This book presents a systematic approach to imaging of acoustic reflection measurements and the extraction of media property information from the image amplitudes, based on wave theory.Although the approach is valid for a wide range of acoustical frequencies and applications, there is a bias towards seismic imaging, because imaging the earth is one of the most challenging of all acoustical imaging applications. In addition, in oil and gas exploration and production applications the need to obtain quantitative information on the media properties of the object to be imaged is most strongly felt. However, the methods presented are equally valid for ultra-sonic non-destructive testing, or medical diagnostic applications.The theory of acoustic wave propagation is presented, from the constituent equations Hooke and Newton, to the acoustic wave equation, to wavefield extrapolation and to extraction of image amplitudes. A feature of this book is the careful analysis of every step in these processes in terms of the linearity of the wavefields in the media property representation they are inverted for. Alternatively, the extrapolated wavefields can be inverted directly for the media properties. Towards the end of the book it is demonstrated that significantly higher resolution quantitative information can be obtained if the non-linearity is taken into account.