Hybrid Autofocus Method Using Distance and Phase Detection Sensors
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Solution Overview
Problem
Portable electronic devices, such as smartphones and tablets, face challenges in implementing effective auto-focus methods due to their compact size, which limits the use of optical zoom lenses and requires faster auto-focus procedures.
Innovation Solution
A hybrid auto-focus method that combines distance sensor auto-focus (DSAF) and phase detection auto-focus (PDAF) modes for a coarse search, followed by contrast detection auto-focus (CDAF) for a fine search, utilizing data from both distance sensors and image sensors to efficiently determine the optimal focusing lens position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a conventional auto-focus method is used in portable electronic devices, then the device structure remains simple, but the auto-focus time is too long (around 800ms) which degrades user experience
Solution Approach 1:
The patent segments the auto-focus process into two distinct stages: a coarse search phase using DSAF/PDAF methods to quickly locate the approximate focus position, and a fine search phase using CDAF to precisely determine the optimal focus position. This segmentation allows each stage to use the most appropriate method for its specific task, significantly reducing overall auto-focus time while maintaining system feasibility in portable devices.
Solution Approach 2:
The patent applies preliminary action by using the distance sensor to obtain initial distance information before the auto-focus search begins. This pre-acquired distance data is used to set the search range and initial focus position, allowing the lens to start the search from a more accurate starting point rather than scanning the entire range, thereby reducing the time required for both coarse and fine search phases.
2Manufacturing precision
If optical zoom lenses are used to improve imaging quality, then the imaging quality improves, but the lens becomes too heavy and requires more physical depth than portable devices can permit
Solution Approach 1:
The patent replaces the mechanical/optical approach of using large aperture lenses and optical zoom with a hybrid sensor-based auto-focus system. By utilizing distance sensors and phase detection capabilities embedded in the image sensor, the system achieves fast and accurate focusing without requiring heavy optical zoom lenses or large physical lens movements, thus maintaining imaging quality while reducing weight and device size.
3Speed
If the maximum aperture of the lens is increased to speed up auto-focus, then the auto-focus speed improves, but the lens structure becomes more complex and larger
Solution Approach 1:
The patent introduces distance sensors and phase detection pixels as intermediary elements that provide focus distance information to the auto-focus system. These intermediaries enable the system to determine the optimal focus position without requiring the lens to perform extensive scanning or use large aperture mechanisms, thereby achieving fast auto-focus speed while keeping the lens structure simple and suitable for portable devices.
Data Source
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AI summary
The disclosure proposes an auto-focus method and an image capturing device including a distance sensor and an image sensor having a lens and a sensing array. The method includes the following steps. First, distance sensor data and phase detection data are respectively obtained from the distance sensor and the sensing array. The lens is controlled to perform a course search within a focusing range by switching between a distance sensor auto-focus mode and a phase detection auto-focus mode based on the distance sensor data and the phase detection data so as to determine a fine-search range. The lens is further controlled to perform a fine search within the fine-search range in a contrast detection auto-focus mode so as to determine an optimal focusing lens position. Next, the lens is controlled to move to the optimal focusing lens position.