DEVICE FOR DETERMINING OPTICAL PROPERTIES OF AN OPTICALLY TRANSPARENT SUBSTRATE AND COATING SYSTEM

Description

[0001] The invention relates to a device for determining optical properties of an optically transparent substrate and a coating system for producing an optically transparent substrate.

[0002] In the production of optically transparent substrates, for example for building glazing and solar modules, coatings are typically applied to the substrate to create a desired property profile, such as with regard to transmission properties or thermal insulation. In this context, it is of great importance to be able to reliably determine the quality and the actual optical behavior achieved by the coated substrate.

[0003] In this context, devices are known in which the coated substrate is examined by means of a measuring unit configured to emit electromagnetic radiation towards the substrate. For this purpose, the measuring unit has an emission unit oriented perpendicular to the surface of the substrate, so that it can be irradiated with electromagnetic radiation that thus strikes the substrate perpendicularly. The transmission and reflection of the electromagnetic radiation can be measured via detector units associated with the emission unit, and conclusions can be drawn about the quality of the coated substrate.

[0004] One disadvantage of known solutions is that they cannot simultaneously measure transmission and reflection at the coated substrate. This increases the required measurement times and is particularly problematic in coating systems where the substrate is moved along a processing direction, necessitating measurements on the moving substrate. The time-staggered measurement and the moving substrate result in a comparatively large measurement range, making a precise determination of the substrate's properties more difficult.

[0005] US Patent 2012 / 0044344 A1 describes a system for detecting defects in a transparent substrate, comprising an illumination module and an imaging module. The illumination module has a first illumination component and a second illumination component, each assigned to a top and bottom surface of the substrate, respectively. The first illumination component emits focused light generated by an optical element, while the second illumination component emits diffused light by means of an optical diffuser.

[0006] EP2533032 describes a system for determining the optical properties of an optically transparent substrate which has a substrate coating on one side.

[0007] The object of the invention is to provide a device with which the optical properties of an optically transparent substrate can be reliably and precisely determined.

[0008] The object of the invention is achieved by a device for determining the optical properties of an optically transparent substrate, which is provided on one side with a substrate coating. The device comprises a first measuring unit and a second measuring unit, wherein the first measuring unit is assigned to the first side of the substrate and the second measuring unit to a second side of the substrate, which is opposite to the first side. The first measuring unit comprises a first emission unit for irradiating a measuring area of ​​the substrate with directed electromagnetic radiation and a first detector unit. The second measuring unit comprises at least a second emission unit for irradiating the measuring area of ​​the substrate with directed electromagnetic radiation and at least a second detector unit.The device has a first operating mode and a second operating mode, wherein in the first operating mode the first emission unit is active and the second emission unit is inactive, and in the second operating mode the first emission unit is inactive and the second emission unit is active, such that in the first operating mode the electromagnetic radiation reflected by the substrate coating in the measuring area can be detected in the first detector unit and the electromagnetic radiation transmitted by the substrate in the measuring area can be detected in the second detector unit, and in the second operating mode the electromagnetic radiation transmitted by the substrate in the measuring area can be detected in the second detector unit.

[0009] The invention is based on the fundamental idea of ​​using the same measuring range to determine various parameters of the coated, optically transparent substrate, allowing conclusions to be drawn about the quality of the substrate, including the substrate coating applied to it. The device according to the invention is designed such that, in the first operating mode, both the reflection caused by the substrate coating (i.e., the reflection associated with the first side of the substrate) and the transmission through the substrate can be measured simultaneously. In other words, the electromagnetic radiation emitted by the first emission unit, after interacting with the coated substrate, interacts with both the first detector unit (associated with the first side of the substrate) and the second detector unit (associated with the second side of the substrate).In this way, the measurement time can be reduced and the size of the measurement range minimized, regardless of whether the substrate remains in its position or is moved during the measurement.

[0010] At the same time, various emission units are provided which can be used to determine different optical properties of the coated substrate in the same measuring range, whereby the respective measuring conditions are influenced by coatings applied to the first side and / or the second side of the substrate.

[0011] It is understood that the substrate coating on the first side may only partially cover the first side. Furthermore, the second side may also be coated with a substrate layer, and the substrate coatings on the first and second sides may be the same or different. The substrate coating may also comprise one or more layers. The crucial factor is that the coatings applied to the optically transparent substrate result in a still optically transparent coated substrate.

[0012] According to the invention, the first and second emission units emit directed electromagnetic radiation. In this context, the term "directed electromagnetic radiation" means that the electromagnetic radiation is free of scattered light components, apart from unavoidable scattered light components from the surroundings of the measuring area. This makes it possible to minimize potential sources of error in the measurement data obtained by the detector units and thus optimize the quality in determining the optical properties of the substrate.

[0013] The first emission unit and / or the second emission unit can be arranged relative to the first or second side of the substrate such that the emitted electromagnetic radiation has a first or second emission angle in the range of 3 to 10° relative to the normal of the first or second side of the substrate, for example, a first or second emission angle of 8°. In other words, this configuration incorporates a certain angular offset of the corresponding emission unit to the surface of the coated substrate, enabling simultaneous measurement of reflection and transmission and ensuring that both measurements are taken within the same measurement range.

[0014] The angular tolerance of the first and second emission angles can be defined by a tolerance range that depends on the substrate thickness and the refractive index of the substrate. For example, the angular tolerance is ±1.5° for a substrate thickness of up to 30 mm and a refractive index of up to 1.6.

[0015] Preferably, the first emission unit, the second emission unit, the first detector unit and the second detector unit are arranged relative to each other such that a first connecting line extending from the first emission unit towards the second detector unit intersects with a second connecting line in the measuring area of ​​the substrate, which extends from the second emission unit towards the first detector unit.

[0016] The first connecting line and the second connecting line thus essentially correspond to the transmission beam path of the directed electromagnetic radiation emitted by the respective emission unit.

[0017] A parallel offset of the transmission beam path caused by refraction effects in the substrate is disregarded with respect to the first or second connecting line, since this can be compensated for by the arrangement of the first detector unit or the second detector unit within the respective measuring units and can therefore be tolerated.

[0018] The first and / or second detector unit can comprise a visible-infrared (VIS) spectrometer and / or a near-infrared (NIR) spectrometer. Each detector unit can be configured to detect electromagnetic radiation in the visible and near-infrared regions of the light spectrum. Determining the properties of the optically transparent substrate in these wavelength ranges is particularly important for verifying its suitability for the intended application. For example, detection using a VIS spectrometer allows for the determination of the optical appearance produced by the coated substrate in the human eye, such as the determination of color perception. A NIR spectrometer can provide information on the thermal behavior of the coated substrate.

[0019] To further increase the measurement speed of the device, a switching element can be assigned to the first and / or second emission unit. This switching element allows an electromagnetic radiation source to be activated, thereby switching the first or second emission unit. In particular, the switching element can be integrated into the respective emission unit. With this design, the electromagnetic radiation source itself does not need to be switched on or off when the device switches from the first to the second operating mode. Instead, the time delay required when changing the operating modes of the device is simply selectable via the switching time of the switching element.

[0020] Preferably, the switching element has a switching time of 30 ms or less, particularly 10 ms or less. Switching elements with a corresponding switching time are known. For example, the switching element could be a fiber optic switch.

[0021] The measuring range can have a length of 30 mm or less, in particular 20 mm or less, for example 12 mm or less. This allows for a particularly precise determination of the optical properties of the substrate, since the measurement data obtained are representative for a comparatively small area of ​​the substrate, thus minimizing or eliminating errors caused by averaged measurement data. A measuring range of such lengths is achievable through the inventive design and coordination between the first emission unit, first detector unit, second emission unit, and second detector unit.

[0022] The geometric shape of the measuring area on the substrate surface, i.e., its cross-section, is not further restricted. For example, the measuring area can be circular, oval, square, or rectangular. In each case, the length of the measuring area refers to its extent along the direction in which it is greatest.

[0023] In one variant, the first measuring unit and / or the second measuring unit has a third emission unit for irradiating the measuring area of ​​the substrate with directed electromagnetic radiation, as well as a third detector unit associated with the third emission unit. The third emission unit is arranged relative to the first or second side of the substrate such that the emitted electromagnetic radiation has a third emission angle relative to the normal of the first or second side of the substrate.

[0024] The third emission angle can be flexibly chosen, depending on which property of the coated substrate is to be determined based on the measurement data obtained in the third detector unit.

[0025] The third emission angle lies particularly in the range of 45 to 65°.

[0026] The optical properties of a coated substrate can vary considerably depending on the viewing angle. The third emission unit makes it possible to reliably determine the appearance of the substrate even at a relatively steep angle relative to its surface. In this way, the color of the optical substrate can be determined, particularly on the first and second sides.

[0027] Furthermore, this method can be used to verify that the coated substrate does not exhibit so-called "flip-flop" effects. This refers to situations where the optical impression created by the coated substrate, particularly the perceived color, changes significantly or abruptly with a relatively small change in the viewing angle.

[0028] It is understood that the third emission unit can be assigned solely to the first side, in particular being a component of the first measuring unit, or it can be assigned solely to the second side, in particular being a component of the second measuring unit. A third emission unit can also be integrated into both the first and the second measuring units.

[0029] To enable optimal measurement depending on the application, the third emission unit can be adjusted in steps or continuously. In this way, the color impression can be determined via the third emission unit at different viewing angles.

[0030] The point in time at which the third emission unit is active can be flexibly selected. For example, the third emission unit can be active in the first and / or second operating mode. Because the third emission angle deviates (significantly) from the first and second emission angles, for example by more than 40°, the electromagnetic radiation emitted by the first and second emission units and the third emission unit is not affected or only negligibly affected.

[0031] The electromagnetic radiation has a wavelength in the range of 350 to 2500 nm, for example, 350 to 1600 nm, preferably 350 to 1200 nm, and more preferably 380 to 1000 nm. At wavelengths below 350 nm, UV properties of the coated substrate would already be measured, which are irrelevant to the impression the coated substrate creates when viewed by the human eye. Wavelengths above 2500 nm are technically difficult to achieve. Furthermore, measurements at wavelengths above 2500 nm can be subject to larger error ranges due to the effects of ambient heat.

[0032] Furthermore, at least one measuring head can be provided which has the first measuring unit and / or the second measuring unit, wherein the measuring head is movable along the substrate.

[0033] In this way, the optical properties of the coated substrate can be measured at various points on the substrate. Furthermore, the measuring head can follow the substrate if it is moved within the device, thus achieving the smallest possible measuring range even in this case.

[0034] The device can have a transport mechanism with which the substrate can be moved along a processing direction, in particular wherein the substrate can be moved along the processing direction at a speed of several meters per minute. For example, the speed at which the substrate can be moved along the processing direction is in the range of 9 to 25 m / min. In this way, the throughput of the investigated coated substrates of the device according to the invention can be increased and the handling of the coated substrate within the device can be facilitated.

[0035] Preferably, the transport device is combined with the previously described movable measuring head, wherein the movement of the measuring head is coordinated with the movement of the substrate.

[0036] The measuring head has a traverse speed that is equal to or greater than the speed at which the substrate is moved along the processing direction. For example, the speed of the measuring head is up to 800 mm / s, preferably up to 600 mm / s. However, it is understood that the traverse speed of the measuring head only needs to be adapted to the specific measuring procedure being performed.

[0037] Preferably, the device is configured to determine the optical properties of the substrate in several measuring ranges, wherein at least one measurement is performed in the first operating mode of the device and one measurement in the second operating mode of the device for each of the measuring ranges. In other words, the device is configured to scan the coated substrate. In this way, property profiles of the coated substrate can be determined across its entire extent, from which it can be determined how uniform or consistent the coated substrate is across the different measuring ranges.

[0038] Additionally, the device can include a unit for measuring the substrate's surface resistance, in particular for performing an eddy current measurement in the substrate's measuring area. The surface resistance allows the substrate's properties to be investigated via a complementary method for determining its optical properties, in order to ascertain further parameters of the coated substrate and / or to verify the information obtained by the detector units. For example, the eddy current measurement can be used to draw conclusions about the crystal structure of the substrate and / or the substrate coating.

[0039] The object of the invention is further achieved by a coating system for producing an optically transparent substrate with a substrate coating applied to a first side of the substrate, which includes a device for determining optical properties of the optically transparent substrate as described above.

[0040] The properties and features of the device according to the invention apply accordingly to the coating system according to the invention and vice versa, and reference is made to the above explanations.

[0041] The device for determining optical properties can be directly connected to a coating module of the coating system or be spatially separated from it.

[0042] In one variant, the device for determining optical properties is integrated into the coating system in such a way that the optical properties of the optically transparent substrate are measured during the coating process itself. For example, the measuring area is selected in a portion of the substrate that has already been coated, while upstream along a processing direction of the coating system, another portion of the substrate is being coated. In this variant, it is possible to adjust the coating process based on the determined optical properties.

[0043] In an alternative and preferred embodiment, the device for determining optical properties is a separate module of the coating system, so that it is not influenced by other modules of the coating system. In other words, the device according to the invention serves in particular as an "ex-situ" measuring device. Furthermore, such a design allows the production of the coated substrate to be separated temporally and / or spatially from the determination of the optical properties of the coated substrate, thereby increasing the flexibility in the manufacturing process of the coated substrate.

[0044] Further features and characteristics of the invention will become apparent from the following description of exemplary embodiments, which are not to be understood in a limiting sense, as well as from the drawings to which reference is made. These show: Fig. 1 a coating system according to the invention, Fig. 2 a device according to the invention for determining optical properties, as used in the coating system according to Fig. 1 is used Fig. 3 the device Fig. 2 in a first operating mode, and Fig. 4 the device Fig. 2 in a second operating mode, and Fig. 5 another embodiment of the device according to the invention Fig. 2 .

[0045] Fig. 1 schematically shows a coating system 10 for applying a substrate coating 12 to an optically transparent substrate 14 (cf. Fig. 2 ).

[0046] Substrate 14, for example, is made of glass or plastic and is essentially flat. For instance, substrate 14 might be a plate with a rectangular cross-section and external dimensions of up to 4 x 9 meters. However, the type and shape of substrate 14 are not fundamentally restricted, as long as it is optically transparent and can be handled by the coating system 10.

[0047] In the following, the substrate 14 provided with the substrate coating 12 will also be referred to as "coated substrate 14".

[0048] The coating system 10 has a loading module 16, a coating module 18, a washing module 20 and an unloading module 22, which are arranged successively along a processing direction B.

[0049] The loading module 16 serves to load the substrate 14 onto a roller arrangement 23 of the coating system 10, with which the substrate 14 can be moved along the processing direction B.

[0050] In coating module 18, the substrate coating 12 is applied to the substrate 14. The type of substrate coating 12 is not further restricted, as long as the coated substrate 14 is also optically transparent. For example, the substrate coating 12 could be an anti-reflective coating, a thermal coating, and / or a protective coating.

[0051] In washing module 20, any residues from the coating process in coating module 18 are removed.

[0052] The coated substrate 14 can be removed from the discharge module 22, for example by means of a (not shown) removal mechanism.

[0053] The number and type of modules in Fig. 1 The coating system 10 shown is merely an example, so naturally there may also be other and / or different modules in the coating system 10.

[0054] Furthermore, the coating system 10 has a device 24 for determining optical properties of the optically transparent substrate 14.

[0055] As in Fig. 1 In the schematic representation, the device 24 is arranged separately from the other modules of the coating system 10, so that the device 24 can be operated independently of them. Naturally, the device 24 can also be integrated into the sequence of the other modules of the coating system 10 along the processing direction B. For example, the device 24 can be arranged between the washing module 20 and the unloading module 22.

[0056] The device 24 has a transport device 26 with which the substrate 14 can be moved through the device 24 along the processing direction B, for example at a speed of 5 m / min or less.

[0057] In addition, the device 24 has a measuring head 28 which includes a first measuring unit 30 and a second measuring unit 32.

[0058] The measuring head 28 is connected to a control module 34 via signal transmission, so that the components of the measuring head 28 can be controlled by means of the control module 34 and measurement data collected by the measuring head 28 can be transmitted to the control module 34 and evaluated by it.

[0059] The control module 34 is also designed to control the other components of the device 24.

[0060] In Fig. 2 Selected components of the device 24 and their arrangement relative to the coated substrate 14 are shown in more detail.

[0061] As in Fig. 2 As can be seen, in the embodiment shown, the substrate coating 12 completely covers a first side 36 of the substrate 14, while there is no substrate coating on a second side 38 of the substrate 14 opposite the first side 36.

[0062] Naturally, substrate 14 can also differ from that described in Fig. 2 The substrate coating 12 can be applied to the substrate 14 in the embodiment shown. For example, the substrate coating 12 can also be applied only to partial areas of the first side 36 of the substrate 14. Furthermore, the substrate coating 12 can also comprise several partial layers. Additionally, a substrate coating 12 can be present on both the first side 36 and the second side 38 of the substrate 14.

[0063] The first measuring unit 30 has a first emission unit 40 which is set up to emit directed electromagnetic radiation onto a measuring area 42 of the substrate 14.

[0064] For this purpose, the first emission unit 40 is connected to a first source 44 of electromagnetic radiation, wherein a switching element 46 is arranged between the first source 44 and the first emission unit 40, by means of which the first source 44 can be switched on. In other words, it can be determined via the switching element 46 whether electromagnetic radiation from the source 44 reaches the first emission unit 40 and thus whether the first emission unit 40 is active or not. The switching time of the first emission unit 40 is therefore determined by the switching time of the switching element 46.

[0065] The switching element 46 is preferably a fiber switch to enable particularly fast switching and has in particular a switching time of 30 ms or less.

[0066] Furthermore, a second source 48 for electromagnetic radiation is available, which can also be switched on via the switching element 46.

[0067] The first source 44 and the second source 48 preferably provide electromagnetic radiation of different wavelengths or wavelength ranges, so that directed electromagnetic radiation of different wavelengths can be emitted via the first emission unit 40, depending on whether the first source 44 and / or the second source 48 is switched on via the switching element 46.

[0068] For example, the first source 44 provides electromagnetic radiation with a wavelength in the visible range of the light spectrum, and the second source 48 provides electromagnetic radiation with a wavelength in the near-infrared range of the light spectrum.

[0069] Sources 44 and 48 are, for example, LEDs and / or halogen lamps.

[0070] In principle, instead of several sources 44 and 48, there can also be only a single source of electromagnetic radiation if this alone can provide electromagnetic radiation of the desired wavelength range.

[0071] It is understood that the switching element 46 is adapted to the specific type and number of sources 44 and 48 used. Accordingly, the switching element 46 can have one or more connection points for the sources 44 and 48 and one or more outputs, which are connected to the respective associated emission unit. In the Fig. 2 bis 4 The illustrated embodiment shows a variant in which the switching elements 46 each have several connection points and a single output.

[0072] In Fig. 5 Another variant is shown in which the switching element 46 assigned to the first emission unit 40 has several connection points and a single output, while the switching element 46 assigned to the second emission unit 58 has several connection points and several outputs.

[0073] The measuring range 42 has a length of 30 mm or less, where the length describes the extent of the measuring range 42 along the direction in which the measuring range 42 is greatest. In the Fig. 2 In the variant shown, this is the extension parallel to the processing direction B.

[0074] The first measuring unit 30 also has a first detector unit 50, which includes a sensor element 52, a VIS spectrometer 54 and a NIR spectrometer 56.

[0075] The sensor element 52 is designed to detect electromagnetic radiation incident on it, whereby an intensity distribution can be determined as a function of the wavelength of the incident electromagnetic radiation. Based on these measurement data, an evaluation can be carried out in the VIS spectrometer 54 (for the visible region of the light spectrum) or in the NIR spectrometer 56 (for the near-infrared region of the light spectrum), which allows conclusions to be drawn about the optical properties of the coated substrate 14.

[0076] The second measuring unit 32, analogous to the first measuring unit 30, has a second emission unit 58, which is configured to emit directed electromagnetic radiation onto the same measuring area 42 of the substrate 14 that can also be irradiated by the first measuring unit 30. However, the second emission unit 58 irradiates the measuring area 42 from the second side 38 of the substrate 14.

[0077] The second emission unit 58 is also connected via a switching element 46 of the second measuring unit 32 to a first source 44 and a second source 48 for electromagnetic radiation.

[0078] Likewise, the second emission unit 58 has a second detector unit 60, which also includes a sensor element 52, a VIS spectrometer 54 and a NIR spectrometer 56 analogous to the first detector unit 50.

[0079] The first emission unit 40 and the second emission unit 58 are aligned relative to the coated substrate 14 such that the electromagnetic radiation emitted by the first emission unit 40 and the second emission unit 58 strikes the substrate 14 at a first emission angle α 1 and a second emission angle α 2 respectively at a normal 59 of the first side 36 and the second side 38 respectively.

[0080] According to the invention, the first emission angle α 1 and the second emission angle α 2 are not equal to 0° and are in particular in the range of 3 to 10°, for example 8°.

[0081] The second measuring unit 32 further has a third emission unit 62, which is also configured to irradiate the same measuring area 42 with electromagnetic radiation as the first emission unit 40 and the second emission unit 58. For this purpose, the third emission unit 62 is also connected to the first source 44 and the second source 48 in the same way as the second emission unit 58.

[0082] As in Fig. 2 As can be seen, the third emission unit 62 is not connected to the first source 44 and the second source 48 via the switching element 46 of the second measuring unit 32. Of course, the third emission unit 62 can also have an analog switching element 46.

[0083] It is also possible that the switching element 46 has several outputs as described above, with one of the outputs being connected to the third emission unit 62. Such a further embodiment is shown in Fig. 5 shown, the further embodiment being otherwise the embodiment according to Fig. 2 bis 4 This corresponds to the fact that the explanations regarding this embodiment also apply analogously to the embodiment according to Fig. 5 apply.

[0084] The second measuring unit 32 also has a third detector unit 64, which is assigned to the third emission unit 62 and includes a sensor element 52 and a VIS spectrometer 54.

[0085] The electromagnetic radiation emitted by the third emission unit 62 strikes the second side 38 of the substrate 14 at a third emission angle α 3 relative to the normal 59, where the third emission angle α 3 is significantly larger than the first emission angle α 1 and the second emission angle α 2. For example, the third emission angle α 3 lies in the range of 45 to 65°.

[0086] The device 24 further comprises a unit 65 for performing a measurement of the surface resistance of the coated substrate 14, namely a unit for performing an eddy current measurement. The unit 65 comprises two measuring probes 66 and 68, wherein the measuring probe 66 is associated with the first side 36 of the coated substrate 14 and the measuring probe 68 with the second side 38 of the coated substrate 14.

[0087] The unit 65 enables the determination of properties of the coated substrate 14 based on the induction of currents in the coated substrate 14 and thus offers the possibility of determining the properties of the coated substrate 14 via a method that is complementary to optical measurement methods.

[0088] In this process, unit 65 examines the same measuring area 42 that was also irradiated by emission units 40, 58 and 62, for example after the substrate 14 was moved along the processing direction B to the height of the measuring probes 66 and 68.

[0089] The control of unit 65, coordinated with the other measurements, can be ensured via the control module 34, which is also connected to unit 65 via signal transmission and controls it.

[0090] The following describes the functioning of the device 24 according to the invention with reference to the Fig. 3 and 4 further explained.

[0091] According to the invention, the device 24 has a first operating mode (cf. Fig. 3 ) and a second operating mode (see Fig. 4 The first operating mode and the second operating mode differ in which emission units 40 and 58 are active.

[0092] In the first operating mode, the first emission unit 40 is active and the second emission unit 58 is inactive (see below). Fig. 3 In other words, in the first operating mode, the connection between the first emission unit 40 and the sources 44 and 48 of the first measuring unit 30 is enabled via the switching element 46 of the first measuring unit 30, while the connection between the second emission unit 58 and the sources 44 and 48 of the second measuring unit 30 is blocked via the switching element 46 of the second measuring unit 30.

[0093] Therefore, in the first operating mode, the measuring area 42 is irradiated with electromagnetic radiation only by the first emission unit 40. The electromagnetic radiation incident on the coated substrate 14 partially passes through the coated substrate 14 and is partially reflected by the coated substrate 14, namely by the substrate coating 12, resulting in a transmission beam path (indicated by arrows in the figures) and a reflection beam path (indicated by dashed arrows in the figures).

[0094] The electromagnetic radiation of the transmission beam path strikes the sensor element 52 of the second detector unit 60, while the electromagnetic radiation of the reflection beam path strikes the sensor element 52 of the first detector unit 50. Thus, according to the invention, in the first operating mode, the transmission and reflection properties of the coated substrate 14 are simultaneously investigated when irradiated from the first side 36.

[0095] In the second operating mode, the second emission unit 58 is active and the first emission unit 40 is inactive (see below). Fig. 4 In other words, in the second operating mode, the connection between the second emission unit 58 and the sources 44 and 48 of the second measuring unit 32 is enabled via the switching element 46 of the second measuring unit 32, while the connection between the first emission unit 40 and the sources 44 and 48 of the first measuring unit 30 is blocked via the switching element 46 of the first measuring unit 30.

[0096] Therefore, in the second operating mode, the measuring area 42 is irradiated with electromagnetic radiation by the second emission unit 58. The electromagnetic radiation incident on the coated substrate 14 partially passes through the coated substrate 14 and is partially reflected by the coated substrate 14, resulting in a transmission beam path (indicated in the figures by dotted arrows) and a reflection beam path (indicated in the figures by dashed-dotted arrows).

[0097] The electromagnetic radiation of the transmission beam path strikes the sensor element 52 of the first detector unit 50, while the electromagnetic radiation of the reflection beam path strikes the sensor element 52 of the second detector unit 60. Thus, according to the invention, in the second operating mode, the transmission and reflection properties of the coated substrate 14 are simultaneously investigated when irradiated from the second side 38.

[0098] In the illustrated embodiment, the third emission unit 62 is also active in both the first and second operating modes, so that the measuring area 42 is additionally irradiated with electromagnetic radiation by the third emission unit 62. This radiation is reflected from the second side 38 of the substrate 14 and strikes the sensor element 52 of the third detection unit 64 (indicated in the figures by dashed-dotted arrows). The third detection unit 64 determines the color impression that a viewer of the substrate 14 receives when looking at the second side 38 of the substrate at a viewing angle corresponding to the third emission angle.

[0099] In principle, it is also possible for the third emission unit 62 to be active only in the first operating mode or only in the second operating mode. For this purpose, the third emission unit 62 can be assigned its own switching element 46, as described above, so that the sources 44 and 48 themselves do not need to be switched on and off.

[0100] Furthermore, it is possible to determine any scattered light components that occur in the second operating mode when the second emission unit 58 is operating, using the third detector unit 64, particularly if the third emission unit 62 is not operating in the second operating mode. In this way, scattered light components can be taken into account when evaluating the measurements in the second operating mode. The same applies to the first operating mode if a third detector unit 64 is assigned to the first substrate 14 coated on side 36.

[0101] The switch between the first and second operating modes can be performed very quickly and is limited only by the switching time of the switching elements 46. Furthermore, the device 24 according to the invention is characterized by the fact that the total measurement time for determining the optical properties of the substrate 14 is significantly reduced, since the number of individual measurements to be performed is minimized by the simultaneous determination of the transmission and reflection properties of the coated substrate 14 (in the first operating mode from the first side 36 and in the second operating mode from the second side 38). In this way, a comparatively small measuring range 42 can also be achieved in which all measurements are carried out, so that the optical properties of the coated substrate 14 can be determined with high local resolution.

[0102] The measuring head 28 as a whole, the first measuring unit 30, the second measuring unit 32, and / or the unit 65 for performing a measurement of the surface resistance of the substrate 14 are preferably movable along the substrate 14. In this way, different areas of the substrate 14 can be examined, and the movements of the substrate 14 along the processing direction B can be compensated for in order to minimize the size of the measuring area 42 or to ensure that the same measuring area 42 is examined in the different operating modes and by the unit 65. In particular, multiple measurements can also be carried out.

[0103] Overall, the device 24 according to the invention is characterized by a high degree of flexibility in determining the optical properties of the coated substrate 14 and by the possibility of realizing particularly small measuring ranges. Bezugszeichenliste

[0104] 10 Coating system 12 Substrate coating 14 Substrate 16 Loading module 18 Coating module 20 Washing module 22 Unloading module 23 Roller assembly 24 Device for determining optical properties 26 Transport device 28 Measuring head 30 first measuring unit 32 second measuring unit 34 control module 36 first side of the substrate 38 second side of the substrate 40 First emission unit 42 Measuring range 44 First source 46 Switching element 48 Second source 50 First detector unit 52 Sensor element 54 VIS spectrometer 56 NIR spectrometer 58 Second emission unit 59 Normal 60 Second detector unit 62 Third emission unit 64 Third detector unit 65 Unit for performing a surface resistance measurement 66 Measuring probe 68 Measuring probe

Claims

1. A device (24) for determining optical properties of an optically transparent substrate (14) which is provided with a substrate coating (12) on a first side (36), wherein the device (24) comprises a first measuring unit (30) and a second measuring unit (32), the first measuring unit (30) being assigned to the first side (36) of the substrate (14) and the second measuring unit (32) being assigned to a second side (38) of the substrate (14) opposite to the first side (36), wherein the first measuring unit (30) comprises a first emission unit (40) for irradiating a measuring area (42) of the substrate (14) with directed electromagnetic radiation free of scattered light components and a first detector unit (50), wherein the second measuring unit (32) comprises at least a second emission unit (58) for irradiating the measuring area (42) of the substrate (14) with directed electromagnetic radiation free of scattered light components and at least a second detector unit (60), wherein the device (24) has a first operating mode and a second operating mode, wherein, in the first operating mode, the first emission unit (40) is active and the second emission unit (58) is inactive and, in the second operating mode, the first emission unit (40) is inactive and the second emission unit (58) is active, so that in the first operating mode, the electromagnetic radiation reflected by the substrate coating (12) in the measuring area (42) can be detected in the first detector unit (50) and the electromagnetic radiation transmitted by the substrate (14) in the measuring area (42) can be detected in the second detector unit (60), and in the second operating mode, the electromagnetic radiation reflected by the substrate (14) in the measuring area (42) can be detected in the second detector unit (60).

2. The device (24) according to claim 1, wherein at least one of the first emission unit (40) and the second emission unit (58) is arranged in relation to the first side (36) and, respectively, to the second side (38) of the substrate (14) such that the electromagnetic radiation emitted has a first and, respectively, a second emission angle in the range of 3 to 10° relative to the normal (59) of the first side (36) and, respectively, the second side (38) of the substrate (14).

3. The device (24) according to claim 1 or 2, wherein the substrate (14), the first emission unit (40), the second emission unit (58), the first detector unit (50) and the second detector unit (60) are arranged in relation to each other such that a first connecting line extending from the first emission unit (40) toward the second detector unit (60) intersects a second connecting line in the measuring area (42) of the substrate (14) extending from the second emission unit (58) toward the first detector unit (50).

4. The device (24) according to any one of the preceding claims, wherein at least one of the first detector unit (50) and the second detector unit (60) comprises at least one of a VIS spectrometer (54) and a NIR spectrometer (56).

5. The device (24) according to any one of the preceding claims, wherein at least one of the first emission unit (40) and the second emission unit (58) is assigned a switching element (46) by means of which a source (44, 48) of electromagnetic radiation can be connected in order to actively switch one of the first emission unit (40) and the second emission unit (58), in particular wherein the switching element (46) is integrated in the respective emission unit (40, 58).

6. The device (24) according to claim 5, wherein the switching element (46) has a switching time of 30 ms or less.

7. The device (24) according to any one of the preceding claims, wherein the measuring area (42) has a length of 30 mm or less.

8. The device (24) according to any one of the preceding claims, wherein at least one of the first measuring unit (30) and the second measuring unit (32) has a third emission unit (62) for irradiating the measuring area (42) of the substrate (14) with directed electromagnetic radiation and a third detector unit (64) assigned to the third emission unit (14), wherein the third emission unit (14) is arranged in relation to at least one of the first side (36) and the second side (38) of the substrate (14) such that the electromagnetic radiation emitted has a third emission angle relative to the normal (59) of the first side (36) and, respectively, the second side (38) of the substrate (14), in particular wherein the third emission angle is in the range of 45 to 65°.

9. The device (24) according to claim 8, wherein the third emission angle is adjustable in steps or continuously.

10. The device (24) according to any one of the preceding claims, wherein the electromagnetic radiation has a wavelength in the range from 350 to 2500 nm.

11. The device (24) according to any one of the preceding claims, wherein at least one measuring head (28) is provided which includes at least one of the first measuring unit (30) and the second measuring unit (32), and wherein the measuring head (28) is movable along the substrate (14).

12. The device (24) according to any one of the preceding claims, wherein the device (24) has a transport device (26) by means of which the substrate (14) can be moved along a processing direction.

13. The device (24) according to claim 12 if dependent on claim 11, wherein the device (24) is configured to determine the optical properties of the substrate (14) in a plurality of measuring areas (42), wherein for each of the measuring areas (42) at least one measurement is performed in the first operating mode of the device (24) and one measurement is performed in the second operating mode of the device (24).

14. The device (24) according to any one of the preceding claims, wherein the device (24) includes a unit (65) for performing a measurement of a sheet resistance of the substrate (14), in particular for performing an eddy current measurement in the measuring area (42) of the substrate (14).

15. A coating system (10) for manufacturing an optically transparent substrate (14) having a substrate coating (12) applied to a first side (36) of the substrate (14), comprising a device (24) for determining optical properties of the optically transparent substrate (14) according to any of the preceding claims.