Scanning mid-IR-laser microscopy was previously demonstrated as an effective tool for the characterization of different semiconductor crystals. Now the technique has been successfully applied for the investigation of CZ SixGe1-x - a promising material for photovoltaics - and multicrystalline silicon for solar cells. In addition, this technique was shown to be appropriate for the imaging of polishing-induced defects as well as huge defects such as 'pin holes'. Besides, previously unexplained 'anomalous' (cubic power) dependence of signal of the scanning mid-IR-laser microscope in the optical-beam-induced light scattering mode on the photoexcitation power obtained for mechanically polished samples has now been attributed to the excess carrier scattering on charged linear defects, likely dislocation lines. The conclusion is made in the article that scanning mid-IR-laser microscopy may serve as a very effective tool for defect investigations in materials for modern photovoltaics.