Focus Detection Device Image Shift Correction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional focus detection devices using CMOS image pickup elements face accuracy issues due to synchronism problems in charge storing time among focus detection pixels, leading to inaccurate calculation of image shift and degraded focus detection accuracy, especially when image movement occurs during charge storage.

Innovation Solution

A focus detection device with a light receiving element, image shift detection unit, movement detection unit, and focus detection unit that corrects image shift amounts using angular velocity and image movement data, ensuring accurate focus adjustment state detection by synchronizing charge storage and readout times across focus detection pixels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If focus detection pixels are arranged in a direction other than the transverse direction of the image capturing screen, then focus detection coverage is improved, but charge storing time synchronism cannot be maintained leading to image shift

Engineering Contradiction:

Improvefocus detection coverageVSAvoidfocus detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by performing charge storage simultaneously across all focus detection pixels regardless of their arrangement direction, and by pre-calculating the expected image shift amount based on angular velocity and time difference. This allows the system to maintain charge storing time synchronism even for pixels arranged in non-transverse directions, thereby preserving focus detection accuracy while expanding detection coverage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by detecting angular velocity during the charge storage period and using this information to calculate and correct the image shift amount. The correction amount is computed based on the angular velocity, time difference between pixels, and focusing distance, then applied to compensate for the image shift. This feedback mechanism ensures that focus detection accuracy is maintained even when pixels are arranged in directions other than the transverse direction.

Inventive Principle:

Principle #23Feedback

2Ease of operation

If charge storage is performed on focus detection pixels during image movement, then focus detection function is enabled, but image shift occurs between first and second images

Engineering Contradiction:

Improvefocus detection functionVSAvoidimage shift calculation accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent uses feedback by continuously monitoring angular velocity during charge storage and using this real-time data to calculate the image shift amount. The correction amount is derived from the angular velocity, the time difference between pixel charge storage, and the focusing distance. This feedback loop allows the system to maintain focus detection functionality during image movement while accurately compensating for the resulting image shift.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies preliminary anti-action by calculating the expected image shift amount before it fully affects the focus detection results. By detecting angular velocity during charge storage and computing the correction amount in advance, the system prepares the compensation value that will counteract the image shift, thereby maintaining measurement accuracy despite ongoing image movement.

Inventive Principle:

Principle #9Preliminary anti-action

3Device complexity

If image shift correction is not applied, then device complexity is reduced, but focus detection accuracy is degraded

Engineering Contradiction:

Improvedetection system complexityVSAvoidfocus detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent employs feedback by detecting angular velocity and using this information to dynamically calculate and apply correction amounts to the image shift. This feedback-based correction mechanism improves focus detection accuracy without requiring complex hardware modifications, as the correction is achieved through computational processing of the detected angular velocity data.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces mechanical or hardware-based correction mechanisms with a computational approach. Instead of using complex optical or mechanical systems to prevent image shift, the invention uses software-based correction that calculates the shift amount from angular velocity data and applies it to the focus detection results. This substitution maintains accuracy while avoiding increased device complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8045048B2Focus detection device, focus detection method, and image pickup apparatus

Publication Date: 2011.10.25 NIKON CORP

AI summary

A focus detection device includes a light receiving element, an image shift detection unit, a movement detection unit, and a focus detection unit. The light receiving element receives a pair of light fluxes passing through different regions of a pupil of an optical system. The image shift detection unit detects an image shift amount caused by the pair of light fluxes, based on outputs of the pair of light fluxes received by the light receiving element. The movement detection unit detects an image movement amount caused by the optical system. The focus detection unit detects the focus adjustment state of the optical system by correcting the shift amount detected by the image shift detection unit, with the image movement amount detected by the movement detection unit.