Attempt to evaluate pressure waveform of diagnostic ultrasound using focused shadowgraphy with incoherent light source

Abstract

We have proposed a simple optical technique for visualization of ultrasound fields using the focused shadowgraphy. To improve the quality of the field images, effects of coherency in the illuminating light source were investigated using a laser diode (LD) and a light-emitting diode (LED). An acoustic field of a 2.5-MHz ultrasound pulse was visualized. The results showed that the effect of noise in the LD beam, which was generated by interference of light diffraction, was not removed by the image subtraction, while the effect of noise in LED beam containing no interference noise was successfully removed. Also, the first order integration of the brightness waveform evaluated using the LED field image showed good agreement with the pressure waveform only in the case with the pinhole, indicating the possibility for evaluation of pressure waveform from an optical image of an ultrasound fields.