Camera Controller Focus Lens Drive Control for Moving Subject

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Solution Overview

Problem

Existing image classification methods for imaging apparatuses face challenges in selecting the best-focused image, especially when the subject is moving in depth, as the image magnification and spatial frequency characteristics change, making it difficult to compare focusing states based on auto-focus evaluation values.

Innovation Solution

An image processing apparatus with a first focus detection unit, drive control unit, second focus detection unit, evaluation unit, and control unit to perform focus detection, adjust the focus lens, evaluate the focusing state, and record information with the image data, allowing for accurate classification of images based on their focusing state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If continuous shooting is performed with a fixed focus position and images are classified based on AF evaluation values, then the user's manual selection workload is reduced, but the reliability of selecting the truly in-focus image deteriorates when the subject moves in depth

Engineering Contradiction:

Improvemanual selection workloadVSAvoidfocus selection accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system performs focus detection on the subject before capturing the image, predicts the in-focus position for the capture timing, and pre-adjusts the focus lens to that position. This preliminary focus adjustment ensures that when the image is captured, the focus is already optimized for the subject's predicted position, making the captured image reliably in-focus without requiring manual selection from multiple images.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If the focus position is moved during continuous shooting to track a moving subject, then the adaptability to moving subjects is improved, but the reliability of comparing AF evaluation values deteriorates due to varying image magnification and spatial frequency characteristics

Engineering Contradiction:

Improvetracking moving subject capabilityVSAvoidAF evaluation value comparison

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system changes the focus position parameter dynamically based on predicted subject position, and simultaneously performs focus detection and prediction at each capture timing. By adjusting the focus lens position to match the predicted in-focus position for each capture moment, the system maintains reliable focus evaluation despite subject movement and changing spatial frequency characteristics.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If multiple images are captured without focus adjustment, then the productivity of capturing multiple frames is improved, but the manufacturing precision of focus quality deteriorates

Engineering Contradiction:

Improvecontinuous shooting speedVSAvoidfocus quality consistency

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The system continuously performs focus detection on the subject and continuously adjusts the focus lens position according to the detected focus state and predicted in-focus position during continuous shooting. This continuous focus maintenance ensures that each captured image in the sequence has consistent high focus quality, eliminating the need to manually select the best-focused image while maintaining shooting speed.

Inventive Principle:

Principle #20Continuity of useful action

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 solution reduces the load of selecting the best-focused image by accurately evaluating and recording the focusing state of each image, ensuring that images are classified based on their intended focus, even when the subject is moving in depth.

Implementation Method 1

a first focus detection unit that performs first focus detection on a subject

Methodology Applied

Scientific EffectPhase difference detection:

Implementation Method 2

a second focus detection unit that performs second focus detection of phase difference type based on image data acquired by a first image sensor

Methodology Applied

Scientific EffectPhase difference detection:

Implementation Method 3

a drive control unit that controls driving of a focus lens based on a result of the first focus detection

Methodology Applied

Scientific EffectLens driving:

Data Source

PatentUS10904425B2Image processing apparatus, control method therefor, and storage medium for evaluating a focusing state of image data

Publication Date: 2021.01.26 CANON KK

AI summary

A camera controller controls driving of a focus lens included in a lens group based on a result of first focus detection performed by a defocus amount detection unit. The defocus amount detection unit performs second focus detection based on image data acquired by a first image sensor which outputs image data corresponding to a subject image at a position of the focus lens that is based on the control. The camera controller evaluates, based on a result of the second focus detection, a focusing state of the image data that is based on an output of the first image sensor, and performs control to record information about the evaluated focusing state together with data corresponding to the image data.