Abstract
On-line non-contact surface inspection with high precision is still an open problem. Laser triangulation techniques are the most common solution for this kind of systems, but there exist fundamental limitations to their applicability when high precisions, long standoffs or large apertures are needed, and when there are difficult operating conditions. Other methods are, in general, not applicable in hostile environments or inadequate for on-line measurement. In this paper we review the latest research in Conoscopic Holography, an interferometric technique that has been applied successfully in this kind of applications, ranging from submicrometric roughness measurements, to long standoff sensors for surface defect detection in steel at high temperatures.
Highlights
Modern manufacturing requires on-line inspection methods to stay competitive
It is possible to project a thin laser line instead of a single point onto the inspected object and, by means of an adequate optic system including a cylindrical lens, each point resulting of the intersection from the laser plane with the object generates a one dimensional signal related to its distance, which is recorded by a conventional CCD camera
A moving target system enables the different speckle patterns to be integrated in each acquisition, reducing the global speckle noise; this reduction technique is naturally used in many industrial inspection applications and improves depth resolution over a 50%, and it is what was used in all the above examples
Summary
Modern manufacturing requires on-line inspection methods to stay competitive. Metrology systems able to detect surface defects, measure dimensions and, in general, acquire data about the geometrical shape of objects in a 3-D space, are a must for quality control, industrial inspection or reverse engineering. To achieve better resolutions from large standoffs when only relative measurements are needed, the University of Oviedo in close collaboration with Optimet, worked in a modification in the setup which consists in introducing triangulation between the laser source and the detection branch, so variations in the distance do provide (very small) fringe frequency variations and the whole interference pattern is shifted.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
