Underwater viewing system
US4119940A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 18, 1976 |
| Grant date | Oct 10, 1978 |
| Priority date | — |
| Expiry date | Oct 18, 1996 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S15/8977
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An underwater viewing system described herein substantially reduces the number of hydrophones in the receiving array and associated circuitry by providing a plurality of transmitting transducers spaced apart by a known distance, each emitting a coded output which is normally a separate frequency. The receiving array, which is preferably square or rectangular, includes a substantial number of receiving hydrophones. A synthetic aperture technique is applied in which the reflected signal arriving at each individual hydrophone is amplified, modulated with a lower frequency reference signal, filtered, digitized and stored in a memory, preferably as part of a computer. The computer also compares each digitized hydrophone signal against sine and cosine reference signals at each frequency and performs a Fourier analysis of each row and column to reconstruct a primary image. It also computes spatial modulation through complex multiplication, addition and subtraction and, through this, reconstructs adjacent images for each transducer frequency such that the ultimate image synthesized and displayed is one in which the effective number of image points is like that of a system in which the numb…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.