Focus Lens Assembly Stabilization via Mechanical Stop Damping
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Solution Overview
Problem
The stability of focus lens assemblies in digital camera modules, particularly in mobile apparatuses, is compromised by vibrations during exposure, leading to image quality issues such as focus wobble and blur, especially in rolling shutter exposure modes.
Innovation Solution
The focus lens assembly is moved against a mechanical stop and then stabilized for a period before being moved to a frame focus position, reducing vibrations and improving stability by forcing it against the stop during this period, and gradually reducing speed when approaching the stop to prevent bouncing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focus lens assembly is moved to a frame focus position for exposure, then the focus distance is adjusted correctly, but vibrations cause the lens to become unstable during exposure
Solution Approach 1:
The patent applies preliminary action by moving the focus lens assembly against a mechanical stop before the actual exposure to eliminate vibrations. The lens is first driven to contact the stop, held there for a stabilizing period, then moved to the final frame focus position. This preliminary stabilization action ensures the lens is vibration-free before exposure begins, resolving the contradiction between achieving accurate focus positioning and maintaining stability during exposure.
2Speed
If the focus lens assembly is rapidly positioned to achieve focus, then the focusing speed is improved, but vibrations and bouncing occur reducing image quality
Solution Approach 1:
The patent implements beforehand cushioning by introducing a stabilizing period during which the focus lens assembly is held against the mechanical stop. This cushioning period allows vibrations to dampen naturally before the lens is moved to its final position for exposure. The approach cushions the impact of rapid positioning movements, preventing bouncing and vibrations that would otherwise degrade image quality while maintaining fast focusing capability.
3Productivity
If continuous AF operation is performed for multiple frames, then the productivity is improved, but accumulated errors in lens position assumption reduce accuracy
Solution Approach 1:
The patent applies self-service by using the mechanical stop as a reference point that the focus lens assembly can return to autonomously after a predetermined number of AF operations or frames. Instead of requiring external intervention or complex error correction algorithms, the system automatically resets the lens position by driving it against the stop, which provides a reliable physical reference. This self-correcting mechanism maintains position accuracy throughout continuous capture sequences while preserving high productivity.
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 method enhances lens stability, reducing focus wobble and improving image quality by damping vibrations, resulting in sharper images across the entire image area during both still and video captures.
Implementation Method 1
a stabilizing period is added between moving the focus lens assembly against the mechanical stop, and moving the focus lens assembly from the mechanical stop
Data Source
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AI summary
A method for positioning a focus lens assembly, the focus lens assembly being movable along an optical axis relative to an image sensor, comprises: moving the focus lens assembly against a mechanical stop; and moving the focus lens assembly from the mechanical stop to a frame focus position for exposure of a frame.