Inductive Lens Position Measurement Using AF and OIS Coils
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Solution Overview
Problem
Small form factor cameras face challenges in achieving high image quality due to parasitic motion in degrees of freedom other than the optical axis, necessitating precise position measurement of the lens to compensate for unwanted motion and rotation, which existing technologies often fail to address effectively without additional sensing components.
Innovation Solution
The implementation of a camera system using existing coils for inductive sensing, where an alternating current is applied to the autofocus coil to generate a magnetic field that induces currents in optical image stabilization coils, allowing for three-axis lens position measurement without dedicated sensors, enabling precise control of lens motion along the optical and orthogonal axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional position measurement methods (Hall-effect sensors, external capacitor plates) are used, then lens position can be measured, but device complexity and form factor are increased
Solution Approach 1:
The patent makes the existing coils serve dual functions: their primary function for OIS/AF operation and a secondary function for position sensing. By measuring the inductance changes of these same coils, the system obtains position information without requiring separate sensing components, thus reducing device complexity while maintaining measurement capability
Solution Approach 2:
The coils automatically provide position measurement information through their inherent electrical properties (inductance changes) when subjected to alternating current. The system uses the coils' own characteristics to sense position, eliminating the need for external dedicated sensors and simplifying the overall device architecture
2Measurement precision
If additional dedicated sensing components are added for position measurement, then measurement precision improves, but the camera form factor increases
Solution Approach 1:
The existing coils in the camera module are made to perform multiple functions: optical image stabilization, autofocus, and position sensing. By utilizing the inductance characteristics of these same coils, the patent achieves three-axis position measurement without adding dedicated sensing components, thereby maintaining a compact camera form factor
Solution Approach 2:
The patent combines the position sensing function with the existing coil structure. Instead of separating sensing components from actuation components, the invention merges these functions into a single integrated system where the coils serve both actuation and sensing purposes, reducing the overall camera module volume
3Device complexity
If lens position is not precisely controlled, then device complexity is reduced, but image quality deteriorates due to parasitic motion
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the inductance changes of the coils, which reflect the actual lens position. This position information is fed back to the control system, enabling closed-loop control that precisely manages lens motion along the optical axis while minimizing parasitic motion, all without significantly increasing device complexity
Solution Approach 2:
The patent replaces complex mechanical position sensing mechanisms with an electrical measurement approach. By measuring the electrical inductance characteristics of the coils, the system obtains precise position information without requiring additional mechanical components, thus maintaining system simplicity while achieving the required motion control precision
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 enables accurate and efficient three-axis lens position measurement, reducing image capture noise and allowing for closed-loop feedback control, thereby enhancing image quality by minimizing parasitic motion and compensating for user-induced handshake and environmental disturbances.
Implementation Method 1
an alternating current is applied to the autofocus coil to generate a magnetic field that induces currents in optical image stabilization coils
Data Source
AI summary
Some embodiments include a camera of a mobile computing device. In some embodiments, the camera includes an autofocus coil for moving a lens module, a plurality of optical image stabilization coils, a driver circuit element, connected to the autofocus coil, for passing an alternating current waveform through the autofocus coil, and one or more measurement circuit elements, connected to respective ones of the plurality of the optical image stabilization coils, for measuring changes induced in currents in the respective ones of the plurality of the optical image stabilization coils by the waveform.