Scan homogenization through velocity modulation

Abstract

Laser scanners that rotationally scan an environment at higher speeds are desirable in order to decrease measurement workflow times. However, due to the angular geometry of the spaced beams at constant velocity, scan data will have resulting holes at certain distances. Modulating the pan-axis velocity during rotation will provide a better quality point cloud with fewer holes and homogeneous density without substantially increasing the scanning times.

Description

P1839-US-WO (138178-81220)SCAN HOMOGENIZATION THROUGH VELOCITY MODULATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Number 63 / 788,430 filed April 14, 2025, the contents of which are incorporated by reference herein in their entirety.TECHNICAL FIELD

[0002] The present application is directed to a portable laser scanning system that scans an environment including objects therein, and in particular, it is directed to a scanning system that generates two-dimensional (2D) and / or three-dimensional (3D) point cloud data representing the environment.BACKGROUND

[0003] Certain portable multi -beam laser scanners have a sensor that emits a pattern of, say, 32 or more channels with an angular distance of about 1° between them. The sensor rotates about its central axis with a frequency of 5-20 Hertz (Hz), depending on the device settings and measurement workflow requirements. At the same time the scanner itself rotates about its vertical pan axis 360 degrees to capture digital representations of an environment. A full scan point cloud is generated by combining the information on the angles of both axes and the calibration (i.e. the pose of the sensor) using the distances measured by the sensor.

[0004] The simplest application is to rotate the scanning device at a constant angular velocity about the pan axis of the scanner. However, due to the geometry of the scanner with certain of its sensors being offset from the pan axis as well as the angular separation between the beams, this results in gaps and holes in the scanned point cloud data. The position and size of these holes depend on the distance from the scanner, the angular properties and rotation frequencies of the sensor and the angular velocities of the scanner during rotation. Such gaps and holes can be reviewed and filled algorithmically or manually, but this is very time consuming for an operator of theP1839-US-WO (138178-81220)scanning device to complete and can result in misrepresentations of the scanned environment.

[0005] Accordingly, while existing scanners are suitable for their intended purposes, there is a technological need for a scanner system having improved features as introduced herein.SUMMARY

[0006] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.

[0007] In various embodiments, a method for operating a scanning device comprises initiating a scan of an environment with a multi -beam laser sensor, rotating the scanning device around a pan axis during the scan, and modulating a pan-axis velocity during the rotating.

[0008] In additional embodiments, the pan axis velocity is modulated by substantially no more than 10% of a constant rotational velocity of the scanner. In certain embodiments, the pan axis velocity is modulated by an intermittent power signal, a stepped power signal and / or a sinusoidal power signal. In some instances, the rotating includes stopping the rotation periodically to image the environment with a camera. In some implementations, the pan axis velocity comprises no more than two peak velocities during the modulating.

[0009] The above features and advantages, and other features and advantages, of the disclosure are readily apparent from the following detailed description when taken in connection with the accompanying drawings.BRIEF DESCRIPTION OF DRAWINGS

[0010] The foregoing and other features and advantages of one or more embodiments described herein are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:P1839-US-WO (138178-81220)

[0011] FIG. 1 A depicts a laser scanner device according to one or more embodiments described herein;

[0012] FIG. IB is an additional schematic illustration of the laser scanning device of FIG 1A;

[0013] FIG. 2 illustrates the general processing system components of the laser scanning device of FIGS. 1 A and IB according to one or more embodiments described herein;

[0014] FIG. 3 depicts an exemplary pan axis of the laser scanner device of FIGS. 1A and IB according to one or more embodiments described herein;

[0015] FIG. 4 is an illustration of hole patterns in scan data of an exemplary point cloud according to one or more embodiments described herein;

[0016] FIG. 5 is an illustration of beam paths and scanning device / laser sensor rotations during a scan of an environment, according to one or more embodiments described herein;

[0017] FIG. 6 is an illustration of a segment of scan lines over a discrete intervals of rotation of a laser scanner device according to one or more embodiments described herein;

[0018] FIG. 7 is a first illustration of periodic hole structures in a segment of a scan according to one or more embodiments described herein;

[0019] FIG. 8 is a second illustration of periodic hole structures in a segment of a scan according to one or more embodiments described herein;

[0020] FIG. 9 is a graph of pan axis angles as a function of time at a constant pan axis velocity according to one or more embodiments described herein;

[0021] FIG. 10 is a graph of pan axis angles as a function of time with modulated pan axis velocity according to one or more embodiments described herein;P1839-US-WO (138178-81220)

[0022] FIG. 11 is a graph illustrating a constant pan axis velocity applied between intermittent stops during a full revolution of a laser scanning device while scanning according to one or more embodiments described herein;

[0023] FIG. 12 is a graph illustrating a first modulated pan axis velocity applied between intermittent stops during a full revolution of a laser scanning device while scanning according to one or more embodiments described herein;

[0024] FIG. 13 is a graph illustrating a second modulated pan axis velocity applied between intermittent stops during a full revolution of a laser scanning device while scanning according to one or more embodiments described herein;

[0025] FIG. 14 is a graph illustrating a third modulated pan axis velocity applied between intermittent stops during a full revolution of a laser scanning device while scanning according to one or more embodiments described herein;

[0026] FIG. 15A illustrates periodic holes in a scan without modulating pan axis velocity as in FIG. 11 according to one or more embodiments described herein;

[0027] FIG. 15B illustrates the disappearance of periodic holes from the scan of FIG.15 A in a scan with modulating pan axis velocity as in FIG. 12 according to one or more embodiments described herein;

[0028] FIG. 16A is an illustration of a first point cloud with periodic holes at constant pan axis velocity according to one or more embodiments described herein;

[0029] FIG. 16B is an illustration of the first point cloud of FIG. 16A without periodic holes accomplished at modulated pan axis velocity according to one or more embodiments described herein;

[0030] FIG. 17A is an illustration of a second point cloud with periodic holes at constant pan axis velocity according to one or more embodiments described herein; and

[0031] FIG. 17B is an illustration of the second point cloud of FIG. 17A without periodic holes accomplished at modulated pan axis velocity according to one or more embodiments described herein.P1839-US-WO (138178-81220)DETAILED DESCRIPTION

[0032] The following detailed description explains embodiments of the disclosure, together with advantages and features, by way of example with reference to the above-referenced drawings. The below features and advantages, and other features and advantages of the disclosure, are readily apparent from the following detailed description when taken in connection with the accompanying drawings. All embodiments described herein are non-limiting examples of at least one mode for implementing the features of the present disclosures, and unless otherwise indicated, other useful modes and design alternatives are readily contemplated without limitation.

[0033] With a 3D laser scanner, particularly but not limited to those having a multichannel sensor located at an offset with respect to the pan axis, rotation of the scanner to generate a point cloud of an environment during scanning operations is found to lead to a pattern of rhombus-shaped holes in the scan data, the location of which depends on the scanning distances involved and the pan axis rotation speed of the scanner. Slower rotation speeds (i.e., one full rotation in approximately ten minutes) would largely eliminate recurring gaps and holes in the scan data, but then necessarily entails longer scan times and more time-consuming measurement workflows. An improvement introduced herein is to instead use a modulated velocity of the pan axis at higher rotational velocities (i.e., one full rotation in approximately ten seconds, or under one minute) of the 3D laser scanner to generate a more homogeneous point cloud in less time than traditional detailed laser scanning.

[0034] The improvement includes not rotating the scanner with a constant velocity about the pan axis but instead using a modulated velocity profile (such as, but not limited to, intermittently powering the rotation, and / or providing a stepped power impetus or a sinusoidal power function to the motor driving the rotation). As the position of holes (i.e. the distance from the scanner) depends on the velocity of rotation, one can vary this velocity, and by doing that ‘average out’ the holes over a certain distance range. This leads to more homogeneous and effectively denser data,P1839-US-WO (138178-81220)which results in better detection of objects in the environment and better overall visual impression of resulting point clouds.

[0035] Referring now to FIGS. 1 A and IB, therein is shown a scanning system 100 for collecting and / or displaying images of an environment 222, or an object therein according to one or more embodiments described herein. FIG. 1 A depicts one view of the scanning system 100, which is for collecting and / or displaying images of an environment 222 or an object therein.

[0036] In various embodiments, the scanning system 100 includes a scan button 1, which is provided to turn it on and commence a scan. In some embodiments, there is a delay of one to several seconds between pressing the scan button 1 and the start of a scan. The scan button 1, in some embodiments, includes a light-emitting diode (LED) or other indicator to indicate that power to the scanning system 100 has been turned on. In various embodiments, the scanner system 100 rotates while scanning, when it is mounted on a tripod 8 (or other support) and is clear of obstructions. In some instances, the scanning system 100 is turned off by pressing the scan button 1 for a set duration.

[0037] In various embodiments, the scanning system 100 includes a battery level indicator 2 for displaying to a user a present charge level of a battery 10 or other power supply.

[0038] In various embodiments, the scanning system 100 includes a bi-directional data port 3, such as a universal serial port (USB or USB-C) for communicating with a network 207 or other processing or memory devices, such as a memory stick or the like to transfer scanning data thereto. In some instances, an LED indicator 5 is provided, which will indicate (i.e., by blinking green) while the data is being transferred to or from the scanning system 100 via the port 3 or via wireless (WiFi) adapter 4. In various embodiments, the scanning data from scanning system 100 is remotely uploaded to a cloud-based data processing program or the like, which may include, in various embodiments, SCENE, STREAM and / or SPHERE XG as provided by FARO Technologies, Inc.

[0039] In various embodiments, the laser scanner 6 scans the environment 222 and creates one single scan file for each individual scan, in similar manners to the FOCUSP1839-US-WO (138178-81220)scanner manufactured by FARO Technologies, Inc. and described inter alia in U.S. Patent No. 10,175,360 entitled “Mobile Three-dimensional Measuring Instrument,” the entirety of which is incorporated herein by reference. The different scans are then preregistered by the cloud-based data processing programs.

[0040] In various embodiments, the cameras 11 include two high-quality panorama camera(s) suitable for generating colorized (red, green blue, etc.) 3D point cloud data of the environment 222, as well as panoramic color images, as along with single shot, high resolution 360° images. Image data from the cameras 11 can be stored in electronic memory in open file formats such as PNG, JPEG, or GIF formats, where for improved compression, JPEG is recommended. In various implementations, the images have a 2: 1 aspect ratio and, for maximum performance and compatibility with virtual reality or other vision systems (e.g., GOOGLE VR), image dimensions resolutions be in powers of two (e.g., 2048 or 4096), although other implementations are readily contemplated.

[0041] In various embodiments, a quick mount adapter 7 secures the scanning system 100 to a tripod 8 or other support for accomplishing scans in the environment 222. In various embodiments, the scanning system 100 has at least one laser sensor 104 and an internal processing system 102, which will now be described in more detail.

[0042] Referring now to FIG. 2 The processing system 102 can be any suitable processing system, such as a built-in processing unit, a smartphone, tablet computer, laptop or notebook computer, node(s) of a cloud computing system, etc. Although not shown, the processing system 102 can include one or more additional components, such as one or more processors or microprocessors for executing processing instructions, a memory, such as a hard disk drive, random access memory, read-only memory, a memory chip or the like for storing the processing instructions and / or data in an electronic, computer-readable format, a display for displaying user interfaces, an input device for receiving inputs, an output device for generating outputs, a communications adapter for facilitating communications with other devices (e.g., the sensor 104), and / or the like including combinations and / or multiples thereof.P1839-US-WO (138178-81220)

[0043] The sensor 104 captures one or more images, such as a panoramic image, of an environment. In examples, the sensor 104 can be an ultra-wide angle sensor. As an example, the sensor 104 can be an omnidirectional sensor, such as a HESAI XT-32 sensor. In an embodiment, the sensor 104 includes at least one sensor, which, in various embodiments includes an array of photosensitive pixels. The sensor 104 is arranged to receive light from a lens. In an embodiment, the lens is an ultra-wide angle lens that provides a field of view 9 between 100 and 270 degrees, for example. In an embodiment, the field of view 9 is greater than 180 degrees and less than 270 degrees. It should be appreciated that while embodiments herein describe the lens as a single lens, this is for exemplary purposes and the sensor 104 may be comprised of a plurality of optical elements.

[0044] In various non-limiting embodiments, the sensor 104 may be a multi -beam laser sensor, such as the XT-32 sensor, which is continuously mechanically rotated through 360° and has 32 beams (channels) that are fanned out in 1° steps. For each pulse, up to two reflected pulses can be detected. The sensor 104 rotates at 5 Hertz (Hz), 10 Hz, or 20 Hz and independent of rotation speed, up to substantially 640,000 scan points of the environment are generated per second.

[0045] In some embodiments, the sensor 104 includes a pair of sensors 110A, HOB that are arranged to receive light. In this disclosure, the sensor 104 is sometimes referred to as a dual sensor because it has a pair of sensors and corresponding lens. A first sensor and lens are arranged to acquire images in a first direction, and a second sensor and lens are arranged to acquire images in a second direction. In the illustrated embodiment, the second direction is opposite the first direction (e.g., 90 or 180 degrees apart). A sensor having opposingly arranged sensors and lenses with at least a 180 degree field of view is sometimes referred to as an omnidirectional sensor, a 360 degree sensor, or a panoramic sensor, since it acquires an image in a 360 degree volume about at least one axis of the sensor.

[0046] The processing system 102 includes a processing device 202 (e.g., one or more of the processing devices 521 of FIG. 5), a system memory 204 (e.g., the RAM 524 and / or the ROM 522 of FIG. 5), a network adapter 206 (e.g., the network adapter 526 of FIG. 5), a data store 208, a display 210, sensor(s) 211, a capture engine 212, and an alignment and trajectory engine 214.P1839-US-WO (138178-81220)

[0047] In various embodiments, the components, modules, engines, etc. described regarding FIG. 2 (such as, the capture engine 212 and the alignment and trajectory engine 214) are implemented as computer processing instructions that are stored on a computer-readable storage medium, in hardware modules, as special-purpose hardware (e.g., application specific hardware, application specific integrated circuits (ASICs), application specific special processors (ASSPs), field programmable gate arrays (FPGAs), as embedded controllers, hardwired circuitry, etc.), or as some combination or combinations of these. According to aspects of the present disclosure, the engine(s) described herein is / are a combination of hardware and programming. The programming is embodied in processor-executable instructions stored in a tangible memory, and the hardware can include the processing device 202 for executing those instructions. Thus, the system memory 204 can store program instructions that when executed by the processing device 202 implement the engines described herein. Other engines can also be utilized to include other features and functionality described in other examples herein. The network adapter 206 enables the processing system 102 to transmit data to and / or receive data from other sources, such as the sensor 104.

[0048] In various embodiments, the sensor 104 is any suitable device for collecting images of an object or an environment 222. For example, the processing system 102 receives data (e.g., an image or set of images of the environment 222) from the sensor 104 directly and / or via a wired or wireless network 207. The data (e.g., image(s)) from the sensor 104) is stored in the data store 208 of the processing system 102 as data 209a (also referred to as “images 209a”). According to one or more embodiments described herein, the capture engine 212 causes the sensor 104 to capture the data 209a (e.g., images), such as by transmitting an activation signal to the sensor 104. According to one or more embodiments described herein, the sensor 104 captures the data 209a automatically and / or responsive to some other trigger event (e.g., a user command) and transmits the data 209a to the processing system 102 for processing and / or storage.

[0049] According to one or more embodiments described herein, the capture engine 212 uses the sensor(s) 211 to capture additional data and / or images of theP1839-US-WO (138178-81220)environment 222 as data 209b. According to one or more embodiments described herein, the processing system 102 generates a representation of the data 209a and / or the data 209b as a point cloud, which is displayed on the display 210. The sensor(s) 211 can include one or more sensors for capturing data / information about the environment 222. The sensor(s) 211 can include one or more of the following: a sensor, an omnidirectional sensor, a panoramic sensor, a 360-degree sensor, a light detection and ranging (LiDAR) sensor, and / or the like, including combinations and / or multiples thereof.

[0050] The network 207 represents any one or a combination of different types of suitable communications networks such as, for example, cable networks, public networks (e.g., the Internet), private networks, wireless networks, cellular networks, or any other suitable private and / or public networks. Further, the network 207 can have any suitable communication range associated therewith and may include, for example, global networks (e.g., the Internet), metropolitan area networks (MANs), wide area networks (WANs), local area networks (LANs), or personal area networks (PANs). In addition, the network 207 can include any type of medium over which network traffic may be carried including, but not limited to, coaxial cable, twistedpair wire, optical fiber, a hybrid fiber coaxial (HFC) medium, microwave terrestrial transceivers, radio frequency communication mediums, satellite communication mediums, or any combination thereof.

[0051] During image capture, the sensor 104 is arranged on, in, and / or around the environment 222 to collect data / images of the environment 222. For example, the sensor 104 captures a sequence of images of the environment while moving along a path or trajectory.

[0052] According to one or more embodiments described herein, using images (e.g., the data 209a) received from the sensor 104 and / or the images (e.g., the data 209b) captured by the sensor(s) 211, the processing system 102 performs various photogrammetry functions. Photogrammetry is a technique for modeling objects using images, such as photographic images acquired by a digital sensor. Photogrammetry can make three-dimensional (3D) models from two-dimensional (2D) images or photographs. When two or more images are acquired at different positions that haveP1839-US-WO (138178-81220)an overlapping field of view, common points or features (sometimes referred to herein with respect to “tie points”) are identified in each image. By projecting a ray from the sensor location to the feature / tie point on the object, the 3D coordinate of the feature / point is determined using trigonometry or triangulation in various embodiments. In some examples, photogrammetry may be based on markers / targets (e.g., lights or reflective stickers) placed on an object in the environment or based on distinctive natural features thereof. To perform photogrammetry, in various instances, images are captured, with a sensor having one or more sensors (such as a photosensitive array for example). By acquiring multiple images of an object, or a portion of the object, from different positions or orientations, 3D coordinates of points on the object are determined based on common features or points and information on the position and orientation (e.g., pose, or pitch, yaw, or roll angle) of the sensor when each image is acquired. In order to obtain the desired information for determining 3D coordinates, the features are identified in two or more images. Since the images are acquired from different positions or orientations, the common features are located in overlapping areas of the field of view of the images. It should be appreciated that one method of performing photogrammetry techniques is described in commonly-owned U.S. Patent No. 10,477,180 entitled “PHOTOGRAMMETRY SYSTEM AND METHOD OF OPERATION” filed in the name of Wolke et al., the contents of which are incorporated by reference herein. With photogrammetry, two or more images are captured and used to determine 3D coordinates of features.

[0053] Different configurations are possible, such as a linear configuration, a circular configuration, a back-to-back configuration, and / or the like including combinations and / or multiples thereof. The particular arrangement of sensors can be selected to provide a desired overlap and coverage of the object or environment being captured. The sensors may have the same or different focal lengths and / or resolutions depending on the specific aspects of the photogrammetric task to be performed.

[0054] Sensor calibration is performed for each individual sensor to determine its intrinsic parameters. Examples of intrinsic parameters can include focal length, principal point, lens distortion coefficients, skew, aspect ratio, and / or the like including combinations and / or multiples thereof. Sensor calibration is performed using on-the-fly calibration in which no additional data is obtained before or after theP1839-US-WO (138178-81220)image capture. Common points produced through feature extraction and matching in images involving the same location in an environment or on an object, as described herein, can be used in this process. In various embodiments, each sensor is calibrated individually by using the portion of an image set selected for sensor calibration. A number of common features and root mean squares of errors (RMSE) of bundle adjustment, as described herein, is considered for image candidates. To obtain enough common points suitable for sensor calibration, and to have a sufficiently large base line among the sensor poses, the sensors can be arranged orthogonally to the direction of movement.

[0055] Once the intrinsic parameters of each sensor are computed, the relative orientations of the sensor(s) can be determined. This involves finding the translation and rotation between the sensors’ coordinate systems. The relative orientation calibration can be performed using a calibration object with known 3D points. This object is placed within the environment (e.g., the environment 222), and the 3D points of the object are captured in the images from each sensor. By matching the 3D points in the images, the relative pose between the sensors can be computed.

[0056] According to one or more embodiments described herein, another approach to relative orientation calibration is based on an on-the-fly system calibration. This approach uses common image points of the images of the image sequence and can be applied to applications like trajectory estimation, where scale information is not being used.

[0057] FIG. 3 depicts an exemplary pan axis 300 of the scanner system 100 of FIGS 1 A and IB according to one or more embodiments described herein. As shown therein, the sensor 6, in various embodiments, is located at a position that is not vertically above the axis, as can be seen in the image. As a result, the position of the rotating sensor 6 oscillates as the scanning system 100 itself rotates around some portion of 360 degrees, or one or more revolutions therethrough during scanning operations which geometrically results in gaps, spaces, holes and bands of the same at certain distances during faster pan axis rotational speeds as illustrated further in the following.

[0058] FIG. 4 is an illustration of holes 420 including recurring patterns of the same in scan data of an exemplary point cloud 400 according to one or more embodimentsP1839-US-WO (138178-81220)described herein. Such holes 420 cannot be interpolated automatically or readily manually filled-in by adding more points because they are typically dimensionally large and, accordingly, some underlying scenography or structure could be missed or misrepresented. To understand better the reason for this result, a simplified system description is provided, from which one can understand the origin of the holes 420 in the point cloud 400.

[0059] FIG. 5 is an illustration of beam paths and scanning system 100 / laser sensor 6 rotations during a scan of an environment 222, according to one or more embodiments described herein. Each laser beam 502 rotates about the LiDAR rotation axis 500 of the sensor 6 and draws a circle. When projecting these circles onto a plane 504 towards the bottom of the scanning system 100, for example at a floor of the environment 222, a set of lines 506 is drawn. Near the pan axis 300, the lines are straight, and as one gets further apart the lines 506 bend. For simplicity it is assumed in this example that the lines 506 are substantially straight.

[0060] Without rotation about the pan axis 300, the point cloud 400 at the bottom would consist of only these lines 506. When adding the pan axis rotation, the line pattern also rotates. At a given rotation speed of the pan axis and also for the sensor 6, the pattern of lines 506 gets rotated by discrete angles, which depend on the rotation speed.

[0061] FIG. 6 is an illustration of a segment of scan lines 506 over discrete intervals of rotation of a scanner system 100 according to one or more embodiments described herein. The illustrated exemplary rotated pattern for, say, seven lines 506 from the sensor 6 over just five rotation angles then results in recurring holes 420, which in various embodiments are typically rhombus-shaped due to this geometry.

[0062] FIG. 7 is a first illustration of certain of the periodic holes 420 in a segment of a scan according to one or more embodiments described herein, while FIG. 8 is a second illustration of certain periodic holes 420 in a zoomed in segment of a scan in FIG. 7 and / or when more pan axis angles are added, according to one or more embodiments described herein. As can be seen here, a periodic hole structure comprising repeating holes 420 is seen, which in turn depends on the spacing between the laser beams 502P1839-US-WO (138178-81220)and on the pan axis 300 and LiDAR axis rotation frequencies of the sensor 6. As observed, these hole structures repeat many times as distances get further away from the pan axis 300. However, in reality, as distances grows, the lines 506 are measurably bent, not straight as assumed above, and the hole structures get further affected.

[0063] In the forgoing Figures above, the pan axis angles are all equidistant and determine the orientation of each line 506 on the plane 504. If the pan axis angles are plotted as a function of time, one gets the following graph in FIG. 9 of pan axis angles at a constant pan axis velocity resulting in the straight line 900 according to one or more embodiments described herein.

[0064] FIG. 10 is a graph of pan axis angles as a function of time with, on the other hand, a modulated pan axis velocity according to one or more embodiments described herein. After adding even a small modulation 1000 on top of the straight line 900, the periodicity of the line crossings is found to be broken and as a result, the number of hole structures in resulting point clouds 400 are greatly reduced and / or eliminated, as illustrated in more detail later below.

[0065] FIG. 11 is a graph illustrating a constant pan axis velocity 1100 applied between intermittent stops 1102 during a full revolution of a scanning system 100 while scanning according to one or more embodiments described herein. It should be noted that the constant pan axis velocity 1100 in practice is not mathematically “constant” but instead is readily understood by one of ordinary skill in the art to include some minor hysteresis and non-linearities during motion as is typical of most any motor-induced rotations, and it is readily further understood that such non-linearities are typically of a magnitude that are too small to affect measurements using scan data and the resulting point cloud generation significantly. Also, in embodiments where the scanning system 100 includes cameras 11 for photographic imaging of the environment 222, in addition to the laser scanning performed by the sensor 6, the rotation of the scanning system 100 may periodically and intermittently substantially or completely stop one or more times (such as but not limited to five times as shown in the exemplary embodiment herein) so that the scanning system 100 images portions of the environment 222 for position determination, and are used in turn to render realistic representations of the environmentP1839-US-WO (138178-81220)222 to be added to the scanned point cloud data corresponding to such captured images. As used herein, substantially stopping, in various implementations, refers to allowing the rotation to slow to a non-zero velocity that does not substantially image quality, point capture or other capturing, measurement functions and the like as variously described herein.

[0066] FIG. 12 is a graph illustrating a first modulated pan axis velocity 1200 applied between intermittent stops 1102 during a full revolution of the scanning system 100 while scanning, in which two peak velocities are demonstrated there according to one or more embodiments described herein. In some embodiments, the peak velocity is substantially equal to the constant pan axis velocity 1100, while the trough velocity is substantially 90% of the peak velocity, i.e. substantially 10% lower than peak velocity. In alternate embodiments, the trough velocity is substantially 20-25% lower than the peak velocity, however, such decreases demonstrate no real additional improvement in the elimination of holes. In various implementations, this velocity profile of the first modulated pan axis velocity 1200 is achieved in any of a variety of useful manners. For example, the peak velocities and fall-offs or troughs thereafter are accomplished by initiating power to a motor that imparts rotation and then turning off the motor when peak velocity is achieved. In other implementations, a step-up or step-down power function or the like is employed to increase and decrease power to the rotational motor to achieve the velocity profile displayed. In still further implementations, a sinusoidal or similar power function is provided to the rotational motor to achieve the desired velocity profile. However, these examples are not limiting. These and other manners of achieving the velocity profile illustrated here as well as in the following Figures are readily contemplated. As can be observed in the following (see FIGS. 15A-17B), such modulation strongly reduces and / or eliminates the hole patterns, and / or gets them to a size which can then at least be filled in by interpolation.

[0067] The position of the holes 420 projected to the floor or other plane depends on parameters like the rotation speed of the pan axis as well as the rotation speed of the sensor 6 about the LiDAR axis, the angle between each individual laser beam and the distance to the floor. The angle between the beams combined with the distance to the floor define the distance between the individual lines on the floor.P1839-US-WO (138178-81220)

[0068] The angle (designated herein as beta) that is the result of a combination of the sensor rotation speed and the pan axis rotation is about 3° at about 12 seconds for a 360° pan axis rotation means 30° per second. Where the sensor 6 simultaneously rotates at 10 Hz, each rotation is one line 506 and therefore the angle between two lines 506 is 3°. It has been observed that there are many positions at which the holes appear. Additionally, the holes have different size (d_h), depending on their distance (r) to the pan axis rotation axis. Based on the approximations above (and also employing further simplifications), one can estimate the expected positions for bands of holes 420: The holes 420 for which the distance d_h is the same as the line spacing d is at a distance from the pan axis given by r = d / sin(beta). Holes with this same size appear also at multiples of this distance. These are the holes which should be eliminated or reduced. For the holes with size d_h = d / 2, the distance is r = d / ( 2 * sin(beta)).

[0069] Another important point is that the modulation can be replaced by many different types of curves which help to break the periodicity of the hole structure. FIG.13 is a graph illustrating a second modulated pan axis velocity 1300 applied between intermittent stops during a full revolution of a laser scanning device while scanning, in which three peak velocities are illustrated therein according to one or more embodiments.

[0070] FIG. 14 is a graph illustrating a third modulated pan axis velocity 1400 applied between intermittent stops during a full revolution of a laser scanning device while scanning in which four peak velocities are illustrated therein according to one or more embodiments. Additional modulation with additional numbers of peak velocities can likewise be used, however, it has been observed that two peak velocities as in FIG. 12 is sufficient to eliminate holes 420 sufficiently to properly register resulting point clouds 400 and that additional peaks in the pan axis velocities do not significantly further reduce the number of holes 420 or periodic occurrences thereof in hole structures.

[0071] FIG. 15A illustrates periodic holes 420 in a scan without modulating pan axis velocity as in FIG. 11 according to one or more embodiments described herein. FIG.15B, on the other hand, illustrates the disappearance of periodic holes 420 from the scanP1839-US-WO (138178-81220)of FIG. 15A resulting from a scan with modulating pan axis velocity profiles such as is shown in FIG. 12 according to one or more embodiments described herein. At the central part we see that the hole structures are gone and in the outer part it partially remains there. The reason for this is because for visibility reasons the simulated data is only for pan axis angles between -40° and 40°. If the entire 360° range is plotted, then the entire pattern will be like the central region as well.

[0072] FIG. 16A is an illustration of a first point cloud with periodic holes 420 at constant pan axis velocity according to one or more embodiments described herein. FIG. 16B, on the other hand, is an illustration of the first point cloud of FIG. 16A without periodic holes 420 accomplished at a modulated pan axis velocity profile such as is shown in FIG. 12 according to one or more embodiments described herein. It should be noted that in some embodiments, some holes in the data are still visible but the magnitude of the holes is strongly reduced so as not to significantly affect measurement data.

[0073] FIG. 17A is an illustration of a second point cloud 400 with periodic holes 420 at constant pan axis velocity according to one or more embodiments described herein. FIG. 17B, on the other hand, is an illustration of the second point cloud 400 of FIG.17A without periodic holes 420 accomplished at modulated pan axis velocity profile, such as is shown in FIG. 12 according to one or more embodiments described herein. It should be noted that in some embodiments, some holes in the data are still visible but the magnitude of the holes is strongly reduced so as not to significantly affect measurement data.

[0074] In the various embodiments herein, it has been observed that the small modulations in pan axis speed do not significantly affect other model parameters of the scanning system 100, such as levelling accuracy, optical tracking stability and the like.

[0075] In an implementation, a method for operating a scanning device includes initiating a scan of an environment with a multi-beam laser sensor, rotating the scanning device around a pan axis during the scan, and modulating a pan-axis velocity during the rotating.P1839-US-WO (138178-81220)

[0076] The pan axis velocity may be modulated by substantially no more than 10% of a constant rotational velocity of the scanning device.

[0077] The pan axis velocity may be modulated by an intermittent power signal, a stepped power signal, and / or a sinusoidal power signal.

[0078] The intermittent power signal, the stepped power signal, and the sinusoidal power signal may be power signals applied to a motor of the scanning device.

[0079] The rotating may include substantially or completely stopping the rotation periodically to image the environment with a camera.

[0080] The method may further include obtaining images of the environment when the rotation of the scanning device around the pan axis is substantially or completely stopped, and combining the images of the environment that are obtained when the rotation of the scanning device around the pan axis is substantially or completely stopped with point cloud data obtained during the scan, the point cloud data corresponding to the images of the environment that are obtained when the rotation of the scanning device around the pan axis is substantially or completely stopped.

[0081] The pan axis velocity may include no more than two peak velocities during the modulating.

[0082] A pan-axis angle may be modulated during the rotating of the scanning device around the pan axis during the scan.

[0083] The method may further include emitting a laser beam from the multi-beam laser sensor of the scanning device during the scan, and rotating the scanning device around a LiDAR rotation axis during the scan, such that the laser beam emitted from the multi-beam laser sensor of the scanning device rotates around the LiDAR rotation axis to generate a circle, wherein a line pattern is generated by projecting the circle onto a plane, the line pattern rotates due to the scanning device rotating around the pan axis during the scan, and the pan-axis angle comprises an angle of the line pattern generated while the scanning device rotates around the pan axis during the scan.

[0084] The circle may be projected onto the plane towards a floor of the environment.

[0085] The rotating of the scanning device around the pan axis during the scan may be induced by a motor of the scanning device, and the motor may be substantially or completely stopped when the pan-axis velocity reaches a peak velocity.P1839-US-WO (138178-81220)

[0086] The modulating of the pan-axis velocity during the rotating may be performed to fill holes in scan data that are generated as a result of rotating the scanning device around the pan axis during the scan.

[0087] In an additional implementation, a scanning device includes a motor, a camera, and a multi-beam laser sensor, wherein the scanning device is caused to: emit a laser beam from the multi-beam laser sensor of the scanning device, initiate a scan of an environment with the multi-beam laser sensor using the emitted laser beam, induce the motor to rotate the scanning device around a pan axis during the scan, and modulate, during the rotating, a pan-axis velocity of the rotating of the scanning device around the pan axis.

[0088] The pan axis velocity may be modulated by at least one of: substantially no more than 10% of a constant rotational velocity of the scanning device, an intermittent power signal applied to the motor of the scanning device, a stepped power signal applied to the motor of the scanning device, and a sinusoidal power signal applied to the motor of the scanning device.

[0089] The scanning device may be further caused to: obtain, using the camera, images of the environment when the rotation of the scanning device around the pan axis is stopped, wherein the rotating includes stopping the rotation periodically to image the environment with the camera, and combine the images of the environment that are obtained when the rotation of the scanning device around the pan axis is substantially or completely stopped, with point cloud data obtained during the scan, the point cloud data corresponding to the images of the environment that are obtained when the rotation of the scanning device around the pan axis is substantially or completely stopped.

[0090] In another implementation, a scanning device includes a motor, and a multibeam laser sensor, at least one processor, and at least one memory storing instructions that when executed by the at least one processor, cause the scanning device to: emit a laser beam from the multi-beam laser sensor of the scanning device, initiate a scan of an environment with the multi-beam laser sensor using the emitted laser beam, induce the motor to rotate the scanning device around a pan axis during the scan, modulate, during the rotating, a pan-axis velocity of the rotating of the scanning device around the pan axis, wherein a pan-axis angle is modulated during the rotating of theP1839-US-WO (138178-81220)scanning device around the pan axis during the scan, and induce the motor to rotate the scanning device around a LiDAR rotation axis during the scan, such that the laser beam emitted by the scanning device rotates around the LiDAR rotation axis to generate a circle, wherein a line pattern is generated by projecting the circle onto a plane towards a floor of the environment, the line pattern rotates due to the scanning device rotating around the pan axis during the scan, and the pan-axis angle comprises an angle of the line pattern generated while the scanning device rotates around the pan axis during the scan.

[0091] The scanning device may be further caused to induce the motor to substantially or completely stop when the pan-axis velocity reaches a peak velocity.

[0092] It will be appreciated that one or more embodiments described herein may be embodied as a system, method, or computer program product and may take the form of a hardware embodiment, a software embodiment (including firmware, resident software, micro-code, etc.), or a combination thereof. Furthermore, one or more embodiments described herein may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

[0093] The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ± 8% or 5%, or 2% of a given value.

[0094] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, operations, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, operations, operations, element components, and / or groups thereof.

[0095] While the disclosure is provided in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the disclosure can be modified toP1839-US-WO (138178-81220)incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that the embodiment(s) may include only some of the described aspects. Accordingly, the disclosure is not to be seen as limited by the foregoing description.

Claims

P1839-US-WO (138178-81220)What is claimed is:

1. A method for operating a scanning device, comprising:initiating a scan of an environment with a multi-beam laser sensor, rotating the scanning device around a pan axis during the scan, and modulating a pan-axis velocity during the rotating.

2. The method of claim 1, wherein the pan axis velocity is modulated by substantially no more than 10% of a constant rotational velocity of the scanning device.

3. The method of claim 1, the modulating further comprises modulating the pan axis velocity by an intermittent power signal.

4. The method of claim 1, the modulating further comprises modulating the pan axis velocity by a stepped power signal.

5. The method of claim 1, the modulating further comprises modulating the pan axis velocity by a sinusoidal power signal.

6. The method of claim 1, the modulating comprises applying a power signals to a motor of the scanning device.

7. The method of claim 1, the rotating includes stopping the rotation periodically to image the environment with a camera.

8. The method of claim 7, further comprising:obtaining images of the environment when the rotation of the scanning device around the pan axis is substantially stopped, andcombining the images of the environment that are obtained when the rotation of the scanning device around the pan axis is substantially stopped with point cloud data obtained during the scan, the point cloud data corresponding to the images of theP1839-US-WO (138178-81220)environment that are obtained when the rotation of the scanning device around the pan axis is stopped.

9. The method of claim 1, wherein the pan axis velocity comprises no more than two peak velocities during the modulating.

10. The method of claim 1, wherein a pan-axis angle is modulated during the rotating of the scanning device during the scan.

11. The method of claim 10, further comprising:emitting a laser beam from the multi-beam laser sensor of the scanning device during the scan, androtating the scanning device around a light detection and ranging (LiDAR) rotation axis during the scan, such that the laser beam emitted from the multi-beam laser sensor of the scanning device rotates around the LiDAR rotation axis to generate a circle,wherein a line pattern is generated by projecting the circle onto a plane, the line pattern rotates due to the scanning device rotating around the pan axis during the scan, and the pan-axis angle comprises an angle of the line pattern generated while the scanning device rotates around the pan axis during the scan.

12. The method of claim 11, wherein the circle is projected onto the plane towards a floor of the environment.

13. The method of any of claims 1, wherein the rotating of the scanning device around the pan axis during the scan is induced by a motor of the scanning device, and the motor is temporarily stopped when the pan-axis velocity reaches a peak velocity.

14. The method of any of claims 1, wherein the modulating of the pan-axis velocity during the rotating is performed to fill holes in scan data that are generated as a result of rotating the scanning device around the pan axis during the scan.P1839-US-WO (138178-81220)15. A scanning device, comprising:a motor,a camera, anda multi-beam laser sensor, wherein the scanning device:emits a laser beam from the multi-beam laser sensor of the scanning device, initiates a scan of an environment with the multi-beam laser sensor using the emitted laser beam,induces the motor to rotate the scanning device around a pan axis during the scan, andmodulates, during the rotating, a pan-axis velocity of the rotating of the scanning device around the pan axis.

16. The scanning device of claim 15, wherein the pan axis velocity is modulated by at least one of:substantially no more than 10% of a constant rotational velocity of the scanning device,an intermittent power signal applied to the motor of the scanning device, a stepped power signal applied to the motor of the scanning device, and a sinusoidal power signal applied to the motor of the scanning device.

17. The scanning device of claim 15, where the scanning device further:obtains, using the camera, images of the environment when the rotation of the scanning device around the pan axis is stopped,wherein the rotating includes stopping the rotation periodically to image the environment with the camera, andcombines the images of the environment that are obtained when the rotation of the scanning device around the pan axis is stopped with point cloud data obtained during the scan, the point cloud data corresponding to the images of the environment that are obtained when the rotation of the scanning device around the pan axis is stopped.P1839-US-WO (138178-81220)18. The scanning device of claim 15, wherein the pan axis velocity comprises no more than two peak velocities during the modulating.

19. A scanning device, comprising:a motor, anda multi-beam laser sensor,at least one processor, andat least one memory storing instructions that when executed by the at least one processor, cause the scanning device to:emit a laser beam from the multi-beam laser sensor of the scanning device, initiate a scan of an environment with the multi-beam laser sensor using the emitted laser beam,induce the motor to rotate the scanning device around a pan axis during the scan,modulate, during the rotating, a pan-axis velocity of the rotating of the scanning device around the pan axis,where a pan-axis angle is modulated during the rotating of the scanning device around the pan axis during the scan, andinduce the motor to rotate the scanning device around a light detection and ranging, LiDAR, rotation axis during the scan, such that the laser beam emitted by the scanning device rotates around the LiDAR rotation axis to generate a circle, where a line pattern is generated by projecting the circle onto a plane towards a floor of the environment, the line pattern rotates due to the scanning device rotating around the pan axis during the scan, and the pan-axis angle comprises an angle of the line pattern generated while the scanning device rotates around the pan axis during the scan.

20. The scanning device of claim 19, where the processing instructions further cause the scanning device to:induce the motor to stop when the pan-axis velocity reaches a peak velocity.

Images