workpiece carrier system

Abstract

workpiece carrier system (1) comprising - a freely suspended workpiece carrier (2), - a reference surface (3), - a detection unit (4) which is arranged on the workpiece carrier (2), and - a control unit (5) which is arranged on the workpiece carrier (2), - wherein the workpiece carrier (2) is freely suspended above the reference surface (3), - wherein the reference surface (3) has a characteristic pattern (6), - wherein the detection unit (4) is designed to detect at least one subsection (7) of the characteristic pattern (6), and - wherein the control unit (5) is configured to calculate a position of the workpiece carrier (2) above the reference surface (3) from the section (7) detected by the detection unit (4).

Description

State of the art

[0001] The present invention relates to a workpiece carrier system with a freely suspended workpiece carrier, wherein a position of the freely suspended workpiece carrier can be determined.

[0002] Workpiece carrier systems are known from the prior art. It is also known that workpiece carriers, especially those that are freely suspended above a surface, must be monitored to determine their position. Capacitive sensors are known for such monitoring, but their required installation space makes them unsuitable for some applications. Optical sensors, particularly stereo cameras, are expensive and complex to install, making them unsuitable for certain applications. A workpiece carrier system comprising a stereo camera for determining the position of a freely suspended workpiece carrier is known, for example, from WO 2013 / 059 934 A1.

[0003] DE 299 20 869 U1 discloses a workpiece carrier for a machine tool.

[0004] A fundamental disadvantage of existing systems is the need for a large number of sensors, which makes the workpiece carrier system very expensive. Furthermore, the large number of sensors results in a significant overall height, negatively impacting the performance of the workpiece carrier system. Disclosure of the invention

[0005] Starting from the prior art, the object of the present invention is to provide an improved workpiece carrier system which overcomes the disadvantages of the prior art.

[0006] The problem is solved by a workpiece carrier system with the features of claim 1.

[0007] The workpiece carrier system according to the invention is cost-effective and requires only a few sensors and a reference layer, which can be applied very thinly to a surface over which a workpiece carrier moves. Thus, a very reliable system can be manufactured simply and cost-effectively. The workpiece carrier system according to the invention comprises a free-floating tool carrier, a reference surface, a detection unit, and a control unit. The workpiece carrier is designed to float freely above the reference surface and is therefore preferably freely movable above it. This free-floating movement can be generated, in particular, by an electromagnetic force, so that there is no contact between the workpiece carrier and the reference surface. The detection unit and the control unit are arranged on the workpiece carrier.The system provides that the reference surface has a characteristic pattern, and the detection unit is designed to detect at least a portion of this pattern. The characteristic pattern is specifically designed such that the portion can be uniquely identified. Thus, detecting the portion enables position detection of the workpiece carrier. For this purpose, the control unit is configured to calculate the position of the workpiece carrier above the reference surface from the portion detected by the detection unit. Advantageously, the characteristic pattern is an optically structured layer of the reference surface. This includes, in particular, an area that is color-differentiated from the rest of the reference surface, making the characteristic pattern clearly recognizable.To calculate a position from a segment of the characteristic pattern, the control unit preferably has knowledge of the characteristic pattern. By comparing the segment with the known, and in particular stored, characteristic pattern, the position of the segment within the characteristic pattern can be determined, thus also revealing the position of the workpiece carrier above the reference surface. By attaching the detection unit to the workpiece carrier and providing the control unit to the workpiece carrier, the entire workpiece carrier system is very cost-effective, as the main costs are concentrated on the tool carrier. Therefore, no core system for position detection needs to be maintained across the entire reference surface. The reference surface only needs to exhibit the characteristic pattern.Furthermore, only a small distance is required between the freely suspended workpiece carrier and the reference surface. Thus, only a thin, optically structured layer needs to be applied to the reference surface to create the characteristic pattern, with the thickness of this layer being only a few micrometers.

[0008] The dependent claims describe preferred embodiments of the invention.

[0009] Preferably, the characteristic pattern is a binary pattern. It is therefore provided that the reference surface comprises two different colors, in particular black and white. The characteristic pattern is then formed by individual areas of the reference surface exhibiting either the first color, in particular black, while other areas exhibit the second color, in particular white. In this way, a high degree of interference immunity is achieved, since only the difference between the two colors needs to be detected. Furthermore, it is preferably provided that a captured subsection of the characteristic pattern can be stored in binary form, resulting in a very low required storage capacity for the storage process of the subsection.

[0010] In an advantageous embodiment of the invention, the characteristic pattern comprises a plurality of pixels. It is provided that each subsection of the characteristic pattern, comprising at least four pixels, differs from every other subsection of the characteristic pattern. The pattern is particularly advantageous in that it is the binary pattern described above, such that each pixel can be assigned either a 0 or a 1. In particular, the characteristic pattern comprises a plurality of pixels, each pixel being either black or white. The detection unit can thus detect the subsection of the characteristic pattern as a collection of four binary values. The four pixels of the subsection are, in particular, arranged in the form of a square. Since each subsection differs from every other subsection, a unique assignment of the subsection to a position of the characteristic pattern is possible.This allows for the positioning of the detection unit that captures the sub-section, and thus also the positioning of the workpiece carrier relative to the characteristic pattern and therefore relative to the reference surface. The sub-section can advantageously comprise more than four pixels, with it being particularly preferred that each sub-section be square. This design minimizes the required resolution of both the characteristic pattern and the detection unit. This allows for a simple and cost-effective provision of the workpiece carrier system.

[0011] The detection unit preferably comprises a camera, in particular a high-speed camera. The camera thus serves, in particular, to detect the portion of the characteristic pattern, which is simplified when a binary pattern is provided as the characteristic pattern. The required resolution of the camera therefore results from the design of the characteristic pattern. By appropriately selecting the characteristic pattern, that is, by providing a multitude of different shapes within the characteristic pattern, the required resolution of the detection unit, in particular the camera, can be minimized.

[0012] The camera preferably comprises an optical sensor and a lens. A deflection device is positioned upstream of the lens. This allows the optical path between the lens and the characteristic pattern to be deflected. The deflection is typically by an angle of 90 degrees, with deviations of up to 10 degrees possible. This deflection enables a narrower workpiece carrier in a vertical dimension, as the camera extends horizontally. The deflection device still allows the characteristic pattern to be captured vertically from above. This significantly reduces the overall height of the workpiece carrier compared to prior art. The deflection device thus allows the workpiece carrier to be positioned at a distance of 0 millimeters above the reference surface, enabling the characteristic pattern to be captured.This means that any minimum distance between the workpiece carrier and the reference surface, as provided for in the prior art, does not need to be maintained.

[0013] A particularly advantageous feature of the deflection device is the inclusion of a beam splitter. This beam splitter allows the optical path between the lens and the characteristic pattern to be deflected by 90 degrees. This enables the characteristic pattern to be captured from the vertical direction, while the camera itself extends horizontally.

[0014] The lens preferably includes a pinhole aperture. The pinhole aperture has, in particular, a central axis that is aligned parallel to the optical axis of the lens. The pinhole aperture increases the depth of field of the camera, allowing the float height—that is, the distance between the reference surface and the workpiece carrier—to be varied over a predefined range, while the characteristic pattern remains detectable by the camera. This increases the camera's detection accuracy.

[0015] In an alternative embodiment, the camera comprises an optical sensor and a plurality of microlenses. Each microlens projects a partial image of the characteristic pattern, particularly with a different focal point, onto a sub-area of ​​the optical sensor. In this way, the principle of a light field camera is implemented. The final image is reconstructed through various computational steps, whereby the focal point can be adjusted during image processing. Such reconstruction of final images from the plurality of captured partial images is known from the prior art.

[0016] According to another alternative, the camera features an optical sensor and a multitude of diffractive optical elements. These diffractive optical elements are primarily holographic. The use of diffractive optical elements increases the camera's depth of field. A particularly advantageous aspect of using diffractive optical elements is that the previously described deflection device, especially the beam splitter, can be omitted, even though the camera extends vertically. This is possible due to the camera's small dimensions when using diffractive optical elements, ensuring that the vertical dimensions of the free-floating workpiece carrier are not increased, even with a vertical camera extension.

[0017] Increasing the depth of field can be particularly advantageous through signal processing of the image captured by the optical sensor. Specifically, this is achieved through regularization and / or a special convolution with the imaging function. If additional sensors are available to determine the distance between the workpiece carrier and the reference surface, their data can be used. This results in improved reconstruction quality.

[0018] The workpiece carrier system advantageously features a lighting unit. This lighting unit is arranged, in particular, on the workpiece carrier. To enable or simplify the camera's detection of a portion of the characteristic pattern, the lighting unit is designed to illuminate the reference surface with light that is detectable by the camera. The lighting unit is thus advantageously located in the immediate vicinity of the camera. The lighting unit enables or simplifies, in particular, the trouble-free operation of the detection unit, especially the camera, thereby ensuring reliable position detection. The illumination is achieved, in particular, by means of light invisible to the human eye. The lighting device is especially advantageous when the camera lens, as previously described, has a pinhole aperture.While the pinhole aperture increases the depth of field, it reduces the illumination intensity of the optical sensor. This is compensated for by the illumination device. Furthermore, it is particularly advantageous if the illumination device illuminates the reference surface via the beam splitter. For this purpose, a diffuser is specifically positioned between the illumination device and the beam splitter to homogenize the illumination. The illumination can thus be directed from a different direction than the camera's optical axis intersects the beam splitter. This effectively decouples the camera and illumination device via the beam splitter.

[0019] The detection unit preferably includes a laser scanning device. This device scans the reference surface with the laser to detect a portion of the characteristic pattern. The laser scanning device allows for a greater depth of field than a camera. Furthermore, a laser scanning device can be used even with varying distances between the workpiece carrier and the reference surface without distorting the detection of the portion. The characteristic pattern is preferably adapted to a specific resolution and shape of the scanning laser, particularly a circular shape. This ensures that each scan can be assigned a unique position.

[0020] The workpiece carrier system advantageously includes a height sensor. The height sensor is preferably mounted on the workpiece carrier. Furthermore, the height sensor is designed to determine the distance between the workpiece carrier and a reference surface. The height sensor is preferably an infrared sensor and / or a laser sensor. Other sensors, such as radar sensors or ultrasonic sensors, are also possible. By providing the height sensor, in addition to the distance between the workpiece carrier and the reference surface, any tilting of the workpiece carrier relative to the reference surface can also be detected. This enables very precise position determination within six degrees of freedom.

[0021] Furthermore, the workpiece carrier system preferably features an induction loop attached to the workpiece carrier. The induction loop is electrically connected to the detection unit and / or the control unit and / or the lighting unit and / or the height gauge. Thus, electrical energy received wirelessly via the induction loop can be conducted to at least the detection unit and / or the control unit, and in particular also to the lighting unit and / or the height gauge. In this way, the induction loop provides a power supply for the height gauge and / or the lighting unit and / or the detection unit and / or the control unit. Electrical energy can be transmitted wirelessly via the induction loop, eliminating the need for wiring the freely suspended workpiece carrier.Alternatively, it is preferably provided that instead of the induction loop, a battery and / or a rechargeable battery and / or a wired power supply is provided, each of which is electrically conductive and connected to the detection unit and / or the control unit and / or the lighting unit and / or the altimeter.

[0022] The workpiece carrier system preferably includes a transmitter unit. The transmitter unit is arranged on the workpiece carrier and is, in particular, electrically connected to the control unit. The transmitter unit serves to transmit the position of the workpiece carrier above the reference surface, as determined by the control unit, to a receiver unit. The receiver unit is preferably integrated into the reference surface. Signal transmission between the transmitter unit and the receiver unit preferably occurs either by radio transmission and / or by optical transmission. If signal transmission occurs by radio transmission, it is preferably provided that the receiver unit is arranged within the reference surface and thus preferably lies below the characteristic pattern. Therefore, any interfering influence of the receiver unit on the detection of the portion of the characteristic pattern is excluded.The receiving unit is preferably electrically connected to other components to process the received position of the workpiece carrier above the reference surface. If, on the other hand, signal transmission is achieved optically, the reference surface preferably has an opening in which the receiving unit is arranged. Optical signal transmission preferably takes place using light of a characteristic wavelength. The transmitting unit is therefore preferably a light-emitting diode or another light-emitting device.

[0023] In a particularly preferred embodiment of the invention, a plurality of characteristic patterns and a plurality of receiving units are provided. The reference surface exhibits the plurality of characteristic patterns. Preferably, all characteristic patterns are identical. Furthermore, each characteristic pattern is assigned its own receiving unit. In this way, position detection is enabled by very simple means, even with large reference surfaces. If the workpiece carrier moves within an area covered by a single characteristic pattern, position detection occurs as described above.If the workpiece carrier moves between two areas covered by different characteristic patterns, its position is initially determined by the receiving unit, which receives signals from the transmitting unit, to identify the characteristic pattern over which the workpiece carrier is located. Thus, selecting the receiving unit provides a rough determination of the workpiece carrier's position. The precise determination of the position is then performed using the characteristic pattern, as described previously. The receiving unit can be selected, in particular, as the one that receives the strongest signal from the transmitting unit or the only one that receives a signal from the transmitting unit. The size of the reference area can therefore be extended as needed by repeatedly arranging identical reference patterns and assigning a receiving unit to each. Brief description of the drawing(s)

[0024] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawing. The drawing shows: Fig. 1 a schematic view of a workpiece carrier of a workpiece carrier system according to an embodiment of the invention, Fig. 2 a schematic side view of the workpiece carrier system according to the embodiment of the invention, Fig. 3 a schematic view of a characteristic pattern of a reference surface of the workpiece carrier system according to the embodiment of the invention, Fig. 4 A schematic view of a multitude of subsections, which consist of the characteristic pattern as in Fig. 3 shown, extract, Fig. 5 a schematic view of a workpiece carrier system according to a first alternative embodiment of the invention, Fig. 6 a schematic view of a workpiece carrier system according to a second alternative embodiment of the invention, and Fig. 7 a schematic view of a workpiece carrier system according to a third alternative embodiment of the invention. embodiment(s) of the invention

[0025] The Fig. 1 and Fig. Figure 2 schematically shows different views of a workpiece carrier system 1 according to an embodiment of the invention. The workpiece carrier system 1 comprises a workpiece carrier 2, which is arranged to float freely above a reference surface 3. The workpiece carrier 2 is thus freely displaceable above the reference surface 3.

[0026] To determine a relative position between workpiece carrier 2 and reference surface 3, the reference surface 3 has a characteristic pattern 6. The characteristic pattern 6 is, in particular, an optically structured layer with a thickness of a few micrometers. The characteristic pattern 6 is described below using the Fig. 3 and Fig. 4 will be explained.

[0027] The workpiece carrier 2 has a detection unit 4. The characteristic pattern 6 can be detected by the detection unit 4. This enables the position of the workpiece carrier 2 to be determined relative to the reference surface 3. The detection unit 4 is, in particular, a camera, preferably a high-speed camera. The camera is connected to a control unit 5, the control unit 5 being configured to calculate the position from the areas detected by the detection unit 4.

[0028] To simplify detection by the detection unit 4, which is designed as a camera, the workpiece carrier 2 has a lighting unit 9. The lighting unit 9 is arranged around the detection unit 4 and serves to illuminate the reference surface 3. The lighting unit preferably comprises a light-emitting diode for emitting light, the light being detectable by the detection unit 4, which is designed as a camera. It is particularly advantageous that the light emitted by the lighting unit 9 is not visible to the human eye.

[0029] Furthermore, the workpiece carrier 2 has a transmitter unit 12. The transmitter unit 12 serves to transmit the position of the workpiece carrier 2, calculated by the control unit 5, to a receiver unit 13. The receiver unit 13 is arranged within the reference area 3 and is preferably located below the characteristic pattern 6. Signal transmission between the transmitter unit 12 and the receiver unit 13 is advantageously carried out by means of radio transmission. By arranging the receiver unit 13 below the characteristic pattern 6, it is ensured that the receiver unit 13 does not interfere with the detection of the detection unit 4.

[0030] To enable or simplify the determination of the workpiece carrier 2's position in six degrees of freedom, the workpiece carrier 2 also has four height sensors 10. The height sensors 10 are arranged regularly around the detection unit 4. The height sensors 10 are designed to detect the distance between the reference surface 3 and the workpiece carrier 2. This is achieved, in particular, by means of infrared sensors and / or laser sensors and / or ultrasonic sensors and / or radar sensors. Other sensor types are also possible. Due to the number of height sensors 10, in addition to the distance of the workpiece carrier 2 to the reference surface 3, the tilting of the workpiece carrier 2 relative to the reference surface 3 can also be determined. Thus, precise position determination in six degrees of freedom is possible. The six degrees of freedom include, in particular, one translation and one rotation each along or about three independent spatial axes.

[0031] An induction loop 11 is provided for the power supply of the detection unit 4, the control unit 5, the lighting unit 9, the altimeter 10, and the transmitter unit 12. This loop is electrically connected to the aforementioned components. Thus, the electrical energy is supplied to these components via a contactless transfer to the induction loop 11. In this way, a cable connection to the workpiece carrier 2 is not necessary.

[0032] The following will be based on the Fig. 3 and Fig. Section 4 explains how to perform a position calculation. For this purpose, see below. Fig. Figure 3 shows a characteristic pattern 6 that is applied to the reference surface 3. The characteristic pattern 6 is, in particular, a binary pattern comprising a plurality of pixels 8. In the Fig. In the embodiment shown in Figure 3, the characteristic pattern 6 comprises a total of twenty-five pixels 8. These twenty-five pixels 8 are either black or white, resulting in a binary pattern. Storing the pattern requires minimal storage, as only one bit per pixel is sufficient.

[0033] Providing a binary pattern simplifies the detection process by the camera-equipped detection unit 4, as only two states need to be distinguished. For each pixel 8, it is only necessary to determine whether pixel 8 is black or white. This minimizes the susceptibility of the detection process to interference.

[0034] For position determination, a subsection 7 of the characteristic pattern 6 can be detected by the detection unit 4. From the in Fig. From the 3 characteristic patterns 6 shown, sixteen subsections 7 can thus be extracted, each comprising four pixels, which can be recognized by the detection unit 4. These are in Fig. Figure 4 shows that the choice of the characteristic pattern 6 results in sixteen sub-sections 7, each independent of the others. The choice of the characteristic pattern 6 thus allows the sub-sections 7 to overlap, enabling the extraction of a maximum number of sub-sections 7 from a characteristic pattern 6 with minimal dimensions. This allows for very precise position detection in a simple and cost-effective manner.

[0035] The position of the workpiece carrier 2 relative to the reference surface 3 can thus be determined by comparing the subsection 7 detected by the detection unit 4 with the reference pattern 6. Advantageously, the characteristic pattern 6 is stored within the control unit 5. As soon as the control unit 5 receives the detected subsection 7 from the detection unit 4, the control unit 5 compares the subsection 7 with the characteristic pattern 6 to identify the portion of the characteristic pattern 6 that corresponds to the subsection 7. Such a determination is unambiguous, since each subsection 7 is distinct from every other subsection 7.By identifying the area from the characteristic pattern 6 that corresponds to the subsection 7, the position of the detection unit 4 relative to the characteristic pattern 6, and thus the position of the workpiece carrier 2 relative to the reference surface 3, is known. The height of the workpiece carrier 2 above the reference surface 3 can be determined, in particular, by comparing the size of the detected pixels 8 with the pixels 8 of the characteristic pattern 6. Alternatively or additionally, the height of the workpiece carrier 2 can be determined using the height gauges 10.

[0036] It is particularly preferred that a large number of in Fig. The characteristic patterns 6 shown are present on the reference surface 3. All these characteristic patterns 6 are preferably identical. Therefore, determining the position of the workpiece carrier 2 is divided into two steps. First, it must be determined over which characteristic pattern 6 the workpiece carrier 2 is located. Then, its position within the characteristic pattern 6 can be determined.

[0037] For the first step, it is preferably provided that the reference surface 3 also has a plurality of receiving units 13, each receiving unit 13 being assigned to exactly one characteristic pattern 6. Thus, the receiving unit 13 that is the only one to receive a signal from the transmitting unit 12, or a signal with the strongest signal from the transmitting unit 12, can be considered the receiving unit 13 over whose assigned characteristic pattern 6 the workpiece carrier 2 is located. The coarse position determination of the workpiece carrier 2 is therefore carried out via the plurality of receiving units 13. Subsequently, a fine position determination is carried out as described above, using the characteristic pattern 6. To enable position determination, it is preferably provided that each receiving unit 13 is arranged centrally below its assigned characteristic pattern 6.

[0038] In the workpiece carrier system 1 according to the illustrated embodiment, all active components are integrated into the workpiece carrier 2. The reference surface 3 only needs to have a characteristic pattern 6 and a receiving unit 13. Thus, the sensor system necessary for position determination is completely integrated into the workpiece carrier 2, which allows the entire workpiece carrier system to be provided very cost-effectively. At the same time, position determination by detecting the characteristic pattern 6, which is in particular a binary pattern, is very simple and reliable. Furthermore, the installation space required on the workpiece carrier 2 for the components necessary for position determination is minimized. This avoids any negative impact on the workpiece carrier 2, in particular on the movement of the freely suspended workpiece carrier 2.

[0039] Fig. Figure 5 schematically shows a first alternative embodiment of a workpiece carrier system 1. The same reference numerals are used as in Fig. 1 and Fig. 2 identical or similar components as in Fig. 1, Fig. 2, Fig. 3 to Fig. 4 on.

[0040] This shows Fig. 5 a workpiece carrier system 1 comprising a workpiece carrier 2 and a reference surface 3. The reference surface 3 is analogous to that in the Fig. 2, Fig. 3 to Fig. The assembly is shown in Figure 4. The workpiece carrier 2 includes a detection unit 4 designed as a camera. The detection unit 4 comprises an optical sensor 14 and a lens 15. The lens 15, in turn, comprises a plurality of lenses 20 and a pinhole aperture 17. It is provided that a central axis of the pinhole aperture 17 is designed parallel to the optical axes of the lenses 20.

[0041] A deflecting device 16, designed as a beam splitter, is positioned upstream of the lens 15. The optical axis of the lens 15, and thus of the camera-designed detection unit 4, is oriented horizontally. However, the characteristic pattern 6 of the reference surface 3 must be detected from a vertical orientation. Therefore, the deflecting device 16 is used to deflect the optical path between the lens 15 and the characteristic pattern 6 by 90 degrees. The deflecting device 16 allows the camera-designed detection unit 4 to extend in the horizontal plane. This minimizes the thickness of the workpiece carrier 2, specifically its dimension perpendicular to the reference surface 3.At the same time, the floating height of the workpiece carrier 2 is minimized, meaning that no minimum distance between workpiece carrier 2 and reference surface 3 needs to be maintained to ensure that the characteristic pattern 6 is detected by the detection unit 4.

[0042] The pinhole aperture 17 serves to increase the depth of field. This enables the detection unit 6 to capture the characteristic pattern 6 even when the distance between the reference surface 3 and the workpiece carrier 2 is varied within a predefined interval. To compensate for any brightness losses at the optical sensor 14 that may occur due to the pinhole aperture 17, an illumination device 9 is also provided. The illumination device 9 illuminates the reference surface 3 via a diffuser 19 and the deflection device 16, which acts as a beam splitter. The diffuser 19 serves to create homogeneous illumination.Furthermore, it is provided that the lighting devices 9 direct the light onto a different side surface of the deflecting device 16, which is designed as a beam splitter, than the side surface on which the optical axis of the lens 15 meets the deflecting device 16. In this way, the detection unit 4 is spatially separated from the lighting device 9.

[0043] If the depth of field is to be further increased, the control unit 5 of the carrier system 1 is used in particular for signal processing of the finished image from the optical sensor 14. It is provided that the control unit 5 performs regularization and / or a special convolution of the imaging function. If, as described above, the height of the workpiece carrier 2 above the reference surface 3 is determined, the control unit is provided that this information is used for signal processing. In this way, improved reconstruction quality results.

[0044] Fig. Figure 6 shows a second alternative of the workpiece carrier system 1. Again, the same reference numerals indicate identical or similar components as in the Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5 on. In the in Fig. In the alternative shown in Figure 6, the detection unit 4, designed as a camera, comprises an optical sensor 14 and a lens 15. In this case, the lens 15 is designed to include at least one lens 20 and at least one diffractive optical element 21. The diffractive optical element 21 is, in particular, a holographic optical element. Due to the compact design of the lens 15 resulting from the use of the diffractive optical element 21, a very narrow design of the detection unit 4 is achieved. Thus, the use of the previously described deflection device 16 is not necessary. Instead, the detection unit 4 can be provided in a vertical orientation within the workpiece carrier 2 without increasing the thickness of the workpiece carrier 2, i.e., its dimension perpendicular to the reference surface 3. This allows for the same advantages as described in Figure 6. Fig. 5 described. The reference surface 3 is illuminated by the lighting unit 9 in the following. Fig. The alternative shown in section 6 is advantageously positioned to the side of the optical sensor 14 and the lens 15.

[0045] Finally, it showed Fig. 7 a third alternative embodiment. Again, the same reference numerals indicate identical or similar components as in Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig.6. In this alternative, the camera-type acquisition unit 4 comprises an optical sensor 4 and a plurality of microlenses 18. The acquisition unit 4 thus follows the principle of a light field camera. Various partial images of the characteristic pattern 6 with different focal points are projected onto the optical sensor 14 via the microlenses 18. The final image of the optical sensor 14 is generated by various computational steps within the control unit 5. The focal point can be adjusted during image processing. In this alternative, a finished image can only be generated by various computational steps of the control unit 5. The computational steps required to assemble the various partial images on the sensor into the final image are known from the prior art; therefore, further description is omitted.

Claims

[1] workpiece carrier system (1) comprising - a freely suspended workpiece carrier (2), - a reference surface (3), - a detection unit (4) which is arranged on the workpiece carrier (2), and - a control unit (5) which is arranged on the workpiece carrier (2), - wherein the workpiece carrier (2) is freely suspended above the reference surface (3), - wherein the reference surface (3) has a characteristic pattern (6), - wherein the detection unit (4) is designed to detect at least one subsection (7) of the characteristic pattern (6), and - wherein the control unit (5) is configured to calculate a position of the workpiece carrier (2) above the reference surface (3) from the section (7) detected by the detection unit (4). [2] Workpiece carrier system (1) according to claim 1, characterized by , that the characteristic pattern (6) is a binary pattern. [3] Workpiece carrier system (1) according to one of the preceding claims, characterized by , that the characteristic pattern (6) comprises at least four pixels (8), wherein each subsection (7) of the characteristic pattern (6) comprising at least four pixels (8) is different from every other subsection (7). [4] Workpiece carrier system (1) according to one of the preceding claims, characterized by , that the detection unit (4) includes a camera. [5] Workpiece carrier system (1) according to claim 4, characterized by , that the camera has an optical sensor (14) and a lens (50), wherein a deflecting device (16) is placed upstream of the lens (15) to deflect an optical path between lens (15) and characteristic pattern (6). [6] Workpiece carrier system (1) according to claim 5, characterized by , that the deflection device (16) includes a beam splitter. [7] Workpiece carrier system (1) according to claim 5 or 6, characterized by , that the lens (15) includes a pinhole aperture (17). [8] Workpiece carrier system (1) according to claim 5, characterized by , that the camera has the optical sensor (14) and microlenses (18), wherein each microlens (18) maps a partial image of the characteristic pattern (6) onto a partial area of ​​the optical sensor (14). [9] Workpiece carrier system (1) according to claim 4, characterized by that the camera has an optical sensor (14) and at least one diffractive optical element (21). [10] Workpiece carrier system (1) according to any one of claims 4 to 9, characterized by a lighting unit (9) wherein the lighting unit (9) is configured to illuminate the reference surface (3) with light detectable by the camera. [11] Workpiece carrier system (1) according to one of the preceding claims, characterized by , that the detection unit (4) comprises a laser scanning device. [12] Workpiece carrier system (1) according to one of the preceding claims, characterized by at least one height gauge (10) for determining a distance between the workpiece carrier (2) and the reference surface (3). [13] Workpiece carrier system (1) according to one of the preceding claims, characterized by an induction loop (11) arranged on the workpiece carrier (2), which is electrically conductively connected to the detection unit (4) and / or the control unit (5) in order to transmit electrical energy received without contact to the detection unit (4) and / or the control unit (5). [14] Workpiece carrier system (1) according to one of the preceding claims, characterized bya transmitting unit (12) attached to the workpiece carrier (2) for transmitting the position calculated by the control unit (5) to a receiving unit (13), wherein the receiving unit (13) is integrated in the reference surface (3), and wherein signal transmission between the transmitting unit (12) and the receiving unit (13) is carried out by radio transmission and / or optical transmission.

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