Abstract: Variations in a translucent medium are imaged by detecting deflections and/or polarization shifts in a probe beam transmitted through the translucent medium. Deflections and polarization shifts may be detected using a first polarizing filter positioned between a probe beam generator and the translucent medium to polarize the probe beam in a first direction, a beam splitter positioned to receive the probe beam after it has been transmitted through the medium, and a probe beam deflection detector that receives a first split beam and provides a deflection signal associated with refractive index variations in the medium. A second polarizing filter receives a second split beam and polarizes it in a second direction, perpendicular to the first direction. An intensity sensor receives the second split beam, after it has passed through the second polarizing filter, and provides an intensity signal associated with a polarization shift in the medium.