Description of the defocus effects of an acoustic reflection scanning microscope (SAM)

The effects connected with the defocus of the SAM are shown. With a radial grating test pattern we demonstrate three defocus effects, which cause an increasing blurring to the image structures. It contains the distribution of acoustic impedance and it is modified by the influence of the phase contrast, which becomes recognizable by spurious structures. If the aperture of the lens encloses the Rayleigh-angle, the described influence is overlayed by the material depending V(z)-contrast