DE102020211136A1 - Method for determining a change in at least one air column property in optical navigation systems - Google Patents

Abstract

A method for determining a change in at least one air column property (110) in at least one working volume (112) of an optical navigation system (114) is proposed. The optical navigation system (114) further includes at least one multilateration system (122). The multilateration system (122) has at least three retroreflectors (124) and at least six localization units (126) or at least six retroreflectors (124) and at least three localization units (126). The locating units (126) are either located around the working volume (112) or the retroreflectors (124) are located around the locating units (126).

Description

technical field

The invention relates to a method for determining a change in at least one air column property in at least one working volume of an optical navigation system and an optical navigation system. The present invention relates in particular to the field of optical coordinate metrology.

Technical background

Distance or coordinate measurements over very large distances, or for large workpieces, are increasingly required for industrial metrology with accuracies that were previously only required for comparatively small distances and small workpieces. The previous system designs can come up against insurmountable limits here, if a completely unrealistic environment is not required for the use of the machine. This is due to the fact that in the traditional and essentially mechanical system designs, the accuracy is provided by a precise movement system, also referred to as a mover, with which the sensors for measuring the workpiece are fed in and the position is recorded at the same time. The traditional system designs can be unsuitable for accuracies in the range of a few micrometers on workpieces with typical length dimensions of a few meters and in manufacturing environmental conditions. Separating the tasks of sensor delivery and sensor localization may be more suitable: A comparatively imprecise mover delivers the sensor and an optical system records the sensor coordinates, see Leica's T-Scan plus LaserTracker. However, this approach may not be able to fully utilize the accuracy potential of the optical distance measurement technology used over long distances or in large volumes. This is largely due to the fact that, particularly in the production environment, the properties of the air in which the light from the optical distance measuring technology propagates are not sufficiently constant.

In principle, it is possible to design distance measurement technology in such a way that changes in the propagation medium along the measurement section can be recorded. Guillory et al. describe in "Towards Kilometric Distance Measurements with Air Refractive Index Compensation", for example, an approach using a measurement setup with two laser wavelengths of 785 nm and 1550 nm associated with considerable additional hardware effort, with which existing optical systems would have to be supplemented, and is therefore unattractive for reasons of complexity and cost.

object of the invention

It is therefore the object of the present invention to provide a device and a method which at least largely avoid the disadvantages of known devices and methods. In particular, compensation for fluctuations in air column properties should be made possible with little complexity in terms of hardware.

General Description of the Invention

This object is addressed by methods and devices having the features of the independent patent claims. Advantageous developments, which can be implemented individually or in any combination, are presented in the dependent claims.

In the following, the terms "have", "have", "comprise" or "include" or any grammatical deviations thereof are used in a non-exclusive manner. Accordingly, these terms can refer both to situations in which, apart from the features introduced by these terms, no further features are present, or to situations in which one or more further features are present. For example, the phrase "A has B," "A has B," "A includes B," or "A includes B" can both refer to the situation in which there is no other element in A other than B (ie to a situation in which A consists exclusively of B), as well as to the situation in which, in addition to B, there are one or more other elements in A, e.g. element C, elements C and D or even further elements .

Furthermore, it is pointed out that the terms "at least one" and "one or more" as well as grammatical variations of these terms, if they are used in connection with one or more elements or features and are intended to express that the element or feature is provided once or several times can generally only be used once, for example when the feature or element is introduced for the first time. If the feature or element is subsequently mentioned again, the corresponding term "at least one" or "one or more" is generally no longer used, without restriction the possibility that the feature or element can be provided one or more times.

Furthermore, the terms “preferably”, “particularly”, “for example” or similar terms are used below in connection with optional features, without alternative embodiments being restricted thereby. Thus, features introduced by these terms are optional features and are not intended to limit the scope of the claims, and in particular the independent claims, by these features. Thus, as will be appreciated by those skilled in the art, the invention may be practiced using other configurations. Similarly, features introduced by "in an embodiment of the invention" or by "in an exemplary embodiment of the invention" are understood as optional features without intending to limit alternative configurations or the scope of the independent claims. Furthermore, through these introductory expressions, all possibilities to combine the features introduced here with other features, be they optional or non-optional features, remain untouched.

In a first aspect of the present invention, a method for determining a change in at least one air column property in at least one working volume of an optical navigation system is proposed.

wobei K, D und g zwei Faktoren beschrieben in Bönsch, G. and E. Potulski (1998), „Measurement of the refractive index of air and comparison with modified Edlen's formulae“, IOP Metrologia, Volume 35, No. 2, pp. 133-139, t die Temperatur, p der Druck, x der CO₂ Anteil und p_ω der Partialdruck von Wasserdampf ist. Der Begriff „Änderung der Luftsäuleneigenschaft“, wie er hier verwendet wird, ist ein weiter Begriff, dem seine gewöhnliche und gängige Bedeutung beigemessen werden soll, wie der Fachmann sie versteht. Der Begriff ist nicht beschränkt auf eine spezielle oder angepasste Bedeutung. Der Begriff kann, ohne Beschränkung, sich insbesondere auf eine Variation und/oder Schwankung der Luftsäuleneigenschaft entlang einer Messstrecke, insbesondere einem optischen Pfad, beziehen. Die Luftsäuleneigenschaft entlang der Messstrecke kann räumlich und/oder zeitlich inhomogen sein, beispielsweise können Brechzahlschwankungen auftreten. Derartige Inhomogenitäten können beispielsweise in industriellen Fertigungsumgebungen auftreten. Beispielsweise können auch Turbulenzen, also räumlich und zeitlich variierende Verwirbelungen, auftreten.The term "air column" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to an amount of air that is located between an observation location and an object whose distance from the observation location is to be measured. The term "air column property" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to at least one physical property, in particular optical property, of the air column. The air column property can in particular include at least one property selected from the group consisting of: a refractive index; a refractive index distribution in the working volume; a refractive index variation; and a turbulence. The term "refractive index" as used herein, also called refractive index or optical density, is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term can refer, without limitation, to an optical property of a medium, which can be specified by the ratio of the wavelength of light in vacuum to the wavelength of light in the medium. The medium is in particular air. The so-called Edlen equation can be used to determine the refractive index n in air: $$n\left(\lambda ,t,p,x,p_{\omega }\right)-1=K\left(\lambda \right)D\left(t,p,x\right)-p_{\omega }G\left(\lambda \right),$$

where K, D and g are two factors described in Bönsch, G. and E. Potulski (1998), "Measurement of the refractive index of air and comparison with modified Edlen's formulae", IOP Metrologia, Volume 35, No. 2, pp. 133-139, t is the temperature, p is the pressure, x is the proportion of CO ₂ and p _{ω is} the partial pressure of water vapour. The term "change in air column property" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a variation and/or fluctuation in the air column property along a measurement section, in particular an optical path. The air column property along the measurement section can be spatially and/or temporally inhomogeneous, for example there can be fluctuations in the refractive index. Such inhomogeneities can occur, for example, in industrial manufacturing environments. For example, turbulence, i.e. spatially and temporally varying turbulence, can also occur.

The term "system" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a device comprising a plurality of components or elements that cooperate at least in part to perform at least one function.

The term "visual navigation system" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a technical system that is set up for optical position determination. The visual navigation system can be set up to calibrate at least one precision machine, in particular a coordinate measuring machine or a processing machine. The optical position determination can include determining at least one spatial position and/or orientation. The spatial position and/or the orientation can be determined in a coordinate system, for example a Cartesian coordinate system or a spherical coordinate system. Other coordinate systems are also conceivable. An origin or zero point of the coordinate system can be in a point of the optical navigation system. The term "spatial position" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term can, without limitation, refer to a three-dimensional point (X, Y, Z) in the coordinate system. The spatial position can be defined by the location coordinates X, Y and Z. The term "orientation" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a rotation of the measurement object, in particular an angular position. The orientation can be specified by at least three angles, for example Euler angles or pitch angles, roll angles and yaw angles. The spatial position and orientation together can also be referred to as six-dimensional information or 6D information.

The optical navigation system includes at least one multilateration system. The term "multilateration" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a geometric method for determining coordinates of at least one point in space, in which a distance of the point from at least three other known points is determined and from this the coordinates of the point are determined. The term "multilateration system" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a system configured to perform multilateration.

The multilateration system comprises at least three retroreflectors and at least six localization units or at least six retroreflectors and at least three localization units. The multilateration system can be set up to carry out a 6 DoF multilateration. A relative position, in particular a spatial position and/or a distance between the retroreflectors and/or a relative position, in particular a spatial position and/or a distance between the localization units, can be known. For example, the retroreflectors can be arranged in a plane in the form of a triangle. The lengths of the sides of the triangle can be known. Provided that the position of the retroreflectors relative to each other is known, 3D trajectories of all three retroreflectors or a 6D trajectory of a system of retroreflectors can be reconstructed from a sequence of length changes measured with the localization units.

The term "retroreflector" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Specifically, the term may refer, without limitation, to any device that reflects a beam of light in the direction from which the beam of light arrived. For example, the retroreflector can be a marker. For example, the retroreflector can be selected from the group consisting of: a cat's eye; a cat's eye with a reflective layer; a marker described in U.S. 2011/0007326 A1 , U.S. 2013/0050410 A1 or US 2017/0258531 A1 , the content of which is hereby incorporated into this application; a cube prism; a corner cube.

The term "localization unit" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to any device that is set up to generate at least one piece of localization information. The localization information can be selected from at least one piece of information from the group consisting of: a measurement signal depending on the location of the retroreflector illuminated by the localization unit; information about a distance of the retroreflector illuminated by the localization unit from the localization unit; information about a distance from the retroreflector illuminated by the localization unit to the localization unit; information about a position of the retroreflector illuminated by the localization unit relative to the localization unit; and information about a change in length.

The localization unit, in particular each of the localization units, can have at least one sensor system based on transit time and/or interferometry measurement principles. The localization unit, in particular each of the localization units, can comprise at least one element selected from the group consisting of: a laser tracer; a laser tracker; a LIDAR sensor, preferably an FMCW LIDAR sensor, time-of-flight (TOF) range finder, other range finders, for example based on at least one mode-locked laser.

The term "laser tracer" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to any measuring device which is set up to determine a distance, in particular a change in distance, to a retroreflector interferometrically. The laser tracer can be set up to track a position of the retroreflector at different points in time. The laser tracer can be set up to follow a retroreflector moving in space by means of a laser beam. The change in distance can be measured incrementally. The laser tracer can be an incremental measuring system with a large field of view, in particular a large pivoting range of a laser beam direction. For example, at least two consecutive measurements may be required to measure the change in distance. The laser tracer can cover a large angular range. For example, the laser beam of the laser tracer can be pivoted in the large angular range.

The term "laser tracker" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to any measuring device which is set up to interferometrically determine a distance and/or a direction of a retroreflector, in particular relative to axes which are defined by an optomechanics of the laser tracker.

The term "LIDAR sensor" as used herein is a broad term that should be given its ordinary and conventional meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to any device based on the LIDAR ("light detection and ranging") measurement principle, also called LADAR (laser detection and ranging). In particular, the LIDAR sensor can be set up to generate and receive a light beam, for example a laser beam, in particular the light beam previously emitted by it and reflected back to it, and from this to determine a distance between the LIDAR sensor and the retroreflector, for example exploiting differences in return times and wavelengths. The localization unit can preferably have an FMCW LIDAR sensor. "FMCW" is an abbreviation for the English expression "Frequency Modulated Continuous Wave". The FMCW LIDAR sensor can be set up to generate the light beam, the frequency of which is continuously tuned according to the FMCW method. For example, the frequency of the light beam can be linearly modulated with time. A combination of LIDAR methods and FMCW methods are known in principle to those skilled in the art, for example from Chip-scale Lidar, Benham Behroozpur Baghmisheh, Technical Report no. UCB/EECS.2017-4. For example, the LIDAR unit as in U.S. 9,559,486 B2 , U.S. 8,913,636 B2 or U.S. 2016/123718 A1 be designed. FMCW LIDAR sensors are more robust and less expensive than laser tracers. Furthermore, the FMCW LIDAR sensors can be insensitive to so-called line-of-sight interruptions, since they are absolute measuring systems. Furthermore, hybrid systems can be used with the addition of mode-locked lasers.

The multilateration system can be a self-calibrating multilateration system. When using three retroreflectors and six locating units, the locating units and the retroreflectors can be arranged and/or aligned with one another in one of the following configurations: four locating units on a first retroreflector, one locating unit on a second retroreflector and one locating unit on a third retroreflector (four -one one); three locating units on the first retroreflector, two locating units on the second retroreflector and one locating unit on the third retroreflector (three-two-one); two locating units on the first retroreflector, two locating units on the second retroreflector and two locating units on the third retroreflector (two-two-two).

For example, the optical navigation system can have the first retroreflector, the second retroreflector and the third retroreflector. For example, the optical navigation system can have a first localization unit, a second localization unit, a third localization unit, a fourth localization unit, a fifth localization unit and a sixth localization unit. The first, second, third and fourth localization units may be aligned with, also referred to as locked onto, and illuminate the first retroreflector. The fifth localization unit can be aligned with and illuminate the second retroreflector. The third retroreflector can be illuminated by the sixth locating unit. This corresponds to the four-one-one configuration. It is noted that in both this and the following examples, the ordinal numbers of the retroreflectors and localization units are used as designations for distinction. Accordingly, the localization units can be interchangeable or interchangeable. The retroreflectors can also be interchangeable or interchangeable. For example, referring to the example above, the second retroreflector may be illuminated by the sixth locating unit and the third retroreflector may be illuminated by the fifth locating unit. Other combinations are possible. Four localization units thus follow the same retroreflector and can each carry out a distance measurement between the localization unit and the retroreflector. Thus, more distance measurements can be carried out than spatial coordinates have to be determined. After a certain number of distance measurements, the position of the localization units relative to one another can be determined. Such a multilateration system is referred to as self-calibrating.

For example, the first retroreflector may be illuminated by the first, second, and third localization units. The second retroreflector can be illuminated by the fourth and fifth locating units. The third retroreflector can be illuminated by the sixth locating unit. This corresponds to the three-two-one configuration. For example, the first retroreflector can be illuminated by the first and the second localization unit. The second retroreflector can be illuminated by the third and fourth locating units. The third retroreflector can be illuminated by the fifth and sixth locating units. This corresponds to the configuration two-two-two. It is possible for the localization units to be interchanged with one another and for the retroreflectors to be interchanged with one another.

The localization units are arranged around the working volume or the retroreflectors are arranged around the localization units. The term "working volume" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a volume in which the optical position determination can take place. Together with the localization units, the retroreflectors can span and/or define the working volume. The working volume can be determined by a measuring range of the optical navigation device, ie a range in which the optical position can be determined within specified limits. The working volume can be a 6 (Degree of Freedom) DOF tracking volume.

The term "arranged about the working volume" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to an arrangement in which the retroreflectors are illuminated from the outside in by the locating units. In particular, the locating units may not be concentrated in a center of the working volume and/or may not be distributed coplanarly at or near a volume boundary. At least two locating units can be positioned so that they face each other. The term "face to face" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a relative spatial position of the localization units to one another, such that observation directions of the localization units located opposite one another are antiparallel to one another. The mutually opposite localization units can be arranged on a common straight line or connecting line, with the measurement object to be measured being arranged between the localization units. Changing air column properties can thus be derived from apparent position shifts associated with them from contradictions in the system of equations to be solved when determining the position of the measurement object. The air column properties can introduce additional degrees of freedom, which require the approach of further positions, before the system of equations can be solved. If the air column properties change more slowly than it takes to move to the required positions, the system can be self-calibrating in the sense described by reference to the returned laser wavelength of the localization units used.

The term "arranged around the locating units" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to an arrangement in which the locating units illuminate the retroreflectors from the inside out. The retroreflectors can be arranged on a measurement object and the localization units can be arranged in space and/or the localization units can be arranged on the measurement object and the retroreflectors can be arranged in space. The retroreflectors can be spaced far apart. The retroreflectors can be arranged such that they are widely spaced within the working volume. The localization units can each have a holder for arranging, setting up and/or fastening the localization units. The retroreflectors can also each have at least one holder for arranging, setting up and/or fastening the retroreflectors.

The term "measurement object" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to an arbitrarily shaped object to be measured. For example, the measurement object can also be a measuring head of a sensor or a tool with which a component can be scanned.

1. a) Erzeugen jeweils mindestens eines Beleuchtungslichtstrahls mit mindestens zwei der Lokalisierungseinheiten und Beleuchten eines gemeinsamen Retroreflektors oder eines Retroreflektor-Ensembles aus unterschiedlichen Raumrichtungen mit den Beleuchtungslichtstrahlen der Lokalisierungseinheiten;
2. b) Empfangen jeweils mindestens eines des von dem gemeinsam beleuchteten Retroreflektor oder dem Retroreflektor-Ensemble reflektierten Lichtstrahls und Erzeugen jeweils mindestens eines Messsignals mit den, den Retroreflektor gemeinsam oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheiten;
3. c) Auswerten der Messsignale der Lokalisierungseinheiten, wobei das Auswerten ein Bestimmen einer ersten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles aus einem Messsignal einer ersten, den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheit und einer zweiten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles aus einem Messsignal einer zweiten, den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheit umfasst, so dass für den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble zwei Positionen bestimmt werden;
4. d) Bestimmen der Luftsäuleneigenschaft durch Vergleichen der ersten Position und der zweiten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles, wobei eine im Wesentlichen identische Änderung der ersten Position und der zweiten Position als eine Änderung der Luftsäuleneigenschaft charakterisiert wird.

The procedure includes the following steps:

1. a) generating in each case at least one illuminating light beam with at least two of the localization units and illuminating a common retroreflector or a retroreflector ensemble from different spatial directions with the illuminating light beams of the localization units;
2. b) receiving in each case at least one of the light beams reflected by the jointly illuminated retroreflector or the retroreflector ensemble and generating in each case at least one measurement signal with the localization units which jointly illuminate the retroreflector or the retroreflector ensemble;
3. c) Evaluation of the measurement signals of the localization units, the evaluation determining a first position of the jointly illuminated retroreflector or of the retroreflector ensemble from a measurement signal of a first localization unit illuminating the jointly illuminated retroreflector or the retroreflector ensemble and a second position of the jointly illuminated retroreflector or the retroreflector ensemble from a measurement signal from a second localization unit illuminating the jointly illuminated retroreflector or the retroreflector ensemble, so that two positions are determined for the jointly illuminated retroreflector or the retroreflector ensemble;
4. d) determining the air column property by comparing the first position and the second position of the co-illuminated retroreflector or retroreflector ensemble, wherein a substantially identical change in the first position and the second position is characterized as a change in the air column property.

The method steps can be carried out in the order given, with one or more of the steps being able to be carried out at least partially simultaneously and with one or more of the steps being able to be repeated several times. In addition, other steps, whether or not mentioned in the present application, can additionally be carried out.

The term "illuminating light beam" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to any beam of light that is emitted and/or transmitted to illuminate the retroreflector. In particular, the illuminating light beam can be a light beam generated by one of the localization units for illuminating one of the retroreflectors. The localization units can each have at least one lighting unit. The lighting unit can have a light source, in particular a laser source.

The term "light" as used herein is a broad term, to which its ordinary and shall be given the usual meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to electromagnetic radiation in at least one spectral range selected from the visible spectral range, the ultraviolet spectral range and the infrared spectral range. The term visible spectral range basically covers a range from 380 nm to 780 nm. The term infrared (IR) spectral range basically covers a range from 780 nm to 1000 µm, with the range from 780 nm to 1.4 µm being referred to as near infrared (NIR), and the range from 15 µm to 1000 µm is called far infrared (FIR). The term ultraviolet generally encompasses a spectral range from 100 nm to 380 nm. The term "ray of light" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to an amount of light emitted and/or transmitted in a particular direction.

The method includes receiving at least one of the light beams reflected by the jointly illuminated retroreflector or by the retroreflector ensemble and generating at least one measurement signal with the localization units that illuminate the retroreflector jointly or the retroreflector ensemble. The localization units can each be set up to receive at least one reflected light beam from the retroreflector illuminated by the respective localization unit and to generate at least one measurement signal in response to the reflected light beam. The term "measurement signal" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term can, without limitation, refer to any, in particular an electrical, signal, for example a voltage or a current, which has been generated according to the reflected, received light beam or using the reflected, received light beam.

The method includes evaluating the measurement signals of the localization units. The evaluation can take place using at least one evaluation unit. The evaluation unit is set up to determine the position of the jointly illuminated retroreflector or the retroreflector ensemble from the measurement signals of the localization units. The evaluation includes determining a first position of the jointly illuminated retroreflector or the retroreflector ensemble from a measurement signal from a first localization unit that illuminates the jointly illuminated retroreflector or the retroreflector ensemble and a second position of the jointly illuminated retroreflector or the retroreflector ensemble from a Measurement signal from a second localization unit illuminating the jointly illuminated retroreflector or the retroreflector ensemble, so that two positions are determined for the jointly illuminated retroreflector or the retroreflector ensemble. The evaluation can include reconstructing a 3D trajectory of the jointly illuminated retroreflector or the retroreflector ensemble. The evaluation can include performing a multilateration method. The evaluation unit can be set up to carry out at least one multilateration method for determining the 6D information of the illuminated retroreflector. The term "evaluation unit" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a device that is set up to carry out one or more evaluation steps. For example, the evaluation unit can have at least one data processing device, for example at least one computer or microcontroller. The evaluation unit can be designed in particular as a central evaluation unit for the entire measuring device. Alternatively, however, a decentralized evaluation unit with a number of individual components that cooperate with one another is also possible. The evaluation unit can also have at least one user interface, for example at least one keyboard and/or at least one display. The evaluation unit can be set up to record and process the measurement signals from the localization units.

At least one of the retroreflectors is illuminated from different directions in space by at least two of the localization units. Embodiments are conceivable in which at least two of the retroreflectors are illuminated by at least two of the localization units from different directions in space. Embodiments are conceivable in which each of the retroreflectors is illuminated by at least two of the localization units from different directions in space. The joint illumination of at least one of the retroreflectors makes it possible to determine which apparent changes in position of the jointly illuminated retroreflector detected by the localization units Changes in the air column property are due. A change in the refractive index causes the same apparent change in the distance between a retroreflector and two or more localization units lying in different spatial directions. This same apparent change is not physically possible since the retroreflector is only visible at one location, so that changes in distance that occur synchronously on several localization units can only be attributed to fluctuations in the refractive index. When using extremely fast laser tracers, for example with a position detection rate of >1kHz, turbulence influences can also be detected. This is particularly advantageous for the manufacturing environment, since no change in the air column is required for measurement purposes.

Alternatively, a retroreflector ensemble can be illuminated with the illumination light beams from the localization units. A retroreflector ensemble can be understood to mean a group of at least two retroreflectors, the distance between which is small and fixed compared to the air column. The retroreflectors can be illuminated by different locating units, it not being necessary for two locating units to illuminate a common retroreflector. Additional retroreflectors, none of which is illuminated by more than one locating unit, can add bulk to a target including the retroreflectors. For many applications, bulky targets can be unproblematic or even advantageous from a handling point of view, because the limited acceptance angle of the retroreflectors is less limiting on the size of the localization volume covered. The system of equations described below can be solved uniquely if none of the retroreflectors of the ensemble is illuminated simultaneously from opposite directions. The individual retroreflectors of the ensemble can be arranged in a sufficiently time-invariant manner and the localization units can be located opposite one another in such a way that they look into the localization volume from opposite directions.

A plurality of measurement positions can be approached in the method. The method may include aligning the locating units. The method may include changing a relative position of the retroreflectors to the locating units. The air column property can be determined at each of the measurement positions. Thus, a distribution of the air column property can be determined.

Determining the air column property includes a comparison of the first and second positions of the co-illuminated retroreflector or retroreflector ensemble. A substantially identical change in the first and second position is characterized as a change in the air column property. The term "substantially identical" as used herein is a broad term which should be given its ordinary and ordinary meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to the fact that two measured values differ only due to statistical errors within the framework of defined tolerances. In particular, the term can refer to the fact that positions and/or changes in positions, for example in the form of position changes such as changes in distance, only differ due to statistical deviations within defined tolerances. For example, an optical path length between the first localization unit illuminating the jointly illuminated retroreflector and the jointly illuminated retroreflector can be _l1 and an assumed refractive index along the propagation direction of the illuminating light beam can be _n1 . For example, an optical path length between the second localization unit illuminating the jointly illuminated retroreflector and the jointly illuminated retroreflector can be l ₂ and an assumed refractive index along the propagation direction of the illuminating light beam can be n ₂ . For a constant refractive index of the air column, the following applies: $$\mathrm{i.e}x=\mathrm{i.e}{l}_1=-\mathrm{i.e}{l}_2.$$

und $$d{n}_2=\frac{d{l}_2}{l_2}\cdot n_2\approx \frac{d{l}_2}{l_2}.$$

For a variable refractive index of the air column, on the other hand, the following applies: $$\mathrm{i.e}{n}_1=\frac{\mathrm{i.e}{l}_1}{{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="DE102020211136A1\_0009.png,DE102020211136A1\_0011.png"\; state="\{\{state\}\}">l</figure-callout>}}_1}\cdot {\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="DE102020211136A1\_0009.png,DE102020211136A1\_0011.png"\; state="\{\{state\}\}">n</figure-callout>}}_1\approx \frac{\mathrm{i.e}{l}_1}{{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="DE102020211136A1\_0009.png,DE102020211136A1\_0011.png"\; state="\{\{state\}\}">l</figure-callout>}}_1}$$

and $$\mathrm{i.e}{n}_2=\frac{\mathrm{i.e}{l}_2}{l_2}\cdot n_2\approx \frac{\mathrm{i.e}{l}_2}{l_2}.$$

The method can include compensating and/or minimizing an influence of the air column property on a localization accuracy of the multilateration system by compensation calculation taking into account the determined air column property. As used herein, the terms "compensate" and "minimize" are broad terms that should be given their ordinary and current meaning as understood by those skilled in the art. The terms are not limited to any specific or adapted meaning. The terms can, without limitation, refer in particular to taking into account the air column property when determining the position include. For example, the air column property can be taken into account as a systematic error when determining the position. For example, an expected uncertainty of the localizations carried out could be specified and/or an estimated statistic of the accuracy of the localizations carried out.

The method can include acquiring at least one environmental parameter with at least one environmental parameter acquisition unit. The term "environmental parameter" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term can, without limitation, refer to a physical property. The environmental parameters can include, for example, temperature, air pressure and/or air humidity in the working volume. The environmental parameter acquisition unit can have at least one sensor for acquiring an environmental parameter. The sensor can be a temperature sensor and/or a pressure sensor and/or a humidity sensor. Using the environmental parameter detection unit can allow online evaluation according to the Edlen equation. The method may include determining a refractive index distribution for the working volume. Determining the refractive index distribution can include solving the Edlen equation, taking the environmental parameters into account.

The illumination of the respective retroreflector with the illuminating light beam and the receiving of the reflected light beam can take place via open air distances. Alternatively or additionally, fixed and/or temperature-invariant interferometer sections can be provided. The multilateration system can have the fixed and/or temperature-invariant interferometer paths. For example, three fixed interferometer paths can be spanned, for example along the boundary edges of the working volume. A fusion of the evaluations according to the Edlen equation for the environmental parameters, the permanently installed interferometer and the movable interferometric measuring sections of the 6-DOF multilateration can allow the instantaneous refractive index ratios to be calculated, so that online compensation, i.e. during the evaluation, of the influence of refractive index fluctuations is possible.

At least method steps c) and d) can be computer-implemented and/or carried out automatically. The term "computer-implemented," as used herein, is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a method involving at least one computer and/or at least one computer network. The computer and/or the computer network can comprise at least one processor, the processor being set up to carry out at least one method step of the method of the invention. Each of the method steps is preferably carried out by the computer and/or the computer network. The term "automatic" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to a process that is performed entirely by a computer and/or a computer network and/or a machine, in particular without user interaction and/or manual intervention. User interaction may be required to initiate the process and/or individual process steps. The user interaction may include selecting at least one record and/or entering at least one command.

Furthermore, within the scope of the present invention, a computer program is proposed which, when run on a computer or computer network, executes the method according to the invention, in particular steps c) and d) of the method according to the invention, in one of its configurations.

Furthermore, within the scope of the present invention, a computer program with program code means is proposed in order to carry out the method according to the invention, in particular steps c) and d) of the method according to the invention, in one of its configurations when the program is run on a computer or computer network . In particular, the program code means can be stored on a computer-readable data carrier and/or a computer-readable storage medium.

As used herein, the terms "computer-readable data carrier" and "computer-readable storage medium" may refer in particular to non-transitory data storage, for example a hardware data storage medium on which computer-executable instructions are stored. The computer-readable data carrier or the computer-readable storage medium can, in particular, be a storage medium such as an edge be or include om-access memory (RAM) and/or read-only memory (ROM).

In addition, within the scope of the present invention, a data carrier is proposed, on which a data structure is stored which, after loading into a working and/or main memory of a computer or computer network, the method according to the invention, in particular steps c) and d) of the method according to the invention Process can run in one of its configurations.

The present invention also proposes a computer program product with program code means stored on a machine-readable carrier in order to carry out at least steps c) and d) of the method according to the invention in one of its configurations if the program is on a computer or computer network is performed.

A computer program product is understood as the program as a tradable product. In principle, it can be in any form, for example on paper or on a computer-readable data medium, and can be distributed in particular via a data transmission network.

A modulated data signal is also proposed within the scope of the present invention, which contains instructions executable by a computer system or computer network for carrying out the method according to the invention, in particular steps c) and d) of the method according to one of the described embodiments.

In a further aspect of the present invention, an optical navigation system is proposed. The optical navigation system has at least one multilateration system. The multilateration system comprises at least three retroreflectors and at least six localization units or at least six retroreflectors and at least three localization units. The localization units are arranged around the working volume or the retroreflectors are arranged around the localization units. At least two of the localization units are set up to generate at least one illumination light beam each and to illuminate a common retroreflector or a retroreflector ensemble from different spatial directions. The localization units that illuminate the retroreflector together or the retroreflector ensemble are each set up to receive at least one of the light beams reflected by the jointly illuminated retroreflector or the retroreflector ensemble and to generate at least one measurement signal in each case. The optical navigation system has at least one evaluation unit. The evaluation unit is set up to evaluate the measurement signals from the localization units. The evaluation includes determining a first position of the jointly illuminated retroreflector or the retroreflector ensemble from a measurement signal from a first localization unit that illuminates the jointly illuminated retroreflector or the retroreflector ensemble and a second position of the jointly illuminated retroreflector or the retroreflector ensemble from a Measurement signal from a second localization unit illuminating the jointly illuminated retroreflector or the retroreflector ensemble, so that two positions are determined for the jointly illuminated retroreflector or the retroreflector ensemble. The evaluation unit is set up to determine the air column property by comparing the first position and the second position of the jointly illuminated retroreflector or the retroreflector ensemble. A substantially identical change in the first position and the second position is characterized as a change in air column property.

The evaluation unit can be set up to carry out one or more evaluation steps. For example, the evaluation unit can have at least one data processing device, for example at least one computer or microcontroller. The evaluation unit can be designed in particular as a central evaluation unit for the entire optical navigation system. Alternatively, however, a decentralized evaluation unit with a number of individual components that cooperate with one another is also possible. The evaluation unit can also have at least one user interface, for example at least one keyboard and/or at least one display. The evaluation unit can be set up to record and process the measurement signals from the localization units.

The optical navigation system can be set up to carry out a method according to the invention. For further definitions and configurations of the optical navigation system, reference can be made to definitions and configurations of the method for determining a change in at least one air column property.

The optical navigation system can also have at least one control unit. The control unit can be set up to align the localization units relative to the retroreflectors. The control unit can be set up to move to a plurality of measurement positions. At each of the measurement positions, the air column property can be determined. The term "controller" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a device which is set up to control or regulate at least one component or a process. For example, the control unit can have at least one data processing device, for example at least one computer or microcontroller. The control unit can be designed in particular as a central control unit for the entire measuring device. Alternatively, however, a decentralized control unit with a plurality of individual components that cooperate with one another is also possible. The control unit can also have at least one user interface, for example at least one keyboard and/or at least one display. The control unit can be set up to align the localization units relative to the retroreflectors. The control unit can be set up to control or regulate a movement of the localization units.

The evaluation unit can be set up to compensate for and/or minimize an influence of the air column property on a localization accuracy of the multilateration system by means of a compensation calculation, taking into account the determined air column property.

Each of the localization units can have at least one element selected from the group consisting of: a laser tracer; a laser tracker; a LIDAR sensor, preferably an FMCW LIDAR sensor, time-of-flight (TOF) range finder, other range finders, for example based on at least one mode-locked laser.

The visual navigation system can include at least one environmental parameter acquisition unit, which is set up to acquire at least one environmental parameter. The environmental parameter acquisition unit can have at least one sensor for acquiring an environmental parameter. The sensor can be a temperature sensor and/or a pressure sensor and/or a humidity sensor.

The evaluation unit can be set up to determine a refractive index distribution for the working volume. Determining the refractive index distribution can include solving the Edlen equation, taking the environmental parameters into account.

The optical navigation system may include open-air routes and/or fixed and/or temperature-invariant interferometer routes.

The method according to the invention and the device according to the invention have numerous advantages over known devices and methods. Within the scope of high-precision position measurements, it is possible to compensate for fluctuations in air column properties with little complexity in terms of hardware. Hardware that can be used to detect the position of measurement objects can also be used to compensate for the fluctuations in air column properties without additional components. Due to the high position detection rate of optical navigation systems, even turbulence influences can be detected. This can be particularly advantageous for production environments, since the air column no longer needs to be prepared for measurement purposes. All in all, a high accuracy potential of optical position detection systems can be achieved with the method according to the invention and the device according to the invention, even on long measurement paths and with large measurement objects in production environments.

• Ausführungsform 1: Verfahren zum Bestimmen von einer Änderung mindestens einer Luftsäuleneigenschaft in mindestens einem Arbeitsvolumen eines optischen Navigationssystems, wobei das optische Navigationssystem mindestens ein Multilaterationssystem umfassend mindestens drei Retroreflektoren und mindestens sechs Lokalisierungseinheiten oder mindestens sechs Retroreflektoren und mindestens drei Lokalisierungseinheiten aufweist, wobei die Lokalisierungseinheiten um das Arbeitsvolumen herum angeordnet sind oder die Retroreflektoren um die Lokalisierungseinheiten herum angeordnet sind, wobei das Verfahren die folgenden Schritte umfasst:
  1. a) Erzeugen jeweils mindestens eines Beleuchtungslichtstrahls mit mindestens zwei der Lokalisierungseinheiten und Beleuchten eines gemeinsamen Retroreflektors oder eines Retroreflektor-Ensembles aus unterschiedlichen Raumrichtungen mit den Beleuchtungslichtstrahlen der Lokalisierungseinheiten;
  2. b) Empfangen jeweils mindestens eines des von dem gemeinsam beleuchteten Retroreflektor oder dem Retroreflektor-Ensemble reflektierten Lichtstrahls und Erzeugen jeweils mindestens eines Messsignals mit den, den Retroreflektor gemeinsam oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheiten;
  3. c) Auswerten der Messsignale der Lokalisierungseinheiten, wobei das Auswerten ein Bestimmen einer ersten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles aus einem Messsignal einer ersten, den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheit und einer zweiten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles aus einem Messsignal einer zweiten, den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheit umfasst, so dass für den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble zwei Positionen bestimmt werden;
  4. d) Bestimmen der Luftsäuleneigenschaft durch Vergleichen der ersten Position und der zweiten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles, wobei eine im Wesentlichen identische Änderung der ersten Position und der zweiten Position als eine Änderung der Luftsäuleneigenschaft charakterisiert wird.
• Ausführungsform 2: Verfahren nach der vorhergehenden Ausführungsform, wobei das Verfahren ein Kompensieren und/oder Minimieren eines Einflusses der Luftsäuleneigenschaft auf eine Lokalisierungsgenauigkeit des Multilaterationssystems durch Kompensationsrechnung unter Berücksichtigung der bestimmten Luftsäuleneigenschaft umfasst.
• Ausführungsform 3: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei jede der Lokalisierungseinheiten mindestens eine auf Laufzeit- und/oder Interferometrie-Messprinzipien basierende Sensorik aufweist, wobei die Sensorik mindestens ein Element umfasst ausgewählt aus der Gruppe bestehend aus: einem Lasertracer; einem Lasertracker; einem LIDAR-Sensor, bevorzugt einem FMCW-LIDAR-Sensor, Flugzeit (TOF)-Abstandsmesser, andere Abstandsmesser, beispielsweise basierend auf mindestens einem modengekoppelten Laser.
• Ausführungsform 4: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Luftsäuleneigenschaft mindestens eine Eigenschaft umfasst ausgewählt aus der Gruppe bestehend aus: einer Brechzahl; einer Brechzahlverteilung im Arbeitsvolumen; einer Brechzahlschwankung; und einer Turbulenz.
• Ausführungsform 5: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Verfahren ein Erfassen mindestens eines Umgebungsparameters mit mindestens einer Umgebungsparametererfassungseinheit umfasst, wobei die Umgebungsparametererfassungseinheit mindestens einen Sensor zur Erfassung eines Umgebungsparameters aufweist, wobei der Sensor ein Temperatursensor und/oder ein Drucksensor und/oder ein Feuchtesensor ist.
• Ausführungsform 6: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Multilatertionssystem feste und/oder temperaturinvariante Interferometerstrecken aufweist.
• Ausführungsform 7: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei in dem Verfahren eine Mehrzahl von Messpositionen angefahren wird, wobei das Verfahren ein Verändern einer relativen Position der Retroreflektoren zu den Lokalisierungseinheiten umfasst, wobei an jeder der Messpositionen die Luftsäuleneigenschaft bestimmt wird.
• Ausführungsform 10: Optisches Navigationssystem, wobei das optische Navigationssystem mindestens ein Multilaterationssystem aufweist, wobei das Multilaterationssystem mindestens drei Retroreflektoren und mindestens sechs Lokalisierungseinheiten oder mindestens sechs Retroreflektoren und mindestens drei Lokalisierungseinheiten umfasst, wobei die Lokalisierungseinheiten um das Arbeitsvolumen herum angeordnet sind oder die Retroreflektoren um die Lokalisierungseinheiten herum angeordnet sind, wobei mindestens zwei der Lokalisierungseinheiten eingerichtet sind jeweils mindestens einen Beleuchtungslichtstrahl zu erzeugen und einen gemeinsamen Retroreflektor oder ein Retroreflektor-Ensemble aus unterschiedlichen Raumrichtungen zu beleuchten, wobei die den Retroreflektor gemeinsam oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheiten eingerichtet sind jeweils mindestens einen des von dem gemeinsam beleuchteten Retroreflektor oder dem Retroreflektor-Ensemble reflektierten Lichtstrahl zu empfangen und jeweils mindestens ein Messsignal zu erzeugen, wobei das optische Navigationssystem mindestens eine Auswerteeinheit aufweist, wobei die Auswerteeinheit eingerichtet ist, um die Messsignale der Lokalisierungseinheiten auszuwerten, wobei das Auswerten ein Bestimmen einer ersten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles aus einem Messsignal einer ersten, den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheit und einer zweiten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles aus einem Messsignal einer zweiten, den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheit umfasst, so dass für den gemeinsam beleuchteten Retroreflektor oder das Retroreflektor-Ensemble zwei Positionen bestimmt werden, wobei die Auswerteeinheit eingerichtet ist, um die Luftsäuleneigenschaft durch Vergleichen der ersten Position und er zweiten Position des gemeinsam beleuchteten Retroreflektors oder des Retroreflektor-Ensembles zu bestimmen, wobei eine im Wesentlichen identische Änderung der ersten Position und der zweiten Position als eine Änderung der Luftsäuleneigenschaft charakterisiert wird.
• Ausführungsform 11: Optisches Navigationssystem nach der vorhergehenden Ausführungsform, wobei das optische Navigationssystem eingerichtet ist ein Verfahren nach einer der vorhergehenden Ausführungsformen durchzuführen.
• Ausführungsform 12: Optisches Navigationssystem nach einer der vorhergehenden, ein optisches Navigationssystem betreffenden, Ausführungsformen, wobei das optische Navigationssystem weiterhin mindestens eine Steuereinheit aufweist, wobei die Steuereinheit eingerichtet ist, die Lokalisierungseinheiten relativ zu den Retroreflektoren auszurichten, wobei die Steuereinheit eingerichtet ist eine Mehrzahl von Messpostionien anzufahren, wobei an jeder der Messpositionen die Luftsäuleneigenschaft bestimmt wird.
• Ausführungsform 13: Optisches Navigationssystem nach einer der vorhergehenden, ein optisches Navigationssystem betreffenden, Ausführungsformen, wobei die Auswerteeinheit eingerichtet ist zu einem Kompensieren und/oder Minimieren eines Einflusses der Luftsäuleneigenschaft auf eine Lokalisierungsgenauigkeit des Multilaterationssystems durch Kompensationsrechnung unter Berücksichtigung der bestimmten Luftsäuleneigenschaft.
• Ausführungsform 14: Optisches Navigationssystem nach einer der vorhergehenden, ein optisches Navigationssystem betreffenden Ausführungsformen, wobei jede der Lokalisierungseinheiten mindestens ein Element aufweist ausgewählt aus der Gruppe bestehend aus: einem Lasertracer; einem Lasertracker; einem LIDAR-Sensor, bevorzugt einem FMCW-LIDAR-Sensor.
• Ausführungsform 15: Optisches Navigationssystem nach einer der vorhergehenden, ein optisches Navigationssystem betreffenden Ausführungsformen, wobei das optische Navigationssystem mindestens eine Umgebungsparametererfassungseinheit umfasst, welche eingerichtet ist, um mindestens einen Umgebungsparameter zu erfassen, wobei die Umgebungsparametererfassungseinheit mindestens einen Sensor zur Erfassung eines Umgebungsparameters aufweist, wobei der Sensor ein Temperatursensor und/oder ein Drucksensor und/oder ein Feuchtesensor ist.
• Ausführungsform 16: Optisches Navigationssystem nach der vorhergehenden Ausführungsform, wobei die Auswerteeinheit eingerichtet ist, um eine Brechzahlverteilung für das Arbeitsvolumen zu bestimmen, wobei das Bestimmen der Brechzahlverteilung ein Lösen der Edlen-Gleichung unter Berücksichtigung der Umgebungsparameter umfasst.
• Ausführungsform 17: Optisches Navigationssystem nach einer der vorhergehenden, ein optisches Navigationssystem betreffenden Ausführungsformen, wobei das optische Navigationssystem Freiluftstrecken und/oder feste und/oder temperaturinvariante Interferometerstrecken umfasst.
• Ausführungsform 18: Computerprogramm mit Programmcode-Mitteln, um ein Verfahren nach einer der vorhergehenden, ein Verfahren betreffenden, Ausführungsformen, insbesondere mindestens Schritte c) und d) des Verfahrens, durchzuführen, wenn das Programm auf einem Computer oder einem Computer-Netzwerk ausgeführt wird.

In summary, the following embodiments are proposed without restricting further possible configurations:

• Embodiment 1: Method for determining a change in at least one air column property in at least one working volume of an optical navigation system, the optical navigation system having at least one multilateration system comprising at least three retroreflectors and at least six localization units or at least six retroreflectors and at least three localization units, the localization units being working volumes are arranged around or the retroreflectors are arranged around the localization units, the method comprising the following steps:
  1. a) generating in each case at least one illuminating light beam with at least two of the localization units and illuminating a common retroreflector or a retroreflector ensemble from different spatial directions with the illuminating light beams of the localization units;
  2. b) receiving in each case at least one of the light beams reflected by the jointly illuminated retroreflector or the retroreflector ensemble and generating in each case at least one measurement signal with the retroreflector localization units illuminating together or the retroreflector ensemble;
  3. c) Evaluation of the measurement signals of the localization units, the evaluation determining a first position of the jointly illuminated retroreflector or of the retroreflector ensemble from a measurement signal of a first localization unit illuminating the jointly illuminated retroreflector or the retroreflector ensemble and a second position of the jointly illuminated retroreflector or the retroreflector ensemble from a measurement signal from a second localization unit illuminating the jointly illuminated retroreflector or the retroreflector ensemble, so that two positions are determined for the jointly illuminated retroreflector or the retroreflector ensemble;
  4. d) determining the air column property by comparing the first position and the second position of the co-illuminated retroreflector or retroreflector ensemble, wherein a substantially identical change in the first position and the second position is characterized as a change in the air column property.
• Embodiment 2 Method according to the preceding embodiment, wherein the method comprises compensating for and/or minimizing an influence of the air column property on a localization accuracy of the multilateration system by compensation calculation taking into account the determined air column property.
• Embodiment 3: Method according to one of the preceding embodiments, wherein each of the localization units has at least one sensor system based on transit time and/or interferometry measurement principles, the sensor system comprising at least one element selected from the group consisting of: a laser tracer; a laser tracker; a LIDAR sensor, preferably an FMCW LIDAR sensor, time-of-flight (TOF) range finder, other range finders, for example based on at least one mode-locked laser.
• Embodiment 4: Method according to one of the preceding embodiments, wherein the air column property comprises at least one property selected from the group consisting of: a refractive index; a refractive index distribution in the working volume; a refractive index variation; and a turbulence.
• Embodiment 5: Method according to one of the preceding embodiments, wherein the method comprises detecting at least one environmental parameter with at least one environmental parameter detection unit, the environmental parameter detection unit having at least one sensor for detecting an environmental parameter, the sensor being a temperature sensor and/or a pressure sensor and/or a humidity sensor is.
• Embodiment 6 Method according to one of the preceding embodiments, in which the multilatertion system has fixed and/or temperature-invariant interferometer paths.
• Embodiment 7 Method according to one of the preceding embodiments, wherein in the method a plurality of measurement positions are approached, the method comprising changing a position of the retroreflectors relative to the localization units, the air column property being determined at each of the measurement positions.
• Embodiment 10: Optical navigation system, wherein the optical navigation system has at least one multilateration system, wherein the multilateration system comprises at least three retroreflectors and at least six localization units or at least six retroreflectors and at least three localization units, the localization units being arranged around the working volume or the retroreflectors around the localization units are arranged around it, with at least two of the localization units each being set up to generate at least one illuminating light beam and to illuminate a common retroreflector or a retroreflector ensemble from different spatial directions, the localization units which illuminate the retroreflector together or the retroreflector ensemble being set up in each case at least one of the Li reflected by the co-illuminated retroreflector or retroreflector ensemble to receive a light beam and to generate at least one measurement signal in each case, the optical navigation system having at least one evaluation unit, the evaluation unit being set up to evaluate the measurement signals of the localization units, the evaluation involving a determination of a first position of the jointly illuminated retroreflector or of the retroreflector ensemble from a measurement signal from a first localization unit illuminating the commonly illuminated retroreflector or retroreflector ensemble and a second position of the commonly illuminated retroreflector or retroreflector ensemble from a measurement signal of a second localization unit that illuminates the jointly illuminated retroreflector or the retroreflector ensemble, so that two positions are determined for the jointly illuminated retroreflector or the retroreflector ensemble, the evaluation unit being set up to determine the air column property by comparing the first position and determine the second position of the co-illuminated retroreflector or retroreflector ensemble, wherein a substantially identical change in the first position and the second position is characterized as a change in air column property.
• Embodiment 11 Optical navigation system according to the preceding embodiment, wherein the optical navigation system is set up to carry out a method according to one of the preceding embodiments.
• Embodiment 12: Optical navigation system according to one of the preceding embodiments relating to an optical navigation system, the optical navigation system also having at least one control unit, the control unit being set up to align the localization units relative to the retroreflectors, the control unit being set up for a plurality of measuring positions approach, the air column property being determined at each of the measurement positions.
• Embodiment 13: Optical navigation system according to one of the preceding embodiments relating to an optical navigation system, wherein the evaluation unit is set up to compensate and/or minimize an influence of the air column property on a localization accuracy of the multilateration system by compensation calculation taking into account the determined air column property.
• Embodiment 14: Optical navigation system according to one of the preceding embodiments relating to an optical navigation system, wherein each of the localization units has at least one element selected from the group consisting of: a laser tracer; a laser tracker; a LIDAR sensor, preferably an FMCW LIDAR sensor.
• Embodiment 15: Optical navigation system according to one of the preceding embodiments relating to an optical navigation system, wherein the optical navigation system comprises at least one environmental parameter acquisition unit, which is set up to acquire at least one environmental parameter, wherein the environmental parameter acquisition unit has at least one sensor for acquiring an environmental parameter, wherein the Sensor is a temperature sensor and/or a pressure sensor and/or a humidity sensor.
• Embodiment 16 Optical navigation system according to the previous embodiment, wherein the evaluation unit is set up to determine a refractive index distribution for the working volume, wherein the determination of the refractive index distribution includes solving the Edlen equation taking into account the environmental parameters.
• Embodiment 17: Optical navigation system according to one of the preceding embodiments relating to an optical navigation system, wherein the optical navigation system comprises open-air links and/or fixed and/or temperature-invariant interferometer links.
• Embodiment 18: Computer program with program code means to carry out a method according to one of the preceding embodiments relating to a method, in particular at least steps c) and d) of the method, when the program is executed on a computer or a computer network.

character list

Further details and features emerge from the following description of exemplary embodiments, in particular in connection with the dependent claims. The respective features can be implemented individually or in combination with one another. The invention is not limited to the exemplary embodiments. The exemplary embodiments are shown schematically in the figures. The same reference numerals in the individual figures designate elements that are the same or have the same function or that correspond to one another in terms of their functions.

• 1 eine schematische Darstellung für ein Bestimmen einer Änderung einer Luftsäuleneigenschaft in einem Arbeitsvolumen;
• 2 eine schematische Darstellung einer Ausführungsform eines erfindungsgemäßen optischen Navigationssystems;
• 3 ein Flussdiagramm eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens;
• 4 eine schematische Darstellung einer weiteren Ausführungsform des erfindungsgemäßen optischen Navigationssystems; und
• 5 eine schematische Darstellung einer weiteren Ausführungsform des erfindungsgemäßen optischen Navigationssystems.

Show in detail:

• 1 a schematic representation for determining a change in an air column property in a working volume;
• 2 a schematic representation of an embodiment of an optical navigation system according to the invention;
• 3 a flowchart of an embodiment of a method according to the invention;
• 4 a schematic representation of a further embodiment of the optical navigation system according to the invention; and
• 5 a schematic representation of a further embodiment of the optical navigation system according to the invention.

Description of the exemplary embodiments

1 shows a schematic representation for determining a change in an air column property 110 in a working volume 112 of an optical navigation device 114.

wobei K, D und g zwei Faktoren beschrieben in Bönsch, G. and E. Potulski (1998), „Measurement of the refractive index of air and comparison with modified Edlen's formulae“, IOP Metrologia, Volume 35, No. 2, pp. 133-139, t die Temperatur, p der Druck, x der CO₂ Anteil und p_ω der Partialdruck von Wasserdampf ist. Die Änderung der Luftsäuleneigenschaft 110 kann eine Variation und/oder Schwankung der Luftsäuleneigenschaft 110 entlang einer Messstrecke 118 umfassen. Die Luftsäuleneigenschaft 110 entlang der Messstrecke 118 kann räumlich und/oder zeitlich inhomogen sein, beispielsweise können Brechzahlschwankungen auftreten. Beispielsweise können auch Turbulenzen, also räumlich und zeitlich variierende Verwirbelungen, auftreten.The air column property 110 can include at least one physical property, in particular an optical property, of the air column 116 . In particular, the air column property 110 may include at least one property selected from the group consisting of: a refractive index; a refractive index distribution in the working volume; a refractive index variation; and a turbulence. The so-called Edlen equation can be used to determine the refractive index n in air: $$n\left(\lambda ,t,p,x,p_{\omega }\right)-1=K\left(\lambda \right)D\left(t,p,x\right)-p_{\omega }G\left(\lambda \right),$$

where K, D and g are two factors described in Bönsch, G. and E. Potulski (1998), "Measurement of the refractive index of air and comparison with modified Edlen's formulae", IOP Metrologia, Volume 35, No. 2, pp. 133-139, t is the temperature, p is the pressure, x is the proportion of CO ₂ and p _{ω is} the partial pressure of water vapour. The change in the air column property 110 may include a variation and/or fluctuation in the air column property 110 along a measurement path 118 . The air column property 110 along the measurement section 118 can be spatially and/or temporally inhomogeneous, for example refractive index fluctuations can occur. For example, turbulence, i.e. spatially and temporally varying turbulence, can also occur.

As in 1 shown, at least one retroreflector 124 is illuminated by at least two localization units 126 from different directions in space. The retroreflector 124 and the localization units 126 can be part of an optical navigation system 114 comprising at least one multilateration system 122 .

The retroreflector 124 can be any device that reflects a light beam 128 in the direction from which the light beam 128 arrived. For example, the retroreflector 124 can be a marker. For example, retroreflector 124 may be selected from the group consisting of: a cat's eye; a cat's eye with a reflective layer; a marker described in U.S. 2011/0007326 A1 , U.S. 2013/0050410 A1 or US 2017/0258531 A1 , the content of which is hereby incorporated into this application; a cube prism; a corner cube.

The localization unit 126 can basically be any device that is set up to generate at least one piece of localization information. The localization information can be selected from at least one piece of information from the group consisting of: a measurement signal depending on the location of the retroreflector 124 illuminated by the localization unit 126; information about a distance from the retroreflector 124 illuminated by the localization unit 126 to the localization unit 126; information about a distance from the retroreflector 124 illuminated by the localization unit 126 to the localization unit 126; information about a position of the retroreflector 124 illuminated by the localization unit 126 relative to the localization unit 126; and information about a change in length.

The localization units 126 can have at least one sensor system based on transit time and/or interferometry measurement principles. The localization units 126 can each comprise at least one element selected from the group consisting of: a laser tracer; a laser tracker; a LIDAR sensor, preferably an FMCW LIDAR sensor, time-of-flight (TOF) range finder, other range finders based on a mode-locked laser, for example.

The laser tracer can be any measuring device that is set up to determine a distance, in particular a change in distance, to a retroreflector 124 interferometrically. The laser tracer can be configured to track a position of the retroreflector 124 at different points in time. The laser tracer can be set up to follow a retroreflector 124 moving in space by means of a laser beam. The change in distance can be measured incrementally. The laser tracer can be an incremental measuring system with a large field of view, in particular a large pivoting range of a laser beam direction. For example, at least two consecutive measurements may be required to measure the change in distance. The laser tracer can cover a large angular range. For example, the laser beam of the laser tracer can be pivoted in the large angular range.

The laser tracker can be any measuring device that is set up to determine a distance and/or a direction of a retroreflector 124 interferometrically, in particular relative to axes defined by an optomechanics of the laser tracker.

The LIDAR sensor can be any device based on the LIDAR ("light detection and ranging") measurement principle, also called LADAR (laser detection and ranging). In particular, the LIDAR sensor can be set up to generate and receive a light beam 128, for example a laser beam, in particular the light beam 128 previously emitted by it and reflected back to it, and from this to establish a distance between the LIDAR sensor and the retroreflector 124 determine, for example by exploiting differences in return times and wavelengths. The localization unit 126 can preferably have an FMCW LIDAR sensor. The FMCW LIDAR sensor can be set up to generate the light beam 128, the frequency of which is continuously tuned according to the FMCW method. For example, the frequency of light beam 128 may be linearly modulated with time. A combination of LIDAR methods and FMCW methods are known in principle to those skilled in the art, for example from Chip-scale Lidar, Benham Behroozpur Baghmisheh, Technical Report no. UCB/EECS.2017-4. For example, the LIDAR unit as in U.S. 9,559,486 B2 , U.S. 8,913,636 B2 or U.S. 2016/123718 A1 be designed. FMCW LIDAR sensors are more robust and less expensive than laser tracers. Furthermore, the FMCW LIDAR sensors can be insensitive to so-called line-of-sight interruptions, since they are absolute measuring systems. Furthermore, hybrid systems can be used with the addition of mode-locked lasers.

The joint illumination of at least one of the retroreflectors 124 makes it possible to determine which apparent position changes of the jointly illuminated retroreflector 124 determined by the localization units 126 are due to changes in the air column property 110 . A change in the refractive index causes the same apparent change in the distance between a retroreflector 124 and two or more localization units 126 located in different spatial directions. This same apparent change is physically impossible, since the retroreflector 124 is only visible at one location, so that such changes in distance , which occur synchronously on several localization units 126 can only be attributed to fluctuations in the refractive index. An optical path length between the first localization unit 136 illuminating the co-illuminated retroreflector 124 and the co-illuminated retroreflector 124 may be l ₁ and an assumed refractive index along the direction of propagation of an illuminating light beam 148 may be n ₁ . For example, an optical path length between the second localization unit 138 illuminating the co-illuminated retroreflector 124 and the co-illuminated retroreflector 124 may be l ₂ and an assumed refractive index along the direction of propagation of the illuminating light beam 148 may be n ₂ . For a constant refractive index of the air column 116, the following applies: $$\mathrm{i.e}x=\mathrm{i.e}{l}_1=-\mathrm{i.e}{l}_2.$$

und $$d{n}_2=\frac{d{l}_2}{l_2}\cdot n_2\approx \frac{d{l}_2}{l_2}.$$

For a variable refractive index of the air column 116, however, the following applies: $$\mathrm{i.e}{n}_1=\frac{\mathrm{i.e}{l}_1}{{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="DE102020211136A1\_0009.png,DE102020211136A1\_0011.png"\; state="\{\{state\}\}">l</figure-callout>}}_1}\cdot {\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="DE102020211136A1\_0009.png,DE102020211136A1\_0011.png"\; state="\{\{state\}\}">n</figure-callout>}}_1\approx \frac{\mathrm{i.e}{l}_1}{{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="DE102020211136A1\_0009.png,DE102020211136A1\_0011.png"\; state="\{\{state\}\}">l</figure-callout>}}_1}$$

and $$\mathrm{i.e}{n}_2=\frac{\mathrm{i.e}{l}_2}{l_2}\cdot n_2\approx \frac{\mathrm{i.e}{l}_2}{l_2}.$$

By evaluating the measurement signals from localization units 126, a first position of the jointly illuminated retroreflector 124 can be determined from a measurement signal from the first localization unit 136, which illuminates the jointly illuminated retroreflector 124, and a second position of the jointly illuminated retroreflector 124 can be determined from a measurement signal from the second, jointly illuminated retroreflector 124 illuminating, localization unit 138 take place, so that two positions are determined for the jointly illuminated retroreflector 124. Determining the air column property 110 includes a comparison of the first and second positions of the co-illuminated retroreflector 124. A substantially identical change in the first and second positions is characterized as a change in the air column property 110. FIG. When using extremely fast laser tracers, for example with a position detection rate of >1kHz, turbulence influences can also be detected. This is particularly advantageous for the manufacturing environment, since no change in the air column is required for measurement purposes.

Illumination light beam 148 may include any light beam 128 that is emitted and/or transmitted to illuminate retroreflector 124 . In particular, the illuminating light beam 148 can be a light beam 128 generated by one of the localization units 126 for illuminating one of the retroreflectors 124 . The localization units 126 can each have at least one lighting unit. The lighting unit can have a light source, in particular a laser source. The light beam 128 may include an amount of light which is emitted and/or sent out in a certain direction.

An exemplary embodiment of an optical navigation system 114 is described, for example, in 2 shown. The optical navigation system 114 can include a technical system that is set up for optical position determination. The optical navigation system 114 can be set up to calibrate at least one precision machine, in particular a coordinate measuring machine or a processing machine. The optical position determination can include determining at least one spatial position and/or orientation. The spatial position and/or the orientation can be determined in a coordinate system, for example a Cartesian coordinate system or a spherical coordinate system. Other coordinate systems are also conceivable. An origin or zero point of the coordinate system can be in a point of the optical navigation system 114 . The spatial position may include a three-dimensional point (X, Y, Z) in the coordinate system. The spatial position can be defined by the location coordinates X, Y and Z. The orientation can include a rotation of the measurement object 120, in particular an angular position. The orientation can be specified by at least three angles, for example Euler angles or pitch angles, roll angles and yaw angles. The spatial position and orientation together can also be referred to as six-dimensional information or 6D information.

The optical navigation system 114 includes the at least one multilateration system 122. The multilateration system 122 includes at least three retroreflectors 124 and at least six localization units 126 or at least six retroreflectors 124 and at least three localization units 126. In the exemplary embodiment of 2 the multilateration system includes seven localization units. The multilateration system 122 can be set up to carry out a 6 DoF multilateration. A relative position, in particular a spatial position and/or a distance between the retroreflectors 124 and/or a relative position, in particular a spatial position and/or a distance between the localization units 126 can be known. For example, the retroreflectors 124 may be arranged in a plane in the shape of a triangle. The lengths of the sides of the triangle can be known. Provided that the position of the retroreflectors 124 relative to one another is known, 3D trajectories of all three retroreflectors 124, or a 6D trajectory of a system of retroreflectors 124, can be reconstructed from a sequence of length changes measured with the localization units 126.

The multilateration system 122 can be a self-calibrating multilateration system 122 . If three retroreflectors 124 and at least six localization units 126 are used, the localization units 126 and the retroreflectors can be arranged and/or aligned with one another in one of the following configurations: two localization units 126 on a first retroreflector 130, two localization units 126 on a second retroreflector 132 and two locating units 126 to a third retroreflector 134 (two-two-two); four locating units 126 to the first retroreflector 130, one locating unit 126 to the second retroreflector 132, and one locating unit 126 to the third retroreflector 134 (four-one-one); three locating units 126 on the first retroreflector 130, two locating units 126 on the second retroreflector 132, and one locating unit 126 on the third retroreflector 134 (three-two-one).

For example, as in 2 As shown, the optical navigation system 114 includes three retroreflectors 124, such as the first retroreflector 130, the second retroreflector 132, and the third retroreflector 134. For example, the retroreflectors 124 may be arranged in a plane in the shape of a triangle. The lengths of the sides of the triangle can be known. Provided that the position of the retroreflectors 124 relative to one another is known, 3D trajectories of all three retroreflectors 124, or a 6D trajectory of a system of retroreflectors 124, can be reconstructed from a sequence of length changes measured with the localization units 126. The Retroreflectors 124, in 2 shown as circles, can be arranged on a measurement object 120 and the localization units 126, in 2 shown as crosses can be arranged in space. In this embodiment, the optical navigation system 114 can have seven localization units 126, for example a first localization unit 136, a second localization unit 138, a third localization unit 140, a fourth localization unit 142, a fifth localization unit 144, a sixth localization unit 146 and a seventh localization unit 147. The first locating unit 136, second locating unit 138 may be aligned with, also referred to as locked onto, third retroreflector 134 and illuminate it. The third localization unit 140 and the fourth localization unit 142 may be aligned with and illuminate the second retroreflector 132 . The first retroreflector 130 can of the fifth Localization unit 144 and the sixth localization unit 146 be illuminated. This corresponds to the configuration two-two-two. The seventh localization unit 147 can also illuminate the third retroreflector 134 . At least two localization units 126 thus follow the same retroreflector 124 and can carry out a distance measurement between localization unit 126 and retroreflector 124 in each case. Thus, more distance measurements can be carried out than spatial coordinates have to be determined. After a certain number of distance measurements, the position of the localization units 126 relative to one another can be determined. Such a multilateration system 122 is referred to as self-calibrating.

The localization units 126 are arranged around the working volume 112 or the retroreflectors 124 are arranged around the localization units 126 . In 2 the localization units 126 are arranged around the working volume 112 . The working volume 112 can include a volume in which the optical position determination can take place. The retroreflectors 124 can span and/or define the working volume 112 together with the localization units 126 . The working volume 112 can be determined by a measurement range of the optical navigation device 114, ie a range in which the optical position determination can take place within specified limits. The working volume 112 may be a 6 (Degree of Freedom) DOF tracking volume. The retroreflectors 124 can be illuminated from the outside in by the localization units 126 . Alternatively, the localization units 126 can illuminate the retroreflectors 124 from the inside out. The retroreflectors 124 can be arranged on a measurement object 120 and the localization units 126 can be arranged in space and/or the localization units 126 can be arranged on the measurement object 120 and the retroreflectors 124 can be arranged in space. The retroreflectors 124 may be widely spaced. The retroreflectors 124 may be arranged such that they are widely spaced within the working volume 112 . Localization units 126 can each have a holder for arranging, setting up and/or fastening localization units 126. Retroreflectors 124 can also each have at least one holder for arranging, setting up and/or fastening retroreflectors 124. Measurement object 120 can have any shape include measured object. For example, the measurement object 120 can also be a measuring head of a sensor or a tool with which a component can be scanned.

The visual navigation system 114 can, as in 2 shown, furthermore have at least one evaluation unit 158. The evaluation unit 158 is set up to determine the position of the jointly illuminated retroreflector 124 from the measurement signals of the localization units 126 . The evaluation comprises determining a first position of the jointly illuminated retroreflector 124 from a measurement signal from a first localization unit 126 that illuminates the jointly illuminated retroreflector 124, and a second position of the jointly illuminated retroreflector 124 from a measurement signal from a second localization unit that illuminates the jointly illuminated retroreflector 124. Locating unit 126 so that two positions are determined for the jointly illuminated retroreflector 124. The evaluating may include reconstructing a 3D trajectory of the co-illuminated retroreflector 124 . The evaluation can include carrying out a multilateration method. The evaluation unit 158 can be set up to carry out at least one multilateration method for determining the 6D information of the illuminated retroreflector 124 . The evaluation unit 158 can include a device which is set up to carry out one or more evaluation steps. For example, the evaluation unit 158 can have at least one data processing device, for example at least one computer or microcontroller. The evaluation unit 158 can be designed in particular as a central evaluation unit 158 for the entire measuring device. Alternatively, however, a decentralized evaluation unit 158 with a plurality of individual components that cooperate with one another is also possible. The evaluation unit 158 can also have at least one user interface, for example at least one keyboard and/or at least one display. The evaluation unit 158 can be set up to record and process the measurement signals from the localization units 126 .

The visual navigation system 114 can, as in 2 shown, further comprise at least one control unit 160. The control unit 160 can be set up to align the localization units 126 relative to the retroreflectors 124 . The control unit 160 can be set up to move to a plurality of measurement positions. The air column properties 110 can be determined at each of the measurement positions. The control unit 160 can include a device that is set up to control or regulate at least one component or one process. For example, the control unit 160 can have at least one data processing device, for example at least one computer or microcontroller. The control unit 160 can in particular act as a central control unit 160 for the entire measuring device be designed. Alternatively, however, a decentralized control unit 160 with a plurality of individual components that cooperate with one another is also possible. The control unit 160 can furthermore have at least one user interface, for example at least one keyboard and/or at least one display. The control unit 160 can be set up to align the localization units 126 relative to the retroreflectors 124 . The control unit 160 can be set up to control or regulate a movement of the localization units 124 .

1. a) Erzeugen jeweils mindestens eines Beleuchtungslichtstrahls 148 mit mindestens zwei der Lokalisierungseinheiten 126 und Beleuchten eines gemeinsamen Retroreflektors 124 oder eines Retroreflektor-Ensembles aus unterschiedlichen Raumrichtungen mit den Beleuchtungslichtstrahlen 148 der Lokalisierungseinheiten 126;
2. b) Empfangen jeweils mindestens eines des von dem gemeinsam beleuchteten Retroreflektor oder dem Retroreflektor-Ensemble reflektierten Lichtstrahls 128 und Erzeugen jeweils mindestens eines Messsignals mit den, den Retroreflektor 124 gemeinsam oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheiten 126;
3. c) Auswerten der Messsignale der Lokalisierungseinheiten 126, wobei das Auswerten ein Bestimmen einer ersten Position des gemeinsam beleuchteten Retroreflektors 124 oder des Retroreflektor-Ensembles aus einem Messsignal einer ersten, den gemeinsam beleuchteten Retroreflektor 124 oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheit 126 und einer zweiten Position des gemeinsam beleuchteten Retroreflektors 124 oder des Retroreflektor-Ensembles aus einem Messsignal einer zweiten, den gemeinsam beleuchteten Retroreflektor 124 oder das Retroreflektor-Ensemble beleuchtenden, Lokalisierungseinheit 126 umfasst, so dass für den gemeinsam beleuchteten Retroreflektor 124 oder das Retroreflektor-Ensemble zwei Positionen bestimmt werden;
4. d) Bestimmen der Luftsäuleneigenschaft 110 durch Vergleichen der ersten Position und der zweiten Position des gemeinsam beleuchteten Retroreflektors 124 oder des Retroreflektor-Ensembles, wobei eine im Wesentlichen identische Änderung der ersten Position und der zweiten Position als eine Änderung der Luftsäuleneigenschaft 110 charakterisiert wird.

3 shows a flow chart of an embodiment of the method according to the invention. The procedure includes the following steps:

1. a) generating at least one illumination light beam 148 with at least two of the localization units 126 and illuminating a common retroreflector 124 or a retroreflector ensemble from different spatial directions with the illumination light beams 148 of the localization units 126;
2. b) receiving in each case at least one of the light beams 128 reflected by the jointly illuminated retroreflector or the retroreflector ensemble and generating in each case at least one measurement signal with the localization units 126 which illuminate the retroreflector 124 jointly or the retroreflector ensemble;
3. c) Evaluating the measurement signals from localization units 126, with the evaluation determining a first position of the jointly illuminated retroreflector 124 or of the retroreflector ensemble from a measurement signal from a first localization unit 126, which illuminates the jointly illuminated retroreflector 124 or the retroreflector ensemble, and from a second Position of the jointly illuminated retroreflector 124 or the retroreflector ensemble from a measurement signal from a second localization unit 126 that illuminates the jointly illuminated retroreflector 124 or the retroreflector ensemble, so that two positions are determined for the jointly illuminated retroreflector 124 or the retroreflector ensemble ;
4. d) determining the air column property 110 by comparing the first position and the second position of the co-illuminated retroreflector 124 or retroreflector ensemble, wherein a substantially identical change in the first position and the second position is characterized as a change in the air column property 110.

3 shows a schematic representation of the method, wherein reference number 150 denotes method step a), wherein reference number 152 denotes method step b), wherein reference number 154 denotes method step c) and wherein reference number 156 denotes method step d). At least method step c) 154 and method step d) 156 can be computer-implemented and/or carried out automatically. The method steps can be carried out in the order given, with one or more of the steps being able to be carried out at least partially simultaneously and with one or more of the steps being able to be repeated several times. In addition, other steps, whether or not mentioned in the present application, can additionally be carried out.

The method comprises receiving, reference numeral 152, at least one of the light beams 128 reflected by the jointly illuminated retroreflector 124 or the retroreflector ensemble and generating at least one measurement signal with the localization units 126 that illuminate the retroreflector 124 jointly or the retroreflector ensemble. The localization units 126 can each be set up to receive at least one reflected light beam 128 from the retroreflector 124 illuminated by the respective localization unit 126 and to generate at least one measurement signal in response to the reflected light beam 128 . The measurement signal can include any desired, in particular an electrical, signal, for example a voltage or a current, which was generated according to the reflected, received light beam 128 or using the reflected, received light beam 128 . The method includes an evaluation, reference number 154, of the measurement signals of the localization units 126. The evaluation can be carried out using the at least one evaluation unit 158.

The method can include compensating for and/or minimizing an influence of the air column property 110 on a localization accuracy of the multilateration system 122 by compensation calculation taking into account the determined air column property 110 . Compensating and minimizing may include considering the air column property 110 when determining the position. For example, the air column property 110 can be taken into account as a systematic error when determining the position. For example, an expected uncertainty of the localizations carried out could be specified and/or an estimated statistic of the accuracy of the localizations carried out. The evaluation unit 158 can be set up to compensating for and/or minimizing an influence of the air column property 110 on a localization accuracy 126 of the multilateration system 122 by compensation calculation taking into account the determined air column property 110.

A plurality of measurement positions can be approached in the method. The method may include aligning the locating units 126 . The method may include changing a relative position of the retroreflectors 124 to the locating units 126 . The air column property 110 can be determined at each of the measurement positions. In this way, a distribution of the air column property 110 can be determined.

4 shows a further embodiment of the optical navigation system 114 according to the invention, in particular an arrangement of one of the retroreflectors 124 and these illuminating localization units 126. The optical navigation system 114 can include open-air routes and/or fixed and/or temperature-invariant interferometer routes. Temperature-invariant connection designs 172 are in 4 denoted by paired parallel dashed lines within the working volume 112 and solid lines denote open-air stretches. 4 shows a schematic representation of a temperature-invariant connection structure 172 for interferometric measurement sections 118 along boundary edges of a working volume 112. The working volume 112 is in 4 marked by dashed border lines. The localization units 126 and the retroreflector 124 are in 4 connected to one another by a temperature-invariant connecting structure 172, the measuring sections 118 being designed as open-air sections.

5 shows a further embodiment of the optical navigation system 114 according to the invention, in particular an arrangement of one of the retroreflectors 124 and these illuminating localization units 126. Temperature-invariant connection structures 172 are in 5 denoted by paired parallel dashed lines within the working volume 112 and solid lines denote open-air stretches. The visual navigation system 114 can include at least one environmental parameter acquisition unit 162, which is set up to acquire at least one environmental parameter. The environmental parameter acquisition unit 162 can have at least one sensor 164 for acquiring an environmental parameter. The environmental parameters can include temperature, air pressure and/or humidity in the working volume 112, for example. The sensor 164 can be a temperature sensor 166 and/or a pressure sensor 168 and/or a humidity sensor 170 . Ambient parameter detection units 162 are shown along the measurement sections 118 . Ti with i=1 to 6 refers to the measured temperature of the i-th temperature sensor 166, Pi with i=1 to 6 to the measured pressure of the respective pressure sensor 168 and Hi with i=1 to 6 to the measured humidity of the respective humidity sensor 170

The overdetermination within the multilateration system 122, with which a large number of measuring positions was approached, can be used to solve the Edlen equation, taking into account the data from temperature sensors 166, pressure sensors 168 and humidity sensors 170 distributed over temperature-invariant interferometric measuring sections 172, so that an approximate refractive index distribution for the working volume 112 of the multilateration system 122 can be determined. This can be used in order to minimize the error effect of changes in the air column properties 110 on the localization accuracy of the multilateration system 122 through compensation calculation.

Reference List

110

air column property

112

volume of work

114

Optical navigation system

116

air column

118

measuring section

120

measurement object

122

multilateration system

124

retroreflector

126

localization unit

128

beam of light

130

First retroreflector

132

Second retroreflector

134

Third retroreflector

136

First localization unit

138

Second localization unit

140

Third localization unit

142

Fourth localization unit

144

Fifth localization unit

146

Sixth localization unit

147

Seventh localization unit

148

illumination light beam

150

process step a)

125

process step b)

154

process step c)

156

process step d)

158

evaluation unit

160

control unit

162

environmental parameter detection unit

164

sensor

166

temperature sensor

168

pressure sensor

170

humidity sensor

172

Temperature invariant connection construction

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US 2011/0007326 A1 [0015, 0066]
• US 2013/0050410 A1 [0015, 0066]
• US 2017/0258531 A1 [0015, 0066]
• US 9559486 B2 [0020, 0071]
• US 8913636 B2 [0020, 0071]
• US2016123718 A1 [0020, 0071]

Claims (10)

Method for determining a change in at least one air column property (110) in at least one working volume (112) of an optical navigation system (114), the optical navigation system (114) having at least one multilateration system (122) comprising at least three retroreflectors (124) and at least six localization units (126) or at least six retroreflectors (124) and at least three localization units (126), the localization units (126) being arranged around the working volume (112) or the retroreflectors (124) being arranged around the localization units (126), the method comprising the following steps: a) generating at least one illumination light beam (148) with at least two of the localization units (126) and illuminating a common retroreflector (124) or a retroreflector ensemble from different spatial directions with the illumination light beams (148) of the localization units (126); b) Receiving in each case at least one of the light beams (128) reflected by the jointly illuminated retroreflector (124) or the retroreflector ensemble and generating in each case at least one measurement signal with the localization units (126 ); c) evaluating the measurement signals of the localization units (126), the evaluation determining a first position of the jointly illuminated retroreflector (124) or of the retroreflector ensemble from a measurement signal of a first illuminating the jointly illuminated retroreflector (124) or the retroreflector ensemble , localization unit (126) and a second position of the jointly illuminated retroreflector (124) or of the retroreflector ensemble from a measurement signal from a second localization unit (126) that illuminates the jointly illuminated retroreflector (124) or the retroreflector ensemble, so that for the jointly illuminated retroreflector (124) or retroreflector ensemble two positions are determined; d) determining the air column property (110) by comparing the first position and the second position of the co-illuminated retroreflector (124) or retroreflector ensemble, wherein a substantially identical change in the first position and the second position is reported as a change in the air column property (110 ) is characterized. Method according to the preceding claim, wherein the method comprises compensating and/or minimizing an influence of the air column property (110) on a localization accuracy of the multilateration system (122) by compensation calculation taking into account the determined air column property (110). Method according to one of the preceding claims, wherein each of the localization units (126) has at least one sensor system based on transit time and/or interferometry measurement principles. The method of any preceding claim, wherein the air column property (110) comprises at least one property selected from the group consisting of: a refractive index; a refractive index distribution in the working volume (112); a refractive index variation; and a turbulence. Method according to one of the preceding claims, wherein the method comprises detecting at least one environmental parameter with at least one environmental parameter detection unit (162), the environmental parameter detection unit (162) having at least one sensor (164) for detecting an environmental parameter, the sensor (164) being a temperature sensor (166) and/or a pressure sensor (168) and/or a humidity sensor (170). Method according to one of the preceding claims, in which the multilatertion system (122) has fixed and/or temperature-invariant interferometer paths. Method according to one of the preceding claims, wherein in the method a plurality of measurement positions is approached, the method comprising changing a relative position of the retroreflectors (124) to the localization units (126), the air column property (110) being determined at each of the measurement positions will. Optical navigation system (114), the optical navigation system (114) having at least one multilateration system (122), the multilateration system (122) having at least three retroreflectors (124) and at least six localization units (126) or at least six retroreflectors (124) and at least three Localization units (126), wherein the localization units (126) are arranged around the working volume (112) or the retroreflectors (124) are arranged around the localization units (126), with at least two of the localization units (126) being set up at least one each To generate illumination light beam (148) and to illuminate a common retroreflector (124) or a retroreflector ensemble from different spatial directions, the retroreflector (124) together or the localization units (126) that illuminate the retroreflector ensemble are set up to receive at least one of the light beams (128) reflected by the jointly illuminated retroreflector (124) or the retroreflector ensemble and to generate at least one measurement signal in each case, the optical navigation system ( 114) has at least one evaluation unit (158), the evaluation unit (158) being set up to evaluate the measurement signals of the localization units (126), the evaluation determining a first position of the jointly illuminated retroreflector (124) or of the retroreflector ensemble from a measurement signal from a first localization unit (126) illuminating the commonly illuminated retroreflector (124) or retroreflector ensemble and a second position of the commonly illuminated retroreflector (124) or retroreflector ensemble from a measurement signal from a second localizing unit (124) illuminating the commonly illuminated retroreflector (124) or the retroreflector ensemble illuminating localization unit (126), so that two positions are determined for the jointly illuminated retroreflector (124) or the retroreflector ensemble, the evaluation unit (158) being set up to determine the air column property (110 ) by comparing the first position and the second position of the co-illuminated retroreflector (124) or retroreflector ensemble, wherein a substantially identical change in the first position and the second position is characterized as a change in the air column property (110). Optical navigation system (114) according to the preceding claim, wherein the optical navigation system (114) is set up to carry out a method according to one of the preceding claims. Computer program with program code means to carry out a method according to one of the preceding claims relating to a method, in particular at least steps c) and d) of the method, when the program is executed on a computer or a computer network.

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