Focus Adjustment Device Backlash Mitigation via Direction Judgment
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Solution Overview
Problem
Existing automatic focus adjustment techniques for imaging devices face challenges due to backlash in the drive mechanism of the focus lens, which can prevent desired lens drive and deteriorate autofocus performance.
Innovation Solution
A focus adjustment device and method that repeatedly judges the drive direction of the focus lens based on evaluation values from image signals, and when the lens is driven in a first direction, it is forbidden from driving in that direction if a subsequent evaluation value indicates a different direction, thereby mitigating the influence of backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the focus lens is driven in a first direction based on a first evaluation value and then driven in a second direction based on a subsequently calculated second evaluation value, then the focus adjustment can respond to changing focus conditions, but the backlash in the drive mechanism causes the lens to fail to reach the desired position and deteriorates autofocus performance
Solution Approach 1:
The control unit applies preliminary anti-action by detecting when the focus lens has been driven in a first direction and subsequently in a second direction, then actively preventing further driving in the first direction even when evaluation values suggest it. This counteracts the backlash effect that would otherwise cause the lens to fail to reach desired positions, thereby maintaining reliable autofocus performance while allowing responsive focus adjustment.
Solution Approach 2:
The system uses feedback from repeatedly calculating evaluation values and judging drive directions to control focus lens movement. The control unit monitors the sequence of drive directions and uses this feedback information to determine when to forbid driving in a particular direction, enabling the system to respond to changing focus conditions while compensating for mechanical backlash through intelligent control decisions.
2Reliability
If the drive amount after switching is increased or the number of times of driving is increased in accordance with a play amount of a drive transmission mechanism, then the backlash influence can be compensated, but the focus adjustment time is extended and productivity is reduced
Solution Approach 1:
The system dynamically adjusts the focus lens drive strategy based on real-time evaluation of drive direction sequences. Rather than using fixed compensation amounts or predetermined numbers of drive cycles, the control unit adaptively determines when to forbid driving in a particular direction based on the actual sequence of evaluation results, optimizing both accuracy and speed for each specific situation.
Solution Approach 2:
The control unit changes the operational parameters of the focus adjustment by dynamically modifying the drive direction decisions based on evaluated conditions. Instead of consistently increasing drive amount or number of cycles, the system changes the drive parameters adaptively by forbidding drives in specific directions only when necessary, thereby maintaining accuracy without unnecessarily extending adjustment time.
3Reliability
If the focus lens is repeatedly driven in both directions to compensate for backlash, then the desired focus position can be reached, but unnecessary lens movements occur and energy is wasted
Solution Approach 1:
By detecting the sequence of drive directions and actively preventing unnecessary reverse driving, the system eliminates wasted energy consumption while still achieving accurate focus positioning. The preliminary anti-action forbids driving in directions that would only cause unnecessary movements due to backlash, thereby reducing energy loss without compromising focus position accuracy.
Data Source
AI summary
A focus adjustment device includes a direction judgment unit and a control unit. A direction judgment unit calculates an evaluation value based on an image signal of a focus detection region, thereby judging a drive direction of a focus lens. The control unit controls a focus adjustment operation on the basis of the drive direction. The control unit causes the direction judgment unit to repeatedly judge the drive direction, and when the focus lens is slightly driven in a first direction judged on the basis of a first evaluation value and then the focus lens is slightly driven in a second direction judged on the basis of a subsequently calculated second evaluation value, the control unit forbids the slight driving of the focus lens in the first direction even though a drive direction judged on the basis of a further subsequently calculated third evaluation value is the first direction.