Camera Module Capacitive Auto Focus Actuation
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Solution Overview
Problem
Camera modules using voice coil motor actuators face manufacturing difficulties due to complex electrical connections and slow auto-focus times, often resulting in inaccurate focus positions due to hysteresis and structural friction.
Innovation Solution
A camera module design that simplifies electrical connections by using a spring between a fixed unit and a movable unit, maintains a minimum gap between coils for accurate displacement detection, and incorporates a damper to reduce natural oscillation, allowing for quick and accurate auto-focus using a fixed coil and movable coil configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hall sensor is used to detect magnetic flux for auto-focus, then the auto-focus position can be measured, but the manufacturing process becomes complex due to requiring 4 power source connections and 6 connectors
Solution Approach 1:
The patent replaces the hall sensor-based magnetic flux detection system with a capacitive sensing system. Instead of using permanent magnets and hall sensors that require complex electrical connections, the invention uses a fixed electrode and movable electrode configuration where the movable electrode is coupled to the lens module. This capacitive approach eliminates the need for multiple power source connections and connectors, simplifying the manufacturing process while maintaining measurement capability.
2Force
If a voice coil motor with hall sensor is used, then the lens module can be driven by Lorenz Force, but the auto-focus time becomes considerable and position errors occur due to hysteresis and structural friction
Solution Approach 1:
The patent replaces the voice coil motor actuation system with a direct capacitive actuation system. Instead of using Lorenz Force from a voice coil motor that suffers from hysteresis and friction, the invention applies electrostatic force directly between the fixed electrode and movable electrode. This eliminates the mechanical transmission components that cause hysteresis and structural friction, enabling faster and more accurate auto-focus response.
Solution Approach 2:
The patent changes the fundamental actuation mechanism from magnetic field-based (voice coil motor) to electric field-based (capacitive actuation). By changing the physical parameter from magnetic flux to capacitance, the system achieves direct coupling between the control signal and lens module position, eliminating the time delays and position errors associated with magnetic hysteresis and mechanical friction.
3Volume of moving object
If the camera module is downsized with ultra-precision lenses, then the mobile terminal can be compact, but the auto-focus system becomes more difficult to design and manufacture
Solution Approach 1:
The patent merges the auto-focus actuation and detection functions into a single capacitive sensor structure. The fixed electrode and movable electrode serve dual purposes: they both actuate the lens module through electrostatic force and detect its position through capacitance changes. This integration eliminates the need for separate hall sensors, permanent magnets, and complex connector assemblies, making the system suitable for downsized camera modules while reducing design and manufacturing complexity.
Solution Approach 2:
The patent implements multi-functionality in the electrode structure, where the same fixed electrode and movable electrode configuration serves both as the actuation mechanism (through applied voltage) and the detection mechanism (through capacitance measurement). This universal structure eliminates the need for separate components, reducing the overall device complexity and making it ideal for compact camera modules in mobile terminals.
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 enables rapid and precise auto-focus, reduces manufacturing complexity, and enhances the camera module's thickness reduction, supporting various focus schemes based on user requests or environmental brightness.
Implementation Method 1
a fixed coil arranged in the fixing unit and configured to receive from the moving coil a current or voltage variable based on a distance with the moving coil
Implementation Method 2
a spring arranged between the moving unit and the fixing unit and configured to restore the moving unit to an initial position
Implementation Method 3
a damper arranged between the spring and the fixing unit and configured to reduce natural oscillation of the spring
Data Source
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AI summary
The present invention includes a fixed unit (100) having a perforated hole formed therein, a movable unit (200) including at least one lens (210), the movable unit (200) configured to linearly move in the perforated hole of the fixed unit (100), a movable coil (220) disposed on a surface of the movable unit (200), and a fixed coil (120) disposed on a surface of the fixed unit (100), the fixed coil (120) configured to receive from the movable coil (220) an induced current or voltage according to a distance from the movable coil (220), wherein the movable coil (220) receives a current or a voltage via a first wiring (310) and a second wiring (320) for moving the movable unit (200), and wherein the fixed coil (120) outputs a current or a voltage via a third wiring (330) and a fourth wiring (340) based on the received induced current or voltage from the movable coil (120).