Design of a new laser thickness measurement instrument

In order to measure the thickness of the hot-rolled steel plate on line, an automatic laser gauging system was established, and its mechanical design and optical design, image algorithm based on MATLAB were investigated. Firstly,the laser beam was inclined to project onto the side of the plate,and a baffle is setted to block the part of light at horizon.Secondly, the laser spot on the tested plate is imaged to CCD target surface in an industrial video camera.Then the defocusing amount is calulated based on the the CCD images.Finally,according to the geometric relationship between actual thickness of the plate to be measured and the imaging height of the plate flank in the CCD and the defocusingamount, the thickness of the steel plate is calculated. Experimental results indicate that the precision of the system is 0.32mm, smaller than the measurement system requirements 0.5mm when the plate thickness between 8mm and 120mm. This measuring system has less influence induced by high temperature radiation.It can satisfy the system requirements of stabilization,higher precision and rapidity,as well as little interference.