Image Sensor Nested Sub-pixels for Focus Detection
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Solution Overview
Problem
Existing image capture apparatuses with focus detection functions suffer from low light reception efficiency and image quality issues due to gaps between photo-electric conversion units, color purity degradation, and complex manufacturing processes when integrating phase difference schemes for focus detection.
Innovation Solution
The image sensor design incorporates focus detection sub-pixels and image capture sub-pixels with shifted light-receiving surfaces, allowing for simultaneous focus detection and high-quality image capture without generating unavailable pixels, using a Bayer arrangement and pn junction photodiodes with different semiconductor layers for color separation and improved light reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If divided photo-electric conversion units are arranged in one pixel for focus detection, then focus detection capability is improved, but light reception efficiency degrades due to gaps between units
Solution Approach 1:
The patent implements nesting by placing focus detection sub-pixels inside the pixel structure as overlapping or nested elements within the image capture sub-pixels. This allows focus detection functionality to be embedded within the image capture pixel without requiring separate dedicated pixels, thereby maintaining high light reception efficiency while enabling effective focus detection through the nested sub-pixel arrangement.
2Difficulty of detecting and measuring
If focus detection pixels are arranged in some areas, then focus detection is improved, but image capture resolution degrades due to unavailable pixels
Solution Approach 1:
The patent applies multi-functionality by designing each pixel to serve dual purposes: image capture sub-pixels capture image signals while focus detection sub-pixels perform focus detection. Both sub-pixel types contribute to their respective functions simultaneously, eliminating the need to sacrifice image capture pixels for focus detection and maintaining full image resolution while enabling effective focus detection across the entire sensor array.
3Difficulty of detecting and measuring
If color separation is performed using Si layer thickness difference, then focus detection and image capture are separated, but color purity degrades
Solution Approach 1:
The patent applies segmentation by dividing each pixel into distinct image capture sub-pixels and focus detection sub-pixels with separate light-receiving surfaces. This segmentation allows independent optimization of each sub-pixel type: image capture sub-pixels maintain full color sensitivity with color filters for high color purity, while focus detection sub-pixels use spectral absorbance differences for focus measurement, thereby resolving the contradiction between focus detection capability and color purity.
4Adaptability or versatility
If multiple sub-pixels are formed in one pixel for simultaneous focus detection and image capture, then functional versatility is improved, but device complexity increases
Solution Approach 1:
The patent applies merging by combining focus detection and image capture functionalities within a unified pixel structure. The image capture sub-pixels and focus detection sub-pixels share common pixel infrastructure including microlenses, color filters, and readout circuits, while maintaining separate light-receiving surfaces. This merged design achieves functional versatility for simultaneous focus detection and high-quality image capture without proportionally increasing device complexity, as the shared components reduce the overall structural burden.
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 achieves high-quality images and effective focus detection by optimizing light reception and color separation, reducing the complexity of manufacturing and enhancing the dynamic range while maintaining image resolution.
Implementation Method 1
one microlens and a plurality of divided photo-electric conversion units are formed in one pixel. The divided photo-electric conversion units receive light beams in different areas of the pupil of an imaging lens via one microlens
Implementation Method 2
one microlens and a plurality of divided photo-electric conversion units are formed in one pixel. The divided photo-electric conversion units receive light beams in different areas of the pupil of an imaging lens via one microlens
Implementation Method 3
because the wavelength of incident light is divided using a difference in spectral absorbance that depends on the thickness of the Si layer
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An image sensor in which each pixel includes a first sub-pixel including a first semiconductor layer, a second sub-pixel including a second semiconductor layer having a polarity different from a polarity of the first semiconductor layer, a third semiconductor layer having a polarity equal to the polarity of the first semiconductor layer, and a microlens, and which includes a plurality of pixels in which the first semiconductor is included in the second semiconductor layer, and the second semiconductor layer is included in the third semiconductor layer, wherein a center of gravity position of a light-receiving surface defining the first semiconductor layer is different from a center of gravity position of a light-receiving surface defining both the first semiconductor layer and the second semiconductor layer.