It is demonstrated that Photo-acoustic Induced by Laser Ablation (PILA) technique is suitable for the real time control and monitoring of the de-thorning process of nopal vegetable using pulsed laser. Two methods for detection of thorns are proposed; the first one uses the photo-acoustic amplitude and the second one is based in the harmonic composition of photo-acoustic signals. The latter detects clearly, thorns positions, differentiating them from other features that could exist in the nopal cortex. Harmonic composition of photo-acoustic signals also allows defining when thorns have been removed. Finally, it is obtained a characteristic pulse duration that, for the used energy range, maximizes thorns removal.Keywords: pulsed photo-acoustic, laser cleaning, laser ablation, photo-acoustic monitoring, laser-matter interaction.
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