Grating Measurement Module Using Moiré Imaging for EMI-Resistant Precision
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Solution Overview
Problem
Traditional grating measuring modules are susceptible to measurement errors due to electromagnetic interference when detecting optical signals, which affects the accuracy of displacement measurements in precision machining.
Innovation Solution
The implementation of a grating measuring module with a laser diode light source, collimating device, and image sensing chip, where the first and second gratings with specific patterns and coatings are used to determine displacement, and an image processing unit calculates the displacement based on pixel differences in the images formed on the image sensing chip, reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photodetector is used to receive optical signals in a traditional grating measuring module, then the displacement can be measured through conversion of light and dark stripes into current, but the photodetector is susceptible to electromagnetic interference leading to measurement errors
Solution Approach 1:
The patent replaces the photodetector-based optical signal reception system with an image sensing chip that captures images of moire fringes. Instead of converting light directly to current through a photodetector, the system uses the image sensing chip to detect the spatial pattern of moire fringes, processes the images to extract displacement information. This substitution eliminates the electromagnetic interference susceptibility of photodetectors while maintaining displacement measurement capability through image-based optical pattern analysis.
2Object-affected harmful factors
If an image sensing chip is used instead of a photodetector, then electromagnetic interference is reduced, but the device complexity increases due to additional image processing requirements
Solution Approach 1:
The image sensing chip serves multiple functions: it captures images of moire fringes, provides spatial resolution for pattern detection, and generates digital signals for processing. The image processing unit performs multiple operations including extracting centerlines of moire fringes, calculating displacements based on centerline positions, and determining displacement directions. This multi-functional approach consolidates what would otherwise require separate components into an integrated system, managing complexity while achieving electromagnetic interference resistance.
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 solution enhances the accuracy of displacement measurements by minimizing electromagnetic interference and providing precise calculations of micro-displacement, improving the reliability of precision machining tools.
Implementation Method 1
a laser diode light source
Implementation Method 2
collimating device
Implementation Method 3
the first grating and the second grating with specific patterns and coatings are used to determine displacement, and an image processing unit calculates the displacement based on pixel differences in the images formed on the image sensing chip
Implementation Method 4
image sensing chip, where the first and second gratings with specific patterns and coatings are used to determine displacement
Data Source
AI summary
A grating measuring module includes a light source, a collimating device, a first grating, a second grating, and an image sensing chip. The first grating is arranged on an optical path of the collimating device and the second grating is arranged on an optical path of the first grating. Each of the two gratings comprises a first pattern and a plurality of second patterns locating at the both sides of the first pattern. The first and second gratings can each be attached to an object which may be displaced in relation to another object, so allowing light of a certain pattern to pass depending on the magnitude of the displacement. The image sensing chip arranged on an optical path from the second grating receives light emitted from the light source and forms an image from which a displacement can be calculated and displayed.