Sonar transducer assembly

Sonar systems and associated methods are provided herein for sonar image generation. The sonar system is configured to enable rotation of a transducer array that includes at least two transducer elements. The transducer array may be mounted to a trolling motor capable of being rotated. The transducer elements can be positioned to enable use of interferometry to obtain angle information regarding sonar returns. The angle and range of each sonar return can be used to form images, such as a 2D forward looking image of the underwater environment. A heading detector can be used to obtain a heading of the transducer elements to enable creation of a 2D radar-like image of the underwater environment. Additionally, the heading, angle, and range of the sonar returns can be used to form a 3D image of the underwater environment.

FIELD OF THE INVENTION

Embodiments of the present invention relate generally to sonar systems and, more particularly, to a sonar system configured for imaging of an underwater environment relative to a watercraft.

BACKGROUND OF THE INVENTION

Sonar (SOund Navigation And Ranging) has long been used to detect waterborne or underwater objects. For example, sonar devices may be used to determine depth and bottom topography, detect fish, locate wreckage, etc. In this regard, due to the extreme limits to visibility underwater, sonar is typically the most accurate way to locate objects underwater. Sonar transducer elements, or simply transducers, may convert electrical energy into sound or vibrations at a particular frequency. A sonar pulse is transmitted into and through the water and is reflected from objects it encounters. The transducer may receive the reflected sound (the “sonar returns”) and convert the sound energy into electrical energy. Based on the known speed of sound, it is possible to determine the distance to and/or location of the waterborne or underwater objects. The sonar return signals can also be processed to be displayed in graphical form on a display device, giving the user a “picture” of the underwater environment. The signal processor and display may be part of a unit known as a “sonar head” that is connected by a wire to the transducer mounted remotely from the sonar head. Alternatively, the sonar transducer may be an accessory for an integrated marine electronics system offering other features such as GPS, radar, etc.

Sonar systems may be used, in some cases, to create an image of an underwater environment. However, some sonar systems may be limited in their capabilities, such as requiring a watercraft to actively travel along the surface of the water in order to acquire the necessary sonar return data to form the image. As such, improved sonar systems are needed to provide for enhanced techniques for creating an image of an underwater environment.

BRIEF SUMMARY OF THE INVENTION

Some embodiments of the present invention provide sonar systems that are configured to enable rotation of a transducer array that includes at least two transducer elements. In some embodiments, the transducer array may be mounted to a trolling motor capable of being rotated. The transducer elements can be positioned to enable use of interferometry to obtain angle information regarding sonar returns. The angle and range of each sonar return can be used to form images, such as a 2D forward looking image of the underwater environment. A heading detector can be used to obtain a heading of the transducer elements to enable creation of a 2D radar-like image of the underwater environment. Additionally, the heading, angle, and range of the sonar returns can be used to form a 3D image of the underwater environment. In this regard, a robust sonar system is formed that allows for flexibility of image generation.

Accordingly, embodiments of the present invention provide a sonar system that is configured for imaging of an underwater environment relative to a watercraft.

According to one aspect of the present invention, a sonar system for imaging an underwater environment relative to a watercraft is provided. The sonar system comprises a housing and a transducer array positioned within the housing. The transducer array comprises a first transducer element configured to transmit one or more sonar pulses into the underwater environment. The first transducer element is further configured to receive first sonar returns from the sonar pulses and convert sound energy from the first sonar returns into first sonar return data. The transducer array further comprises a second transducer element configured to receive second sonar returns from the sonar pulses and convert sound energy from the second sonar returns into second sonar return data. The housing is mountable so as to enable rotation of the transducer array with respect to the watercraft. The sonar system further comprises a sonar signal processor configured to receive the first sonar return data and the second sonar return data. The sonar signal processor is further configured to generate a set of 2D sonar return data based on the first sonar return data and the second sonar return data by using interferometry to process the first sonar return data and the second sonar return data to determine an angle associated with each sonar return in the set of 2D sonar return data.

In some embodiments, the housing is mountable to at least one of a trolling motor or a steerable device.

In some embodiments, the angle is associated with a vertical angle between a theoretical plane corresponding to a surface of a body of water and the sonar return. Additionally, the first transducer element and the second transducer element may be vertically stacked within the housing and each define an emitting surface that is aimed at approximately a same angle with respect to the surface of the body of water. Additionally, the first transducer element and the second transducer element may each define a rectangular shape and be configured to transmit and/or receive a fan-shaped sonar beam. The fan-shaped sonar beam may define a beamwidth of approximately 15° in a horizontal direction and approximately 90° in a vertical direction.

In some embodiments, the sonar system further comprises a third transducer element configured to receive third sonar returns from the sonar pulses and convert sound energy from the third sonar returns into third sonar return data. The sonar signal processor may be further configured to receive the third sonar return data and generate the set of 2D sonar return data further based on the third sonar return data by using interferometry to process the first sonar return data, the second sonar return data, and the third sonar return data to determine the angle associated with each sonar return in the set of 2D sonar return data.

In some embodiments, the sonar signal processor may be configured to generate, based on the set of 2D sonar return data, 2D forward looking sonar image data associated with a 2D forward looking image of the underwater environment. The 2D forward looking image may represent, at least, depth contours of a portion of the underwater environment in front of the transducer array.

In some embodiments, the sonar system further comprises a heading sensor configured to detect a heading of the transducer array. The set of 2D sonar return data may be associated with the detected heading when the sonar returns associated with the set of 2D sonar return data are captured and the sonar signal processor may be configured to generate, based on the set of 2D sonar return data and the detected heading, 3D sonar image data associated with a 3D image of the underwater environment. Additionally, the sonar signal processor may be configured to generate the 3D image data by positioning at least a portion of the set of 2D sonar return data as a theoretical vertical 2D slice at an angle with respect to a point in the 3D image corresponding to a position of the transducer array, wherein the angle is determined based on the detected heading. Additionally or alternatively, the sonar signal processor may be configured to generate the 3D image data by processing at least a portion of the set of 2D sonar return data with at least a portion of a second set of 2D sonar return data to generate a 3D representation of at least a portion of the underwater environment.

In some embodiments, the sonar system may further comprise a heading sensor configured to detect a heading of the transducer array. The at least one of the first sonar return data or the second sonar return data may be associated with the detected heading when the respective at least one of first sonar returns or second sonar returns are captured and the sonar signal processor may be configured to generate, based on the at least one of the first sonar return data or the second sonar return data and the detected heading, 2D radar-like sonar image data associated with a 2D radar-like image of the underwater environment.

In some embodiments, the first and second transducer elements may each be configured to receive respective first and second sonar returns from the sonar pulses while the first and second transducer elements are rotated at variable speeds.

In some embodiments, the first and second transducer elements may each be configured to receive respective first and second sonar returns from the sonar pulses while the first and second transducer elements are rotated at a user-defined speed.

In some embodiments, the sonar system may further comprise a heading sensor configured to detect a heading of the transducer array. The set of 2D sonar return data may be associated with the detected heading when the sonar returns associated with the set of 2D sonar return data are captured and at least one of the first sonar return data or the second sonar return data may be associated with the detected heading when the respective at least one of first sonar returns or second sonar returns are captured. The sonar signal processor may be configured to generate at least one of: 2D forward looking sonar image data associated with a 2D forward looking image of the underwater environment based on the set of 2D sonar return data, wherein the 2D forward looking image represents, at least, depth contours of a portion of the underwater environment in front of the transducer array; 2D radar-like sonar image data associated with a 2D radar-like image of the underwater environment based on the at least one of the first sonar return data or the second sonar return data and the detected heading; or 3D sonar image data associated with a 3D image of the underwater environment based on the set of 2D sonar return data and the detected heading. Additionally, the sonar system may further comprise a display configured to display at least one of the 2D forward looking image, the 2D radar-like image, or the 3D image. Additionally, the display may be configured to display, on a single screen, at least two of the 2D forward looking image, the 2D radar-like image, or the 3D image. Additionally, the display may be configured to display chart information on a single screen with the at least one of the 2D forward looking image, the 2D radar-like image, or the 3D image.

According to another aspect of the present invention, a sonar transducer assembly for imaging an underwater environment relative to a watercraft is provided. The sonar transducer assembly comprises a housing and a transducer array positioned within the housing. The transducer array comprises a first transducer element configured to transmit one or more sonar pulses into the underwater environment. The first transducer element is further configured to receive first sonar returns from the sonar pulses and convert sound energy from the first sonar returns into first sonar return data. The transducer array comprises a second transducer element configured to receive second sonar returns from the sonar pulses and convert sound energy from the second sonar returns into second sonar return data. The housing is mountable so as to enable rotation of the transducer array with respect to the watercraft. The sonar transducer assembly further comprises a sonar signal processor configured to receive the first sonar return data and the second sonar return data. The sonar signal processor is further configured to generate a set of 2D sonar return data based on the first sonar return data and the second sonar return data by using interferometry to process the first sonar return data and the second sonar return data to determine an angle associated with each sonar return in the set of 2D sonar return data.

According to another aspect of the present invention, method for imaging an underwater environment relative to a watercraft is provided. The method comprises transmitting one or more sonar pulses into the underwater environment from a first transducer element of a transducer array. The transducer array is positioned within a housing. The housing is mountable so as to enable rotation of the transducer array with respect to the watercraft. The method further comprises receiving first sonar returns from the sonar pulses with the first transducer element, wherein the first transducer element is configured to convert sound energy from the first sonar returns into first sonar return data. The method further comprises receiving second sonar returns from the sonar pulses with a second transducer element of the transducer array. The second transducer element is configured to convert sound energy from the second sonar returns into second sonar return data. The method further comprises receiving the first sonar return data and the second sonar return data with a sonar signal processor. The method further comprises generating, by the sonar signal processor, a set of 2D sonar return data based on the first sonar return data and the second sonar return data by using interferometry to process the first sonar return data and the second sonar return to determine an angle associated with each sonar return in the set of 2D sonar return data.

DETAILED DESCRIPTION OF THE INVENTION

Sonar systems, such as sonar depth finders, sidescan sonars, downscan sonars, and sonar fish finders, are commonly employed by boaters, sport fishermen, search and rescue personnel, researchers, surveyors, and others. Some embodiments of the present invention provide sonar systems that are configured to enable rotation of a transducer array that is formed of at least two transducer elements.FIG. 1illustrates an example sonar system that includes a transducer assembly136that is mounted to a trolling motor120of a watercraft100floating on a surface110of a body of water.

As described in greater detail herein, in some embodiments, the transducer assembly136may include a transducer array with at least two transducer elements. The transducer elements may each be configured to transmit one or more sonar pulses and/or receive sonar returns within a beam pattern. The sonar returns may be processed using interferometry to help determine the position from which each sonar return originated. In some embodiments, the return data may generate an angle from the transducer to each position from which the returns are received with respect to a theoretical plane (e.g., corresponding to a surface of a body of water).

FIG. 1shows an example beam pattern140of 90° in the vertical direction. Additionally, the transducer array is oriented forwardly and downwardly from the housing and mounting position on the trolling motor. A user may direct the facing of the transducer assembly136by rotating the trolling motor120, such as by the shaft112. Thus, depending on the direction the transducer assembly136is facing, the user can obtain an image of the relative portion of the underwater environment. As described in greater detail herein, the sonar returns from the transducer array can be used to generate a number of different images that portray information regarding the underwater environment, which can be useful for fishing and watercraft control.

Example System Architecture

FIG. 2is a basic block diagram illustrating a sonar system30capable for use with multiple example embodiments of the present invention. As shown, the sonar system30may include a number of different modules or components, each of which may comprise any device or means embodied in either hardware, software, or a combination of hardware and software configured to perform one or more corresponding functions. For example, the sonar system30may include a sonar signal processor32, a transceiver34and a transducer assembly36and/or numerous other peripheral devices such as one or more multi-function displays38. One or more of the modules may be configured to communicate with one or more of the other modules to process and/or display data, information or the like from one or more of the modules. The modules may also be configured to communicate with one another in any of a number of different manners including, for example, via a network40. In this regard, the network40may be any of a number of different communication backbones or frameworks including, for example, Ethernet, the NMEA2000framework or other suitable networks. The network may also support other data sources, including GPS, autopilot, engine data, compass, radar, etc.

The display38may be configured to display images and may include or otherwise be in communication with a user interface39configured to receive an input from a user. The display38may be, for example, a conventional LCD (liquid crystal display), a touch screen display, or any other suitable display known in the art upon which images may be rendered. Although each display38ofFIG. 2is shown as being connected to the sonar signal processor32via the network and/or via an Ethernet hub, the display38could alternatively be in direct communication with the sonar signal processor32in some embodiments, or the display38, sonar signal processor32and user interface39could be in a single housing. The user interface39may include, for example, a keyboard, keypad, function keys, mouse, scrolling device, input/output ports, touch screen, or any other mechanism by which a user may interface with the system. Moreover, in some cases, the user interface39may be a portion of one or more of the displays38.

In some embodiments, with reference toFIG. 2A, the transducer assembly36may include a heading sensor69that detects the heading of the transducer assembly. In this regard, a detected heading can be linked to captured sonar returns for use in image generation, as will be described in greater detail herein.

The transducer assembly36, with continued reference toFIG. 2A, may also include one or more transducer elements positioned within the housing as a transducer array47.FIG. 3illustrates a cross-sectional view of an example transducer assembly36. The example transducer array47is shown having two transducer elements60,62.

The emitting faces of each transducer element60,62may be oriented downwardly and outwardly as shown. In this regard, the transducer array47may be held at a predetermined angle relative to the surface of the body of water. For example, the emitting surfaces of the transducer array47may be oriented at 30 degrees from the surface of the body of water in order to transmit and/or receive sonar pulses. The transducer elements60,62may also be positioned at a predetermined distance from each other (e.g., a predetermined distance between the centers of the transducer elements, also referred to as element pitch). The predetermined distance may be designed based on the frequency or wavelength of the sonar pulses. For example, the predetermined distance between the transducer elements60,62may be a fraction or multiple of the wavelength of the sonar pulses (e.g., 1/10, ⅛, ⅙, ¼, ½, 1, 2, 3, or 4 times the wavelength). In some embodiments, the predetermined distance may be less than or equal to half the wavelength of the sonar pulses, as discussed below.

In some embodiments, the transducer arrays may include more than two transducer elements. For example,FIG. 3Ashows an embodiment of the transducer array47′ having four transducer elements94,96,98,100. The array47′ may further include absorption material and shielding. Each of the transducer elements94,96,98,100may be positioned a predetermined distance from each other. In some embodiments, the distance between elements may differ.

In some embodiments, the third98and fourth100transducer elements may be electrically connected in parallel to act as a single element. For example, the third98and fourth100transducer elements98,100may be connected in parallel to act as a single element. In such embodiments, the combination of elements98and100may be referred to as a single transducer element.

The transducer elements94,96,98,100may be electrified substantially simultaneously to receive the sonar returns and then convert sound energy from the sonar returns into respective sonar return data that is provided to the sonar signal processor.

In some embodiments, the transducer elements are vertically stacked within the housing such that their longitudinal lengths extend in the horizontal direction. Such a configuration produces a beam pattern that has a fan-shaped beam with a larger beamwidth in the vertical plane and a smaller beamwidth in the horizontal plane. As shown inFIGS. 3 and 3A, the emitting surface of each transducer element may be aimed at the same angle with respect to the surface of the body of water (e.g., 30° inFIGS. 3 and 3A).

In some embodiments detailed herein, a single sonar pulse may be transmitted such that all of the transducer elements may receive sonar returns (e.g., a pulse that is long enough for each set of pairwise elements to receive), or, alternatively, multiple pulses may be transmitted. In some embodiments, any or all of the transducer elements may be configured to transmit one or more sonar pulses into the underwater environment. For example, with reference toFIG. 3A, the second transducer element96is transmitting a sonar pulse within the beam pattern140that defines 90° in the vertical plane and 15° in the horizontal plane (shown inFIG. 4A). In some embodiments, the electrically coupled transducer elements (e.g., elements98,100) may be configured to transmit sonar pulses into the water. The designed beam pattern for the transmitted sonar pulses may be configured to ensonify a region of the underwater environment that causes sonar returns to be received within the receive beam of each of the transducer elements94,96,98,100.

Additional examples of transducer array orientations, configurations, processing, and other information may be found in U.S. patent application Ser. No. 14/618,987 filed Feb. 10, 2015, and entitled “A Transducer Array having a Transceiver,” which reference is hereby incorporated by reference herein in its entirety.

As noted above, some embodiments of the present invention provide a sonar transducer assembly configured for 360 degree imaging of an underwater environment under a watercraft.FIGS. 4A, 4B, and 4Cillustrate an example sonar transducer assembly136mounted to a trolling motor120of a watercraft100.

Example Rotational Mounting

As noted above, in some embodiments, the sonar transducer assembly36may comprise a housing that is mountable to a watercraft (or device mounted to a watercraft) so as to enable rotation of the transducer elements with respect to the watercraft. With reference to FIGS.4A,4B, and4C, the transducer assembly136may be mounted to a trolling motor120such that the transducer assembly136(and the transducer elements contained therein) may be rotated up to 360 degrees with respect to the watercraft100along with the trolling motor120. For example, with reference toFIG. 4A, the transducer assembly136and the trolling motor120may be aimed to transmit sonar pulses and/or receive sonar returns (e.g., defined by the beam pattern140) generally forward from the watercraft100. However, with reference toFIG. 4C, the sonar transducer assembly136may be rotated (e.g., along arrow A) such that the transducer assembly136is aimed to transmit sonar pulses and/or receive sonar returns (e.g., defined by the beam pattern140) generally 45 degrees clockwise from forward of the watercraft100. This rotation may continue such that the transducer assembly136may transmit sonar pulses and receive sonar returns from any angle with respect to forward from the watercraft (e.g., the transducer assembly136may rotate 360 degrees).

Though the above described embodiment details a sonar transducer assembly mounted to a trolling motor to enable rotation, some embodiments of the present invention contemplate other ways to enable rotation of the transducer elements. Moreover, rotation may be achieved by any means (e.g., a motor, manually, steerable device, etc.).

Additionally, as noted above, some embodiments of the present invention provide a transducer assembly that enables imaging while the transducer assembly rotates at variable speeds. Further, in some embodiments, the sonar transducer assembly may provide imaging while being rotated continuously (e.g., without pauses). Moreover, in some embodiments, the transducer assembly may provide imaging while being rotated at a user-defined speed. Such ability is enabled due to the width of the beam pattern in the horizontal direction. In the example shown inFIG. 4A, the beam pattern defines 15°, which is large enough to enable receipt of sonar returns while still accounting for an unknown (and perhaps fast) change in direction due to rotation of the transducer assembly. Said differently, due to the time delay of sound and the unknown rotational speed of the transducer assembly, it is difficult to predict where the sonar pulses need to be for receipt by the transducer elements to capture adequate sonar returns. Thus, the depicted embodiment ofFIG. 4Aenables 15 degrees of sonar pulses to account for the time delay of sound and the unknown rotational speed of the transducer assembly. In such a regard, even though the transducer assembly may be actively rotating, the transducer elements may receive sonar returns with adequate detail to produce an image.

Though the above described embodiments detail 15 degrees of sonar pulses, some embodiments contemplate other configurations. Further, some embodiments of the present invention may utilize a separate transmit transducer element, such as to provide for a wider horizontal beam pattern, while still enabling narrower (and more defined) sonar returns for imaging.

Example Image Processing

As noted above, some embodiments of the present invention comprise a sonar signal processor. In some embodiments, the sonar signal processor is configured to receive sonar return data resulting from the transducer elements in the transducer array. Additionally, in some embodiments, the sonar signal processor is further configured to generate one or more images (or image data corresponding to one or more images) of the underwater environment based on the received sonar return data and/or other information (e.g., a detected heading from the heading sensor).

In some embodiments, the sonar signal processor is configured to generate 2D radar-like sonar image data, 2D forward looking sonar image data, and/or 3D sonar image data. As detailed herein, the corresponding 2D radar-like image, 2D forward looking image, and/or 3D image can be displayed to a user on a display (e.g., separately, split-screen mode, etc.). Additionally, in some embodiments, other information (e.g., depth, temperature, etc.) may be displayed with one or more of the generated images. Additionally, in some embodiments, chart information, GPS information, navigation information, among others may be displayed with one or more of the generated images. In this regard, some embodiments of the present invention provide for robust imaging options that are useful for fisherman and boaters.

In some embodiments, the sonar signal processor is configured to generate 2D radar-like sonar image data corresponding to a 2D radar-like image of the underwater environment. In some embodiments, the 2D radar-like image is formed as a composite of sonar returns respectively arranged in positions corresponding to the rotation of the sonar transducer assembly. As the sonar transducer assembly rotates, the transducer elements may capture sonar returns. These sonar returns (which include a range) may be processed and formed into sonar image data by the sonar signal processor. The resulting image of the underwater environment may be generated by arranging the resulting sonar images in the proper order that corresponds with the position and heading of the transducer elements when receiving the sonar returns.

Along these lines, in some embodiments, the sonar transducer assembly may comprise a heading sensor configured to detect the heading of the transducer elements. The detected heading may be associated with sonar returns captured by the transducer elements. Further, the detected heading may be transmitted to the sonar signal processor for aiding in arranging of the sonar images corresponding to each set of captured sonar returns. For example, each sonar image may have an associated heading that enables the sonar signal processor to determine its arrangement to create the 2D radar-like image of the underwater environment. Further, in some embodiments, the sonar signal processor may take into account the relative heading of the watercraft as compared to the heading of the associated sonar returns when creating the image.

FIG. 5shows a diagram illustrating an example display of an underwater environment. The transducer assembly may be positioned at162and aimed such that the transducer elements received sonar returns in a heading associated with a first volume171. The sonar signal processor may process the sonar returns associated with the first volume171and, using the heading, position the sonar image of the first volume171of the underwater environment160. The sonar image of first volume171may include a portion of an object165.

With reference toFIG. 5A, as the transducer assembly rotates clockwise, additional sonar images may be arranged on the screen160. In the depicted embodiment, the transducer elements may have rotated slightly clockwise to capture sonar returns within a second volume172. Further, the transducer elements may have rotated slightly clockwise again to capture sonar returns within a third volume173. The sonar signal processor may process the sonar returns associated with second and third volumes172and173and, using the respective headings, position the sonar images of the volumes172and173on the screen160to further define the image. As shown inFIG. 5A, further detail of the object165can be seen with the addition of the sonar images from second and third volumes172and173. In such a regard, as the transducer assembly rotates, the image of the underwater environment can be further defined (e.g., until it is complete).

As noted above, some embodiments of the present invention seek to provide a transducer assembly that enables imaging while the transducer assembly rotates at variable speeds. In such a regard, as is consistent with the above disclosure, the receive-only transducer element may capture sonar returns from volumes that are not consecutively positioned. For example, the speed at which the transducer assembly is rotating may cause gaps to occur between the sonar returns. The sonar signal processor, in some embodiments, may be configured to account for such gaps when creating the image of the underwater environment. Indeed, use of the detected heading associated with the sonar returns may aid in proper arrangement of each sonar image of each respective volume. For example,FIG. 6illustrates an image of the same underwater environment160shown inFIG. 5A. However, the transducer assembly has rotated at variable speeds such that the sonar images of the second and third volumes172′ and173′ are different than that of the second and third volumes172and173shown inFIG. 5A. In this regard, the sonar signal processor has accounted for the variable speed of rotation by properly arranging the sonar images of the second and third volumes172′ and173′ on the screen160using their respective headings. For example, in the depicted embodiment, the object165is shown in pieces of165′ and165″ in volumes172′ and173′ respectively.

Example 2D Forward Looking Imaging

In some embodiments, the sonar signal processor is configured to generate 2D forward looking sonar image data corresponding to a 2D forward looking image of the underwater environment. In some embodiments, the 2D forward looking image is formed as a composite of sonar returns respectively arranged as the sonar returns are captured (e.g., in waterfall form).

The sonar returns used to generate the corresponding 2D forward looking sonar image data are received with at least a first transducer element and a second transducer element. The sonar returns define a range. Interferometry between the corresponding first sonar returns from the first transducer element and second sonar returns from the second transducer element is used to define an angle associated with each sonar return. Depending on the orientation of the transducer elements, two transducer elements stacked with respect to each other in a direction can be used to determine an angle of a sonar return based on differences between the returned information for each sonar return relative to the different transducer elements. For example, in the embodiments shown inFIG. 3, the transducer element60is vertically stacked above transducer element62. Due to the shape of the resulting beam pattern, there are ˜90° of sonar return information in the vertical plane being received by both transducer elements60,62. Thus, having vertically stacked transducer elements60,62allows differentiation between the angles of sonar returns within the 90° beam pattern in the vertical plane. In this manner, the calculated angle may be associated with a vertical angle between a theoretical plane corresponding to a surface of a body of water and the sonar return (with the transducer assembly as the center point).

The resulting angle and range information for the sonar return data can be used by the sonar signal processor to generate the 2D forward looking sonar image data that results in the 2D forward looking image. Such an image is useful for providing pertinent navigation and fishing information to a user.

With reference toFIGS. 7-9, the following is an explanation of an example use of interferometry to determine corresponding angles of the sonar returns. Turning toFIG. 7, a simplified example is shown of the transducer elements60,62receiving returns from a single point74on the floor of the body of water or other reflecting surface to generate a point of return data including a distance and/or time to the point as well as an angle α. During actual interferometric sonar sounding, sonar returns may be received from across the entire beam width of the transmitted sonar pulses to generate a plurality of points of return data in two-dimensional slices from each transmitted sonar pulse. The returns A, B may originate at the same time from the same point74and be received by the first60and second62transducer elements respectively.

Each of the transducer elements60,62may produce one-dimensional distance data in response to receiving sonar returns A, B, respectively, from the point74. The sonar signal processor may combine this one-dimensional distance data from each element with the predetermined distance between the elements and the angle α between the orientation of the transducer array and the surface of the body of water to determine the position of the point74of origin of the sonar return. The position of the point74may be represented as two-dimensional coordinates with respect to the boat or housing, or may alternatively be represented as a distance and angle from the boat or housing. In yet another embodiment, the position may be determined as an absolute position value by comparing the interferometric data with GPS or other positioning data.

In some embodiments, the location of the point of origin for the sonar returns may be determined via a phase difference between the returns received at the respective transducer elements60,62. Turning toFIG. 8, another simplified example of a transducer array receiving sonar returns A, B is shown. In this embodiment, the sonar returns from the point74are represented as waves A, B received by the first60and second62transducer elements. The returns A, B originating from the same point74on the floor of the body of water or other reflecting surface may have substantially the same frequency, amplitude, and wavelength. Given that the waves A, B may be expected to have the same properties when received at both the first60and second62transducer element, a phase difference between the two waves, in combination with the predetermined distance and angle of the transducer array, may provide the location of their point74of origin. As shown inFIG. 8, the returns A, B may be received by the respective transducer elements60,62at different positions76,78along the respective waves. The phase, or position, of the wave at the point it is received by the transducer elements may be compared to determine the angle of the point74of origin. In some embodiments, the angle (e.g., β shown inFIG. 8) may be derived by using an interferometer (e.g., as part of or separate from the sonar signal processor) to calculate a phase difference between the two returns which is converted into a single physical angle, which would be the angle from the seafloor point to the phase center of the array (the imaginary point directly between the two transducer elements being used for the interferometry calculation).

FIG. 9shows a plot overlaying the returns A, B as received by each transducer element60,62versus time. The phase difference θ between the returns A, B may indicate the degree of offset between the returns, which, when combined with the predetermined distance d, one-dimensional distance data, frequency of the returns, and/or angle of the transducer arrays may produce the position of the point74of origin. The angle β to the point74may be represented by the following Equation (1):

Where λ represents the wavelength of the return, θ represents the received phase difference, and d represents the predetermined distance.

Though the above explanation focuses on two transducer elements, three or more transducer elements (e.g., transducer elements94,96,98,100) may be used with embodiments of the present invention to determine angle information through interferometry.

In some embodiments, the sonar signal processor is configured to ignore the detected heading that corresponds to the captured sonar return data when generating the 2D forward looking sonar image data. In this regard, the resulting 2D forward looking image is displayed irrespective of the heading of the transducer assembly, leaving interpretation for the user as to the direction and orientation of the image of the underwater environment shown in the display.

FIGS. 10 and 11illustrate forward looking displays300and400derived from sonar return data in accordance with implementations of various techniques described herein. In particular, the 2D forward looking images300and400may represent depth contours of an underwater environment that is in front of the transducer assembly. The 2D forward looking images300and400may have respective depth lines310and410plotted on an x-y graph, where the depth lines correspond to the depth contours of the underwater environment in front of the transducer assembly. A vertical axis of the x-y graph may be used to display a scale of depths that correspond to the depth lines. The horizontal axis may be used to display a range of distance from the transducer assembly. A position of the watercraft on the 2D forward looking image may be represented by where the vertical axis meets the horizontal axis.

In one implementation, as the watercraft traverses through the body of water, the sonar signal processor may analyze the sonar data in real-time to produce the 2D forward looking image that corresponds to the real-time marine environment in front of the transducer assembly.

Further, the portions of the x-y graph underneath the depth lines may be filled in with color to provide a visual representation of the underwater environment. Such an implementation may provide an easier way for a user to interpret depth and forward range information.

The sonar signal processor may also perform auto-ranging to keep the 2D forward looking image in a range that is usable for the user. In particular, a range of the vertical axis may be determined based on the sonar data, such that the sonar signal processor may automatically detect a maximum depth in the data. A range of the horizontal axis may be determined based on a range of the vertical axis. For example, the range of the horizontal axis may be a multiple of the range of the vertical axis. Thus, as the range of the vertical axis increases in depth, the range of the horizontal axis may also increase.

In addition, as shown inFIG. 11, a point cloud representation420may also be included in the 2D forward looking image. In one implementation, the point cloud representation420may include information derived from raw sonar data regarding debris, fish, and/or the like that may be positioned in the underwater environment in front of the transducer assembly. In another implementation, the sonar signal processor may not include the point cloud representation420in the 2D forward looking image unless prompted by a user.

The 2D forward looking images may be developed using real-time marine electronics data (e.g., real time sonar data), as well as historical marine electronics data (e.g., historical sonar data and/or bathymetric charts). In another implementation, the 2D forward looking image may be selected as an option by the user from another representation being visualized. For example, the sonar signal processor may display a navigational chart having a heading line extension to a user, where the line extension may be used to indicate a future location of the watercraft if the watercraft maintains the current course. The sonar signal processor may provide an option on the navigational chart that, when selected by the user, will change the display to visualize the 2D forward looking image.

Example 3D Imaging

In some embodiments, the sonar signal processor is configured to generate 3D sonar image data corresponding to a 3D image of the underwater environment.

The sonar returns used to generate the corresponding 3D sonar image data may be received with at least and first transducer element and a second transducer element. The sonar returns may define a range. As detailed above, interferometry between the corresponding first sonar returns from the first transducer element and second sonar returns from the second transducer element is used to define an angle associated with each sonar return. In this regard, 2D (range and angle) sonar return data is generated.

With reference toFIG. 4A, the corresponding beam pattern140for receipt of the sonar returns may define a small beamwidth (e.g., 15°) in the horizontal direction. In this way, a relatively thin slice of sonar data of the underwater environment is captured. Each sonar return of the raw sonar data may be defined by, at least, a distance and an angle (e.g., 2D), which may be processed (e.g., by the sonar signal processor) to generate 2D sonar data. Further, even though there may be some space within the narrow width of the fan-shaped beam, the 2D sonar returns can be defined to ignore that width and, thus, be assumed to fall within the slice.

In some embodiments, different sets of 2D sonar return data (corresponding to a set of sonar pulses) may build up over time, generating a plurality of sets of slices of 2D sonar data. As detailed above, the sonar transducer assembly may comprise a heading sensor configured to detect the heading of the transducer elements. The detected heading may be associated with sonar returns captured by the transducer elements. Further, the detected heading may be transmitted to the sonar signal processor for aiding in arranging of the sonar images corresponding to each set of captured sonar returns. For example, each set (or slice) of 2D sonar return data may define a corresponding heading. The heading can be used to define the third dimension for creation of the 3D image (wherein the other two dimensions are range and angle of the sonar return).

In some embodiments, the sonar return data from the 2D slice and corresponding heading are saved in memory for processing to form the 3D sonar image data, which may be displayed as a 3D image. In some embodiments, 3D image data representing a 3D image may be stored in a buffer prior to or in conjunction with display on the screen.

In some embodiments, the sonar signal processor may be configured to process a plurality of sets of 2D sonar return data to generate a 3D representation of at least a portion of the underwater environment. In this regard, the plurality of sets of 2D sonar data (built up over time) may be processed together and used to generate the 3D image data. For example, the 3D image data may be produced by combining the points of interferometric return data from each set of 2D sonar data to create a 3D point cloud of individual data points. The 3D point cloud may then be processed (e.g., using the sonar signal processor) to generate a mesh based on the point cloud.

In some embodiments, 2D sonar data may be processed with one or more adjacent sets of 2D sonar data to produce an adjusted set of sonar data. The adjusted set of sonar data may include interpolated connections between the points of 2D sonar data and/or between adjacent sets of 2D sonar data to visualize the underwater environment. The adjusted set of sonar data may represent continuous contours or topographical meshes such that the 3D image data may be formed by connecting the adjusted sets of sonar data with connecting gridlines. For example, the sonar signal processor may be configured to reconstruct the bottom surface of the underwater environment based on the sonar returns that form the 3D point cloud. Further, the reconstructed bottom surface could be used to generate the 3D image data.

In some embodiments, the sonar signal processor may be configured to reconstruct objects within the underwater environment (e.g., fish, trees, submerged watercraft, etc.) and use the generated mesh to generate the 3D image data. Additionally or alternatively, only portions of the underwater environment may be reconstructed (e.g., just the bottom surface, or just the bottom surface and fish, etc.). The remaining raw sonar return data could be used to form the remainder of the 3D image data (e.g., using the raw sonar returns or presenting an icon (e.g., fish icon) in place of or over raw sonar returns that have been determined to correspond to an object represented by the icon). U.S. Patent Application Ser. No. 62/128,641, filed Mar. 5, 2015, entitled “Reconstruction of Underwater Features for 3D Imaging” provides additional detail regarding example systems and methods of reconstructing a 3D Image and is hereby incorporated by reference herein in its entirety.

In some embodiments, each of the sets of 2D sonar data may be used to form the 3D image data. In this regard, each set of 2D sonar data may be displayed on a display in the appropriate direction (using the detected heading) by adding the newest 2D vertical slice (e.g., a theoretical vertical slice) in the appropriate direction (e.g., similar to the description regardingFIGS. 5, 5A, and 6). In this regard, the raw sonar data made up of range and angle may be used to form the 3D image data.

In some embodiments, a combination of the above noted techniques can be used to form the 3D image data. For example, the bottom surface may be reconstructed and used to generate the 3D image data and the objects within the water column may be updated using the raw sonar data with positioning based on the detected heading.

In some embodiments, the 3D image may be displayed in a perspective view such that the contour of the floor of the body of water is visualized in three dimensions. Additionally, in some embodiments, the 3D image may also be turned with the movement of the boat such that the 3D image appears to turn with the watercraft and/or transducer assembly. In this regard, the display may be north up, boat up, transducer assembly up, or a user-defined direction up.

FIG. 12illustrates an example 3D image that may be displayed to a user. The 3D image shows the underwater environment500from a perspective of a viewer to the upper right of the watercraft510. The bottom surface530of the underwater environment may be displayed and individual raw sonar returns540may also be displayed in the water column. A vertical plane520may be shown to indicate the current direction of the transducer assembly (though other icons or indicators may be used). As the transducer assembly rotates, the sonar returns525within the vertical plane520(in the water column, the bottom surface, or both) may be updated. Though the example 3D image shows just a small angle of the underwater environment, all 360° could be shown.

Example Method of Operation

FIG. 13illustrates a flowchart according to an example method for operating a sonar system according to an example embodiment600. Operations that are shown in dashed lines need to necessarily be performed for embodiments of the present invention.

Operation602may comprise transmitting one or more sonar pulses into the underwater environment. The processor32, transceiver34, transmitter circuitry71, and or transducer elements60,62may, for example, provide means for performing operation602. Operation604may comprise receiving sonar returns from the sonar pulses with the first transducer element and converting the sonar returns into first sonar return data. Operation606may comprise receiving sonar returns from the sonar pulses with the second transducer element and converting the sonar returns into second sonar return data. Operation608may comprise transferring the first and second sonar return data to the processor. The transceiver34or receiver circuitry72may, for example, provide means for performing operation608.

Operation620may comprise detecting a heading of the first and/or second sonar return data during capture. The processor32and/or heading sensor69may, for example, provide means for performing operation620. Operation622may comprise generating 2D radar-like sonar image data based on at least one of the first sonar return data or the second sonar return data and the detected heading. The processor32may, for example, provide means for performing operation622. Operation624may comprise displaying the 2D radar-like image of the underwater environment. The processor32, user interface39, or display38may, for example, provide means for performing operation624.

Operation630may comprise generating 2D sonar return data that includes a range and an angle for each sonar return. The processor32may, for example, provide means for performing operation630.

Operation640may comprise detecting a heading of the first and/or second sonar return data during capture. The processor32and/or heading sensor69may, for example, provide means for performing operation640. Operation642may comprise generating 3D sonar image data based on the 2D sonar return data and the detected heading. The processor32may, for example, provide means for performing operation642. Operation644may comprise displaying the 3D image of the underwater environment. The processor32, user interface39, or display38may, for example, provide means for performing operation644.

Operation652may comprise generating 2D forward looking sonar image data based on the 2D sonar return data. The processor32may, for example, provide means for performing operation652. Operation654may comprise displaying the 2D forward looking image of the underwater environment. The processor32, user interface39, or display38may, for example, provide means for performing operation654.

Though the described embodiment ofFIG. 13details operating one example sonar system, some embodiments of the present invention contemplate methods for operating any example sonar system described herein.

Example System Hardware

In some embodiments, referring back toFIGS. 2 and 2A, the transducer assembly36and/or sonar module44may be positioned within a housing. The housing may include a recessed portion defining a containment volume for holding the transducer elements. To prevent cavitation or the production of bubbles due to uneven flow over the housing, the housing (and in particular the containment volume portion of the housing) may have a gradual, rounded or otherwise streamlined profile to permit laminar flow of water over the housing. In some examples, an insulated cable may provide a conduit for wiring (e.g., transmitter circuitry71or receiver circuitry72) to couple each of the transducer elements to the sonar module44. As detailed herein, any of a number of configurations of transducer elements and transducer arrays may be provided within the housing.

The shape of a transducer element may largely determine the type of beam that is formed when that transducer element transmits a sonar pulse (e.g., a circular transducer element emits a cone-shaped beam, a linear/rectangular transducer element emits a fan-shaped beam, etc.). In some embodiments, a transducer element may comprise one or more transducer elements positioned to form one transducer element. For example, a rectangular transducer element may comprise two or more rectangular transducer elements aligned with each other so as to be collinear. In some embodiments, three transducer elements aligned in a collinear fashion (e.g., end to end) may define one rectangular transducer element.

Likewise, transducer elements may comprise different types of materials that cause different sonar pulse properties upon transmission. For example, the type of material may determine the strength of the sonar pulse. Additionally, the type of material may affect the sonar returns received by the transducer element. As such, embodiments of the present invention are not meant to limit the shape or material of the transducer elements.

In some embodiments, each of the transducer elements (e.g., transducer elements60,62shown inFIG. 3and/or transducer elements94,96,98, and100) may be a rectangular transducer element. Thus, for example, each of the transducer elements may be substantially rectangular in shape and made from a piezoelectric material such as a piezoelectric ceramic material, as is well known in the art. In such a regard, the transducer elements may be configured to transmit and/or receive a fan-shaped beam (e.g., 15° by 90°, though any fan-shaped beam is contemplated).

As noted above, any of the transducer elements described herein may be configured to transmit and receive sonar pulses (e.g., transmit/receive transducer elements). While the transducer elements may be described herein as transmit/receive transducer elements, in some embodiments, the transducer elements may be configured as receive-only transducer elements, or in other cases, transmit-only transducer elements.

In some embodiments, each transducer element may be configured to operate at any frequency, including operation over an array of frequencies. Along these lines, it should be understood that many different operating ranges could be provided with corresponding different transducer element sizes and shapes (and corresponding different beamwidth characteristics). Moreover, in some cases, the sonar module44may include a variable frequency selector, to enable an operator to select a particular frequency of choice for the current operating conditions.

The active element in a given transducer may comprise at least one crystal. Wires are soldered to coatings so the crystal can be attached to a cable which transfers the electrical energy from the transmitter to the crystal. As an example, when the frequency of the electrical signal is the same as the mechanical resonant frequency of the crystal, the crystal moves, creating sound waves at that frequency. The shape of the crystal determines both its resonant frequency and shape and angle of the emanated sound beam. Frequencies used by sonar devices vary, but the most common ones range from 50 KHz to over 900 KHz depending on application. Some sonar systems vary the frequency within each sonar pulse using “chirp” technology. These frequencies are in the ultrasonic sound spectrum and are inaudible to humans.

It should be noted that although the widths of various beams are shown and described herein, the widths being referred to do not necessarily correspond to actual edges defining limits to where energy is placed in the water. As such, although beam patterns and projections of beam patterns are generally shown herein as having fixed and typically geometrically shaped and sharply defined boundaries, those boundaries merely correspond to the −3 dB (or half power) points for the transmitted beams. In other words, energy measured outside of the boundaries shown is less than half of the energy transmitted, but this sound energy is present nonetheless. Thus, some of the boundaries shown are merely theoretical half power point boundaries.

In an example embodiment, the sonar signal processor32, the transceiver34and an Ethernet hub42or other network hub may form a sonar module44. As such, for example, in some cases, the transducer assembly36may simply be placed into communication with the sonar module44, which may itself be a mobile device that may be placed (but not necessarily mounted in a fixed arrangement) in the vessel to permit easy installation of one or more displays38, each of which may be remotely located from each other and operable independent of each other. In this regard, for example, the Ethernet hub42may include one or more corresponding interface ports for placing the network40in communication with each display38in a plug-n-play manner. As such, for example, the Ethernet hub42may not only include the hardware needed to enable the displays38to be plugged into communication with the network40via the Ethernet hub42, but the Ethernet hub42may also include or otherwise be in communication with software modules for providing information to enable the sonar module44to communicate with one or more different instances of the display38that may or may not be the same model or type of display and that may display the same or different information. In other words, the sonar module44may store configuration settings defining a predefined set of display types with which the sonar module is compatible so that if any of the predefined set of display types are placed into communication with the sonar module44, the sonar module44may operate in a plug-n-play manner with the corresponding display types. Accordingly, the sonar module44may include a memory storing device driver accessible to the Ethernet hub42to enable the Ethernet hub42to properly work with displays for which the sonar module44is compatible. The sonar module44may also be enabled to be upgraded with additional device drivers or transceivers to enable expansion of the numbers and types of devices with which the sonar module44may be compatible. In some cases, the user may select a display type to check whether a display type is supported and, if the display type is not supported, contact a network entity to request software and/or drivers for enabling support of the corresponding display type.

The sonar signal processor32may be any means such as a device or circuitry operating in accordance with software or otherwise embodied in hardware or a combination of hardware and software (e.g., a processor operating under software control or the processor embodied as an application specific integrated circuit (ASIC) or field programmable gate array (FPGA) specifically configured to perform the operations described herein, or a combination thereof) thereby configuring the device or circuitry to perform the corresponding functions of the sonar signal processor32as described herein. In this regard, the sonar signal processor32may be configured to analyze electrical signals communicated thereto by the transceiver34to provide sonar data indicative of the size, location, shape, etc. of objects detected by the sonar system. For example, the sonar signal processor32may be configured to receive sonar return data and process the sonar return data to generate sonar image data for display to a user (e.g., on display38).

In some cases, the sonar signal processor32may include a processor, a processing element, a coprocessor, a controller or various other processing means or devices including integrated circuits such as, for example, an ASIC, FPGA or hardware accelerator, that is configured to execute various programmed operations or instructions stored in a memory device. The sonar signal processor32may further or alternatively embody multiple compatible additional hardware or hardware and software items to implement signal processing or enhancement features to improve the display characteristics or data or images, collect or process additional data, such as time, temperature, GPS information, waypoint designations, or others, or may filter extraneous data to better analyze the collected data. It may further implement notices and alarms, such as those determined or adjusted by a user, to reflect depth, presence of fish, proximity of other watercraft, etc. Still further, the processor, in combination with a storage module, may store incoming transducer data or screen images for future playback or transfer, or alter images with additional processing to implement zoom or lateral movement, or to correlate data, such as fish or bottom features to a GPS position or temperature. In an exemplary embodiment, the sonar signal processor32may execute commercially available software for controlling the transceiver34and/or transducer assembly36and for processing data received therefrom.

The transceiver34may be any means such as a device or circuitry operating in accordance with software or otherwise embodied in hardware or a combination of hardware and software (e.g., a processor operating under software control or the processor embodied as an ASIC or FPGA specifically configured to perform the operations described herein, or a combination thereof) thereby configuring the device or circuitry to perform the corresponding functions of the transceiver34as described herein. In this regard, for example, the transceiver34may include (or be in communication with) circuitry (e.g., transmitter circuitry71shown inFIG. 2) for providing one or more transmission electrical signals to the transducer assembly36for conversion to sound pressure signals based on the provided electrical signals to be transmitted as a sonar pulse. The transceiver34may also include (or be in communication with) circuitry (e.g., receiver circuitry72) for receiving one or more electrical signals produced by the transducer assembly36responsive to sound pressure signals received at the transducer assembly36based on echo or other return signals received in response to the transmission of a sonar pulse. The transceiver34may be in communication with the sonar signal processor32to both receive instructions regarding the transmission of sonar signals and to provide information on sonar returns to the sonar signal processor32for analysis and ultimately for driving one or more of the displays38based on the sonar returns. In some embodiments, the transmitter circuitry71and/or receiver circuitry72may be positioned within the transceiver34or sonar module44. In other embodiments the transmitter circuitry71and/or receiver circuitry72may be positioned within the transducer assembly36. Likewise, in some embodiments, the transmitter circuitry71and/or receiver circuitry72may be positioned separate from the transducer assembly36and transceiver34/sonar module44.