DEVICE AND METHOD FOR DETERMINING A POSITION AND/OR AN EXTENSION OF A DROP

Abstract

A device for determining a position and/or an extension of a drop in a position determination space, where the device has a camera having an objective and a beam splitter in the recording area of the camera, and the device is designed in such a way that light coming from the position determination space can enter the objective of the camera along a first light path as well as along a second light path, where light along the first light path can be reflected at a first reflector element in the direction of the beam splitter and can be transmitted through the beam splitter towards the objective, and where light along the second light path can be reflected at a second reflector element in the direction of the beam splitter and can be reflected at the beam splitter towards the objective.

Claims

1. Device (10) for determining a position and/or an extension of a drop (5) in a position determination space (3), wherein the device comprises a camera (14) having an objective (15) and a beam splitter (13) in the recording area (4) of the camera, wherein the device is designed in such a way that light coming from the position determination space (3) can enter the objective of the camera both along a first light path (1) and along a second light path (2) into the objective of the camera, wherein light along the first light path (1) can be reflected at a first reflector element (11) in the direction of the beam splitter and can be transmitted through the beam splitter (13) to the objective (15), and wherein light along the second light path (2) can be reflected at a second reflector element (12) in the direction of the beam splitter (13) and can be reflected at the beam splitter towards the objective (15).

2. Device (10) according to claim 1, wherein the first (1) and the second light path (2) intersect at an intersection point (6) in the position determination space (3), in particular wherein the first and the second light path intersect at right angles.

3. Device (10) according to claim 2, wherein a first path length of the first light path (1) from the intersection point (6) in the position determination space to the beam splitter (13) is equal to a second path length of the second light path (2) from the intersection point (6) in the position determination space to the beam splitter (13).

4. Device (10) according to claim 2, wherein sections of the first (1) and second (2) light paths between the intersection point (6) in the position determination space and the first (11) and second (12) reflector elements define a first plane (E1), wherein sections of the first and second light paths between the beam splitter and the first (11) and second (12) reflector elements define a second plane (E2), and wherein the second plane is arranged in a tilted manner relative to the first plane.

5. Device (10) according to claim 1, wherein the device further comprises a first (16) and a second (17) lighting element, wherein the first lighting element (16) and the first reflector element (11) are arranged on mutually opposite sides of the position determination space (3), wherein the second lighting element (17) and the second reflector element (12) are arranged on mutually opposite sides of the position determination space, wherein the first lighting element is adapted to illuminate a drop (5) in the position determination space parallel to a direction of the first light path (1) in front of the first reflector element (11), and wherein the second lighting element is adapted to illuminate a drop in the position determination space parallel to a direction of the second light path (2) in front of the second reflector element (12).

6. Device (10) according to claim 5, comprising a first (16) and a second lighting element (17), in particular wherein the first and the second lighting element are substantially identically constructed, wherein the first and the second lighting element are adapted to alternately not illuminate the position determination space (3) in a temporal respect at all or to illuminate it individually.

7. Device (10) according to claim 1, wherein the beam splitter (13), the first reflector element (11), the second reflector element (12) and the camera (14) are located outside an area comprising the position determination space and its imaginary continuation in the direction (G) of gravity.

8. Measuring device (20) for measuring an absorption of an electromagnetic radiation in a drop (5) and/or for measuring a fluorescence excited by an electromagnetic radiation in a drop (5), wherein the measuring device comprises a device (10) according to claim 1, wherein the measuring device further comprises a radiation source (21) of electromagnetic radiation and a detector (22, 22′, 22″) for electromagnetic radiation, wherein the measuring device is designed such that electromagnetic radiation can arrive at the detector along a radiation path (23) from the radiation source via a drop in the position determination space, and wherein the device is adapted to determine the position of the drop in relation to the radiation path.

9. Measuring device (20) according to claim 8, wherein the first light path (1), the second light path (2) and the radiation path (23) intersect in a common intersection point (6) in the position determination space (3).

10. Pipetting robot (30) having a device (10) according to claim 1, wherein the pipetting robot is adapted to move a pipette tip (31) into the position determination space (3) of the device, to form a drop (5) of a liquid outside an opening of the pipette tip, and to determine the position of the formed drop in the position determination space on the basis of at least one image recorded by a camera (14).

11. Pipetting robot (30) having a measuring device (20) according to claim 8 and having means for moving at least one pipette tip (31) in at least one direction of movement, wherein the pipetting robot is adapted to move the at least one pipette tip into the position determination space (3) of the device (10), to form a drop (5) of a liquid outside an opening of the pipette tip, to determine the position and/or an extension of the formed drop in the position determination space on the basis of at least one image taken with the camera (14), and to measure, by using the measuring device (20), an absorption of an electromagnetic radiation in the drop and/or to measure a fluorescence excited by an electromagnetic radiation in a drop.

12. Method for determining a concentration of a substance in a drop (5) by means of a measuring device (20) according to claim 8, comprising the steps of introducing the drop (5) into the position determination space (3) or creating the drop in the position determination space, determining the position of the position of the drop in relation to the beam path (23) of the measuring device, determining the extension of the drop, determining the optical path length of the beam path in the drop, measuring an absorption of an electromagnetic radiation, wherein electromagnetic radiation along the radiation path starting from the radiation source (21) traverses the drop in the position determination space and arrives in the detector (22, 22′, 22″), wherein a radiation intensity of the radiation source is related to a radiation intensity in the detector, and calculating the concentration as a function of the measured absorption and the determined optical path length in the drop.

13. Method according to claim 12, wherein a first extension of the drop (5) is determined before the step of measuring, wherein a second extension of the drop is determined after the step of measuring, and wherein an average value of the first and second extension of the drop is used to determine the concentration of the substance.

14. Method according to claim 12, wherein the method is a method for determining a concentration of RNA, DNA or protein, wherein the electromagnetic radiation has a wavelength characteristic of RNA, DNA or proteins.

15. Method for holding a drop (5) in the position determination space (3) of a pipetting robot (30) according to claim 10, wherein the method comprises the repeated application of the following steps: determining an actual position of a drop formed at the opening of a pipette tip (31) of the pipetting robot in the position determination space (3) on the basis of at least one image recorded by the camera (14), determining a deviation of the determined actual position from a predetermined target position, and moving the pipette tip in a direction which brings the actual position closer to the target position.

16. Method for regulating a drop size of a drop (5) in the position determination space (3) of a pipetting robot (30) according to claim 10, wherein the method comprises the repeated application of the following steps: determining an actual drop size of a drop formed at the opening of a pipette tip (31) of the pipetting robot in the position determination space (3) on the basis of at least one image recorded with the camera (14), determining a deviation of the determined actual drop size from a predetermined target drop size, and aspirating liquid into the pipette tip or ejecting liquid from the pipette tip, wherein aspiration is selected when the actual drop size is larger than the target drop size and ejection is selected when the actual drop size is smaller than the target drop size.

Description

[0084] Exemplary embodiments of the present invention are explained in more detail below using figures, wherein:

[0085] FIG. 1 shows a schematic cross-section of the device according to the invention;

[0086] FIG. 2 shows a schematic cross-section through an embodiment of the device;

[0087] FIG. 3a shows a perspective view of an embodiment of the measuring device

[0088] FIGS. 3b and 3c show schematic, perspective views of the geometric position of selected elements from FIG. 3a;

[0089] FIG. 4 shows an arrangement of an embodiment of the device in connection with a part of a pipetting robot;

[0090] FIG. 5 shows a perspective view of a pipetting robot with a device according to the invention;

[0091] FIG. 6 shows a schematic, perspective view of the situation in the position determination space for an embodiment of the measuring device or an embodiment of the pipetting robot.

[0092] FIG. 1 shows a schematic cross-section of the device 10 according to the invention. A dashed circle shows the position of the position determination space 3. Within the position determination space, a smaller dashed circle shows the possible position of a drop 5, the position and/or extension of which can be determined with the aid of the device 10. The device comprises a camera 14 with an objective 15 and a beam splitter 13 in the recording area 4 of the camera. The recording area 4 of the camera in front of the objective is schematically marked by dashed lines. It corresponds to the area from which incident light can reach an image sensor of the camera via the objective. Light from the position determination space 3 can reach the objective 15 along a first light path 1, which is drawn as a dotted line with an arrow. The light is reflected at a first reflector element 11 and radiated through the beam splitter 13. Light from the position determination space 3 can also enter the objective along a second light path 2, which is drawn as a dotted line with an arrow. In this case, the light is reflected at a second reflector element 12 and is also reflected at the beam splitter 13.

[0093] FIG. 2 shows a schematic cross-section of an embodiment of device 10. In the embodiment shown here, the first light path 1 and the second light path 2 intersect in the position determination space at a right angle. In the illustration shown, there is a drop 5, which is arranged straight at the intersection point 6 of the intersecting light paths. The intersection point 6 is located in the position determination space 3, whose position is indicated by a dashed line. The first reflector element 11 and the second reflector element 12 are arranged in the illustrated embodiment parallel to a reflecting surface of the beam splitter 13. The reflector elements 11 and 12 are further arranged symmetrically to the reflecting surface of the beam splitter 13. This results in a first path length of the first light path 1 from the intersection point 6 to the beam splitter 13 and a second path length of the second light path 2 from the intersection point 6 to the beam splitter, wherein the first and second path lengths are equally large. The embodiment shown here additionally comprises a first lighting element 16 and a second lighting element 17. Both lighting elements comprise a light emitting diode (LED) 43 and a lens 42 in the embodiment shown here. Light rays along the first light path 1 and along the second light path 2 are drawn here starting from the light emitting diode to the camera. One lighting element and one reflector element each are located on opposite sides of the position determination space. The drop is illuminated by the first lighting element 16 parallel to the first light path 1 and by the second lighting element parallel to the second light path 2. The parallelism of illumination direction and light path is determined by the direction of the section of the respective light path before the first or second reflector element. From the camera's point of view, drop 5 is illuminated from behind along both light paths and is displayed in a kind of shadow image. Alternatively to the lighting situation shown here, only one of the lighting elements can be switched on in a time-staggered manner, so that the position determination space and a drop disposed therein is illuminated by only one lighting element each. The lighting elements shown here are essentially identical in construction. A possible variant of the embodiment could include light emitting diodes of different colors.

[0094] The cross in the circle indicates the direction G of gravity, which in the situation shown is perpendicular to the image plane of the figure. Thus, the position determination space and also its imaginary continuation in direction G of gravity is free of elements of the device. A drop falling down from the position determination space in the direction of gravity will therefore not hit any of the elements of beam splitter 13, first reflector element 11, second reflector element 12 or camera 14.

[0095] A relay optic 41 is located between the beam splitter 13 and the camera 14. The camera may have a CMOS image sensor, for example.

[0096] The shown arrangement can be constructed in a very compact manner. For example, the distance from intersection point 6 to the first or second reflector element can be approx. 25 mm and the distance from intersection point 6 to one of the LEDs can be less than 30 mm.

[0097] With these dimensions and a camera with a pixel size of 10 micrometers, for example, an imaging system can be realized that achieves an optical resolution of approximately 6 micrometers per pixel, i.e. a displacement of a real object in the position determination space by 6 micrometers results in a displacement of the image by one pixel. In this case, the optical system leads to a reduction by a factor of about 1.7.

[0098] The optical layout of the embodiment shown is designed in such a way that with only two LEDs for illumination, two lenses, two mirrors, a beam splitter and a camera, a device is obtained which is suitable for determining a position and an extension of a drop, for example in the measuring chamber of a spectrometer. The LEDs are used to illuminate the drop from two directions, for example a horizontal x-direction and a perpendicular, also horizontal y-direction. In this case, the camera can take images of the drop from two different directions, but from the same distance, wherein images of the drop can be produced in an x-z plane and in a y-z plane. The z-direction in this example is the vertical direction, this means that the three-dimensional position information of the drop can be obtained with a device without moving parts. For example, two separate images can be obtained by sequentially illuminating the drop in the position determination space with only one of the two LEDs at a time. Based on such a pair of images, the size of the drop as well as the position of the drop can be regulated in three dimensions by a control loop, which for example includes the control of a pipetting robot.

[0099] In this context, it is possible to deviate temporarily from the usual software architecture of a control software, which provides that the control software controls the individual modules or devices (i.e. linear axes, pump, incubators, shakers, extraction modules, etc.) according to a predefined flow chart, in that in this case the measuring device determines how the pipette of the pipetting robot has to move based on the position data determined by the device according to the invention.

[0100] FIG. 3a shows a perspective view of an embodiment of the measuring device 20. A drop 5 is located in the center of a position determination chamber, which is provided by a cylindrical wall with through-holes for light paths 1 and 2 or a beam path 23. In this position, the drop can, for example, hang on a pipette tip not shown. The measuring device includes a device according to the invention as described above. The device comprises a first reflector element 11, a second reflector element 12, a beam splitter 13 and a camera 14 with C-mount 44 for attaching an objective. In the manner described above, a first light path 1 and a second light path 2 lead in two different ways from the position determination space into the objective of the camera, which is not shown here for reasons of clarity, but whose position is determined by the position of the C-mount 44, which defines the position of the camera near end of the objective. In the embodiment shown, the device further comprises a first lighting element 16 and a second lighting element 17. Light from the first lighting element 16 can be irradiated into the area of drop 5 through the through-hole visible in the upper right corner of the cylindrical wall. From there, the light continues to follow the first light path 1 through an invisible through-hole via the first reflector element 11, through the beam splitter 13 into the objective. Light from the second lighting element 17 can be irradiated into the area of the drop 5 through the visible through-hole in the upper left corner of the cylindrical wall. From there, the light continues to follow the second light path 2 through an invisible through-hole via reflection at the second reflector element 12 and via reflection at the beam splitter 13 into the objective of the camera. The first and second light paths coincide in the shown arrangement in the area between beam splitter 13 and C-mount 44. The measuring device 20 further comprises a radiation source (not shown) for electromagnetic radiation and a detector 22 for the electromagnetic radiation. The radiation source can be a flash lamp, for example. A radiation path 23 leads from the radiation source via a monochromator and is deflected and focused via the ellipsoid mirror 24. The radiation path passes through a through-hole in the cylindrical wall, through drop 5 and through another, invisible, through-hole to detector 22, where a radiation intensity of the electromagnetic radiation can be measured. The first and second light paths 1, 2 and the radiation path 23 define a common first plane in the area of the drop and intersect at a common point of intersection. The two light paths intersect each other at an angle of about 90° and intersect the radiation path 23 at an angle of about 45°. Due to the tilted arrangement of the first and second reflector elements 11, 12, the first and second light paths leave this plane after reflection at the respective reflector element.

[0101] The lighting elements 16, 17, for example, each comprise a light emitting diode and a lens arranged in a housing in front of the light emitting diode. The reflector elements 11, 12, for example, are designed as planar mirrors. Regarding the reflecting side, arranged behind the reflector elements 11, 12, a suspension for precise alignment of the mirrors can be seen.

[0102] FIG. 3b shows, in a reduced manner but in comparison to FIG. 3.a) in unchanged orientation, the first light path 1 and the second light path 2. The first plane E1 is defined by the first light path 1 and the second light path 2 in the area between the intersection point 6 of the light paths, the point 7 on the first reflector element where the first light path is deflected, and point 8 on the second reflector element where the second light path is deflected. The first plane is shown as dotted. The first light path 1 is shown as a dotted line, the second light path 2 as a dashed line. From points 7 and 8, the light paths extend in a second plane E2, which is inclined with respect to plane E1. The point 9 on the beam splitter 13 lies in the plane E2. From this point, the two light paths 1, 2 coincide.

[0103] FIG. 3c shows the same as FIG. 3b but from a slightly different angle. In addition, the angle α at which the first plane E1 and the second plane E2 intersect is shown. The angle α can be about 90°, for example. In one embodiment, the plane E1 can be a horizontal plane, which is perpendicular to the direction G of gravity. In this case, the light paths lead down into the objective of the camera, which is arranged below the plane E1 to save space. In this arrangement the camera is also outside of a possible falling direction of the drop.

[0104] The compact design, which is implemented in the embodiment of the device as shown in FIGS. 3a (as part of the measuring device), 3b and 3c, allows the camera to be placed underneath a work surface that is parallel to the plane E1. The reflector elements are tilted in relation to the plane E1, i.e. also in relation to the working surface. The reflector elements are also tilted with respect to a plane defined by the beam splitter. The plane defined by the beam splitter forms in this case also a symmetry plane of the two reflector elements.

[0105] FIG. 4 shows an exemplary arrangement of an embodiment of the device, as it can be arranged as part of a pipetting robot. Only one storage area for microplates and some holders 32 for standard microplates are shown. The device 10 has a round access opening, open at the top, for inserting a pipette tip into the position determination space of the device, which is located inside the cuboid housing. A further housing 18 is located below the microplate storage area and contains the camera of the device, which is not visible in this view. The housing 18 can contain further components, for example a monochromator of a spectrometer. In this embodiment, the geometrical arrangement of the position determination space and the camera can be chosen as shown in FIG. 3a, for example. In this way a very space-saving arrangement is created, where the device has only the space requirement of a single holder for standard microplate.

[0106] With the compact design shown, the device according to the invention can be ideally integrated as a module into a platform for handling liquids, especially in a platform where the standing surface of a module is critical. The embodiment shown saves space on the work surface.

[0107] FIG. 5 shows a pipetting robot 30 with a device 10 according to the invention in the context of an exemplary application. The pipetting robot comprises controllable linear axes, which can move a pipette in the three directions of a Cartesian coordinate system represented by arrows in x-, y- and z-direction. A pipetting channel 34, at the lower end of which a pipette tip is located, is connected to a pump device by a flexible tube. The pipette tip is located directly above an opening of the device 10. By lowering the pipette tip in negative z-direction, the pipette tip can be retracted into the device. Microplates 33 are arranged on a work surface of the pipetting robot. The shown microplates have 4×6 wells, but also microplates with 8×12 wells or other common microplates could be used. The space requirement of the device 10 on the working surface in relation to the microplates is shown realistically. It shows the compact design that is possible with the device according to the invention.

[0108] FIG. 6 shows schematically the arrangement of elements of an embodiment of the measuring device or the pipetting robot in connection with the position determination space of the device during a measuring process on a drop 5. The drop 5 hangs on a pipette tip 31, which is movable in x-, y- and z-direction of the illustrated Cartesian coordinate system by linear axes of a pipetting robot. A section each of the first light path 1 and the second light path 2 are drawn as dotted and dashed lines, respectively, so that the orientation of the other elements relative to the light paths of the device can be seen. A radiation path 23 of electromagnetic radiation emanates from the radiation source 21 and is deflected in the direction of the drop by a mirror 24, which can be an ellipsoid mirror, for example. A detector for measuring the intensity of the electromagnetic radiation is arranged in a straight line behind the drop. At this point the intensity reduced by absorption in the drop can be measured. Vertical to this beam direction is another detector 22′. At this point the intensity of electromagnetic radiation generated by fluorescence in the drop can be measured. Long dashed and short dashed are the sections 23′, 23″ of the radiation path between the drop and the detector for the absorption measurement and for the fluorescence measurement. In the embodiment shown here, the radiation source 21 can both provide the irradiated intensity for the absorption measurement and excite a fluorescence. In the embodiment shown here, the first light path 1, the second light path 2, the section of radiation path 23′ leading to detector 22′ for absorption and the section of radiation path 23″ leading to detector 22″ for fluorescence are all in a common plane.

[0109] It is also possible to measure fluorescence at another z-position alternatively or additionally. Thus, the following procedure is also conceivable within the scope of the invention: Determination of the drop position in x and y by means of the device for position determination and subsequent traversing of a predefined distance in z-direction. This means that the plane of the measurement does not necessarily have to correspond to the plane of the position determination.

LIST OF REFERENCE NUMERALS

[0110] 1 First light path [0111] 2 Second light path [0112] 3 Position determination space [0113] 4 Recording area of the camera [0114] 5 Drop [0115] 6 Intersection point [0116] 7 Point on first reflector element [0117] 8 Point on second reflector element [0118] 9 Point on beam splitter [0119] 10 Device [0120] 11 First reflector element [0121] 12 Second reflector element [0122] 13 Beam splitter [0123] 14 Camera [0124] 15 Objective [0125] 16 First lighting element [0126] 17 Second lighting element [0127] 18 Housing (contains camera) [0128] 20 Measuring device [0129] 21 Radiation source [0130] 22, 22′, 22″ Detector [0131] 23 Radiation path [0132] 23′, 23″ Sections of the radiation path in front of the detector [0133] 24 Ellipsoid mirror [0134] 30 Pipetting robot [0135] 31 Pipette tip [0136] 32 Holder for standard microplates [0137] 33 Microplate [0138] 34 Pipetting channel [0139] 41 Relay optic [0140] 42 Lens [0141] 43 LED [0142] 44 C-mount of the camera [0143] D Diameter of the drop [0144] E1 First plane [0145] E2 Second plane [0146] α Angle between first and second plane [0147] G Direction of gravity