Patent Application
20240027623
The invention relates to a method for determining a profile section of an object and/or space by means of a 2D laser scanner having a laser rangefinder. The invention further relates to a 2D laser scanner.
From DE 10 2009 027 668 A1, a laser rangefinder is known in which the laser beam can be rotated within a measuring plane by means of a mirror, in order to measure multiple angle-dependent distances within the measuring plane. These distances are measured between the laser diode emitting a laser beam in the laser rangefinder and the surrounding walls.
The invention proceeds from a method for determining a profile section of an object and/or space by means of a 2D laser scanner having a laser rangefinder and a 2D laser scanner. The 2D laser scanner comprises at least one laser rangefinder, wherein the 2D laser scanner is configured to record mutually assignable, in particular assigned, distance measurement values and distance measurement directions by means of the laser rangefinder in a measuring plane that is at least partially traversed radially by a laser beam of the laser rangefinder. The 2D laser scanner is used to measure objects and/or spaces while generating a profile section of the object or space, in particular a two-dimensional profile section. Such 2D laser scanners are used by architects, room or building planners, realtors or craftspeople to determine the shape and/or size of spaces and/or objects (such as swimming pools). The 2D laser scanner finds particular application in the context of measuring tasks as they occur in particular in the artisanal field. For example, the 2D laser scanner finds application in an interior design of buildings or in construction work in general.
The 2D laser scanner comprises a laser rangefinder for non-contact distance measurement. The laser rangefinder further comprises at least one laser light source, in particular a laser diode, for generating laser radiation. The laser rangefinder is provided for emitting time-modulated laser radiation in the form of a laser beam in the distance measurement direction towards a target object, the distance of which to the laser rangefinder is to be determined. Laser radiation reflected or scattered by the target object, i.e., radiated back, is at least partially detected by the laser rangefinder, in particular by a receiver of the laser rangefinder, and used to determine the distance measurement value to be measured in the distance measurement direction. The receiver is configured to detect laser radiation that has been radiated back. From the emitted laser radiation and the laser radiation reflected from the surface of the target object, a light transit time is determined by means of a phase comparison and the desired distance measurement value between the laser rangefinder, i.e. the 2D laser scanner, and the target object is determined from the speed of light. Alternatively, the light transit time can also be determined from a flight time determination. The underlying concepts of non-contact distance measurement by laser are known to a person skilled in the art. The terms laser radiation and laser beam are used interchangeably here. By at least partially traverse it is understood that only sections of the plane (for example over an angular range of 180°) are also traversed and/or that the emitted laser beam is temporarily interrupted as it moves in the measuring plane from one distance measurement direction (measuring position) to the next distance measurement direction (measuring position).
The 2D laser scanner is configured to orient the laser beam emitted by means of the laser rangefinder in different spatial directions so that distance measurement values are obtained in different spatial directions, i.e. distance measurement directions. The 2D laser scanner is specifically configured to have the laser beam of the laser rangefinder traverse a measuring plane at least partially in the radial direction—starting from the laser rangefinder in the center. For example, this can be realized by rotating the laser rangefinder about an axis of rotation that is oriented perpendicular to the direction of emission of the laser beam. The zero point of the distance measurement can advantageously lie on the axis of rotation—and thus in the center of the rotational movement. Alternatively, it is conceivable for beam-directing optical elements, for example diffractive elements, mirrors, reflectors or the like, to be used to enable the laser beam to be transmitted in different spatial directions in a technically simple manner, wherein the laser beam of the laser rangefinder also traverses a measuring plane at least partially in the radial direction—starting from the optical element in the center. In particular, the 2D laser scanner can include a drive device for aligning, in particular rotating about the axis of rotation, the laser rangefinder, or the beam-directing optical element. For example, the drive device can be viewed to act via an electric motor or alternatively, using a retractable spring as in an egg timer that is prestressed in such a way and subsequently relaxed again in a defined manner. A particularly simple, automated recording of the distance measurement values in different distance measurement directions is realized by the drive device. The distance measurement direction in three-dimensional space, in particular in the measuring plane traversed by the laser beam, in which the laser beam is transmitted to the target object, is recorded during the execution of a respective distance measurement by means of a sensor or via a control device, for example the drive device. In this sense, the distance measurement direction is also recorded by means of or using the laser rangefinder since a given orientation of the laser rangefinder defines the distance measurement device presently in effect at this time. The recording of the distance measurement direction can be realized, for example, by recording a distance measurement angle, for example an angle of rotation of the laser rangefinder with respect to the aforementioned axis of rotation. The distance measurement direction is so defined by the distance measurement angle with respect to the 2D laser scanner. By aligning the laser beam, in particular as a result of aligning the laser rangefinder, it is possible to perform distance measurements in different distance measuring directions, i.e. different spatial directions, without having to change the position of the 2D laser scanner itself. In this way, the measurement of the object and/or space, and the creation of the profile section is accelerated accordingly compared to the performance of a plurality of individual measurements, because the 2D laser scanner only has to be positioned once (in particular as centrally as possible in the space) and subsequently different distance measurements are carried out without changes in location.
In this way, mutually assignable or assigned distance measurement values and distance measurement directions, in particular distance measurement angles, are determined by means of the laser rangefinder in a measuring plane that is at least partially traversed radially by the laser beam of the laser rangefinder during the execution of a 2D laser scan. By mutually assignable/assigned, it is to be understood that an associated distance measuring direction, in particular an assigned distance measuring angle, is recorded and processed, in particular at least temporarily stored, by means of the 2D laser scanner for each recorded distance measuring value. The recorded distance measurement values and distance measurement directions initially represent a profile section in the abstract form of a 2D point cloud. The profile section should be understood to mean that the data set comprises mutually assigned distance measurement values and distance measurement directions that lie within a measuring plane which is at least partially traversed radially by the laser beam of the laser rangefinder during a 2D laser scan, so that a type of room section—the profile section as an imaginary section of the space produced by the measuring plane—is obtained. The profile section can then be further processed and/or outputted to a user of the 2D laser scanner for example by means of a computing unit, in particular an evaluation unit, and/or using an output device (internal or external to the device) such as a display screen. Further, different evaluations such as surface calculations, angle calculations, creation of floor plans, etc. are conceivable based on the profile section. Various types of evaluation of such profile sections are known to the person skilled in the art.
When measuring typical spaces, most surfaces where laser distance measurement values are measured are vertical walls or horizontal ceilings and floors. In the following, (without limitation to generality) only the case of a measurement of vertical walls—i.e. the measuring plane of the 2D laser scanner is aligned nearly horizontally—is discussed for simplification. It should be noted that the transfer to a measurement with the measuring plane nearly vertically aligned is also easily possible. In the best case scenario, a profile section resulting from the measurement of vertical walls is intended to include distance measurement values and distance measurement directions that lie in an (ideal) horizontal plane. In this case, the horizontal plane is the reference plane. If this is not the case—i.e. the measuring plane has an angle of inclination with respect to the horizontal plane—a distorted profile section results that is not well suited for further evaluation. The method according to the invention allows a profile section initially recorded at an angle of inclination of the measuring plane with respect to the horizontal plane (or generally to a reference plane) in the aftermath of the 2D laser scan by mathematically projecting the recorded distance measurement values and the distance measurement directions onto the (ideal) horizontal plane (or reference plane). Correcting refers to converting the recorded distance measurement values by means of trigonometric functions and using the angle of inclination, wherein distance measurement values projected into the (ideal) horizontal plane (generally: reference plane) are obtained.
In one embodiment of the 2D laser scanner, the scanner comprises a computing unit configured to execute the method according to the invention to determine a profile section. A computing unit, in particular a computer device, is to be understood in particular as a processor unit.
In a further aspect of the invention, a system consisting of a 2D laser scanner and a computing unit realized externally to the 2D laser scanner is proposed. The 2D laser scanner is configured to record, by means of the laser rangefinder, mutually assignable or assigned distance measurement values and distance measurement directions, in particular distance measurement angles, in a measuring plane that is at least partially traversed radially by a laser beam of the laser rangefinder. The computing unit, for example in the form of a smart device, such as a tablet, a smartphone, or the like, is configured to execute the method according to the invention for determining a profile section. In this embodiment, the correction is carried out according to the method according to the invention on a computing unit external to the 2D laser scanner, wherein the profile section required for this purpose and any further information (for example, the angle of inclination or data for determining the same) is provided, in particular transmitted to the external computing unit using a data communication interface of the 2D laser scanner. For example, a data communication interface is understood to be a Bluetooth, Bluetooth Low Energy, WiFi data communication interface or the like. An external computing unit is understood to mean, for example, a smartphone, a cloud, a computer, a tablet, or the like.
The method according to the invention for determining a profile section of an object and/or space proceeds from a method comprising the method steps of:
Correcting the profile section requires knowledge of the angle of inclination of the measuring plane with respect to the reference plane. According to the invention, the angle of inclination of the measuring plane is determined using the laser rangefinder. The reference plane represents a horizontal or vertical plane depending on the direction in which the measuring plane is aligned.
Methods known in the prior art, for example from U.S. Pat. No. 8,699,005 B2, are known for determining the angle of inclination using an accelerometer or an inertia sensor that records the orientation of the laser rangefinder and thus of the measuring plane. This requires the integration of additional particularly precise and consequently expensive sensors in the 2D laser scanner. The proposed method makes it possible to omit additional sensors and still record, in a simple manner, an angle of inclination by means of which the recorded profile section can be corrected.
In one embodiment of the method, the angle of inclination of the measuring plane is determined in an additional, in particular an additional calibration measurement. For example, in one embodiment of the method, during the calibration measurement
In particular, it is conceivable to initiate the execution of a calibration measurement by means of an input means of the 2D laser scanner, whereupon a measurement sequence of the plurality of distance measurements is triggered. During the measurement sequence, the plurality of individual distance measurements transverse to the measuring plane (always starting from the center of the laser rangefinder, only at a (pivot) angle) are then carried out. From this plurality of distance measurements, at least one minimum value is then determined in the distance measurement values, which is precisely the case when the laser beam lies in the reference plane. In this way, it is possible to determine the angular deviations of the measuring plane in this direction simply by pivoting the laser beam during the calibration measurement over the surface to be measured.
In one embodiment of the method, the two different distance measurement directions are selected orthogonally to each other. In this way, a mathematically particularly simple, consequently not very computationally intensive and thus quickly feasible method can be specified.
In one embodiment of the method, the plurality of distance measurement values are recorded at increasing and/or decreasing angles with respect to the measuring plane during manual or automatic tilting (or pivoting) of the laser rangefinder, in particular of the 2D laser scanner. An automatic tilting of the laser rangefinder can be realized, for example, by means of a specific (tilting) actuator. The actuator can be realized in the form of a motor. Alternatively or additionally, a manual tilting can be realized by means of a mechanical pivoting device. In this way, a method can be provided that is capable of being implemented in a constructively simple manner.
In one embodiment of the method, the angle of inclination of the measuring plane is determined from the profile section itself. In particular, it is conceivable that in one embodiment of the method, the angle of inclination is determined by simulation in the event that a distortion of the profile section is compensated as a result of variation (change) of the angle of inclination. In the event that the distortion of the profile section disappears completely (at least within the framework of tolerance limits) and thus is compensated, the simulation-determined (varied) angle corresponds to the angle of inclination of the measuring plane actually sought. Consequently, in this way, a configuration of the method can be specified in which no particular design precautions of the 2D laser scanner need to be provided.
In an alternative or additional embodiment of the method, the angle of inclination is determined by trigonometric calculation from two distance measurement values in different, in particular non-collinear or non-parallel, distance measurement directions as well as from the angular distance between these distance measurement directions. In this way, in particular, the angle of inclination of the measuring plane can be calculated from an adjustment of distance measurement values expected according to a predetermined or pre-determinable angular distance (for example, predetermined by a step width of a stepper motor) with actually recorded distance measurement values. This method is also realizable without special design precautions in the 2D laser scanner.
In one embodiment of the method, the determined angle of inclination of the measuring plane is refined or adjusted using a sensor, in particular an inertial sensor such as a gravitational sensor or an accelerometer or a rotation rate sensor or the like, an inclination sensor, an electro-optical bubble level or an electrolytically-operating sensor. Such sensors, which are known to a person skilled in the art, permit a simple, in particular small-scale integration into the 2D laser scanner.
The invention is explained in further detail in the following description with reference to embodiment examples shown in the drawings. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will appropriately also consider the features individually and combine them into further meaningful combinations. In the figures, identical reference numbers denote functionally identical elements.
Shown are:
The illustration of
The 2D laser scanner 10 comprises a housing 12 with edge lengths in a range of 4 to 15 cm. The housing 12 encloses the mechanical components as well as the optical and electronic components (see in particular
During the performance of a respective distance measurement, the distance measurement direction 20 of the laser beam 18 is recorded in the form of a distance measurement angle 36 with respect to the axis of rotation 26 in the measuring plane 34 (cf.
The 2D laser scanner 10 is configured to automatically measure an object and/or a space (cf.
The 2D laser scanner 10 further comprises an operator element 40 for initiating performing a 2D laser scan. Further, the 2D laser scanner 10 comprises a data communication interface, not shown in more detail here, by means of which a recorded profile section 38 as well as further relevant information can be provided to an external computing unit 70, here in the form of a smartphone. For this purpose, the external computing unit 70 also comprises a data communication interface of the same type, which is not shown in more detail here, for example a Bluetooth data communication interface. The transmission of data is shown in
Further, the housing 12 of the 2D laser scanner 10 comprises a battery compartment. A battery compartment lid 44 closes the battery compartment flush with the surface of the housing 12. The battery compartment is used to hold batteries (not shown in more detail here) or also rechargeable batteries for powering the 2D laser scanner 10.
In
In method step 1006, the angle of inclination 50 of the measuring plane 34 with respect to the reference plane 52, in this case the horizontal reference plane 52, is then determined. This can be done in a variety of ways.
In a first embodiment example of method step 1006—referred to here as (a)—the angle of inclination 50 of the measuring plane 34 is determined in a separate calibration measurement. In the process, in sub-method steps
Method step 1006a.1 is realized using actuator 48 shown in
In
In a second embodiment example of method step 1006—referred to herein as (b)—the angle of inclination 50 of the measuring plane 34 is determined from the profile section 38, 38a itself, wherein the angle of inclination 50 is determined by simulation in the event that a distortion of the profile section 38, 38a is compensated as a result of variation of the angle of inclination 50 such that the desired profile section 38, 38b (i.e., a straight or kink-free profile expected according to typical wall designs) is obtained.
In a third embodiment example of method step 1006—referred to herein as (c)—the angle of inclination 50 of the measuring plane 34 is determined from the profile section 38, 38a itself by trigonometric calculation of two different, non-collinear or non-parallel distance measurement directions 20, 20a, 20b as well as the angular distance 58 between these distance measurement directions 20, 20a, 20b.
Finally, in method step 1008, the distorted profile section 38, 38a is corrected using the determined angle of inclination 50 of the measuring plane 34 by converting the recorded distance measurement values 20, 20a, 20b by means of trigonometric functions and using the angle of inclination 50, wherein the distance measurement values 20, 20a, 20b are projected into the reference plane 52 in this manner.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 216 159.3 | Dec 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/080942 | 11/8/2021 | WO |
