Differential Position Sensing Circuit for Noise-Resistant Lens Control
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Solution Overview
Problem
Conventional position sensing devices using two coils and oscillation circuits face complexity, increased manufacturing costs, and errors due to frequency differences and temperature compensation issues, while single coil methods require multiple circuits and are prone to noise interference.
Innovation Solution
A differential sensing coil unit with two coils having variable inductances that maintain a constant sum, a shared differential oscillation circuit generating signals with opposite phases, and a signal processing circuit calculating position values from detected amplitudes to remove common noise and facilitate temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two separate oscillation circuits are used to process inductance of two sensing coils, then sensing capability is improved, but device complexity increases and manufacturing costs increase
Solution Approach 1:
The patent combines two separate oscillation circuits into a single differential oscillation circuit that processes both sensing coils simultaneously. The differential oscillation circuit generates two oscillation signals with opposite phases, allowing both coils to be processed through one unified circuit structure, thereby reducing device complexity while maintaining sensing capability.
Solution Approach 2:
The differential oscillation circuit serves multiple functions: it generates oscillation signals for both sensing coils, provides temperature compensation through differential measurement, and enables position detection. This multi-functional design eliminates the need for separate dedicated circuits for each coil, reducing overall system complexity.
2Reliability
If two separate oscillation circuits are used with different oscillation frequencies, then mutual interference is avoided, but temperature compensation errors occur due to frequency differences
Solution Approach 1:
The differential oscillation circuit generates two oscillation signals with opposite phases at the same frequency. This periodic action with opposite phases allows the system to avoid mutual interference while maintaining identical frequency characteristics, enabling accurate temperature compensation through differential measurement of the two signals.
Solution Approach 2:
The patent uses opposite-phase oscillation signals as counterbalancing measurements. By generating signals with equal amplitude but opposite phases, the system can subtract common-mode noise and temperature drift effects, achieving accurate temperature compensation while avoiding mutual interference between the two sensing coils.
3Device complexity
If a single coil and single oscillation circuit are used, then device complexity is reduced, but noise interference increases and temperature compensation becomes difficult
Solution Approach 1:
The patent merges two sensing coils into a differential configuration where both coils share a common oscillation circuit. This unified approach reduces device complexity compared to using separate circuits, while the differential arrangement inherently rejects common-mode noise and enables temperature compensation through comparative measurement.
Solution Approach 2:
The patent converts the potential harm of using a single shared oscillation circuit (which could cause mutual interference) into a benefit by using differential signaling. The opposite-phase signals allow the system to reject common-mode noise and temperature drift, turning what could be a source of interference into a mechanism for noise rejection and temperature compensation.
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 simplifies the circuitry, reduces noise and temperature-related errors, and enables precise position sensing without frequency interference, thereby improving the accuracy and cost-effectiveness of position detection.
Implementation Method 1
a differential oscillation circuit generating a first oscillation signal having a first amplitude based on a first inductance of the first sensing coil, which is variable according to positional movement of a conductor, and a second oscillation signal having a second amplitude based on a second inductance of the second sensing coil
Data Source
AI summary
A position sensing circuit that can be used with a position control device including a differential sensing coil unit having a first sensing coil and a second sensing coil disposed to face a conductor disposed on one side of a lens barrel. The position sensing circuit includes: a differential oscillation circuit generating a first oscillation signal having a first amplitude based on a first inductance of the first sensing coil, variable according to positional movement of the conductor, and a second oscillation signal having a second amplitude based on a second inductance of the second sensing coil, variable according to positional movement of the conductor; an amplitude detection circuit detecting the first amplitude of the first oscillation signal and the second amplitude of the second oscillation signal; and a signal processing circuit calculating the first amplitude and the second amplitude to calculate a position value.