Research On Portable Single Lens Laser Triangulation Thickness Gauge

Along with the developing of the material manufacturing technique and the improving ofthe measuring and metering technique level, the measuring accuracy of the instrument wasrequested to be higher, and the detecting pattern has changed from off-line metering to on-linegauging gradually. The cold-rolled steel has a comprehensive application in the areas ofvehicle manufacturing, mechanical processing, shipbuilding, civil construction, light industryand so on as an important raw material, and the hot-dip galvanization process was applied inthe area of rust protection of steel plate. It has been reported that about half of the productionof the zinc of the world were consumed in anticorrosion of the steel plate annually. Hence, thehigh precisely measuring of the galvanized sheet influenced the optimizing of the process ofthe galvanizing and rational distribution of the zinc significantly. In order to solve theproblem of high accuracy on-line thickness measurement of the galvanized sheets, a methodcalled single lens laser triangulation was proposed. Comparing with the traditional dual-lasertriangulation thickness measurement method, the two imaging detectors in the upper andlower optical paths became one through optimizing the optical path designing, thus it avoidedthe difficulty to synchronize two imaging detectors and made the measuring result unaffectedby the dithering of the measurand. In this paper, the following works have been done for thedesigning of the thickness gauging device:1. Summarized the existing thin plate thickness measurement methods, and discussed thecharacteristics, the accuracy and the main error influencing factors of the different measuringmodels respectively. Proposed a single lens laser triangulation method based on the aheadwork and analyzed the thickness measuring principle and the mathematical model.2. Confirmed a reasonable mechanical structure program and an optimal optical systemstructure program which guaranteed that the laser thickness gauge has a small geometricaldimension, light weight and portable measurement ability. Evaluated the optical system withthe ZEMAX software and introduced the selection of the assembly parts.3. Finished the image processing and the software programming work with the VisualC++tools based on the windows platform.4. Conducted the calibrating experiment and finished the data processing with Matlabsoftware.5. Proposed a nonlinear correction method and conducted the contrast experiment for therectification of the nonlinear relationship between the measuring thickness and the twoimaging spots spacing during the calibrating experiment.The actually developed thickness gauge has a geometrical dimension of380mm×202mm ×98mm with a weight less than7.5kilograms, which achieved the portable measurementdemand for its small apparent size and light weight comparing to the similar traditionalthickness gauge. After a period of time on-line working on the dip galvanizing line, themeasuring accuracy of the thickness gauge was proven to be influenced rather slightly by theenvironmental temperature and vibration, which satisfied the measuring requirement of theindustrial scene well, and it is high likely to be expanded to the thickness measurement ofother similar sheets such as thin plate, section bar and thin films.