Lens Drive Roller Guidance for Faster Miniature Autofocus
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lens moving apparatuses face challenges in miniaturization, speed of AF operation, and the range of magnet and coil sizes, particularly in subminiature camera modules, and there is a need for improved guidance mechanisms for the bobbin during autofocus operations.
Innovation Solution
The lens moving apparatus employs rollers instead of leaf springs to guide the bobbin in the optical-axis direction, with a novel configuration that includes a first and second roller unit in contact with specific grooves, a magnetic body to generate attractive force, and a circuit board connected to the coil, enhancing the bobbin's movement and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a voice coil motor (VCM) is used in existing general camera modules, then the actuator can drive the lens for autofocus, but it is difficult to apply to subminiature, low-power camera modules
Solution Approach 1:
The actuator is divided into separate functional components: a magnet fixed to the bobbin and a coil fixed to the housing. This segmentation allows independent optimization of each component and enables the use of smaller, more efficient magnetic elements suitable for subminiature camera modules while maintaining reliable autofocus operation.
Solution Approach 2:
The conventional VCM configuration is inverted by fixing the magnet to the moving bobbin and the coil to the stationary housing, rather than the traditional arrangement. This inversion optimizes the magnetic circuit for miniaturization while maintaining the electromagnetic driving force necessary for reliable autofocus operation in low-power applications.
2Speed
If the bobbin is guided using a leaf spring, then the bobbin is supported during movement, but the guidance mechanism increases device complexity and reduces AF speed
Solution Approach 1:
The leaf spring guidance mechanism is extracted and replaced with roller units that run in grooves. This extraction eliminates the complex elastic deformation characteristics of leaf springs while providing positive mechanical guidance through the groove-roller interface, resulting in faster and more reliable autofocus operation.
Solution Approach 2:
The elastic mechanical guidance system (leaf spring) is replaced with a constrained mechanical guidance system (grooves and rollers). This substitution provides more precise control over bobbin movement paths, reduces energy loss through elastic deformation, and increases autofocus speed while maintaining guidance functionality.
3Volume of moving object
If the magnet and coil sizes are limited, then the actuator fits in subminiature camera modules, but the driving force for AF operation is reduced
Solution Approach 1:
The magnetic circuit is optimized with local quality enhancements by positioning the magnet and coil in specific configurations that maximize magnetic flux density in the air gap. The magnet is fixed to the bobbin and the coil to the housing with precise spacing, creating high-density magnetic fields that generate sufficient driving force despite the small overall size of the components.
Solution Approach 2:
The electromagnetic driving force is enhanced by optimizing parameters such as magnet strength, coil turns, and air gap distance. By carefully controlling these parameters within the constraints of miniaturization, the system achieves adequate driving force for autofocus operation while maintaining small component sizes suitable for subminiature camera modules.
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 improves the speed of autofocus operations, suppresses bobbin movement, and increases the range of magnet and coil sizes, thereby enhancing the performance of camera modules and optical devices.
Implementation Method 1
a coil disposed between the first post and the second post so as to correspond to the magnet
Implementation Method 2
a magnetic body disposed at the base under the coil so as to generate attractive force in cooperation with the magnet
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An embodiment comprises: a base which comprises a body and a first column part, a second column part, a third column part, and a fourth column part arranged at corner parts of the body, respectively; a bobbin disposed on the body; a first roller part disposed in a first groove provided on the first column part; a second roller part disposed in a second groove provided on the second column part adjacent to the first column part; a magnet disposed on the bobbin; and a coil corresponding to the magnet and disposed between the first and the second column part, wherein the first roller part contacts at least two areas of the first groove, the second roller part contacts at least two areas of the second groove, the first groove comprises a first opening through which a part of the first roller part is exposed, the second groove comprises a second opening through which a part of the second roller part is exposed, and the bobbin comprises a first support part disposed in the first opening and contacting the first roller part and a second support part disposed in the second opening and contacting the second roller part.