Device and method for measuring an object

Abstract

The invention relates to a device and a method for measuring an object. The object moves along a motion axis in a motion direction, and the device has: a first sensor device, which has a first and a second SMI sensor, for emitting a first / second measuring beam along a first / second measuring axis, receiving the first / second measuring beam reflected back from a first / second working area of ​​the first / second SMI sensor, and generating a first / second measuring signal from the reflected first / second measuring beam, the SMI sensor emitting the measuring beam in opposite directions along the motion axis; a control and evaluation unit, which receives the first and second measuring signals, determines the speed of the object along the motion axis according to at least one measuring signal, detects a first characteristic change of the second measuring signal at a first time point, a first characteristic change of the first measuring signal at a second time point, and a second characteristic change of the first measuring signal at a third time point, and determines the length of the object along the motion axis using the first and third time points and the speed of the object.

Description

[0001] The present invention relates to an apparatus and a method for measuring an object.

[0002] In the scientific publication "VCSEL-based miniature laser-Doppler interferometer" (Proc. SPIE 6908, Vertical-Cavity Surface-Emitting Lasers XII, 69080I (January 29, 2008); https: / / doi.org / 10.1117 / 12.775131), a laser-based technology is described in which a moving object is illuminated with a measuring beam of coherent laser light. Part of the emitted light is diffusely reflected on the surface of the moving object and returns to the laser, wherein this diffusely reflected part of the emitted light undergoes a phase shift relative to the emitted light due to the Doppler effect caused by the object's motion. In the laser resonator, self-mixing interference occurs between the emitted light and the reflected light, resulting in periodic oscillations of the laser intensity. As a result, a modulated measurement signal is generated. Based on the signal waveform of the frequency change and the intensity, the speed and direction of the moving object can be detected. For example, the basic principle of this so-called "self-mixing interference" (SMI) action principle and various possible applications are also described in the scientific publications "Laser diode self-mixing technique for sensing applications" (Guido Giuliani et al., 2002 J. Opt. A: Pure Appl. Opt. 4S283, http: / / doi.org / 10.1088 / 1464-4258 / 4 / 6 / 371) and "Laser feedback interferometry: a tutorial on the self-mixing effect for coherent sensing" (Thomas Taimre et al., Adv. Opt. Photon. 7, 570-631 (2015), https: / / doi.org / 10.1364 / AOP.7.000570).

[0003] EP 1 261 877 B1 discloses the use of a sensor operating according to the SMI principle (hereinafter referred to as SMI sensor) for measuring the movement of a sheet of paper relative to the SMI sensor. In order to improve the speed measurement, a sensor arrangement is proposed with two SMI sensors, the measuring axes of which are arranged at opposite angles relative to the normal to the plane of movement of the paper web. As a result, opposite interference effects are produced in each of the two SMI sensors. As a result, the magnitude of the speed can be determined by subtracting the detector signals, while the direction of movement can be determined by comparing the asymmetry of the detector signals. However, EP 1 261 877 B1 discloses only the measurement of the movement of planar (i.e. two-dimensional) objects (e.g. paper), but does not determine absolute lengths, in particular absolute lengths of three-dimensional objects.

[0004] EP 3 035 001 A1 shows a device for determining the absolute position of a moving object, which is also based on the use of an SMI sensor. When detected by the SMI sensor, the coded markings arranged on the surface of the object produce a characteristic amplitude change of the sensor signal, so that the position of the object can be determined. The disadvantage here is that the object must be provided with a corresponding coded marking.

[0005] The SMI sensor can only determine the radial velocity of the scanned object points, i.e. the velocity of the individual scanned object points of the moving object in the direction of the measuring axis of the SMI sensor. The velocity of the object in the direction of motion can then be determined using the angle between the measuring axis of the SMI sensor and the direction of motion of the object. If, for example, a cuboid object moves through the measuring axis of the SMI sensor, the transition of the measuring beam from the side surface to the top surface of the cuboid cannot be determined from the velocity of the SMI sensor, since the radial velocity determined by the SMI sensor remains constant, regardless of whether the side surface or the top surface of the cuboid is scanned. Therefore, the edges of the cuboid cannot be detected in this way.

[0006] A similar problem arises when the objects are located on a transport medium (e.g. a conveyor belt). The transport medium usually moves at the same speed as the objects on it, so that the SMI sensor always measures the same speed, regardless of whether it is the transport medium or the objects located on it that the SMI sensor scans. Therefore, in order to still be able to identify objects on the transport medium, additional sensors, such as light barriers, are usually used in order to identify objects on the transport medium. If an object on the transport medium interrupts the light barrier, the length of the object in the direction of movement of the transport medium can be determined from the length of the interruption and the speed of the object determined by the SMI sensor.

[0007] The object of the present invention is therefore to further develop an arrangement of SMI sensors such that it is suitable for determining the length of moving three-dimensional (in particular cuboid) objects without having to use data from other sensors or special markings on the object.

[0008] According to the invention, this object is achieved by a device and a method for contactless measurement of an object moving along an axis of movement.

[0009] The present invention is based on the following basic idea, namely that in a sensor device with two self-mixing interferometer sensors (SMI sensors) having measurement light beams emitting in opposite directions, the dimensions of a three-dimensional object moving along a movement axis lying in a movement plane, in particular the length of a cuboid object, can be determined by skillful evaluation of the measurement signals of the SMI sensors.

[0010] The device for measuring an object moving in a motion plane along a motion axis according to the present invention comprises a first sensor device having a first self-mixing interferometer sensor (SMI sensor) for emitting a first measuring beam along a first measuring axis. The first SMI sensor has a first working area along the first measuring axis, wherein the first measuring beam reflected back from the first working area to the first SMI sensor generates a first measuring signal in the first SMI sensor. The first SMI sensor is oriented so that the emitted first measuring beam extends at least partially in the direction of motion of the object, i.e. has a component parallel to the motion axis and a component in the direction of motion. Therefore, the first measuring axis forms a first angle with a plane perpendicular to the motion axis.

[0011] The first sensor device also includes a second SMI sensor, which is used to emit a second measurement light along a second measurement axis. The second SMI sensor has a second working area along the second measurement axis, wherein a second measurement light beam reflected from the second working area back to the second SMI sensor generates a second measurement signal in the second SMI sensor. The second SMI sensor is oriented so that the emitted second measurement light beam extends at least partially opposite to the direction of movement of the object, i.e., has a component parallel to the axis of movement and a component opposite to the direction of movement. Therefore, the second measurement axis forms a second angle with a plane perpendicular to the axis of movement, which second angle is different from the first angle formed by the first measurement axis and the plane perpendicular to the axis of movement at least in sign.

[0012] The SMI sensor is configured so that only the measuring light beam reflected back from the working area of ​​the SMI sensor generates measurement signals, which are fed for further processing. Each of these working areas has an end facing the SMI sensor and an end facing away from the SMI sensor. The extension of the working area can be defined according to principle, for example in the following way: due to the material properties of the object to be measured, the intensity of the reflected measuring light beam is no longer sufficient to generate a measurement signal from a certain distance from the SMI sensor. For example, the center of the working area can be located in the waist area of ​​the measuring light beam. Alternatively, the working area can be limited by the transport medium on the side of the working area facing away from the SMI sensor. The end of the working area facing away from the SMI sensor is the intersection of the measuring axis of the sensor and the transport medium. The length of the working area can also be set by a corresponding distance filter of the SMI sensor.

[0013] The distance between the ends of the working areas facing away from the SMI sensor, which is parallel to the axis of movement of the object, defines a measurement path having a measurement path length, wherein if the end of the first working area facing away from the first SMI sensor is arranged upstream of the end of the second working area facing away from the second SMI sensor in the direction of movement, the measurement path length has a positive magnitude, and if the end of the first working area facing away from the first SMI sensor is arranged downstream of the end of the second working area facing away from the second SMI sensor in the direction of movement, the measurement path length has a negative magnitude.

[0014] The device further comprises a control and evaluation unit for receiving the first and second measurement signals and for determining the speed along the axis of motion from at least one of the measurement signals. Alternatively, the speed can already be determined in the SMI sensor from the measurement signals.

[0015] The speed can be the speed of the object to be measured or the speed of the transport medium if the transport medium is located in the working area.

[0016] The control and evaluation unit is designed to detect a first characteristic change of the first measurement signal at a first point in time, a first characteristic change of the second measurement signal at a second point in time, and a second characteristic change of the first measurement signal at a third point in time.

[0017] A characteristic change of the measurement signal of the SMI sensor is to be understood as an overall change of the measurement signal. This can be, for example, a change in the total intensity of the modulated SMI measurement signal described in the prior art presented at the beginning. A change in the total intensity occurs in the case where the measurement light is reflected from surfaces of different reflectivity (for example, when the SMI sensor detects both the transport medium and an object located on the transport medium, and the reflection behavior of the transport medium differs from the reflection behavior of the object to be detected, so that a significant change in the total intensity that exceeds the signal noise occurs when the object is detected instead of the transport medium).

[0018] The overall change in the measurement signal can also include a digital change, meaning the presence or absence of an SMI measurement signal. This can occur, for example, even when the transport medium is outside the working area of ​​the SMI sensor. The measurement light reflected back from the transport medium is not sufficient to generate interference in the SMI sensor and is therefore not detected by the SMI sensor. In this case, a measurement signal is only generated when the object enters the working area of ​​the SMI sensor.

[0019] For determining the length of the object, the control and evaluation unit is designed to determine the length of the object along the axis of movement using the first time, the second time, the third time, the determined object speed and the measurement path length.

[0020] An advantage of the invention is that with the device the speed and length of an object can be determined without the need for other sensors or special markings on the object.

[0021] In particular, in the case of a uniform movement of the object, a single velocity determination, for example in the time period between the first time point and the third time point, is sufficient to determine the length of the object. The control and evaluation unit can also be designed to store the determined velocity over time. Thus, even in the case of a non-uniform velocity, the length of the object can be determined precisely.

[0022] In the case of uniform movement at a constant speed, the control and evaluation unit can be designed to determine a length value based on a first time difference between a third time point and the first time point and the constant speed, and to determine the length of the object along the axis of movement by adding the length value to the measurement path length.

[0023] In order to determine the length more accurately, the control and evaluation unit can additionally or alternatively be designed to determine a length value by time integration of the speed determined between the first time point and the third time point in the case of variable speed, and to determine the length of the object along the axis of movement by adding this length value to the measurement path length.

[0024] The control and evaluation unit can be embodied as a component of the sensor arrangement, as an external unit or as part of one of the SMI sensors.

[0025] The control and evaluation unit can have an interface for outputting received data and / or for outputting the object length, for example to a display unit or a superordinate controller.

[0026] Preferably, the measuring axes of the first SMI sensor and the second SMI sensor may have angles of equal magnitude relative to a plane perpendicular to the axis of motion.Such a symmetrical arrangement simplifies data processing.

[0027] Preferably, the measurement axes of the first SMI sensor and the second SMI sensor can be located in a common measurement plane. Preferably, the axis of motion of the object can be located in the common measurement plane. This geometric arrangement further simplifies data processing. The first SMI sensor and the second SMI sensor can be arranged so that their measurement axes intersect at an intersection in the common measurement plane. Here, the intersection can be located in the center of the working area of ​​the SMI sensor.

[0028] In an alternative embodiment, the measuring axes of the first SMI sensor and the second SMI sensor may be located in parallel measuring planes. This geometric arrangement prevents interference signals caused by reflections of the measuring beam at the optics of the respective other SMI sensor. Preferably, the axis of motion of the object may be located between the measuring planes. The first SMI sensor and the second SMI sensor may be arranged so that the distance between the centers of the working areas of the SMI sensors is minimized.

[0029] In an embodiment, the transport medium may be located in at least one working area of ​​the SMI sensor. Thereby, the speed of the transport medium may be determined.

[0030] In an alternative embodiment, the transport medium can be located outside the working area of ​​the SMI sensor. This has the advantage that objects can be detected more reliably, because only the measurement signal of the object on the transport medium is detected, and not the measurement signal of the transport medium itself.

[0031] The measuring path length can be determined during the teaching process, for example, using a measuring body of defined length, whose reflectivity corresponds within the usual tolerance range to the reflectivity of the object to be measured. If the SMI sensors are arranged so that their operating area is limited by the transport medium, the measuring path length results from the distance of the intersection point of the measuring light beam with the transport medium.

[0032] The control and evaluation unit can use the first and second measurement signals to determine the speed of the object along the axis of motion, wherein the speeds obtained with the two sensors can be averaged or the measurement signals can be subtracted for speed determination, as described in EP 1 261 877 B1. This allows a more precise determination of the speed.

[0033] In an embodiment of the invention, a second sensor device can be provided, which has a third SMI sensor and a fourth SMI sensor, wherein the measuring axes of the third SMI sensor and the fourth SMI sensor can preferably be oriented parallel to the measuring axes of the first SMI sensor and the second SMI sensor. The advantage of using a second sensor device is that not only the size can be determined, but also the orientation of the object on the transport medium by comparing the time curves of the characteristic changes of the signals in the first sensor device and the second sensor device. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be described in detail below based on embodiments with reference to the accompanying drawings. Here, the same components in the accompanying drawings are marked with the same reference symbols. In the accompanying drawings:

[0035] Figure 1 A device for measuring an object moving along an axis of motion according to the invention is shown;

[0036] Figure 2 shows an exemplary scanning of an object at different points in time using the device according to the invention in the case where the transport medium is located outside the working area of ​​the SMI sensor;

[0037] Figure 3 shows the scanning of an object at different points in time using the device according to the invention, when the transport medium is located within the working area of ​​the SMI sensor;

[0038] Figure 4 A device according to the invention for measuring an object moving along an axis of movement is shown, which device has two sensor devices arranged in parallel.

[0039] Figure 1A device 10 according to the invention is shown for measuring an object 14 which moves along a movement axis 12 in a movement direction 13 at a speed v. The device 10 comprises a first sensor device 16 having a first self-mixing interferometer sensor (SMI sensor) 18.1 and a second SMI sensor 18.2, and a control and evaluation device 20 for controlling the SMI sensors 18.1, 18.2 and for receiving and / or evaluating measurement signals 44, 48 of the SMI sensors 18.1, 18.2. The control and evaluation device 20 has an interface 21 for forwarding measurement signals and / or evaluation results. The interface 21 can also be configured to receive control signals from a superior controller. The first SMI sensor 18.1 emits a measuring light beam from a hole 36.1 along a first measuring axis 22.1, the first measuring axis 22.1 having a first angle α relative to a plane 24 perpendicular to the movement axis 12. 1 The second SMI sensor 18.2 emits measuring light from the aperture 36.2 along a second measuring axis 22.2 which has a second angle α relative to the plane 24 perpendicular to the axis of movement 12. 2 Angle α 1 , α 2 is a directed angle with an orientation indicated by the sign preceding the magnitude of the angle. In embodiments, the angles have equal magnitudes, applicable to α 2 =-α 1 The measuring axes 22.1, 22.2 can also lie in a common measuring plane, which in the exemplary embodiment is the drawing plane. If, as in the exemplary embodiment, the axis of motion 12 lies in or is parallel to the measuring plane, the velocity v of the object 14 is determined according to the velocity v determined by the SMI sensors 18.1, 18.2 传感器1 、v 传感器2 According to the following formula:

[0040]

[0041] or

[0042]

[0043] The first SMI sensor 18.1 and the second SMI sensor 18.2 each have a first working area 26.1 and a second working area 26.2 along the measuring axes 22.1, 22.2, wherein only the measuring light beam reflected back from the working areas 26.1, 26.2 generates measuring signals 44, 48, which are fed for further processing. The end 28.1 of the first working area 26.1 facing away from the first SMI sensor 18.1 and the end 28.2 of the second working area 26.2 facing away from the second SMI sensor 18.2 define a measuring path parallel to the axis of motion 12 of the object 14, which has a measuring path length l M Since in the exemplary embodiment the end 28.1 of the first working area 26.1 facing away from the first SMI sensor 18.1 is arranged downstream of the end 28.2 of the second working area 26.2 facing away from the second SMI sensor 18.2 in the direction of movement 13 of the object 14, the measuring path length l M Negative value participates in the object length l Obj of determination.

[0044] The first sensor device 16 measures the height h arranged above the transport medium 34 from the holes 36 . 1 , 36 . 2 of the SMI sensors 18 . 1 , 18 . 2 . 传感器 In this embodiment, the ends 28.1, 28.2 of the working areas 26.1, 26.2 facing away from the SMI sensors 18.1, 18.2 are located at a distance h above the transport medium 34. 偏移 The vertical distance 38 from the holes 36.1, 36.2 of the SMI sensors 18.1, 18.2 to the intersection of the measuring axes 22.1, 22.2 is called the standoff distance (SD).

[0045] Figure 2 A first example of the functional principle of the device according to the invention is schematically shown. The sensor device 16 is arranged at a first height h above the transport medium 34 (eg a conveyor belt). 传感器1 The transport medium 34 is located in the working area 26.1, 26.2 of the SMI sensors 18.1, 18.2. As a result, the transport medium 34 does not generate any intensity signal in the SMI sensors 18.1, 18.2, such as Figure 2 The intensity-time diagram 40 in the lower left corner is shown. Therefore, the SMI sensors 18.1, 18.2 of the sensor unit 16 do not provide any speed signal either. Figure 2 The speed-time diagram 42 is shown in the lower right corner.

[0046] At the first time point T 1 , the object 14 moving along the movement axis 12 on the transport medium 34 enters the second measurement axis 22.2 of the second SMI sensor 18.2. The measuring light beam emitted by the second SMI sensor 18.2 is reflected by the object 14, returns at least partially along the second measurement axis 22.2 to the second SMI sensor 18.2, and generates a second measurement signal 44 with an intensity I at the second SMI sensor 18.2 (dashed line in the intensity-time diagram 40). Therefore, at the time point T 1 A first characteristic change of the second measurement signal 44 occurs, namely a sudden change in intensity from a value below the indication limit to a value at which the second SMI sensor 18.2 can determine the velocity v, so that the velocity-time diagram 42 also shows the velocity v from the time T 1 A non-zero second velocity signal 46 (dashed line in the velocity-time graph 42) is generated.

[0047] At the second time point T 2 , the measuring beam emitted by the first SMI sensor 18.1 is also reflected by the object 14, returns at least partially along the first measuring axis 22.1 to the first SMI sensor 18.1, and generates a first measuring signal 48 with an intensity I at the first SMI sensor 18.1 (dash-dotted line in the intensity-time diagram 40). Thus, similarly to the second measuring signal 44 at the time T 1 The change at time point T 2 A first characteristic change occurs in the first measurement signal 48. Therefore, the first SMI sensor 18.1 now also supplies a non-zero first speed signal 50 (dash-dotted line in the speed-time diagram 42).

[0048] At the third time point T 3 , the object 14 leaves the first measuring axis 22.1 of the first SMI sensor 18.1. Therefore, a second characteristic change of the first measuring signal 48 occurs, and the intensity of the first measuring signal 48 also drops again to a value below the indication limit, which also means that there is no longer a first speed signal 50.

[0049] At a constant object speed v konst In the case of Obj :

[0050] l Obj =(T 3 -T 1 )·v konst +l M

[0051] Among them, l M= represents the measuring path length of the sensor device 16. Since in the exemplary embodiment the end 28.1 of the first working area 26.1 facing away from the first SMI sensor 18.1 is arranged downstream of the end 28.1 of the second working area 26.2 facing away from the second SMI sensor 18.2 in the direction of movement 13 of the object 14, the measuring path length l M Negative value participates in the object length l Obj Determination, that is, from the time point T 3 and T 1 Subtract the difference from the length obtained.

[0052] The object has a variable velocity v var In the case of object length l Obj The object velocity v which is variable over time and stored over time in the SMI sensors 18 . 1 , 18 . 2 or in the evaluation unit 20 can be used. var (t) is determined. The following applies:

[0053]

[0054] Figure 3 A second example of the functional principle of the device according to the invention is schematically shown. The sensor device 16 is arranged at a second height h above the transport medium 34. 传感器2 The transport medium 34 is located in the working area 26.1, 26.2 of the SMI sensors 18.1, 18.2. As a result, the transport medium 34 generates intensity signals 64, 68 in the SMI sensors 18.1, 18.2, such as Figure 3 The intensity-time diagram 60 in the lower left corner is shown. Therefore, the SMI sensors 18.1, 18.2 of the sensor unit 16 also provide speed signals, such as Figure 3 The speed-time diagram 62 is shown in the lower right corner.

[0055] At the first time point T 1 , an object 14 moving along the movement axis 12 in the movement direction 13 on the transport medium 34 enters the second measurement axis 22.2 of the second SMI sensor 18.2. The measurement light beam emitted by the second SMI sensor 18.2 is reflected by the object 14 and returns at least partially along the second measurement axis 22.2 to the second SMI sensor 18.2. Due to the different reflectivities of the transport medium 34 and the object 14 (in this example, the reflectivity of the object 14 is higher than that of the transport medium 34), the intensity of the second measurement signal 64 changes (dashed line in the intensity-time diagram 60). Therefore, at the time point T 1A first characteristic change of the second measurement signal 64 occurs, namely a sudden increase in intensity, which can be detected by the second SMI sensor 18.2. Since the object 14 moves at the same speed v as the transport medium 34, the speed v determined by the second SMI sensor 18.2 and the corresponding second speed signal 66 (dashed line in the speed-time diagram 62) do not change.

[0056] At the second time point T 2 , the measuring light beam emitted by the first SMI sensor 18.1 is also reflected by the object 14 and returns at least partially along the first measuring axis 22.1 to the first SMI sensor 18.1. Due to the different reflectivities of the transport medium 34 and the object 14, the intensity of the first measurement signal 68 (dash-dotted line in the intensity-time diagram 60) also increases at the time point T 1 Therefore, at time point T 2 A first characteristic change of the first measurement signal 68 occurs, namely a sudden increase in intensity, which can be detected by the first SMI sensor 18.1. Since the object 14 moves at the same speed v as the transport medium 34, the speed determined by the first SMI sensor 18.1 and the corresponding first speed signal 70 (dash-dotted line in the speed-time diagram 62) also do not change.

[0057] At the third time point T 3 , the object 14 leaves the first measuring axis 22.1 of the first SMI sensor 18.1. As a result, a second characteristic change of the first measuring signal 68 occurs, and the intensity of the first measuring signal 68 falls back to the second time point T 2 The previous value.

[0058] Therefore, in Figure 3 In the example described, not only the object velocity v can be determined, but also the velocity of the transport medium. However, for the length determination, the reflectivity of the transport medium 34 and the object 14 to be measured must differ sufficiently so that a characteristic change in the intensity of the measurement signal can be detected by the SMI sensors 18.1, 18.2, so that the time point T can be reliably determined. 1 To T 3 The length of object 14 is Figure 2 Determined as in the example described in .

[0059] Figure 4 A schematic top view of another embodiment of a device 80 according to the present invention is shown, wherein the device 80 has a first sensor device 16 (eg Figure 1The second sensor device 16b can be constructed like the first sensor device 16, wherein the measuring axes of the SMI sensors of the first sensor device 16 and the second sensor device 16b are oriented so that the measuring axes are located in parallel measuring planes 88a, 88b.

[0060] If a rectangular object 84, 94 (eg a package on a conveyor belt) is moved on the transport medium 81 along the movement axis 82 through the working area of ​​the sensor device 16, 16b, the object length L can be determined. 1a , L 1b , L 2a , L 2b The orientation of the object 84 , 94 on the transport medium 81 is determined by comparing the time curves of characteristic changes of the signals and the entry of the object into the working area of ​​the SMI sensor of the sensor device 16 , 16 b or the exit of the object from the working area.

[0061] For example, in the case of first object 84, if the side faces of the first object are oriented parallel or perpendicular to measuring planes 88a, 88b of sensor devices 16, 16b, these sensor devices determine the same length L of first object 84. 1a , L 1b On the other hand, the first object 84 simultaneously enters the working area of ​​the SMI sensors of the sensor devices 16 , 16 b within the usual tolerance range.

[0062] For example, in the case of second object 94, if the side surface is not oriented parallel to measuring planes 88a, 88b of sensor devices 16, 16b, second object 94 enters the working area of ​​the SMI sensor of sensor devices 16, 16b at different points in time, and on the other hand, the determined length L of second object 94 is different from that of 2a , L 2b If the size of the object is known, the position of the object 94 on the transport medium 81 can be determined.

Claims

1. A device (10) for measuring an object (14) which moves along a movement axis (12) in a movement direction (13), the device comprising: A first sensor device (16) comprising: a first self-mixing interferometer sensor (18.1) for emitting a first measuring light beam along a first measuring axis (22.1), receiving the first measuring light beam reflected back from a first working area (26.1) of the first self-mixing interferometer sensor (18.1), and generating a first measuring signal (48) from the reflected first measuring light beam, wherein the first self-mixing interferometer sensor (18.1) is oriented such that the emitted first measuring light beam extends at least partially in the direction of movement (13) of the object (14), a second self-mixing interferometer sensor (18.2) for emitting a second measuring light beam along a second measuring axis (22.2), receiving the second measuring light beam reflected back from a second working area (26.2) of the second self-mixing interferometer sensor (18.2), and generating a second measuring signal (44) from the reflected second measuring light beam, wherein the second self-mixing interferometer sensor (18.2) is oriented such that the emitted second measuring light beam extends at least partially opposite to the direction of movement (13) of the object (14), in, The first working area (26.1) has an end (28.1) facing away from the first self-mixing interference sensor (18.1), and the second working area (26.2) has an end (28.2) facing away from the second self-mixing interference sensor (18.2), and the ends (28.1, 28.2) define a measurement path parallel to the movement axis (12), the measurement path having a measurement path length l M ; a control and evaluation unit (20) for receiving the first measurement signal (48) and the second measurement signal (44) and for determining a velocity v of the object along the axis of motion (12) based on at least one of the measurement signals (44, 48), It is characterized in that The control and evaluation unit (20) is configured to: The second measurement signal (44) is detected at a first time point T 1 The first characteristic change, Detect a first characteristic change of the first measurement signal (48) at a second time point T 2 ​ Detecting the first measurement signal (48) at a third time point T 3 The second characteristic change, and Using the first time point T 1 , the third time point T 3 , the velocity v and the measurement path length l M Determining an object length l of the object (14) along the motion axis (12) Obj .

2. The device (10) according to claim 1, It is characterized in that The control and evaluation unit (20) is designed to store the speed v over time.

3. The device (10) according to claim 1, It is characterized in that The control and evaluation unit (20) is designed to control the object (14) at a constant speed v konst Next, according to the third time point T 3 and the first time point T 1 The time difference between the constant speed v konst The length value is determined, and based on the length value and the measurement path length l M The length of the object (14) along the axis of motion (12) is determined.

4. The device (10) according to claim 2, It is characterized in that The control and evaluation unit (20) is designed to control the object (14) at a constant speed v konst Next, according to the third time point T 3 and the first time point T 1 The time difference between the constant speed v konst The length value is determined, and based on the length value and the measurement path length l M The length of the object (14) along the axis of motion (12) is determined.

5. The device (10) according to claim 2, It is characterized in that The control and evaluation unit (20) is designed to operate at a variable speed v var Next, by the first time point T 1 and the third time point T 3 The variable speed v between var The length value is determined by time integration, and the length value and the measurement path length l are used to determine the length value. M The length of the object (14) along the axis of motion (12) is determined.

6. The device (10) according to any one of claims 3 to 5, It is characterized in that If the end (28.1) of the first working area (26.1) facing away from the first self - mixing interference sensor (18.1) is arranged upstream in the direction of movement (13) of the end (28.2) of the second working area (26.2) facing away from the second self - mixing interference sensor (18.2), then the measurement path length l M is positive. If the end (28.1) of the first working area (26.1) facing away from the first sensor (18.1) is arranged downstream in the direction of movement (13) of the end (28.2) of the second working area (26.2) facing away from the second self - mixing interference sensor (18.2), then the measurement path length l M is negative, and the control and evaluation unit (20) is designed to determine the length l of the object (14) by adding the length value and the measurement path length l M . Obj .

7. The device (10) according to any one of claims 1 to 5, It is characterized in that The first measuring axis (22.1) has a first angle α relative to a plane (24) perpendicular to the movement axis (12). 1 , and the second measuring axis (22.2) has a second angle α relative to a plane (24) perpendicular to the movement axis (12) 2 , where the angle α 1 , α 2 have different signs, and the angle α 1 , α 2 The magnitudes are equal.

8. The device (10) according to any one of claims 1 to 5, It is characterized in that The first measuring axis (22.1) and the second measuring axis (22.2) lie in a common measuring plane.

9. The device (10) according to claim 8, It is characterized in that The axis of movement (12) of the object (14) lies in the common measuring plane.

10. The device (10) according to any one of claims 1 to 5 and 9, It is characterized in that The first measuring axis (22.1) and the second measuring axis (22.2) are located in parallel measuring planes.

11. The device (10) according to claim 10, It is characterized in that The axis of motion (12) of the object (14) lies between the parallel measuring planes.

12. The device (10) according to any one of claims 1 to 5, 9 and 11, It is characterized in that The object (14) is moved by a transport medium (34), wherein the transport medium (34) is located in at least one working area (26.1, 26.2) of the self-mixing interferometric sensor (18.1, 18.2).

13. The device (10) according to any one of claims 1 to 5, 9 and 11, It is characterized in that The object (14) is moved by a transport medium (34), wherein the transport medium (34) is located outside the working area (26.1, 26.2) of the self-mixing interferometric sensor (18.1, 18.2).

14. The device (10) according to any one of claims 1 to 5, 9 and 11, It is characterized in that The control and evaluation unit (20) is designed to determine a speed v along the axis of movement (12) using the first measurement signal (48) and the second measurement signal (44).

15. The device (80) according to any one of claims 1 to 5, 9 and 11, It is characterized in that The device (80) has a second sensor device (16b), which has a third self-mixing interference sensor and a fourth self-mixing interference sensor, wherein the measuring axes of the third self-mixing interference sensor and the fourth self-mixing interference sensor are oriented parallel to the measuring axes (22.1, 22.2) of the first self-mixing interference sensor (18.1) and the second self-mixing interference sensor (18.2) of the first sensor device (16).

16. A method for measuring an object (14) which moves along a movement axis (12) in a movement direction (13), the method comprising the following steps: emitting a first measuring light beam along a first measuring axis (22.1) using a first self-mixing interferometer sensor (18.1) of a first sensor device (16), wherein the first self-mixing interferometer sensor (18.1) is oriented such that the emitted first measuring light beam extends at least partially in the direction of movement (13) of the object (14), receiving a first measuring light beam reflected from a first working area (26.1) of the first self-mixing interferometric sensor (18.1), generating a first measurement signal (48) from the reflected first measurement light beam, emitting a second measuring light beam along a second measuring axis (22.2) by means of a second self-mixing interferometer sensor (18.2) of the first sensor device (16), wherein the second self-mixing interferometer sensor (18.2) is oriented such that the emitted second measuring light beam extends at least partially opposite to the direction of movement (13) of the object (14), receiving a second measuring light beam reflected from a second working area (26.2) of the second self-mixing interferometric sensor (18.2), generating a second measurement signal (44) from the reflected second measurement beam, The first working area (26.1) has an end (28.1) facing away from the first self-mixing interference sensor, and the second working area (26.2) has an end (28.2) facing away from the second self-mixing interference sensor, and the ends (28.1, 28.2) define a measurement path parallel to the movement axis (12), the measurement path having a measurement path length l M ; receiving the first measurement signal (48) and the second measurement signal (44) by means of a control and evaluation unit (20), and determining a velocity v along the axis of motion (12) based on at least one of the measurement signals (44, 48), It is characterized in that The second measurement signal (44) is detected at a first time point T 1 The first characteristic change, Detect a first characteristic change of the first measurement signal (48) at a second time point T 2 ​ Detecting the first measurement signal (48) at a third time point T 3 The second characteristic change, and Using the first time point T 1 , the third time point T 3 , the velocity v and the measurement path length l M Determine the length l of the object along the axis of motion (12) Obj .

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