Lens Position Detection Using Multi-Scale Magnetic Averaging
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Solution Overview
Problem
Existing lens devices with annular magnetic recording media face challenges in precise position detection due to signal unevenness and insertion errors, particularly in large aperture lenses, leading to inaccurate phase difference calculations and increased manufacturing costs.
Innovation Solution
A lens device with a rotary member featuring first and second magnetic recording scales of different wavelengths, where signals are detected and phase differences calculated over multiple cycles to average and determine the absolute position of the movable optical element, reducing the impact of signal unevenness and insertion errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a hollow annular magnetic recording medium is used in a lens device with large aperture, then the lens device can achieve large aperture performance, but signal unevenness is easily generated in the magnetic signal
Solution Approach 1:
The patent divides the magnetic signal detection into multiple segments by using multiple MR sensors arranged around the annular magnetic recording medium. Each sensor detects signals from different angular positions, and the control unit processes these segmented signals to calculate average values, thereby compensating for local signal unevenness caused by the hollow structure and insertion errors.
2Volume of moving object
If the position detector is inserted in the lens device with small gap for compact size, then the lens device achieves small size and light weight, but insertion error occurs causing magnetic signal unevenness
Solution Approach 1:
The control unit implements a feedback mechanism by continuously monitoring the magnetic signals from multiple MR sensors and calculating average values to compensate for insertion errors. The system uses the detected phase differences and signal averages to correct position detection accuracy, thereby mitigating the effects of insertion errors while maintaining compact dimensions.
3Measurement precision
If multiple MR sensors are provided for each annular magnetic recording medium to improve detection precision, then absolute position detection accuracy is increased, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the detection data from multiple MR sensors by calculating average values of the magnetic signals in the control unit. This combining approach maintains high position detection accuracy through multi-sensor data fusion while simplifying the overall system architecture and reducing manufacturing complexity compared to using independent processing channels for each sensor.
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 precise and cost-effective absolute position detection of movable optical elements with a simplified configuration, improving accuracy and reducing manufacturing costs by averaging phase differences over multiple cycles.
Implementation Method 1
two MR sensors which detect signals corresponding to the magnetic signals of the two annular magnetic recording media
Data Source
AI summary
A lens device includes a movable optical element, a rotary member; first and second magnetic recording scales fixedly disposed on an outer periphery of the rotary member to extend along a peripheral direction of the rotary member; a signal detecting unit which detects first to fourth signals; and a position detecting unit which detects a position of the movable optical element based on the detected signals, in which the position detecting unit includes: a phase difference calculating unit which calculates a phase difference between the first signal and the third signal, based on the detected first to fourth signals for one cycle; a phase average calculating unit which calculates an average of the phase differences respectively calculated for n cycles; and an absolute position detecting unit which detects an absolute position of the movable optical element based on the calculated average.