Thickness Measure Instrument By Laser Triangulation With Side Focal Line Illumination

The methods of thickness measurement include offline and online.Generally,in order to ensure efficiency,the factory will choose an online measurement system.The laser triangulation thickness measurement is not high on the surface of the measured object,and more importantly,its detection speed is faster and the precision is higher.Therefore,the thickness gauge based on the laser triangulation method is an excellent on-line measuring device which can meet the thickness measurement needs of most factories.There are many such measuring illumination on the market,but most of them are C-shaped and word-shaped structures.When these structural measuring instrument is placed on the production line,it may be damaged due to the workpiece edge warping,which will interfere with the normal operation of the production line.To solve this problem,a laser triangulation thickness measurement system based on side focus line method is proposed in this paper.The main work is as follows:1.Analyzed the principle of laser triangulation ranging,from direct laser triangulation ranging to oblique laser triangulation ranging.The principle of laser triangulation thickness measurement is also analyzed,from the double optical path laser triangulation thickness measurement to the single lens laser triangulation thickness measurement.In order to overcome their shortcomings,the new principle of this thesis—thickness measurement by Laser Triangulation with side focal line illumination is proposed.2.Design a complete measurement plan,not only to plan the design as a whole,but also to analyze and calculate the light source module and the imaging module separately.Among them,the design of light source module includes the design of focal length and depth of field;the design of imaging module includes the design and selection of aperture,plane glass,imaging lens group and image detector.The mechanical structure of the system was modeled using Solid Works and the optical system was designed and evaluated using Zemax.3.Image processing is carried out on the collected images.Firstly,the random errors caused by stray light are eliminated by smoothing filtering and the influence of background noise is eliminated by threshold segmentation.Then,the work of searching and locating the spot is carried out,which lays a foundation for the calculation of measuring thickness.Finally,the software interface is designed,including preview module,calibration module,measurement module and display module.4.Several calibration methods are compared and the most reasonable and accurate one is selected to establish the calibration equation for the measurement system.The calibrated measurement system is used to simulate the production line experiment,record the experimental data and verify its online measurement function.The main sources of errors are analyzed,which provides ideas for future improvement and perfection.The actual thickness gauge can be placed on the side of the production line to complete the measurement.It has a measuring range of 10 mm and a measurement accuracy of ±10?m.