Lens Holder Drive Device Quadrangular Yoke Magnetic Interference
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Solution Overview
Problem
Existing lens holder driving devices face challenges in accurately detecting the position of the lens holder in the light axis direction due to interference from driving magnets and manufacturing complexities, particularly with arc-shaped inner peripheries of driving magnets, which affect the stability and balance of the position detection mechanism.
Innovation Solution
A lens holder driving device with a quadrangular cylindrical yoke and plate-shaped driving magnets, separated from sensor magnets, allows for accurate position detection in the light axis direction by optimizing magnetic interference and using a position detection mechanism with sensor magnets and a hole sensor, ensuring correct positioning and balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position detection mechanism using sensor magnets and driving magnets is provided in the lens holder driving device, then the position of the lens holder can be detected, but the driving magnets interfere with the sensor magnets causing inaccurate position detection
Solution Approach 1:
The patent extracts the sensor magnets from the lens holder and relocates them to the yoke, separating the detection function from the moving component. This extraction eliminates the magnetic interference problem that occurred when sensor magnets were placed on the lens holder near the driving magnets, thereby improving position detection accuracy without suffering from harmful magnetic effects.
Solution Approach 2:
The patent introduces the yoke as an intermediary component that hosts the sensor magnets. The yoke serves as a mediator between the driving mechanism and the position detection system, providing a stable mounting location for sensor magnets that is not subject to the same magnetic interference issues as the lens holder, thus enabling accurate position detection.
2Reliability
If arc-shaped inner periphery driving magnets are used, then the magnetic circuit can be optimized, but the manufacturing complexity and difficulty increase
Solution Approach 1:
Instead of shaping the driving magnets with complex arc-shaped inner peripheries, the patent inverts the approach by providing the yoke with an arc-shaped inner periphery that matches the lens holder's outer periphery. This inversion simplifies the driving magnet manufacturing while achieving the same magnetic circuit optimization through the yoke's geometry.
Solution Approach 2:
The patent segments the magnetic circuit optimization function between the yoke's arc-shaped inner periphery and the driving magnets. By assigning the complex geometric shape to the yoke rather than the driving magnets, the manufacturing complexity is separated from the critical magnetic performance components, making the overall system easier to manufacture while maintaining reliability.
3Device complexity
If sensor magnets are attached on the lens holder, then the position detection mechanism can be simplified, but the magnetic interference from driving magnets affects the sensor magnets
Solution Approach 1:
The patent extracts the sensor magnets from the lens holder and relocates them to the yoke, separating the detection function from the moving component. This extraction eliminates the magnetic interference problem that occurred when sensor magnets were placed on the lens holder near the driving magnets, thereby improving position detection accuracy without suffering from harmful magnetic effects.
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
The solution enables precise detection of the lens holder's position in the light axis direction without interference from the driving magnets, ensuring stable and balanced movement, improving the accuracy and reliability of the position detection mechanism.
Implementation Method 1
VCM systems using a voice coil motor (VCM) are known as a driving mechanism (actuator) used for the above-mentioned AF lens holder driving device. An AF lens holder driving device of the VCM type includes a magnetic circuit composed of a driving coil, a yoke and a permanent magnet as a driving mechanism (actuator).
Implementation Method 2
PTL 1 discloses a lens driving device that performs hand shake correction by utilizing a position detection mechanism using a Hall device sensor magnet and a Hall device sensor.
Data Source
AI summary
A lens holder drive device has: a lens holder; a fixing part that includes a base member disposed below the lens holder; a drive mechanism; an upper-side plate spring; a lower-side plate spring; and a position detection unit that detects the position of the lens holder in the optical axis direction. The drive mechanism has: a drive coil fixed to the perimeter of the lens holder; a yoke having a substantially square columnar shape; and a drive magnet disposed to face the drive coil in a first direction which is orthogonal to the optical axis direction. The position detection unit includes: a sensor magnet attached to an outer circumferential surface of the lens holder in a second direction which is orthogonal to the optical axis direction and the first direction; and a magnetic sensing element that faces the sensor magnet and is provided to the base member.