Transfer function analysis of a quasioptical ultrasonic imaging system.
The imaging properties of lenses have been well analyzed in the optical regime. However, most of these analyses have been confined to two cases: illumination of the object with ideal coherent or ideal incoherent light. In ultrasonics, imaging systems with lenses also are known. But in contrast to the optical case, the object can be easily insonified with waves of variable frequency or with a noise source of adjustable bandwidth. In this paper, the influence of the broad frequency bandwidth in an ultrasonic imaging system is emphasized. A so called "imaging channel transfer function" (ICTF) is introduced to describe all nonelectrical system properties. It is shown that the ICTF is part of a temporal frequency transfer function. This transfer function has a frequency dependence which is not readily attainable with well-known active or passive RLC-networks. Finally, it is demonstrated how to use the ICTF for calculating the image response in a wideband imaging system with ultrasonic sources emitting either deterministic or stochastic signals of a certain bandwidth.
D000162:Acoustics; D006801:Humans; D007909:Lenses; D008433:Mathematics; D055095:Optics and Photonics; D014463:Ultrasonography / Q000379:methods*