Image Sensor Pixel Division for Focus Detection
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Solution Overview
Problem
Existing image sensors with focus detection pixels face issues due to imbalance in optical characteristics caused by transfer gate electrodes, leading to undesirable horizontal stripes in captured images, especially when pixel division positions vary with image height.
Innovation Solution
The design incorporates a pixel structure with multiple pixel groups, each having photoelectric conversion portions with different division boundaries that adjust according to image height, ensuring balanced light reception and reducing the influence of transfer gate electrodes on image quality, allowing for accurate focus detection across a broader range of pupil distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel division positions are varied with image height to improve focus detection accuracy, then focus detection precision is improved, but imbalance in optical characteristics is caused leading to horizontal stripes in captured images
Solution Approach 1:
The patent applies local quality by making the photoelectric conversion portions have different division positions specifically in pixel groups at different image heights (peripheral pixels vs central pixels), while keeping the transfer gate electrode structure uniform across all pixels. This localized differentiation in photoelectric conversion portion arrangement allows optimal focus detection at each image height region without causing horizontal stripe artifacts, as the transfer gate electrodes maintain consistent optical characteristics throughout the sensor.
2Ease of operation
If transfer gate electrodes are used to transfer electric charges from photoelectric conversion portions, then charge transfer function is achieved, but light shielding effect causes imbalance in light receiving amount
Solution Approach 1:
The patent applies parameter changes by adjusting the positional parameters of the photoelectric conversion portions relative to the transfer gate electrodes. Specifically, at peripheral image heights where the chief ray angle is larger, the photoelectric conversion portions are positioned to compensate for the light shielding effect of the transfer gate electrodes, ensuring that the effective light receiving area remains balanced across all pixel groups despite the presence of light-shielding transfer gate structures.
3Adaptability or versatility
If multiple pixel groups with different division positions are implemented, then focus detection across broader pupil distances is enabled, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the pixel array into multiple pixel groups according to image height regions (central region and peripheral regions), where each group has photoelectric conversion portions arranged with different division positions. This segmentation allows the sensor to handle different pupil distance ranges optimally for different sensor regions, achieving broad focus detection capability while maintaining a relatively simple and uniform transfer gate electrode structure across all pixels.
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 approach effectively reduces the impact of transfer gate electrodes on image quality, enabling more accurate focus detection and minimizing horizontal stripes, while allowing for flexible focus detection across varying pupil distances and image heights.
Implementation Method 1
a plurality of photoelectric conversion portions; and a plurality of transfer gates that respectively correspond to the photoelectric conversion portions
Data Source
AI summary
An image sensor comprising a pixel portion that is constituted by a plurality of pixels, and includes a first pixel group and a second pixel group, wherein each of the pixels included in the first pixel group and the second pixel group includes: a plurality of photoelectric conversion portions; and a plurality of transfer gates that respectively correspond to the photoelectric conversion portions, and have transfer gate electrodes covering same partial regions in the photoelectric conversion portions, and an average position of barycenters of respective light receivable regions of the photoelectric conversion portions included in each pixel of the first pixel group and an average position of barycenters of respective light receivable regions of the photoelectric conversion portions included in each pixel of the second pixel group are at positions different from each other in the pixels.