Manual scan imaging sonar

Details Manual scan imaging sonar Manual scan imaging sonar

1999-03-25

2001-05-01

Pihulic, Daniel T. (Department: 3662)

Communications, electrical: acoustic wave systems and devices

Echo systems

Distance or direction finding

Reexamination Certificate

active

06226227

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a self contained sonar device, and more specifically to a manual scan imaging sonar.
BACKGROUND OF THE INVENTION
A sonar (an acronym for Sound Navigation and Ranging) is a sensing system which measures features of an environment by the way in which that environment transmits, reflects and/or absorbs acoustic waves. It is generally used to detect objects or to determine their direction/bearing and distance/range. The earliest and simplest sonar imaging measured sound pulse reflections off the ocean floor. By determining the time between the transmission of the pulse and receipt of the reflection of the pulse, dividing by a factor of two, and multiplying by the speed of sound in water, depth could be determined.
Sonar units have many applications for individual, commercial, as well as government use. For example, individuals may use a sonar system to inspect docks and boat hulls, to recover lost objects, to treasure hunt, or to perform geographic and contour mapping of local areas. Commercial users may use sonar units to inspect ship hulls, to inspect oil wells, to assess underwater damage, and to assess fisheries, for example, by locating and mapping fish. Similarly, the government uses sonar units to perform underwater surveillance for security, reconnaissance, ordinance classification and hydrographic surveys; to recover lost objects; to train divers; to train marine mammals; to rescue people; to assess damage; and to inspect ship hulls.
Traditional sonar systems of similar application fall into three categories: single beam mechanical scan, single beam hand held, and multiple beam hand held. Each of these types of systems have limitations which can limit their usefulness. Existing mechanically scanned single beam sonar units require a stable platform and stepper motors for operation, which preclude use by a diver. Hand held single beam sonar units, on the other hand, only provide range information to the diver who is therefore required to remember the location of all targets. Multiple beam hand held sonar units continuously display range and bearing for targets over a limited sector, but require an amount of circuitry proportional to the sector coverage, thereby increasing the size of the sonar. Thus, the size and power requirements of a multiple beam hand held sonar significantly limit sector extent, resolution, and maneuverability.
SUMMARY OF THE INVENTION
The present invention integrates multiple technologies into a small, low cost, easily maneuverable, self-contained, single beam manual scan sonar. This manual scan sonar generates wide sector views from a single narrow beam using solid state components to eliminate moving parts. This unit may be used by divers and/or topside personnel to record large area underwater scenes and identify specific objects.
In one form, the manual scan imaging sonar comprises a piezoelectric ceramic transducer, orientation and motion sensors, amplification circuitry, and a microcomputer with display capability which is used for operator interface. The orientation and motion sensors may include a flux gate compass to measure bearing, an angle rate sensor (based on, for example, a solid state gyroscope) to more accurately measure bearing in between compass updates, and a fluid sensor to measure pitch and roll. These components are integrated into a small underwater housing easily used by the diver.
The data from these components is used to create the sonar image on the display. From the operator's point of view, the display image may be created by pointing the sonar in the direction at which the operator/diver is looking and starting sonar operation by pressing the user control start button. As the operator scans (rotates) the sonar across an area, the image is accumulated from each bearing and is displayed as a continuous video frame. As an area is re-scanned, new data replaces old data and is stored in its place. Sectors may be generated in either the horizontal or vertical planes.
By way of illustration and not of limitation, the uses of this device include large underwater surveys, location, detection, and classification of underwater objects, and generation of geophysically correct maps over an extended area. With this device, a diver can swim an area and obtain sonar images as he or she proceeds.
In another form of the invention, the manual scan imaging sonar comprises a piezoelectric ceramic transducer, orientation and motion sensors, amplification circuitry, a microcomputer with display capability which is used for operator interface, and a suspension means for allowing a topside operator to dip the sonar into the water and generate images.
In an alternative embodiment, the transducer may be mounted on a retractable pole which is submersible underwater while the rest of the system remains topside with the operator. By using a mechanically rigid pole, all rotations of the transducers may be measured by the motion and orientation sensors in the sonar electronics housing. In this configuration, the topside operator may use the sonar in the same manner as the underwater diver. The extension pole advantageously allows the operator to stay out of the water during the operation.
In either method of use, the images, as well as the position and orientation information pertaining to each image may be stored. With accurate position information and the orientation of the images obtained with the sonar's compass, the images may be properly rotated and translated so that they may be correctly overlaid. This would allow the generation of a mosaic of multiple images to form a much larger area map.
These and other features, and advantages, will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. It is important to point out that the illustrations may not necessarily be drawn to scale, and that there may be other embodiments of the present invention which are not specifically illustrated. Furthermore, as the figures may illustrate the same or substantially similar elements, like reference numerals will be used to designate elements that are the same or substantially similar in either shape or function.


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“Diver held imaging sonars,” Mar. 17 1999, pp. 1-3.

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