Staggered Optical Pattern for Steel Sheet Flatness Measurement
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Solution Overview
Problem
Existing methods for measuring the flatness of hot-rolled steel sheets struggle with high accuracy due to strong specular reflection properties, leading to image saturation and reduced measurement resolution, especially when the image pickup device is positioned to receive specularly reflected light.
Innovation Solution
A method using a staggered pattern with light and dark portions arranged in a staggered form at predetermined pitches in the longitudinal and transverse directions, allowing the image pickup device to capture the pattern while avoiding image saturation, and calculating the surface shape by averaging picture element concentrations along specific lines to maintain measurement resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the image pickup device is positioned to receive specularly reflected light from the steel sheet surface, then the measurement can be performed in a compact setup, but the strong specular reflection causes image saturation and pattern collapse leading to loss of measurement precision
Solution Approach 1:
The patent applies asymmetry by using a staggered pattern where light and dark portions are offset from each other in the longitudinal direction, creating an asymmetric arrangement that prevents symmetric collapse of the pattern due to specular reflection. This asymmetric staggered configuration ensures that the pattern maintains its distinguishability even when subjected to strong specular reflection from the steel sheet surface.
Solution Approach 2:
The patent transitions from a conventional linear pattern to a two-dimensional staggered pattern arranged in both longitudinal and transverse directions. By adding the transverse dimension with staggered positioning, the pattern creates multiple reference points that prevent complete collapse even when specular reflection affects certain areas, thereby maintaining measurement precision.
2Device complexity
If a conventional linear pattern is used for flatness measurement, then the setup is simple, but the pattern collapses under strong specular reflection causing loss of measurement resolution
Solution Approach 1:
The patent segments the conventional linear pattern into multiple staggered light and dark portions arranged in a two-dimensional configuration. This segmentation creates distributed pattern elements that are less susceptible to complete collapse from specular reflection, maintaining measurement resolution while keeping the overall system relatively simple.
Solution Approach 2:
The patent introduces a curved or staggered arrangement of the pattern elements rather than a straight linear configuration. This curved/staggered geometry helps the pattern maintain its integrity under specular reflection conditions, preventing the linear pattern collapse that would otherwise occur.
3Productivity
If the light and dark pattern is projected onto the steel sheet surface with strong specular reflection, then the measurement can be performed, but the picture element concentration saturates leading to inaccurate surface shape calculation
Solution Approach 1:
The staggered pattern arrangement acts as an intermediary structure that mediates between the projected light and the image pickup device. By staggering the light and dark portions, the pattern distributes the reflected light intensity more evenly, preventing saturation of picture element concentrations while maintaining the ability to perform measurements.
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
Enables high-accuracy flatness measurement of hot-rolled steel sheets even with strong specular reflection, preventing pattern collapse and maintaining measurement resolution, thus improving the precision of flatness control in steel sheet production.
Implementation Method 1
the image pickup device is positioned to receive specularly reflected light
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
An objective of the present invention is to provide a method for measuring the flatness of a sheet material, in which even in the case where an image pickup device is arranged at a position at which the specularly reflected light of a light and dark pattern projected onto the surface of a sheet material having a strong specular reflection property can be received, the surface shape and the flatness of the sheet material can be measured with high accuracy. The method of the present invention uses a staggered pattern as the light and dark pattern projected onto the surface of the sheet material, the staggered pattern being composed of light portions arranged in a staggered form at a predetermined preset pitch in a longitudinal direction and a transverse direction. The method sets a shape measurement line extending along the longitudinal direction of the staggered pattern in the acquired pattern image by the image pickup device. The method averages picture element concentrations on a straight line which passes through a picture element on the shape measurement line and extends in the transverse direction of the staggered pattern, and has a length two times or more the transverse preset pitch between the light portions to calculate an average picture element concentration. The method calculates a surface shape of the sheet material based on the average picture element concentration distribution along the shape measurement line, and calculates the flatness of the sheet material based on the calculated surface shape.