阅读说明：本技术 非视域追踪系统 (Non-visual field tracking system ) 是由 徐飞虎 黎正平 吴骋 潘建伟 于 2020-12-23 设计创作，主要内容包括：本公开提供了一种非视域追踪系统,包括：信号源,用于产生触发信号；光学收发板,包括光学金属基板、光学发射模块和光学接收模块,其中,光学金属基板用于固定光学发射模块和光学接收模块,光学发射模块用于向中介物体发射激光信号,光学接收模块用于接收中介物体返回的漫反射激光信号,漫反射激光信号是由处于非视域的目标对象经过漫反射得到的信号；脉冲激光器,与光学发射模块连接,用于接收触发信号,并响应触发信号将激光信号传输至光学发射模块；单光子探测器,与光学接收模块连接,用于接收光学接收模块传输的漫反射激光信号,并产生探测信号传输给时间数字转换器；以及时间数字转换器,用于接收触发信号和探测信号,并记录时间信息。(The present disclosure provides a non-vision field tracking system comprising: a signal source for generating a trigger signal; the optical transceiver board comprises an optical metal substrate, an optical transmitting module and an optical receiving module, wherein the optical metal substrate is used for fixing the optical transmitting module and the optical receiving module, the optical transmitting module is used for transmitting laser signals to the intermediary object, the optical receiving module is used for receiving diffuse reflection laser signals returned by the intermediary object, and the diffuse reflection laser signals are signals obtained by diffuse reflection of a target object in a non-visual field; the pulse laser is connected with the optical transmitting module and used for receiving the trigger signal and transmitting the laser signal to the optical transmitting module in response to the trigger signal; the single-photon detector is connected with the optical receiving module and used for receiving the diffuse reflection laser signals transmitted by the optical receiving module, generating detection signals and transmitting the detection signals to the time-to-digital converter; and the time-to-digital converter is used for receiving the trigger signal and the detection signal and recording time information.)

1. A non-field-of-view tracking system, comprising:

a signal source for generating a trigger signal;

the optical transceiver board comprises an optical metal substrate, an optical transmitting module and an optical receiving module, wherein the optical metal substrate is used for fixing the optical transmitting module and the optical receiving module, the optical transmitting module is used for transmitting a laser signal to an intermediary object, the optical receiving module is used for receiving a diffuse reflection laser signal returned by the intermediary object, and the diffuse reflection laser signal is a signal obtained by diffuse reflection of a target object in a non-visual field;

the pulse laser is connected with the optical emission module and used for receiving the trigger signal and responding to the trigger signal to transmit a laser signal to the optical emission module;

the single-photon detector is connected with the optical receiving module and used for receiving the diffuse reflection laser signals transmitted by the optical receiving module, generating detection signals and transmitting the detection signals to the time-to-digital converter; and

and the time-to-digital converter is used for receiving the trigger signal and the detection signal and recording time information.

2. The non-view tracking system of claim 1, wherein the signal source, the optical transceiver panel, the pulsed laser, the single photon detector, and the time-to-digital converter are integrated in a chassis.

3. The non-vision tracking system of claim 2, wherein the chassis is mounted on a bracket with pulleys.

4. The non-vision field tracking system of claim 1, wherein the optical transceiver board comprises at least two-way optical receiving modules.

5. The non-view tracking system of claim 4, wherein each of the optical receive modules comprises: the optical coupling module and the optical filtering module.

6. The non-vision field tracking system of claim 1, the optical transceiver board further comprising a pointing adjustment mechanism, wherein the pointing adjustment mechanism is connected to the optical metal substrate and the optical transmitter module and the optical receiver module respectively for adjusting the transmitting direction of the optical transmitter module and the receiving direction of the optical receiver module.

7. The non-view tracking system of claim 1, wherein the pulsed laser comprises: a near infrared pulse laser.

8. The non-vision field tracking system of claim 1, wherein the signal source and the time-to-digital converter are integrated on the same circuit board.

9. The non-vision field tracking system of claim 1, wherein the single photon detector comprises: at least two-channel single photon detector.

10. The non-vision field tracking system of claim 1, further comprising:

and the information processing device is used for receiving the time information of the time-to-digital converter and calculating the position information of the target object according to the time information and the focal position information of the intermediary object.

Technical Field

The present disclosure relates to the field of lidar, and more particularly, to a non-vision field tracking system.

Background

The Non-line-of-sight (NLOS) field is mainly studied on how to effectively acquire information about objects and scenes hidden from view, and more particularly, how to locate, track, and image objects hidden from view.

In 2009, researchers from the Massachusetts institute of technology media laboratory first proposed the concept of non-visual field at the international computer vision conference of the year and initially demonstrated the possibility of capturing objects outside the visual field.

In the prior art, for example, gaierpy et al uses a 32x32 pixel visible light single photon detection (SPAD) array to realize a set of non-visual field positioning and tracking system with a working waveband of about 800nm, however, the SPAD array of 32x32 pixels can acquire a large amount of redundant information, bring certain pressure to post-processing of data and hardware adopted, and are not beneficial to further integration and real-time; and as Chan et al use three single-point SPADs to build a set of non-vision field positioning system, but because the system is mainly oriented to a non-vision field scene in a long distance, the system is provided with heavy devices such as a large telescope, and the like, and has a huge overall structure and no portability, and meanwhile, the system needs to perform signal collection by point-by-point scanning and has no real-time tracking function.

Therefore, in the process of implementing the present invention, it is found that the non-visual field localization and tracking system in the related art has a large overall structure, is not portable, and is difficult to implement real-time tracking well.

Disclosure of Invention

In view of the above, the present disclosure provides a non-field-of-view tracking system.

According to an embodiment of the present disclosure, a non-field-of-view tracking system includes: a signal source for generating a trigger signal; an optical transceiver board, comprising an optical metal substrate, an optical transmitting module and an optical receiving module, wherein the optical metal substrate is used for fixing the optical transmitting module and the optical receiving module, the optical transmitting module is used for transmitting a laser signal to an intermediary object, the optical receiving module is used for receiving a diffuse reflection laser signal returned by the intermediary object, and the diffuse reflection laser signal is a signal obtained by diffuse reflection of a target object in a non-visual field; the pulse laser is connected with the optical emission module and used for receiving the trigger signal and transmitting a laser signal to the optical emission module in response to the trigger signal; the single-photon detector is connected with the optical receiving module and used for receiving the diffuse reflection laser signals transmitted by the optical receiving module and generating detection signals to transmit to the time-to-digital converter; and the time-to-digital converter is used for receiving the trigger signal and the detection signal and recording time information.

According to the embodiment of the present disclosure, the signal source, the optical transceiver board, the pulse laser, the single-photon detector, and the time-to-digital converter are integrated in a chassis.

According to the embodiment of the disclosure, the chassis is mounted on a bracket with pulleys.

According to the embodiment of the present disclosure, the optical transceiver board includes at least two optical receiving modules.

According to an embodiment of the present disclosure, each of the optical receiving modules includes: the optical coupling module and the optical filtering module.

According to an embodiment of the present disclosure, the optical transceiver board further includes a direction adjustment mechanism, wherein the direction adjustment mechanism is connected to the optical metal substrate, the optical transmitter module and the optical receiver module, respectively, and is configured to adjust a transmitting direction of the optical transmitter module and a receiving direction of the optical receiver module.

According to an embodiment of the present disclosure, the above pulse laser includes: a near infrared pulse laser.

According to the embodiment of the disclosure, the signal source and the time-to-digital converter are integrated on the same circuit board.

According to an embodiment of the present disclosure, the single photon detector includes: at least two-channel single photon detector.

According to an embodiment of the present disclosure, the non-field-of-view tracking system further comprises: and an information processing device for receiving the time information of the time-to-digital converter and calculating the position information of the target object according to the time information and the focal position information of the intermediary object.

According to the embodiment of the disclosure, because a small-sized optical device is used and a reasonable structural design is adopted, the problems of large volume and complex structure of the non-visual field tracking system are at least partially overcome, and the effects of integration and practicability are further achieved.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

FIG. 1 schematically illustrates a typical non-field-of-view tracking scene schematic;

FIG. 2 schematically illustrates a non-field-of-view tracking system according to the present disclosure;

FIG. 3 schematically illustrates a schematic diagram of an integrated non-field-of-view tracking system according to an embodiment of the disclosure;

FIG. 4 schematically illustrates a schematic diagram of a non-vision tracking system for localization tracking of a scene according to an embodiment of the present disclosure;

FIG. 5 schematically illustrates a schematic diagram of a prototype system of a non-vision tracking system according to another embodiment of the disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

Where a convention analogous to "at least one of A, B and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B and C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.). Where a convention analogous to "A, B or at least one of C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B or C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.).

Embodiments of the present disclosure provide a non-vision field tracking system, comprising: a signal source for generating a trigger signal; the optical transceiver board comprises an optical metal substrate, an optical transmitting module and an optical receiving module, wherein the optical metal substrate is used for fixing the optical transmitting module and the optical receiving module, the optical transmitting module is used for transmitting laser signals to the intermediary object, the optical receiving module is used for receiving diffuse reflection laser signals returned by the intermediary object, and the diffuse reflection laser signals are signals obtained by diffuse reflection of a target object in a non-visual field; the pulse laser is connected with the optical transmitting module and used for receiving the trigger signal and transmitting the laser signal to the optical transmitting module in response to the trigger signal; the single-photon detector is connected with the optical receiving module and used for receiving the diffuse reflection laser signals transmitted by the optical receiving module, generating detection signals and transmitting the detection signals to the time-to-digital converter; and the time-to-digital converter is used for receiving the trigger signal and the detection signal and recording time information.

Fig. 1 schematically illustrates a typical non-field-of-view tracking scene schematic.

As shown in fig. 1, the application scenario includes an intermediary object 101, a target object 102, an obstacle 103, and a tracking system 104, wherein the tracking system 104 includes a transmitting end 1041 and a receiving end 1042. Due to the shielding of the obstacle 103, the ordinary positioning and tracking system cannot directly perform positioning and tracking on the target object 102 and cannot directly acquire the specific coordinate information r thereof₀(x₀，y₀，z₀). Based on the application scenario, the following method is adopted in the embodiment of the disclosure:

first, the emitting end 1041 of the tracking system 104 emits a laser signal to irradiate a point r on the medium object 101_l(x_l，y_l,0). The intervening objects may include various objects having a planar structure, such as walls, metal plates, and the like. It should be noted that the intervening object provided in the embodiments of the present disclosure is not limited to this, and may also include an object having a non-planar structure.

Thereafter, the laser pulse is diffusely reflected at that point and propagates to the target object 102; on the surface of the target object 102, the laser light is diffusely reflected for the second time and propagates to a certain point r on the intervening object 101_i(x_i，y_iAnd 0).

Finally, the photons carrying the object information are at this point r_iWhere a third diffuse reflection occurs and is received by the probe tip 1042 of the tracking system 104.

For each photon carrying hidden object information, the detecting end 1042 will record the time of flight t from emission to reception of the photon_iThe following equation is derived for distance:

R₀+R₁+R₂+R₃＝t_ix c (one)

Point r on the intermediary object_lAnd r_iThe coordinates of the laser signal can be obtained by calculation according to the angle information of the laser signal, or obtained by calibration through auxiliary equipment by using methods such as laser ranging and the like, and the methods belong to methods well known by persons skilled in the art and are not described in detail. The above equation can be modified to obtain the following equation:

R₁+R₂＝t_i×c-R₀-R₃(II)

Thus, the target object 102 can be known to be located at r_l、r_iIs a focal point, R₁+R₂Is an ellipsoid of the major axis.

According to the Euclidean geometrical relationship in the three-dimensional space, at least 3 intersected surfaces are needed for determining one three-dimensional point in the space, so that 3 groups of laser points r are passed_lAnd r_iAnd corresponding photon time of flight t_iThe coordinate position of the target object 102 can be obtained by finding the intersecting area of the 3 ellipsoids.

FIG. 2 schematically illustrates a schematic diagram of a non-field-of-view tracking system according to an embodiment of the disclosure.

As shown in fig. 2, the non-field-of-view tracking system includes a signal source 201, an optical transceiver board 202, a pulsed laser 203, a single photon detector 204, and a time-to-digital converter 205.

The signal source 201 is used for generating a trigger signal, and the signal source 201 may be any device that can generate a stable and controllable signal, such as, but not limited to, a function signal generator, etc.

The optical transceiver board 202 includes an optical metal substrate 2021, an optical transmitter module 2022, and an optical receiver module 2023, where the optical metal substrate 2021 is used to fix the optical transmitter module 2022 and the optical receiver module 2023, the optical transmitter module 2022 is used to transmit a laser signal to the intermediary object 101, and the optical receiver module 2023 is used to receive a diffuse reflection laser signal returned by the intermediary object 101, where the diffuse reflection laser signal is a signal obtained by the target object 102 in a non-visual field through diffuse reflection. The optical transmitting module 2022 and the optical receiving module 2023 are formed by devices having a function of coupling and collimating light beams, such as a collimator, a lens set, and the like. The optical signals between the optical transmitter module 2022 and the pulse laser 203 and between the optical receiver module 2023 and the single photon detector 204 are transmitted by a medium with good optical conduction characteristics, such as, but not limited to, an optical fiber.

And the pulse laser 203 is connected with the optical transmitting module 2022 and is used for receiving the trigger signal and transmitting the laser signal to the optical transmitting module 2022 in response to the trigger signal. The pulse laser 203 may be a laser generator of any operating wavelength band, including near infrared laser pulsers and the like.

And the single-photon detector 204 is connected with the optical receiving module 2023, and is configured to receive the diffusely-reflected laser signal transmitted by the optical receiving module 2023, generate a detection signal, and transmit the detection signal to the time-to-digital converter 205. The single photon pulser 204 is a highly sensitive device operating in the wavelength band of the pulsed laser 203, such as an InGaAs single photon avalanche diode.

And the time-to-digital converter 205 is used for receiving the trigger signal and the detection signal and recording time information.

According to the embodiment of the disclosure, because a small-sized optical device is used and a reasonable structural design is adopted, the problems of large volume and complex structure of the non-visual field tracking system are at least partially overcome, and the effects of integration and practicability are further achieved.

FIG. 3 schematically illustrates a schematic diagram of an integrated non-field-of-view tracking system according to an embodiment of the disclosure.

As shown in fig. 3, according to the integrated non-visual field tracking system of the embodiment of the present disclosure, the time control and measurement circuit board 301 integrates the functions of the signal source 201 and the time-to-digital converter 205. The time control and measurement circuit board 301 may be any circuit having signal generation, signal acquisition and data storage functions, or other programmable circuits, such as, but not limited to, FPGAs, etc. The circuit board 301 is in signal interaction with the pulse laser 203 and the single photon detector 204 through printed circuit board lines, wires or electric connectors.

According to the integrated non-visual field tracking system of the embodiment of the present disclosure, the time control and measurement circuit board 301, the optical transceiver board 202, the pulse laser 203 and the single photon detector 204 are integrated in the chassis 300. The optical transceiver board 202 is a panel of the chassis 300.

In accordance with the integrated non-visual tracking system of the disclosed embodiment, the housing 300 can be mounted on a rack with pulleys to facilitate movement and maintain optical stability during actual use.

According to the integrated non-visual field tracking system of the embodiment of the present disclosure, the optical transceiver board 202 includes at least two optical receiving modules 2023, and the single photon detector 204 is at least two-channel single photon detector 204. The at least two optical receiving modules 2023 can simultaneously receive the diffusely-reflected laser signals reflected from at least two different positions on the intervening object 101, and the at least two single-photon detectors 204 can simultaneously respond to the at least two diffusely-reflected laser signals. According to the european geometry principle, the non-visual field tracking system of the present disclosure can obtain two-dimensional or three-dimensional coordinate information of the target object 102 in one transmission-reception-processing operation.

According to the integrated non-visual field tracking system of the embodiment of the present disclosure, the optical receiving module 2023 includes an optical coupling module and an optical filtering module, wherein the optical coupling module is configured to receive a laser signal and couple the laser signal into a light guide medium, and the optical filtering module is configured to filter the received laser signal in a specific wavelength range.

According to the integrated non-visual field tracking system of the embodiment of the present disclosure, the optical transceiver board 202 further includes a pointing adjustment mechanism 302, wherein the pointing adjustment mechanism 302 is connected to the optical metal substrate 2021, the optical transmitter module 2022, and the optical receiver module 2023, respectively, for adjusting the transmitting direction of the optical transmitter module 2021 and the receiving direction of the optical receiver module 2023. For example, when the position of the laser point on the intermediary object 101 is preset, the optical emission module 2022 may be driven to point to the preset position of the laser point by adjusting the pointing adjustment mechanism 302; alternatively, the optical receiving module 2023 may receive the diffuse reflection laser signal reflected by the point on the designated intermediary object 101 by adjusting the pointing adjustment mechanism 302.

FIG. 4 schematically illustrates a schematic diagram of a non-field-of-view tracking system for localization tracking a scene according to an embodiment of the disclosure.

As shown in fig. 4, the non-visual field tracking system according to the embodiment of the present disclosure further includes an information processing device 401 configured to receive the time information of the time-to-digital converter 205 and calculate the position information of the target object 102 according to the time information and the position information of the laser spot on the broker object 101. The information processing apparatus 401 is an electronic device having functions of information reception, information processing, information storage, and information output, and includes, for example, but is not limited to, a computer, a single chip microcomputer, and the like.

FIG. 5 schematically illustrates a schematic diagram of a prototype system of a non-vision tracking system according to another embodiment of the disclosure.

As shown in fig. 5, the emitting portion of a prototype system according to another embodiment of the disclosure includes a pulsed laser 203 and a collimator 501. The pulse laser 203 emits a laser signal in response to a trigger signal transmitted from the FPGA504, transmits the laser signal to the collimator 501 on the optical transceiver board 202 through the optical fiber, and emits the laser signal to the intermediary object 101 by adjusting the angle of the collimator 501 by the pointing adjustment mechanism 302. The trigger signal of the laser is synchronously input to a timing module in the FPGA504 as a start timing signal.

According to another embodiment of the prototype system of the present disclosure, the pulse laser 203 may be 1550nm pulse laser with a pulse width of 500ps, or may be replaced by a narrow pulse width subnanosecond, picosecond, or femtosecond pulse laser in a near-infrared band. The near infrared band belongs to the invisible light band, and compared with the visible light band, the near infrared band has higher human eye safety and cannot be perceived by a reconnaissance target in practical application. The pulse width of the pulse laser is the sum of the time required for the number of photons to rise from a half maximum value to a peak value and the time required for the number of photons to fall from the peak value to the half maximum value, and the narrower the pulse width is, the higher the accuracy of time measurement is, so that the positioning accuracy is improved.

In a prototype system according to another embodiment of the disclosure, collimator 501 includes a collimating head and an optical fiber, and a combination of a convex lens group plus an optical fiber may be used instead.

According to the prototype system of another embodiment of the present disclosure, the optical fiber can be 62.5um core diameter multimode optical fiber to ensure higher collection efficiency and improve the stability of the system.

According to the prototype system of another embodiment of the present disclosure, the FPGA504 can integrate the functions of the signal source 201 and the time-to-digital converter 205, and can also be implemented by other electronic designs.

The receiver portion of the prototype system of another embodiment of the present disclosure includes 3 collimators 502, 3 filters 503, and single photon detectors 204. The 3 collimators 502 can be aligned to three different detection points on the medium object 101 by the adjustment angle of the pointing adjustment mechanism 302, respectively, to receive the photons after three diffuse reflections. The emitted laser signals are collected by the 3 collimators 502 after three times of diffuse reflection, and are respectively coupled into collection optical fibers after being subjected to spectral filtering by the 3 filters 503, and are respectively transmitted into the single photon detector 204 by the optical fibers. The detector transmits the detection signal of each channel to a timing module integrated in the FPGA504 as a timing end signal, measures the flight time of the photon, and transmits the data of the information related to the flight time of the photon to the computer 505.

In the prototype system according to another embodiment of the present disclosure, the coordinates of the probe point on the intermediate object 101 can be obtained by simple calculation of the geometric relationship by combining the angle between the transmission part and the reception part with the time of flight of photons, and the position of the object to be tracked can be obtained by calculation with the computer upper computer software.

According to another prototype system of the present disclosure, the filter 503 may be a 1550nm narrowband filter or an optical fiber filter. The passband of the narrow-band filter is relatively narrow, and is generally less than 5% of the central wavelength value, for example, the 1550nm narrow-band filter generally only allows optical signals within the wavelength range of 1472.5-1627.5 nm to pass through, and it filters noise interference except the wavelength range, including but not limited to visible light noise, ultraviolet light noise, and the like, thereby realizing the practical requirement of the system working all day long.

According to another embodiment of the prototype system disclosed herein, the single photon detector 204 may be a three-channel integrated near-infrared single photon detector, or may be three small single-channel detectors, or other near-infrared single photon detectors with a temporal jitter of less than 1 ns.

According to another embodiment of the prototype system of the present disclosure, the substrate of the optical transceiver board 202 may be a thick plate of high strength aluminum alloy, and the collimator 501 of the transmitting part, the 3 sets of collimators 502 of the receiving part, and the filter 503 are fixed on the substrate by the adjusting frame.

In accordance with a prototype system according to another embodiment of the disclosure, both the transmitter and receiver portions of the system may be integrated into a chassis. For example, in another embodiment of the present disclosure, the volume of the metal chassis is only 287mm × 215mm × 93.5mm, wherein the optical transceiver board 202 is vertically installed at the front end of the prototype system and serves as a side panel of the metal chassis; the collimators 501 and 502, the filter 503 and the pointing adjustment mechanism 302 on the optical transceiver board 202 are closely arranged in an area of 100mm × 100 mm; the pulse laser 203 and the single photon detector 204 both adopt miniaturized optical devices, can be installed in a space of 250mm multiplied by 150mm multiplied by 50mm, are close to each other in space, and are connected with an optical transceiver board through optical fibers; the back end of the prototype system is an FPGA504 circuit board which is only 250mm multiplied by 200mm multiplied by 20mm and is arranged on the other side panel of the metal chassis.

Through the prototype system of the non-visual field tracking system of another embodiment of the present disclosure, a high degree of integration and miniaturization of the system are achieved, wherein integration includes integration of a signal source module, a time-to-digital converter, a three-channel single photon detector, and a pulse laser, and compact electronic connection can be achieved. The vertical optical transceiver board design is adopted, and the optical transmitting and the three-way optical receiving provide stable and compact installation and fixation. The optical transmission adopts an optical fiber transmission mode, and the requirements on stability and integration are met. The small optical device is adopted to replace large equipment such as a telescope system in the prior art, and the portable optical device has the advantages of small size, portability and the like and has practicability. According to the embodiment of the disclosure, a set of practical non-visual field tracking system is provided, which can simultaneously take into account the actual requirements of all-time working, real-time performance, portability and the like. The embodiment of the disclosure is designed and built for various requirements in practical application, and the system has the capability of real-time positioning and tracking under the ordinary sunlight environment, is simple in structure, small and portable.

The embodiments of the present disclosure have been described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the embodiments are described separately above, this does not mean that the measures in the embodiments cannot be used in advantageous combination. The scope of the disclosure is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the present disclosure, and such alternatives and modifications are intended to be within the scope of the present disclosure.