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Proceedings Paper

Noncontact photoacoustic spectroscopy (NCPAS) during photoablation: a step toward the smart laser?
Author(s): Thomas Bende; Michael Matallana; Bernhard Kleffner; Manfred Ostertag; Benedikt J. Jean
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Paper Abstract

Laser photoablation in the IR and UV is accompanied by an acoustic signal. NCPAS may be used for a non-contact monitoring of the ablation process. NCPAS was performed in combination with the 193 nm Excimer-, 2.94 micrometers Er:YAG-, and the FEL laser (< 11 micrometers ). A microphone (Bjoer & Kjaer, 20 Hz- 200kHz) was used. Gelatine, as a target material substitute for cornea was ablated. During ablation, the dependency of NCPAS as a function of fluence, ablation diameter, and target hydration was determined. NCPAS was analyzed in the time-signal and Fourier transformation (FT). The Fourier spectrum of the NCPAS signal shows two gaussian-like curves. As a function of fluence NCPAS showed a linear increase of the time dependent amplitude and the amplitude of the frequency interval, in the observed fluence range. In the FT the beam diameter leads to a square increase of amplitude. Up to the physiological value the hydration shows an increase in amplitude of the FT. NCPAS allows the discrimination of different neighboring biological materials by a typical frequency shift in the FT. On-line detection of NCPAS can be used for feed back, leading to a `smart' laser control.

Paper Details

Date Published: 22 May 1995
PDF: 9 pages
Proc. SPIE 2393, Ophthalmic Technologies V, (22 May 1995); doi: 10.1117/12.209833
Show Author Affiliations
Thomas Bende, Univ. Tuebingen (Germany)
Michael Matallana, Univ. Tuebingen (Germany)
Bernhard Kleffner, Univ. Tuebingen (Germany)
Manfred Ostertag, Univ. Tuebingen (Germany)
Benedikt J. Jean, Univ. Tuebingen (Germany)


Published in SPIE Proceedings Vol. 2393:
Ophthalmic Technologies V
Jean-Marie Parel; Qiushi Ren; Karen Margaret Joos, Editor(s)

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