METHOD FOR DETERMINING AN ABSOLUTE COORDINATE FOR A TARGET WELL OF A MULTIWELL PLATE AND AN ADDRESSING DEVICE

Description

[0001] The invention relates to a method for determining an absolute coordinate for a target well of a multiwell plate and to an addressing device.

[0002] Pipetting involves adding or removing small amounts of liquid, such as media, chemicals, or biological samples, from multiwell plates—sometimes also called microtiter plates. This process is usually performed using hand-held dosing pipettes, whose volume typically ranges from 1 µl to 1 ml. Multiwell plates usually have 96, 384, or 1536 wells, into which individual pipettes can be placed independently. Manual pipetting with a dosing pipette is a process that requires the utmost precision, which is why it is usually performed only by trained personnel. Documentation of the pipetting process must be done manually, either in a lab notebook or entered into appropriate laboratory software.Without additional methods, such as sample staining, the responsibility for ensuring that individual pipetting steps are performed correctly rests solely with the user and / or operator of the dosing pipette. This risk of error is particularly high when working in confined spaces, as there is no overarching control when performing very similar pipetting steps and, for example, a colleague interrupts the workflow. Therefore, even with a high level of concentration, a user is at risk of error if their work is interrupted.

[0003] Currently, automation using automated pipetting systems requires a very high degree of preparation and calibration to control the position of the multiwell plates. While detecting the actual position of a dosing pipette tip relative to a multiwell plate enables a flexible system for faster automation of pipetting tasks, the corresponding automated pipetting systems involve a significant investment.

[0004] European patent EP 3 154 698 B1 discloses a pipette comprising a cylinder with a piston, which is movably mounted within the cylinder for drawing in and dispensing liquids, and a handle for gripping the pipette. The pipette further includes an imaging device element for obtaining images to aid its use. However, the problem remains that the pipette and the associated device are complex in design and correspondingly expensive to purchase. Furthermore, the use of the device requires the arrangement of multiwell plates on a specially designed surface.

[0005] WO 2018 / 088460 A1 discloses a system for detecting well addresses of a multiwell plate. EP 3 154 698 A1 discloses a pipette that includes an imaging element for obtaining images. WO 2015 / 172971 A1 discloses a method for detecting the presence or absence of disposable pipette tips in pipette tip holders.

[0006] There is therefore a need to provide a dosing pipette, or a method and device for a dosing pipette, that allows for the simple tracking of pipetting processes. It would also be advantageous if this device were easy to use and cost-effective. Furthermore, it would be beneficial if commercially available, manually operated dosing pipettes could also be retrofitted with the device.

[0007] The invention is therefore based on the objective of creating a method for determining an absolute coordinate for a target well of a multiwell plate and an addressing device, wherein the aforementioned disadvantages are at least reduced, preferably do not occur.

[0008] The problem is solved by providing the present technical teaching, in particular the teaching of the independent claims as well as the preferred embodiments and exemplary embodiments disclosed in the dependent claims and the description.

[0009] The problem is solved in particular by providing a method for determining an absolute coordinate for a target well of a multiwell plate for carrying out a pipetting operation into the target well using a dosing pipette, wherein the target well is the well of the multiwell plate which, at the time of the pipetting operation carried out with the dosing pipette, is closest to a dosing pipette tip, wherein an optical sensor for recording, in particular detecting, an image stream representing the dosing pipette tip is arranged on the dosing pipette, in such a way that an environment of the dosing pipette tip, including the dosing pipette tip, is imaged in the image stream, wherein the image stream is evaluated to determine an image of a region of the multiwell plate in the image stream, and wherein the following method steps are carried out,when the image stream detects an area of ​​the multiwell plate: , a) Detecting at least three, preferably eight, wells of the multiwell plate in the imaged area of ​​the multiwell plate, particularly in a single frame of the image stream; b) Creating a model of the multiwell plate based on the wells detected in step a) and determining the absolute coordinate of the target well based on the model, wherein the model of the multiwell plate is created by: b1) applying a wave grid to the detected wells, preferably based on a predetermined or specifiable distance feature and preferably extending it beyond the detected wells, from which the model is obtained, wherein a relative wave grid of the model of the multiwell plate is used as the wave grid.wherein the relative 2D coordinates of the wells identified according to step a) are determined using the relative coordinates of adjacent regular features to determine the relative well grid, and / or b2) the identified wells are compared with a plurality of layouts of known and / or predefinable multiwell plates, wherein the layout of the plurality of layouts which shows the highest agreement with the identified wells is selected as the selected layout, wherein the model is obtained from the selected layout.

[0010] In connection with the present invention, an image stream shall be understood to be a stream of individual images from an optical sensor, in particular a camera, wherein the image stream preferably has a frame rate of 24 Hz. However, in connection with the present invention, the term image stream can also refer to the individual images or groups of images within the image stream of the optical sensor, in particular the camera.

[0011] In a preferred embodiment, it is possible that after process step a) in a process step a1), a subset, preferably at least three, of the identified wells according to process step a) are selected, which are then used as identified and selected wells in the further process steps, in particular in process step b), in particular in process steps b1) and b2), instead of the identified wells.

[0012] A distance feature, in this context, refers specifically to a feature that characterizes or determines the distance between immediately adjacent wells. Specifically, the distance feature can be the distance between immediately adjacent wells. It can also be the smallest detected well spacing and / or the most frequently detected well spacing. If wells are detected in an image of the image stream, distances between the centers of the wells can be determined. A multitude of different distances are detected, for example, distances between wells that are immediately adjacent in different directions, but also distances between wells that are not immediately adjacent, with other wells positioned in between.The smallest detected distance can be understood as the characteristic distance between wells immediately adjacent to one another along a base direction of the multiwell plate – in particular along a row or column. It is also to be expected that such a distance between wells immediately adjacent to one another along a base direction will be detected most frequently, so that the most frequently detected distance can also be used as the characteristic distance. Thus, in a preferred embodiment, the distance feature is such a characteristic distance.

[0013] A lattice feature is understood to be, in particular, a feature that is characteristic or determining for a lattice and that characterizes the position of the wells on the multiwell plate. In a preferred embodiment, such a lattice feature is a basis vector, or a pair of non-collinear, preferably orthogonal, basis vectors of the lattice. Preferably, the basis vectors are obtained from the spacing feature, in particular as characteristic distances between wells that are immediately adjacent to one another along the bass directions spanning the lattice.

[0014] In this context, the term "layout" of a multiwell plate refers specifically to the design of the multiwell plate, particularly its size, shape, and the number of rows and columns of wells arranged on the plate. A number of such layouts of known multiwell plates may be stored in a database, and these layouts can be accessed to carry out the method proposed here.

[0015] The method for determining an absolute coordinate for a target well of a multiwell plate can be provided in particular within the framework of higher-level procedures, especially process complexes, such as the logging of a pipetting task, the creation and / or processing of a recipe which contains a predetermined sequence of different pipetting tasks.

[0016] In particular, it is preferably provided that the target wells approached or targeted with the dosing pipette tip, i.e., in particular those wells towards which the dosing pipette tip points for at least a parameterizable period of time, are recorded.

[0017] Furthermore, it is preferably provided that, within the framework of a higher-level procedure, a pipetting process can also preferably be blocked if an incorrect well is detected with the present procedure, into which an attempt is accidentally made to pipette.

[0018] Conversely, it is also possible for a higher-level process to release a pipetting operation when the dosing pipette tip is positioned over a target well that has been identified as the correct well using the existing method. This makes it possible to perform pipetting tasks in a simple and, above all, reproducible manner. Furthermore, the often monotonous and very tiring pipetting work becomes traceable afterward, so that if errors occurred, their cause can be determined retrospectively. Forensic investigations, in particular, where errors are unacceptable, especially if the results of such investigations form the basis of, for example, criminal judgments, can be precisely documented and subsequently reviewed and / or verified for accuracy using the method proposed here.

[0019] In this context, it is preferably provided that the image stream captured by the optical sensor or the individual images from the image stream are also stored - for documentation purposes - in addition to the storage of the detected well.

[0020] Furthermore, it is possible that, by means of a suitable device, such as a vibration exciter assigned to the dosing pipette, a user of the dosing pipette is guided to a target well that has been predetermined, in such a way that, for example, the vibration frequency and / or amplitude is reduced, in particular to zero, when the dosing pipette has been placed over the correct well.

[0021] Furthermore, it is preferably provided that the multiwell plates used in the process do not have any special features by which a well can be automatically detected and / or identified. This refers in particular to barcodes or other markings that help to detect and / or identify a multiwell plate, especially a well on the multiwell plate.

[0022] Furthermore, it is preferably intended that the dosing pipette be a hand-held pipette. In other words, it is specifically intended that it is not a machine-operated dosing pipette.

[0023] Alternatively or additionally, it is preferably provided that the method according to the invention is also used in a pipetting machine, in particular a pipetting robot, with in particular axis-guided dosing pipettes.

[0024] The method according to the invention is particularly preferred for the automatic documentation of pipetting operations. In this context, the method can be used to identify the targeted wells during a software recording mode. Specifically, information about the steps performed with the dosing pipette is continuously recorded during the process. If well identification is not possible during aspiration or dispensing, an entry with empty coordinates is made. Such documentation can be interrupted or terminated via software or by an additional signal, in particular a button and / or actuator and / or trigger. The recorded data is stored, preferably on the evaluation device.

[0025] Furthermore, a procedure is conceivable that enables automatic (early) error detection and active warnings for near misses. In such an operating mode, the dosing pipette can compare a stored protocol for a sequence of pipettes with the pipettes performed by the user, so that the user is shown precisely which steps to perform next. Deviations from the protocol can be detected, and a warning message can be issued, preferably audibly and / or visually, via an output device associated with the evaluation unit. The user is then prompted to correct the deviation from the protocol and can continue with the procedure. The recorded data is stored.In addition, it is possible to continuously evaluate which well the pipette tip is located in, so that an early warning can be given before an incorrect pipetting is carried out, if necessary by means of the vibration exciter mentioned above.

[0026] Furthermore, an operating mode is conceivable in which aspiration or dispensing with the dosing pipette can only be performed after successful detection and verification that the correct target well is being used. If the correct target well is not detected, the dosing pipette or the addressing device could be designed in such a way that pipetting, i.e., aspiration or dispensing, is not possible, i.e., it is blocked. Additionally, it is conceivable that, in a pipetting robot, an identifier for the wells is determined and stored independently of any other control system. This allows for verification, independent of the pipetting robot, of whether error-free operation is occurring, i.e., whether the correct wells have been processed.Furthermore, corresponding calibration, verification, or plausibility functions are conceivable.

[0027] According to a further development of the invention, the image stream from the optical sensor, in particular the camera, is preprocessed using Gaussian blurring, thereby reducing image noise. This makes it possible, in particular, to obtain a more suitable image stream for evaluation in a simple manner and using a common and proven algorithm.

[0028] Alternatively or additionally, it is possible to brighten the image stream, in particular individual images of the image stream or the entire image stream, preferably by an offset and / or scaling operation.

[0029] According to a further development of the invention, edge detection is performed to identify regular features in order to detect the wells of the multiwell plate according to process step a). Preferably, the parameters of the edge detection are determined based on a median of the gray values ​​of the acquired image stream, in particular the area of ​​the multiwell plate within the image stream. Preferably, the edge detection is performed using a Canny algorithm, and subsequently, preferably, the edges are enhanced—sometimes also referred to as dilation. By means of edge detection, and preferably with parameters for edge detection based on a median of the gray values ​​of the acquired image stream, improved and more robust detection of regular features can be achieved in a simple manner.

[0030] According to a further development of the invention, a Hough transform is performed to detect the wells of the multiwell plate according to process step a), preferably for identifying circular features, in particular for detecting circular wells. The use of the Hough transform has proven especially advantageous for detecting circular wells in the image stream.

[0031] According to a further development of the invention, in process step b1), when determining the model of the multiwell plate, detection of multiwell plate edges in a multiwell plate edge region of the multiwell plate in the image stream is performed, wherein the multiwell plate edge region lies in a predefinable area or at a predefinable multiwell plate edge distance to the outermost wells of the model of the multiwell plate. Preferably, the multiwell plate edge distance corresponds to the smallest and / or most frequently detected well spacing between the wells detected according to process step a), or to a well spacing between wells of a layout of the majority of the layouts according to process step b2).In particular, applying the smallest wave spacing with the highest frequency, or the wave spacing between wells of a layout out of the majority of layouts, provides a simple feature or criterion for defining, based on the previously detected wells, an area where edges of the multiwell plate are to be expected. This leads to a significant improvement in detection quality as well as a considerably more efficient utilization of the available computing power. In other words, the method is made significantly more computationally efficient.

[0032] According to a further development of the invention, in step b1) the relative 2D coordinates required for determining the relative wave lattice are determined, preferably by recursive determination using the relative coordinates of the neighboring regular features – particularly known ones – especially neighboring wells of the target well. By orienting the process to neighboring regular features, such as neighboring wells, the efficiency of the method is significantly increased, and errors can also be avoided.

[0033] According to a further development of the invention, it is provided that in step b2) when determining a relative wave grid of the model of the multiwell plate, in particular of the selected layout of the plurality of layouts, a multiwell plate edge region of the multiwell plate is obtained by shifting the multiwell plate edge region outwards with respect to the multiwell plate by an associated basis vector starting from straight rows of outer wells, which are based either on detected wells according to method step a) and / or on wells obtained by extending the model, wherein an actual edge of the multiwell plate is obtained by checking, in particular, whether an edge can actually be detected in the image stream of the optical sensor in the multiwell plate edge region.and wherein the associated basis vector is preferably based on the smallest and / or most frequently detected wave spacing between the wells detected according to process step a) or on the wave spacing of a selected layout of the majority of the layouts according to process step b2). By detecting edges, in particular the edges of the multiwell plate, verification and / or plausibility of the results obtained by the method can also be achieved in a simple manner.

[0034] The problem is also solved in particular by providing an addressing device for a dosing pipette, especially a hand-held one, with a dosing pipette tip, comprising a base body with a - preferably two-part - dosing pipette receiving device, which is configured to be connected to a dosing pipette in an operating position, wherein the base body has a communication device and an optical sensor, wherein the communication device is operatively connected to the optical sensor, wherein a focus and / or a field of view of the optical sensor is focused and / or directed on the tip, in particular the pipette tip, of the dosing pipette in the operating position, wherein the addressing device has an - preferably automatic, in particular programmed - evaluation device, which is operatively connected to the communication device, wherein the evaluation device is configured topreferably autonomously and / or automatically, that is to say, in particular without triggering by a user, to carry out a method according to the invention or a method according to one of the aforementioned embodiments. In connection with the addressing device, the advantages are realized in particular that which have already been explained in connection with the method for determining an absolute coordinate for a target well of a multiwell plate.

[0035] In the context of the present technical teaching, a device, in particular the addressing device, is understood to be a device or system which includes a plurality of further devices, in particular the base body, the metering pipette receiving device, the communication device, the optical sensor and, according to the invention, the evaluation device.

[0036] The method is particularly preferably carried out on the evaluation device, which is preferably designed as a PC and is preferably independent of the base body. Alternatively, it is preferably provided that the evaluation device is associated with the base body or is designed as a communication device. This means, in particular, that the communication device can also take over the function of the evaluation device. In other words, the communication device is additionally configured to carry out the method for determining an absolute coordinate for a target well of a multiwell plate.

[0037] According to a further development of the invention, it is provided that the evaluation device is assigned to the base body, in particular arranged on the base body or integrated into the base body.

[0038] The optical sensor is preferably selected from a group consisting of a camera, in particular an optical camera, a thermal imaging camera, and a NIR camera (near-infrared camera).

[0039] The invention will be explained in more detail below with reference to the drawing.

[0040] This shows: Figure 1 shows a schematic diagram of a flowchart of an embodiment of the method for determining an absolute coordinate for a target well of a multiwell plate; Figure 2 shows a schematic diagram of an embodiment of the addressing device, in particular a base body of the addressing device; Figure 3 shows a schematic diagram of a single frame of the image stream of the optical sensor; Figure 4 shows a schematic diagram of the single frame of the image stream of the optical sensor. Figure 3, where Wells were detected according to procedure step a), Figure 5 shows a schematic representation of the single frame of the image stream of the optical sensor according to Figure 3 or 4 , wherein a basis vector according to process step b), in particular process step b1), is shown, Figure 6 in a schematic representation the single frame of the image stream of the optical sensor according to Figure 3, 4 or 5 , wherein edge detection was performed in process step b1) or b2), Figure 7 shows a schematic representation of the single frame of the image stream of the optical sensor according to one of the Figures 3, 4, 5 and 6 , wherein according to procedure step b) an absolute coordinate of the target well was determined, Figure 8 in a schematic representation the single frame of the image stream of the optical sensor according to Figure 7 , showing that the method can also be carried out on a multiwell plate that is only partially imaged,

[0041] Fig. 1A schematic diagram shows a flowchart of an embodiment of the method for determining an absolute coordinate for a target well 1 of a multiwell plate 3 for carrying out a pipetting operation into the target well 1 using a metering pipette 5, wherein the target well 1 is the well of the multiwell plate 3 which is closest to a metering pipette tip 7 of the metering pipette 5, wherein an optical sensor (not shown in the figures) is arranged on the metering pipette 5 for recording an image stream 9 of the metering pipette tip 7, such that the metering pipette tip 7 is imaged in the image stream 9 (see in particular Fig. 3 ), wherein the image stream 9 is evaluated for an image of an area 11 of the multiwell plate 3 in the image stream, and wherein the following procedure steps are carried out when the image of an area 11 of the multiwell plate 3 is detected in the image stream 9: a) Detecting at least three, preferably eight, wells 13 of the multiwell plate 3 in the illustrated area 11 of the multiwell plate 3. This process step is particularly the Fig. 4 to be seen. For clarity, only two of the identified Wells 13 are shown in Figure 4 , but also in the Figures 5 to 8 , designated with a reference symbol.

[0042] Furthermore, the Figures 3 to 8 The area 11 of the multiwell plate 3 is shown and / or depicted in the image stream 9. The area 11 of the multiwell plate 3 is preferably arranged around a pipette tip 7 of the dosing pipette 5, but can also be located in another area of ​​the multiwell plate 3. Therefore, in the Figures 3 to 8 The area 11 of the multiwell plate 3 is shown, for example, arranged in the area of ​​the dosing pipette tip 7.

[0043] Fig. 2An addressing device 27 for a particularly hand-held dosing pipette 5 with a dosing pipette tip 7 is to be removed, comprising a base body 29 with a, preferably two-part, dosing pipette receiving device 31, which is configured to be in an operating position with a dosing pipette 5 (in Figure 2(not shown) to be connected, wherein the base body 29 has a communication device (not shown in the figures) and an optical sensor (not shown in the figures), wherein the communication device is operatively connected to the optical sensor, wherein a focus and / or a field of view of the optical sensor in the operating position is focused and / or directed onto the metering pipette tip 7 of the metering pipette 5, wherein the addressing device 27 is associated with an evaluation device (not shown in the figures) which is operatively connected to the communication device, wherein the evaluation device is configured to carry out a method according to the invention.

[0044] It is particularly preferred that the evaluation device is assigned to the base body 29.

[0045] Before the detection of at least three, preferably eight, wells 13 of the multiwell plate 3 can be carried out according to process step a), the operative connection between the communication device and the optical sensor as well as an operative connection between the evaluation device and the communication device is preferably established.

[0046] The image stream 9 is preferably recorded with specific camera parameters and is then transmitted from the optical sensor to the evaluation device via the aforementioned functional connections, either continuously or as a single image, preferably upon a trigger signal.

[0047] A trigger signal can be determined in particular by a sensor on the actuating button (not shown in the figures) of the dosing pipette, preferably with a pressure-elastic element.

[0048] In other words, a trigger signal is activated each time the dosing pipette's operating button is pressed. At this point, or at a predefined point in time, the image stream, or a single frame of the image stream, is stored, preferably on the evaluation device.

[0049] The Figure 1 Furthermore, according to step b), a model of the multiwell plate 3 is created based on the wells 13 identified in step a), and the absolute coordinate of the target well 1 is determined based on the model, whereby the model of the multiwell plate 3 is created by: b1) particularly starting from the detected wells 13 - preferably on the basis of a particularly predetermined or predefinable spacing feature using a particularly predetermined or predefinable grid feature - a wave grid 15 is applied to the detected wells 13 and preferably extended beyond the detected wells 13, from which the model is obtained, wherein a relative wave grid of the model of the multiwell plate 3 is used as the wave grid 15, wherein relative 2D coordinates of the wells 13 detected according to process step a) required to determine the relative wave grid are determined by means of relative coordinates of adjacent regular features, in particular neighboring wells of the target well, and / or b2) the detected wells 13 are compared with a plurality of layouts of known and / or predefinable multiwell plates, wherein the layout of the plurality of layouts is selected as the selected layout,which shows the highest agreement with the identified Wells 13, whereby the model is obtained from the selected layout.

[0050] The detected wells 13 of the multiwell plate 3 in area 11 of the multiwell plate 3 are preferably obtained as detected and selected by sorting all detected wells in the image stream 9 according to a pixel address, and then selecting all detected wells which belong to the pixel address interval of area 11 of the multiwell plate 3.

[0051] Furthermore, it is preferably provided that the image stream 9 of the optical sensor, in particular individual frames of the image stream, is preprocessed using a Gaussian blur filter, whereby noise reduction is particularly performed. According to a preferred embodiment, it is possible that the image stream 9, in particular individual frames of the image stream 9, is brightened, in particular by an offset and / or scaling operation.

[0052] Furthermore, it is preferably provided that, in order to detect the wells 13 of the multiwell plate 3 according to process step a), edge detection is carried out to detect regular features, wherein preferably a determination of parameters of the edge detection is based on a median of the gray values ​​of the captured image stream, in particular of the area 11 of the multiwell plate in the image stream 9, wherein preferably the edge detection is carried out with a Canny algorithm and subsequently preferably an enhancement of the edges - sometimes also referred to as dilation - is carried out.

[0053] Furthermore, it is preferably provided that a Hough transformation is carried out to detect the wells 13 of the multiwell plate 3 according to process step a), preferably for the identification of circular features, in particular for the detection of circular wells.

[0054] Furthermore, it is preferably provided that in process step b1) when determining the model of the multiwell plate 3, a detection of multiwell plate edges 17 in a multiwell plate edge area 19 of the multiwell plate 3 in the image stream 9 is carried out, wherein the multiwell plate edge area 19 lies in a predefinable area or in a predefinable multiwell plate edge distance to the outermost wells 21 of the model of the multiwell plate 3.

[0055] Furthermore, it is preferably provided that in step b1) the relative 2D coordinates of the wells 13 identified according to procedure step a) required for determining the relative well grid are determined by a recursive determination using the relative coordinates of the neighboring regular features, in particular neighboring wells of the target well.

[0056] Furthermore, it is preferably provided that in step b2) when determining a relative wave lattice of the model of the multiwell plate 3, in particular of the selected layout of the plurality of layouts, a multiwell plate edge region 19 of the multiwell plate 3 is obtained by shifting the multiwell plate edge region 19 outwards with respect to the multiwell plate 3 by an associated basis vector 23 starting from straight rows of outer wells 21, which are based either on detected wells according to method step a) and / or on wells obtained by extending the model, wherein an actual edge 25 of the multiwell plate 3 is obtained by checking, in particular, whether an edge 25 can actually be detected in the multiwell plate edge region 19 in the image stream 9 of the optical sensor.and wherein preferably the associated basis vector 23 is based on a smallest and / or most frequently detected wave spacing between the wells detected according to process step a) or on a wave spacing of a selected layout of the majority of the layouts according to process step b2).

[0057] When determining the basis vectors 23 that span the wave lattice 15, a wave spacing of the identified wells 13 is first determined. Then, normalized vectors are formed between the centers of the circles of the identified wells. These vectors are then preferably aligned in principal directions, in particular from left to right and / or from top to bottom – inverting them if necessary. The normalized vectors are then preferably sorted according to the magnitude of the determined wave spacings. Angles between all vectors, in particular pairs of vectors, are calculated, and collinear vectors (x, y) are sorted into an array with x > y and another with y > x. Finally, an average of the direction and / or length of the vectors in the arrays is preferably calculated.The aforementioned array vectors are validated against each other as basis vectors by comparing angles using an angle criterion greater than 70° and less than 110°. Subsequently, a basis vector 23, preferably two non-collinear, preferably orthogonal basis vectors 23, is formed from the mean of the validated array vectors. Preferably, during the detection of the detected wells, the image stream or a single frame of the image stream is straightened by determining a rotation angle for the image stream or a single frame of the image stream and then rotating the image stream, in particular a single frame of the image stream, together with the detected wells 13 and basis vectors.

[0058] In particular the Fig. 5 The determination of a basis vector 23 can be deduced.

[0059] To construct the wave lattice 15, the determined basis vector 23 – with a positive or negative sign – is added to the center point of a detected well. This yields a presumed center point of an adjacent well. Then, a search is conducted within a predetermined radius around the presumed center point for a detected center point of a detected well. Preferably, the quadratic distance formula is used to check whether the presumed center point is close enough to a detected center point of a detected well. This procedure is carried out for both orthogonal basis vectors in the positive and negative directions to find all possible adjacent wells. In this way, the wave lattice 15, which is particularly relative, is successively assembled.

[0060] The corrugated grid 15 constructed in this way is preferably validated by comparing the number of detected rows and columns with the number of rows and columns stored for a corresponding multiwell plate type. If a larger number of rows and / or columns is detected than the corresponding multiwell plate type is permitted to have, those excess rows and / or columns located at the edge, which have the fewest detected wells, are preferably removed, as these rows and / or columns then appear implausible.

[0061] Preferably, connecting lines linking the centers of wells 13 arranged side by side along a basis vector 23 are recognized as grid lines of the well grid 15. Such a grid line corresponds in particular to either a column or a row of wells 13 of the multiwell plate 3. Such grid lines are preferably used to identify the edges 25 of the multiwell plate 3. Knowledge of the edges 25, or of which grid lines lie at an edge of the multiwell plate 3, is in turn relevant for determining the absolute coordinates of the wells 13, especially if not all rows and / or columns of wells 13 of the multiwell plate 3 could be determined.

[0062] To estimate the position of the edge or a border 25 of the multiwell plate 3, an outer grid line is preferably shifted outwards by the basis vector 23 that is perpendicular to the grid line. Since the grid line runs parallel to the edge, the orientation of the border line or border 25 and its position are then at least approximately known.

[0063] If all rows and columns of the multiwell plate 3 have been correctly detected, the absolute coordinates of the wells 13 can be readily obtained from the relative well grid 15. If, however, some wells 13 have not been detected, particularly if entire columns and / or rows are missing, it is necessary to determine, based on further information, which of the detected wells 13 are located at the edge of the multiwell plate 3 in order to ascertain the absolute coordinates. Preferably, a detected edge 25 is used as the primary criterion for this. If such an edge 25 is not available, the position of the outermost detected wells 13 at an image edge, particularly at the left / right or top / bottom image edge, is preferably used. If this is also not possible, the number of detected wells 13 at an outer grid line is preferably used as the criterion.

[0064] The absolute coordinates are preferably determined from the relative coordinates of the relative well grid 15 starting from the wells 13 located at the edge of the multiwell plate 3, taking into account a predetermined counting direction, for example ascending from the left and descending from the top.

[0065] Finally, the absolute coordinate of target well 1 is derived and output.

[0066] Furthermore, the Fig. 6 a determination of an absolute coordinate according to procedure step b) as well as a recognition of multiwell plate edges 17.

[0067] The Fig. 7 In a schematic representation, the individual frame of the image stream of the optical sensor is shown according to one of the Figures 3, 4, 5 and 6 to be extracted, whereby an absolute coordinate of the target well was determined according to procedure step b).

[0068] The Fig. 8It can be deduced that such a determination of an absolute coordinate - as in Figure 6 shown - can also be carried out or is feasible if the entire multiwell plate 3 is not depicted in the image stream, especially in a single frame of the image stream.

Claims

1. Method for determining an absolute coordinate for a target well (1) of a multiwell plate (3) for carrying out a pipetting process into the target well (1) using a dispensing pipette (5), wherein the target well (1) is the well of the multiwell plate (3) which is closest to a dispensing pipette tip (7) of the dispensing pipette (5), wherein an optical sensor for recording an image stream (9) is arranged on the dispensing pipette (5) in such a way that a surrounding of the dispensing pipette tip (7), including the dispensing pipette tip (7), is imaged in the image stream (9), wherein the image stream (9) is evaluated for an image of a region (11) of the multiwell plate (3) in the image stream (9), and wherein the following method steps are carried out when the image of a region (11) of the multiwell plate (3) is detected in the image stream (9): a) detecting at least three, preferably eight, wells (13) of the multiwell plate (3) in the imaged region (11) of the multiwell plate (3), b) creating a model of the multiwell plate (3) based on the wells (13) detected in step a) and determining the absolute coordinate of the target well (1) based on the model, wherein the model of the multiwell plate (3) is created by: b1) applying a well grid (15) to the detected wells (13) and preferably extending it beyond the detected wells (13), from which the model is obtained, wherein a relative well grid of the model of the multiwell plate (3) is used as the well grid (15), wherein relative 2D coordinates, required for determining the relative well grid, of the wells (13) detected according to method step a) are determined by means of relative coordinates of neighbouring regular features, and / or b2) the detected wells (13) are compared with a plurality of layouts of known and / or predefinable multiwell plates, wherein the layout from the plurality of layouts exhibiting the highest match with the detected wells (13) is selected as the selected layout, wherein the model is obtained from the selected layout.

2. Method according to claim 1, characterised in that the image stream (9) from the optical sensor, in particular individual frames of the image stream, is pre-processed using a Gaussian blur filter.

3. Method according to claim 1 or 2, characterised in that, for the detection of the wells (13) of the multiwell plate (3) according to method step a), edge detection is performed to detect regular features, wherein preferably the determination of parameters for the edge detection is based on a median of the grey values of the captured image stream, in particular the region (11) of the multiwell plate in the image stream (9), wherein the edge detection is preferably performed using a Canny algorithm and is subsequently preferably followed by edge enhancement.

4. Method according to any of the preceding claims, characterised in that, for the detection of the wells (13) of the multiwell plate (3) according to method step a), a Hough transform is performed, preferably for the identification of circular features.

5. Method according to any of the preceding claims, characterised in that, in method step b1), when determining the model of the multiwell plate (3), detection of multiwell plate edges (17) in a multiwell plate edge region (19) of the multiwell plate (3) in the image stream (9) is performed, wherein the multiwell plate edge region (19) lies within a definable region or at a definable multiwell plate edge distance from the outermost wells (21) of the model of the multiwell plate (3).

6. Method according to any of the preceding claims, characterised in that, in step b1), the relative 2D coordinates required to determine the relative well grid are determined by a recursive determination using the relative coordinates of the neighbouring regular features, in particular neighbouring wells of the traget well (1).

7. Method according to any of the preceding claims, characterised in that, in step b2), when determining a relative well grid of the model of the multiwell plate (3), in particular of the selected layout from the plurality of layouts, a multiwell plate edge region (19) of the multiwell plate (3) is obtained by shifting the multiwell plate edge region (19) outwards relative to the multiwell plate (3), starting from straight rows of outer wells (21), which are based either on detected wells (13) according to method step a) and / or on wells (13) obtained by extending the model, by a corresponding base vector (23), wherein an edge (25) of the multiwell plate (3) is obtained by, in particular, checking whether an edge (25) can be detected in the multiwell plate edge region (19) within the image stream (9) of the optical sensor, and wherein preferably the corresponding base vector (23) is based on the basis of a smallest and / or most frequently detected well distance between the wells (13) detected according to method step a) or on the basis of a well distance of a selected layout from the plurality of layouts according to method step b2).

8. Addressing unit (27) for a dispensing pipette (5), in particular a hand-held dispensing pipette, with a dispensing pipette tip (7), comprising a base body (29) with a dispensing pipette holding device (31) which is adapted to be connected to a dispensing pipette (5) in an operating position, wherein the base body (29) comprises a communication device and an optical sensor, wherein the communication device is operatively connected to the optical sensor, wherein a focus and / or a field of view of the optical sensor is, in the operating position, focused and / or directed onto the dispensing pipette tip (7) of the dispensing pipette (5), wherein the addressing unit (27) comprises an evaluation device which is operatively connected to the communication device, wherein the evaluation device is adapted to carry out a method according to any of the preceding claims.

9. Addressing unit (27) according to claim 8, characterised in that the evaluation device is assigned to the base body (29).