Voice Coil Motor Sensor Layout for Precise Lens Motion Control
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Solution Overview
Problem
Uncontrollable magnetic interference between multiple magnetic pieces in voice coil motors leads to errors in controlling the movement of lens assemblies in camera modules, resulting in reduced precision and speed in focusing and anti-shake functions.
Innovation Solution
The voice coil motor design includes a first magnetic sensor disposed on a counterweight, away from heat sources, which detects magnetic field changes generated by a first induction magnet to accurately control the movement of the lens assembly along the optical axis, thereby improving precision and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple magnetic pieces are arranged radially around the optical carrier to enable multi-directional lens movement control, then the lens assembly can be driven to move in x-axis, y-axis, and z-axis directions, but uncontrollable magnetic interference occurs between the magnetic pieces leading to control errors
Solution Approach 1:
The magnetic field sensing function is segmented into multiple independent magnetic sensors positioned at different locations. Each sensor detects magnetic field changes in its specific region, allowing the system to distinguish between intentional magnetic field changes (from coil electrification) and interference (from magnetic piece interactions). This segmentation enables selective use of sensor data to maintain control precision while preserving multi-directional movement capability.
Solution Approach 2:
Magnetic sensors are introduced as intermediary detection elements between the magnetic pieces and the control system. These sensors convert magnetic field changes into electrical signals that can be processed to distinguish useful control signals from interference. The intermediary sensors enable the system to detect and compensate for magnetic interference, maintaining control precision without sacrificing the versatility of multi-directional movement.
2Device complexity
If the magnetic sensor is disposed on the FPC substrate close to the heat source, then the structure is compact, but the heat generated by FPC substrate operation affects the detection precision of the magnetic sensor
Solution Approach 1:
The magnetic sensor is extracted from the heat-prone FPC substrate area and relocated to a position on the optical carrier away from heat-generating components. This spatial separation removes the sensor from the thermal environment that would degrade its detection precision, while the sensor remains integrated into the overall device structure through its mounting on the optical carrier.
Solution Approach 2:
The sensor placement problem is solved by transitioning from a two-dimensional planar arrangement (on the FPC substrate) to a three-dimensional configuration (on the optical carrier at a different spatial location). This dimensional change allows the sensor to be positioned in a thermally favorable location while maintaining structural integration, resolving the conflict between compactness and detection precision.
3Measurement precision
If closed-loop control is implemented using magnetic sensor feedback to improve control precision, then lens assembly positioning accuracy improves, but the system requires additional components and control complexity
Solution Approach 1:
A closed-loop control system is implemented where magnetic sensors continuously detect magnetic field changes caused by lens assembly position changes, convert them to electrical signals, and feed this information back to the control circuit. The control circuit compares the detected position with the target position and adjusts coil electrification accordingly, achieving high positioning accuracy through continuous feedback while managing complexity through efficient signal processing.
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 more precise and faster closed-loop control of the lens assembly, enhancing the focusing and anti-shake performance of the camera module by minimizing the impact of magnetic interference and heat-generated errors.
Implementation Method 1
After being electrified, the first coils may drive, under actions of magnetic fields, the optical carrier to move in a direction of an optical axis
Implementation Method 2
One of the two coils is disposed opposite to the first magnetic piece, and the other of the two coils is disposed opposite to the third magnetic piece
Implementation Method 3
the first magnetic sensor may convert a magnetic field signal generated by the first induction magnet into a first electrical signal, to detect a moving direction and a moving distance
Implementation Method 4
The first magnetic sensor is disposed on a side that is of the counterweight and that is close to the optical carrier. The first induction magnet is fastened on an outer wall that is of the optical carrier
Data Source
AI summary
A voice coil motor including a first magnetic piece, a second magnetic piece, a third magnetic piece, and a counterweight, with the first magnetic piece, the second magnetic piece, the third magnetic piece, and the counterweight radially and sequentially arranged around an optical carrier, a first plurality of coils symmetrically fastened on two sides of the optical carrier, where the first plurality of coils includes a first coil and a second coil, the first coil is disposed opposite the first magnetic piece, and the second coil is disposed opposite the third magnetic piece, a first magnetic sensor, and a first induction magnet disposed opposite the first magnetic sensor. The first magnetic sensor is disposed on a side of the counterweight that is adjacent to the optical carrier, and the first induction magnet is fastened on an outer wall of the optical carrier that is adjacent to the counterweight.