The process of contrast formation for spherical particles in reflectio
n scanning acoustic microscopes is investigated. It is shown that in r
eflection acoustic microscopes the image formation of spherical partic
les is quantitatively well described by the Fourier optics methods. Th
e center image of a sphere shows the Fourier transformation of the squ
ared pupil function. The images in the top are similar to the OTF of t
he confocal microscopical system. The contrast of the image obtained i
n a middle position exhibits the pupil function in square.