Patent Grant
9741335
If an Application Data Sheet (ADS) has been filed on the filing date of this application, it is incorporated by reference herein. Any applications claimed on the ADS for priority under 35 U.S.C. §§119, 120, 121, or 365(c), and any and all parent, grandparent, great-grandparent, etc., applications of such applications are also incorporated by reference, including any priority claims made in those applications and any material incorporated by reference, to the extent such subject matter is not inconsistent herewith.
The present application claims the benefit of the earliest available effective filing date(s) from the following listed application(s) (the “Priority Applications”), if any, listed below (e.g., claims earliest available priority dates for other than provisional patent applications or claims benefits under 35 U.S.C. §119(e) for provisional patent applications, for any and all parent, grandparent, great-grandparent, etc., applications of the Priority application(s)). In addition, the present application is related to the “Related applications,” if any, listed below.
NONE
If the listings of applications provided above are inconsistent with the listings provided via an ADS, it is the intent of the Applicant to claim priority to each application that appears in the Priority applications section of the ADS and to each application that appears in the Priority applications section of this application.
All subject matter of the Priority applications and the Related applications and of any and all parent, grandparent, great-grandparent, etc. applications of the Priority applications and the Related applications, including any priority claims, is incorporated herein by reference to the extent such subject matter is not inconsistent herewith.
This disclosure relates to acoustic phased arrays and metamaterial acoustic transducer systems. Specifically, this disclosure relates to sub-wavelength transducers addressable via selective electromagnetic resonance.
The present disclosure includes various systems and methods for generating and receiving acoustic transmissions according to a dynamically selectable acoustic pattern or beam-form. In one embodiment, an acoustic transducer system for ultrasonic imaging includes an array of sub-wavelength ultrasonic transducer elements each configured to generate an ultrasonic acoustic emission within an ultrasonic frequency band between 1 and 15 MHz in response to received electromagnetic energy within an electromagnetic frequency band between 1 GHz and 10 GHz. The system may also include at least one electromagnetically resonant element with an electromagnetic resonance within the electromagnetic frequency band coupled to each of the sub-wavelength ultrasonic transducer elements. The system may further include an electromagnetic transmission module configured to modify one or more characteristics of transmitted electromagnetic energy to effectuate an acoustic emission by the array of sub-wavelength transducer elements according to an acoustic transmission pattern corresponding to the respective electromagnetic resonance characteristics of at least some of the electromagnetically resonant elements coupled to the sub-wavelength ultrasonic transducer elements. In addition, the system may include a common port configured to facilitate electromagnetic communication with each of the electromagnetically resonant elements coupled to the sub-wavelength transducer elements, wherein a physical diameter of each individual sub-wavelength ultrasonic transducer element is less than one-half of an effective wavelength of the highest frequency of the acoustic emissions.
According to the various embodiments described herein, a specific acoustic pattern (e.g., a beam-formed acoustic transmission) is generated by selectively activating individual or groups of sub-wavelength transducer elements in an array of sub-wavelength transducer elements.
For example, an acoustic transducer system may include an array of sub-wavelength transducer elements. Each sub-wavelength transducer element in the array of sub-wavelength transducer elements may be configured to resonate with a particular electromagnetic frequency. The electromagnetic resonance of each sub-wavelength transducer element may cause an acoustic emission. Similarly, the reception of acoustic energy may cause the sub-wavelength transducer element to emit, absorb, and/or modulate electromagnetic energy.
Thus, each sub-wavelength transducer element in the array of sub-wavelength transducer elements may be configured to convert electromagnetic energy to acoustic energy and/or acoustic energy to electromagnetic energy. In some embodiments, each sub-wavelength transducer element is configured to convert energy in both directions. That is, each sub-wavelength transducer elements may be configured to convert electromagnetic energy to acoustic energy and acoustic energy to electromagnetic energy.
In other embodiments, some sub-wavelength transducer elements are configured to convert electromagnetic energy to acoustic energy and other sub-wavelength transducer elements are configured to convert acoustic energy to electromagnetic energy.
In some embodiments, each sub-wavelength transducer element in the array of sub-wavelength transducer elements may be configured to resonate at a different electromagnetic frequency(ies). Accordingly, each sub-wavelength transducer element within the array of sub-wavelength transducer elements may be uniquely addressable via the unique resonant frequency.
In other embodiments, the array of sub-wavelength transducer elements may be divided into sets of sub-wavelength transducer elements, where each set includes one or more sub-wavelength transducer elements. Each set may resonate at a unique frequency, such that each sub-wavelength transducer element in a particular set resonates at the same frequency as other sub-wavelength transducer elements in the particular set, but at a different frequency than sub-wavelength transducer elements in a different set. Thus, a set of sub-wavelength transducer elements may be group-addressable via a single electromagnetic frequency. Multiple sets of sub-wavelength transducer elements may be addressable via multiple corresponding electromagnetic frequencies.
A set of sub-wavelength transducer elements may include any number of sub-wavelength transducer elements that are contiguously located within the array of sub-wavelength transducer elements. Alternatively, a set of sub-wavelength transducer elements may include any number of sub-wavelength transducer elements that are disparately, randomly, stochastically (with respect to other subsets), or strategically located within the array of sub-wavelength transducer elements.
Each respective sub-wavelength transducer element may be configured to generate and/or receive an acoustic signal at a wavelength having a larger wavelength than the diameter and/or depth of the respective sub-wavelength transducer element. As will be appreciated by one of skill in the art, each embodiment or example described in terms of a transmitter may be equally applicable to receiving arrays of sub-wavelength transducer elements. Similarly, each embodiment or example described in terms of a receiver may be equally applicable to transmitting arrays of sub-wavelength transducer elements.
A controller in communication with the array of sub-wavelength transducer elements may be configured to selectively transmit (or receive) electromagnetic energy at the resonant frequency of a select subset of sub-wavelength transducer elements in the array of sub-wavelength transducer elements. The select subset may include one or more uniquely-addressable individual sub-wavelength transducer elements and/or one or more sets of group-addressable sub-wavelength transducer elements.
The controller may be in communication with the array of sub-wavelength transducer elements via a common port. In some embodiments, an electromagnetic transmitter may be configured to communication via a free-space common port; in other embodiments, the common port may be embodied as an antenna or waveguide.
Each sub-wavelength transducer element may be configured with an electromagnetic resonance at one of a plurality of carrier electromagnetic frequencies. Resonance at the carrier frequency may cause an acoustic emission at a modulation frequency associated with the carrier frequency.
Accordingly, each sub-wavelength transducer element or set of sub-wavelength transducer elements may be configured to resonate at unique electromagnetic carrier frequencies and yet emit acoustic energy at the same frequency (by using a common modulation or side band frequency) or varying frequencies (by using unique modulation or side band frequencies). A carrier frequency may be between 2 and 10 (or more) times larger than the modulation frequency. Similarly, side band frequencies may be spaced from the carrier frequency by a percentage of the carrier frequency.
As an example, one or more sub-wavelength transducer elements may be configured with an electromagnetic resonance of 10 MHz, one or more other sub-wavelength transducer elements may be configured with an electromagnetic resonance at 15 MHz, and other sets of one or more sub-wavelength transducer elements at 20 MHz, 25 MHz, and so forth. Each sub-wavelength transducer element may be configured to generate an acoustic emission in response to receiving a resonating electromagnetic signal. The generated acoustic emission may correspond to a fixed acoustic frequency associated with the resonating electromagnetic frequency and/or a modulation frequency associated with the resonating electromagnetic frequency.
For instance, in the example above, a modulation frequency of 30 kHz may be present on each of the electromagnetic signals. According to various embodiments, by selectively transmitting electromagnetic signals at 10 MHz, 15 MHz, 20 MHz, 25 MHz, and so forth, the array of sub-wavelength transducer elements may be selectively controlled to transmit acoustic energy from only those sub-wavelength transducer elements receiving a resonating electromagnetic signal. The transmitted acoustic signal may be at the modulation frequency of 30 kHz. The amplitude and/or phase of each acoustic signal transmitted by each sub-wavelength transducer element may be varied by adjusting the amplitude and/or phase of the modulation frequency. Each respective carrier frequency may be separated a sufficient number of frequency channels to prevent or reduce the likelihood of interference due to modulation and/or side band channels.
The amplitudes and/or phases of one or more carrier frequencies, side band frequencies, and/or modulation frequencies may be modified to dynamically adjust the acoustic transmission transmitted by the collective array of sub-wavelength transducer elements. A specific acoustic transmission pattern may be produced by inducing sub-wavelength transducer elements to generate an acoustic transmission. The specific acoustic transmission may be generated and/or modified by varying one or more characteristic (e.g., phase, amplitude, and/or frequency) of the resonating electromagnetic energy, electromagnetic energy at the resonating carrier frequency, side band of the resonating carrier frequency, and/or modulation frequency(ies) of the resonating carrier frequency.
In various embodiments, the specific acoustic pattern may include a beam-formed acoustic transmission, a pseudo-random acoustic transmission, a focused beam acoustic transmission, a collimated, random pattern acoustic transmission, an audible transmission, and/or an ultrasonic transmission. For example, an ultrasonic transmission may include acoustic transmissions between 20 kHz and 1 GHz. In other embodiments, the acoustic transmission may be between 20 Hz and 20 KHz, or even in the sub-audible range. A single system or variations of the same system may utilize frequencies between 2 Hz and 1 GHz, or higher.
In various embodiments, the electromagnetic energy may be generated by one or more electromagnetic energy sources. One or more controllers or sub-controllers may control the one or more electromagnetic energy sources to cause them to transmit electromagnetic energy via a common port to the array of sub-wavelength transducer elements. For example, in some embodiments a system may include a microwave energy source.
A controller may adjust one or more of the phase and time-of-transmission of the electromagnetic energy based on a time delay or phase delay associated with the position of one or more of the sub-wavelength transducer elements relative to the controller and/or electromagnetic energy source.
The sub-wavelength transducer elements may comprise resonator elements, such as, for example, metamaterial sub-wavelength transducer elements. The sub-wavelength transducer elements may comprise piezoelectric transducers, ferroelectric polymer transducers, acoustically tunable transducer elements, electromagnetically tunable transducer elements, filters, capacitors, nematic liquid crystal, plasmonic metamaterial transducers, tunable active acoustic metamaterial transducers, dynamically controllable circuit elements, inductors, and/or various other components.
The spacing distance between each of the sub-wavelength transducer elements may be less than ½, ⅓, 1/10 of an acoustic wavelength in the surrounding medium, contiguously spaced with shared edges, and/or otherwise spaced within the array of sub-wavelength transducer elements. Furthermore, in some embodiments, the sub-wavelength transducer elements may be evenly spaced and in other embodiments they may be randomly, stochastically, and/or otherwise spaced within the array of sub-wavelength transducer elements.
In some embodiments, the spacing may be specifically chosen based on a desired acoustic transmission possibility. In some embodiments, the sub-wavelength transducer elements comprise a continuous surface of sub-wavelength transducer elements. The array of sub-wavelength transducer elements may comprise one or more impedance matching layers. The sub-wavelength transducer elements may be in the form of a flexible array of sub-wavelength transducer elements.
The array of sub-wavelength transducer elements may comprise a one-dimensional array of sub-wavelength transducer elements, a two-dimensional array of sub-wavelength transducer elements, and/or a three-dimensional array of sub-wavelength transducer elements. The sub-wavelength transducer elements in an array of sub-wavelength transducer elements may or may not be coplanar with one another. For example, an array of sub-wavelength transducer elements may be disposed on a flexible medium allowing the array to be curved and/or conform to a wide variety of surfaces and shapes.
In some embodiments, position detection elements may provide sufficient positional information to a controller to allow the controller to dynamically modify which sub-wavelength transducer elements are activated (caused to resonate) to continually and dynamically produce and/or receive a specific acoustic pattern(s).
Examples of suitable carrier frequencies may include those in the ultrasonic band between 20 kHz and 100 MHz. Modulation frequencies and/or side band frequencies may be based on the carrier frequency and be between 20 kHz and 20 MHz. Suitable carrier frequencies may depend on the desired acoustic (including ultrasonic, sonic, and subsonic) frequencies, and on the configuration of the transducer system. For example, for medical ultrasound, ultrasonic frequencies are typically between 1 and 10 MHz, and carrier frequencies in this case may be between 100 MHz and 10 GHz. Acoustic transducers for sonar applications may operate at acoustic frequencies of 10 kHz-1 MHz, and are comparatively large; suitable carrier frequencies in this case may be 1 MHz to 1 GHz. As provided above, each of the sub-wavelength transducer elements may be configured with an electromagnetic resonance at a unique frequency(ies) and/or pairs or groups of sub-wavelength transducer elements may be configured with similar or identical electromagnetic frequency resonances.
According to various embodiments, an acoustic transducer system may be configured to receive an acoustic signal at a wavelength larger than a physical diameter of each of the sub-wavelength transducer elements and generate a corresponding electromagnetic transmission at one of a plurality of electromagnetic carrier frequencies. In some embodiments, the electromagnetic carrier frequency generated by a sub-wavelength transducer element may become a modulation frequency of a higher carrier frequency transmitted and/or received via the common port.
At least one of the sub-wavelength transducer elements may be configured to generate an electromagnetic transmission at a first carrier frequency and at least one other of the sub-wavelength transducer elements may be configured to generate an electromagnetic transmission at a second, different carrier frequency.
A receiver may be configured to receive the electromagnetic transmission from each of the sub-wavelength transducer elements. In some embodiments, a controller may selectively control from which of the sub-wavelength transducer elements the receiver receives the electromagnetic transmissions, thereby allowing the array of sub-wavelength transducer elements to receive a specific acoustic pattern. Similar to other embodiments, a common port may facilitate electromagnetic communication between the receiver(s) and each of the sub-wavelength transducer elements.
The transmitter, receiver, and/or transceiver systems described above may be utilized in any of a wide variety of manners. In any of a wide variety of embodiments, an acoustic transmission pattern may be emitted by a plurality of sub-wavelength transducer elements. Each sub-wavelength transducer element may be configured with an electromagnetic resonance at one of a plurality of electromagnetic frequencies.
Each of the respective sub-wavelength transducer elements may be configured to generate an acoustic emission in response to the electromagnetic resonance. In some embodiments, the sub-wavelength transducer elements may be (alternatively or additionally) configured to generate an electromagnetic transmission, resonance, and/or interference pattern in response to an acoustic input. For example, in some embodiments, the sub-wavelength transducer elements may cause a reflected and/or refracted electromagnetic energy to be frequency and/or phase modulated.
A transmitter may transmit energy in at least two of the plurality of electromagnetic frequencies that resonates with a subset of the sub-wavelength transducer elements to generate ultrasonic emissions corresponding to the specific acoustic transmission pattern. The electromagnetic energy may be conveyed via a common port to each of the sub-wavelength transducer elements.
Many existing computing devices and infrastructures may be used in combination with the presently described systems and methods. Some of the infrastructure that can be used with embodiments disclosed herein is already available, such as general-purpose computers, computer programming tools and techniques, digital storage media, and communication links. A computing device or controller may include a processor, such as a microprocessor, a microcontroller, logic circuitry, or the like. A processor may include a special purpose processing device, such as application-specific integrated circuits (ASIC), programmable array logic (PAL), programmable logic array (PLA), programmable logic device (PLD), field programmable gate array (FPGA), or other customizable and/or programmable device. The computing device may also include a machine-readable storage device, such as non-volatile memory, static RAM, dynamic RAM, ROM, CD-ROM, disk, tape, magnetic, optical, flash memory, or other machine-readable storage medium. Various aspects of certain embodiments may be implemented using hardware, software, firmware, or a combination thereof.
The embodiments of the disclosure will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The components of the disclosed embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Furthermore, the features, structures, and operations associated with one embodiment may be applicable to or combined with the features, structures, or operations described in conjunction with another embodiment. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of this disclosure.
Thus, the following detailed description of the embodiments of the systems and methods of the disclosure is not intended to limit the scope of the disclosure, as claimed, but is merely representative of possible embodiments. In addition, the steps of a method do not necessarily need to be executed in any specific order, or even sequentially, nor do the steps need to be executed only once. As described above, descriptions and variations described in terms of transmitters are equally applicable to receivers, and vice versa.
In the illustrated embodiment, a controller 110 is in electrical and/or electromagnetic communication with each of the sub-wavelength transducer elements 120. The controller may be in electromagnetic communication via a common port 140. The common port 140 may comprise free space, a resonant cavity, or a wave guide.
The acoustic transducer system 100 may include an array of sub-wavelength transducer elements 120. Each sub-wavelength transducer element 120 in the array of sub-wavelength transducer elements 120 may be configured to resonate with a particular electromagnetic frequency. The electromagnetic resonance of each sub-wavelength transducer element 120 may cause an acoustic emission. Similarly, the reception of acoustic energy may cause each sub-wavelength transducer element 120 to emit electromagnetic energy. The illustrated antennas 130, 131, and 132 may represent the ability of each sub-wavelength transducer element to receive and/or transmit electromagnetic energy in response to transmissions from the controller 110 and/or externally received acoustic energy.
Thus, each sub-wavelength transducer element 120 in the array of sub-wavelength transducer elements 120 may be configured to convert electromagnetic energy to acoustic energy and/or acoustic energy to electromagnetic energy. In some embodiments, each sub-wavelength transducer element 120 is configured to convert energy in both directions. That is, each sub-wavelength transducer element 120 may be configured to convert electromagnetic energy to acoustic energy and acoustic energy to electromagnetic energy.
In other embodiments, some sub-wavelength transducer elements 120 are configured to convert electromagnetic energy to acoustic energy and other sub-wavelength transducer elements 120 are configured to convert acoustic energy to electromagnetic energy.
In some embodiments, each sub-wavelength transducer element 120 in the array of sub-wavelength transducer elements may be configured to resonate at a different frequency. That is, each sub-wavelength transducer element 120 in the array of sub-wavelength transducer elements may be configured to resonate at a different and unique frequency. Accordingly, each sub-wavelength transducer element 120 within the array of sub-wavelength transducer elements may be uniquely addressable via a unique resonant frequency.
In other embodiments, the array of sub-wavelength transducer elements 120 may be divided into sets of sub-wavelength transducer elements, where each set includes one or more sub-wavelength transducer elements. For example, a first set may include all sub-wavelength transducer elements that resonate at a first electromagnetic frequency (represented by antennas 130). A second set may include all sub-wavelength transducer elements that resonate at a second electromagnetic frequency (represented by antennas 131). A third set may include all sub-wavelength transducer elements that resonate at a third electromagnetic frequency (represented by antennas 132). In other embodiments, any number of sets, each configured to resonate at a unique electromagnetic frequency, may be part of the array of sub-wavelength transducer elements 120. Communication with each of the antennas 130, 131, and 132 may be facilitated by a common port 140. A reflecting or non-reflecting plate 150 may cooperate with the common port 140. For instance, in some embodiments, the common port 140, in conjunction with the reflecting or non-reflecting plate 150, may be a waveguide.
As described above, each set may resonate at a unique frequency, such that each sub-wavelength transducer element 120 in a particular set (those associated with antennas 103, 131, or 132) resonates at the same frequency as other sub-wavelength transducer elements 120 in the same set, but at a different frequency than sub-wavelength transducer elements 120 in a different set. Thus, a set of sub-wavelength transducer elements 120 may be group-addressable via a single electromagnetic frequency. Multiple sets of sub-wavelength transducer elements 120 may be addressable via multiple corresponding electromagnetic frequencies.
As will be appreciated by one of skill in the art, each embodiment or example described in terms of a transmitter may be equally applicable to receiving arrays of sub-wavelength transducer elements 120. Similarly, each embodiment or example described in terms of a receiver may be equally applicable to transmitting arrays of sub-wavelength transducer elements 120.
For instance, in some embodiments, each column may resonate at a unique electromagnetic frequency. In such an embodiment, a controller 110 may be able to individually drive each column by transmitting a unique electromagnetic frequency. For example, sub-wavelength transducer elements in column A may be configured to resonate at 1 MHz, sub-wavelength transducer elements in column B may be configured to resonate at 2 MHz, sub-wavelength transducer elements in column C may be configured to resonate at 3 MHz, and so on until sub-wavelength transducer elements in column K are configured to resonate at 11 MHz. The separation between resonant frequencies of each column may be greater than or less than the example above of 1 MHz. Moreover, the resonant frequencies may be orders of magnitude higher or lower than the MHz range.
In such an embodiment, the controller 110 may transmit electromagnetic energy at 3 MHz to cause each of the sub-wavelength transducer elements in column C to generate an acoustic emission at a frequency Fa, where Fa is any acoustic frequency ranging from audible to extreme ultrasonic. The controller 110 may simultaneously and/or successively transmit electromagnetic energy at various other frequencies to cause the sub-wavelength transducer elements in the other columns to generate an acoustic emission at a frequency Fa. In some embodiments, selective modulation, frequency shifting, phase shifting, and/or other variation on each of the transmitted electromagnetic energy frequencies may cause the sub-wavelength transducer elements to generate an acoustic emission at a frequency Fa+K, KFa, Fak, where K is associated with the modulation, frequency shifting, phase shifting or other variation on each of the transmitted electromagnetic energy.
By controlling which sub-wavelength transducer elements generate an acoustic emission and when, the controller 110 can control the constructive and destructive interference of acoustic emissions from the acoustic transducer system 100. Specifically, the controller 110 may allow the acoustic transducer system to generate a specific acoustic transmission pattern. Similarly, the controller may selectively “listen” (whether actively or passively) to each set of sub-wavelength transducer elements to receive an acoustic signal from a particular direction.
In other embodiments, any combination of sub-wavelength transducer elements may be grouped in a set. For example, a set of sub-wavelength transducer elements may include sub-wavelength transducer elements listed by column and row as follows: A1, B2, C3, D1, E2, F3. Alternatively, they may be grouped in any other conceivable arrangement.
As in other embodiments described herein, each embodiment or example described in terms of a transmitter may be equally applicable to receiving arrays of sub-wavelength transducer elements 120. Similarly, each embodiment or example described in terms of a receiver may be equally applicable to transmitting arrays of sub-wavelength transducer elements 120.
A controller module 210 may include a controller 211, a transmitter 212, and/or a receiver 213 in communication with the array of sub-wavelength transducer elements 220 via a common port 240. The controller module 210 and its components, such as the controller 211, may be implemented in software, firmware, and/or hardware. The controller 211 may drive the transmitter 212 to transmit electromagnetic energy via the common port to the array of sub-wavelength transducer elements 220. The controller 211 may cause the transmitter 212 to transmit specific frequencies to drive one or more sets of sub-wavelength transducer elements 221-224 to cause them to generate an acoustic emission. By selectively driving a different set or sets of sub-wavelength transducer elements at discrete intervals of time, any of a wide variety of acoustic transmission patterns may be realized. Each set of sub-wavelength transducer elements may include one or more sub-wavelength transducer elements.
In some embodiments, the controller 211 may cause the receiver 213 to receive electromagnetic energy from a different set or sets of sub-wavelength transducer elements at discrete intervals of time. Each set of sub-wavelength transducer elements may transmit electromagnetic energy to the receiver based on converted acoustic energy received by the sub-wavelength transducer element. In some embodiments, the receiver may be configured to actively listen to each sub-wavelength transducer element. In such an embodiment, each sub-wavelength transducer element may modify electromagnetic energy that is ultimately received by the receiver 213.
In various embodiments, sub-wavelength transducer elements may draw energy from the electromagnetic transmission. In other embodiments, the sub-wavelength transducer elements may be powered by a separate and/or independent source. The separate and/or independent power source may be controlled by the electromagnetic transmissions and/or via a separate or joint control unit.
The determined and/or selected 515 electromagnetic frequencies may be chosen for discrete time periods and/or time intervals to generate the specific acoustic pattern. The controller may cause a transmitter and/or receiver to transmit and/or receive 520 electromagnetic energy at the selected electromagnetic frequencies and times. The electromagnetic energy may then be conveyed 525 via a common port connecting the transmitter(s) and/or receiver(s) and the sub-wavelength transducer elements.
This disclosure has been made with reference to various exemplary embodiments, including the best mode. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of the present disclosure. While the principles of this disclosure have been shown in various embodiments, many modifications of structure, arrangements, proportions, elements, materials, and components may be adapted for a specific environment and/or operating requirements without departing from the principles and scope of this disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure.
This disclosure is to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope thereof. Likewise, benefits, other advantages, and solutions to problems have been described above with regard to various embodiments. However, benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element. The scope of the present invention should, therefore, be determined by the following claims.
| Number | Name | Date | Kind |
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| 20140098979 | Osborn | Apr 2014 | A1 |
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| Number | Date | Country | |
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| 20150334487 A1 | Nov 2015 | US |
