A New Holographic Method for Improving Lateral Resolution in Ultrasonic B-Scan Imaging

摘要

This paper describes a new ultrasonic holographic imaging method, UHB imaging (ultrasonic holographic B-scan imaging) invented by the author in the University of Oulu. The starting point was an attempt to improve the lateral resolution of conventional ultrasonic B-scan imaging by using the holographic principle. The object is illuminated by transmitting wide-angle ultrasonic bursts from each point of the hologram line. The echos reflected from each distance of the transducer are measured at each point using a time-gating principle. Both amplitude and phase are measured and stored in a computer memory. The image is then reconstructed from these data in the computer by a method based on the backward propagation of wavefronts. Mathematically, this process is based on a Fourier transform, an inverse Fourier transform, and a spectrum shift theorem. If this process is performed by a fast, specialized microcomputer, it seems to be possible to develop UHB imaging as a real time method.