Lens Barrel Cam Ring Rotation Control
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Solution Overview
Problem
Conventional lens barrels with cam-driven mechanisms experience optical performance degradation due to shifting fitting clearances between the cam ring and the fixed cylinder, leading to decentering and increased optical aberrations at zoom ends, which are difficult to manage without increasing manufacturing complexity and cost.
Innovation Solution
A lens barrel design featuring a fixed cylinder with two projections and corresponding rotation restricting portions on the cam ring, allowing for controlled rotation and alignment to maintain consistent clearance direction, reducing decentering and optical performance degradation across zoom ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single stopper pin is used to restrict cam ring rotation at zoom ends, then the structure is simple, but the fitting clearance shifts in opposite directions at different zoom ends causing increased decentering and optical performance degradation
Solution Approach 1:
The single stopper pin is segmented into two separate stopper pins positioned at different locations. The first stopper pin restricts rotation at the first zoom end while the second stopper pin restricts rotation at the second zoom end. This segmentation allows each stopper pin to independently control the fitting clearance direction at its respective zoom end, preventing the clearance from shifting in opposite directions and causing decentering.
Solution Approach 2:
Different regions of the cam ring are given different local qualities by providing distinct rotation restricting portions (first and second rotation restricting portions) at different locations. Each rotation restricting portion has a specific shape designed to work with its corresponding stopper pin, creating locally optimized clearance control for each zoom end without affecting the other.
2Ease of operation
If fitting clearance is maintained for smooth cam ring driving, then the cam ring rotates smoothly, but the clearance shifts direction at zoom ends causing decentering of the movable lens group
Solution Approach 1:
The stopper pins are preliminarily positioned and configured to define the fitting clearance direction before the cam ring reaches the zoom ends. The rotation restricting portions are designed in advance with specific shapes that guide the clearance maintenance, ensuring that when the cam ring operates, the clearance remains in a consistent direction without shifting, thus preventing decentering while maintaining smooth driving.
Solution Approach 2:
The rotation restricting portions act as intermediaries between the stopper pins and the cam ring body. These intermediary structures transmit the stopping force while simultaneously guiding the fitting clearance to maintain a consistent direction, mediating between the need for smooth driving (requiring clearance) and the need for stable clearance direction.
3Reliability
If the cam ring is restricted at one zoom end, then rotation is controlled at that end, but the maximum clearance portion shifts position causing decentering
Solution Approach 1:
The rotation control function is segmented into two independent systems: the first stopper pin with the first rotation restricting portion for controlling rotation at the first zoom end, and the second stopper pin with the second rotation restricting portion for controlling rotation at the second zoom end. This segmentation ensures that each zoom end's rotation control does not cause the maximum clearance portion to shift to positions that would create decentering.
Data Source
AI summary
A lens barrel and a projector of the invention are provided with a fixed cylinder, and a cam ring mounted on the fixed cylinder. A first projection and a second projection are provided on one of the fixed cylinder and the cam ring, and a first rotation restricting portion and a second rotation restricting portion are provided on the other of the fixed cylinder and the cam ring. The first rotation restricting portion restricts rotation of the cam ring by abutting contact with the first projection when the cam ring is rotated in a first direction, and the second rotation restricting portion restricts rotation of the cam ring by abutting contact with the second projection when the cam ring is rotated in a second direction opposite to the first direction.