Autofocus Actuator Capacitive Sensing for Compact Position Control
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Solution Overview
Problem
Existing autofocus actuators in cameras face challenges in achieving high speed, high accuracy, and low cost due to the increased cost and form factor associated with the implementation of magnetic field sensors.
Innovation Solution
The use of capacitance sensing between a rotor plate attached to a rotor and a stator plate attached to a stator in the autofocus actuator to measure the actual position, reducing the cost and form factor by eliminating the need for magnetic field sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic field sensors are implemented in the autofocus actuator to measure actual position, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces magnetic field sensors with a capacitance sensing system that uses electrical fields to detect rotor position. The stator plate and rotor plate form a capacitor where capacitance changes as the rotor moves, providing position information without requiring magnetic field detection hardware. This substitution eliminates the need for magnetic field sensors while maintaining measurement capability.
Solution Approach 2:
The patent introduces capacitance as an intermediary parameter to measure rotor position. Instead of directly measuring magnetic field changes, the system measures capacitance variations between the stator plate and rotor plate, which change as the rotor moves. This intermediary measurement approach simplifies the sensing mechanism while providing accurate position data.
2Measurement precision
If magnetic field sensors are implemented in the autofocus actuator to measure actual position, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent replaces expensive magnetic field sensors with a capacitance sensing system that can be implemented using standard electronic circuits. The capacitance sensing approach uses the existing stator and rotor structures as capacitor plates, eliminating the need for specialized magnetic field detection components and reducing manufacturing costs.
Solution Approach 2:
The patent makes the stator plate and rotor plate serve dual functions: they are both functional components of the electromagnetic actuator and the sensing elements for position detection. By using the existing structural components as capacitor plates, the system eliminates the need for separate sensing components, reducing overall system cost.
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 approach allows for reduced costs and form factor while maintaining high speed and accuracy in the autofocus process, enhancing the efficiency of the autofocus actuator.
Implementation Method 1
measuring, at a capacitance sensing circuit, the capacitance between the rotor plate and the stator plate
Data Source
AI summary
In accordance with the present disclosure, a method for controlling an autofocus actuator is provided such that the actual position of the autofocus actuator can be measured using capacitance sensing. In some embodiments, a rotor plate attached to a rotor and a stator plate attached to a stator in the autofocus actuator can be used to create a capacitance. When the rotor moves, a capacitance change value between the rotor plate and the stator plate can be measured. In these embodiments, the cost and the form factor of the aforementioned autofocus actuator are reduced compared to implementation of magnetic field sensors in the autofocus actuator.