CMOS Focus Detection Control for Flicker-Affected Live View
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Solution Overview
Problem
Existing image pickup apparatuses using CMOS sensors experience flicker issues, particularly in environments with high-frequency digital signage, leading to inconsistent exposure and reduced focus detection accuracy, and existing solutions either restrict focus detection unnecessarily or fail to account for partial flicker occurrence.
Innovation Solution
The image pickup apparatus employs a CMOS sensor with focus detecting pixels arranged in rows and columns, each receiving light through different partial pupil regions, allowing sequential exposure and readout for both horizontal and vertical pupil division focus detection, with processors determining which detection method to use based on sensor drive information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rolling electronic shutter is used to read out image lines sequentially, then the image sensor can capture images in live-view mode, but lateral stripe-like flicker occurs in the imaging screen
Solution Approach 1:
The patent dynamically adjusts the accumulation time of the image sensor based on the frame frequency and lighting conditions. By making the accumulation time variable rather than fixed, the system can adapt to different shooting scenarios and reduce flicker influence while maintaining live-view capability
Solution Approach 2:
The patent changes the accumulation time parameter to be an integer multiple of the lighting cycle period. This parameter adjustment synchronizes the image sensor's exposure with the lighting frequency, thereby reducing flicker in the imaging screen while preserving productivity
2Measurement precision
If focus detection is performed using phase-difference detecting method with multiple focus detecting directions, then focus detection accuracy is improved, but the complexity of the system increases
Solution Approach 1:
The patent divides the focus detection into multiple independent directions (first focus detecting direction and second focus detecting direction perpendicular to it). Each direction uses dedicated focus detecting pixels and can be processed separately, improving accuracy while managing complexity through modular architecture
Solution Approach 2:
The image sensor is designed to perform multiple functions: it can detect focus in multiple directions, handle flicker reduction, and operate in live-view mode. The same sensor structure serves various purposes, reducing overall system complexity while maintaining high measurement precision
3Object-affected harmful factors
If the accumulation time is set to an integer multiple of the lighting cycle, then uniform exposure amount is achieved and flicker is reduced, but the flexibility in exposure control is reduced
Solution Approach 1:
The accumulation time is made dynamic and adjustable based on shooting conditions. The system can switch between different accumulation time settings (integer multiple of lighting cycle for flicker reduction, or other values for flexibility), allowing adaptive exposure control while minimizing flicker influence
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 adaptively addressing flicker in partial imaging environments, reducing line flicker and improving focus detection precision in various lighting conditions.
Implementation Method 1
an image sensor that has a plurality of focus detecting pixels arranged in rows and columns, each of which receives a light beam passing through a different partial pupil region
Data Source
AI summary
Image pickup apparatuses, control apparatuses, control methods, and storage mediums are provided herein. One or more image pickup apparatuses include an image sensor that has a plurality of focus detecting pixels arranged in rows and columns, each of which receives a light beam passing through a different partial pupil region in an imaging optical system, and which sequentially starts exposure for each row or for each block of a plurality of rows of pixels to perform sequential readout, and one or more processors that operate to perform a first focus detection using output signals from focus detecting pixels having a pupil division direction in a row direction, and a second focus detection using output signals from focus detecting pixels having a pupil division direction in a column direction, and determine whether to use a result of the second focus detection according to drive information of the image sensor.