Device for inspecting a planar or web-shaped object
Patent Information
- Application Number
- EP2024704412
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-14
- Filing Date
- 2024-02-09
- Publication Date
- 2025-12-24
AI Technical Summary
Existing devices for inspecting ultra-thin plate-shaped or web-shaped objects, such as glass panes or plastic films, face challenges in achieving precise optical inspection while avoiding mechanical damage and contamination, as the carrier body influences measurement accuracy and can cause damage during transportation.
A device with a one-piece vibration generator forming a flat levitation surface and having a continuous gap that allows the object to be inspected directly through the gap by an optical sensor and illuminated directly through the gap by a lighting device, ensuring accurate transmission and reflection measurements without interference from additional materials.
This solution enables precise optical inspection of ultra-thin objects by maintaining accurate levitation and avoiding mechanical damage, enhancing the accuracy of defect detection and contamination assessment without complex adjustments or material interference.
Smart Images
Figure EP2024053277_22082024_PF_FP
Abstract
Description
[0001] Device for inspecting a plate-shaped or sheet-shaped object
[0002] DESCRIPTION
[0003] The invention relates to a device for inspecting a plate-shaped or sheet-shaped object having a top side and a bottom side, for example a thin glass pane, a thin plastic film, wafer or the like, by means of an optical sensor.
[0004] For an inspection, a thin, plate-like or sheet-like object is usually transported along a conveyor belt and illuminated on the top and / or bottom using a lighting device. An optical sensor, such as a camera, detects the electromagnetic radiation transmitted through and / or reflected from the object. Based on these measurement results, the quality of the object can be assessed and / or its dimensions can be determined.
[0005] With ultra-thin plate-shaped or web-shaped objects, e.g. glass panes for mobile phones, or plastic films, mechanical damage or contamination can easily occur during transport on a conveyor belt if the object rests with its underside on the belt. To avoid this, a sonotrode with a sound-emitting surface facing the object can be used. Such a sonotrode is described, for example, in documents WO 2015 / 010681 A2 and WO 2009 / 056127 A2. The inspection device disclosed in document WO 2009 / 056127 A2 has a vibration generator with a carrier body made of a translucent material. This allows the underside of the material to be inspected to be observed through the carrier body using an optical sensor arranged below the carrier body.However, this approach is not advantageous for ultra-thin plate-like or sheet-like objects, since the carrier body influences the measurement result and reduces its accuracy.
[0006] The object is therefore to create a device and specify a method that enable precise optical inspection of a thin plate-like or sheet-like object while simultaneously avoiding mechanical damage or contamination. The above object is achieved by a device having the features of claim 1 and a method having the features of claim 9.
[0007] In particular, the object is achieved by a device for inspecting a web-shaped or plate-shaped object having a top side and a bottom side, wherein the device has a vibration generator and an optical sensor as well as a corresponding illumination device, wherein the vibration generator forms a flat levitation surface on a side facing the object, over which the object can be moved from a first end to a second end by means of a transport device, wherein the vibration frequency and the vibration amplitude of the vibration generator can be adjusted such that the object can be moved in suspension substantially parallel to the levitation surface, wherein the object can be inspected by means of the illumination device and the optical sensor, wherein the vibration generator is formed in one piece and has at least one continuous gap partially intersecting the levitation surface in such a way,that the object can be inspected directly through the gap using the optical sensor arranged on the side of the vibration generator facing away from the object and / or illuminated directly through the gap using the illumination device arranged on the side of the vibration generator facing away from the object. In the first case, the electromagnetic radiation reflected or transmitted by the object passes through the gap to the optical sensor, which receives the respective electromagnetic radiation. In the second case, the electromagnetic radiation generated by the illumination device strikes the object through the gap.
[0008] The sheet-like or plate-like object to be inspected can be a thin or ultra-thin glass pane (e.g., for a mobile phone), a wafer, a microchip, or a thin film, whereby the object can be at least partially transparent to electromagnetic radiation. The two largest, opposite sides of the object are referred to as the top and bottom, with the side of the object facing the vibration generator forming the bottom and the opposite side of the object forming the top. The thickness of such an object, measured between the top and bottom of the object, is, for example, in the range of 0.03 mm to 1 mm.
[0009] The vibration generator (also referred to as a sonotrode) is designed to form a flat levitation surface. The vibration generator can, for example, have a cuboid shape or a cuboid-like shape. The underside of the object lies opposite the levitation surface and is transported along it from a first end to a second end of the levitation surface. The direction of transport along the levitation surface is referred to below as the transport direction. The vibration frequency and the vibration amplitude of the vibration generator can be adjusted such that a standing pressure wave is generated in the air film arranged beneath the object, so that the object levitates essentially parallel to the levitation surface and thereby moves in a levitating manner in the transport direction by means of the transport device.For example, the vibration generator has dimensions in the range of 0.4 m to 3 m in length and 10 cm to 40 cm in width, with the levitation surface, for example, having a size in the range of 400 cm. 2 up to 12,000 cm 2 The frequency of the vibration generator is, for example, in the range from 10 kHz to 50 kHz, in particular in the range from 30 kHz to 40 kHz, and the amplitude is, for example, in the range from 1 pm to 50 pm. For optimal vibration generation, the vibration generator can be attached to profile elements (e.g., aluminum profile elements), for example, in such a way that it is only attached to the respective profile element at the nodal points of the vibration generator's vibration, e.g., by means of screws.
[0010] For optical inspection of the object, an optical sensor, such as a high-resolution line-scan or matrix camera, is provided to observe the electromagnetic radiation reflected and / or transmitted by the object in bright field or dark field. Accordingly, the illumination device can be designed as a line-shaped or matrix-shaped illumination device, for example as a line or matrix with a plurality of LEDs. The illumination device illuminates the object in a predetermined area, generating electromagnetic radiation in the wavelength range suitable for the respective examination. In one embodiment, the optical sensor is arranged above the top side of the object.To examine the object's transparency properties, the illumination device is positioned on the side of the vibration generator facing away from the object and illuminates the underside of the object through the gap. Alternatively, conversely, the illumination device for illuminating the top of the object can be positioned above the object, and the optical sensor can be positioned below the side of the vibration generator facing away from the object. To examine the reflected properties on the underside of the object, both the illumination device and the optical sensor can be positioned below the side of the vibration generator facing away from the object. In this case, the electromagnetic radiation emitted by the illumination device passes through the gap directly to the underside of the object.The electromagnetic radiation then reflected from the object is also guided through the gap directly to the optical sensor. Likewise, it is possible to arrange the optical sensor and the illumination device above the top side of the object in order to examine the top side of the object in reflection. Combinations of the above illumination and recording configurations are particularly advantageous for the transmitted and / or reflected electromagnetic radiation. Furthermore, the illumination angle of the illumination device can be adjusted and varied accordingly to enable analysis of the bright-field or dark-field properties of the object. For example, a single optical sensor can be arranged above the top side of the object, and at least one illumination device can be arranged above the top side of the object, and at least one illumination device can be arranged below the side of the vibration generator facing away from the object.This allows the reflection and transmission of the electromagnetic radiation, for example in the bright field, to be observed using the optical sensor. Using a second illumination device, which is also arranged above the upper side of the object at an angle different from the illumination angle of the first illumination device, the dark field reflection can additionally be measured. In such a configuration with two or more than two illumination devices and a single associated optical sensor that records the signals generated by multiple illumination devices (and the object), it is advantageous to separate the signals in terms of time and / or wavelength. With this temporal separation, the illumination devices can be switched on and off one after the other so that the illumination is only provided by a single illumination device at any given time.The signals recorded by the optical sensor can be assigned to the respective illumination signal based on their measurement period, since they are generated directly by transmission and reflection from the object. Additionally or alternatively, the illumination can be provided in different wavelength ranges, allowing discrimination of the signals recorded by the optical sensor across the respective wavelength range. For example, a first illumination device can generate electromagnetic radiation in the wavelength range 400 nm to 500 nm for illumination with a visible blue-green color, and a second illumination device can generate electromagnetic radiation in the wavelength range 600 nm to 700 nm for illumination with a visible red color.
[0011] The position and orientation of the optical sensor and the at least one lighting device in the room, particularly with respect to the reflective surface, are known. The position and orientation of the optical sensor can be determined using a known calibration method.
[0012] The optical sensor, in the form of a line scan or matrix camera, determines a brightness value and / or a color value for each pixel of an observed area of the object. In one embodiment, the color and / or brightness values of all areas of the object can be combined to form an image. The color and / or brightness values can be forwarded to the data processing unit, where they can be analyzed for defects and / or contamination. In one embodiment, by moving the object along the levitation surface and thus transversely to the optical sensor, which is stationary with respect to the levitation surface at least during the inspection, the object can be inspected over its entire top and / or bottom surface. Alternatively, parts of the top and / or bottom surface of the object can be analyzed. The data processing unit can be integrated into the optical sensor as a module or form a separate unit from the optical sensor.In the latter case, the image data is transmitted wired or wirelessly from the camera to the data processing unit. The data processing unit comprises a processor, which is a functional module that interprets and executes instructions / commands of an algorithm, as well as a command control unit, an arithmetic unit, and a logic unit. The processor can comprise at least a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA - a digital integrated circuit into which a logic circuit can be programmed), a discrete logic circuit, and any combination of these components. The data processing unit can also comprise a memory module, an input module (e.g., keyboard or touchpad), a power supply module (e.g., battery), and a display module (e.g., display).The data processing unit can be implemented as a real hardware resource, such as a smartphone, desktop computer, server, notebook, cluster / warehouse-scale computer, embedded system, or the like, or as a virtualized computing resource. Furthermore, the data processing unit can include a transmitter / receiver (transceiver) for exchanging data with the optical sensor.
[0013] Using the optical data detected by the optical sensor (e.g., intensity and / or color data) relating to the electromagnetic radiation transmitted and / or reflected by the object in the bright field and / or dark field, it is possible to detect contamination and / or defects on the object during inspection and to assign them to a specific position or area of the object. Examples of contamination and / or defects include particles, scratches, stains / discolorations, protrusions, notches, dents, bubbles, material compaction, burrs, rings, and the like arranged on the top and / or bottom of the object or within the object volume. Such contamination and / or defects are detected, for example, by a change in contrast and / or brightness in the reflected and / or transmitted electromagnetic radiation.For this purpose, the signal recorded by the optical sensor and, if necessary, digitized is forwarded to a corresponding data processing device for evaluation and determination of the contamination and / or defects. Based on the transport speed of the object and the known location of the illumination device and optical sensor, the position or area of the detected defect and / or contamination can also be determined from the signal recorded by the optical sensor and the associated measurement time. Contamination and / or defects can also be detected, for example, by measuring the deflection or a variation in the deflection of the electromagnetic radiation reflected and / or transmitted by the material of the object. This is possible, for example, using methods described in more detail in document EP 2 390 656 B1.The content of the procedure described therein is intended to be included in this description by this citation.
[0014] According to the invention, the vibration generator is formed in one piece and has at least one continuous gap partially intersecting the levitation surface in such a way that the object can be inspected directly through the gap by means of the optical sensor arranged on the side of the vibration generator facing away from the object and / or illuminated directly through the gap by means of the illumination device arranged on the side of the vibration generator facing away from the object. The gap thus allows a direct determination of the transmission properties or the reflection properties on the underside of the object, with the electromagnetic radiation transmitted or reflected by the object passing through the gap directly to the optical sensor. The illumination of the underside of the object by means of the illumination device arranged on the side of the vibration generator facing away from the object also occurs directly through the gap.This prevents any alteration of the signal by another material (e.g. the material of the vibration generator) and increases the accuracy of the optical inspection. Furthermore, the one-piece design of the vibration generator ensures that it oscillates in the same way on both sides of the gap. This means that the standing wave causing the levitation is generated evenly across the entire levitation surface. This means that the levitation of the object can be reliably achieved and counteracts mechanical damage to the sensitive object or contamination. The one-piece design of the vibration generator also avoids the complex adjustment that would be necessary when using two separate sonotrodes. In addition, the one-piece design of the vibration generator ensures that the oscillation is in phase across the entire surface of the vibration generator.For example, the distance between the bottom of the object and the levitation surface caused by levitation is 20 pm to 100 pm.
[0015] In one embodiment, the vibration generator can have a single such gap; alternatively, the vibration generator can include two or more such gaps, with at least two gaps running parallel or at a predetermined angle to each other in one embodiment. The at least one gap can have a rounded edge at the front edge in the transport direction, which is advantageous because it prevents any sagging object from getting caught in the gap during transport.
[0016] The gap is designed such that it passes through the vibration generator and partially intersects the levitation surface, so that electromagnetic radiation passes through the gap on its way from an illumination device to the object or from the object to the optical sensor - depending on the configuration of the device. Accordingly, the illumination device and / or the optical sensor are aligned such that the electromagnetic radiation passes from the illumination device via the gap to the object or from the object via the gap to the optical sensor. The gap is, for example, slit-shaped, so that only a linear area of the object is illuminated or the reflected or transmitted electromagnetic radiation is absorbed by a linear area of the object. The gap extends, for example, with its largest dimension (referred to as the length) transversely, e.g.perpendicular to the transport direction of the object over the levitation surface, wherein in one embodiment the length of the gap transverse to the transport direction is equal to or greater than the width of the object. For example, the length of the gap in the region of the levitation surface is equal to or greater than 10 cm. The width of the gap in the region of the levitation surface is, for example, equal to or greater than 0.5 mm, e.g. equal to or greater than 1 mm, wherein the width of the gap is measured perpendicular to the length of the gap. If the gap runs perpendicular to the transport direction, then the width of the gap is measured in the transport direction. The width of the gap in the region of the levitation surface is less than 5 mm in one embodiment, since otherwise the object in the section arranged above the gap would be deformed too greatly due to its own mass (e.g. bent in the direction of the gap).Since the gap only partially intersects the levitation surface, the levitation surface has a web at least at one end of the gap (in the direction of the gap's length), via which the body sections of the vibration generator arranged in front of and behind the gap are connected to each other in the transport direction. Such a web (hereinafter also referred to as a connecting web) can also be arranged at both ends of the gap. The respective web forms a rigid connection between the body sections of the vibration generator and ensures the uniform oscillation of all body sections of the vibration generator, thus ensuring a reliable and uniform formation of the standing wave and thus the levitating transport of the object.In one embodiment, the connecting web can have a width (shortest dimension between the gap end and the edge of the vibration generator in the region of the levitation surface) of at least 20 mm (for example, at least 10% of the length of the gap defined above) along the levitation surface between the end of the gap and the edge of the vibration generator, so that a reliably rigid connection of the body sections of the vibration generator is effected.
[0017] In one embodiment, the width of the at least one gap of the vibration generator at the first gap end located on the levitation surface is smaller than the width of the gap at the second gap end, which is located on the side of the vibration generator opposite the levitation surface. This allows, on the one hand, the gap size in the region of the levitation surface to be kept small, so that the deformation of the object in the region of the gap is very small. On the other hand, such an approximately wedge-shaped design of the gap makes it possible to use different illumination and / or observation directions (i.e., the direction of the corresponding illumination or inspection axis) of the illumination device or the optical sensor, which are arranged on the side of the vibration generator facing away from the object, at a predetermined angle oblique to the levitation surface.In this embodiment, the gap is designed, for example, such that the gap has a trapezoidal shape in a cross-section along the transport direction of the object. The parallel base sides of the trapezoid form the opening / width of the gap in the region of the levitation surface and in the region of the side of the vibration generator facing away from the object, wherein the opening / width is smaller in the region of the levitation surface than in the region of the side of the vibration generator facing away from the object. As already partially explained above, the width of the gap in the region of the levitation surface is, for example, 0.5 mm < width (in the region of the levitation surface) < 10 mm, in particular 0.5 mm < width (in the region of the levitation surface) < 5 mm, in the region of the side of the vibration generator facing away from the object, for example, in the range 5 mm < width (on the side facing away from the object) < 25 mm.The dimension (thickness) of the vibration generator in a direction perpendicular to the levitation surface is, for example, in the range 5 mm < thickness < 30 mm.
[0018] In one embodiment, the levitation surface of the vibration generator is inclined by a maximum of 65°, for example, inclined by at least 15°, with respect to the direction of the gravitational force, such that the object is transported from the first end to the second end of the levitation surface continuously at this angle transverse to the direction of the gravitational force, wherein the transport device is provided at the lower end of the inclined levitation surface of the vibration generator. The optical sensor and the illumination device are arranged in one embodiment such that the inspection axis (optical axis) of the optical sensor and the illumination axis of the electromagnetic radiation of the illumination device are arranged correspondingly inclined to the direction of the gravitational force. The transport device can be designed as a conveyor belt.For example, the transport device comprises a conveyor belt or at least two conveyor belts, each with a belt surface running transversely to the levitation surface of the vibration generator and a belt surface moving circumferentially on the upper side in the transport direction, which belt surface runs, for example, perpendicular to the inclined levitation surface. When at least two conveyor belts are used, a first conveyor belt is arranged in the region between the first end of the levitation surface and the at least one gap, and a second conveyor belt is arranged in the region between the at least one gap and the second end of the levitation surface. If there are multiple gaps in the vibration generator, such a conveyor belt can also be arranged between two adjacent gaps.The conveyor belt enables simple and cost-effective movement of the object along the levitation surface such that the entire object is inspected by the inspection device. The object rests with its lower edge on the respective conveyor belt. The inclined arrangement of the object on the conveyor device prevents slippage during transport with the conveyor device and thus further increases the accuracy of the inspection. The use of several conveyor belts arranged on both sides of the respective gap is advantageous because in this case the illumination or observation of the object is not impaired by the conveyor belts. In one embodiment, the transport device, for example the conveyor belt, is arranged in a corresponding cutout, for example a lowered edge of the vibration generator.
[0019] In one embodiment, the inspection axis of the optical sensor or the illumination axis of the illumination device runs at an angle to the surface normal of the levitation surface that is greater than or equal to 5°. This is particularly advantageous when the properties of the object are to be analyzed with a single optical sensor not only in bright field but also in dark field.
[0020] In one embodiment, the elements of the inspection device explained above can be attached to a frame.
[0021] In one embodiment, a suction device is provided which sucks gas (e.g. air) out of the space between the underside of the object and the levitation surface essentially in the direction of the levitation surface. For this purpose, small openings (e.g. bores, diameter for example in the range 1 mm to 5 mm) can be provided in the vibration generator, which pass through the vibration generator in a direction perpendicular or oblique to the levitation surface and are in fluid communication with a suction pump for the gas (suction pressure for example in the range 1 mbar to 100 mbar). The suction direction thus runs approximately opposite to or at an angle to the levitation direction. By means of such a suction device, deformation due to the levitation movement can be prevented in objects with a particularly small thickness (thickness for example in the range 0.03 mm to 0.25 mm).
[0022] The above object is also achieved by a method for inspecting a web-shaped or plate-shaped object having a top side and a bottom side, wherein the device comprises a vibration generator and an optical sensor as well as a corresponding illumination device, wherein the vibration generator forms a flat levitation surface on a side facing the object, wherein the vibration generator is formed in one piece and has at least one continuous gap partially intersecting the levitation surface, with the following steps:
[0023] • Moving the object by means of a transport device from a first end to a second end of the levitation surface, wherein the oscillation frequency and the oscillation amplitude of the oscillation generator are adjusted such that the object can be moved in suspension substantially parallel to the levitation surface, and
[0024] • Inspecting the object by means of the illumination device and the optical sensor, which comprises directly inspecting the object through the gap by means of the optical sensor arranged on the side of the vibration generator facing away from the object and / or directly illuminating the object through the gap by means of the illumination device arranged on the side of the vibration generator facing away from the object.
[0025] The method has the advantages and embodiments explained above with respect to the device (each as a method), so that reference is made to the above discussion of the invention.
[0026] In particular, in one embodiment of the method, it is advantageous if the object is transported from the first end to the second end of the levitation surface transversely to the direction of the gravitational force over the levitation surface of the vibration generator, which is arranged inclined by a maximum of 65° with respect to the direction of the gravitational force, by means of the transport device provided at the lower end of the inclined levitation surface of the vibration generator.
[0027] In one embodiment of the method, the object is transported by means of the transport device, which comprises at least two transport belts, each with a belt surface running transversely to the levitation surface of the vibration generator, wherein a first transport belt is arranged in the region between the first end of the levitation surface and the at least one gap and a second transport belt is arranged in the region between the at least one gap and the second end of the levitation surface.
[0028] In one embodiment of the method, the object is inspected such that the inspection axis of the optical sensor or the illumination axis of the illumination device runs at an angle to the surface normal of the levitation surface that is greater than or equal to 5°.
[0029] In one embodiment of the method, the inspection includes an evaluation of the electromagnetic radiation recorded by the optical sensor and transmitted through the object and / or the electromagnetic radiation recorded by the optical sensor and reflected by the object, e.g. an evaluation of the electromagnetic radiation reflected or transmitted by bright field illumination or dark field illumination and received by the optical sensor with regard to the presence of defects and / or irregularities such as inclusions, scratches, contamination, etc. in the object at the respective location, e.g. on the surface or in the bulk.
[0030] In one embodiment of the method, the inspection includes bright field illumination and / or dark field illumination.
[0031] The electromagnetic radiation used for inspection is, for example, electromagnetic radiation from the visible wavelength range (wavelength in the range 380 nm to 780 nm) or from the infrared radiation range (wavelength greater than 780 nm) and / or from the UV radiation range (wavelength less than 380 nm). The electromagnetic radiation used in each case can contain individual sections of these wavelength ranges or combinations of several sections.
[0032] In one embodiment, the vibration generator comprises at least one material from the group comprising aluminum, aluminum alloy and glass or consists of at least one material from this group.
[0033] In one embodiment, as described above, gas (e.g., air) is sucked out of the space between the underside of the object and the levitation surface substantially in the direction of the levitation surface.
[0034] Further advantages, features, and possible applications of the present invention will become apparent from the following description of an exemplary embodiment and the drawings. All described and / or illustrated features, individually or in any combination, constitute the subject matter of the invention, regardless of their summary in the claims or their references.
[0035] They show schematically
[0036] Fig. 1 shows an embodiment of an inspection device according to the invention in a perspective view from the side,
[0037] Fig. 2 shows the embodiment according to Fig. 1 with an object in a perspective view from the side, Fig. 3 shows a schematic diagram of the embodiment according to Fig. 1 in a view from the front,
[0038] Fig. 4 shows the elements of the embodiment according to Fig. 1 necessary for the optical inspection of the object in a perspective view from the side,
[0039] Fig. 5 shows an enlarged section of Fig. 1 and
[0040] Fig. 6 shows an enlarged section of Fig. 3 in the area of the gap.
[0041] Figures 1 to 6 show an embodiment of an inspection device 1 according to the invention in various views and as a schematic diagram, which also illustrates the course of the electromagnetic radiation.
[0042] An optical sensor in the form of a line-scan camera (short: camera 11), as well as a first illumination device 21, a second illumination device 22, and a third illumination device 23 are attached to a frame 5 of the inspection device 1. Furthermore, a vibration generator (sonotrode 30) with a gap 31 is provided, over whose upper, flat levitation surface 33 an object (here, a thin glass pane 7) is transported from a first end 35 to a second end 36 of the levitation surface 33. The sonotrode 30 is mounted on aluminum profiles. The sonotrode 30 is formed in one piece, for example, as an aluminum block.
[0043] The sonotrode 30 is operated at a frequency of 30 to 40 kHz and an amplitude of 1 pm to 10 pm to transport the glass pane 7 with dimensions of 200 mm x 300 mm in a suspended manner from the first end 35 to the second end 36 of the levitation surface 33. The distance A (see Fig. 6) between the underside of the glass pane 7 and the levitation surface 33 is, for example, 20 pm to 100 pm. The aforementioned movement of the glass pane 7 is effected by conveyor belts 41, 42, which are arranged on both sides of the gap 31 of the sonotrode 30 in a recess 38 of the sonotrode. The glass pane 7 rests with its lower edge on the upper side of the respective conveyor belt 41, 42 and is thereby transported in the transport direction (arrow 40, see Figs. 2 and 3) by means of the respective conveyor belt 41, 42. Each conveyor belt 41 has a circumferential belt whose surface is made of plastic, for example.
[0044] The gap 31 arranged in the central region of the sonotrode 30 runs perpendicular to the transport direction (arrow 40) and extends from the levitation surface 33 through the entire sonotrode 30 to the side 34 of the sonotrode 30 facing away from the glass pane 7 (side 34 lies opposite the levitation surface 33). As a result, the third illumination device 23 arranged below the sonotrode (i.e. below the side 34 of the sonotrode 30 facing away from the glass pane 7) can directly illuminate the glass pane 7 through the gap 31 (see Figs. 3 and 6). However, the gap 31 does not intersect the levitation surface 33 across its entire width, as is shown in Figs.1, 2, 4, and 5, but the sections of the sonotrode 30 located in front of and behind the gap 31 in the transport direction are connected to one another by means of the rigid webs 37 and 39, so that the sections of the sonotrode 30 arranged in front of and behind the gap 31 oscillate at the same frequency, amplitude and phase. The standing wave above the levitation surface 33 therefore forms uniformly across the gap 31 and ensures that the glass pane 7 can be moved uniformly across the levitation surface 33 and does not deform in the region of the gap 31. The gap has, for example, a trapezoidal shape in cross-section shown in Fig. 6, which extends in the transport direction (arrow 40). In the area of the levitation surface 33, the gap has, for example, a width 31 b of 2 mm and in the area of the side opposite the glass pane 7 or the levitation surface 33, a width 31 B of, for example, 9 mm.Furthermore, the gap 31 has a dimension of, for example, L = 200 mm along its greatest extent (length) transverse to the transport direction. The length L of the gap 31 is generally greater than the width of the glass pane 7, which is measured transversely to the transport direction or on the upper side of the glass pane 7. The gap 31 has side surfaces extending at a predetermined angle, which allow the electromagnetic radiation generated by the lighting devices to impinge on the glass pane 7 at a small angle (e.g., at least 5°) to the normal on the underside of the glass pane 7.
[0045] The optical components of the inspection device 1 are arranged such that the first illumination device 21 generates electromagnetic radiation 21a, which directly illuminates a linear area of the upper side of the glass pane 7. The electromagnetic radiation 21 falls, for example, at an angle of 10° (see angle of the illumination axis 21b, measured with respect to the normal on the upper side of the glass pane 7). The electromagnetic radiation reflected by the glass pane 7 is reflected (along the beam 11a with the axis 11b) to the camera 11 and recorded by the camera 11 (bright field measurement).
[0046] Furthermore, the second illumination device 22 is arranged above the glass pane 7 and illuminates the glass pane 7 directly in a linear region along the beam 22a at a second angle of 10° (see angle of the illumination axis 22b). The camera 11 observes the glass pane 7 under dark-field conditions with respect to the latter illumination along the beam 11a with the axis 11b. Finally, the third illumination device 23 is arranged below the side 34 of the sonotrode 30. As already explained above, the third illumination device 23 illuminates the underside of the glass pane 7 in a linear region with electromagnetic radiation along the beam 23a with the illumination axis 23b.This radiation passes through the gap 31 directly to the underside of the glass pane 7, is at least partially transmitted through the glass pane, and after exiting the glass pane 7, is observed along the beam 11a by the camera 11. The electromagnetic radiation can, for example, contain radiation from the visible wavelength range, and the illumination devices 21, 22, 23 can be switched on sequentially and individually for a predetermined time, so that the camera 11 can successively record the resulting reflected or transmitted electromagnetic radiation and separate them from one another. The separation can also be achieved by means of the respective wavelength range of the electromagnetic radiation used (as described above).
[0047] The illumination devices 21, 22, 23 are each designed as line-shaped illumination devices that illuminate the glass pane 7 in a line-shaped area across its entire width. For this purpose, they each have, for example, an LED row. The camera 11 is designed, for example, as a line-scan camera that captures the reflected or transmitted electromagnetic radiation of the respectively illuminated line-shaped area across the entire width of the glass pane 7. Each pixel of the line-scan camera detects a color and / or brightness signal, which is then transmitted to a data processing device 50 for evaluation with regard to the presence of defects or contamination on the surface or in the volume of the glass pane 7.The data processing device 50 can combine the individually detected brightness and / or color values of the line-shaped regions of the glass pane 7 to form an image of the glass pane 7 and can correlate / coordinate the measured values with the movement of the glass pane 7 so that the location / area of any defects and / or contamination detected on / in the glass pane 7 can be determined.
[0048] As can be seen in particular from Figs. 1 and 2, the levitation surface 33 is arranged inclined to the direction of the gravitational force (perpendicular in Figs. 1 and 2). The levitation surface 33 forms an angle of α = 30 ° with the direction of the gravitational force, for example (cf. Fig. 1). The upper surface of the two conveyor belts 41, 42, on which the glass pane 7 rests with its lower edge, extends perpendicular to the levitation surface 33. The inclined arrangement and the described positioning of the conveyor belts 41, 42 prevent slippage between the glass pane 7 and the respective conveyor belt 41, 42. A gap 43 is formed between the conveyor belts 41, 42 in the region of the slot 31, which gap ensures that the conveyor belts 41, 42 do not hinder the optical inspection of the glass pane 7.
[0049] Overall, the inspection device described above allows for simple and accurate optical inspection of ultra-thin objects that can be moved relative to the optical components in such a way that they are not scratched or contaminated.
Claims
P a t e n t a n s p r ü c h e 1 . Device (1) for inspecting a web-shaped or plate-shaped object (7) having a top side and a bottom side, wherein the device (1) has a vibration generator (30) and an optical sensor (11) as well as a corresponding illumination device (21, 22, 23), wherein the vibration generator (30) forms a flat levitation surface (33) on a side facing the object (7), over which the object (7) can be moved from a first end (35) to a second end (36) by means of a transport device (41, 42), wherein the vibration frequency and the vibration amplitude of the vibration generator (30) can be adjusted such that the object (7) can be moved in suspension substantially parallel to the levitation surface, wherein the object (7) can be inspected by means of the illumination device (21, 22, 23) and the optical sensor (11), wherein the vibration generator (30) is formed in one piece and has at least one continuous,the levitation surface has a gap (31) partially intersecting it such that the object (7) can be inspected directly through the gap (31) by means of the optical sensor (11) arranged on the side (34) of the vibration generator (30) facing away from the object (7) and / or illuminated directly through the gap (31) by means of the lighting device (23) arranged on the side (34) of the vibration generator facing away from the object (7).
2. Device (1) according to claim 1, characterized in that the levitation surface (33) of the vibration generator (30) is arranged inclined by a maximum of 65° with respect to the direction of the gravitational force such that the transport of the object (7) from the first end (35) to the second end (36) of the levitation surface takes place transversely to the direction of the gravitational force, wherein the transport device (41, 42) is provided at the lower end of the inclined levitation surface of the vibration generator (30).
3. Device (1) according to one of the preceding claims, characterized in that the transport device comprises at least two conveyor belts, each with a belt surface running transversely to the levitation surface of the vibration generator (30), wherein a first conveyor belt (41) is arranged in the region between the first end (35) of the levitation surface (33) and the at least one gap (31) and a second conveyor belt (42) is arranged in the region between the at least one gap (31) and the second end (36) of the levitation surface (33).
4. Device (1) according to one of the preceding claims, characterized in that the width (31 b) of the at least one gap (31) of the vibration generator (30) at the first gap end located on the levitation surface (33) is smaller than the width (31 B) of the respective gap (31) at the second gap end, which is located on the side (34) of the vibration generator (30) facing away from the object (7).
5. Device (1) according to one of the preceding claims, characterized in that the gap (31) has a trapezoidal shape in a cross section along the transport direction of the object (7).
6. Device (1) according to one of the preceding claims, characterized in that the inspection axis (11 b) of the optical sensor (11) or the illumination axis (21 b, 23b) of the illumination device (21, 23) runs at an angle to the surface normal of the levitation surface (33) which is greater than or equal to 5 °.
7. Device (1) according to one of the preceding claims, characterized in that the optical sensor (11) is a line camera and / or the illumination device (21, 22, 23) is a line-shaped illumination device.
8. Device (1) according to one of the preceding claims, characterized in that a suction device is provided which sucks gas from the space between the underside of the object (7) and the levitation surface (33) substantially in the direction of the levitation surface.
9. A method for inspecting a web-shaped or plate-shaped object (7) having a top side and a bottom side, wherein the device (1) has a vibration generator (30) and an optical sensor (11) as well as a corresponding illumination device (21, 22, 23), wherein the vibration generator (30) forms a flat levitation surface (33) on a side facing the object (7), wherein the vibration generator (30) is formed in one piece and has at least one continuous gap (31) partially intersecting the levitation surface, comprising the following steps: • Moving the object (7) by means of a transport device from a first end (35) to a second end (36) of the levitation surface, wherein the oscillation frequency and the oscillation amplitude of the oscillation generator (30) are adjusted such that the object (7) can be moved in suspension substantially parallel to the levitation surface, and • Inspecting the object (7) by means of the illumination device (21, 22, 23) and the optical sensor (11), which comprises a direct inspection of the object (7) through the gap (31) by means of the optical sensor (11) arranged on the side (34) of the vibration generator (30) facing away from the object (7) and / or a direct illumination of the object (7) through the gap (31) by means of the illumination device (23) arranged on the side (34) of the vibration generator (30) facing away from the object (7).
10. The method according to claim 9, wherein the object (7) is transported from the first end (35) to the second end (36) of the levitation surface (33) transversely to the direction of the gravitational force over the levitation surface of the vibration generator (30), which is arranged inclined by a maximum of 65° with respect to the direction of the gravitational force, by means of the transport device (41, 42) provided at the lower end of the inclined levitation surface of the vibration generator (30).
11. Method according to one of claims 9 and 10, characterized in that the transporting takes place by means of the transport device which comprises at least two conveyor belts, each with a belt surface running transversely to the levitation surface of the vibration generator (30), wherein a first conveyor belt (41) is arranged in the region between the first end (35) of the levitation surface (33) and the at least one gap (31) and a second conveyor belt (42) is arranged in the region between the at least one gap (31) and the second end (36) of the levitation surface (33).
12. Method according to one of claims 9 to 11, characterized in that the object (7) is inspected such that the inspection axis (11 b) of the optical sensor (11) or the illumination axis (21 b, 23 b) of the illumination device (21, 23) runs at an angle to the surface normal of the levitation surface which is greater than or equal to 5 °.
13. Method according to one of claims 9 to 12, characterized in that the inspection includes an evaluation of the recorded electromagnetic radiation transmitted by the object (7) and / or the recorded electromagnetic radiation reflected by the object (7).
14. Method according to one of claims 9 to 13, characterized in that the inspection includes bright field illumination and / or dark field illumination.
15. Method according to one of claims 9 to 14, characterized in that gas is sucked out of the space between the underside of the object (7) and the levitation surface (33) substantially in the direction of the levitation surface.