Abstract
The photo-induced effects generated upon laser cleaning result to the removal of unwanted material, still transient deformation and damage on the surface and the structure of the materials can be also occurred. It is herein presented a laser-based workstation to monitor deformation and to evaluate any damage potentially induced by laser cleaning processes in a non-destructive and on-line methodology. An all-optics laser geometry, which allows the alignment of the ablation beam and the monitoring system, is enabled. On-line surface monitoring of photomechanical effects is performed through the acquisition of surface condition and its relevant displacement associated to the synchronously performed laser cleaning procedure. Surface condition is traced by interference generated patterns expressed in spatial coordinates and their alterations throughout the cleaning process. Transient deformation, damage, successful or successful intervention is deduced upon comparison of the last to the initial-reference position of the surface points. The all-optics laser-workstation aims to respond to the increasing demand of controlled interventions satisfying safety regulations and preventive measures to be taken on time. As a proof of application principle infrared (IR) laser-cleaning in the removal of varnish from wooden objects monitored with the synchronized coherent interferometry system, is presented.
Highlights
Introduction surfaceDespite any thorough post-evaluation protocol, the results are not always clarifying up the optimum operation conditions, given that preliminary tests are only indicative of the actual situation
Examination of photomechanical alterations was performed on polymer technical samples by means of optical holographic interferometry (HI) and Digital Holographic Speckle Pattern Interferometry (DHSPI), which allowed real-time visualization of the treated surfaces with resolving powers ranging from 100-3000 lines/ mm depended upon optics-geometry setting [9, 15,16,17,18]
In experimental conditions (i), (iii) and (iv) IR heating has been used as the excitation method in order to achieve the recording of the deformed state of the object whereas in experimental condition (ii) the laser irradiation from the laser cleaning device acts as the excitation method
Summary
The laser cleaning involves material removal with subsequent chemical and mechanical effects to the underlying or the surrounding areas. The photomechanical effects of the shock-waves propagation generated upon laser ablation may potentially provoke structural modifications to the surface, interfaces and to the bulk of the object. These potential effects cannot be detected by spectroscopy monitoring. The photomechanical effects differ from the dominant laser ablation effects and require different investigation approach These are studied simultaneously to the full extent of the surface of the irradiated sample and in temporal monitoring intervals. Photomechanical effects due to generation of structural flaws in solid materials are developed both in short and long-term and are monitored periodically opposed to photochemical and photothermal that are studied instantly [10 - 14]
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