Study on CCD laser scanning flatness measurement method for hot rolled strip

Abstract

To provide a flexible calibration method and make an accurate machine vision (MV) based flatness measurement strategy a reality in routine production line, an area scan charge coupled device (CCD) laser stripe scanning approach is presented. The applicability of the proposed method is not tied to the strip exclusively. First, we devise an automatic laser stripe imaging quality evaluation method through analysing the characteristics of the image grey gradient of laser stripe, which is a prerequisite for precisely extracting the laser stripe modulated information in hot or reflective object surface; second, a fast system calibration method is designed based on the area scan CCD imaging principle and spatial measurement technologies; here, the practical calibration is an indispensable technique for MV based measurement with large field of view in modern steelmaking lines. The proposed method performs competitively with the state-of-the-art as seen from the comparison of the experimental results. Through online testing, this method also showed considerable promise for hot rolled strip flatness measurement. However, the scheme for eliminating the influence of vibrations related to different applications is not taken into account in the current work.

Keywords:

• Hot rolled strip
• CCD
• Flatness measurement
• System calibration
• Laser scanning