Lens Barrel Position Detection via Magnetic Scale
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Solution Overview
Problem
Existing lens barrel systems face accuracy issues in detecting the position of the lens movement frame due to gaps between guide grooves and linking pins, and complex electrical wiring arrangements complicate assembly.
Innovation Solution
A lens barrel design where the detected member is provided on the lens movement frame and the detector is positioned on the outside of the barrel main body, allowing direct detection of the lens movement frame's position with improved accuracy and simplified wiring installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a gap is formed between the guide groove of the cam barrel and the linking pin of the lens movement frame, then the lens movement frame can move smoothly, but the position detection accuracy decreases due to offset between the detected position and actual position
Solution Approach 1:
A detected member (magnetic scale) is introduced as an intermediary element that is directly coupled to the lens movement frame. This member provides a direct reference for position detection without relying on the gap between the cam barrel guide groove and linking pin, thereby eliminating the offset error while preserving smooth movement.
Solution Approach 2:
The mechanical position detection method (using the cam barrel rotation position as reference) is replaced with a magnetic field-based detection system. A magnetic sensor detects the position of the magnetic scale directly attached to the lens movement frame, substituting the indirect mechanical reference with a direct magnetic field reference that is not affected by mechanical gaps.
2Measurement precision
If a photointerruptor is disposed inside the cam barrel, then position detection can be achieved, but the electrical wiring for power supply and signal transmission becomes complicated and assembly becomes more difficult
Solution Approach 1:
The magnetic sensor is extracted from the interior of the cam barrel and positioned on the exterior surface. This extraction eliminates the need for complex internal wiring through the cam barrel, as the sensor can be connected to external circuitry without penetrating the cam barrel structure. The magnetic field detection works through the cam barrel material, maintaining detection capability while simplifying wiring.
Solution Approach 2:
The detection method is changed from optical (photointerruptor requiring light transmission paths and complex wiring) to magnetic field-based (magnetic sensor detecting magnetic scale position). This parameter change in the detection principle allows for simpler wiring configuration and easier assembly, as magnetic sensors can be positioned externally and connected without interfering with the cam barrel's internal structure.
Data Source
AI summary
A lens barrel includes a barrel main body, a first lens movement frame, a magnetic scale, and a magnetic sensor. The first lens movement frame is arranged movably in the optical axis direction of the optical system with respect to the barrel main body. The magnetic scale is provided to the first lens movement frame. The magnetic sensor is arranged on the outside of the barrel main body, and detects the position of the first lens movement frame with respect to the barrel main body by detecting the position of the magnetic scale with respect to the barrel main body.