Position Detecting Device With Differential Amplifier For OIS Accuracy
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Solution Overview
Problem
Existing position detecting devices using magnetic sensors face accuracy issues when the positional relationship between the magnetic sensor and sense magnet changes due to optical image stabilizer mechanisms, which are not addressed by existing configurations.
Innovation Solution
A method involving two sets of sense magnets and magnetic sensors that move integrally with the detection target, with the sensors positioned outside the movable range, and a differential amplifier to correct and amplify the difference in magnetic field detection signals, ensuring accurate position detection even when the positional relationship changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a magnetic sensor is fixed at a predetermined place to detect lens position, then the device structure is simple, but position detection accuracy deteriorates when the sense magnet moves due to OIS
Solution Approach 1:
The patent applies the Dynamics principle by making the magnetic sensor movable rather than fixed. The sensor is positioned on the lens holder to move together with the lens during OIS operation, maintaining a constant positional relationship with the sense magnet. This dynamic adjustment resolves the contradiction by allowing simple device structure while preserving position detection accuracy through coordinated movement.
2Measurement precision
If multiple magnetic sensors are used to reduce noise magnetic field influence, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent applies the Self-service principle by using the moving magnetic sensor to simultaneously achieve multiple functions: it detects the lens position while its movement with the lens during OIS automatically compensates for positional changes relative to the sense magnet. This eliminates the need for additional sensors or complex correction mechanisms, resolving the contradiction by achieving high measurement precision without increasing device complexity.
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 configuration effectively maintains position detection accuracy by canceling changes in the composite magnetic fields, allowing for precise detection of the lens position despite movements perpendicular to its optical axis, reducing complexity and cost in the camera module.
Implementation Method 1
a magnetic sensor that is applied to a composite magnetic field of the driving magnetic field generated by the driving magnet and the sense magnetic field generated by the sense magnet
Implementation Method 2
amplifying the difference between the detection signals of the magnetic field output from the first magnetic detecting circuit and the second magnetic detecting circuit by a differential amplifier
Data Source
AI summary
The position detecting device of the present invention is a device for detecting the position of a movable detection target within a predetermined movable range. The position detecting device comprises: a first magnet (13A) and a second magnet (13B) which are arranged so as to move integrally with the movement of the detection target; a first magnetic detecting circuit (20A) that detects the magnetic field of the first magnet (13A) and a second magnetic detecting circuit (20B) that detects the magnetic field of the second magnet (13B), which are arranged at positions outside the movable range; and a differential amplifier (8) that amplifies the difference between the detection signals of the magnetic field output from the first magnetic detecting circuit (20A) and the second magnetic detecting circuit (20B), and that outputs the amplified difference of the signal as a position detecting signal of the detection target.