Communications – electrical: acoustic wave systems and devices – Acoustic image conversion – With memory means
Reexamination Certificate
1999-03-05
2001-03-06
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Acoustic image conversion
With memory means
C367S111000
Reexamination Certificate
active
06198692
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus suitable for searching an underwater object, and particularly to a fish finder, which transmits ultrasonics from a transducer attached to the bottom of a ship into a body of water, receives reflected ultrasonics from fish schools or the like, converts the received ultrasonics to an electric signal and further to digital data, and displays on a display device, based on the obtained data, an image representative of any schools of fish present and, if present, its concentration and size.
2. Description of the Related Art
Fish finders visually display an image representative of the concentration and size of any school of fish present in an operation area of a fishing boat, and are widely used in such fishing boats and other watercraft. However, conventional fish finders have a fault in that they require a significant time to detect a school of fish. Specifically, for accurate detection and display of the location and size of a school of fish, a transducer with narrow directivity must be used. However, when such a transducer with narrow directivity is used, only a narrow area can be scanned. Therefore, in order to locate fish schools, the ship must move around its operation zone to conduct a close search. This contributes to increased operation hours and, as a consequence, increases labor and fuel costs.
SUMMARY OF THE INVENTION
One object of the present invention is to eliminate the need for inefficient seeking and tracking of objects in water, e.g., schools of fish, such as close searches while moving within an operation zone. This object is achieved in the present invention by performing 3D scanning with respect to a space under the water surface and giving ray tracing to obtained data for 3D displaying on a 2D screen.
A fish finder according to the present invention comprises a scanner, a ray tracer, and a display. The scanner three-dimensionally scans the area beneath the water's surface using directed supersonics, to obtain reception data revealing the presence or absence, concentration, and size of any schools of fish in the water. The data is expressed relative to a 3D polar coordinate system with the ship's hull used as the origin. The ray tracer gives ray tracing processing to the reception data obtained by using the scanner so that an image similar to the image that would be seen when viewing the space from a hypothetical viewing point, is displayed on a display screen. An image representing the presence or absence, concentration, and size of any underwater schools of fish is displayed on the display screen based on the reception data subjected to ray tracing processing. Therefore, according to the present invention, users can obtain that information for a region around their ship without conducting wasteful effort, such as close search while moving the ship around. Further, since the image displayed on the display screen is a 3D image including depth information, advantageously, the user can intuitively understand the size, condition, and other information concerning any displayed fish schools.
A scanner of this invention can be achieved by using, for example, a 2-dimensional (2D) transducer array capable of changing its beam direction two-dimensionally. That is, a 2D transducer array comprising transducers arranged in an array, is fixedly attached to a ship's hull so that each transducer transmits or receives a signal. The transmitted or reception signal is desirably subjected to phase shifting whereby the beam direction can be two-dimensionally changed (e.g., both in the fore/aft direction and in the post/starboard direction). This allows 3D scanning of the area below the water's surface. However, this structure has a problem such that too many transducers (and associated phase shifters) are required, which inevitably increases the size of such a device as a whole.
To avoid this problem, a plurality of 1D transducer arrays are fixedly attached to the ship's hull such that the transducer arrangement directions thereof cross one another. A 1D transducer array mentioned here is a transducer array having a structure in which a plurality of transducers are one-dimensionally arranged in a predetermined direction. As is well known, the beam width of a transducer array on a plane perpendicular to the transducer arrangement direction is the same as that when a transducer is used alone. However, the beam width on a plane perpendicular to that plane, i.e., a plane in parallel to the transducer arrangement direction, is significantly narrower than that when a transducer is used alone.
Therefore, in rendering the present invention into practice, preferably, a first 1D transducer array is arranged such that the transducer arrangement direction thereof (i.e., a direction in which the beam direction is changeable) is parallel to a first plane which crosses the horizontal plane, and such that a second 1D transducer array is arranged such that the transducer arrangement direction thereof is parallel to a second plane which crosses to both the horizontal plane and the first plane. Further, while the first transducer array transmits ultrasonics into the body of water at a predetermined timing, a transmitter/receiver is provided for supplying data relating to the ultrasonics which have been transmitted through the body of water and received by the second transducer array, to the ray tracer. Further, a beam transmitting direction controller is provided for shifting the phase of a signal relating to each of the transducers constituting the first transducer array so that the beam direction &thgr; on the first plane, of the first transducer array is changed within a predetermined angular range. Also, a receiving beam direction controller is provided for shifting the phase of a signal corresponding to each of the transducers constituting the second transducer array, so that the beam direction &phgr; on the second plane, of the second transducer array is repeatedly changed within a predetermined angular range during a short period when a changing amount of the beam direction &thgr; and a propagation distance of the ultrasonics remain within a predetermined value. As described above, when the first and second transducer arrays are used for transmission and receiving, respectively, and phase shifts for the transmitting and reception signals are desirably controlled, it is possible to two-dimensionally scan the area underwater, similar to a case in which an 2D transducer array for two-dimensionally steering a narrow beam is used. Moreover, when the beam is formed in a fan-like shape (a fan beam) on a plane which crosses the transducer arrangement direction, the 3D area of scanning can be enhanced. Further, the number of transducers (and associated phase shifters) can be reduced as a whole, which makes it possible to reduce the device size.
When the first transducer array is used not only for transmission but also for receiving such that the received outputs of the first and second transducer arrays are combined (e.g., to obtain a product of the outputs), resultant reception data with much narrower reception width is supplied to the ray tracer. With this arrangement, the width of a beam formed by the first transducer array can be narrower than that in the case where the first transducer array is exclusively used for transmission. This consequently renders the device less affected by noises (e.g., acoustic waves from anything other than a fish shoal) and improves resolution. This arrangement can be achieved without increasing transducer size.
A ray tracer in this invention can be realized as a means for controlling or operating a write address for use in writing reception data into a 2D memory space (e.g., an image memory) which corresponds to a display screen. That is, when reception data obtained from a scanner is written into a 2D memory space corresponding to a display screen, the memory address with respect to the memory space is controlled such that the reception data r
Japan Radio Co. Ltd.
Oliff & Berridg,e PLC
Pihulic Daniel T.
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