Multipolar Magnet Position Detection for Lens Modules
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Solution Overview
Problem
Existing position detection units using magnetic sensors face challenges in achieving high detection accuracy due to variations in the distance between the magnetic sensor and the magnet, which affect the intensity and direction of the magnetic fields, leading to inaccuracies in determining the position of moving components like lenses in imaging apparatuses.
Innovation Solution
A position detection unit is designed with a multipolar magnet as the first magnetic field generator, which includes adjacent N and S poles along a plane orthogonal to the axis direction, and a second magnetic field generator, allowing the magnetic sensor to detect changes in the composite magnetic field with high accuracy by using a Wheatstone bridge circuit to determine the angle of the composite magnetic field, thereby reducing the impact of variations in the distance between the sensor and the magnet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a magnetic sensor and magnet are used for position detection, then the detection mechanism is simple, but detection accuracy deteriorates due to distance variations affecting magnetic field intensity and direction
Solution Approach 1:
The magnet is segmented into multiple poles (N and S poles) arranged adjacently along a plane orthogonal to the first-axis direction. This segmentation creates multiple magnetic field components that can be detected by the magnetic sensor, enabling more accurate position detection despite distance variations.
Solution Approach 2:
The magnetic sensor detects not only the intensity of the magnetic field but also the direction (angle) of the composite magnetic field. By adding angular detection in addition to intensity measurement, the system achieves higher position detection accuracy while maintaining simple device structure.
2Device complexity
If the magnetic sensor detects magnetic field intensity, then the detection principle is simple, but detection accuracy worsens due to sensitivity to distance variations
Solution Approach 1:
The system transitions from detecting only magnetic field intensity to detecting both intensity and direction (angle) of the composite magnetic field. This dimensional expansion in detection capability allows the system to compensate for distance variations and achieve higher accuracy without complicating the fundamental detection principle.
Solution Approach 2:
The patent creates a composite magnetic field detection system that combines information from multiple magnetic field components (first magnetic field from the multipolar magnet and second magnetic field from the second magnetic field generator) to form a composite magnetic field. The angle of this composite field provides robust position information insensitive to distance variations.
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
This configuration enables accurate detection of the position of the lens by effectively determining the angle of the composite magnetic field, even with variations in the distance between the sensor and the magnet, thus improving the overall detection accuracy and stability.
Implementation Method 1
a second magnetic field generator generates a second magnetic field
Data Source
AI summary
A position detection unit includes a magnetic sensor and a first magnetic field generator. The first magnetic field generator is spaced from and opposed to the magnetic sensor in a first-axis direction, includes a first multipolar magnet, and generates a first magnetic field to be exerted on the magnetic sensor. The first multipolar magnet includes N and S poles adjacent to each other along a plane orthogonal to the first-axis direction. The magnetic sensor and the first magnetic field generator are relatively movable with respect to each other along a second-axis direction orthogonal to the first-axis direction. A center position of the magnetic sensor in a third-axis direction orthogonal to both of the first-axis direction and the second-axis direction is different from a position in the third-axis direction of an interface between the N and S poles adjacent to each other in the third-axis direction.