Piezoelectric Lens Actuator Module with Inline Preload
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Solution Overview
Problem
Existing lens actuator modules in digital cameras face limitations such as high power consumption, non-straight flexure movement causing angular tilt, low strength, slow stepping, and sensitivity to gravity orientation, which result in inconsistent focus and delayed image capture, especially in high-resolution cameras.
Innovation Solution
A lens actuator module utilizing a linear piezoelectric motor with a preload force applied in-line and perpendicular to the drive force, optimizing the bearing guide properties to achieve high force efficiency, safety factor, and speed ratio, while eliminating the need for special low-friction materials and complex manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voice coil motor (VCM) is used to drive the lens, then the lens can be suspended and positioned, but high power consumption occurs due to continuous current required to hold the lens position
Solution Approach 1:
The patent employs periodic ultrasonic vibrations at resonant frequency to drive the lens back and forth. The piezoelectric element generates periodic mechanical vibrations that, through friction coupling with the drive surface, produce the desired lens movement. This periodic action eliminates the need for continuous power consumption to maintain position, as the system only consumes energy during the vibration cycles.
Solution Approach 2:
The invention utilizes mechanical vibrations from a piezoelectric ultrasonic actuator to drive the lens. The piezoelectric element converts electrical energy to mechanical vibrations at ultrasonic frequencies, which are then transferred to the lens through a friction coupling mechanism. This vibration-based drive mechanism replaces the continuous electromagnetic force of VCM, dramatically reducing power consumption while maintaining positioning capability.
2Reliability
If a VCM is used with a flexure guide assembly, then the lens can be held at fixed position, but non-straight flexure movement causes angular tilt between the lens and image plane
Solution Approach 1:
The patent replaces the flexure guide mechanical system with a direct linear drive mechanism. Instead of using flexible beams that inherently produce curved motion paths and angular tilt, the invention uses a piezoelectric actuator with a friction coupling drive surface that moves the lens in a straight line parallel to the optical axis. This substitution eliminates the angular tilt problem while maintaining positioning stability.
Solution Approach 2:
Rather than guiding the lens movement through a flexible structure that constrains motion, the invention inverts the approach by using a rigid linear guide with a friction-based drive mechanism. The drive surface moves linearly, and friction coupling transfers this motion to the lens, ensuring straight-line movement without angular deviation. This inverted approach to achieving controlled motion eliminates the alignment issues inherent in flexure-based systems.
3Reliability
If a VCM with slow stepping movement is used, then the lens can be positioned, but oscillations extend the focus time and delay the time to take a picture
Solution Approach 1:
The patent uses periodic ultrasonic vibrations at resonant frequency to drive the lens, enabling rapid back-and-forth motion. The resonant frequency operation allows the system to achieve the required focus travel distance in minimal cycles, dramatically reducing focus time compared to slow VCM stepping. The periodic nature of the vibration also ensures smooth, oscillation-free movement once the target position is reached.
Solution Approach 2:
The invention changes the operating parameters from slow, continuous VCM stepping to high-frequency ultrasonic vibrations. By operating the piezoelectric actuator at its resonant frequency, the system achieves maximum speed and efficiency. The ultrasonic vibration frequency (typically 20-100 kHz) is much higher than VCM stepping frequencies, enabling the lens to reach focus positions rapidly without the oscillations that plague slower stepping mechanisms.
4Speed
If a piezo motor is used with friction contact, then fast and precise lens motion can be achieved, but significant friction outside the contact point must be avoided to maintain reliable motion
Solution Approach 1:
The patent applies local quality by creating a specialized friction coupling interface with specific surface properties at the contact point. The drive surface and contacting surface are designed with particular roughness, material composition, and geometry to optimize friction coupling only where needed. This localized friction generation allows rapid motion while preventing unwanted friction elsewhere in the mechanism that would compromise reliability.
Solution Approach 2:
The invention introduces a friction coupling interface as an intermediary between the piezoelectric actuator and the lens. This intermediate drive surface acts as a mediator that converts the ultrasonic vibrations into reliable friction-driven motion. The intermediary surface is specifically designed to provide controlled friction coupling, enabling fast response while maintaining motion reliability through optimized surface properties and geometric configuration.
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 provides fast, precise, and robust lens motion with improved focus accuracy and reduced sensitivity to gravity, enabling efficient and cost-effective manufacturing for high-volume production.
Implementation Method 1
A lens actuator module utilizes a linear piezoelectric motor
Implementation Method 2
A lens actuator module includes a linear actuator and a lens carriage frictionally coupled to the linear actuator at a contact point using a preload force
Data Source
AI summary
A lens actuator module includes a lens assembly with an optical centerline and a clear aperture, a bearing guide integrated adjacent to the clear aperture with the centerline of motion substantially parallel to the optical centerline, a linear actuator with a preloaded frictional contact point that moves the lens along the centerline. The preload force is perpendicular to the optical centerline, constant and generated in-line with the contact point such that the preload force produces substantially zero additional friction in the bearing guide irrespective of the location along the optical centerline.