DE102019202797A1 - Method and device for determining the relative speed between an object and a detector - Google Patents

Abstract

With regard to a particularly simple and reliable determination of the relative speed between an object and a detector (1) with structurally simple means, a method for determining the relative speed between an object and a detector (1) is specified, with a relative movement between the object and the Detector (1) can take place in one direction of movement, the object having at least two detection elements (2, 3) which have a different reflectance spectrum relative to a predeterminable region (4) of the object, and at least one of the detection elements (2, 3) adjoins the area (4), the detection elements (2) alternating with light during the possible relative movement and during a predefinable duration (Δ t) of an image recording by the detector (1) by means of a lighting device in a predefinable sequence and predefinable respective illumination duration different we Llenlängen (6, 7) are illuminated and the wavelengths (6, 7) are selected such that at least one first detection element (2) of the detector (1) is dark when illuminated with at least one first wavelength (6) and dark when illuminated with at least one second wavelength (7) different from the at least one first wavelength (6) light, at least one further second detection element (3) when illuminated with the at least one second wavelength (7) dark and when illuminated with the at least one first Wavelength (6) light and the area

Description

The invention relates to a method for determining the relative speed between an object and a detector, wherein a relative movement between the object and the detector can take place in one direction of movement. The present invention also relates to a corresponding device for carrying out such a method.

Methods and devices of the type mentioned are known from practice and exist in different embodiments. Such methods and devices are used, in particular, in industrial areas in which objects moving relative to a detector must be monitored, preferably in an automated manner.

For example, from the EP 0 532 169 A1 a method is known in which the relative speed between an object on a surface and a detector can be determined with a CCD array. The relative speed is determined on the basis of the sequence of individual image recordings.

Furthermore, from the EP 1 729 086 A1 a method for image processing is known, wherein relative speeds between an object and a detector are determined.

The known methods for determining the relative speed are well suited for the applications described in the above prior art. However, in many applications today it is necessary to achieve a particularly high level of reliability when determining the relative speed. The methods known from the prior art are only suitable to a limited extent for this purpose, since, in particular if one of the individual measuring components in the image processing chain fails, it cannot immediately be determined that a speed measurement is faulty. The aim here is to increase the reliability of the determination of the relative speed.

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

According to the invention, the above object is achieved by a method with the features of claim 1 and by a device with the features of claim 11.

Thereafter, the method according to the invention forms a method for determining the relative speed between an object and a detector, whereby a relative movement between the object and the detector can take place in one direction of movement,
wherein the object has at least two detection elements which have a different remission spectrum relative to a predeterminable area of the object and which differ from one another, at least one of the detection elements adjoining the area,
wherein the detection elements are alternately illuminated with light of different wavelengths during the possible relative movement and during a prescribable duration of an image recording by the detector by means of an illumination device in a prescribable sequence and a prescribable respective illumination duration,
wherein the wavelengths are selected such that at least one first detection element of the detector is dark when illuminated with at least one first wavelength and bright when illuminated with at least one second wavelength different from the at least one first wavelength, at least one further second detection element when illuminated with the at least one second wavelength dark and with an illumination with the at least one first wavelength light and the area both with an illumination with the at least one first wavelength and with an illumination with the at least one second wavelength dark or light with correspondingly lower or higher Brightness can be detected,
wherein, in the image recording generated in this way, the detector detects a brightness curve that is dependent on the remission spectrum of the area and the detection elements and on the different wavelengths of the illuminations with decreasing and / or increasing brightnesses in the possible direction of movement, and
wherein the relative speed is determined and / or based on a proportionality of a spatial width of a decreasing or increasing section of the brightness curve to the relative speed and taking into account one or more of the illumination periods
wherein based on a proportionality of a distance between two constant sections and / or a distance between centers of two constant sections and / or a width of a peak between two constant sections of the brightness curve to the relative speed and taking into account one or more of the illumination periods, the relative speed is determined.

Furthermore, according to claim 11, a device for performing a method for determining the relative speed between an object and a detector is specified,
whereby a relative movement between the object and the detector can take place in one direction of movement,
wherein the object has at least two detection elements which have a different remission spectrum relative to a predeterminable area of the object and which differ from one another, at least one of the detection elements adjoining the area,
wherein the detection elements can be illuminated alternately with light of different wavelengths during the possible relative movement and during a prescribable duration of an image recording by the detector by means of an illumination device in a prescribable sequence and illumination duration,
wherein the wavelengths are selected such that at least one first detection element of the detector is dark when illuminated with at least one first wavelength and bright when illuminated with at least one second wavelength different from the at least one first wavelength, at least one further second detection element when illuminated with the at least one second wavelength dark and with an illumination with the at least one first wavelength light and the area both with an illumination with the at least one first wavelength and with an illumination with the at least one second wavelength dark or light with correspondingly lower or higher Brightness are detectable,
wherein, in the image recording generated in this way, a brightness curve that is dependent on the remission spectra of the area and the detection elements and on the different wavelengths of the illuminations with decreasing and / or increasing brightnesses in the possible direction of movement can be detected by the detector, and
wherein the relative speed can be determined and / or based on a proportionality of a spatial width of a decreasing or increasing section of the brightness curve to the relative speed and taking into account one or more of the illumination periods
where based on a proportionality of a distance between two constant sections and / or a distance between centers of two constant sections and / or a width of a peak between two constant sections of the brightness curve to the relative speed and taking into account one or more of the lighting periods, the relative speed can be determined.

In the manner according to the invention, it was first recognized that a particularly reliable determination of the relative speed between an object and a detector with the aid of predeterminable illumination during the possible relative movement and during an image recording by the detector is possible with structurally simple means. The expression "possible relative movement" and "possible direction of movement" means 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. there is no relative speed in any direction of movement. If there is a relative movement, this then takes place in the "possible direction of movement". The term “relative speed” in this document therefore also includes the case in which the relative speed is equal to zero.

Specifically, the object has at least two detection elements for this purpose, which have a remission spectrum that is different relative to a predeterminable region of the object and also different from one another. In other words, both the predeterminable area and the at least two detection elements have remission spectra or colors that differ from one another. At least one detection element is directly adjacent to the area.

During the possible relative movement and during a predeterminable duration of an image recording by the detector, the detection elements are alternately illuminated with light of different wavelengths by means of an illumination device, whereby both the sequence and the respective illumination duration of the light of different wavelengths can be specified. The wavelengths are selected such that the detector detects at least one first detection element dark when illuminated with at least one first wavelength and light when illuminated with at least one second wavelength different from the at least one first wavelength. Furthermore, at least one further second detection element is detected dark when illuminated with the at least one second wavelength and light when illuminated with the at least one first wavelength. Finally, the area is detected both in the case of illumination with the at least one first wavelength and in the case of illumination with the at least one second wavelength dark or light with correspondingly low or high brightness. In this context, light or dark means intensities of the brightness that can be differentiated by the particular detector used due to its sensitivity, so that a contrast between the illuminated detection elements and the area can be perceived by the detector with suitable lighting. For example, a turquoise-colored detection element illuminated with a blue wavelength appears bright, whereas an orange-colored detection element illuminated with a blue wavelength appears dark.

In the image recording generated in this way, a brightness curve that is dependent on the reflectance spectra of the area and the detection elements and on the different wavelengths of the illuminations with decreasing and / or increasing brightnesses in the possible direction of movement is detected by the detector. The brightnesses detected by the detector are integrated during the image recording period. In this respect, a moving darkly detected detection element, which is arranged on a lightly detected area, creates a section with decreasing brightness in the possible direction of movement.

Based on a proportionality of a spatial width of this decreasing or, in another case constellation, also increasing section of the brightness curve to the relative speed, the relative speed is then determined taking into account one or more of the illumination periods.

As an alternative or in addition to this, based on a proportionality of a distance between two constant sections and / or a proportionality of a distance from midpoints of two constant sections and / or a proportionality of a width of a peak between two constant sections of the brightness curve to the relative speed and taking into account an or several of the illumination periods determine the relative speed. There are therefore different options for determining the relative speed, with decreasing or increasing sections or edges of the brightness curve and / or constant sections of the brightness curve and / or a peak in the brightness curve being taken into account. When the constant sections are taken into account, on the one hand the distance between the constant sections and on the other hand or additionally the distance from centers of the constant sections can be taken into account. If a peak in the brightness curve between two constant sections is taken into account, this peak can point in the direction of greater brightness or in the direction of lower brightness. In any case, the width of such a tip between two constant sections is relevant for determining the relative speed and not the direction in which the tip points.

By specifying the sequence and the respective illumination duration of the alternating light of different wavelengths within the duration of an image recording by the detector and taking into account the reflectance spectra or the color design of the detection elements and the area, a very specific - expected - brightness curve is generated and detected by the detector, it is further assumed that the level of the relative speed is in a range that is also expected. The brightness curve actually detected by the detector in a specific application can be compared by means of an evaluation device with the brightness curve expected on the basis of the selected lighting and detection element parameters prevention of a further relative movement between the object and the detector can be taken 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.

With the method according to the invention and the device according to the invention, a particularly reliable determination of the relative speed is thus possible with structurally simple means, only through suitable lighting and suitable remission spectra or color design of the detection elements and the area.

In an advantageous manner, a monochrome camera can be used as a detector, it being possible to use a camera with a pixel sensor. With such a pixel sensor, the course of brightness can be recorded - preferably in the direction of movement - particularly simply - pixel by pixel - and determined with regard to its width or length. In a further advantageous manner, the pixel sensor can be designed as a CMOS sensor or CCD sensor or as a line sensor.

With regard to a particularly clearly definable and easily generated brightness curve, the detection elements can be arranged adjacent to one another on, on or in the object. Such detection elements can, for example, be printed on the object or integrated into the object.

Furthermore, with a view to generating a particularly simple brightness curve, the detection elements can be arranged adjacent to one another in the direction of movement. This enables reliable detection of the brightness profile.

In principle, the detection elements can have very different shapes and contours, provided that a suitable color difference or contrast to the adjacent area can be realized. Can in a particularly simple way the detection elements have a rectangular contour. As an alternative to this, the detection elements can also have a different polygonal or polygonal contour, this not necessarily having to be a contour that is symmetrical in any way. For example, an edge profile of the detection elements that is inclined to the direction of movement can also be implemented. The specific shape of the detection elements may need to be taken into account in a suitable manner when determining the relative speed. In a further advantageous manner, the detection elements can be an element of a code, in particular a data matrix code or a barcode. Such codes are used, for example, when determining the position of objects moving relative to a detector in the industrial sector, the codes being attached to the objects. Such codes are characterized by clear contrasts to surrounding or bordering areas in order to enable reliable image recording and evaluation of the codes.

As an alternative to a flat configuration of the detection elements as described above with, for example, a rectangular contour, the detection elements can be implemented as linear or almost linear detection elements which extend in the direction of movement and which can be formed from individual pixels. In the case of linear detection elements, a brightness curve that results when the method is carried out will likewise be linear or almost linear, and here too, depending on the detector used, a brightness curve can result from individual pixels. The length of this linear brightness curve is in turn proportional to the relative speed, the relative speed being able to be determined here too, taking into account the recording time.

In a preferred embodiment of the teaching according to the invention, the area can be implemented as a light or white or as a dark or black area or background. As an alternative or in addition to this, the range can have a high or a low level of remission for at least one specifiable spectral range and / or for at least one wavelength. In this way, a reliable differentiation of the area of detection elements designed in different colors or of detection elements with different reflectance spectra can be realized.

In a particularly simple embodiment of the method according to the invention, the wavelength of the illumination can be changed from the at least one first wavelength to the at least one second wavelength after half the duration of the image recording. The detection elements are first illuminated with light of a first wavelength and then with light of a second wavelength different from the first wavelength, the first wavelength and the second wavelength being selected in such a way that a first detection element of the detector when illuminated with the first wavelength dark and light when illuminated with the second wavelength and a second detection element light when illuminated with the first wavelength and dark when illuminated with the second wavelength or vice versa with correspondingly low or high brightness relative to the area. In addition to this use of only two different wavelengths, which are changed after half the time of the image recording, numerous other possible combinations of illumination periods that are not even half the duration of the image acquisition and more than two illumination wavelengths are possible. For example, the change between a first and a second wavelength can already take place after a third of the duration of the image recording or only after two thirds of the duration of the image recording. When choosing the individual lighting durations for the lights with different wavelengths and also with the number of lights with different wavelengths used, the respective application must be taken into account. In a particularly simple embodiment of the method according to the invention, there are only two illuminations with different wavelengths, i.e. a two-color illumination, and also only two detection elements with different colors or remission spectra, the wavelength of the illumination being changed to the second wavelength after half the duration of the image recording.

With regard to a particularly reliable determination of the relative speed, the duration of the image recording can be specified in such a way that the object or the detection elements do not move or move out of a viewing window of the detector during the duration of the image recording. On the other hand, it is advantageous if the object - when using a pixel sensor - moves relatively at least along a plurality of pixels in order to enable a sufficient width of the brightness curve and thus a safe and reliable determination of the relative speed.

With the method according to the invention and the device according to the invention, it is also possible in a particularly advantageous manner that the direction of movement is determined taking into account the shape of the brightness curve and the sequence of the wavelengths of the illumination. Use can be made of the fact that, given the same sequence of the wavelengths of the illuminating light, the brightness curve has two different shapes for the same object, depending on which one Direction the object is moving. With an optical axis of the detector arranged perpendicular to the direction of movement, for example, a reliable distinction can be made as to whether the object is moving from left to right or from right to left, for example. Thus, with the method according to the invention and the device according to the invention, it is not only possible to reliably determine the relative speed, but also to reliably determine the direction of movement. For this purpose, known brightness curves that result when known wavelengths and detection elements are present, for which the respective direction of movement of the object is also known, can be used for comparison with currently detected brightness curves.

At this point it should be noted that throughout the document, the terms “wavelength” and “illumination wavelength” can refer to not only an isolated wavelength but also a wavelength range or a combination of different individual wavelengths and / or wavelength ranges in 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. There is no restriction to the visible wavelength range when using the term “color”. The entire electromagnetic spectrum is also included here. When using the term “color”, this can be understood as a mere exemplary designation of a section of the electromagnetic spectrum that relates to the visible wavelength range.

• 1 in einer schematischen Darstellung ein Sichtfenster eines bei einem Ausführungsbeispiel des erfindungsgemäßen Verfahrens verwendeten Detektors sowie den Detektor, wobei zwei Detektionselemente im Sichtfenster sichtbar sind,
• 2 in drei übereinanderliegenden schematischen Darstellungen, bei a) ein nach unten aufgetragener zeitlicher Ablauf während einer Bildaufnahme, wobei links neben den Detektionselementen die Beleuchtungsreihenfolge mit zunächst einer roten und nach der Hälfte der Dauer der Bildaufnahme blauen Beleuchtung, bei b) die Helligkeit, die ein monochromer Detektor während der Bildaufnahme detektiert, und bei c) in einem Diagramm die während der Dauer der Bildaufnahme aufgenommene Helligkeit B entlang der Bewegungsrichtung x, wobei bei dieser Darstellung noch keine Relativbewegung zwischen dem Objekt und dem Detektor stattgefunden hat,
• 3 in drei schematischen Darstellungen in den Teilen a), b) und c) dieselbe Situation wie in 2, jedoch bei einer erfolgten Relativbewegung während der Dauer der Bildaufnahme, wobei sich das Objekt nach rechts, d.h. in positiver x-Richtung bewegt hat,
• 4 in einem Diagramm einen typischen Helligkeitsverlauf bei Betrachtung eines Detektionselements gemäß 3,
• 5 in einer schematischen Darstellung vier Situationen jeweils in Bereichen I., II., III. und IV., wobei die Darstellungen gemäß den Teilen a), b) und c) den Darstellungen in den 2 und 3 entsprechen und wobei jeweils Relativbewegungen nach links oder nach rechts bei zunächst roter und nach der Hälfte der Aufnahmedauer blauer Beleuchtung in den Bereichen I. und II. und zunächst blauer Beleuchtung und dann nach der Hälfte der Aufnahmedauer roter Beleuchtung in den Bereichen III. und IV. gezeigt sind, und
• 6 in einer schematischen Darstellung die beiden Situationen gemäß den Bereichen III. und IV. aus 5, wobei Abschnitte konstanter Helligkeit und eine Spitze im Helligkeitsverlauf für die Bestimmung der Relativgeschwindigkeit spezifiziert sind.

There are now various possibilities for designing and developing the teaching of the present invention in an advantageous manner. For this purpose, on the one hand, reference is made to the subordinate claims and, on the other hand, to the following explanation of preferred exemplary embodiments of the method according to the invention based on the drawing. In connection with the explanation of the preferred exemplary embodiments with reference to the drawing, generally preferred configurations and developments of the teaching are also explained. Show in the drawing

• 1 in a schematic representation a viewing window of a detector used in an exemplary embodiment of the method according to the invention and the detector, two detection elements being visible in the viewing window,
• 2 in three superimposed schematic representations, at a) a downwardly plotted time sequence during an image recording, with the lighting sequence to the left of the detection elements with initially a red and after half the duration of the image recording blue lighting, with b) the brightness, which is a monochrome Detector detected during the image recording, and at c) in a diagram the brightness B recorded during the duration of the image recording along the direction of movement x, whereby in this representation no relative movement has yet taken place between the object and the detector,
• 3 in three schematic representations in parts a), b) and c) the same situation as in 2 , but if there was a relative movement during the duration of the image recording, with the object moving to the right, ie in the positive x-direction,
• 4th in a diagram a typical brightness curve when viewing a detection element according to FIG 3 ,
• 5 in a schematic representation four situations each in areas I., II., III. and IV., the representations according to parts a), b) and c) to the representations in 2 and 3 and with relative movements to the left or to the right with initially red and after half of the exposure time blue lighting in areas I. and II. and initially blue lighting and then after half the exposure time red lighting in areas III. and IV., and
• 6th in a schematic representation the two situations according to areas III. and IV. from 5 , where sections of constant brightness and a peak in the brightness curve are specified for determining the relative speed.

1 shows a detector in a schematic representation 1 to determine the relative speed between an object and the detector 1 , the object having two detection elements 2 and 3 having that to an area 4th of the object. The detection element 2 has a turquoise color and the detection element 3 an orange color. The area 4th is trained white. 1 shows the area 4th with the detection elements 2 and 3 in a viewing window 5 of the detector 1 , which is designed as a monochrome image recorder in the form of a CMOS sensor. The detection elements 2 and 3 as well as the area 4th have different colors from each other.

During one embodiment of the method according to the invention, the detection elements 2 , 3 during the possible relative movement and for a predefinable duration an image recording by the detector 1 by means of a lighting device in a specifiable sequence and specifiable respective lighting duration, alternating with light of different wavelengths 6th , 7th illuminated. In the embodiment shown here, the first wavelength corresponds 6th red light and the second wavelength 7th blue light. By choosing the color design or the design with regard to the provided reflectance spectra of the detection elements 2 and 3 as well as the area 4th and the choice of illumination light colors provides a situation whereupon the first detection element 2 due to its turquoise color it appears light under blue lighting and dark under red lighting. With the orange color of the second detection element 3 if the situation is exactly the opposite, according to which this orange detection element 3 appears dark with blue lighting and bright with red lighting.

In the 1 , 2 , 3 and 5 corresponds to the dotted representation of the first detection element 2 a turquoise color and the representation of the second detection element 3 with cross lines of an orange color. The red light of the first wavelength 6th is represented by lines sloping down to the right and the blue light of the second wavelength 7th represented by lines running diagonally to the top right.

2 shows in a schematic representation how the brightness values are determined. A situation is shown in which there is no relative movement between the object and the detector. This includes the case of a relative speed with the value zero. At a) the time sequence or the time t is plotted downwards during an image recording. Between the arrow of the time sequence and the detection elements 2 and 3 is schematically the illumination color with initially the first wavelength 6th - red light - and then the second wavelength 7th - blue light - shown. To the right is a horizontal section plane through the detection elements 2 and 3 plotted, which moves downwards, ie along the t-axis, with time t. The color change or wavelength change takes place after half the duration of the duration Δt of the image recording. In the middle part b) the 2 the brightness that a monochrome image recorder such as the detector is plotted 1 detects, whereby the black area corresponds to the dark perception and the white area with the edge delimitation by a black line corresponds to the light perception by the detector. It can be seen that the detection element is during the first half of the exposure time 2 appears dark and light during the second half of the exposure time. With the detection element 3 the opposite is true. It appears light at first and then dark. The detector integrates the illuminance during the exposure time or the duration of the image recording, so that the brightness recorded by the detector as in the lower part c) of 2 can be determined, the mean value being calculated along the t-axis for each point on the x-axis, which shows the spatial extent along a possible direction of movement.

That means with the detection element 2 in the left area first 0% brightness and then 100% brightness, which results in an average value of 50% brightness, ie (0% + 100% / 2 = 50%. The average value is the same as for the detection element 3 a value of 50%. According to the diagram in c), this results in a brightness curve of the brightness B from a maximum value, that of the brightness of the white area 4th corresponds to a one section 10 or a distance of 50% constant which is initially transmitted to the detection element 2 and then the detection element 3 corresponds. The brightness curve then rises again to the maximum value, that of the brightness of the area 4th corresponds. The detection elements behave according to b) 2 and 3 so just in opposite directions, after which the first detection element first 2 dark and the second detection element 3 bright and then the first detection element 2 bright and the second detection element 3 be detected dark. The entire course of brightness during the duration of the image recording and the once changing different colored lighting is shown in the diagram at c).

• Die Erkennung der Detektionselemente 2 und 3 durch den Detektor 1 hängt von deren farblicher Gestaltung oder deren Remissionsspektren und von der jeweiligen Beleuchtungswellenlänge ab. In der Realität wird man möglicherweise keine extrem schmalbandigen Beleuchtungen mit nur einer Wellenlänge oder wenigen Wellenlängen zur Verfügung haben. In gleicher Weise wird das von den Detektionselementen 2 und 3 reflektierte Licht nicht nur aus einer Wellenlänge oder einigen wenigen Wellenlängen bestehen. Insoweit sind die Charakterisierungen „dunkel“ und „hell“ ebenfalls relativ zu sehen und eine Unterscheidung dieser beiden Zustände als „dunkel“ oder „hell“ wird vom Auflösungsvermögen des gewählten Detektors abhängen. Grundsätzlich muss ein Remissionsspektrum eines Detektionselements ein Beleuchtungsspektrum der Beleuchtungseinrichtung zumindest teilweise umfassen, um zu einer Wahrnehmung als „hell“ zu führen. Die Farbe des Detektionselements und die Farbe des Beleuchtungslichts müssen in entsprechender Weise ähnlich und aufeinander abgestimmt sein. In umgekehrter Weise soll ein Remissionsspektrum eines Detektionselements ein Beleuchtungsspektrum der Beleuchtungseinrichtung möglichst wenig umfassen, um zu einer Wahrnehmung durch den Detektor als „dunkel“ zu führen. Insoweit führt gemäß dem erläuterten Ausführungsbeispiel eine blaue Beleuchtung einer türkisen Farbe zu einer hellen und eine blaue Beleuchtung einer orangenen Farbe zu einer dunklen Wahrnehmung. Im Ergebnis sind die Farben und jeweiligen Remissionsspektren der Detektionselemente 2 und 3 sowie des Bereichs 4 in geeigneter Weise auf die Wellenlängen 6 und 7 oder auf entsprechende Wellenlängenspektren der abwechselnden Beleuchtung abzustimmen.

To the detection as "dark" and "light" by the detector 1 the following is also carried out:

• The recognition of the detection elements 2 and 3 through the detector 1 depends on their color design or their reflectance spectra and on the respective illumination wavelength. In reality, it is possible that extremely narrow-band lighting with only one wavelength or a few wavelengths will not be available. This is done in the same way by the detection elements 2 and 3 reflected light does not consist of just one wavelength or a few wavelengths. In this respect, the characterizations “dark” and “light” can also be seen relatively and a distinction between these two states as “dark” or “light” will depend on the resolution of the selected detector. In principle, a reflectance spectrum of a detection element must at least partially include an illumination spectrum of the illumination device in order to lead to a perception as “bright”. The color of the detection element and the color of the illuminating light must be similar and matched to one another in a corresponding manner. Conversely, a reflectance spectrum of a detection element should be a lighting spectrum of the lighting device include as little as possible in order to lead to a perception by the detector as “dark”. In this respect, according to the exemplary embodiment explained, a blue illumination of a turquoise color leads to a light perception and a blue illumination of an orange color to a dark perception. The result is the colors and the respective remission spectra of the detection elements 2 and 3 as well as the area 4th appropriately to the wavelengths 6th and 7th or to match them to appropriate wavelength spectra of the alternating lighting.

3 shows in three schematic representations a), b) and c) a situation with a relative movement between object and detector 1 for the duration of an image recording. A relative movement takes place along the x-axis to the right in the positive x-direction. The representations in parts a), b) and c) of 3 correspond to the illustrations in parts a), b) and c) of 2 . In part a), the object moving to the right can be recognized by the trapezoidal shape of the detection elements 2 and 3 have formed.

In part b) the 3 are the corresponding intensities of the brightnesses perceived by the detection elements 2 and 3 shown, a shift to the right during time t can also be seen here.

In area c) the brightness B is now plotted along the x-direction. At each point on the x-axis there is an integration of the brightnesses recorded during the duration of an image recording by the detector 1 their precipitation. Compared to the brightness curve in 2 c) there is a kind of broadening of the brightness curve with a falling edge 8th that is based on the maximum value of the brightness, that of the brightness of the area 4th corresponds. Then there is a further section in the positive x-direction 10 or a constant 50% value for a distance and a rising edge in the further course 9 , up to the maximum value of the brightness B. . The gradient pattern is then repeated with a falling edge 8th , one more section 10 or a constant 50% range for a distance and a rising edge 9 up to the maximum value of the brightness, which is again the brightness of the area 4th corresponds. Between the two constant, plateau-like sections 10 with the 50% value is through the rising edge 9 and the subsequent falling edge 8th a peak 11 or a peak section is formed which extends in the direction of increasing brightness B. extends.

4th shows in a diagram the brightness curve with respect to a detection element 2 or 3 according to 3 c) in an isolated illustration. The brightness curve generated during the relative movement is shown here as a function of the location. The brightness B. according to the in 4th The curve shown in the x-direction initially shows its maximum value. This corresponds to the brightness value of the area 4th . Looking further at the curve in the direction of movement along the x-axis, the brightness value increases in the area of the brightness profile along a width d and in the form of a flank 8th or linear ramp down to a minimum of the brightness value. This minimum corresponds to the one section 10 or a distance of 50% constant according to 3 c) . After passing through the constant minimum in the positive x-direction, the brightness increases along a further edge 9 to the maximum value, which is the brightness value of the area 4th corresponds. The width of this further flank 9 corresponds to the width of the first falling edge 8th the curve and thus the distance covered during the relative movement d. The determination of the relative speed v can thus be calculated using the formula v = d / Δt, where Δt is the duration of the image recording by the detector 1 is. A determination of the speed can be made both at the in the 3 and 4th shown left flanks or falling flanks 8th as well as right flanks or rising flanks 9 done as both the falling edges 8th as well as the rising flanks 9 have the same width d.

5 shows in schematic representations in the areas I., II., III. and IV. various scenarios with regard to the direction of movement and the lighting sequence. Otherwise the representations shown there correspond to the basic structure 2 and 3 with parts a), b) and c). In particular, the scenario in area II. Corresponds to the scenario 3 . It can be clearly seen that a movement to the left, ie in the negative x-direction, leads to a different brightness curve than a movement to the right in the positive x-direction. However, a reversal of the lighting order with regard to the first wavelength leads 6th and the second wavelength 7th again to a brightness curve that corresponds to the other direction of movement. In other words, the brightness curve in area I. corresponds to the brightness curve in area IV. And the brightness curve in area II. Corresponds to the brightness curve in area III. Either the direction of movement or the lighting sequence is reversed.

With knowledge of the lighting sequence and knowledge of the color design or reflectance spectra of the detection elements 2 and 3 and the area 4th can thus not only be a determination of Speed, but also a determination of the direction of movement, for which purpose a comparison with known expected spectra can be made by means of an evaluation device.

6th shows in schematic representations the two situations according to areas III. and IV. from 5 , with sections 10 with a constant brightness curve in the x-direction, ie plateaus with constant brightness in the brightness curves according to parts c), and peaks 11 are highlighted in the brightness gradients. Since in some cases the spatial width d of the falling flanks 8th or rising edges 9 Because of the blurriness in digital image processing due to noise and the presence of only a few pixels, it is often difficult to determine, a distance between two constant sections can alternatively or additionally be used to determine the speed 10 and / or a distance D from centers M. two constant sections 10 and / or a width Q of a tip 11 between two constant sections 10 be used. In 6th in addition to these parameters already mentioned, a length L of a detection element 2 or 3 and a length P of a constant section 10 specified.

$$\text{D}=\text{P}+2*\text{d}$$

$$\text{D}=\left(\text{L}-\text{d}\right)+\left(2*\text{d}\right)$$

$$\text{D}=\text{L}+\text{d}$$

$$\text{D}=\text{L}+\text{v*}\mathrm{\Delta }\text{t}$$

Becomes the focus M. of the two sections 10 according to area III. determined, both sections 10 each have a length P, the distance D of the center points M. can be calculated as follows: $$\text{D.}=\text{P}/2+\text{d}+\text{d}+\text{P}/2$$

$$\text{D.}=\text{P}+2*\text{d}$$

$$\text{D.}=\left(\text{L.}-\text{d}\right)+\left(2*\text{d}\right)$$

$$\text{D.}=\text{L.}+\text{d}$$

$$\text{D.}=\text{L.}+\text{v *}\mathrm{\Delta }\text{t}$$

It can be seen from this that the distance between the two sections 10 or the distance D between the centers M. of sections 10 is linearly dependent on the speed.

$$\text{Q}=2*\text{v}*\mathrm{\Delta }\text{t}$$

Alternatively or in addition to this, the width Q of the tip can also be used 11 can be determined in the middle of the brightness curve as follows: $$\text{Q}=2*\text{d}$$

$$\text{Q}=2*\text{v}*\mathrm{\Delta }\text{t}$$

The advantage of taking into account the width Q of the tip 11 is that the certain width Q with respect to the speed with a factor 2 increases and thus an improved measurement accuracy in comparison with the consideration of the distance between the sections 10 or the distance D between the centers M. of sections 10 results.

$$\text{D}=\text{P}+2*\text{d}$$

$$\text{D}=\left(\text{L- 2*d}\right)+2*\text{d}$$

$$\text{D}=\text{L}$$

In the area IV. The distance between the sections 10 or the distance from centers of the sections 10 cannot be used because: $$\text{D.}=\text{P}/2+\text{d}+\text{d}+\text{P}/2$$

$$\text{D.}=\text{P}+2*\text{d}$$

$$\text{D.}=\left(\text{L- 2 * d}\right)+2*\text{d}$$

$$\text{D.}=\text{L.}$$

No proportionality to the relative speed can be derived from this.

$$\text{Q}=2*\text{v*}\mathrm{\Delta }\text{t}$$

However, in a situation according to area IV. The width Q of the tip 11 which are in the middle of the brightness curve between two constant sections 10 can be used again as follows: $$\text{Q}=2*\text{d}$$

$$\text{Q}=2*\text{v *}\mathrm{\Delta }\text{t}$$

According to area III. shows the top 11 towards increasing brightness B. , whereas in area IV. the top 11 towards decreasing brightness B. shows. Since according to area III. a movement to the left and in the area IV. a movement to the right is based, can be from the direction of the tip 11 the direction of the relative speed can be derived.

When carrying out an exemplary embodiment of the method according to the invention, a suitable, coordinated choice of the color design or design with regard to the reflectance spectra of the detection elements is necessary 2 and 3 and the area 4th as well as the wavelengths 6th and 7th or to undertake corresponding wavelength spectra of the illuminating light that illuminates alternately. With these parameters a scenario suitable for the respective application can be generated in order to carry out a more reliable determination of the relative speed - also v = 0 - between an object and a detector. In addition to the colors mentioned above by way of example, any other colors are also such Green shades can be used, provided there is sufficient contrast between light and dark perception by the detector 1 with appropriate lighting with the different wavelengths 6th and 7th or wavelength spectra is guaranteed. In addition to these parameters, the sequence of lighting and the respective duration of the different lighting can be specified to verify the functionality of a device used. The point in time of the start of an image recording can also be used as an additional or alternative parameter in order to establish a scenario for a suitable image recording, which can then be used to reliably verify the functionality of a detector, for example.

In any case, if the lighting sequence and order of the colors or reflectance spectra of the detection elements are known 2 and 3 of the object, the direction of the relative movement can be determined on the basis of the brightness profile or intensity profile. The speed can be determined from an edge steepness in this brightness profile or intensity profile.

Depending on the detector used, for example a pixel sensor, the in the 2 to 6th The brightness curves shown may be composed of individual pixels or pixel values. A continuous curve can be obtained with a suitable compensation calculation.

In the exemplary embodiments shown here, the optical axis is the detector 1 arranged perpendicular to the plane within which the detection elements 2 and 3 or move the object. In further exemplary embodiments, the optical axis of the detector must 1 not necessarily perpendicular to the plane of movement of the detection elements 2 and 3 or of the object. It is also an inclined orientation of the optical axis of the detector 1 relative to the plane of movement of the detection elements 2 and 3 or the object possible. The inclination of the optical axis relative to the plane of movement of the detection elements 2 and 3 or the object must be taken into account when determining the relative speed.

However, the determination of the relative speed does not work or does not work very reliably if the optical axis of the detector 1 runs parallel to or coincides with the direction of movement or within one to the plane of movement of the detection elements 2 and 3 or the object is arranged or extends parallel plane.

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

Finally, it should be expressly pointed out that the exemplary embodiments described above only serve to explain the teaching claimed, but do not restrict them to these exemplary embodiments.

List of reference symbols

1

detector

2

first detection element

3

second detection element

4th

Area

5

Viewing window

6th

first wavelength

7th

second wavelength

8th

falling edge

9

rising edge

10

constant section

11

top

d

width

Δt

Duration of an image recording

t

time

x

place

B.

brightness

D.

distance

L.

Length of a detection element

M.

Focus

P

Length of the constant section

Q

Width of the tip

QUOTES INCLUDED IN THE DESCRIPTION

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

Patent literature cited

• EP 0532169 A1 [0003]
• EP 1729086 A1 [0004]

Claims (11)

Method for determining the 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 two detection elements (2, 3) which have a reflectance spectrum that is different relative to a predeterminable area (4) of the object and different from one another, with at least one of the detection elements (2, 3) adjoining the area (4), wherein the detection elements (2, 3) are alternately illuminated with light of different wavelengths (6, 7) during the possible relative movement and for a specifiable duration (Δt) of an image recording by the detector (1) by means of an illumination device in a specifiable sequence and specifiable respective illumination duration , wherein the wavelengths (6, 7) are chosen such that at least one first detection element (2) of the detector (1) is dark when illuminated with at least one first wavelength (6) and dark when illuminated with at least one of the at least one first Wavelength (6) different second wavelength (7) light, at least one further second detection element (3) when illuminated with the at least one second wavelength (7) dark and when illuminated with the at least one first wavelength (6) light and the area (4) dark or light with a correspondingly low or high brightness (B) are detected both with illumination with the at least one first wavelength (6) and with illumination with the at least one second wavelength (7), whereby in the image recording generated by this, a brightness curve dependent on the remission spectra of the area (4) and the detection elements (2, 3) and on the different wavelengths (6, 7) of the illuminations with decreasing and / or increasing brightnesses (B) in the possible Direction of movement is detected by the detector (1), and wherein the relative speed is determined and / or based on a proportionality of a spatial width (d) of a decreasing or increasing section of the brightness curve to the relative speed and taking into account one or more of the illumination periods wherein based on a proportionality of a distance between two constant sections (10) and / or a distance (D) from centers (M) of two constant sections (10) and / or a width (Q) of a tip (11) between two constant sections ( 10) of the brightness curve in relation to the relative speed and the relative speed is determined taking into account one or more of the illumination periods. Procedure according to Claim 1 , characterized in that a monochrome camera, preferably a camera with a pixel sensor, is used as the detector (1), the pixel sensor further preferably being designed as a CMOS sensor or CCD sensor or as a line sensor. Procedure according to Claim 1 or 2 , characterized in that the detection elements (2, 3) are arranged adjacent to one another on, on or in the object. Method according to one of the Claims 1 to 3 , characterized in that the detection elements (2, 3) are arranged adjacent to one another in the direction of movement. Method according to one of the Claims 1 to 4th , characterized in that the detection elements (2, 3) have a rectangular contour, the detection elements (2, 3) preferably being elements of a code, in particular a data matrix code or a bar code. Method according to one of the Claims 1 to 4th , characterized in that the detection elements are implemented as linear detection elements extending in the direction of movement. Method according to one of the Claims 1 to 6th , characterized in that the area (4) is implemented as a light or white or as a dark or black area (4) or background and / or that the area (4) has a high or low level of remission for at least one specifiable spectral range and / or for at least one wavelength. Method according to one of the Claims 1 to 7th , characterized in that after half a duration (Δt) of the image recording, the wavelength of the illumination is changed from the at least one first wavelength (6) to the at least one second wavelength (7). Method according to one of the Claims 1 to 8th , characterized in that the duration (Δt) of the image recording is specified in such a way that the object or the detection elements (2, 3) do not move or move out of a viewing window (5) of the detector during the duration (Δt) of the image recording. Method according to one of the Claims 1 to 9 , characterized in that taking into account the shape of the brightness curve and the sequence of the wavelengths (6, 7) of the lighting, the direction of movement is determined. Device for carrying out a method for determining the relative speed between an object and a detector (1), preferably for carrying out a method according to one of the Claims 1 to 10 , wherein a relative movement between the object and the detector (1) can take place in one direction of movement, the object having at least two detection elements (2, 3) which have a different remission spectrum relative to a predeterminable area (4) of the object and different from one another , wherein at least one of the detection elements (2, 3) adjoins the area (4), the detection elements (2, 3) during the possible relative movement and during a predeterminable duration (Δt) of an image recording by the detector (1) by means of an illumination device can be illuminated alternately with light of different wavelengths (6, 7) in a predeterminable sequence and illumination duration, the wavelengths (6, 7) being selected such that at least one first detection element (2) of the detector (1) when illuminated with at least one first wavelength (6) dark and when illuminated with at least one of the at least one first n wavelength (6) different second wavelength (7) light, at least one further second detection element (3) when illuminated with the at least one second wavelength (7) dark and when illuminated with the at least one first wavelength (6) light and the Area (4) can be detected both with illumination with the at least one first wavelength (6) and with illumination with the at least one second wavelength (7) dark or light with correspondingly low or high brightness (B), in which case generated image recording a brightness curve dependent on the remission spectra of the area (4) and the detection elements (2, 3) and the different wavelengths (6, 7) of the illuminations with decreasing and / or increasing brightnesses (B) in the possible direction of movement of the detector (1) is detectable, and based on a proportionality of a spatial width (d) of a decreasing or increasing end section of the brightness curve to the relative speed and taking into account one or more of the illumination periods the relative speed can be determined and / or based on a proportionality of a distance between two constant sections (10) and / or a distance (D) from centers (M) of two constant ones Sections (10) and / or a width (Q) of a tip (11) between two constant sections (10) of the brightness curve relative to the relative speed and taking into account one or more of the illumination periods, the relative speed can be determined.

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