Distance Sensor Pixel With Segmented Photosensor For 3D Imaging
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Solution Overview
Problem
Current image sensors, particularly those used in portable devices, face challenges in achieving high sensitivity and demodulation contrast for accurate distance measurement and 3D imaging, especially when employing time-of-flight methods.
Innovation Solution
The design of a pixel sensor for distance sensors includes a photosensor with increasing cross-sectional area and pinning voltage along specific directions, featuring a 2-tap structure with transfer gates and a pinning layer, which accelerates photocharges and enhances demodulation contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the photosensor cross-sectional area is increased to improve sensitivity and fill factor, then sensitivity and fill factor are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The photosensor is divided into multiple segments along the light-receiving direction, with each segment having a different cross-sectional area. This segmentation allows the sensor to capture photons at different depths while maintaining a manageable structural complexity, resolving the contradiction between improved sensitivity and device complexity.
Solution Approach 2:
The patent introduces a depth dimension to the photosensor structure by varying the cross-sectional area along the light-receiving direction. This dimensional approach enables enhanced sensitivity through multi-depth photon capture without proportionally increasing lateral complexity, effectively resolving the contradiction between sensitivity and device complexity.
2Area of stationary object
If the photosensor cross-sectional area is increased to improve fill factor, then fill factor is improved, but manufacturing precision requirements increase
Solution Approach 1:
The photosensor area is segmented into multiple depth layers with varying cross-sectional areas. This segmentation achieves a high overall fill factor by utilizing vertical space while maintaining manufacturability through standardized layer fabrication processes, resolving the contradiction between fill factor and manufacturing precision.
Solution Approach 2:
The patent exploits the depth dimension to increase the effective photosensor area without proportionally increasing lateral dimensions. By varying cross-sectional area along the light-receiving direction, the design achieves high fill factor while maintaining manageable manufacturing precision requirements through vertical rather than lateral scaling.
3Measurement precision
If transfer gates are added to accelerate photocharge transfer, then sensitivity and demodulation contrast are improved, but device complexity increases
Solution Approach 1:
The transfer gate structure is segmented and integrated directly within the photosensor regions. This segmentation allows photocharges from different depth segments to be transferred efficiently with minimal lateral movement, improving demodulation contrast while keeping the overall device complexity manageable through localized transfer mechanisms.
Solution Approach 2:
The transfer gates are merged with the photosensor structure rather than being separate components. This integration combines the photocharge generation and transfer functions into a unified structure, improving sensitivity and demodulation contrast while reducing device complexity by eliminating separate transfer mechanisms.
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 improves the sensitivity and demodulation contrast of the pixel sensor, enabling more accurate distance calculations and maintaining high fill factor and resolution, suitable for portable electronic devices like smartphones.
Implementation Method 1
a photosensor arranged to generate photocharges corresponding to light incident in a first direction
Data Source
AI summary
A pixel of a distance sensor includes a photosensor that generates photocharges corresponding to light incident in a first direction. The photosensor includes a plurality of first layers having a cross-sectional area increasing along the first direction after a first depth and at least one transfer gate which receives a transfer control signal for transferring the photocharges to a floating diffusion node. A strong electric field is formed in the direction in which the photocharges move horizontally or vertically in the pixel, thereby accelerating the photocharges, allowing for increased sensitivity and demodulation contrast.