Position Detection Device Using Dual-Track Interference
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Solution Overview
Problem
Existing position detection devices face errors in determining the position of a moving body due to complex circuit configurations and increased manufacturing costs, especially with multiple tracks, leading to potential erroneous determinations and increased complexity.
Innovation Solution
A position detection device that calculates a reference position using signals from tracks with different cycle lengths, specifies slits within the moving range, and corrects the absolute position using an in-slit position calculation, thereby simplifying the configuration and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase modulation signals are used to extract position within wavelength, then position detection accuracy is improved, but circuit complexity increases due to required modulation circuits
Solution Approach 1:
The patent extracts the essential position information directly from the interference pattern without requiring complex modulation circuits. By using a simple photodetector to detect the interference signal and processing it through basic arithmetic operations (addition, subtraction, division), the system achieves accurate position detection while eliminating the need for complex modulation/demodulation circuitry.
Solution Approach 2:
The patent replaces complex electrical modulation circuits with a simpler optical-mechanical interference system. The position information is encoded in the interference pattern of light waves, and the detection system uses basic photodetection and mathematical processing instead of complex electronic modulation, thereby reducing circuit complexity while maintaining measurement precision.
2Measurement precision
If the number of tracks is increased to improve position detection accuracy, then measurement precision is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent segments the position detection task into two independent components: coarse position detection using track pitch and fine position detection using interference fringes. This segmentation allows the system to achieve high precision without increasing the number of tracks, as the fine position information is derived from the interference pattern rather than additional tracks, thereby reducing manufacturing cost and complexity.
Solution Approach 2:
The patent introduces a new dimension for position measurement by utilizing the interference fringe pattern in addition to the track pitch. Instead of adding more tracks in the same dimension, the system uses the optical interference dimension to provide fine position resolution, effectively achieving high precision measurement without increasing track count or manufacturing complexity.
3Measurement precision
If multiple tracks with different cycles are used, then absolute position determination is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent performs preliminary calculation of the reference position using the second track with larger pitch before determining the final absolute position. This preliminary action provides a coarse reference that simplifies the subsequent fine position determination using the interference pattern from the first track, thereby achieving accurate absolute position determination with a simpler multi-track configuration rather than requiring multiple complex tracks.
Solution Approach 2:
The patent uses the reference position calculated from the second track as an intermediary to facilitate the determination of absolute position. This intermediary reference position serves as a baseline that simplifies the interpretation of the interference pattern from the first track, enabling accurate absolute position determination without requiring complex multi-track processing circuits.
Data Source
AI summary
There is provided a position detection device to suppress an influence of a signal distortion due to a processing error or the like, the position detection device including: a reference position calculation unit that calculates a reference position of a moving body on the basis of a first signal and a second signal, the first signal being detected from a first track provided on the moving body and having a scale of predetermined cycles, and the second signal being detected from a second track provided on the moving body and having a scale of cycles less than the predetermined cycles; a slit specifying unit that specifies a slit corresponding to a position of the moving body; an in-slit position calculation unit that calculates an in-slit position of the moving body in the specified slit; and a correction unit that corrects an absolute position of the moving body.