Image Sensor Focus Detection During Buffer Overflow
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Solution Overview
Problem
Image capturing apparatuses face a decrease in focus detection accuracy during continuous shooting when the buffer memory becomes full, causing a temporary cessation of fixed shooting intervals and potential inaccuracies in imaging plane phase difference detection methods.
Innovation Solution
An image capturing apparatus with an image sensor, focus detection unit, continuous shooting unit, storage unit, and estimation unit that performs focus detection and estimation of the in-focus position using focus detection signals even when the storage unit cannot store image signals, allowing for continuous focus adjustment during buffer overflow conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous shooting is performed at high speed using buffer memory, then shooting speed and productivity are improved, but focus detection accuracy deteriorates when buffer memory becomes full
Solution Approach 1:
The system performs focus detection in advance during periods when the buffer memory has available capacity, before the buffer becomes full. The estimation unit calculates the in-focus position using focus detection results obtained at earlier timestamps, allowing focus adjustment to be prepared beforehand. This preliminary focus detection ensures that focus accuracy is maintained even when continuous shooting continues at high speed without interruption.
Solution Approach 2:
The system uses its own buffer memory capacity management to serve dual purposes: both storing image data for continuous shooting and storing focus detection signals for accuracy maintenance. When buffer space is available, the system automatically performs focus detection and stores the results, utilizing the buffer's idle capacity for focus-related operations. This self-service approach allows the system to maintain focus accuracy without requiring external or additional resources.
2Ease of operation
If fixed shooting intervals are maintained during continuous shooting, then ease of operation is improved, but reliability deteriorates when buffer memory becomes full
Solution Approach 1:
The system continuously monitors buffer memory capacity and uses this feedback to dynamically adjust focus detection timing. The storage unit stores focus detection results with their corresponding timestamps, and the estimation unit selects appropriate historical data based on current buffer status and shooting interval requirements. This feedback mechanism ensures that focus detection is performed at optimal moments while maintaining the appearance of fixed shooting intervals for the user, thereby preserving both ease of operation and reliability.
3Device complexity
If focus detection is performed using imaging plane phase difference detection method, then device complexity is reduced, but focus detection accuracy deteriorates when shooting intervals become non-fixed
Solution Approach 1:
The imaging plane phase difference detection method performs focus detection in advance during periods when buffer memory has available capacity. The system captures focus detection signals at earlier timestamps and stores them in the buffer memory along with timing information. When continuous shooting proceeds and the buffer fills up, the estimation unit retrieves these pre-captured focus detection results and uses them to calculate the in-focus position, ensuring accuracy is maintained despite the simplicity of the detection method.
Solution Approach 2:
The buffer memory serves as an intermediary between the simple imaging plane phase difference detection method and the final focus adjustment. It stores focus detection signals and their timestamps, allowing the estimation unit to bridge the time gap between when focus detection is performed and when it is applied. This intermediary role of the buffer memory enables the simple detection method to achieve accurate focus results even when shooting intervals become non-fixed due to buffer capacity constraints.
Data Source
AI summary
An image capturing apparatus, comprises an image sensor; a focus detection unit; a continuous shooting unit; an estimation unit that estimates an in-focus position of an object based on a result of the focus detection and information relating to an accumulation timing; and a focus adjustment unit that performs focus adjustment, wherein, the image sensor performs accumulation of the focus detection signal in a time period in which a storage unit cannot store the image signal for recording, the focus detection unit performs the focus detection, and the estimation unit estimates the in-focus position at the time of acquiring the image signal that is acquired after the end of the time period, based on the focus detection result and the information relating to the accumulation timing of the focus detection signal.