Image Sensor Pixel Layout for Edge Shading and Dynamic Range
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Solution Overview
Problem
In photoelectric conversion systems, shading occurs due to incident light not being concentrated on the center of pixels at the outer edge of the pixel area, leading to a decrease in light amount and reduced dynamic range.
Innovation Solution
The system includes a pixel area with pixels arranged such that each pixel has a first conversion unit and a second conversion unit surrounding it, with a transistor area for processing signals from both units. The planar distance between the first conversion unit and the transistor area in pixels closer to the edge is longer than in central pixels, and the first conversion unit is eccentric relative to the second conversion unit to optimize light reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pixels are arranged with the first conversion unit at the center of the second conversion unit, then the structure is simple and manufacturing is easy, but shading occurs at pixel edges where light is not concentrated on the center
Solution Approach 1:
The patent applies local quality by differentiating the positioning of the first conversion unit based on pixel location. In pixel area outer edge portions, the first conversion unit is positioned at an off-center location to receive concentrated light, while in other regions it may be centered. This localized adjustment resolves the contradiction between structural simplicity and light concentration at edges.
Solution Approach 2:
The patent introduces asymmetry in the positioning of the first conversion unit relative to the second conversion unit in edge pixels. Instead of maintaining symmetric central positioning, the first conversion unit is deliberately offset to align with the concentrated light path, thereby eliminating shading effects while maintaining manufacturing feasibility.
2Illumination intensity
If the first conversion unit is positioned to receive concentrated light at pixel edges, then shading is reduced, but the planar distance to the transistor area increases
Solution Approach 1:
The patent applies local quality by adjusting the positioning of the first conversion unit based on pixel location. In pixel area outer edge portions where light concentration is critical, the first conversion unit is positioned offset from the center to receive concentrated light, accepting the increased distance to the transistor area. In other regions, the standard centered positioning is maintained, thus resolving the contradiction locally where it matters most.
3Device complexity
If a single photoelectric conversion unit is used per pixel, then the device structure is simple, but the dynamic range is limited
Solution Approach 1:
The patent merges two photoelectric conversion units (first and second conversion units) within each pixel to expand the dynamic range. The first conversion unit has a smaller light receiving area and the second has a larger area, allowing them to capture different light intensity ranges. Their signals are combined to achieve a wider dynamic range while maintaining a relatively simple device structure.
Solution Approach 2:
The patent implements a nested structure where the first conversion unit is positioned within the area of the second conversion unit. This nested arrangement allows both conversion units to coexist in a compact space, expanding functional capability (dynamic range) without proportionally increasing device complexity.
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 enhances light reception and reduces shading, allowing for an expanded dynamic range without the need for shading correction coefficients, thereby improving image quality and reducing power consumption.
Implementation Method 1
a first conversion unit, a second conversion unit surrounding the first conversion unit, and a transistor area provided with a circuit configured to process a signal based on a charge generated in the first conversion unit and the second conversion unit
Data Source
AI summary
An apparatus including a pixel area including a plurality of pixels arranged in the pixel area, the apparatus includes a first pixel of the plurality of pixels, and a second pixel arranged at a position closer to an edge of the pixel area than the first pixel, wherein each of the first pixel and the second pixel includes a first conversion unit, a second conversion unit surrounding the first conversion unit, and a transistor area provided with a circuit configured to process a signal based on a charge generated in the first conversion unit and the second conversion unit, and wherein a planar distance between the first conversion unit and the transistor area in the second pixel is longer than a planar distance between the first conversion unit and the transistor area in the first pixel.