The present disclosure relates generally computer vision systems and relates more particularly to sensors for measuring the distance between a vehicle and an object or point in space.
Unmanned vehicles, such as robotic vehicles and drones, typically rely on computer vision systems for obstacle detection and navigation in the surrounding environment. These computer vision systems, in turn, typically rely on various sensors that acquire visual data from the surrounding environment, which the computer vision systems process in order to gather information about the surrounding environment. For instance, data acquired via one or more imaging sensors may be used to determine the distance from the vehicle to a particular object or point in the surrounding environment.
In one embodiment, a method for calculating a distance to an object includes projecting a plurality of projection beams from each of a plurality of projection points, wherein the plurality of projection points is arranged around a lens of an image capturing device, and wherein at least two beams of the plurality of projection beams are parallel to each other, capturing an image of the field of view, wherein the object is visible in the image and a projection pattern generated by the at least two beams of the plurality of projection beams is also visible in the image, and calculating the distance to the object using information in the image.
In another embodiment, a computer-readable storage device stores a plurality of instructions which, when executed by a processor, cause the processor to perform operations for calculating a distance to an object. The operations include projecting a plurality of projection beams from each of a plurality of projection points, wherein the plurality of projection points is arranged around a lens of an image capturing device, and wherein at least two beams of the plurality of projection beams are parallel to each other, capturing an image of the field of view, wherein the object is visible in the image and a projection pattern generated by the at least two beams of the plurality of projection beams is also visible in the image, and calculating the distance to the object using information in the image.
In another embodiment, a method for calculating a distance to an object includes projecting a plurality of projection beams from each of a plurality of projection points, wherein the plurality of projection points is arranged around a lens of an image capturing device, and wherein at least one beam of the plurality of projection beams is offset by a first angle relative to a line extending radially outward from an axis passing through a center of the lens, capturing an image of the field of view, wherein the object is visible in the image and a projection pattern generated by the at least one beam of the plurality of projection beams is also visible in the image, and calculating the distance to the object using information in the image.
The teaching of the present disclosure can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
In one embodiment, the present disclosure relates to a distance sensor. Distance sensors may be used in unmanned vehicles in order to help a computer vision system determine the distance from the vehicle to a particular object or point in the surrounding environment. For instance, a distance sensor may project one or more beams of light onto the object or point and then compute the distance according to time of flight (TOF), analysis of the reflected light (e.g., lidar), or other means. Conventional distance sensors of this type tend to be bulky, however, and thus may not be suitable for use in compact vehicles. Moreover, the sensors can be very expensive to manufacture and tend to have a limited field of view. For instance, even using an arrangement of multiple conventional imaging sensors provides a field of view that is less than 360 degrees.
Embodiments of the disclosure provide optical configuration refinements for a compact distance sensor, such as any of the distance sensors disclosed in U.S. patent application Ser. No. 14/920,246, filed Oct. 22, 2015. For instance,
As illustrated in
The components are arranged substantially symmetrically about a central axis A-A′. In one embodiment, the central axis A-A′ coincides with the optical axis of the imaging sensor 110. In one embodiment, the light source 104 is positioned at a first end of the central axis A-A′. In one embodiment, the light source 104 is a laser light source that emits a single beam of light along the central axis A-A′. Hereinafter, the single beam emitted by the light source 104 may also be referred to as the “primary beam.” In one embodiment, the light source 104 emits light of a wavelength that is known to be relatively safe to human vision (e.g., infrared). In a further embodiment, the light source 104 may include circuitry to adjust the intensity of its output. In a further embodiment, the light source 104 may emit light in pulses, so as to mitigate the effects of ambient light on image capture.
The first diffractive optical element (DOE) 106 is positioned along the central axis A-A′ in proximity to the light source 104 (e.g., “in front” of the light source 104, relative to the direction in which light emitted by the light source 104 propagates). In particular, the first DOE 106 is positioned to intercept the single beam of light emitted by the light source 104 and to split the single or primary beam into a plurality of secondary beams. In one embodiment, the angles between the central axis A-A′ and each of the secondary beams are equal. The first DOE 106 is any optical component that is capable of splitting the primary beam into a plurality of secondary beams that diverge from the primary beam in different directions. For example, in one embodiment, the first DOE 106 may include a conical mirror or holographic film. In this case, the plurality of secondary beams are arranged in a cone shape. In further embodiments, the primary beam may be split by means other than diffraction.
The array of second DOEs 108 is positioned along the central axis A-A′ in proximity to the first DOE 106 (e.g., “in front” of the first DOE 106, relative to the direction in which light emitted by the light source 104 propagates). In particular, the array of second DOEs 108 is positioned such that the first DOE 106 is positioned between the light source 104 and the array of second DOEs 108. As more clearly illustrated in
Each second DOE 108 is positioned to intercept one of the secondary beams produced by the first DOE106 and to split the secondary beam into a plurality of (e.g., two or more) tertiary beams that are directed away from the second DOE 108 in a radial manner. Thus, each second DOE 108 defines a projection point of the sensor 100 from which a group of projection beams (or tertiary beams) is emitted into the field of view. In one embodiment, each respective plurality of tertiary beams fans out to cover a range of approximately one hundred degrees. The second DOEs 108 are any optical components that are capable of splitting a respective secondary beam into a plurality of tertiary beams that diverge from the secondary beam in different directions. For example, in one embodiment, each second DOE may include a conical mirror or holographic film. In other embodiments, however, the secondary beams are split by a means other than diffraction.
In one embodiment, each plurality of tertiary beams is arranged in a fan or radial pattern, with equal angles between each of the beams. In one embodiment, each of the second DOEs 108 is configured to project tertiary beams that create a different visual pattern on a surface. For example, one second DOE 108 may project a pattern of dots, while another second DOE 108 may project a pattern of lines or x's.
The imaging sensor 110 is positioned along the central axis A′A′, in the middle of the array of second DOEs 108 (e.g., at least partially “in front” of the array of second DOEs 108, relative to the direction in which light emitted by the light source 104 propagates). In one embodiment, the imaging sensor 110 is an image capturing device, such as a still or video camera. As discussed above, the imaging sensor 110 includes a wide-angle lens, such as a fisheye lens, that creates a hemispherical field of view. In one embodiment, the imaging sensor 110 includes circuitry for calculating the distance from the distance sensor 100 to an object or point. In another embodiment, the imaging sensor includes a network interface for communicating captured images over a network to a processor, where the processor calculates the distance from the distance sensor 100 to an object or point and then communicates the calculated distance back to the distance sensor 100.
Thus, in one embodiment, the distance sensor 100 uses a single light source (e.g., light source 104) to produce multiple projection points from which sets of projection beams (e.g., comprising patterns of dots or lines) are emitted. One or more of the projection beams may, in turn, form a projection plane. In one embodiment, at least one of the projection planes is parallel to the central axis A-A′ of the sensor 100. In a further embodiment, this projection plane is projected from a single one of the projection points or DOEs 108 (e.g., such that the plane would be vertically orientated in
The distance from the distance sensor 100 to an object can be calculated from the appearances of the projection beams in the field of view (as described in U.S. patent application Ser. No. 14/920,246, filed Oct. 22, 2015). In particular, the use of the first and second DOEs makes it possible to generate a plurality of projection points around the lens, from the single beam of light emitted by the light source. This allows the distance sensor 100 maintain a relatively compact form factor while measuring distance within a wide field of view. The imaging sensor 110 and the light source 104 can also be mounted in the same plane in order to make the design more compact; however, in one embodiment, the second DOEs 1081-108n are positioned behind the principal point of the imaging sensor 110 in order to increase the field of view that can be covered by the projection beams (e.g., such that the depth angle of the field of view is closer to a full 180 degrees, or, in some cases, even greater).
Moreover, since each of the second DOEs 108 projects tertiary beams of a different pattern, the circuitry in the imaging sensor can easily determine which beams in a captured image were created by which of the second DOEs 108. This facilitates the distance calculations, as discussed in greater detail below.
Although the sensor 100 is illustrated as including only a single light source 104 (which reduces the total number of components in the sensor 100), in alternative embodiments, the sensor may include a plurality of light sources. In this case, the first DOE 106 may not be necessary. Instead, in one embodiment, each light source of the plurality of light sources may correspond to one DOE in an array of DOEs (such as the array of second DOEs 108 in
In some embodiments, the distance sensor 100 may be configured to produce projection beams that form parallel patterns in a field of view.
All illustrated, the pattern 200 comprises two sets 2021 and 202n (hereinafter collectively referred to as “sets 202”) of projection beams. In one example, each set 202 of projection beams fans out radially from one of the projection points 108 of the sensor 100 to form a plane. As also illustrated, the planes defined by the two sets 202 of projection beams are substantially parallel to each other, due to the projection points 108 being spaced approximately 180 degrees apart from each other around the central axis A-A′ of the sensor 100.
By enabling multiple pairs of DOEs, where the DOEs in each pair of DOEs are spaced approximately 180 degrees apart from each other around the central axis A-A′, a plurality of parallel projection patterns or planes can be produced.
All illustrated, the pattern 300 comprises multiple parallel pairs of projection beams, indicated by the pairs of dashed lines a1 and a2 through f1 and f2. As in
In some embodiments, each pattern or plane that makes up a pair of parallel patterns is generated using at least two light sources and two DOEs or projection points, rather than one light source and one DOE. This is because some light sources, even when operating in conjunction with a DOE, may not be capable of generating a set of projection beams that fans out in an arc of larger than ninety degrees.
As illustrated, the pattern 400 comprises two projection patterns or planes 4021 and 4022 (hereinafter collectively referred to as “projection planes 402”). In one example, each projection plane 402, in turn, comprises two sets 4041 and 4042 or 404n-1 and 404n (hereinafter collectively referred to as “sets 404”) of projection beams that fan out radially from one of the projection points 408 of the sensor 100. In this case, each set 404 of projection beams fans out in an arc of approximately ninety degrees, and each pair of sets 404 spans an arc of approximately 180 degrees which corresponds to one projection plane 402. As illustrated, the projection planes 402 are substantially parallel to each other, due to the projection points 408 being spaced approximately 180 degrees apart from each other around the central axis A-A′ of the sensor 100.
In further embodiments, two sensors similar to the sensor 100 illustrated in
As illustrated, the pattern 500 comprises four projection patterns or planes 5021-5024 (hereinafter collectively referred to as “projection planes 502”). In one example, each projection plane 502, in turn, comprises two sets of projection beams that fan out radially from one of the projection points of the associated sensor 100. In this case, as in
In further embodiments, one DOE or projection point may generate a plurality of projection planes, where the plurality of projection planes are offset from each other by some angle. Moreover, two DOEs or projection points each generating a plurality of projection planes may be used to generate multiple parallel pairs of projection planes.
As illustrated, the pattern 600 comprises a plurality of pairs 6021-602n (hereinafter collectively referred to as “pairs 602”) of projection planes (where each individual projection plane comprises a set of projection beams that fan out in an arc of up to 180 degrees from a projection point 108, as described above). In this case, each projection point 108 generates one of the projection planes in each pair 602 of projection planes. Moreover, each projection point 108 generates a plurality of projection planes that fan out from each other in a direction substantially perpendicular to the direction in which the individual projection beams fan out. For instance, in
When the distance φ between the axis B-B′ and the central axis A-A′ of the distance sensor is known to be zero, (a/2)/D=tan(θ/2). Thus, the distance D from the imaging sensor 1704 to the object 1702 may be calculated as D=(a/2)/tan(θ/2). Also, D≈a/tan(θ) when a<<D.
When the distance φ between the axis B-B′ and the central axis A-A′ of the distance sensor is known to be a non-zero number, D≈a/tan(θ) when θ=(θ/2+φ)−(−θ/2+φ).
The method 800 begins in step 802. In step 804, a light source is activated to generate a primary beam of light. In one embodiment, a single primary beam is generated by a single light source; however, in other embodiments, multiple primary beams are generated by multiple light sources. In one embodiment, the light source or light sources comprise a laser light source.
In optional step 806, the primary beam is split into a plurality of secondary beams using a first beam splitting means (e.g., a diffractive optical element) that is positioned in the path along which the primary beam propagates. The first beam splitting means may be, for example, a conical mirror. Step 806 is performed, for example, when the distance sensor (of which the imaging sensor is a part) includes only a single light source.
In step 808, each beam in the plurality of secondary beams is split into a plurality of projection or tertiary beams using a second beam splitting means (e.g., second diffractive optical element) in an array of beam splitting means. In one embodiment, a plurality of second beam splitting means are positioned in a ring, such that each second beam splitting means is positioned in the path along which one of the secondary beams propagates. In one embodiment, at least some of the second beam splitting means are conical mirrors. In one embodiment, where the distance sensor comprises a plurality of light sources, the method 800 may proceed directly from step 804 to step 808. In this case, each primary beam of a plurality of primary beams (generated using the plurality of light sources) is directly split into a plurality of projection beams by one of the second beam splitting means.
In step 810, at least one image of the object or point is captured. The image includes a pattern that is projected onto the object or point and onto the surrounding space. The pattern is created by each of the projection beams projecting a series of dots, lines, or other shapes onto the object, point, or surrounding space. In one example, the pattern comprises one or more parallel pairs of projection beams or projection planes, for example as illustrated in
In step 812, the distance from the sensor to the object or point is calculated using information from the images captured in step 810. In one embodiment, a triangulation technique is used to calculate the distance. For example, the positional relationships between parts of the patterns projected by the sensor can be used as the basis for the calculation.
The method 800 ends in step 814. Thus, the method 800, in combination with the sensor depicted in
D=s/(−tan α2+tan α1+tan θ2+tan θ1) (EQN. 1)
where α2 is the angle formed between the projection beam 9002 and a central axis c2 of the second diffractive optical element 1082, α1 is the angle formed between the projection beam 9001 and a central axis c1 of the second diffractive optical element 1081, θ2 is the angle formed between the central optical axis O of the imaging sensor 110 and the angle at which the imaging sensor 110 perceives the point 9022 created by the projection beam 9002, and θ1 is the angle formed between the central optical axis O of the imaging sensor 110 and the angle at which the imaging sensor 110 perceives the point 9021 created by the projection beam 9001.
EQN. 1 is derived from the following relationships:
D*tan α1+D*tan θ1=x (EQN. 2)
D*tan α2+D*tan θ2=s−x (EQN. 3)
EQNs. 2 and 3 allow one to calculate the distance from a source of a projection pattern (comprising, e.g., a pattern of dots) to an object onto which the projection pattern is projected. The distance is calculated based on the positional relationship between the points of light (e.g., the dots) that form the projection pattern when the points of light are emitted by different projection points around the source. In this embodiment, the positional relationships between the points of light are known a priori (i.e., not measured as part of the calculation).
In further embodiments, distance calculations may be facilitated in different environments by tilting an angle of the imaging sensor 110 relative to the projection points or DOEs 108.
As illustrated in
The components are arranged substantially symmetrically about a central axis A-A′. In one embodiment, the central axis A-A′ coincides with the optical axis of the imaging sensor 1010. Although not illustrated, the light source is positioned at a first end of the central axis A-A′, and the first DOE, if included, is positioned along the central axis A-A′ in proximity to the light source (e.g., “in front” of the light source, relative to the direction in which light emitted by the light source propagates). In particular, the first DOE is positioned to intercept a single beam of light emitted by the light source and to split the single or primary beam into a plurality of secondary beams
The array of second DOEs 1008 is positioned along the central axis A-A′ in proximity to the first DOE (e.g., “in front” of the first DOE, relative to the direction in which light emitted by the light source propagates). In one embodiment, the second DOEs 1008 are arranged in a ring-shaped array, with the central axis A-A′ passing through the center of the ring and the second DOEs 1008 spaced at regular intervals around the ring. However, as illustrated in
In one embodiment, the second DOEs 1008 are spaced approximately thirty degrees apart around the ring. In one embodiment, the array of second DOES 1008 is positioned “behind” a principal point of the imaging sensor 1010 (i.e., the point where the optical axis A-A′ intersects the image plane), relative to the direction in which light emitted by the light source propagates.
Each second DOE 1008 is positioned to intercept one of the secondary beams produced by the first DOE and to split the secondary beam into a plurality of (e.g., two or more) tertiary beams that are directed away from the second DOE 1008 in a radial manner. Thus, each second DOE 1008 defines a projection point of the sensor 1000 from which a group of projection beams (or tertiary beams) is emitted into the field of view. In one embodiment, each respective plurality of tertiary beams fans out to cover a range of approximately one hundred degrees.
In one embodiment, each plurality of tertiary beams is arranged in a fan or radial pattern, with equal angles between each of the beams. In one embodiment, each of the second DOEs 1008 is configured to project tertiary beams that create a different visual pattern on a surface. For example, one second DOE 1008 may project a pattern of dots, while another second DOE 1008 may project a pattern of lines or x's.
The configuration illustrated in
The amount by which each of the projection artifacts (e.g., dots, dashes, x's, etc.) making up a projection beam moves relative to the distance from the sensor 1100 may vary with the size of the angle α. For instance, when the angle α increases, a projection artifact's movement relative to the distance from the sensor 1100 will also increase. In addition, the line density (e.g., how close multiple projection beams projected by a single DOE are to each other) will decrease with an increase in the angle α, as discussed in further detail below with respect to
Although
By tilting the projection beams, a projection pattern can be generated that allows one to calculate the distance to an object using non-overlapping projection artifacts (e.g., dots, dashes, or x's) on a single line of projection artifacts. By varying the angle α, the overlap between projection artifacts can be varied. For instance,
z=r0 sin θ (EQN. 4)
y=r0 cos θ sin α (EQN. 5)
x=r0 cos θ cos α (EQN. 6)
Thus,
r02=x2+y2+z2 (EQN. 7)
EQNs. 4-7 describe the positional relationships of a plurality of parameters of a tilted projection beam emitted by a distance sensor.
Referring to
z−b=R0 sin φ (EQN. 8)
y=R0 cos φ sin β (EQN. 9)
x+a=R0 cos φ cos β (EQN. 10)
Thus,
R02=(x+a)2+y2+(z−b)2 (EQN. 11)
From EQN. 4 and EQN 8, one can derive:
R0 sin φ+b=r0 sin θ (EQN. 12)
From EQN. 5 and EQN 9, one can derive:
R0 cos φ sin β=r0 cos θ sin α (EQN. 13)
From EQN. 6 and EQN 10, one can derive:
R0 cos φ cos β−a=r0 cos θ cos α (EQN. 14)
Thus,
β and φ are measured from an image captured by the imaging sensor; a, b, and α are known from the imaging sensor/projection settings; and θ is known from the projection pattern.
As illustrated, a projection point of the distance sensor 2000, such as projection point 2006, projects a projection beam onto an object 2010 positioned a distance D away from the imaging sensor 2006. An angle of the projection beam relative to an axis B-B′ extending radially outward from the central axis is defined by a. A portion of the light emitted by the projection beam is reflected back to the imaging sensor 2006 as a beam of return light.
The method 1500 begins in step 1502. In step 1504, a light source is activated to generate a primary beam of light. In one embodiment, a single primary beam is generated by a single light source; however, in other embodiments, multiple primary beams are generated by multiple light sources. In one embodiment, the light source or light sources comprise a laser light source.
In optional step 1506, the primary beam is split into a plurality of secondary beams using a first beam splitting means (e.g., a diffractive optical element) that is positioned in the path along which the primary beam propagates. The first beam splitting means may be, for example, a conical mirror. Step 806 is performed, for example, when the distance sensor (of which the imaging sensor is a part) includes only a single light source.
In step 1508, each beam in the plurality of secondary beams is split into a plurality of projection or tertiary beams using a second beam splitting means (e.g., second diffractive optical element) in an array of beam splitting means. In one embodiment, a plurality of second beam splitting means are positioned in a ring, such that each second beam splitting means is positioned in the path along which one of the secondary beams propagates. In one embodiment, at least some of the second beam splitting means are conical mirrors. In one embodiment, where the distance sensor comprises a plurality of light sources, the method 800 may proceed directly from step 1504 to step 1508. In this case, each primary beam of a plurality of primary beams (generated using the plurality of light sources) is directly split into a plurality of projection beams by one of the second beam splitting means.
In step 1510, at least one image of the object or point is captured. The image includes a pattern that is projected onto the object or point and onto the surrounding space. The pattern is created by each of the projection beams projecting a series of dots, lines, or other shapes onto the object, point, or surrounding space. In one example, the pattern comprises one or more projection beams that are offset or tilted relative to an imaginary reference line extending radially outward from the sensor's central axis A′A′, for example as illustrated in
In step 1512, the distance from the sensor to the object or point is calculated using information from the images captured in step 1510. In one embodiment, a triangulation technique such as that discussed above in connection with
The method 1500 ends in step 1514. Thus, the method 1500, in combination with the sensor depicted in
It should be noted that the present disclosure can be implemented in software and/or in a combination of software and hardware, e.g., using application specific integrated circuits (ASIC), a programmable logic array (PLA), including a field-programmable gate array (FPGA), or a state machine deployed on a hardware device, a general purpose computer or any other hardware equivalents, e.g., computer readable instructions pertaining to the method(s) discussed above can be used to configure a hardware processor to perform the steps, functions and/or operations of the above disclosed methods. In one embodiment, instructions and data for the present module or process 1605 for calculating distance (e.g., a software program comprising computer-executable instructions) can be loaded into memory 1604 and executed by hardware processor element 1602 to implement the steps, functions or operations as discussed above in connection with the example methods 800 and 1500. Furthermore, when a hardware processor executes instructions to perform “operations”, this could include the hardware processor performing the operations directly and/or facilitating, directing, or cooperating with another hardware device or component (e.g., a co-processor and the like) to perform the operations.
The processor executing the computer readable or software instructions relating to the above described method(s) can be perceived as a programmed processor or a specialized processor. As such, the present module 1605 for calculating distance (including associated data structures) of the present disclosure can be stored on a tangible or physical (broadly non-transitory) computer-readable storage device or medium, e.g., volatile memory, non-volatile memory, ROM memory, RAM memory, magnetic or optical drive, device or diskette and the like. More specifically, the computer-readable storage device may comprise any physical devices that provide the ability to store information such as data and/or instructions to be accessed by a processor or a computing device such as a computer or an application server.
While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/159,286, filed May 10, 2015, which is herein incorporated by reference in its entirety.
Number | Name | Date | Kind |
---|---|---|---|
4914460 | Caimi et al. | Apr 1990 | A |
5598299 | Hayakawa | Jan 1997 | A |
5730702 | Tanaka et al. | Mar 1998 | A |
5980454 | Broome | Nov 1999 | A |
20030071891 | Geng | Apr 2003 | A1 |
20060055942 | Krattiger | Mar 2006 | A1 |
20060290781 | Hama | Dec 2006 | A1 |
20070091174 | Kochi et al. | Apr 2007 | A1 |
20070206099 | Matsuo et al. | Sep 2007 | A1 |
20080128506 | Tsikos | Jun 2008 | A1 |
20100149315 | Qu et al. | Jun 2010 | A1 |
20100238416 | Kuwata | Sep 2010 | A1 |
20120113252 | Yang et al. | May 2012 | A1 |
20120225718 | Zhang | Sep 2012 | A1 |
20140009571 | Geng | Jan 2014 | A1 |
20140036096 | Sterngren | Feb 2014 | A1 |
20140071239 | Yokota | Mar 2014 | A1 |
20140125813 | Holz | May 2014 | A1 |
20140207326 | Murphy | Jul 2014 | A1 |
20140275986 | Vertikov | Sep 2014 | A1 |
20140320605 | Johnson | Oct 2014 | A1 |
20150009301 | Ribnick | Jan 2015 | A1 |
20150077764 | Braker | Mar 2015 | A1 |
20150171236 | Murray | Jun 2015 | A1 |
20150248796 | Iyer | Sep 2015 | A1 |
20150268399 | Futterer | Sep 2015 | A1 |
20160022374 | Haider | Jan 2016 | A1 |
20160128553 | Geng | May 2016 | A1 |
20160178915 | Mor et al. | Jun 2016 | A1 |
20160267682 | Yamashita | Sep 2016 | A1 |
20160327385 | Kimura | Nov 2016 | A1 |
20160334939 | Dawson | Nov 2016 | A1 |
20160350594 | McDonald | Dec 2016 | A1 |
20170307544 | Nagata | Oct 2017 | A1 |
Number | Date | Country |
---|---|---|
WO 2014-131064 | Aug 2014 | WO |
Entry |
---|
International Preliminary Report on Patentability, dated Nov. 23, 2017 in corresponding PCT Application No. PCT/US2016/031412, 10 pages. |
Search Report mailed in corresponding EP Patent Application No. 16 793 300.1, dated Oct. 22, 2018, 6 pages. |
Number | Date | Country | |
---|---|---|---|
20160327385 A1 | Nov 2016 | US |
Number | Date | Country | |
---|---|---|---|
62159286 | May 2015 | US |