Surface Crack Detection with Low-cost Photoacoustic Imaging System

Abstract

Photoacoustic measurement in an imaging system is a unique method as it uses optical disturbance but observes its effect acoustically. Acoustical observation increases the quality of a measurement by reducing the scattering effect that often occurs in optical research. However, a few problems, such as cost and complexity, hinder development of a photoacoustic system. This report presents a design of a photoacoustic system using a laser diode and a commercial microphone as the acoustic emission source and sensor, respectively. Analysis of the photoacoustic signal received by the microphone was performed with software-based Fourier transformation, which makes the photoacoustic system simpler and lower in cost. By measuring the amplitude of the signal, the system accurately detects surface micrometer cracks. The report shows that the system is capable of producing a photoacoustic image of an object with microcracks on its surface. The results indicate that the photoacoustic imaging system developed in the experiment is a more promising way to generate images of cracks than optical imaging.

Resonance frequency measurement to identify stiffness variations based on photoacoustic imaging

“…Variations in measurements may be caused by nonuniform light fluence on the surface [ 31 ], and surface roughness of the sample [ 32 ]. The boundary line of the phantom intersection experiences repetitive reflection toward a very thin slit, which results in an increase in absorption as a result of repeated laser-material interactions [ 33 ] and shows up as an increase in the gray value of the pixel plot profile (Fig 7(c), and 7(d)). However, the photoacoustic technique still presents the difference in mechanical resonance for the different phantom stiffnesses tested.…”

Subsurface detection of opaque and solid material defect based on photoacoustic effect

“…Compared with the conventional laser (e.g. OPO Nd: YAG or TEA-CO 2 ), laser diode is more portable and low cost [13,14]. On the acoustic sensor part, a standard audio microphone without any customization is used.…”

Sistem Pendingin Termoakustik Dengan Menggunakan Stack Acak dan Penukar Kalor Tambahan Dalam Resonator

“…Selain parameter di atas, pada dasarnya terdapat banyak parameter yang menentukan kinerja dan efisiensi pendingin termoakustik, antara lain: jenis dan tekanan gas, bahan stack, kinerja loudspeaker, konfigurasi resonator, dan lain-lain [5,6,7,8,9,10].…”