A Study on the Uncertainty of a Laser Triangulator Considering System Covariances

Pablo Puerto,Alberto Mendikute,Beñat Estala

doi:10.3390/s20061630

Abstract

A laser triangulation system, which is composed of a camera and a laser, calculates distances between objects intersected by the laser plane. Even though there are commercial triangulation systems, developing a new system allows the design to be adapted to the needs, in addition to allowing dimensions or processing times to be optimized; however the disadvantage is that the real accuracy is not known. The aim of the research is to identify and discuss the relevance of the most significant error sources in laser triangulator systems, predicting their error contribution to the final joint measurement accuracy. Two main phases are considered in this study, namely the calibration and measurement processes. The main error sources are identified and characterized throughout both phases, and a synthetic error propagation methodology is proposed to study the measurement accuracy. As a novelty in uncertainty analysis, the present approach encompasses the covariances of correlated system variables, characterizing both phases for a laser triangulator. An experimental methodology is adopted to evaluate the measurement accuracy in a laser triangulator, comparing it with the values obtained with the synthetic error propagation methodology. The relevance of each error source is discussed, as well as the accuracy of the error propagation. A linearity value of 40 µm and maximum error of 0.6 mm are observed for a 100 mm measuring range, with the camera calibration phase being the main error contributor.

Highlights

To guarantee accurate measurement using a triangulation system, previous calibration procedures must be performed in order to know the relative position between both elements
40 μm and maximum error of 0.6 mm are observed for a 100 mm measuring range, with the camera calibration phase being the main error contributor
In doing so we identify plane’s are the normal vector of the laser plane information

Summary

Introduction

To guarantee accurate measurement using a triangulation system, previous calibration procedures must be performed in order to know the relative position between both elements. These measurement systems are known as laser displacement sensors (LDS), structured-light sensors, or sheets of light. The calibration process is carried out with a reference object with previously known dimensions. This object can either be 2D or 3D [1]. More than the position of the object is needed unless the 3D object is accurate enough to define the laser plane

Methods

Discussion

Conclusion