The proposed nondestructive method is mainly developed for the needs of semiconductor technology and is intended for visual inspection of interfacial bubble- and gap-like defects in multi-wafer bonded structures including SOI. It implies the use of a narrow spectral range (Delta lambda) IR imaging camera with Delta lambda/lambda(c) similar to 0.1, where lambda(c) is the operating wavelength. The method does not need a monochromatic radiation source. Computer-equipped IR thermography system with InAs-based focal plane array is employed in the work. The possibility to detect the concealed defects in the transmitted and reflected beams as well as to observe their evolution during annealing is demonstrated. In particular, the method is applied for monitoring samples containing heavily doped wafers, nontransparent to IR radiation.