Abstract:

As part of an ongoing research effort related to new sonar systems, a system that can directly generate 3-D images of the underwater terrain has been developed. This 3-D forward-look (3-D FL) sonar consists of a separate projector and receiver hydrophone. The projector has a 1 deg fan beam, which is electronically scanned in 1-deg steps within the forward sector of view ((plus or minus)60 deg). The receiver hydrophone array oriented crosswise to the projector array can simultaneously form 100 beams within (plus or minus)50 deg, generating a profile for each of the positions of the projector fan beams. The sequence of profiles thus generated constitute a 3-D image of the underwater terrain or bottom targets. The system operates at 230 kHz with a 20% bandwidth. To speed the generation rate of the profiles a pseudorandom signal is used. The level of data processing required to generate the profiles is, however, significant. Test tank and stationary at-sea image data have been collected and will be presented. [Work sponsored by ONR.]