Focus Control Apparatus Using Segmented Phase-Difference Detection
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Solution Overview
Problem
Existing focus control methods for imaging devices, particularly in Live View and movie shooting modes, face challenges with unstable focus control due to increased pixel counts, leading to unnatural and blurred images.
Innovation Solution
A focus control apparatus and method that utilizes a lens device and imaging device configuration with a lens control unit and camera control unit communicating to adjust aperture and focusing lens positions, employing image-plane phase-difference AF with correlation computation to calculate defocus and reliability, and dynamically adjusting focus areas to maintain image stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel count is increased to improve image quality, then image resolution is improved, but focus control stability deteriorates
Solution Approach 1:
The image sensor is divided into multiple focus detection areas, each independently analyzing focus information. This segmentation allows the system to process focus data from different regions separately, reducing the impact of pixel count increases on overall focus control stability while maintaining high image resolution.
Solution Approach 2:
Different regions of the image sensor are assigned different functions: specific areas are dedicated to focus detection while other areas maintain high-resolution imaging capabilities. This local differentiation allows the system to optimize focus control in detection areas without compromising the overall image quality from the full sensor array.
2Measurement precision
If focus detection area is expanded to improve focus accuracy, then focus detection precision is improved, but focus control stability deteriorates
Solution Approach 1:
The focus detection function is segmented into multiple independent focus detection areas distributed across the image sensor. Each area performs focus detection locally, and the results are combined to achieve stable overall focus control. This prevents any single large detection area from causing instability while maintaining adequate detection precision.
Solution Approach 2:
Instead of using the entire image sensor for focus detection, only specific partial areas are dedicated to this function. This partial action approach provides sufficient focus detection precision while reducing the complexity and instability that would arise from using the full sensor area for focus analysis.
3Adaptability or versatility
If focus detection is performed in Live View mode to enable real-time focus adjustment, then operational versatility is improved, but focus control stability deteriorates
Solution Approach 1:
The image sensor serves multiple functions simultaneously: it performs both high-resolution imaging and focus detection in Live View mode. By integrating focus detection capabilities into the main image sensor rather than using a separate dedicated sensor, the system achieves operational versatility without compromising focus control stability.
Solution Approach 2:
During Live View operation, the sensor output is segmented into imaging data and focus detection data. Specific regions or pixel groups are analyzed for focus information while the rest of the sensor continues full-resolution imaging, allowing real-time focus adjustment without destabilizing the overall focus control system.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An acquisition unit (207) is configured to acquire first defocus information based on a sensor output corresponding to a first region in an area of a captured image, and to acquire second defocus information based on a sensor output corresponding to a second region in the area. A control unit (204) is configured to obtain defocus information corresponding to the area using the first defocus information and the second defocus information, and to perform focus control based on the obtained defocus information. The first region has a length longer in a phase-difference detection direction than the length of the second region.