On-Machine Optical Probe Based on Discrete Rotational Symmetric Triangulation

Xu Zhang,Quan Zhang,Kai Fei,Jianxiang Wang

doi:10.1155/2018/5801034

Abstract

In the field of modern manufacturing, probes have been playing a more and more crucial role. However, contact probes are unfit for measuring objects with soft surfaces or very tiny cavities and require radius compensation of stylus. In comparison, noncontact probes such as optical probes do not have to consider these problems and are well-performed in measurement. However, existing optical probes (triangulation) may fail to detect objects with rich spatial structures (due to the occlusion effect) and highly reflective curved surfaces (due to existence of highlight spots). Considering the problems, an optical probe based on discrete rotational symmetric triangulation is proposed in this paper. The emitting laser beam of the probe is the rotational axis and the five receiving optical paths (lenses and mirrors) are rotationally symmetrically distributed around the laser axis and are coimaged on a CMOS camera. Results of simulations and experiments show that the new-established prototype is designed with good robustness under various conditions such as different surface characteristics and different inclination degrees. The probe enables conducting real-time on-machine measurement without directional dependency with a resolution of 39 μm and repeatability accuracy of 0.72 μm.

Highlights

With the rapid development of modern manufacturing, complex parts have been more and more widely adopted in ship, automobile, aerospace, and other fields
To overcome the direction-dependent problem of laser triangulation measurement, the traditional method is to increase the degree of freedom (DOF) of the manipulator loaded by the measuring device, but additional mechanical design and cost are required
An optical probe based on discrete rotational symmetric triangulation method is proposed

Summary

Introduction

With the rapid development of modern manufacturing, complex parts have been more and more widely adopted in ship, automobile, aerospace, and other fields. To overcome the direction-dependent problem of laser triangulation measurement, the traditional method is to increase the degree of freedom (DOF) of the manipulator loaded by the measuring device, but additional mechanical design and cost are required. Another way is to change the equipment structure from the standpoint of the flexibility of the measuring device. The system can effectively solve the direction-dependent problem existing in traditional triangulation because the optical probe with discrete rotational symmetric characteristics can detect at least one light spot in all circumstances.

Discrete Rotational Symmetric Triangulation

Simulation

Experiment

Findings

Conclusion