Depth-Segmented Pixel Array for Focus Detection and Higher Saturation Charge
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Solution Overview
Problem
Existing image sensors face challenges in increasing saturation charge amount while maintaining the number of pupil division directions for focus detection, leading to high manufacturing costs and reduced light receiving area due to the use of transfer transistors or complex vertical transfer transistors.
Innovation Solution
The image sensor design incorporates a pixel array with two photodiodes at different depths and connecting regions, allowing for efficient signal charge transfer and accumulation, enabling increased saturation charge while maintaining two pupil division directions for focus detection without the need for complex transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transfer transistor is provided for each photoelectric conversion portion, then signal charge transfer is enabled, but the number of transistors increases and the light receiving area becomes small
Solution Approach 1:
Multiple photoelectric conversion portions share a common charge storage unit instead of each having its own transfer transistor. The patent combines the charge storage function into a shared region where signal charges from multiple photodiodes are accumulated and transferred together, eliminating the need for individual transfer transistors and increasing the light receiving area.
Solution Approach 2:
The common charge storage unit serves multiple functions: it stores signal charges from multiple photoelectric conversion portions, enables charge transfer, and supports both imaging and focus detection functions. This multi-functional design replaces multiple specialized transistors with a single shared structure.
2Measurement precision
If photoelectric conversion portions are formed at different depths, then color mixing of phase difference detection signal is suppressed, but the device complexity increases
Solution Approach 1:
The photoelectric conversion portions are segmented into different depth levels within the semiconductor substrate. First photodiodes are formed at a first depth and second photodiodes at a second depth, allowing wavelength-specific photoelectric conversion without requiring complex transistor structures. This spatial segmentation enables color separation through depth rather than through complex circuitry.
3Reliability
If the number of pupil division directions is maintained at two, then focus detection capability is preserved, but the saturation charge amount is limited
Solution Approach 1:
The patent adds a depth dimension to the photoelectric conversion structure by forming photodiodes at different depths within the semiconductor substrate. This third dimension (depth) allows increased charge storage capacity without compromising the two-pupil-division focus detection capability, as the depth separation enables both charge accumulation and optical path differentiation.
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 the saturation charge amount and reduces manufacturing costs by simplifying the transistor process, enabling effective focus detection with improved image data quality without interpolation processing.
Implementation Method 1
photoelectric conversion portions formed at different depths to photoelectrically convert visible light in different wavelength ranges
Data Source
Figure 1~2
Figure 3
Figure 4A~4C
AI summary
An image sensor comprising a plurality of microlenses, and a pixel array having, with respect to each of the microlenses, a pair of first regions formed at a first depth from a surface on which light is incident, a pair of second regions formed at a second depth deeper than the first depth, and a plurality of connecting regions that connects the pair of first regions and the pair of second regions, respectively. A direction of arranging the pair of second regions corresponding to each microlens is a first direction, and a direction of arranging the pair of first regions is either the first direction or a second direction which is orthogonal to the first direction.