1. A method for determining a sound pressure distribution in a solid body, comprising: launching into the solid body an ultrasonic pulse waveform; directing light from a stroboscopic light source into the solid body during a time when the pulse waveform is propagating in the solid body, through a linear polarization device having a principal axis which is aligned at a first predetermined angle; generating a first image of the light passing through the body with the principal axis at the first predetermined angle; generating a second image of the light passing through the solid body with the principal axis offset at about 45.degree. from the predetermined first angle; and combining the first and second images to produce a synthesized image.