Imaging-Plane Phase Difference AF Control Apparatus for Focusing Speed
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Solution Overview
Problem
Existing image capturing systems using imaging-plane phase difference AF face challenges in achieving accurate focusing due to the limitations of bandpass filtering, where low frequency bands can detect defocus in large blur states but reduce accuracy near the in-focus position, while high frequency bands improve accuracy near the in-focus position but fail to detect defocus in large blur states, leading to prolonged focusing times.
Innovation Solution
A control apparatus that acquires signals from different pupil regions of an image capturing optical system, performs multiple filtering processes with varying frequency bands to calculate multiple defocus amounts and reliabilities, and determines the appropriate defocus amount for focusing based on the differences between these calculations, allowing for precise control of the focus lens and limiting its drive range accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low frequency band filter is used to detect defocus amount, then defocus can be detected in large blur states, but focusing accuracy in the vicinity of the in-focus position deteriorates
Solution Approach 1:
The patent segments the frequency band into multiple bands (first frequency band and second frequency band) and processes image signals through separate filtering operations for each band. This allows independent optimization of defocus detection capability and focusing accuracy, resolving the contradiction between detecting large blur states and maintaining accuracy near in-focus position.
Solution Approach 2:
The patent dynamically switches between different frequency bands based on the current focusing state. When in large blur states, the low frequency band is used for reliable defocus detection. When approaching the in-focus position, the system transitions to the high frequency band to maintain high focusing accuracy. This dynamic adaptation resolves the contradiction by using the appropriate frequency band for each focusing stage.
2Measurement precision
If a high frequency band filter is used to improve focusing accuracy, then accuracy near the in-focus position improves, but the ability to detect defocus in large blur states deteriorates
Solution Approach 1:
The patent divides the frequency processing into separate channels with distinct frequency characteristics. The first frequency band is optimized for detecting large defocus amounts, while the second frequency band is optimized for high-precision focusing near the in-focus position. This segmentation allows each band to specialize in its strength without compromising the other.
Solution Approach 2:
The system dynamically selects which frequency band to use based on the current focusing condition. In large blur states, the low frequency band provides reliable defocus detection. As the focus lens approaches the in-focus position, the system switches to the high frequency band to maintain precision. This dynamic switching resolves the contradiction by adapting the frequency band to the current operational requirement.
3Device complexity
If only one frequency band is used for defocus amount calculation, then the processing is simple, but the focusing time increases due to inability to detect defocus in large blur states
Solution Approach 1:
The patent segments the filtering process into multiple parallel operations with different frequency bands. This allows simultaneous processing of different frequency components, enabling the system to detect defocus in large blur states using the low frequency band while maintaining the option to use the high frequency band for precision when needed. The parallel structure manages complexity effectively.
Solution Approach 2:
The patent performs preliminary filtering with multiple frequency bands in advance, preparing defocus amount calculations for different focusing scenarios before actual focusing occurs. This preliminary processing enables the system to quickly identify the appropriate frequency band and defocus amount without time-consuming real-time calculations, reducing overall focusing time.
Data Source
AI summary
A control apparatus includes an acquirer (204a) which acquires a first signal and a second signal that correspond to light beams passing through different pupil regions of an image capturing optical system, a calculator (204b) which performs a plurality of filtering processes with different bands for the first signal and the second signal to calculate a plurality of defocus amounts and reliabilities based on the first signals and the second signals where the respective filtering processes have been performed, and a determiner (209) which determines a defocus amount used for focusing from among the plurality of defocus amounts based on a difference between the plurality of defocus amounts and at least one of the plurality of reliabilities.