Research On Laser Triangulation Rangefinder With Linear Facula

Laser triangulation technology has become one of the most widely used optical measurement technologies because of its many remarkable advantages.In order to meet the higher and higher accuracy requirements of laser triangulation in scientific research and industrial production,it is necessary to study the factors that limit the accuracy of laser triangulation.Therefore,in order to suppress the laser speckle noise in laser triangulation,the method of laser triangulation with linear facula and the method of laser triangulation with wavefront-splitting image shifting are proposed in this paper.The main research contents are as follows:(1)The basic principle of laser triangulation rangefinder is introduced,and the relationship between measurement uncertainty and location uncertainty of imaging spot is deduced;The basic principle of generating laser speckle noise is explained,and the expression of measurement uncertainty in laser triangulation ranging is deduced;A method of suppressing laser speckle noise by laser triangulation with linear facula is proposed;The location uncertainty of imaging spot is simulated and experimented.The influence of laser speckle noise on the location uncertainty of imaging spot,The suppression of laser speckle noise by linear facula and the influence of system parameters on laser speckle noise are verified.(2)The design of laser triangulation rangefinder with linear facula is presented,including optical system,system structure and software algorithm.The design of the optical system includes the depth and length of the linear facula,the selection of the imaging lens and the image sensor,and the overall design of the optical system;In the part of system structure design,in order to meet different needs,three sets of system structures are designed;In the part of software algorithm design,a gray centroid algorithm based on image spot shape is proposed,which improves the effect of suppressing speckle noise by linear focus illumination.(3)The related performance experiments of the developed laser triangulation rangefinder with linear facula are carried out,including system calibration,range scanning and measured surface effect.The polynomial fitting method is used in the system calibration experiment,and good results are obtained;The range scanning experiment proves that the measurement uncertainty of the system meets the design requirements.The experiment of measured surface effect proves that the measurement uncertainty is not only affected by the roughness but also by the non-uniformity of the optic response characteristics of the measured surface.(4)In order to further suppress laser speckle noise without sacrificing larger lateral resolution,a new method of wavefront-splitting image-shifting laser triangulation ranging is proposed in this paper.The principle of speckle noise suppression by wavefrontsplitting image shifting is introduced,and the influence of the statistical properties of each imaging spot on the suppression effect of laser speckle noise is discussed;The method of realizing wavefront-splitting image shifting in this paper is given.And according to the statistical properties of the imaging spot,a method of calculating the location coordinates of the imaging spot by normalized averaging in the wavefront-splitting image shifting is proposed,which further reduces the location uncertainty of the imaging spot;Finally,the effects of various methods to suppress laser speckle noise are compared through experiments.The experimental results show that the suppression effect of speckle noise of wavefront-splitting image shifting is better than that of single-line facula,and the suppression effect of speckle noise of single-line facula is better than that of single-point facula.