Miniature Camera Lens Control Using Piezoelectric Zoom and Focus
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Solution Overview
Problem
Miniature lens systems face challenges in accurately controlling autofocus (AF) and optical zoom (OZ) due to interference between magnetic fields of Voice Coil motors, requiring complex closed-loop systems and high power consumption, especially in miniature cameras like mobile phones and laptops.
Innovation Solution
Utilizing piezoelectric motors driven by voltage signals for precise positioning of optical lens groups, combined with a drive unit that uses predetermined lens positioning data to directly control AF and OZ operations, eliminating the need for additional autofocus procedures and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Voice Coil motors are used for autofocus and optical zoom in miniature lens systems, then lens groups can be moved along the optical axis, but magnetic field interference between motors reduces positioning accuracy and requires complex closed-loop control systems
Solution Approach 1:
The patent replaces Voice Coil motors with piezoelectric motors for driving the lens groups. Piezoelectric motors use piezoelectric expansion and contraction to generate mechanical motion directly, eliminating the electromagnetic mechanisms that cause magnetic field interference. This substitution maintains the ability to move lens groups along the optical axis while removing the source of magnetic interference, thereby simplifying the control system and improving positioning accuracy without requiring complex closed-loop compensation.
Solution Approach 2:
The patent extracts and removes the magnetic field interference problem by eliminating Voice Coil motors from the system. By taking out the electromagnetic actuation mechanism and replacing it with a piezoelectric-based system, the harmful magnetic interactions between motors are completely removed, allowing for simpler control architecture and more precise positioning.
2Length of moving object
If Voice Coil motors with long stroke length are used for optical zoom, then larger zoom range can be achieved, but positioning accuracy deteriorates
Solution Approach 1:
The patent replaces Voice Coil motors with piezoelectric motors that can achieve the required stroke length through stacked piezoelectric elements or mechanical amplification mechanisms. Piezoelectric motors inherently provide higher positioning accuracy due to their direct drive mechanism and lack of backlash, maintaining precision even over longer travel distances. The piezoelectric expansion/contraction allows for controlled linear motion that combines both long stroke capability and high positioning accuracy.
3Measurement precision
If closed-loop autofocus control system is implemented to compensate for magnetic field interference, then positioning accuracy is maintained, but power consumption increases
Solution Approach 1:
The patent replaces Voice Coil motors with piezoelectric motors, which are inherently more energy efficient for precision positioning tasks. Piezoelectric motors consume power primarily during position changes and maintain position with minimal or zero power consumption, unlike Voice Coil motors that require continuous current to maintain position against spring forces and friction. This substitution eliminates the need for high-power continuous operation, significantly reducing overall power consumption while maintaining accurate positioning.
Solution Approach 2:
The piezoelectric motor system is self-sufficient in maintaining position without requiring continuous external energy input. Once a lens group is positioned at the desired location, the piezoelectric actuator maintains that position through its inherent mechanical properties without consuming additional power, making the system self-servicing in terms of position holding.
4Adaptability or versatility
If two independent Voice Coil motors are used to move lens groups without magnetic field interference, then independent autofocus and zoom operations are possible, but device complexity and cost increase
Solution Approach 1:
The patent replaces Voice Coil motors with piezoelectric motors, which do not generate magnetic fields and therefore do not interfere with each other. This allows multiple piezoelectric motors to operate independently in close proximity without the magnetic field interference problems that plague Voice Coil systems. Each piezoelectric motor can be precisely controlled to move its associated lens group independently, enabling both autofocus and optical zoom operations simultaneously without requiring complex shielding or spacing arrangements.
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
Enables simple and accurate control of AF and OZ in miniature lens systems, allowing for efficient power management and simplified system interactions, particularly suitable for mobile devices.
Implementation Method 1
Utilizing piezoelectric motors driven by voltage signals for precise positioning of optical lens groups
Data Source
AI summary
A method for driving an optical lens system having a first and a second group of optical lenses movable along a linear path parallel to an optical axis by a first and second motor, respectively, and a drive unit, comprises reading (S2, S4) of a present position of the groups and communicating (S6) it to the drive unit. In the drive unit, a command representing a requested optical zoom degree and/or a requested focusing distance is received (S10). Requested positions of the groups, corresponding to the received command, are deduced (S20) by utilizing predetermined lens positioning data available in the drive unit. The predetermined lens positioning data represents positions of the groups causing different combinations of optical zoom degree and focusing distance. The motors are driven (S30, S32) to move the groups to the respective requested positions. The driving comprises applying (S31, S33) of voltage signals over electromechanical materials.