Focus Indication Stability in Zooming Image Pickup Apparatus
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Solution Overview
Problem
Image pickup apparatuses face challenges in maintaining accurate focus indications during zoom operations when using manual focus, as existing systems rely on threshold values that change with F-number variations, leading to incorrect out-of-focus indications.
Innovation Solution
An image pickup apparatus with an image pickup unit, a determination unit that sets an in-focus condition based on a minimum F-number threshold, and a focus indication unit that provides stable in-focus indications regardless of zoom operations, utilizing an image plane phase difference detection method to assess defocus amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the focus indication uses defocus amount information with threshold values based on open F numbers, then the focus indication adapts to different zoom conditions, but the focus indication becomes unstable and shows false out-of-focus states when zoom operations change the F number
Solution Approach 1:
The patent changes the parameter used for focus indication from defocus amount (which varies with F number) to defocus amount multiplied by F number. This parameter transformation ensures that the focus indication remains stable across different zoom conditions, as the F number multiplication compensates for the F number changes during zoom operations, preventing false out-of-focus indications
Solution Approach 2:
The patent introduces an intermediary calculation step where the focus indication is derived from the product of defocus amount and F number rather than defocus amount alone. This intermediary parameter acts as a mediator that decouples the focus indication from direct F number variations, maintaining indication stability while still reflecting actual focus conditions
2Measurement precision
If the threshold value for in-focus indication is set based on current open F number, then the indication is sensitive to actual focus quality, but the threshold changes during zoom operations causing incorrect focus status changes
Solution Approach 1:
The patent transforms the threshold determination from being based solely on current F number to being based on the product of defocus amount and F number. This parameter change creates a more robust threshold that accounts for both focus quality and F number variations, maintaining measurement precision while achieving stability during zoom operations
Solution Approach 2:
The patent performs preliminary calculation of the focus indication parameter (defocus amount × F number) before zoom operations occur, establishing a baseline that remains valid across zoom conditions. This preliminary action allows the system to maintain consistent focus assessment criteria throughout the zoom range without requiring real-time threshold adjustments
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
Ensures consistent and accurate focus indications during manual focus adjustments and zoom operations, preventing false out-of-focus notifications and maintaining image clarity.
Implementation Method 1
an image pickup unit configured to pick up an optical image formed through an optical system
Implementation Method 2
utilizing an image plane phase difference detection method to assess defocus amounts
Data Source
AI summary
In a case where an in-focus threshold value is set based on an F number, when a zoom or a focus is changed, the threshold value will change, so that an in-focus indication happens to be switched to an out-of-focus indication.To solve the problem, an image pickup apparatus has an image pickup unit that picks up an optical image formed through an optical system, wherein the optical system has a zoom function and F number thereof varies within a predetermined range according to a plurality of zoom conditions, a determination unit that determines an in-focus condition when a defocus amount of an object is smaller than predetermined first threshold value, wherein the first threshold value is determined by a minimum F number within the predetermined range, and a focus indication unit that indicates a first in-focus indication when the focus condition is in-focus condition.