Lens Barrel Rotation Sensing with GMR Sensor
Solution Overview
Problem
Conventional displacement sensing devices for lens barrels require a dedicated member to unitize the magnetic scale and MR sensor, complicating the structure and limiting rotation sensing resolution.
Innovation Solution
A lens barrel design incorporating a movable lens frame, manual operation ring, first and second gear units, detection magnet, and rotation sensor, where the detection magnet rotates with the second gear unit and is sensed by a GMR sensor attached to a separate member, improving rotation sensing resolution without adding complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated member is used to unitize the magnetic scale and MR sensor, then sensing resolution can be improved, but device complexity increases
Solution Approach 1:
The patent combines the magnetic scale and MR sensor into a single integrated member, eliminating the need for a dedicated casing member. This merging approach maintains the high sensing resolution benefits while reducing structural complexity and the number of components required.
Solution Approach 2:
The integrated member serves multiple functions: it acts as both the magnetic scale and the sensor housing/support structure. This multi-functionality eliminates the need for separate dedicated members, thereby reducing device complexity while maintaining sensing resolution.
2Device complexity
If photo-interrupter based sensing is used, then structure remains simple, but sensing resolution is limited
Solution Approach 1:
The patent replaces the photo-interrupter based optical sensing system with a magnetic sensing system using MR sensors and magnetic scales. This substitution enables higher sensing resolution while maintaining relatively simple structural implementation through the integrated member design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances rotation sensing resolution without complicating the structure, allowing for finer depth of field adjustments in lens barrels, such as macro lenses, by using a separate GMR sensor to detect the rotation of the detection magnet.
Implementation Method 1
the detection magnet rotates integrally with the second gear portion and has a magnetized surface on which different magnetic poles are magnetized alternately. The rotation sensor is fixed to a member separate from the detection magnet, is provided at a position adjacent to the detection magnet, and senses the rotation of the detection magnet
Data Source
AI summary
A lens barrel 100 includes a fifth lens group unit 25, a focus ring 31, an internal gear 31b, a pinion gear 41, a detection magnet 43, and a GMR sensor 44. The internal gear 31b rotates integrally with the focus ring 31 and has a plurality of gear portions 31c. The pinion gear 41 is provided on the inner peripheral surface side of the focus ring 31 and has a gear portion 41a that mates with the gear portion 31c of the internal gear 31b, and a guide shaft 42 that is inserted through the center of the gear portion 41a. The guide shaft 42 is inserted through the detection magnet 43, and the detection magnet 43 rotates integrally with the gear portion 41a and has a magnetized surface 43b on which different magnetic poles are alternately magnetized. The GMR sensor 44 is fixed to a member separate from the detection magnet 43, is provided at a position adjacent to the detection magnet 43, and detects the rotation of the detection magnet 43 that rotates along with the pinion gear 41.