Image Sensor Pixel Array for Phase Detection Autofocus
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Solution Overview
Problem
Current image sensors face challenges in achieving high frame rates and fast autofocus speeds while maintaining accurate focus detection, particularly in phase difference autofocus techniques, where the focus detection speed and accuracy are limited by the design of focus detection pixels and image detection pixels.
Innovation Solution
The image sensor design incorporates a pixel array with microlenses and pairs of photoelectric conversion elements arranged in parallel, where a row decoder controls the output of image signals and sum image signals from each pixel, allowing for sequential readout and analog-to-digital conversion, enabling the generation of autofocus data based on phase detection signals from adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase difference autofocus detection is performed on each pixel or certain adjacent pixels, then focus detection accuracy is improved, but focus detection speed is reduced
Solution Approach 1:
Each pixel is divided into multiple photoelectric conversion elements (e.g., first and second photoelectric conversion elements) that can independently perform phase difference detection. This segmentation allows parallel processing of focus detection across multiple pixels simultaneously, improving both accuracy and speed.
Solution Approach 2:
The patent introduces a temporal dimension by sequentially reading out image signals and sum signals from different pixels at different time periods. This allows focus detection data from multiple pixels to be collected and processed without interfering with each other, resolving the speed-accuracy tradeoff.
2Productivity
If high frame rate readout is implemented, then productivity is improved, but autofocus accuracy is reduced
Solution Approach 1:
The patent merges image signal readout and sum signal readout into a unified readout process. By controlling the same pixel to output both types of signals in sequence during different time periods, the system maintains high frame rate while ensuring accurate autofocus data collection through the sum signal.
Solution Approach 2:
The readout process is organized into periodic time periods where specific pixels are controlled to output image signals during first time periods and sum signals during second time periods. This periodic action allows systematic collection of both image and autofocus data at high speed.
3Adaptability or versatility
If focus detection pixels are separated from image detection pixels, then autofocus function is enabled, but device complexity increases
Solution Approach 1:
Each pixel is designed with multiple photoelectric conversion elements that can serve dual purposes: generating image signals for image detection and generating sum signals for autofocus detection. This multi-functionality eliminates the need for separate focus detection pixels, reducing overall device complexity while maintaining autofocus capability.
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 enhances autofocus speed and accuracy by allowing for high-speed readout of image signals and sum signals from each pixel, improving frame rate and enabling highly accurate autofocus data generation, thus facilitating faster and more precise autofocus functions in image sensors.
Implementation Method 1
each pixel of the plurality of pixels including a microlens, a first photoelectric conversion element, and a second photoelectric conversion element
Data Source
AI summary
An image sensor includes a pixel array including a plurality of pixels arranged in a matrix, each of the pixels including a microlens, a first photoelectric conversion element, and a second photoelectric conversion element, the first and second photoelectric conversion elements being arranged parallel with each other in a first direction below the microlens; and a row decoder configured to control a first image signal generated by the first photoelectric conversion element and a sum image signal generated by the first and second photoelectric conversion elements to be sequentially output from a first pixel in a first row of the pixel array during a first readout period, and to control a second image signal generated by the second photoelectric conversion element and the sum image signal to be sequentially output from a second pixel in a second row of the pixel array during a second readout period.