Camera Auto Focus Correction for Flash Spectrum Mismatch

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Cameras often fail to auto focus properly during flash illumination due to the short duration of flash discharge, and existing methods may not account for differences between the ambient light spectrum used for auto focus and the flash spectrum used for image capture, leading to focus issues in captured images.

Innovation Solution

A camera system that uses ambient light for auto focusing and applies a correction factor to adjust the focus for the different wavelengths used during image capture, allowing for proper focus under both ambient and flash light spectra, even when they differ.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If flash illumination is used for image capture, then image capture speed is improved, but auto focus accuracy deteriorates due to short flash duration

Engineering Contradiction:

Improveimage capture speedVSAvoidauto focus accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent performs auto focus using ambient light before the flash discharge occurs. The camera completes the focusing operation during the pre-flash or ambient light period, ensuring focus is established before the actual image capture with flash illumination. This preliminary action resolves the contradiction by separating the focusing measurement from the brief flash duration.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If ambient light spectrum is used for auto focus, then auto focus capability is improved, but image capture focus accuracy deteriorates when flash spectrum differs from ambient light spectrum

Engineering Contradiction:

Improveauto focus capabilityVSAvoidimage capture focus accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent applies a spectral correction factor to adjust the auto focus position based on the difference between ambient light spectrum and flash spectrum. The system calculates how the focal point shifts between different wavelengths and compensates for this shift by modifying the lens position or focus parameters, ensuring accurate focus for the flash spectrum even when auto focus was performed using ambient light.

Inventive Principle:

Principle #35Parameter changes

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

Enables accurate auto focusing using ambient light and ensures proper focus during image capture under flash illumination by calculating and applying a correction factor for wavelength differences, ensuring clear images even when ambient and flash spectra differ.

Implementation Method 1

If, however, the ambient light spectrum used for auto focus differs from the flash light spectrum that is used for image capture, the camera focus that is obtained during auto focus may not be entirely in focus for the captured image

Methodology Applied

Scientific EffectChromatic aberration: Refraction

Data Source

PatentUS8049812B2Camera with auto focus capability

Publication Date: 2011.11.01 GENTEX CORP

AI summary

A method and apparatus for automatically focusing a camera that may rely upon ambient light for auto focusing and flash illumination for image capture. A correction factor may be determined that is based at least in part on a range between the camera and a desired subject. The camera focus may be adjusted in accordance with the correction factor prior to capturing a capture image using flash illumination.