Active thermography and post-processing image enhancement for recovering of abraded and paint-covered alphanumeric identification marks

R. Montanini, A. Quattrocchi, Sebastiano Piccolo

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Alphanumeric marking is a common technique employed in industrial applications for identification of products. However, the realised mark can undergo deterioration, either by extensive use or voluntary deletion (e.g. removal of identification numbers of weapons or vehicles). For recovery of the lost data many destructive or non-destructive techniques have been endeavoured so far, which however present several restrictions. In this paper, active infrared thermography has been exploited for the first time in order to assess its effectiveness in restoring paint covered and abraded labels made by means of different manufacturing processes (laser, dot peen, impact, cold press and scribe). Optical excitation of the target surface has been achieved using pulse (PT), lock-in (LT) and step heating (SHT) thermography. Raw infrared images were analysed with a dedicated image processing software originally developed in Matlab™, exploiting several methods, which include thermographic signal reconstruction (TSR), guided filtering (GF), block guided filtering (BGF) and logarithmic transformation (LN). Proper image processing of the raw infrared images resulted in superior contrast and enhanced readability. In particular, for deeply abraded marks, good outcomes have been obtained by application of logarithmic transformation to raw PT images and block guided filtering to raw phase LT images. With PT and LT it was relatively easy to recover labels covered by paint, with the latter one providing better thermal contrast for all the examined targets. Step heating thermography never led to adequate label identification instead.
    Original languageEnglish
    JournalInfrared Physics & Technology
    Volume78
    Pages (from-to)24-30
    ISSN1350-4495
    Publication statusPublished - 2016

    Keywords

    • Atomic and Molecular Physics, and Optics
    • Condensed Matter Physics
    • Electronic, Optical and Magnetic Materials
    • Forensic investigation
    • Identification labels
    • Lock-in thermography
    • Pulse thermography
    • Serial numbers
    • Step heating thermography
    • Crashworthiness
    • Infrared imaging
    • Locks (fasteners)
    • MATLAB
    • Nondestructive examination
    • Optical data processing
    • Paint
    • Recovery
    • Thermography (imaging)
    • Active infrared thermography
    • Identification of products
    • Lockin thermography
    • Logarithmic transformations
    • Serial number
    • Thermographic signal reconstruction
    • Image processing

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