Abstract
A device for determining at least one of a speed and a length of a product. The device includes a laser for irradiating a surface of the product, a detector apparatus to detect laser radiation backscattered from the surface, a first sensor with a first transmission grid arranged in front of the first sensor and a second sensor. A first beam splitter splits laser radiation backscattered from the product into laser radiation conducted to at least one of the first sensor and to the second sensor. An evaluation apparatus determines at least one of: (i) the speed; and (ii) the length of the product. A third sensor is provided as is a second beam splitter that splits laser radiation coming from the first beam splitter to at least one of the sensors. The evaluation apparatus eliminates a direct component of the measurement signal received by the first sensor.
Claims
1-11. (canceled)
12. A device for determining at least one of a speed and a length of a product moving along a conveying direction, comprising: a laser configured to irradiate a surface of the product, a detector apparatus configured to detect laser radiation backscattered from the surface of the product; a first sensor with a first transmission grid arranged in front of the first sensor; a second sensor formed by an image sensor; a first beam splitter configured to split laser radiation backscattered from the product into laser radiation conducted to at least one of the first sensor and to the image sensor; an evaluation apparatus configured to determine at least one of: (i) the speed; and (ii) the length of the product based on: (i) an intensity modulation detected by the first sensor during a movement of the product; and (ii) a shift of a speckle pattern formed on the image sensor detected by the image sensor during a movement of the product; a third sensor; a second beam splitter positioned between the first beam splitter and the image sensor and is configured to split laser radiation coming from the first beam splitter into laser radiation conducted to at least one of: (i) the image sensor; (ii) the first sensor; and (iii) the third sensor, wherein the evaluation apparatus is configured to calculate a difference in measurement signals from the first sensor and from the third sensor in order to determine at least one of: (i) the speed; and (ii) the length of the product so that a direct component of the measurement signal received by the first sensor is eliminated.
13. The device according to claim 12, further comprising a first transmission grid and a first lens positioned between a first transmission grid and the first sensor, wherein the first lens is configured to focus the laser radiation onto the first sensor.
14. The device according to claim 12, wherein the first sensor is a photodiode.
15. The device according to claim 13, further comprising a second lens positioned between the first beam splitter and the image sensor and configured to focus the laser radiation conducted to the image sensor.
16. The device according to claim 12, wherein the image sensor is one of: (i) a CCD sensor or (ii) a CMOS sensor.
17. The device according to claim 13, further comprising a second transmission grid positioned in front of the third sensor, wherein the second transmission grid is phase-shifted by 180° compared to the first transmission grid.
18. The device according to claim 12, wherein the third sensor is a photodiode.
19. The device according to claim 12, wherein the evaluation apparatus is configured to determine a shift of the speckle pattern detected by the image sensor in a direction transverse to the conveying direction of the product.
20. The device according to claim 19, further comprising an adjusting apparatus configured to adjust a point of incidence of the laser radiation on the product at least in a direction transverse to the conveying direction of the product, wherein that the evaluation apparatus is configured to control the adjusting apparatus to adjust the point of incidence of the laser radiation on the product at least in a direction transverse to the conveying direction of the product, and wherein the adjusting apparatus is controlled based on the determined shift of the speckle pattern detected by the image sensor in the direction transverse to the conveying direction of the product.
21. The device according to claim 12, further comprising a distance setting apparatus configured to set a distance of at least one of the laser and the detector apparatus from the surface of the product.
22. The device according to claim 12, further comprising a laser beam splitter configured to conduct laser radiation vertically onto the surface of the product.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Exemplary embodiments of the invention are explained in greater detail below based on drawings. Schematically:
[0024] FIG. 1 illustrates an embodiment of a device for determining the speed and/or the length of a product;
[0025] FIG. 2 illustrates another embodiment of the device for determining the speed and/or the length of a product;
[0026] FIG. 3 illustrates an embodiment of setting an embodiment of a laser;
[0027] FIG. 4A illustrates a partial view of an embodiment of an adjusting apparatus for adjusting the point of incidence of the laser radiation;
[0028] FIG. 4B illustrates another partial view of the embodiment of FIG. 4A;
[0029] FIG. 4C illustrates another partial view of the embodiments of FIG. 4A and 4B; and
[0030] FIG. 5 illustrates another embodiment of the device for determining the speed and/or the length of a product.
[0031] The same reference signs refer to the same objects in the figures unless indicated otherwise.
DETAILED DESCRIPTION OF THE INVENTION
[0032] FIG. 1 shows a section of a tubular strand 10 which is conveyed by means of a conveying apparatus (not shown) along a conveying direction, as illustrated by the arrow 12. The conveying direction runs in the direction of the longitudinal axis of the strand 10. Laser radiation is conducted onto the surface of the strand 10 by means of a laser 14. Laser radiation scattered from the surface is split into two radiation components by means of a first beam splitter 16. A first radiation component strikes a first transmission grid 18. Laser radiation passing through the first transmission grid 18 is focused by a first lens 20 onto a first sensor 22, which can be, for example, a photodiode. A second radiation component reaches a second sensor 24, which is an image sensor, for example a CCD sensor or a CMOS sensor. A focusing second lens 26, arranged directly in front of the image sensor 24, can be provided. Alternatively or additionally, a focusing second lens 28 can also be arranged directly after the first beam splitter 16. The radiation coming from the first radiation splitter 16 is focused onto a measuring opening of the image sensor 24 by the second lens 26 and/or 28.
[0033] By using coherent laser light, a speckle pattern is formed on the first transmission grid 18, on the one hand, and on the sensor surface of the image sensor 24, on the other hand. This speckle pattern is characterized by the surface structure of the strand 10 and moves accordingly with the strand 10. As a result, the first sensor 22 detects an intensity modulation with a modulation frequency that is characteristic of the movement of the strand 10. On the other hand, the speckle pattern shifts on the sensor surface of the image sensor 24 and the image sensor 24 detects this shift. The measurement signals from the first sensor 22 and from the image sensor 24 are supplied to an evaluation apparatus 30. The evaluation apparatus 30 determines the speed and/or the length of the strand between different measurement times based on the intensity modulation detected by the first sensor 22 and/or based on the shift of the speckle pattern detected by the image sensor 24.
[0034] The embodiment in FIG. 2 largely corresponds to the device from FIG. 1. In contrast to the device from FIG. 1, in the case of the device in FIG. 2, a second beam splitter 32 is arranged between the first beam splitter 16 and the image sensor 24 and splits laser radiation coming from the first beam splitter 16 into laser radiation conducted to the image sensor 24 on the one hand and to a third sensor 34 on the other hand. The third sensor 34 can also be formed by a photodiode. In addition to the measurement signals from the first sensor 22 and the image sensor 24, in the exemplary embodiment according to FIG. 2, the measurement signals from the third sensor 34 are also conducted to the evaluation apparatus 30. The evaluation apparatus 30 calculates a difference between the measurement values of the first sensor 22 and the third sensor 34 in order to eliminate a direct component in the measurement signal. This improves the signal-to-noise ratio and increases the measurement accuracy. It is possible to arrange a second transmission grid, which is phase-shifted by 180° compared to the first transmission grid 18, in front of the third sensor 34, in particular between the second beam splitter 32 and the third sensor 34. In the case of a differential formation between the sensor signals from the first and third sensors 22, 34, this additionally leads to a maximum amplification of the measured modulation signal.
[0035] The embodiment shown in FIG. 3, illustrates how tilting the laser 14 of FIG. 1 can ensure an ability to adjust to different distances between the surface of the strand 10 and the device, in particular the sensors 22, 24 or respectively the beam splitter 16. In this case, two strand surfaces at different distances from the device and correspondingly two different positions of the laser 14 are shown. Tilting the laser 14 ensures that the laser radiation always strikes the strand surface in the middle vertically below the beam splitter 16. This of course applies in the same manner to the exemplary embodiment shown in FIG. 2. Due to the omission of an optical imaging unit between the strand 10 and the sensors 22, 24 and possibly 34 in the devices shown according to the invention, and due to the fact that the speckle pattern formed on the first transmission grid 18 or respectively the image sensor 24 is always sharp, no additional calibration measures are required when tilting the laser 14, in a particularly simple manner.
[0036] In FIGS. 4A-C, an adjusting apparatus integrated into the laser 14 for adjusting the point of incidence of the laser radiation on the strand 10 in a direction transverse to the conveying direction of the strand 10 is shown very schematically. This can be used in each of the exemplary embodiments shown. In FIGS. 4A-C, three different partial views are shown which show different states. In all three partial views show in FIGS. 4A-C, the conveying direction of the strand 10 runs perpendicularly into the plane of the drawing. In FIG. 4A, a state is shown in which laser radiation from the laser 14 strikes the surface of the strand 10 in the middle vertically downward. Striking it in the middle is the desired state. FIG. 4B illustrates a state in which the strand 10 has moved transversely to the conveying direction, in the partial view somewhat to the left. As a result, the point of incidence of the laser radiation, which continues to exit the laser 14 vertically downward, is no longer in the middle on the strand surface. This leads to a non-optimal illumination of the strand surface and can, with a correspondingly pronounced lateral shift of the strand 10, even lead to the strand 10 completely exiting the range of the laser radiation. The lateral shift of the strand 10 can be detected based on an evaluation of the measurement signal of the image sensor 24, in particular by a corresponding shift of the speckle pattern on the sensor surface of the image sensor 24, evaluated by the evaluation apparatus 30. The evaluation apparatus 30 can then control the adjusting apparatus in order to adapt the point of incidence of the laser radiation to the strand surface such that it is again in the middle of the strand 10, as shown in FIG. 4C. The adjusting apparatus can, for example, in a particularly simple manner comprise an adjustable mirror conducting the laser radiation onto the strand surface. The mirror can be adjusted, for example, by means of a galvanometer drive.
[0037] FIG. 5 shows a further exemplary embodiment of a device according to the invention which largely corresponds to the exemplary embodiment according to FIG. 1. Additionally, a laser beam splitter 36 is provided here, which conducts laser radiation emitted by the laser 14 vertically onto the surface of the strand 10. In this case, the laser radiation is coupled directly into the beam path of the detector apparatus, in particular of the first and second sensors (22, 24), by the laser beam splitter 36. In particular, laser radiation backscattered vertically from the strand surface strikes the first beam splitter 16 and the first and second sensors 24, 26 in the middle. Laser radiation backscattered vertically from the strand surface also runs through the first and second lenses 20, 28 in the middle. A beam dump 38 is arranged on the side of the laser beam splitter 36 opposite the laser 14 in order to prevent laser radiation from passing through the laser beam splitter 36 and contacting the sensors 24, 26 directly. The component of the laser radiation that is directly let through by the laser beam splitter 36 is absorbed by the beam dump 38. Of course, the embodiment according to FIG. 5 can also be combined, for example, with the exemplary embodiment from FIG. 2.
LIST OF REFERENCE SIGNS
[0038] 10 Strand [0039] 12 Conveying direction [0040] 14 Laser [0041] 16 First beam splitter [0042] 18 First transmission grid [0043] 20 First lens [0044] 22 First sensor [0045] 24 Second sensor (image sensor) [0046] 26 Second lens [0047] 28 Second lens [0048] 30 Evaluation apparatus [0049] 32 Second beam splitter [0050] 34 Third sensor [0051] 36 Laser beam splitter [0052] 38 Beam dump
