Film Thickness Gauge Based On Dual-light Path Infrared Imaging

Thickness is an important parameter of film, in a large-scale film production, smallthickness change will lead to a huge material difference. Accurate online film thicknessmonitoring has been an indispensable part of the film production line. Infrared thicknessmeasurement is a common used online film thickness measurement method, but traditionalinfrared thickness measurement still have many defects. Some open-loop infrared thicknessmeasurement system is sensitive to the stability of light source, some is not applicable tohigh-speed film production line. In order to solve these problems, a dual-light path infraredimaging thickness measurement system was presented. Using dual-light path referencemeasurement method can effectively avoid the impact of the unstable of light source, and asthe exposure time of the camera is very short, system is applicable to high-speed filmproduction line. The following work has been completed:Several commonly used infrared online thickness methods were introduced, theadvantages and disadvantages of each method were analyzed. Internal and overseas researchactuality was summarized, the shortcomings of current Infrared thickness measurement wasanalyzed, then, a dual-light path imaging measurement was proposed.The basic principle of infrared thickness measurement was studied. The light pathstructure and the mechanical structure was designed. The imaging principle was describedand the expression of the intensity ratio was derived.Developed the measurement software by Visual Studio in Windows platform, anefficient image processing algorithm was proposed by extracting the light spot once butusing it repeatedly.Analyzed the relationship between the resolution of the instrument and three factors:the thickness of the film, the absorption coefficient of the film and the light source intensity.Several experiments were designed to test the instrument and the results showed that change of light source intensity, change of camera exposure time and small internal stress all havelittle effect on the measurement.Calibration experiments for PE and PTFE film were conducted, the results show thatthe system has a micron accuracy.