Autofocus Control Apparatus Point Light Source Detection

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Solution Overview

Problem

Conventional imaging apparatuses using contrast type autofocus control often experience false focusing in low-brightness environments due to the detection of a point light source area, leading to inaccurate focus positioning of the main object.

Innovation Solution

A control apparatus with a determination unit to identify the presence of a point light source area and a focus control unit that adjusts the focus control method based on its position, limiting the focus driving range to prevent false focusing by switching between point light source AF and exclusion AF methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the imaging apparatus uses contrast type autofocus control to focus on the main object, then the focus accuracy is improved, but false focusing occurs when a point light source area exists in low-brightness environments

Engineering Contradiction:

Improvefocus accuracyVSAvoidfocus positioning accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The determination unit performs preliminary detection of point light source areas in the image data before the focus control unit executes autofocus. This preliminary action identifies the presence and position of point light sources, allowing the system to preemptively adjust the focus control method or driving range to prevent false focusing, thereby maintaining both focus accuracy and reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The determination unit acts as an intermediary between the image data and the focus control unit. It processes the image data to detect point light source areas and provides this information to the focus control unit, which then adjusts its operation accordingly. This intermediary function enables the system to distinguish between actual main objects and point light sources, preventing false focusing while maintaining accurate focus control

Inventive Principle:

Principle #24Intermediary (Mediator)

2Illumination intensity

If the imaging apparatus detects and adjusts exposure for point light source areas, then the brightness of point light sources is optimized, but the signal level of the main object decreases when the main object is at a different position

Engineering Contradiction:

Improvebrightness of point light sourceVSAvoidsignal level of main object

Core Design Contradiction:

Illumination intensityVSMeasurement precision

Solution Approach 1:

The determination unit identifies specific regions in the image as point light source areas and applies different processing to these localized regions versus other areas. When a point light source is detected, the system adjusts exposure or focus control specifically for that local region while preserving the signal level and quality for the main object in other regions, thereby optimizing point light source brightness without degrading main object signal

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11277554B2Control apparatus, imaging apparatus, control method, and storage medium

Publication Date: 2022.03.15 CANON KK

AI summary

A control apparatus includes a determination unit configured to determine whether or not a point light source area exists in an image, and a focus control unit configured to perform a focus control based on an evaluation value sequentially acquired from the image while moving the focus lens. The focus control unit changes a method of the focus control based on a position of the point light source area.