Lens Control Apparatus for Zoom Focus Stability
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Solution Overview
Problem
Existing techniques for maintaining focus stability during zooming operations are unstable, particularly at low illuminance or when the object is not at the image center, and can result in defocusing issues due to insufficient depth of field, especially at long focal lengths.
Innovation Solution
A lens control apparatus that includes a control unit for both zoom and focus lenses, utilizing stored cam data to adjust the focus lens position based on the object distance and zoom magnification, ensuring the focal position moves appropriately with the zoom lens to maintain focus, even when the depth of field is shallow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If AF during zooming is performed using high-frequency contrast evaluation, then focusing can be performed while focal position is moving, but the in-focus position becomes unstable at low illuminance or when the object is not at the image center
Solution Approach 1:
The system performs preliminary actions by acquiring object distance information before zooming operation and selecting appropriate cam tracks in advance. The control unit prepares the focal position movement plan based on the selected cam track that corresponds to the acquired object distance, ensuring stable focusing during zooming operation.
2Reliability
If control is performed to focus on a specific object distance within predetermined focal length, then focus stability is improved when sufficient depth of field is secured, but defocusing occurs when depth of field is insufficient due to long focal length
Solution Approach 1:
The system dynamically selects cam tracks based on the acquired object distance and zoom magnification. The control unit determines the appropriate cam track from multiple stored tracks and adjusts the focal position movement accordingly, allowing the system to adapt to different focal lengths and object distances while maintaining focus stability.
3Device complexity
If the focal position is moved based on a single cam track, then the control is simple, but the focal position cannot be accurately adjusted when zoom magnification changes significantly
Solution Approach 1:
The system segments the cam track selection into multiple discrete tracks stored in the storage unit, each corresponding to different object distances. The control unit selects the appropriate segment (cam track) based on the acquired object distance and zoom magnification, enabling accurate focal position adjustment while maintaining relatively simple control logic.
Data Source
AI summary
A lens control apparatus includes a control unit that controls a position of a zoom lens and a position of a focus lens, a storage unit that stores cam tracks, an object distance acquisition unit that acquires an object distance, and a target position acquisition unit that acquires information of a first track corresponding to the object distance acquired by the object distance acquisition unit before movement of the zoom lens and a second track corresponding to an object distance longer than that of the first track, and the target position of the focus lens so as to move a focal position of an imaging optical system including the zoom lens and the focus lens based on the first track and the second track when zoom magnification of the imaging optical system including the zoom lens and the focus lens is increased by the movement of the zoom lens.