The theory of dark field imaging technique as applied to acousto‐optic interactions has been developed and then used in studies of linear and nonlinear surface acoustic waves and volume acoustic waves. The theory is consistently expressed in terms of phase transmittance function. Experimental results show how the technique can be applied in the case of multimode propagation to unfold the complex frequency spectra of spurious modes in surface wave devices, and how to discriminate between different harmonics in the case of nonlinear acoustic propagation.