Image Sensor Storage Diode Segmentation for Light Leakage
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Solution Overview
Problem
CMOS-type global shutter image sensors experience light leakage due to diffraction and diffused reflection of incident light, causing charge accumulation and readout issues that lead to image gradation and performance deterioration, especially in low illuminance conditions.
Innovation Solution
The image sensor design includes a structure where Storage Diodes of adjacent pixels are arrayed symmetrically, with a shading curtain or micro lens configuration to prevent light leakage, and a phase difference auto focusing operation is performed based on charge accumulation in adjacent pixels, improving light collection efficiency and manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If charges are stored in Storage Diodes of all pixels simultaneously in a batch, then global shutter operation is achieved, but light leakage occurs from adjacent pixels to the Storage Diode
Solution Approach 1:
The pixel array is divided into multiple banks, and within each bank, Storage Diodes are arranged in a segmented pattern where every other pixel's Storage Diode is positioned at the same height level. This segmentation creates isolated charge storage zones that prevent lateral charge diffusion between adjacent pixels during simultaneous charge transfer, thereby eliminating light leakage while maintaining global shutter functionality.
Solution Approach 2:
Adjacent pixels are designed with asymmetric Storage Diode positioning - specifically, Storage Diodes of pixels at alternating positions are placed at different height levels. This asymmetric arrangement ensures that charge packets from adjacent pixels do not follow the same diffusion path, preventing cross-talk and light leakage between neighboring pixels during the charge transfer process.
2Object-affected harmful factors
If readout operation is performed sequentially for each pixel, then light leakage is reduced, but readout time increases significantly
Solution Approach 1:
By segmenting the pixel array into multiple banks with alternating Storage Diode height levels, the patent enables parallel charge transfer operations within each bank while maintaining isolation between adjacent pixels. This segmentation allows simultaneous readout of multiple pixels without causing light leakage, significantly reducing the time loss compared to sequential readout.
3Area of stationary object
If Storage Diodes of adjacent pixels are positioned close together, then device area is reduced, but charge diffusion between pixels increases
Solution Approach 1:
The patent employs asymmetric positioning of Storage Diodes in adjacent pixels, where every other pixel's Storage Diode is positioned at a different height level. This vertical asymmetry creates physical separation in the charge storage zones, preventing lateral charge diffusion between closely spaced adjacent pixels while maintaining compact device area.
Solution Approach 2:
The patent utilizes the vertical dimension (height level) to separate charge storage zones of adjacent pixels, rather than only relying on horizontal spacing. By positioning Storage Diodes at alternating height levels, the patent achieves three-dimensional charge isolation that prevents diffusion while allowing tight two-dimensional packing, thus reducing overall device area without increasing charge diffusion.
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 design effectively reduces light leakage, enhances light collection efficiency, simplifies phase difference auto focusing, and improves performance in low illuminance conditions by using a symmetrical Storage Diode arrangement and micro lens placement.
Implementation Method 1
a micro lens is arrayed in an area in which the Photo Diode of each of the plurality of pixels is arrayed
Implementation Method 2
a shading curtain is formed in an area in which the Storage Diodes of the plurality of pixels are arrayed to be adjacent to each other
Implementation Method 3
an image sensor which generates an image by electrically converting incident light admitted into a lens
Data Source
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AI summary
A photographing apparatus for preventing or reducing light leakage and an image sensor thereof are provided. The photographing apparatus includes an image sensor configured to include a plurality of pixels respectively having a Photo Diode and a Storage Diode for temporarily storing a charge accumulated in the Photo Diode and an image processor configured to perform an image processing operation by receiving the charge stored in the Storage Diode of each of the plurality of pixels. In addition, the image sensor has a structure where the Storage Diodes of the plurality of pixels are arrayed to be adjacent to each other. Accordingly, the photographing apparatus may prevent the light leakage from the adjacent pixel being flowed into a Storage Diode of each pixel.