Phase-Difference Autofocus Control Under Readout Time Mismatch
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Solution Overview
Problem
Existing image pickup apparatuses using imaging-surface phase-difference detection methods face challenges in maintaining focus detecting accuracy due to large readout time differences in correlation directions, particularly under conditions of high object movement, low shutter speeds, dark F-numbers, and bright object luminance, which degrade focus detection performance.
Innovation Solution
The apparatus employs an image sensor with pixels that convert light beams through different pupil areas, performing sequential signal readout in two directions and utilizing a processor to detect phase differences in both directions, with adaptive processing based on shutter speed and F-number to optimize focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If focus detection is performed in both first and second pupil division directions, then focus detecting performance is improved, but readout time difference in correlation direction increases causing focus detecting accuracy to degrade
Solution Approach 1:
The patent dynamically selects between first detection (first pupil division direction) and second detection (second pupil division direction) based on imaging conditions such as shutter speed and object movement. The processor adaptively determines which detection method to use, making the system flexible rather than static, thereby resolving the contradiction between maintaining focus detecting performance and avoiding accuracy degradation from readout time differences
Solution Approach 2:
The patent changes the detection parameters (which pupil division direction to use) based on imaging conditions. When shutter speed is fast or object movement is large, the system switches to first detection; when shutter speed is slow and object movement is small, it uses second detection. This parameter-based adaptation resolves the technical contradiction by optimizing the detection method for each specific imaging scenario
2Reliability
If second detection is performed under high-speed readout conditions, then focus detecting performance is maintained, but readout time difference becomes large causing accuracy to decrease
Solution Approach 1:
The patent implements a feedback mechanism where the processor continuously monitors imaging conditions (shutter speed, object movement) and adjusts the detection method accordingly. This feedback loop ensures that when readout time difference becomes problematic, the system automatically switches to the appropriate detection method, preventing accuracy degradation while maintaining focus detecting performance
3Ease of operation
If detection is performed in correlation direction with large readout time difference, then focus detection can be achieved, but error due to time difference is superimposed on focus detecting signal
Solution Approach 1:
The patent extracts and separates the two detection methods (first detection and second detection) into distinct processing paths. By taking out the problematic second detection path and creating a separate first detection path that avoids the readout time difference issue, the system can select the appropriate path based on conditions, thereby preventing error superposition on the focus detecting signal
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 approach enhances focus detection accuracy by selectively using the most reliable detection results, reducing errors caused by readout time differences and maintaining consistent focus performance across varying imaging conditions.
Implementation Method 1
an image sensor configured to capture an object is used as a focus detecting sensor
Data Source
AI summary
An image pickup apparatus includes an image sensor, and a processor that configured to detect a phase difference between a pair of detection signals generated by signals read out of at least a part of pixels, perform a first detection for detecting the phase difference in the first direction and a second detection for detecting the phase difference in the second direction, perform first processing for acquiring the information by the first detection or the second detection in a case where a shutter speed including a period during which the pair of detection signals are generated is longer than a predetermined time, perform second processing for acquiring the information by the first detection irrespective of the second detection in a case where the shutter speed is shorter than the predetermined time, and set the predetermined time to be longer as an F-number of the optical system is larger.