Device for inspecting flat or web-shaped objects

Abstract

The invention relates to a device (1) and to a corresponding method for inspecting web-shaped or flat-plate-shaped objects (7) having a top side and a bottom side. In order to avoid contamination or mechanical damage to the object while enabling precise optical inspection of the object, the device comprises a vibration generator (30) and an optical sensor (11) and, if necessary, further comprises a corresponding illumination device (21, 22, 23), in which the vibration generator forms a planar floating surface (33) on the side facing the object, the vibration generator has a planar suspension surface on which the object can be moved from a first end (35) to a second end (36) by means of a conveying device (41, 42), the vibration frequency and the vibration amplitude of the vibration generator being adjustable such that the object can be moved in a suspension substantially parallel to the suspension surface, the vibration generator is formed as a single piece and has at least one through gap partially cut through the suspension surface such that the object can be directly inspected by means of an optical sensor arranged on a side (34) of the vibration generator facing away from the object or by means of an irradiation device (23) arranged on a side (34) of the vibration generator facing away from the object.

Description

describe

[0001] The invention relates to a device for inspecting flat or web-shaped objects having a top side and a bottom side (eg thin glass plates, thin plastic films, wafers, etc.) by means of an optical sensor.

[0002] For inspection, thin, flat or web-shaped objects are typically transported on a conveyor belt and illuminated from the top and / or bottom using an illumination device. Optical sensors (e.g., cameras) capture the electromagnetic radiation transmitted and / or reflected by the object. Based on these measurements, the object's quality can be assessed and / or its dimensions determined.

[0003] Ultra-thin, flat or web-shaped objects, such as glass sheets or plastic films used in mobile phones, can be easily damaged or contaminated during transport if the bottom side of the object rests on a conveyor belt. To prevent this, an ultrasonic oscillator (sonotrode) with a sound-emitting surface facing the object can be used. For example, documents WO 2015 / 010681 A2 and WO 2009 / 056127 A2 describe such ultrasonic oscillators. The inspection device disclosed in WO 2009 / 056127 A2 includes a vibration generator with a carrier body made of a translucent material. This allows the bottom side of the inspected material to be observed through the carrier body using an optical sensor positioned below. However, this process is not advantageous for ultra-thin, flat or web-shaped objects because the carrier body can affect the measurement results and reduce their accuracy.

[0004] The object of the present invention is therefore to create a device or to specify a method which enables precise optical inspection of thin, flat or web-shaped objects while avoiding mechanical damage or contamination.

[0005] This object is achieved by a device having the features of claim 1 and a method having the features of claim 9 .

[0006] In particular, this object is achieved by a device for inspecting a web-shaped or flat-plate-shaped object having a top side and a bottom side, the device comprising a vibration generator and an optical sensor, and corresponding illumination means. The vibration generator forms a planar levitation surface on a side facing the object, and the object can be moved on this planar levitation surface from a first end to a second end by means of a conveying device. The vibration frequency and amplitude of the vibration generator can be adjusted so that the object is substantially parallel to the levitation surface and can be moved in levitation substantially parallel to the levitation surface. The object can be inspected by means of the illumination means and the optical sensor. The vibration generator is formed as a single piece and includes at least one through-gap partially cut through the levitation surface, so 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 can be illuminated directly through the gap by means of the illumination means arranged on the side of the vibration generator facing away from the object. In the first case, electromagnetic radiation reflected or transmitted by the object passes through the gap to the optical sensor, which receives the corresponding electromagnetic radiation. In the second case, electromagnetic radiation generated by the illumination means passes through the gap to the object.

[0007] The web-shaped or flat object to be inspected can be a thin or ultrathin glass sheet (e.g., for mobile phones), a wafer, a microchip, or a film. The object can be made at least partially transparent to electromagnetic radiation. The two opposing, largest sides of the object are referred to as the top and bottom sides, with the side of the object facing the vibration generator forming the bottom side and the opposite side of the object forming the top side. The thickness of such an object, measured between the top and bottom sides, can range from 0.03 mm to 1 mm, for example.

[0008] The vibration generator (also known as an ultrasonic oscillator) is designed to form a planar levitation surface. For example, the vibration generator can have a rectangular or cuboid shape. The object's bottom side faces the levitation surface and is transported along the levitation surface from a first end to a second end. Hereinafter, the transport direction along the levitation surface will be referred to as the transport direction. The vibration frequency and amplitude of the vibration generator can be adjusted to generate a standing pressure wave (stationary wave) in the air film disposed beneath the object, causing the object to float substantially parallel to the levitation surface and thereby move in the transport direction with the aid of the transport device. For example, the dimensions of the vibration generator are in the range of 0.4 to 3 meters in length and 10 to 40 cm in width, wherein, for example, the size of the levitation surface is in the range of 400 to 12,000 cm². The frequency of the vibration generator is, for example, in the range of 10 kHz to 50 kHz, particularly in the range of 30 to 40 kHz, and the amplitude is, for example, in the range of 1 μm to 50 μm. The vibration generator can for example be attached to a profile element (for example an aluminum profile element) for optimal generation of vibrations in such a way that it is attached to the respective profile element (for example by means of screws) only at the nodes of the vibration of the vibration generator.

[0009] Optical sensors, such as high-resolution line scan or matrix cameras, are used for optical inspection of objects to observe electromagnetic radiation reflected and / or transmitted by the object in brightfield or darkfield. The illumination device can be designed as a linear or matrix-shaped illumination device, for example, a line or matrix comprising a large number of LEDs. The object is illuminated in a predetermined area by means of the illumination device, wherein the illumination device generates electromagnetic radiation within a wavelength range suitable for the respective inspection. In one embodiment, the optical sensor is positioned above the top side of the object. To inspect the object's transmissive properties, the illumination device is positioned on the side of the vibration generator facing away from the object and illuminates the object's bottom side through a gap. Alternatively, conversely, the illumination device for illuminating the object's top side can be positioned above the object, and the optical sensor positioned below the side of the vibration generator facing away from the object. To inspect the reflective properties of the object's bottom side, 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 bottom of the object. Electromagnetic radiation reflected by the object then also passes through the gap directly to the optical sensor. Similarly, an optical sensor and an illumination device can be positioned above the top side of an object to examine the object's top side in reflection. Combinations of the aforementioned illumination and capture configurations for transmitted and / or reflected electromagnetic radiation are particularly advantageous. Furthermore, the illumination angles of the illumination devices can be adjusted and varied accordingly to allow analysis of the object's brightfield or darkfield properties. For example, a single optical sensor can be positioned above the object's top side, while at least one illumination device is positioned above the object's top side, and at least one illumination device is positioned below the side of the vibration generator facing away from the object. This allows the optical sensor to observe both reflection and transmission of electromagnetic radiation, for example, in brightfield. Using a second illumination device, also positioned above the object's top side at a different angle than the first illumination device, darkfield reflection can also be measured. In such configurations with two or more illumination devices and a single associated optical sensor (which captures the signals generated by the several illumination devices (and the object)), the signals are advantageously separated in time and / or wavelength. With temporal separation, the illumination devices can be switched on and off sequentially over time, so that only a single illumination device provides illumination at any given time. The signals captured by the optical sensors can be assigned to corresponding illumination signals, since they are generated directly in transmission and reflection on the object based on their measurement cycles. Additionally or alternatively, the illumination can occur in different wavelength ranges, so that the signals captured by the optical sensors can be differentiated relative to the respective wavelength ranges. For example, a first illumination device can generate electromagnetic radiation in the wavelength range of 400 nm to 500 nm for illumination with visible blue-green colors, and a second illumination device can generate electromagnetic radiation in the wavelength range of 600 nm to 700 nm for illumination with visible red colors.

[0010] The position and orientation of the optical sensor and the at least one illumination device in the surrounding space, in particular relative to the reflective surface, are known. The position and orientation of the optical sensor can be determined using known calibration methods.

[0011] An optical sensor, in the form of a line scan or matrix camera, determines the brightness and / or color values ​​for each pixel of the object's observed area. In one embodiment, the color and / or brightness values ​​of all regions of the object can be combined to form an image. The color and / or brightness values ​​can be forwarded to a data processing unit, where they are analyzed for defects and / or contamination. In one embodiment, the object can be inspected over its entire top and / or bottom side by moving the object along the suspended surface and thus transversely to the optical sensor, which is fixed relative to the suspended surface at least during inspection. Alternatively, a certain proportion of the object's top and / or bottom side can be analyzed.

[0012] 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, image data is transmitted from the camera to the data processing unit via wired or wireless communication. The data processing unit includes a processor, an instruction control unit, an arithmetic unit, and a logic unit. The processor is the functional module that interprets and executes the instructions / commands of the algorithm. Processors can include at least microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs—digital integrated circuits into which logic circuits can be programmed), discrete logic circuits, and any combination of these. The data processing unit may also include a memory module, an input module (such as a keyboard or touchpad), a power module (such as a battery), and a display module (such as a monitor). The data processing unit can be implemented as a real hardware resource, such as a smartphone, desktop computer, server, laptop, cluster / warehouse-scale computer, embedded system, etc., or as a virtualized computer resource. The data processing unit may also include a transmitter / receiver (transceiver) for exchanging data with the optical sensor.

[0013] Using optical data (e.g., intensity and / or color data) detected by optical sensors regarding electromagnetic radiation transmitted and / or reflected by an object in brightfield and / or darkfield conditions, contamination and / or defects can be detected during inspection and assigned to specific locations or areas of the object. Examples of contamination and / or defects include particles, scratches, stains / discolorations, protrusions, indentations, dents, bubbles, material compactions, burrs, rings, etc., located on the top and / or bottom sides of the object or within the object's bulk. Such contamination and / or defects are detected, for example, by changes in the contrast and / or brightness of the reflected and / or transmitted electromagnetic radiation. To this end, the signals captured and possibly digitized by the optical sensors are transmitted to a corresponding data processing unit for evaluation and determination of the contamination and / or defect. Based on the object's transport speed and the known positions of the illumination device and the optical sensor arrangement, the location or area of ​​the detected defect and / or contamination can also be determined from the signals captured by the optical sensors and the associated measurement times. Contamination and / or defects can also be detected, for example, by measuring the deflection or changes in the deflection of electromagnetic radiation reflected and / or transmitted by the object's material. This is possible, for example, using the method described in more detail in document EP 2 390 656 B1. The content of the method described therein is incorporated herein by reference.

[0014] According to the present invention, the vibration generator is formed as a single piece and includes at least one through-gap partially cut through the levitation surface. This allows the object to be directly inspected through the gap by an optical sensor disposed on the side of the vibration generator facing away from the object and / or to be directly illuminated through the gap by an illumination device disposed on the side of the vibration generator facing away from the object. Thus, the gap allows the transmission or reflection properties of the object's underside to be directly determined, with electromagnetic radiation transmitted or reflected by the object passing directly through the gap to the optical sensor. Illumination of the object's underside by the illumination device disposed on the side of the vibration generator facing away from the object is also provided directly through the gap. This prevents signal distortion by another material (e.g., the material of the vibration generator), thereby improving the accuracy of optical inspection. Furthermore, the single-piece form of the vibration generator ensures that it vibrates identically on both sides of the gap, generating a uniform standing wave (stationary wave) that induces levitation across the entire levitation surface. This ensures reliable levitation of the object, counteracting mechanical damage or contamination of sensitive objects. The single-piece form of the vibration generator also avoids time-consuming adjustments that would be necessary if two separate ultrasonic oscillators were used. Furthermore, the one-piece form of the vibration generator ensures that the vibrations are in phase over the entire surface of the vibration generator.The distance between the bottom side of the object caused by levitation and the levitation surface is, for example, 20 μm to 100 μm.

[0015] In one embodiment, the vibration generator may include a single such gap, or the vibration generator may include two or more such gaps, wherein in one embodiment, at least two gaps extend parallel to each other or at a predetermined angle. At least one gap may include a rounded edge at its leading edge in the conveying direction, which is advantageous because it prevents objects that may sag from getting stuck in the gap during conveyance.

[0016] The gap is formed such that it passes through the vibration generator and partially cuts through the levitated surface, allowing electromagnetic radiation to pass through the gap on its way from the illumination device to the object or from the object to the optical sensor (depending on the device configuration). The illumination device and / or the optical sensor are thus oriented such that electromagnetic radiation is transmitted from the illumination device to the object via the gap, or from the object to the optical sensor via the gap. The gap can be formed, for example, as a slit, so that only a linear region of the object is illuminated, or reflected or transmitted electromagnetic radiation is recorded by a linear region of the object. For example, the gap extends across the levitated surface in its largest dimension (referred to as the length) transversely (e.g., perpendicularly) to the direction of transport of the object. 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 levitated surface is equal to or greater than 10 cm. For example, the width of the gap in the region of the levitated surface is equal to or greater than 0.5 mm, for example, equal to or greater than 1 mm, where the width of the gap is measured perpendicular to the length of the gap. If the gap extends perpendicular to the transport direction, the width of the gap is measured in the transport direction. In one embodiment, the width of the gap in the area of ​​the levitation surface is less than 5 mm. Otherwise, the section of the object located above the gap would deform excessively due to its own mass (e.g., bend in the direction of the gap). Because the gap only partially cuts through the levitation surface, the levitation surface includes a web at at least one end of the gap (in the longitudinal direction of the gap), connecting the main body sections of the vibration generator, which are arranged in front and behind the gap in the transmission direction, via this web. Such a web (hereinafter also referred to as a bridging web / connecting web) can also be arranged at both ends of the gap. The corresponding web forms a rigid connection between the main body sections of the vibration generator and ensures that all main body sections of the vibration generator vibrate in the same manner, thereby ensuring reliable and uniform formation of standing waves and, therefore, ensuring transmission of the object. In one embodiment, the connecting web can have a width along the levitation surface (the shortest dimension between the end of the gap and the edge of the vibration generator in the area of ​​the levitation surface) of at least 20 mm (e.g., at least 10% of the gap length defined above), thereby achieving a reliable and rigid connection between the main body sections of the vibration generator.

[0017] In one embodiment, the width of at least one gap in the vibration generator at a first gap end located at the levitation surface is smaller than the gap width at a second gap end located on the side of the vibration generator opposite the levitation surface. This keeps the gap size small in the levitation surface region, minimizing deformation of the object in the gap region. Furthermore, this approximately wedge-shaped design of the gap enables, for example, the use of different illumination and / or viewing directions (i.e., directions of corresponding illumination or inspection axes) of an illumination device or optical sensor positioned on the side of the vibration generator facing away from the object, at predetermined angles relative to the levitation surface. For example, in this embodiment, the gap is formed such that its cross-section along the object's transport direction comprises a trapezoidal shape. The parallel base sides of the trapezoid define the gap's opening / width in the levitation surface region and in the region of the vibration generator facing away from the object, with the opening / width in the levitation surface region being smaller than the opening / width in the region of the vibration generator facing away from the object. As partially explained above, for example, the width of the gap in the area of ​​the levitation surface is 0.5 mm ≤ width (in the area of ​​the levitation surface) ≤ 10 mm, specifically 0.5 mm ≤ width (in the area of ​​the levitation surface) ≤ 5 mm. For example, the width of the gap in the area of ​​the vibration generator facing away from the object is within the range of 5 mm ≤ width (on the side facing away from the object) ≤ 25 mm. For example, the dimension (thickness) of the vibration generator in a direction perpendicular to the levitation surface is within the range of 5 mm ≤ thickness ≤ 30 mm.

[0018] In one embodiment, the vibration generator's levitation surface is arranged to be tilted by a maximum of 65°, for example, by at least 15°, relative to the direction of gravity, such that the object is conveyed continuously from a first end to a second end of the levitation surface at this angle transverse to the direction of gravity. The conveying device is disposed at the lower end of the vibration generator's tilted levitation surface. In one embodiment, the optical sensor and the illumination device are arranged such that the inspection axis (optical axis) of the optical sensor and the illumination axis of the electromagnetic radiation of the illumination device are respectively tilted relative to the direction of gravity. The conveying device can be formed as a conveyor belt. For example, the conveyor device includes a conveyor belt or at least two conveyor belts, each having a belt surface extending transverse to the vibration generator's levitation surface and a circumferential belt surface that moves on the top side in the conveying direction (e.g., extending perpendicular to the tilted levitation surface). When at least two conveyor belts are used, the first conveyor belt is disposed in the region between the first end of the levitation surface and the at least one gap, and the second conveyor belt is disposed in the region between the at least one gap and the second end of the levitation surface. If multiple gaps are present in the vibration generator, such a conveyor belt can also be disposed between two adjacent gaps. Conveyor belts enable simple and cost-effective movement of objects along a suspended surface, allowing the entire object to be inspected by the inspection device. The lower edge of the object rests on the corresponding conveyor belt. The angled arrangement of the object on the conveyor prevents slippage during transport, further improving inspection accuracy. The use of multiple conveyor belts arranged on either side of a corresponding gap is advantageous because, in this case, illumination or observation of the object is not impaired by the conveyor belts. In one embodiment, the conveyor device (e.g., conveyor belt) is arranged in the corresponding cutout (e.g., the lower edge of the vibration generator).

[0019] In one embodiment, the inspection axis of the optical sensor or the illumination axis of the illumination device extends at an angle of greater than or equal to 5° to the surface normal of the suspended surface. This is particularly advantageous if properties of an object are to be analyzed with a single optical sensor both in bright field and in dark field.

[0020] In one embodiment, the elements of the inspection device described above may be attached to a frame.

[0021] In one embodiment, a suction device is provided that extracts gas (e.g., air) from the space between the bottom side of the object and the levitation surface, essentially in the direction of the levitation surface. To this end, a small through-opening (e.g., a hole with a diameter in the range of 1 mm to 5 mm) can be provided in the vibration generator, extending perpendicularly or obliquely to the levitation surface, and fluidically connected to a suction pump for the gas (e.g., with a suction pressure in the range of 1 mbar to 100 mbar). The suction direction thus extends generally opposite to the levitation direction or at an angle relative thereto. This type of suction device can be used to prevent deformation caused by levitation movement in the case of objects with particularly low thickness (e.g., thickness in the range of 0.03 mm to 0.25 mm).

[0022] The above object is also solved 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 and corresponding illumination means, wherein the vibration generator forms a planar floating surface on a side facing the object, wherein the vibration generator is formed in one piece and comprises at least one through-gap partially cut through the floating surface, the method comprising the following steps: - moving the object from a first end of the levitation surface to a second end of the levitation surface by means of the conveying device, wherein the vibration frequency and the vibration amplitude of the vibration generator are set so that the object can be moved in levitation substantially parallel to the levitation surface, and - inspecting the object with the aid of an illumination device and an optical sensor, which includes directly inspecting the object through a gap with the aid of an optical sensor arranged on the side of the vibration generator facing away from the object and / or directly illuminating the object through the gap with the aid of an illumination device arranged on the side of the vibration generator facing away from the object.

[0023] The method comprises the advantages and embodiments explained above with respect to the apparatus (each acting on the method), so reference is made to the above discussion of the invention.

[0024] In particular, in one embodiment of the method, it is advantageous if the object is conveyed transversely to the direction of gravity from a first end of the levitation surface to a second end of the levitation surface via the levitation surface of the vibration generator (arranged at an inclination of at most 65° relative to the direction of gravity) by means of a conveying device arranged at the lower end of the inclined levitation surface of the vibration generator.

[0025] In one embodiment of the method, the objects are conveyed by means of a conveying device comprising at least two conveyor belts, each conveyor belt having a belt surface extending transversely to the suspension surface of the vibration generator, wherein a first conveyor belt is arranged in a region between a first end of the suspension surface and at least one gap, and a second conveyor belt is arranged in a region between the at least one gap and a second end of the suspension surface.

[0026] In one embodiment of the method, the object is inspected such that an inspection axis of the optical sensor or an illumination axis of the illumination device extends at an angle greater than or equal to 5° to a surface normal of the suspended surface.

[0027] In one embodiment of the method, the inspection includes evaluating electromagnetic radiation captured by the optical sensor and transmitted through the object and / or electromagnetic radiation captured by the optical sensor and reflected from the object, for example, evaluating electromagnetic radiation reflected or transmitted by bright field illumination or dark field illumination and received by the optical sensor regarding the presence of defects and / or irregularities, such as inclusions, scratches, contamination, etc., present at corresponding locations in the object (i.e., on the surface or in the body).

[0028] In one embodiment of the method, the inspecting comprises bright field illumination and / or dark field illumination.

[0029] For example, the electromagnetic radiation used for the examination is electromagnetic radiation from the visible wavelength range (wavelength in the range of 380 nm to 780 nm), 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 a combination of several sections.

[0030] In one embodiment, the vibration generator includes or consists of at least one material from the group consisting of aluminum, aluminum alloy, and glass.

[0031] In one embodiment, as described above, gas (eg, air) is exhausted from the space between the bottom side of the object and the levitation surface substantially in the direction of the levitation surface.

[0032] Other advantages, features and possible applications of the present invention are also apparent from the following description of embodiments and the accompanying drawings. All features described and / or illustrated form the object of the present invention individually or in any combination, even independently of their summary in the claims or their references.

[0033] The following schematically shows: Figure 1 is a perspective side view of an embodiment of an inspection device according to the present invention; Figure 2 Is based on an object Figure 1 A perspective side view of an embodiment of the invention; Figure 3 is based on Figure 1 A front view of a schematic diagram of a principle embodiment of the present invention; Figure 4 is based on Figure 1 A perspective side view of the elements necessary for optical inspection of an object of an embodiment; Figure 5 yes Figure 1 an amplified section of Figure 6 is in the gap area Figure 3 The enlarged section.

[0034] Figures 1 to 6 An embodiment of an inspection device 1 according to the invention is shown in various views and schematic diagrams, which also illustrate electromagnetic radiation paths.

[0035] An optical sensor in the form of a line scan camera (camera 11 for short) and first, second, and third illumination devices 21, 22, and 23 are attached to the frame 5 of the inspection device 1. Furthermore, a vibration generator (ultrasonic oscillator 30) is provided with a gap 31, and an object (here, a thin glass plate 7) is conveyed over the vibration generator's top planar levitation surface 33 from a first end 35 to a second end 36 of the levitation surface 33. The ultrasonic oscillator 30 is mounted on an aluminum profile. The ultrasonic oscillator 30 is formed as a single piece, for example, as an aluminum block.

[0036] The ultrasonic oscillator 30 is operated at a frequency of 30 kHz to 40 kHz and an amplitude of 1 μm to 10 μm to transport the glass plate 7 having a size of 200 mm×300 mm from the first end 35 to the second end 36 of the suspension surface 33 in a floating manner. The distance A between the bottom side of the glass plate 7 and the suspension surface 33 (refer to Figure 6 ) is, for example, 20 μm to 100 μm. The above-mentioned movement of the glass plate 7 is achieved by conveyor belts 41, 42, which are arranged on both sides of the gap 31 of the ultrasonic oscillator 30 and in the groove 38 of the ultrasonic oscillator. The glass plate 7 rests with its lower edge on the top side of the corresponding conveyor belt 41, 42 and is moved in the conveying direction (arrow 40, see Figure 2 and Figure 3 Each conveyor belt 41 comprises a circumferential belt, the surface of which is formed of, for example, a plastic material.

[0037] The gap 31 arranged in the central region of the ultrasonic oscillator 30 extends perpendicularly to the conveying direction (arrow 40) and extends from the suspension surface 33 through the entire ultrasonic oscillator 30 to the side 34 of the ultrasonic oscillator 30 facing away from the glass sheet 7 (this side 34 is opposite to the suspension surface 33). Therefore, the third irradiation device 23 arranged below the ultrasonic oscillator (i.e., below the side 34 of the ultrasonic oscillator 30 facing away from the glass sheet 7) can directly irradiate the glass sheet 7 through the gap 31 (see Figure 3 and Figure 6 ). However, from Figure 1 、 Figure 2 、 Figure 4 and Figure 5It can be seen that the gap 31 does not cut through the entire width of the suspension surface 33, but the sections of the ultrasonic oscillator 30 located in front of and behind the gap 31 in the transmission direction are connected to each other by means of rigid webs 37 and 39, so that the sections of the ultrasonic oscillator 30 located in front of and behind the gap 31 oscillate with the same frequency, amplitude, and phase. As a result, the standing wave above the suspension surface 33 is formed uniformly across the gap 31, ensuring that the glass sheet 7 can move uniformly across the suspension surface 33 and does not deform in the area of ​​the gap 31. For example, the gap has a trapezoidal cross-section, such as Figure 6 As shown, this trapezoidal shape extends in the conveying direction (arrow 40). In the region of the suspension surface 33, the gap comprises a width 31b of, for example, 2 mm, and in the region of the side opposite the glass sheet 7 or the suspension surface 33, the gap comprises a width 31B of, for example, 9 mm. Furthermore, the gap 31 has, for example, a dimension L = 200 mm along its major dimension (length) transverse to the conveying direction. The length L of the gap 31 is typically greater than the width of the glass sheet 7, measured transverse to the conveying direction or on the top side of the glass sheet 7. The gap 31 includes side surfaces extending at a predetermined angle, which allows the electromagnetic radiation generated by the illumination device to impinge on the glass sheet 7 at a small angle (e.g., at least 5°) relative to the normal on the bottom side of the glass sheet 7.

[0038] The optical components of the inspection device 1 are arranged so that a first illumination device 21 generates electromagnetic radiation 21a that directly illuminates a linear area on the top side of the glass sheet 7. The electromagnetic radiation 21 falls, for example, at an angle of 10° (see angle of illumination axis 21b, measured relative to the normal on the top side of the glass sheet 7). The electromagnetic radiation reflected by the glass sheet 7 (along a beam 11a having an axis 11b) is reflected to the camera 11 and recorded by the camera 11 (bright-field measurement).

[0039] Furthermore, a second illumination device 22 is arranged above the glass sheet 7 and directly illuminates the glass sheet 7 in a linear region along a beam 22a at a second angle of 10° (see angle of illumination axis 22b). Based on the aforementioned illumination, the camera 11 observes the glass sheet 7 under dark-field conditions along the beam 11a having an axis 11b. Finally, a third illumination device 23 is arranged below one side 34 of the ultrasonic oscillator 30. As described above, the third illumination device 23 illuminates the bottom side of the glass sheet 7 in a linear region along a beam 23a having an illumination axis 23b. This radiation passes through the gap 31 directly onto the bottom side of the glass sheet 7, is at least partially transmitted through the glass sheet, and is observed by the camera 11 along the beam 11a after exiting the glass sheet 7. The electromagnetic radiation can each include, for example, radiation from the visible wavelength range, and the illumination devices 21, 22, and 23 can be switched on sequentially and individually for predetermined periods of time, so that the camera 11 can continuously record the resulting reflected or transmitted electromagnetic radiation and separate them from one another. Separation can also be achieved (as described above) by means of a corresponding wavelength range of the electromagnetic radiation used.

[0040] Illumination devices 21, 22, and 23 are each designed as a linear illumination device that illuminates glass sheet 7 in a linear region across the entire width of glass sheet 7. To this end, they each comprise, for example, a row of LEDs. Camera 11 is designed, for example, as a line scan camera that captures reflected or transmitted electromagnetic radiation from the respective illuminated linear region across the entire width of glass sheet 7. Each pixel of the line scan camera detects a color and / or brightness signal, which is then transmitted to data processing unit 50 for evaluation regarding the presence of defects or contamination on the surface or in the volume of glass sheet 7. Data processing unit 50 can combine the individually captured brightness and / or color values ​​of the linear regions of glass sheet 7 to form an image of glass sheet 7 and can correlate / coordinate the measured values ​​with the movement of glass sheet 7, so that the location / region of any detected defects and / or contamination on / in glass sheet 7 can be determined.

[0041] Especially from Figure 1 and Figure 2 It can be seen that the direction of the levitation surface 33 relative to the gravity (in Figure 1 and Figure 2 For example, the levitation surface 33 forms an angle of a=30° with the direction of gravity (see Figure 1The upper surfaces of the two conveyor belts 41, 42 extend perpendicular to the suspension surface 33, and the glass sheet 7 rests with its lower edge on the upper surfaces of the two conveyor belts 41, 42. The inclined arrangement and positioning of the conveyor belts 41, 42 prevent slippage between the glass sheet 7 and the respective conveyor belts 41, 42. A gap 43 is formed between the conveyor belts 41, 42 in the area of ​​the trough 31, ensuring that the conveyor belts 41, 42 do not obstruct optical inspection of the glass sheet 7.

[0042] In summary, the above-described inspection apparatus allows for easy and accurate optical inspection of ultra-thin objects, which can be moved relative to the optical components such that the ultra-thin objects will not be scratched or contaminated.

Claims

1. A device (1) for inspecting a web-shaped or flat-plate-shaped object (7), the web-shaped or flat-plate-shaped object (7) having a top side and a bottom side, wherein the device (1) comprises a vibration generator (30) and an optical sensor (11) and corresponding illumination devices (21, 22, 23), wherein the vibration generator (30) forms a planar levitation surface (33) on the side facing the object (7), the object (7) being movable from a first end (35) to a second end (36) by means of a conveying device (41, 42), wherein the vibration frequency and the vibration amplitude of the vibration generator (30) are adjustable so that the object (7) can be levitated 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 as a single piece and comprises at least one through-gap (31) partially cut through the suspension surface, so that the object (7) can be inspected directly through the gap (31) by means of the optical sensor (11) arranged on a side (34) of the vibration generator (30) facing away from the object (7), and / or can be directly illuminated through the gap (31) by means of the illumination device (23) arranged on a side (34) of the vibration generator (30) facing away from the object (7).

2. The device (1) according to claim 1, characterized in that The suspension surface (33) of the vibration generator (30) is arranged to be inclined at a maximum of 65° relative to the direction of gravity, so that the object (7) is transferred from the first end (35) of the suspension surface to the second end (36) of the suspension surface transversely to the direction of gravity, wherein the transfer device (41, 42) is provided at the lower end of the inclined suspension surface of the vibration generator (30).

3. The device (1) according to any one of the preceding claims, characterized in that The conveying device comprises at least two conveyor belts, each conveyor belt having a belt surface extending transversely to the suspension surface of the vibration generator (30), wherein a first conveyor belt (41) is arranged in a region between the first end (35) of the suspension surface (33) and the at least one gap (31), and a second conveyor belt (42) is arranged in a region between the at least one gap (31) and the second end (36) of the suspension surface (33).

4. The device (1) according to any one of the preceding claims, characterized in that The width (31b) of at least one gap (31) of the vibration generator (30) at a first gap end located on the suspension surface (33) is smaller than the width (31B) of the corresponding gap (31) at a second gap end located on a side (34) of the vibration generator (30) facing away from the object (7).

5. Device (1) according to any one of the preceding claims, characterized in that The cross section of the gap (31) along the conveying direction of the object (7) comprises a trapezoidal shape.

6. Device (1) according to any one of the preceding claims, characterized in that The inspection axis (11b) of the optical sensor (11) or the illumination axis (21b, 23b) of the illumination device (21, 23) extends at an angle greater than or equal to 5° to the surface normal of the suspension surface (33).

7. Device (1) according to any one of the preceding claims, characterized in that The optical sensor (11) is a line scan camera and / or the illumination device (21, 22, 23) is a linear illumination device.

8. Device (1) according to any one of the preceding claims, characterized in that Suction means are provided which extract gas from the space between the bottom side of the object (7) and the suspension surface (33) substantially in the direction of the suspension 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) comprises a vibration generator (30) and an optical sensor (11) and corresponding illumination means (21, 22, 23), wherein the vibration generator (30) forms a planar suspended surface (33) on the side facing the object (7), wherein the vibration generator (30) is formed in one piece and comprises at least one through-gap (31) partially cut through the suspended surface, the method comprising the following steps: - moving the object (7) from a first end (35) of the levitation surface to a second end (36) of the levitation surface by means of a conveying device, wherein the vibration frequency and the vibration amplitude of the vibration generator (30) are set so that the object (7) can be moved in levitation 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), comprising directly inspecting 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 directly illuminating 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: By means of the conveying device (41, 42) provided at the lower end of the inclined suspension surface of the vibration generator (30), the object (7) is conveyed from the first end (35) of the suspension surface (33) via the suspension surface of the vibration generator (30) transversely to the direction of gravity to the second end (36) of the suspension surface (33), the suspension surface being arranged to be inclined by a maximum of 65° relative to the direction of gravity.

11. The method according to any one of claims 9 and 10, characterized in that The conveying is performed by means of the conveying device, which comprises at least two conveyor belts, each conveyor belt having a belt surface extending transversely to the suspension surface of the vibration generator (30), wherein a first conveyor belt (41) is arranged in the area between the first end (35) of the suspension surface (33) and the at least one gap (31), and a second conveyor belt (42) is arranged in the area between the at least one gap (31) and the second end (36) of the suspension surface (33).

12. The method according to any one of claims 9 to 11, characterized in that The object (7) is inspected such that an inspection axis (11b) of the optical sensor (11) or an illumination axis (21b, 23b) of the illumination device (21, 23) extends at an angle greater than or equal to 5° to a surface normal of the suspended surface.

13. The method according to any one of claims 9 to 12, characterized in that The inspection comprises evaluating captured electromagnetic radiation transmitted through the object (7) and / or captured electromagnetic radiation reflected from the object (7).

14. The method according to any one of claims 9 to 13, characterized in that The inspection includes bright field illumination and / or dark field illumination.

15. The method according to any one of claims 9 to 14, characterized in that Gas is sucked out of the space between the bottom side of the object (7) and the levitation surface (33) substantially in the direction of the levitation surface.

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