Abstract
Laser triangulation (LT) is widely used in many fields due to its good stability, high resolution and fast speed. However, the accuracy in these applications suffers from severe constraints on the data acquisition accuracy of LT. To solve this problem, the optical triangulation principle, the object equation of the optical path relationship and the deviation of the laser spot centroid are applied to deduce a mathematical model. Therefore, the image sensor inclination errors can be quantitatively calculated, and the collected data are compensated in real time. Further, a threshold sub-pixel gray-gravity (GG) extraction algorithm is proposed; the gradient function and Gaussian fit algorithm are used to set thresholds to remove the impact of the spot edge noise area on the center location; and polynomial interpolation is employed to enhance the data density of the traditional GG method, thus improving the data acquisition accuracy of LT. Finally, the above methods are applied to on-machine measurement of the American Petroleum Institute (API) thread and the screw rotor, respectively. The experimental results prove that the proposed method can significantly improve the measurement accuracy of free-form curved surfaces using LT and that the improved laser spot center extraction algorithm is more suitable for free-form curved surfaces with smaller curvature and more uniform curvature changes.
Highlights
In recent years, non-contact optical instruments based on laser triangulation (LT) have been increasingly used in size measurement in the fields of automobiles [1,2], automation [3,4,5], machine tools [6,7], papermaking [8] and construction [9,10], due to their low-cost, high-efficiency and non-invasive features
TheHowever, contour parameters parameters are measured the monomial parameters gauge (MPG)current in every oil field are measured by using by theusing monomial parameters gauge (MPG)
To increase the data acquisition accuracy of LT, this paper starts with the LT principle, delves into the LT geometrical optical path system, analyzes the cause for generating image sensor inclination errors and deduces a mathematical model that can quantitatively calculate the error compensation amount based on the deviation of the spot centroid
Summary
Non-contact optical instruments based on laser triangulation (LT) have been increasingly used in size measurement in the fields of automobiles [1,2], automation [3,4,5], machine tools [6,7], papermaking [8] and construction [9,10], due to their low-cost, high-efficiency and non-invasive features. Many factors can interfere with the data acquisition accuracy of LT, which can be generally divided into three categories: the inherent characteristics of LT, the measurement environment and the surface properties and geometries of the measured object. The impact of the inherent characteristics of LT on its data acquisition accuracy can be further divided into two factors: the nonlinearity of the triangulation model and the fluctuation of the laser beam. The problem that the nonlinearity of the triangulation model affects the measurement accuracy of LT is usually solved by using the calibration method. Sun et al [12] and Zhang et al [13], considering that the geometric parameter calibration process is tedious, established new data acquisition models respectively based on different methods and proved experimentally that the proposed calibration method is efficient. Yang et al analyzed the Sensors 2018, 18, 3527; doi:10.3390/s18103527 www.mdpi.com/journal/sensors
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call