Phase-Shifting Shadow Moiré Surface Topography Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring surface flatness, particularly in transparent materials like light guide plates, are inefficient and damage the materials due to the need for reflective painting, and existing systems are not suitable for real-time, on-line measurement of continuously moving samples.
Innovation Solution
The phase-shifting shadow moiré method involves projecting a light beam with varying incident angles onto a substrate with a grating, capturing fringe pattern images, and using image correction to recover skewed patterns, allowing for the calculation of out-of-plane displacement and surface topography without painting, using a system comprising a light source, reference grating, image acquisition apparatus, and computer for real-time processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reflective paint is sprayed on the transparent object surface to make interference fringe pattern visible, then the visibility of fringe pattern is improved, but the object may be damaged or cannot be reused
Solution Approach 1:
The patent introduces a reference grating as an intermediary element that enables fringe pattern generation without direct modification of the transparent object. The grating serves as a mediator between the light source and the object surface, creating the necessary interference pattern through its periodic structure rather than requiring painted markers on the object itself.
Solution Approach 2:
The patent replaces the mechanical/chemical process of painting and de-painting transparent objects with an optical system using a reference grating and light beams. This substitution eliminates the harmful mechanical and chemical effects of paint application while achieving the same goal of making surface topography visible through interference fringes.
2Measurement precision
If conventional shadow moiré method is used to measure transparent materials, then surface topography can be measured, but the measurement process is time-consuming and not suitable for real-time measurement
Solution Approach 1:
The patent employs phase-shifting technology that introduces periodic variations in the reference grating's position or orientation, creating a series of interferograms at different phase states. This periodic action enables the extraction of complete surface topography information through mathematical processing of multiple phase-shifted fringes, significantly improving measurement speed and enabling real-time analysis.
Solution Approach 2:
The patent implements a continuous measurement system where the light source continuously illuminates the object, the reference grating continuously generates interference patterns, and the detector continuously captures fringe images. This continuous operation, combined with real-time phase-shifting and processing, enables real-time surface topography measurement without interruption or repeated setup.
3Productivity
If a grating is positioned at a non-zero angle with respect to the plane of conveyance to measure continuously moving samples, then on-line measurement is enabled, but the fringe pattern becomes skewed and requires correction
Solution Approach 1:
The patent incorporates image correction processing that analyzes the skewed fringe patterns generated by the angled grating configuration and applies mathematical transformations to restore accurate surface topography information. This feedback loop continuously corrects the distortion introduced by the angled setup, maintaining measurement precision while enabling on-line operation of continuously moving samples.
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 method enables efficient, cost-effective, and non-destructive real-time measurement of surface topography and out-of-plane deformation in transparent objects, such as light guide plates, by generating high-contrast interference fringe patterns and correcting skewed images, ensuring accurate determination of surface topography without damaging the materials.
Implementation Method 1
the light beam pass through the grating onto the flat surface and is reflected to pass the grating again for forming a fringe pattern image
Implementation Method 2
receiving the reflected light from the substrate at other side of the normal of the grating
Implementation Method 3
phase-shifting shadow moiré method
Implementation Method 4
changing the distance of the substrate and the grating to receive a plurality of fringe pattern image for a phase value of the flat surface; and calculating the phase value to out-of-plane displacement
Data Source
AI summary
The present invention is directed to a system and method for on-line real-time measuring the surface topography and out-of-plane deformation by using phase-shifting shadow moiré method. Digital Phase-Shifting Shadow Moiré Method is applied to a system, which receives the reflected images from the surface of transparent or non-transparent plate projected under a light beam passing through a grating. Next, by image correction program, the skewed interference fringe pattern is recovered to the image as if the image acquisition equipment is placed normal to the surface. Furthermore, the received images are processed with Phase-Shifting to show the surface topography of the plate.