Imaging Focus Position Control for Stable 3DNR Autofocus
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Solution Overview
Problem
Existing autofocus (AF) control in imaging apparatuses using 3-dimensional noise reduction (3DNR) processing suffers from inaccuracies in detecting the in-focus position due to smoothing of evaluation values, leading to issues like direction inversions, delayed convergence, and reduced accuracy in determining contrast changes.
Innovation Solution
The imaging apparatus controls the movement of the focus position by stopping for a predetermined time period corresponding to the intensity of 3DNR processing, and adjusts the wobbling driving amount to enhance accuracy, particularly at critical control points such as target position changes or direction inversions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 3DNR processing is applied to reduce noise in images, then image quality is improved, but the evaluation value becomes smoothed and focus position detection accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by stopping the focus position movement in advance during high-intensity 3DNR processing. The control unit determines when to stop movement based on the intensity level of 3DNR processing, preventing the smoothed evaluation value from causing inaccurate focus detection. This preliminary pause allows the evaluation value to stabilize before resuming focus adjustment, resolving the contradiction between noise reduction and detection accuracy.
2Reliability
If evaluation value is smoothed over multiple frames for noise reduction, then noise is reduced, but direction inversions and delayed convergence occur in autofocus control
Solution Approach 1:
The patent implements periodic action by intermittently stopping and resuming focus position movement based on the intensity of 3DNR processing. During high-intensity processing, movement is stopped periodically to allow evaluation value stabilization. When processing intensity decreases, movement resumes. This periodic pause-resume mechanism prevents direction inversions while maintaining reasonable autofocus convergence speed, balancing noise reduction with productivity.
3Speed
If focus position movement continues during high-intensity 3DNR processing, then autofocus responsiveness is maintained, but evaluation value becomes unstable and detection accuracy decreases
Solution Approach 1:
The patent applies dynamics by making the focus position movement adaptive to the intensity of 3DNR processing. The control unit dynamically adjusts movement behavior based on real-time processing intensity: stopping movement during high-intensity processing when stability is needed, and resuming movement when processing intensity decreases to maintain responsiveness. This dynamic adjustment resolves the contradiction between responsiveness and evaluation value stability.
Data Source
AI summary
An image capturing apparatus includes an image sensor that captures an image of an object formed by an imaging optical system, at least one processor, and a memory coupled to the at least one processor. The memory stores instructions that, when executed by the at least one processor, cause the at least one processor to execute noise reduction processing on a first image captured by the image sensor based on a plurality of second images, acquire an evaluation value indicating contrast of the first image on which the noise reduction processing has been executed, and control movement of a focus position of the imaging optical system based on the evaluation value. The movement is controlled so that the movement is stopped for a time period having a length corresponding to an intensity of the noise reduction processing in a case where a predetermined condition is satisfied.