Focus Detection Apparatus Noise Assessment Filter Selection
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Solution Overview
Problem
Conventional phase difference detection methods for focus detection in image pickup apparatuses face challenges in accurately determining the effect of noise in parallax image signals, which can lead to errors in focus detection and reduced accuracy due to noise contamination.
Innovation Solution
An image pickup apparatus is designed with a determination unit to assess the noise effect in parallax image signals and an acquisition unit that selects appropriate filters based on this assessment to reduce noise impact, using band-pass filters with different frequency characteristics to enhance focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase difference detection method is used without noise assessment, then focus detection can be performed, but noise effect reduces measurement precision
Solution Approach 1:
The determination unit performs preliminary assessment of noise effect in parallax image signals before the correlation calculation is executed. This preliminary action allows the system to select appropriate filters and adjust detection parameters in advance, thereby improving measurement precision without significantly increasing overall system complexity.
Solution Approach 2:
The determination unit acts as an intermediary between the image signal input and the correlation calculation process. It assesses noise effects and determines appropriate processing strategies, serving as a mediator that optimizes the detection process and improves accuracy without requiring complete system redesign.
2Measurement precision
If multiple filters with different frequency characteristics are used, then noise effect can be reduced, but device complexity increases
Solution Approach 1:
The system dynamically selects appropriate filters based on the assessed noise characteristics of the input signals. Rather than using a fixed filter configuration, the determination unit adapts the filter selection to match the actual noise conditions, improving measurement precision while keeping the system flexible and manageable.
Solution Approach 2:
The system changes filter parameters (frequency characteristics) based on the determined noise effect level. By adjusting which filter is applied according to the assessed noise conditions, the system optimizes phase difference calculation accuracy without requiring all filters to operate simultaneously, thus managing device complexity.
3Measurement precision
If noise correction processing is added to the focus detection process, then measurement precision improves, but processing time increases
Solution Approach 1:
The determination unit performs noise effect assessment preliminarily, before the main correlation calculation. This allows the system to pre-determine the appropriate processing level and filter selection, so that noise correction can be applied efficiently without adding excessive processing time to the overall workflow.
Solution Approach 2:
The system applies noise correction processing selectively based on the determined noise effect level. When noise effect is low, minimal or no correction is applied; when noise effect is high, appropriate filters and correction methods are applied. This partial action approach improves accuracy when needed while minimizing unnecessary processing time.
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
The solution effectively reduces the effect of noise in focus detection, improving the accuracy of phase difference calculation and subsequent focus adjustment by selecting the appropriate filter based on the noise level, thereby enhancing the overall focus detection process.
Implementation Method 1
a photodiode A for photoelectrically converting one image obtained by pupil division, a photodiode B for photoelectrically converting the other image
Data Source
AI summary
A focus detection apparatus includes a determination unit configured to determine a degree of effect of noise included in a pair of parallax image signals, and an acquisition unit configured to acquire information about a phase difference between the pair of parallax images based on a calculation of correlation between the pair of parallax image signals. The acquisition unit selects a filter used to acquire the information about the phase difference from among a plurality of filters having different frequency characteristics based on a determination result of the determination unit, and outputs, as a focus detection result, the information about the phase difference acquired by the correlation calculation based on the pair of parallax image signals applied to the selected filter.