Imaging Apparatus Focus Controller for Continuous AF Speed
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Solution Overview
Problem
Conventional imaging apparatuses face challenges in improving Auto Focus (AF) speed and accuracy, especially during burst capture and continuous shooting, as they rely on contrast AF methods that can lead to delayed focus adjustment and display of blurred images due to the need for repeated image signal readouts from the image sensor.
Innovation Solution
The implementation of a focus controller that generates an evaluation value by extracting signal components from image signals to adjust the focus lens position where the evaluation value peaks, combined with a tracking circuit for continuous focus adjustment and display of initial image data corresponding to the peak evaluation value, allowing for optimized image display and tracking during continuous focus operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If contrast AF is executed by reading out image signals from the image sensor repeatedly, then focus adjustment can be performed, but AF speed becomes slow due to the time required for repeated readout operations
Solution Approach 1:
The patent applies preliminary action by performing focus adjustment calculations using previously readout image signals before new image signals are fully available. The focus adjustment unit calculates focus adjustment amounts based on historical image data, allowing the system to prepare focus adjustments in advance and reduce waiting time for new readout operations to complete.
Solution Approach 2:
The patent implements dynamics by continuously updating focus adjustment based on moving images rather than static images. The system dynamically adjusts focus during video playback or live view by comparing successive frames and calculating focus drift, enabling real-time focus correction without requiring repeated full readout cycles from the image sensor.
2Reliability
If continuous AF is executed during burst capture, then focus can be maintained on moving subjects, but display performance deteriorates due to processing delays and blurred image display
Solution Approach 1:
The patent applies copying by using a buffer to store and manage multiple frames of image data during burst capture. The display unit selectively displays frames from the buffer based on focus evaluation results, allowing the system to maintain focus reliability while improving display performance by choosing the sharpest available frame for display rather than displaying intermediate blurred states.
Solution Approach 2:
The patent implements feedback through continuous focus evaluation during burst capture and playback. The focus evaluation unit assesses sharpness of captured frames, and this evaluation feedback drives the focus adjustment unit to correct focus drift, creating a closed-loop system that maintains focus reliability while providing visual feedback to the user about focus quality.
3Measurement precision
If focus adjustment is performed based on peak evaluation value, then accurate focus can be achieved, but processing time increases due to continuous evaluation and calculation
Solution Approach 1:
The patent applies partial action by performing focus evaluation selectively rather than continuously on all image data. The focus evaluation unit evaluates focus based on representative frames or key moments during capture and playback, reducing processing time while maintaining sufficient focus accuracy through targeted evaluation rather than exhaustive continuous analysis.
Data Source
AI summary
An imaging apparatus, comprising a focus controller that generates an evaluation value by extracting given signal components from an image signal, and carries out focus adjustment by calculating position of the focus lens where the evaluation value becomes a peak, a display that displays an image based on image data generated from the image signal, and a controller that, as initial image display after commencement of the continuous focus adjustment operation, executes display using the display based on image data corresponding to an image signal in which the evaluation value becomes a peak, from among image data that has been acquired during the focus adjustment operation.