Image Sensor AF Pixel Group Layout for High-Speed Focus Detection
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Solution Overview
Problem
Existing image sensors face challenges in quickly performing auto focusing (AF) functions, which are crucial for capturing images accurately and efficiently in various applications, including digital cameras and security devices.
Innovation Solution
The image sensor incorporates a pixel array with both image pixel groups and AF pixel groups, connected through specific transmission control signal lines, allowing for high-resolution and high-speed AF operations by adjusting the activation timing of pixels within these groups to generate phase signals for focus detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a pixel array includes both image pixel groups and AF pixel groups with separate transmission control signal lines, then the auto focusing speed and resolution are improved, but the device complexity increases
Solution Approach 1:
The pixel array is segmented into distinct image pixel groups and AF pixel groups, each with dedicated transmission control signal lines. This segmentation allows independent control of imaging and auto-focusing operations, enabling high-speed AF by selectively activating only AF pixels during focus detection without affecting the entire pixel array, thus improving speed while managing complexity through functional separation.
Solution Approach 2:
The transmission control signal lines are designed to dynamically control the activation timing of different pixel groups. During AF operations, only AF pixel groups are activated with specific timing, while during imaging operations, image pixel groups are activated. This dynamic control optimizes performance for different modes and allows the system to adapt its complexity based on operational requirements.
2Measurement precision
If multiple transmission control signal lines are used for different pixel groups, then the measurement precision for phase difference detection is improved, but the manufacturing complexity increases
Solution Approach 1:
The signal line architecture is segmented into dedicated lines for different pixel groups (first transmission control signal line for image pixels, second transmission control signal line for AF pixels). This segmentation simplifies the manufacturing process by providing clear routing guidelines and reducing the complexity of signal distribution, while still enabling precise phase difference measurement through dedicated control paths.
Solution Approach 2:
The transmission control signal lines act as intermediaries that mediate between the control logic and the pixel groups. By introducing these dedicated intermediary signal lines, the system achieves precise control over pixel activation timing for phase difference detection, while the intermediary nature of these lines simplifies the overall control architecture and manufacturing process.
3Productivity
If AF pixel groups are electrically separated from image pixel groups, then the auto focusing function speed is improved, but the device complexity increases
Solution Approach 1:
The pixel array is segmented into electrically independent image pixel groups and AF pixel groups with separate transmission control signal lines. This segmentation enables the AF function to operate independently and simultaneously with imaging operations, improving productivity by allowing parallel operations and rapid focus switching without interfering with the main imaging pipeline.
Solution Approach 2:
The pixel array structure is designed with multi-functionality, where the same physical pixel array can serve both imaging and auto-focusing functions through electrical separation and selective activation. The AF pixel groups can be used for focus detection while image pixel groups handle imaging, and both functions can coexist and switch rapidly, achieving universal functionality that improves operational efficiency.
Data Source
AI summary
An image sensor according to an example embodiment include a plurality of image pixel groups, a plurality of auto focusing (AF) pixel groups, a first transmission control signal line connected to a first pixel of each of the plurality of image pixel groups, a second transmission control signal line connected to a second pixel of each of the plurality of image pixel groups, a third transmission control signal line connected to a first pixel of each of the plurality of AF pixel groups, and a fourth transmission control signal line connected to a second pixel of each of the plurality of AF pixel groups, wherein the fourth transmission control signal line is electrically separated from the first to the third transmission control signal line, and the each of the plurality of image pixel group and the plurality of AF pixel groups are disposed below a single microlens.