Lens Barrel Tracking Data Correction for Hysteresis
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Solution Overview
Problem
Existing lens barrel systems face challenges in accurately correcting image plane variations due to hysteresis caused by backlash and flexure during zoom operations, leading to inconsistent in-focus states across the entire zoom range.
Innovation Solution
A lens barrel system that includes a moving lens unit, a focus lens, a driver, a controller, a zoom state detector, a focus lens detector, and a data correction mechanism to measure and correct tracking data at multiple zoom states, generating correction data to adjust the electronic cam track and maintain accurate in-focus states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detector is disposed near the zoom optical system to directly detect the position of the moving lens unit, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses the focus lens position as an intermediary to indirectly determine the moving lens unit position. Instead of directly detecting the moving lens unit position near the zoom optical system, the system detects the focus lens position (which can be detected at a convenient location) and uses this as a proxy to infer the moving lens unit position, thereby avoiding the need for complex direct detection while maintaining measurement precision.
2Device complexity
If indirect detection of the moving lens unit position is used, then device complexity is reduced, but hysteresis is generated due to tracking delay such as backlash or flexure
Solution Approach 1:
The patent implements feedback by detecting the actual focus lens position and comparing it with the expected position from tracking data. The difference (error signal) is then used to correct the tracking data, creating a closed-loop system that compensates for hysteresis and tracking delay effects, thereby maintaining position detection accuracy despite the indirect detection method.
Solution Approach 2:
The patent changes the parameter being corrected from the raw tracking data to corrected tracking data that includes compensation for hysteresis. By detecting the actual focus lens position and calculating the deviation from expected position, the system generates correction values that are applied to the tracking data, effectively changing the parameter to account for mechanical imperfections like backlash and flexure.
3Ease of manufacture
If hysteresis correction is applied uniformly across the entire zoom range, then manufacturing complexity is reduced, but the influence of hysteresis cannot be reduced effectively since hysteresis varies with zoom position
Solution Approach 1:
The patent applies local quality by generating different correction values for different zoom positions. Instead of using a uniform correction approach, the system calculates correction amounts specific to each zoom position by comparing actual focus lens positions with expected positions at multiple zoom states. This allows the correction to be tailored to the local conditions at each zoom position, effectively addressing the varying hysteresis characteristics across the zoom range.
Data Source
AI summary
A lens barrel includes a moving lens unit that moves in accordance with a zooming operation, a focus lens that moves to correct an image plane variation caused by a movement of the moving lens unit, a driver that moves the focus lens, a controller that controls the driver, a zoom state detector that detects a zoom state, a focus lens detector that detects a position of the focus lens, a storage portion that stores tracking data indicating the position of the focus lens to correct the image plane variation, and a data correction portion that measures a real position of the focus lens in an in-focus state in a plurality of zoom states for each zooming operation in directions from wide angle to telephoto sides and from the telephoto to wide angle sides to generate correction data and correct the tracking data based on the correction data.