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Proceedings Paper

Noncontact photoacoustic spectroscopy (NCPAS) for photoablation control: data acquisition and analysis using cluster analysis
Author(s): Holger Specht; Thomas Bende; Benedikt J. Jean; Wolfgang Fruehauf
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Paper Abstract

Laser photoablation using UV or IR lasers is known to trigger a photo acoustic event. Different target materials can be discriminated by analyzing the photoacoustic signal. In vitro measurements of NCPAS have revealed the necessity to integrate a number of variable elements (tissue hydration, fluence, laser beam diameter, distance to microphone, etc.). This study defines the parameters needed for the initiation of a self learning system for target material recognition. A UV excimer laser (λ=193 nm; Summit Technology, UV 200L) was used to ablate organic polymers (PMMA, PA, PVC), normal and porcine corneal scar tissue, and human cornea in vivo. NCPAS was performed using a microphone (up to 200 kHz) as a detector. During photoablation, the acoustic signal was analyzed by a multiport A/D IBM PC based digital oscilloscope. The data obtained were imported into a Matlab language program and analyzed. NCPAS allows the discrimination of different materials by a characteristically frequency shift of the photoacoustic signal. Detection and online material recognition using NCPAS is a step on the way to a `smart' laser control, based on an artificial neuronal network.

Paper Details

Date Published: 18 June 1999
PDF: 6 pages
Proc. SPIE 3591, Ophthalmic Technologies IX, (18 June 1999); doi: 10.1117/12.350581
Show Author Affiliations
Holger Specht, Univ. Eye Hospital Tuebingen (Germany)
Thomas Bende, Univ. Eye Hospital Tuebingen (Germany)
Benedikt J. Jean, Univ. Eye Hospital Tuebingen (Germany)
Wolfgang Fruehauf, Technical Univ. Reutlingen (Germany)

Published in SPIE Proceedings Vol. 3591:
Ophthalmic Technologies IX
Bruce E. Stuck; Pascal O. Rol; Michael Belkin; Karen Margaret Joos; Fabrice Manns; Bruce E. Stuck; Michael Belkin, Editor(s)

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