In this study, the visualization and measurement of shock wave phenomena were conducted using the Background Oriented Schlieren (BOS) method. Initially, an LED nano-flash lamp was adopted as the illumination source. However, two major challenges arose: insufficient light intensity for accurate measurement and the large physical size of the lamp, which interfered with background imaging. To overcome these limitations and achieve miniaturization, we adopted a semiconductor laser as the new light source. While the semiconductor laser offered advantages in compactness and high intensity, achieving effective visualization of unsteady compressible flow required short pulse duration and sufficient light output. In this study, we evaluated two semiconductor lasers with different power ratings 5 W and 50 W to investigate the effect of output power on visualization performance. The experimental results showed that the 5 W laser provided insufficient contrast for BOS imaging, whereas the 50 W pulse laser (CAVILUX) enabled clear background images with a short light emission time. These findings suggest that higher laser output is critical for accurate BOS measurements of unsteady compressible flows.
SHIMIZU et al. (Wed,) studied this question.