Lens Moving Coil Sensing for Low-Noise Autofocus Control
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Solution Overview
Problem
Existing camera modules face challenges in reducing noise induced in coils and improving autofocus accuracy, particularly in small electronic devices like smartphones, where vibrations can blur images and affect autofocus performance.
Innovation Solution
A lens moving apparatus is designed with a housing, bobbin, coils, magnets, sensing coils, and a circuit board with amplifiers to detect and control induced voltages, reducing noise and enhancing autofocus accuracy by using a detector to compare induced voltages and control bobbin displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a second coil is added to detect bobbin displacement for autofocus, then measurement precision is improved, but noise generated in the second coil worsens the signal quality
Solution Approach 1:
A third coil is introduced as an intermediary sensing element that detects the magnetic field generated by the first coil. This third coil is positioned to sense only the driving field without being subjected to the same mechanical vibrations and noise as the second coil, thereby providing a cleaner reference signal for autofocus control.
Solution Approach 2:
The detection function is separated into two independent coils: the second coil remains dedicated to detecting bobbin displacement, while the third coil is extracted to specifically detect the magnetic field generated by the first coil. This separation allows each coil to be optimized for its specific function and reduces cross-interference and noise.
2Stability of the object's composition
If vibration damping structures are added to reduce handshake impact, then stability is improved, but device complexity increases
Solution Approach 1:
The vibration damping function is merged with the existing magnetic field generation structure. The first coil serves dual purposes: generating the magnetic field for autofocus and acting as part of the vibration damping system through its electromagnetic interaction with the second coil. This eliminates the need for separate mechanical damping structures.
Solution Approach 2:
Mechanical vibration damping structures are replaced with an electromagnetic damping system. The interaction between the first coil (driving coil) and the second coil (sensing coil) creates electromagnetic forces that naturally counteract vibrations, providing damping without mechanical components.
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 effectively reduces noise and improves autofocus accuracy, ensuring clearer images and more precise autofocus operations in camera modules, even in environments prone to vibration.
Implementation Method 1
a first sensing coil disposed on the housing to generate a first induced voltage by interaction with the first coil
Implementation Method 2
a second sensing coil disposed in the housing to generate a second induced voltage by interaction with the first coil
Data Source
AI summary
An embodiment comprises: a housing; a bobbin disposed in the housing; a first coil disposed on the bobbin; a magnet disposed on the housing; a first sensing coil, disposed on the housing, for generating a first induced voltage by interacting with the first coil; a first circuit board connected to the first coil and the first sensing coil; and a first amplifier, disposed on the first circuit board, for amplifying the first induced voltage of the first sensing coil and outputting a first amplified signal.