A method for optically testing semiconductor devices or wafers using a holographic optical interference system with a light source providing a light beam of coherent wavelength with a wavelength to which the semiconductor material is transparent, splitting the light beam into a reference beam and an object beam, imposing the object beam on the semiconductor material to generate a reflected object beam reflected from interior structures of the semiconductor material, adjusting the angle of the reference beam relative to the object beam between a plurality of angles with the semiconductor material being in a different state for each angle of the reference beam, imposing the reflected object beam and the reference beam onto a detection device to create a plurality of interference patterns, one for each of the reference beam angles, and comparing the interference patterns to one another to determine characteristics within the semiconductor material.