Laser ultrasonic tomography uses pulsed laser light for photoacoustic excitation of short probe ultrasonic pulses in a special light-absorbing plate. These pulses propagate through the immersion liquid, then they are reflected from the surface of the object and scattered by the inhomogeneities inside the object. Scattered and reflected waves are recorded by a broadband multi-element piezoelectric array and used to reconstruct the image. The wide spectral band (0.1-15 MHz) of probe pulses is well suited to the problem of inspection of carbon-fiber-reinforced polymers (CFRPs), allowing visualization of individual carbon fiber layers and defects with high accuracy. In this paper, laser ultrasonic tomography is proposed for inspection of CFRPs. The experimental results of the inspection of a graphite-epoxy composite sample with inclusions and defects are presented.
We report on a new experimental technique aimed to investigate femtosecond filamentation process in transparent condensed dielectrics. The proposed method is based on a highly resolved shadow photography and wideband (about 100MHz) photoacoustic imaging. We demonstrate, that combination of these techniques allows conducting comprehensive filament investigation by retrieving the value of the energy deposition into a medium, plasma electron density and the size of the filament formation region. Moreover, applying these techniques we studied the dependence of filament properties on a filamentation regime.
This article addresses theoretical and numerical investigation of image formation in photoacoustic (PA) imaging with complex-shaped concave sensor arrays. The spatial resolution and the size of sensitivity region of PA and laser ultrasonic (LU) imaging systems are assessed using sensitivity maps and spatial resolution maps in the image plane. This paper also discusses the relationship between the size of high-sensitivity regions and the spatial resolution of real-time imaging systems utilizing toroidal arrays. It is shown that the use of arrays with toroidal geometry significantly improves the diagnostic capabilities of PA and LU imaging to investigate biological objects, rocks, and composite materials.