuminance conditions.
Implementation Method 1
The photoelectric conversion region collects photo charges based on the light reflected by the object
Data Source
AI summary
A pixel array in a three-dimensional image sensor includes depth pixels and an ambient light cancellation (ALC) circuit. The depth pixels operate in response to photo control signals having different phases, and generate distance information of an object based on light reflected by the object. The ALC circuit removes an ambient light component from the reflected light, and is shared by the depth pixels. Each depth pixel includes a photoelectric conversion region, a floating diffusion region, a photo gate, and a drain gate. The photoelectric conversion region collects photo charges based on the reflected light. The floating diffusion region accumulates the photo charges. The photo gate is activated in response to one of the photo control signals. The photoelectric conversion region accumulates the photo charges when the photo gate is activated, and the photo charges in the photoelectric conversion region are released when the drain gate is activated.