## 4pSP11. Two-step holographic reconstruction of an acoustic field.

### Session: Thursday Afternoon, December 5

### Time: 4:50

**Author: Makoto Tabei**

**Location: Dept. of Intl. Development Eng., Tokyo Inst. of Technol. 2-12-1, O-okayama, Meguro-ku, Tokyo, 152 Japan**

**Author: Mitsuhiro Ueda**

**Location: Dept. of Intl. Development Eng., Tokyo Inst. of Technol. 2-12-1, O-okayama, Meguro-ku, Tokyo, 152 Japan**

**Abstract:**

A method for the holographic reconstruction of an acoustic field from a
finite sound source is discussed in detail. It is often experienced that the
holographic reconstruction based on the angular spectral method gives
unexpectedly erroneous reconstruction. This is due to the fact that the
singularity of the transfer function in the spatial frequency domain cannot be
treated accurately by the discrete system. [Waag et al., ``Cross-sectional
measurements and extrapolations of ultrasonic fields,'' IEEE Trans. Sonics
Ultrason. SU- 32, 26--35 (1985)]. In this paper, a reconstruction is proposed
that is based on the convolution of observed data and the transfer function
rather than the direct manipulation of data in the frequency domain. It is shown
that when the observed data are backpropagated to the plane that includes the
finite sound source, the sampling interval of the data can be taken to be
significantly larger than the half-wavelength. On the other hand, by taking the
pixel interval of the reconstructed source image as less than or equal to the
half-wavelength, the acoustic field at an arbitrary point in the space can be
evaluated by the successive forward propagation of the source image. The effect
of observing an aperture on the resolving power is also discussed.

ASA 132nd meeting - Hawaii, December 1996