Method and apparatus for determining a relative velocity between an object and a detector

Abstract

Method for determining a relative speed between an object and a detector (1), wherein a relative movement between the object and the detector (1) can take place in one direction of movement, wherein the object has at least one detection element (2) in the form of a code divided into at least two sub-elements (3, 4), wherein the sub-elements (3, 4) are arranged at a predeterminable spatial distance (ds) from one another at predeterminable positions on, at or in the object and are image elements of an overall image of the code, wherein during the possible relative movement and for an image recording by the detector (1), a first sub-element (3) is illuminated at a first predeterminable time for a predeterminable first illumination duration (t 1) with a first light having a first wavelength (6) and after a time interval (dt) a second sub-element (4) at a later second predeterminable time for a predeterminable second illumination duration (t 2 ) are illuminated with a second light having a second wavelength (7), wherein the wavelengths (6, 7) are selected such that that when illuminated with the first wavelength (6), the first sub-element (3) is detected as dark and when illuminated with the second wavelength (7), the second sub-element (4) is also detected as dark with a correspondingly low brightness relative to a background (5) by the detector (1), or that when illuminated with the first wavelength (6), the first sub-element (3) is brightly detected and when illuminated with the second wavelength (7), the second sub-element (4) is also brightly detected with a correspondingly high brightness relative to a background (5) by the detector (1), wherein, in the image acquisition by the detector (1), an image of the component parts (3, 4) is generated, wherein - for determining the relative velocity based on forming a quotient from the spatial distance (ds) and the time interval (dt) between the first and the second time - it is checked by means of an evaluation device whether the component parts (3, 4) are imaged in the image in a predefined relative positioning with respect to each other, wherein the component parts (3, 4) have been displaced relative to each other in such a way in the predefined relative positioning during the imaging that the code is legible or decodable, and wherein, as soon as the code is legible or decodable, the determination of the relative velocity takes place based on forming a quotient from the spatial distance (ds) and the time interval (dt) between the first and the second time.

Description

[0001] The invention relates to a method for determining a relative velocity between an object and a detector, wherein a relative movement between the object and the detector can occur in one direction of movement. Furthermore, the present invention relates to a corresponding device for carrying out such a method.

[0002] Methods and devices of the type mentioned above are known in practice and exist in various embodiments. Such methods and devices are used particularly in industrial areas where objects moving relative to a detector must be monitored, preferably automatically.

[0003] For example, EP 0 532 169 A1 discloses a method in which the relative velocity between an object on a surface and a detector with a CCD array can be determined. The relative velocity is determined based on the sequence of individual image recordings.

[0004] Furthermore, EP 1 729 086 A1 discloses a method for image processing, wherein relative speeds between an object and a detector are determined.

[0005] Furthermore, DE 10 2010 055 533 A1 discloses a method and a device for determining the rotational speed of a rotatably mounted part of a device, wherein a rotatably mounted shaft 1 can be illuminated with the aid of a communication device 4, wherein the rotational speed of the shaft 1 can be determined based on one or more markings on the shaft 1.

[0006] Furthermore, a method and a device for determining the position of an object are known from US 2018 / 0 209 823 A1.

[0007] Furthermore, EP 2 133 697 A2 discloses a method and a device for detecting speeds of an object surface, wherein a detection area 13 of an object surface 3a is imaged onto a detector and partial images recorded shortly after one another are separated by an image processing unit.

[0008] The known methods for determining relative speed are well suited for the applications described in the above prior art. However, many modern applications require particularly high levels of reliability in determining relative speed. The methods known from the prior art are only of limited use for this purpose, since it is not immediately apparent that a speed measurement is faulty, particularly if one of the individual measuring components in the image processing chain fails. The aim here is to increase the reliability of determining relative speed.

[0009] The present invention is therefore based on the object of specifying a method and a device for determining the relative velocity between an object and a detector, after which a particularly reliable determination of the relative velocity between an object and a detector is made possible with structurally simple means.

[0010] According to the invention, the above object is achieved by a method having the features of claim 1 and by a device having the features of claim 16.

[0011] Thereafter, the method according to claim 1 forms a method for determining a relative velocity between an object and a detector, wherein a relative movement between the object and the detector can take place in a movement direction. wherein the object has at least one detection element in the form of a code divided into at least two sub-elements, wherein the sub-elements are arranged at a predeterminable spatial distance from one another at predeterminable positions on, at or in the object and are image elements of an overall image of the code, wherein during the possible relative movement and for image recording by the detector, a first sub-element is illuminated at a first predeterminable time for a predeterminable first illumination duration with a first light having a first wavelength and after a time interval, a second sub-element is illuminated at a later second predeterminable time for a predeterminable second illumination duration with a second light having a second wavelength, where the wavelengths are chosen such that that when illuminated with the first wavelength, the first sub-element is dark and when illuminated with the second wavelength, the second sub-element is also dark with a correspondingly low brightness relative to a background, or that when illuminated with the first wavelength, the first sub-element is brightly detected by the detector and when illuminated with the second wavelength, the second sub-element is also brightly detected with a correspondingly high brightness relative to a background, whereby an image of the sub-elements is generated by the detector during image recording, wherein - to determine the relative speed on the basis of a quotient of the spatial distance and the time interval between the first and the second time - an evaluation device is used to check whether the sub-elements in the image are shown in a predeterminable relative position to one another, wherein the sub-elements have shifted relative to one another in the predeterminable relative positioning during the mapping in such a way that the code is readable or decodable, and whereby, as soon as the code is readable or decodable, the determination of the relative speed takes place on the basis of a quotient of the spatial distance and the time interval between the first and the second time point.

[0012] Furthermore, according to claim 16, a device for carrying out a method for determining a relative speed between an object and a detector is specified, wherein a relative movement between the object and the detector can take place in a direction of movement, wherein the object has at least one detection element in the form of a code divided into at least two sub-elements, wherein the sub-elements are arranged at a predeterminable spatial distance from one another at predeterminable positions on, at or in the object and are image elements of an overall image of the code, wherein during the possible relative movement and for image recording by the detector, a first sub-element can be illuminated at a first predeterminable time for a predeterminable first illumination duration with a first light having a first wavelength and after a time interval, a second sub-element can be illuminated at a later second predeterminable time for a predeterminable second illumination duration with a second light having a second wavelength, where the wavelengths are chosen such that that when illuminated with the first wavelength, the first sub-element is dark and when illuminated with the second wavelength, the second sub-element is also dark with a correspondingly low brightness relative to a background, detectable by the detector, or that when illuminated with the first wavelength, the first sub-element is bright and when illuminated with the second wavelength, the second sub-element is also bright and can be detected by the detector with a correspondingly high brightness relative to a background, whereby an image of the sub-elements can be generated in the image recording by the detector, wherein - for determining the relative speed on the basis of a quotient of the spatial distance and the time interval between the first and the second time - it can be checked by means of an evaluation device whether the sub-elements in the image are depicted in a predeterminable relative position to one another, wherein the sub-elements have shifted relative to one another in the predeterminable relative positioning during the mapping in such a way that the code is readable or decodable, and whereby, as soon as the code is readable or decodable, the determination of the relative speed can be carried out on the basis of a quotient of the spatial distance and the time interval between the first and the second time point.

[0013] In accordance with the invention, it was first recognized that a particularly reliable determination of the relative speed between an object and a detector is possible with the aid of predeterminable illumination during the possible relative movement and suitable image recording by the detector using structurally simple means. The terms "possible relative movement" and "possible direction of movement" mean that the determination of the relative speed between an object and a detector also covers the case in which the relative speed is zero, i.e. no relative speed occurs in any direction of movement. If a relative movement does occur, it then occurs in the "possible direction of movement". Thus, the term "relative speed" in this document also covers the case in which the relative speed is zero.

[0014] Specifically, the object has at least one detection element in the form of a code, divided into at least two sub-elements, wherein the sub-elements are arranged at a predeterminable spatial distance from one another at predeterminable positions on, at or in the object and are image elements of an overall image of the code. During the relative movement, a first sub-element is illuminated with a first light having a first wavelength at a first predeterminable point in time for a predeterminable first illumination duration. After a time interval, at a later second predeterminable point in time, a second sub-element is illuminated with a second light having a second wavelength for a predeterminable second illumination duration.

[0015] In a first alternative, the wavelengths are selected such that, when illuminated with the first wavelength, the first sub-element is detected by the detector as dark according to its remission spectrum, and when illuminated with the second wavelength, the second sub-element is also detected by the detector as dark according to its remission spectrum with correspondingly low brightness relative to a background. In a second alternative, the wavelengths are selected such that, when illuminated with the first wavelength, the first sub-element is detected by the detector as bright according to its remission spectrum, and when illuminated with the second wavelength, the second sub-element is detected by the detector as bright according to its remission spectrum with correspondingly high brightness relative to a background.“Bright” or “dark” mean intensities of brightness that can be distinguished by the detector used due to its sensitivity, so that a contrast between the illuminated sub-elements and the background can be perceived by the detector under suitable lighting.

[0016] In an image captured by the detector, the method creates an image of the subelements. The brightness values ​​detected by the detector are integrated during the image capture.

[0017] To determine the relative speed, an evaluation device is used to check whether the sub-elements in the image are shown in a predeterminable relative position to one another, wherein the sub-elements have shifted relative to one another in the predeterminable relative position during the image such that the code is readable or decodable, and wherein, as soon as the code is readable or decodable, the determination of the relative speed takes place on the basis of a formation of a quotient from the spatial distance and the time interval between the first and the second time.

[0018] For example, the predeterminable relative positioning can mean the positioning of the sub-elements in the undivided state of the detection element. In this case, the sequential imaging of the sub-elements during image acquisition essentially results in the sub-elements being combined to form the undivided detection element. The undivided detection element can be seen in the image. As an alternative to this complete reassembly of the detection element in the image, any predeterminable relative positioning can be selected during evaluation using the evaluation device. The relative speed is determined based on the formation of a quotient from the predeterminable spatial distance between the sub-elements and the time interval between the first and second points in time.If, for example, the predeterminable relative positioning is the combined position of the sub-elements to form the undivided detection element, the speed results directly from the quotient of the spatial distance of the arrangement of the sub-elements and the time interval between the first and second points in time. If a different predeterminable relative positioning is selected in the image, the spatial distance between the divided detection elements is no longer to be selected when forming the quotient, but rather a distance corresponding to the currently selected predeterminable relative positioning. For example, a smaller distance if the selected predeterminable relative positioning means that the sub-elements are not yet combined with the detection element in the undivided state.

[0019] For carrying out the method according to the invention, a device according to the invention has at least one detector, an illumination device for generating the first light and the second light and an evaluation device for checking the predeterminable relative positioning.

[0020] With the method according to the invention and the corresponding device according to the invention, a particularly reliable determination of the relative speed is possible with structurally simple means, merely by suitable arrangement and illumination of sub-elements of at least one detection element.

[0021] Advantageously, a monochrome camera can be used as the detector, preferably a camera with a pixel sensor. Such a camera can ensure reliable image capture of both bright and dark elements. Further advantageously, the pixel sensor can be designed as a CMOS sensor, CCD sensor, or line sensor.

[0022] In principle, it is desirable to select a short illumination duration, preferably a flash, so as not to interfere, for example, with a position detection process between the object and the detector, which also takes place based on a predefined illumination. Advantageously, the first illumination duration can be between approximately 10 and approximately 200 µs and / or the second illumination duration can be between approximately 10 and approximately 200 µs. When selecting the illumination duration, the aforementioned avoidance of interference with other detection methods, for example, must be ensured, while also ensuring reliable image acquisition through sufficiently long first and / or second illumination durations.

[0023] The time interval or pause between the first lighting period and the second lighting period can be approximately 0.5 to 20 ms, depending on the application.

[0024] Furthermore, with a view to particularly reliable image recording, the background can have a lower reflectivity than the sub-elements. It should be noted that during image recording, part of the background usually lies in a viewing window of the detector. The background can be designed accordingly to ensure reliable image recording. For example, in a simple case, the background can be white and the detection elements black or dark. Alternatively, the background can be black or dark and the sub-elements light or white. Further alternatively, the background can be designed such that it reflects less than the sub-elements when illuminated with the first and / or second wavelength. For example, the background can be designed such that it has only 50% of the reflectivity or reflectivity of the sub-elements.

[0025] In a particularly simple embodiment of the method, the first wavelength and the second wavelength can be the same. For example, the sub-elements can be designed as black or identically colored sub-elements that are suitably illuminated with the first and second wavelengths, which are identical, to ensure reliable image acquisition by the detector. This particularly simple embodiment allows the relative speed to be reliably determined.

[0026] At this point it should be noted that throughout this document the terms “wavelength” and “illumination wavelength” can refer not only to an isolated wavelength but also to a wavelength range or a combination of different individual wavelengths and / or wavelength ranges across the entire electromagnetic spectrum. In this respect the term “wavelength” or “illumination wavelength” is synonymous with one or more individual wavelengths and / or one or more wavelength ranges. The use of the term “color” is not restricted to the visible wavelength range. This also includes the entire electromagnetic spectrum. When using the term “color,” this can be understood as merely an example of a section of the electromagnetic spectrum that relates to the visible wavelength range.

[0027] In a further advantageous embodiment of the method according to the invention, the sub-elements can be designed in different colors or have different remission spectra. In this case, too, a reliable determination of the relative speed is possible if the wavelengths are selected such that the illuminated sub-elements are detected as dark or bright—and thus contrasting—in a suitable manner. In this case, too, the wavelengths can be fundamentally the same, provided the color design or the remission spectra of the sub-elements is or are selected such that suitable dark or bright detection is possible.

[0028] Although the above-described embodiments allow for determining the relative velocity, they do not allow for determining the corresponding direction of movement. However, if the sub-elements are suitably designed in different colors, the direction of movement can also be detected with a suitable selection and sequence of wavelengths. In this case, the wavelengths must be selected differently.Specifically, the wavelengths can be selected such that when illuminated with the first wavelength, the first sub-element is dark and the second sub-element is bright, and when illuminated with the second wavelength, the first sub-element is bright and the second sub-element is dark with a correspondingly low or high brightness relative to the background, or that when illuminated with the first wavelength, the first sub-element is bright and the second sub-element is dark, and when illuminated with the second wavelength, the second sub-element is bright and the first sub-element is dark with a correspondingly high or low brightness relative to the background.

[0029] By knowing and taking into account the sequence of the first and second illumination durations with the corresponding first and second wavelengths and knowing the color configuration of the sub-elements, it can be determined with appropriate evaluation whether the imaging of the sub-elements has led to an image correlating with a known speed and direction of movement.

[0030] Furthermore, with a view to particularly reliable determination of the relative speed and, if applicable, the direction of movement, the sub-elements can be arranged along the direction of movement. To determine speeds in directions deviating from the direction of movement, the sub-elements can additionally be arranged along a corresponding, predeterminable further direction running at an angle to the direction of movement.

[0031] In an arrangement of at least two sub-elements as described above, it is fundamentally only possible to determine one speed that correlates with the spatial distance between the sub-elements and the time interval between the first and second times of illumination. To determine several different speeds, the sub-elements can be arranged in a particularly advantageous manner in several arrangements with different, predeterminable spatial distances from one another, each at predeterminable positions on, at, or in the object. When implementing these multiple arrangements, a number of speeds corresponding to the number of multiple arrangements can be determined if the spatial distances between the sub-elements in the arrangements are all different.

[0032] The subelements are image elements of an overall code image. Such image elements can be easily printed onto a suitable object to ensure the desired arrangement of the subelements.

[0033] In a particularly advantageous embodiment, the at least one code can be a data matrix code or a barcode with multiple bars. Such codes can be particularly easily detected and evaluated by suitable detectors.

[0034] If a barcode is used as the at least one detection element, the bars of the barcode can be alternately colored to form sub-elements, wherein preferably several barcodes can be arranged one above the other in a predeterminable manner in an image plane and / or the differently colored sub-elements can be spatially shifted relative to one another. With a suitable selection of the wavelengths and a suitably selected time interval between the illuminations, differently colored sub-elements shifted in this way can be converted back into a readable barcode in the image generated by the image recording, as it existed before the sub-elements were shifted relative to one another.

[0035] In order to avoid interference with other lighting-related determinations or evaluations, preferably on or with the same object, a color design of the sub-elements and the first wavelength and / or the second wavelength can be selected to be coordinated with one another in such a way that additional illumination of a further code arranged on or at the object, in particular a data matrix code or a barcode, with the first light and / or the second light does not cause any interference or falsification of reflections and / or absorptions generated, for example, during a position determination with the further code.

[0036] Furthermore, with a view to particularly reliable determination of the relative speed, the time interval and / or the sequence of illumination with the first light and the second light can be specified. This specification can preferably be made by means of a control device and further preferably randomly or pseudo-randomly. By specifying the time interval and / or the sequence of illumination with the first light and the second light, a very specific - expected - detection can be generated by the detector, whereby it is assumed that the relative speed is within an expected range.The image recording and representation of the sub-elements generated by the detector in such a case can be compared by means of an evaluation device with an image expected based on the selected parameters in the form of the time interval and / or the sequence of illumination with the first light and the second light. If a detected deviation between the generated image and the expected image exceeds a predeterminable threshold, suitable measures can be taken to influence or even prevent further relative movement between the object and the detector, or the deviation can be displayed. Such a deviation can indicate a malfunction in the image processing, for example in the detector. If no deviation occurs, a very reliable speed measurement can be assumed.

[0037] For a particularly reliable determination of the relative velocity, the time interval can be specified such that the object or its sub-elements do not move out of the detector's viewing window during the time interval. This ensures, for example, that all sub-elements are imaged as required during image acquisition, thus ensuring that no information is lost when determining the relative velocity.

[0038] To reduce the influence of unwanted extraneous light during image acquisition, the detector can capture the image only during the first illumination period and the second illumination period and / or not capture the image between the first and second illumination periods. This ensures image acquisition of the subelements, while simultaneously preventing unwanted extraneous light from reducing the quality of the image acquisition or the signal-to-noise ratio between the illumination periods. Advantageously, a shutter for the detector or camera can be used for this purpose; for example, this shutter is only open during the first and second illumination periods and closed otherwise. This allows for particularly reliable reduction of extraneous light.

[0039] There are now various possibilities for advantageously embodying and developing the teaching of the present invention. Reference is made, on the one hand, to the dependent claims and, on the other hand, to the following explanation of preferred embodiments of the method according to the invention and the device according to the invention with reference to the drawing. In conjunction with the explanation of the preferred embodiments with reference to the drawing, generally preferred embodiments and developments of the teaching are also explained. The drawing shows: Fig. 1 shows a schematic representation of a detection element in the form of a data matrix code which can be used in an embodiment of the method according to the invention and which is divided into two differently coloured sub-elements, wherein an image of the sub-elements is shown with appropriate illumination and with increasing relative speed between the object and the detector, Fig. 2 in a schematic representation in a further embodiment, a detection element also designed as a data matrix code, which is divided into two differently colored sub-elements, the background being dark in this embodiment, Fig. 3 in a further embodiment, the use of five detection elements designed as barcodes with corresponding division into two different colored sub-elements, Fig. 4 shows a schematic representation of a scenario as in Fig. 3, but with twice the distance traveled during the relative movement, Fig. 5 in a schematic representation a similar scenario as in Fig. 3, but with an exchange of wavelengths and thus of illumination with the first light and the second light, and Fig. 6 shows a schematic representation of a typical sequence of illumination times for an image acquisition by a detector.

[0040] Based on the Fig. 1, an embodiment of the method according to the invention for determining the relative speed between an object and a detector 1 is explained, wherein the detector 1 is designed as a camera. The object has a detection element 2 designed as a data matrix code, which is divided into two sub-elements 3 and 4 on a background 5, which are arranged at a spatial distance ds from one another at predeterminable positions on the object. The sub-elements 3 and 4 have different colors, wherein the Fig. 1 right sub-element 3 exemplary red and the one in Fig. 1, sub-element 4 shown on the left is designed in blue. This color difference is illustrated by the different hatching in sub-elements 3 and 4.

[0041] In a), detection element 2 is shown in its unchanged form. In b), it is colored accordingly in blue and red. In c), the division of detection element 2 into subelements 3 and 4 at a distance ds is shown.

[0042] The sequence changing from c1) to c5) shows images of the sub-elements 3 and 4 with the detector 1 in a corresponding image recording, whereby the sequence correlates with an increasing relative speed. In case c1), a stationary situation without relative speed and relative movement is still shown. The image recording is generated by illuminating the red first sub-element 3 at a first predeterminable time for a predeterminable first illumination duration with a first blue light having a first wavelength 6 and the blue second sub-element 4 at a later second predeterminable time for a predeterminable second illumination duration with a second red light having a second wavelength 7. In the still stationary situation c1), the sub-elements 3 and 4 have the same distance ds as when the detection element 2 was originally divided into the sub-elements 3 and 4 according to the partial representation c).

[0043] In the areas c2) and c3) there is now a relative velocity that increases from c2) to c3). Accordingly, the sub-elements 3 and 4 are located in the respective Fig. 1 shown illustration. In the situation according to c4), the sub-elements 3 and 4 are now depicted in a relative positioning to one another that corresponds to the original design of the detection element 2 in its form as a data matrix code. This predeterminable relative positioning of the sub-elements 3 and 4 to one another can now be detected by an evaluation device, namely by the fact that the data matrix code is readable again in the first place. In the situations according to c1), c2), and c3), such readability of the data matrix code is not possible.

[0044] Therefore, in situation c4), the speed can be determined by calculating the quotient of the spatial distance ds and the time interval dt between the first illumination period and the second illumination period. As soon as the Data Matrix code is readable again, this unambiguous speed determination can be performed using the aforementioned quotient calculation.

[0045] If the speed increases even further, a situation like in c5) can arise in Fig. 1, in which the sub-elements 3 and 4 are again shown with a distance to each other.

[0046] In the embodiment according to Fig. 1, it is possible to illuminate both the first sub-element 3 and the second sub-element 4 together with the first light and the second light. Selective illumination of only one sub-element 3 or the other sub-element 4 is not necessary, since the color design of the sub-elements 3 and 4 and the corresponding choice of the wavelengths 6 and 7 lead to the desired image of the sub-elements 3 and 4 according to situations c1) to c5). If no color design of the sub-elements and no color difference between the first light and the second light is selected, it is preferable to carry out selective illumination of the sub-elements 3 and 4 in order to obtain only one image of the illuminated sub-element 3 or 4 in each case.However, this selective illumination and evaluation is not absolutely necessary, and the method also functions when sub-elements 3 and 4 are not colored and wavelengths 6 and 7 are not different. Checking whether the specified relative positioning of sub-elements 3 and 4 is present in the image, for example by determining the readability of a data matrix code, is also possible when sub-elements 3 and 4 are not colored and wavelengths 6 and 7 are the same. In this respect, a reliable determination of the relative speed is always possible.

[0047] In the scenarios according to Fig. 1 and the color design of the component elements 3 and 4 thus present a situation where, when the scenario with the component elements 3 and 4 and the background 5 is completely illuminated in red, only the blue component element 4 is detected as dark. When everything is illuminated in blue, only the red component element 3 is detectable. It is desirable to choose a very short, flash-like illumination duration with blue and red light in order not to interfere with possible other illumination-based detection processes, such as position determination. Due to the spatial separation of the component elements 3 and 4 of the data matrix code at a distance ds, decoding of the data matrix code is no longer possible.If the detector 1 now moves relative to the object, the two sub-elements 3 and 4 in the image move relative to one another, depending on the speed, the spatial distance ds and the time interval dt between the first and the second time of illumination. With a very specific combination of these three parameters - speed, distance ds and time interval dt - a data matrix code is produced in the image according to c4) which can be decoded. In this situation, it can be assumed that the speed is within a certain range due to the checksum CRC. In the case of the situation according to . Fig. 1, detector 1 moves to the left relative to sub-elements 3 and 4, so that initially during the blue exposure the detector 1 is located above the red sub-element 3, which is then detected as dark. After the time interval dt the detector is located above the blue sub-element 4 and exposes it to red, so that this too appears dark and is superimposed on the previous image of the first sub-element 3. In order to obtain a readable code in the other direction of movement the exposure must be in the reverse order, i.e. first red and then blue. In both cases the speed is given by v = ds / dt, regardless of the direction of movement. Taking into account, i.e. knowing the illumination sequence - first blue and then red or first red and then blue - the direction of movement can also be deduced.This detection of the direction of movement is only possible with appropriate color design, for example as in the scenario in . Fig. 1 and not possible with a design of the same colour of the sub-elements 3 and 4 and the same illumination wavelengths 6 and 7.

[0048] For the prior determination of a suitable time interval dt, an acceleration sensor can be used, for example, which can specify the time interval dt if necessary.

[0049] To determine different speeds, multiple arrangements of sub-elements 3 and 4 can be provided on the object, with sub-elements 3 and 4 being arranged at different spatial distances ds from each other. The underlying codes can have different content to enable reliable inference of the relative speed upon detection of a code. Depending on the speed, for example, only one readable code is suitable.

[0050] The method can also be used to detect a standstill. For this purpose, both sub-elements 3 and 4 can be arranged on, at, or in the object without being shifted. These can then only be decoded if there is no relative velocity. In another case, the differently colored sub-elements 3 and 4 would be imaged at a distance from each other.

[0051] In an advantageous embodiment of the method, the detection elements used to determine the relative speed can be implemented multiple times on an object. In each case, the detection elements can be provided separately for speed determination. In this respect, they can be implemented independently of codes used, for example, for position determination.

[0052] If different arrangements of sub-elements 3 and 4 are implemented to determine different speeds, a suitable control device can vary the time interval and the sequence of the exposure colors or wavelengths 6 and 7, preferably randomly or pseudo-randomly. This then results in speeds determined in different ways, i.e. with different parameters. This enables a comparison of the parameters specified by the control device with the images generated by the image recording. In other words, the images generated by the image recording must "match" the selected parameters with regard to the time interval dt and the sequence of the exposure colors. In the event of discrepancies, this can be used to conclude that the processing chain between the illumination control and the determined speed is functioning incorrectly.In this way, a “black channel” formed by the detector 1 and the evaluation device can be verified for correctness by means of the variation of the parameters by the control device.

[0053] Fig. 2 shows a schematic representation of a further embodiment of the present invention, wherein the Fig. 2 shown scenarios a) to c5) to the corresponding scenarios in Fig. 1. However, a dark background 5 has been chosen here. Otherwise, to avoid repetition, please refer to the explanations for Fig. 1.

[0054] Fig. Figure 3 shows a schematic representation of detection elements 2 according to a further embodiment, which are generated on the basis of a barcode. According to Part I. in Fig. 3, five codes are selected, which are converted into five barcodes and arranged one above the other in an image plane according to II. Thus, II. shows five detection elements 2 in the form of "short" barcodes arranged one above the other. The transition from I. to II. is shown in the right part of the Fig. 3 is shown schematically, with the code "-01" selected as an example, which is shown as the second code from the top. According to II., the five different barcodes are merely positioned one above the other, or next to each other in the image plane. This is not a "stacked barcode" or similar.

[0055] According to III., for example, all bars 8 of the codes are alternately colored blue and red. The blue and red modules thus generated, formed by the respectively colored bars 8 from all blue or red bars 8 of a respective barcode, which serve as sub-elements 3 (blue) and 4 (red), are spatially shifted against each other according to IV. The degree of shift is explained in the table in Part IV. The two modules of the first detection element 2 are shifted by 2 mm to the left (blue) and to the right (red). This shift distance of 2 mm is chosen only as an example, so that other shift distances are also possible. The modules of the second detection element 2 are each shifted by only 1 mm to the left (blue) and right (red). The modules of the third detection element 2 are not shifted, and the modules of the fourth and fifth detection element 2 are different from the situation in Part III.shifted in the opposite direction to the first two detection elements 2, so that the overall shift situation shown in Part IV. results.

[0056] Part V now presents an image obtained after a corresponding exposure. First, the image was briefly exposed to blue light, so that the red modules are depicted in the position they were after the relative displacement performed according to Part IV. In this respect, the situation regarding the red modules is unchanged from Part IV.

[0057] After waiting for the time interval dt, a short red exposure was applied, resulting in an image of the blue modules with an extent corresponding to the displacement that had occurred in the meantime. The displacement here is ds = -2 mm.

[0058] Part VI shows an image through a monochrome area sensor chip. A line-by-line decoding reveals that only the second code from the top can be decoded. The corresponding code content is "-01" according to the above explanation. The velocity can then be calculated as shown on the right in Part VI. It should be emphasized that this is merely an example implementation of the method. The determined velocity is -0.5 m / s.

[0059] Fig. 4 shows in a schematic representation essentially the same scenario as in Fig. 3 with first red and then blue illumination and the same direction of movement, whereby the displacement here is doubled during the time interval dt. This doubled distance results from the doubling of the time interval dt.

[0060] Since both the time interval dt and the distance ds have been doubled, the same speed of -0.5 m / s results as in Fig. 3. This shows that the decoding process itself is independent of the time interval dt. The speed is still reliably determined.

[0061] Fig. 5 shows a further schematic representation of a scenario according to Fig. 3, where the sequence of exposure has been reversed, so that red is exposed first, followed by blue. The corresponding image through the detector is shown in Part IX. Here, the blue modules - sub-element 3 - are made of Fig. 3 remains unchanged. However, the red modules - sub-element 4 - have been moved to the right by the distance ds.

[0062] Here too, according to Part X., it is clear that the pure decoding system ultimately does not know or need not know the time interval dt, but that with the method according to the invention, a reliable speed determination is possible overall, since in this embodiment the correct speed of -0.5 m / s is also obtained, as in the scenarios according to the Fig. 3 and Fig. 4 results.

[0063] Fig. Figure 6 shows a schematic representation of a typical sequence of illumination durations t 1 and t 2 with a pause or a time interval t delta between the lighting periods t 1 and t 2 . The temporal progression is plotted against the illumination over a time t. With such short illumination durations t 1 and t 2 can be prevented that between these lighting periods t 1 and t 2unwanted extraneous light is picked up by detector 1. This could be achieved by opening a shutter of a sensor chip of detector 1 only during the illumination periods t 1 and t 2 open and otherwise remains closed.

[0064] This increases image quality and reduces signal-to-noise ratio. If the shutter of the sensor chip remains open between the illumination periods t 1 and t 2 closed, the extraneous light is largely blocked. For example, during the lighting period t 1 red. The shutter is then closed. After the time t delta the shutter is opened again. During the subsequent illumination period t 2 For example, it is exposed to blue light.

[0065] This ambient light reduction can be achieved using different sensor chips. In one version, during an illumination period t 1 or t 2 normally exposed and in between the target voltage is reduced to a minimum, so that the sensor is not very sensitive to light in this intermediate range.

[0066] With another sensor technology, two different inputs can be used, which act as shutter t 1 and shutter t 2 can be used. Binning can be used for reading, or the two inputs can be combined using an external circuit.

[0067] There are also sensor chips that allow multiple exposures before the data is read out. All such sensor chips can be used in the method according to the invention.

[0068] With regard to further advantageous embodiments of the teaching according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

[0069] Finally, it should be expressly pointed out that the embodiments described above serve only to explain the claimed teaching, but do not limit it to these embodiments. List of reference symbols 1 detector 2 detection element 3 sub-elements 4 sub-elements 5 Background 6 first wavelength 7 second wavelength 8 bars ds spatial distance dt time interval t time t 1 Lighting duration t 2 Lighting duration t delta Duration

Claims

[1] Method for determining a relative speed between an object and a detector (1), wherein a relative movement between the object and the detector (1) can take place in one direction of movement, wherein the object has at least one detection element (2) in the form of a code divided into at least two sub-elements (3, 4), wherein the sub-elements (3, 4) are arranged at a predeterminable spatial distance (ds) from one another at predeterminable positions on, at or in the object and are image elements of an overall image of the code, wherein during the possible relative movement and for an image recording by the detector (1), a first sub-element (3) is illuminated at a first predeterminable time for a predeterminable first illumination duration (t 1) with a first light having a first wavelength (6) and after a time interval (dt) a second sub-element (4) at a later second predeterminable time for a predeterminable second illumination duration (t 2 ) are illuminated with a second light having a second wavelength (7), wherein the wavelengths (6, 7) are selected such that that when illuminated with the first wavelength (6), the first sub-element (3) is detected as dark and when illuminated with the second wavelength (7), the second sub-element (4) is also detected as dark with a correspondingly low brightness relative to a background (5) by the detector (1), or that when illuminated with the first wavelength (6), the first sub-element (3) is brightly detected and when illuminated with the second wavelength (7), the second sub-element (4) is also brightly detected with a correspondingly high brightness relative to a background (5) by the detector (1), wherein an image of the sub-elements (3, 4) is generated in the image recording by the detector (1), wherein - to determine the relative speed on the basis of a quotient of the spatial distance (ds) and the time interval (dt) between the first and the second time - an evaluation device is used to check whether the sub-elements (3, 4) are depicted in the image in a predeterminable relative position to one another, wherein the sub-elements (3, 4) have shifted relative to one another during the imaging in the predeterminable relative positioning such that the code is readable or decodable, and whereby, as soon as the code is readable or decodable, the determination of the relative speed takes place on the basis of a quotient of the spatial distance (ds) and the time interval (dt) between the first and the second time point. [2] Method according to claim 1, characterized bythat a monochrome camera, preferably a camera with a pixel sensor, is used as the detector (1), wherein the pixel sensor is further preferably designed as a CMOS sensor or CCD sensor or as a line sensor. [3] Method according to claim 1 or 2, characterized by that the first lighting duration (t 1 ) between about 10 and about 200 µ s and / or the second illumination duration (t 2 ) is between about 10 and about 200 µ s and / or that the time interval (dt) or a pause between the first illumination period (t 1 ) and the second illumination duration (t 2 ) is approximately 0.5 to 20 ms. [4] Method according to one of claims 1 to 3, characterized by that the background (5) has a lower reflectivity than the sub-elements (3, 4). [5] Method according to one of claims 1 to 4, characterized by that the first and second wavelengths (6, 7) are the same. [6] Method according to one of claims 1 to 4, characterized by that the sub-elements (3, 4) are of different colors or have different remission spectra. [7] Method according to claim 6, characterized by that the wavelengths (6, 7) are chosen such that that when illuminated with the first wavelength (6), the first sub-element (3) is dark and the second sub-element (4) is bright, and when illuminated with the second wavelength (7), the first sub-element (3) is bright and the second sub-element (4) is dark with correspondingly low or high brightness relative to the background (5) of the detector (1), or that when illuminated with the first wavelength (6), the first sub-element (3) is bright and the second sub-element (4) is dark, and when illuminated with the second wavelength (7), the second sub-element (4) is bright and the first sub-element (3) is dark with correspondingly high or low brightness relative to the background of the detector (1). [8] Method according to one of claims 1 to 7, characterized by that the sub-elements (3, 4) are arranged along the direction of movement and preferably additionally along a predeterminable further direction running at an angle to the direction of movement. [9] Method according to one of claims 1 to 8, characterized by that the sub-elements (3, 4) are arranged in several arrangements with different predeterminable spatial distances (ds) from one another at predeterminable positions on, at or in the object. [10] Method according to one of claims 1 to 9, characterized bythat at least one code is a Data Matrix code or a barcode with multiple bars. [11] Method according to claim 10, characterized by that the code is a barcode, wherein the bars (8) of the barcode are alternately designed in different colors to form sub-elements (3, 4), wherein preferably a plurality of barcodes are arranged one above the other in a predeterminable manner in an image plane and / or the sub-elements (3, 4) of different colors are arranged spatially displaced from one another. [12] Method according to one of claims 1 to 11, characterized bythat a color design of the sub-elements (3, 4) and the first wavelength (6) and / or the second wavelength (7) are selected to be coordinated with one another in such a way that additional illumination of a further code arranged on or at the object, in particular a data matrix code or a barcode, with the first light and / or the second light does not cause any interference or falsification of reflections and / or absorptions generated during a position determination with the further code. [13] Method according to one of claims 1 to 12, characterized by that the time interval (dt) and / or a sequence of illumination with the first light and the second light are or will be predetermined - preferably by means of a control device and further preferably randomly or pseudo-randomly. [14] Method according to one of claims 1 to 13, characterized bythat the time interval (dt) is predetermined in such a way that the object or the sub-elements (3, 4) do not move out of a viewing window of the detector (1) during the time interval (dt). [15] Method according to one of claims 1 to 14, characterized by that the image recording by the detector (1) only takes place during the first illumination period (t 1 ) and the second illumination duration (t 2 ) and / or between the first lighting period (t 1 ) and the second illumination duration (t 2 ) has not been carried out. [16] Device for carrying out a method for determining a relative speed between an object and a detector (1), preferably for carrying out a method according to one of claims 1 to 15, wherein a relative movement between the object and the detector (1) can take place in a direction of movement, wherein the object has at least one detection element (2) in the form of a code divided into at least two sub-elements (3, 4), wherein the sub-elements (3, 4) are arranged at a predeterminable spatial distance (ds) from one another at predeterminable positions on, at or in the object and are image elements of an overall image of the code, wherein during the possible relative movement and for an image recording by the detector (1), a first sub-element (3) is illuminated at a first predeterminable time for a predeterminable first illumination duration (t 1 ) with a first light having a first wavelength (6) and after a time interval (dt) a second sub-element (4) at a later second predeterminable time for a predeterminable second illumination duration (t 2 ) can be illuminated with a second light having a second wavelength (7), wherein the wavelengths (6, 7) are selected such that that when illuminated with the first wavelength (6), the first sub-element (3) is dark and when illuminated with the second wavelength (7), the second sub-element (4) is also dark with a correspondingly low brightness relative to a background (5) can be detected by the detector (1), or that when illuminated with the first wavelength (6), the first sub-element (3) is bright and when illuminated with the second wavelength (7), the second sub-element (4) is also bright with a correspondingly high brightness relative to a background (5) can be detected by the detector (1), wherein an image of the sub-elements (3, 4) can be generated in the image recording by the detector (1), wherein - for determining the relative speed on the basis of a quotient of the spatial distance (ds) and the time interval (dt) between the first and the second time - it can be checked by means of an evaluation device whether the sub-elements (3, 4) are depicted in the image in a predeterminable relative positioning to one another, wherein the sub-elements (3, 4) have shifted relative to one another during the imaging in the predeterminable relative positioning such that the code is readable or decodable, and wherein, as soon as the code is readable or decodable, the determination of the relative speed can be carried out on the basis of a formation of a quotient of the spatial distance (ds) and the time interval (dt) between the first and the second time point.

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