Synthetic Aperture Imaging Using Acoustical Holography

We develop the mathematical basis for synthetic aperture imaging using acoustical holography in a form suitable for application to underwater viewing. Synthetic aperture technique by itself is a high resolution ultrasonic imaging system. By using acoustical holography we can improve the resolution even further. We preform demodulation and low band-pass filtering on the holographic signal. This is followed by heterodyne detection on the signal. Then we have the superposition of complex images using two frequencies or double exposure acoustical holographic interferometry. We then compare the resolution obtained after applying holographic technique with that before applying. We finally outline a system to test the above principle.