Apparatus for inspecting plate-shaped or web-shaped objects

Abstract

An apparatus (1) and a corresponding method for inspecting a web-like or plate-like object (7) having an upper and lower surface are disclosed. To avoid contamination and mechanical damage to the object, while enabling precise optical inspection of the object, the apparatus comprises a vibration generator (30), an optical sensor (11), and, if necessary, corresponding illumination devices (21, 22, 23). The vibration generator forms a planar levitation surface (33) on the side facing the object, and the object is movable over it from a first end (35) to a second end (36) by a transport device (41, 42). The vibration frequency and amplitude of the vibration generator are adjustable so that the object can move while floating substantially parallel to the levitation surface. The vibration generator is formed as a single unit and has one or more penetrating vibration generators. The levitation surface is cut out in such a manner that the object can be directly inspected by an optical sensor located on the side of the vibration generator opposite to the object (34), or by an illumination device (23) located on the side of the vibration generator opposite to the object (34).

Description

Technical Field

[0001] The present invention relates to an apparatus for inspecting a plate-shaped or web-shaped object having an upper surface and a lower surface, such as a thin glass plate, a thin plastic film, a wafer, etc., by an optical sensor.

Background Art

[0002] For inspection, a thin plate-shaped or web-shaped object is usually conveyed on a conveyor belt and illuminated from above and / or below by a lighting device. An optical sensor, such as a camera, acquires the electromagnetic radiation transmitted through and / or reflected by this object. Based on these measurement results, the quality of this object can be evaluated and / or its dimensions can be determined.

[0003] In the case of an ultra-thin plate-shaped or web-shaped object, such as a glass plate or a plastic film for a mobile phone, when the lower surface of this object rests on the conveyor belt, mechanical damage and contamination are likely to occur during conveyance. To avoid this situation, a sonotrode having an acoustic radiation surface facing the object may be used. This type of sonotrode is described, for example, in Patent Document 1 and Patent Document 2. The inspection apparatus disclosed in Patent Document 2 includes a vibration generator provided with a carrier body made of a light-transmissive material. Thereby, the lower surface of the material to be inspected can be observed through the carrier body by an optical sensor disposed below the carrier body. However, this procedure is not advantageous for an ultra-thin plate-shaped or web-shaped object. This is because the carrier body affects the measurement results and reduces the accuracy.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] Therefore, the purpose of this project is to manufacture or identify a device capable of optically inspecting thin, plate-like or web-like objects with high precision while avoiding mechanical damage and contamination. [Means for solving the problem]

[0006] The above objectives are achieved by an apparatus having the features of claim 1 and a method having the features of claim 9.

[0007] In particular, this objective is achieved by a device for inspecting web-like or plate-like objects having an upper and lower surface, the device comprising a vibration generator and an optical sensor and a corresponding illumination device, wherein the vibration generator forms a planar levitation surface on the side facing the object, the object is movable on the levitation surface from a first end to a second end by a transport device, the vibration frequency and amplitude of the vibration generator are adjustable so that the object is movable in a floating state substantially parallel to the levitation surface, the object is inspectable by the illumination device and the optical sensor, the vibration generator is integrally formed and includes one or more through-gap partially cut through the levitation surface, the object is capable of being directly inspected through the gap by an optical sensor positioned on the side of the vibration generator opposite to the object, and / or directly illuminated through the gap by an illumination device positioned on the side of the vibration generator opposite to the object. In the first case, electromagnetic radiation reflected by or transmitted through the object reaches the optical sensor receiving the respective electromagnetic radiation through the gap. In the second case, electromagnetic radiation generated by the lighting device reaches the object through the gap.

[0008] The web-like or plate-like object to be inspected may be a thin or ultrathin glass plate (e.g., for a mobile phone), a wafer, a microchip, or a thin film, which may be formed to be at least partially transparent to electromagnetic radiation. The two largest opposing surfaces of the object are referred to as the top and bottom surfaces, with the side of the object facing the vibration generator forming the bottom surface and the opposite side forming the top surface. The thickness of the object measured between the top and bottom surfaces is, for example, in the range of 0.03 mm to 1 mm.

[0009] A vibration generator (also called a sonotrode) is designed to form a planar levitation surface. The vibration generator may have, for example, a rectangular parallelepiped or a rectangular parallelepiped-like shape. The underside of an object faces the levitation surface and is transported along the levitation surface from a first end to a second end. The direction of transport along the levitation surface is hereinafter referred to as the "transport direction." The vibration frequency and amplitude of the vibration generator are adjustable to generate a standing (steady) pressure wave within an air film positioned beneath the object, thereby causing the object to levitate substantially parallel to the levitation surface and move in the transport direction by the transport device. For example, the vibration generator may have dimensions ranging from 0.4m to 3m in length and from 10cm to 40cm in width, and the levitation surface may be, for example, 400cm. 2 ~12,000cm 2 The vibration generator has a range of magnitudes. The frequency of the vibration generator is, for example, in the range of 10 kHz to 50 kHz, particularly in the range of 30 kHz to 40 kHz, and the amplitude is, for example, in the range of 1 μm to 50 μm. The vibration generator may be mounted on a profile member (for example, an aluminum profile member) to optimize the generation of vibration, that is, mounting is done only at the vibration nodes of the vibration generator, for example, using screws.

[0010] To optically inspect an object, an optical sensor, such as a high-resolution line-scan camera or a matrix camera, is provided to observe the electromagnetic radiation reflected and / or transmitted by the object in bright-field or dark-field observation. Therefore, the illumination device may be designed, for example, as a linear or matrix illumination device with a large number of LEDs arranged linearly or in a matrix. This illumination device illuminates the object in a predetermined area, and the illumination device generates electromagnetic radiation in a wavelength range suitable for each inspection. In one embodiment, the optical sensor is positioned above the top surface of the object. To inspect the transparency of the object, the illumination device is positioned on the opposite side of the vibration generator from the object, illuminating the underside of the object through a gap. Alternatively, the illumination device for illuminating the top surface of the object may be positioned above the object, and the optical sensor may be positioned below the vibration generator on the opposite side from the object. To inspect the reflectivity of the underside of the object, both the illumination device and the optical sensor may be positioned below the vibration generator on the opposite side from the object. In this case, the electromagnetic radiation emitted from the illumination device directly irradiates the underside of the object through a gap. Subsequently, electromagnetic radiation reflected by the object is also directly incident on the optical sensor through the gap. Similarly, to inspect the reflective properties of the object's upper surface, both the optical sensor and the illumination device can be positioned above the object's upper surface. The above illumination and imaging configurations are particularly advantageous for targeting transmitted and / or reflected electromagnetic radiation. Furthermore, by making the illumination angle of the illumination device adjustable and changeable, the bright-field or dark-field properties of the object can be analyzed. For example, a single optical sensor may be positioned above the object's upper surface, one or more illumination devices may be positioned above the object's upper surface, and one or more additional illumination devices may be positioned below the vibration generator on the opposite side from the object. This configuration allows the reflection and transmission of electromagnetic radiation to be observed, for example, in bright-field by the optical sensor. Furthermore, reflection in dark-field can also be measured by a second illumination device positioned above the object's upper surface at a different angle than that of the first illumination device.Thus, in a configuration comprising two or more illuminators and a single associated optical sensor that acquires signals generated by the multiple illuminators and (objects), it is advantageous to separate these signals based on time and / or wavelength. When temporal separation is performed, the illuminators may be repeatedly switched on and off continuously over time so that at any given time, only a single illuminator is providing illumination. The signals acquired by the optical sensor are assigned to their respective illumination signals because they are directly generated in transmission and reflection with respect to the object, based on the measurement period. In addition or alternatively, illumination may be performed in various wavelength ranges so that the signals acquired by the optical sensor can be identified with respect to their respective wavelength ranges. For example, the first illuminator may generate electromagnetic radiation in the wavelength range of 400 nm to 500 nm for visible blue-green illumination, and the second illuminator may generate electromagnetic radiation in the wavelength range of 600 nm to 700 nm for visible red illumination.

[0011] The position and orientation of the optical sensor and one or more lighting devices in the surrounding space are known, particularly in relation to reflective surfaces. The position and orientation of the optical sensor may be determined using known calibration methods.

[0012] An optical sensor, in the form of a line scan camera or a matrix camera, determines a luminance value and / or color value for each pixel in the observation area of ​​an object. In one embodiment, the color values ​​and / or luminance values ​​of all areas of the object may be combined to form an image. The color values ​​and / or luminance values ​​may be sent to a data processing unit, where they may be analyzed for defects and / or contamination. In one embodiment, the entire top and / or bottom surface of an object may be inspected by moving the object along a levitation surface, i.e., in a direction intersecting the optical sensor, which is fixed to the levitation surface at least during inspection. Alternatively, only a portion of the top and / or bottom surface of the object may be analyzed.

[0013] The data processing unit may be integrated into the optical sensor as a module, or it may constitute a separate unit from the optical sensor. In the latter case, image data is transmitted from the camera to the data processing unit by wire or wireless. The data processing unit comprises a processor, which is a functional module that interprets and executes algorithmic instructions / commands, as well as an instruction control unit, an arithmetic unit, and a logic unit. The processor may 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 in which logic circuits can be programmed), discrete logic circuits, and any combination thereof. The data processing unit may also comprise a memory module, an input module (e.g., a keyboard or touchpad), a power module (e.g., a battery), and a display module (e.g., a display). The data processing unit may be formed as an actual hardware resource such as a smartphone, desktop computer, server, notebook, cluster / warehouse-scale computer, or embedded system, or as a virtualized computer resource. The data processing unit may also comprise a transceiver for exchanging data with the optical sensor.

[0014] By using optical data (e.g., intensity data and / or color data) detected by an optical sensor in association with electromagnetic radiation transmitted and / or reflected by the object in bright-field and / or dark-field conditions, it is possible to detect contamination and / or defects in the object during inspection and associate them with specific locations or areas of the object. Contamination and / or defects may include, for example, particles, scratches, stains / discoloration, protrusions, dents, depressions, bubbles, material compression, burrs, and ring marks, and may be present on the top and / or bottom surfaces of the object, or inside the object. Such contamination and / or defects are detected, for example, by changes in contrast and / or brightness in the reflected and / or transmitted electromagnetic radiation. For this purpose, signals acquired by the optical sensor, and potentially digitized, are transmitted to a corresponding data processing unit for evaluation and determination of contamination and / or defects. Based on the known transport speed of the object, as well as the placement of the illumination device and optical sensor, the location or area of ​​detected defects and / or contamination can also be identified from the signals acquired by the optical sensor and associated measurement times. Contamination and / or defects can also be detected, for example, by measuring the deflection or change in deflection of electromagnetic radiation reflected and / or transmitted by the material of the object. This can be done, for example, using the method described in detail in European Patent No. 2390656. The method described in that document is incorporated herein by reference.

[0015] According to the present invention, the vibration generator is integrally formed and includes one or more through-holes that are partially cut out and penetrate the levitation surface, allowing an object to be directly inspected through the gap by an optical sensor positioned on the opposite side of the vibration generator from the object, and / or illuminated through the gap by an illumination device positioned on the opposite side of the vibration generator from the object. Through this gap, electromagnetic radiation transmitted or reflected by the object reaches the optical sensor directly, making it possible to directly determine the transmission or reflection characteristics of the object's underside. Illumination of the object's underside by the illumination device positioned on the opposite side of the vibration generator from the object is also performed directly through this gap. This prevents the signal from being altered by other materials (e.g., the material of the vibration generator), improving the accuracy of the optical inspection. Furthermore, because the vibration generator is integrally formed, both sides of the gap vibrate similarly, and a standing wave that causes levitation is uniformly generated across the entire levitation surface, ensuring that the object is levitated in a way that avoids mechanical damage or contamination of delicate objects. Furthermore, the integrated design of the vibration generator eliminates the time-consuming adjustment required when using two separate sonotrodes. Additionally, the integrated design ensures that vibrations are in phase across the entire surface of the vibration generator. The distance between the underside of the object and the levitation surface formed by levitation is, for example, 20 μm to 100 μm.

[0016] In one embodiment, the vibration generator may include one such gap, or alternatively, the vibration generator may include two or more such gaps, and in one embodiment, the two or more gaps may be parallel to each other or extend at predetermined angles. One or more gaps may include a rounded edge at the front edge in the transport direction, which is advantageous in preventing objects that may bend during transport from getting caught in the gap.

[0017] This gap is formed through the vibration generator and partially cut out of the levitation surface, so that electromagnetic radiation passes through the gap along the path from the lighting device to the object, or from the object to the optical sensor, depending on the configuration of the device. Therefore, the lighting device and / or optical sensor are oriented so that electromagnetic radiation travels from the lighting device through the gap to the object, or from the object through the gap into the optical sensor. The gap is formed, for example, in a slit shape, so that only a linear region of the object is illuminated, or reflected or transmitted electromagnetic radiation is recorded by the linear region of the object. The gap, for example, has a maximum dimension (referred to as length) that extends across the levitation surface in a direction intersecting the transport direction, for example, perpendicular to it, and in one embodiment, the length of the gap in the direction intersecting the transport direction is greater than or equal to the width of the object. For example, the length of the gap in the region of the levitation surface is 10 cm or more. For example, the width of the gap in the region of the levitation surface is 0.5 mm or more, for example, 1 mm or more, and 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 region of the levitation surface is less than 5 mm; otherwise, the portion of the object located above the gap will be excessively deformed by its own weight (e.g., bend in the direction of the gap). Since the gap only partially cuts into the levitation surface, the levitation surface includes a web at least at one end of the gap (in the longitudinal direction of the gap) that connects the main body portions of the vibration generators positioned in the transport direction in front of and behind the gap. Such webs (hereinafter also referred to as bridge / connecting webs) may also be positioned at both ends of the gap. Each web forms a rigid connection between the main body portions of the vibration generators, ensuring that all main body portions of the vibration generators vibrate in the same way, thereby ensuring reliable and uniform formation of standing waves and reliable transport of the object. In one embodiment, the connecting web may have a width (the shortest dimension between the end of the gap in the area of ​​the floating surface and the edge of the vibration generator) of 20 mm or more along the floating surface (for example, 10% or more of the length of the gap specified above), thereby ensuring a secure and rigid connection of the main body portion of the vibration generator.

[0018] In one embodiment, the width of one or more gaps in the vibration generator at one gap end located on the levitation surface is smaller than the width of the gap at a second gap end on the vibration generator side, which is located opposite the levitation surface. This allows for keeping the gap dimensions in the levitation surface region small, thereby minimizing deformation of the object in the gap region. On the other hand, this roughly wedge-shaped gap structure allows for the use of various illumination directions and / or observation directions (i.e., the direction of the corresponding illumination axis or inspection axis) of an illumination device or optical sensor located on the side of the vibration generator opposite the object, at a predetermined angle to the levitation surface. In this embodiment, for example, the gap is formed to be trapezoidal in cross-section along the object transport direction. The parallel bases of this trapezoid form the opening / width of the gap in the levitation surface region and in the region of the vibration generator opposite the object, and the opening / width in the levitation surface region is smaller than the opening / width in the region of the vibration generator opposite the object. As partially explained above, for example, the gap width in the buoyancy surface region is 0.5 mm ≤ (width in the buoyancy surface region) ≤ 10 mm, and in particular 0.5 mm ≤ (width in the buoyancy surface region) ≤ 5 mm, and in the region of the vibration generator opposite the object, for example, it is in the range of 5 mm ≤ (width on the opposite side of the object) ≤ 25 mm. The dimensions (thickness) of the vibration generator in the direction perpendicular to the buoyancy surface are in the range of 5 mm ≤ thickness ≤ 30 mm.

[0019] In one embodiment, the levitation surface of the vibration generator is positioned at an inclination of up to 65°, for example, 15° or more, with respect to the direction of gravity, so that the transport of an object from the first end to the second end of the levitation surface is performed continuously at this angle in a direction intersecting the direction of gravity, and the transport device is provided at the lower end of the inclined levitation surface of the vibration generator. In one embodiment, the optical sensor and the illumination device are configured such that the inspection axis (optical axis) of the optical sensor and the illumination axis of the electromagnetic radiation of the illumination device are positioned at corresponding inclinations with respect to the direction of gravity. The transport device may be configured as a conveyor belt. For example, the conveying device comprises one or more conveyor belts, each having a belt surface extending in a direction intersecting the levitation surface of the vibration generator and an annular belt surface moving upward in a conveying direction perpendicular to the inclined levitation surface, for example. When two or more conveyor belts are used, the first conveyor belt is positioned in the region between the first end of the levitation surface and one or more gaps, and the second conveyor belt is positioned in the region between one or more gaps and the second end of the levitation surface. If there are multiple gaps in the vibration generator, a conveyor belt may also be positioned between two adjacent gaps. The conveyor belts allow the object to be moved along the levitation surface easily and cost-effectively in a manner in which the entire object is inspected by the inspection device. The lower edge of the object rests on each conveyor belt. By positioning the object at an angle on the conveying device, slippage during conveyance is prevented, and inspection accuracy is further improved. A configuration in which multiple conveyor belts are placed on both sides of each gap is advantageous because the illumination or observation of objects is not obstructed by the conveyor belts. In one embodiment, the conveying device, such as the conveyor belt, is placed in a corresponding notch with a lowered edge, for example, of a vibration generator.

[0020] In one embodiment, the inspection axis of the optical sensor or the illumination axis of the illumination device extends at an angle of 5° or more with respect to the surface normal of the levitation surface. This configuration is particularly advantageous when analyzing the properties of an object using a single optical sensor not only in bright-field but also in dark-field.

[0021] In one embodiment, the elements of the inspection device described above may be attached to a frame.

[0022] In one embodiment, a suction device is provided that substantially sucks gas (e.g., air) in the direction of the floating surface from the space between the lower surface of the object and the floating surface. For this purpose, small through-holes (e.g., holes in the range of 1 mm to 5 mm in diameter) penetrating the vibration generator may be provided in the vibration generator in a direction perpendicular or oblique to the floating surface, and these are fluidly connected to a gas suction pump (e.g., in the range of a suction pressure of 1 mbar to 100 mbar). Therefore, the suction direction extends substantially in the opposite direction to the floating direction or at an angle thereto. This type of suction device can be used to prevent deformation due to floating movement, particularly in the case of an object with a small thickness (e.g., in the range of 0.03 mm to 0.25 mm).

[0023] The above object is also achieved by a method for inspecting a web-shaped or plate-shaped object having an upper surface and a lower surface. In this method, the device includes a vibration generator, an optical sensor, and a corresponding lighting device, the vibration generator forms a planar floating surface on the side facing the object, the vibration generator is integrally formed, and includes one or more through gaps that penetrate and are partially cut out through the floating surface, and this method includes the step of moving the object from a first end to a second end of the floating surface by a transport device, setting the vibration frequency and amplitude of the vibration generator so that the object can move in a floating state substantially parallel to the floating surface, and the step of inspecting the object by the lighting device and the optical sensor, directly inspecting the object through the gap by an optical sensor disposed on the side of the vibration generator opposite to the object, and / or directly illuminating the object through the gap by a lighting device disposed on the side of the vibration generator opposite to the object.

[0024] This method has the advantages and embodiments described above with respect to the device (each as a method), and reference is made to the above description of the present invention.

[0025] In particular, in one embodiment of the method, when the object is conveyed from the first end to the second end of the inclined floating surface of the vibration generator in a direction intersecting the direction of gravity via the floating surface of the vibration generator arranged at a maximum inclination of 65° with respect to the direction of gravity, it is advantageous.

[0026] In one embodiment of the method, the object is conveyed by a conveying device comprising two or more conveyor belts each having a belt surface extending in a direction intersecting the floating surface of the vibration generator, wherein the first conveyor belt is arranged in a region between the first end of the floating surface and one or more gaps, and the second conveyor belt is arranged in a region between one or more gaps and the second end of the floating surface.

[0027] In one embodiment of the method, the object is inspected in such a manner that the inspection axis of the optical sensor or the illumination axis of the illumination device extends at an angle of 5° or more with respect to the surface normal of the floating surface.

[0028] In one embodiment of the method, the inspection includes an evaluation of electromagnetic radiation transmitted through the object and / or electromagnetic radiation reflected from the object, acquired by the optical sensor, for example, electromagnetic radiation reflected or transmitted by bright-field illumination or dark-field illumination and received by the optical sensor is evaluated with respect to the respective positions of the object, that is, defects such as inclusions, scratches, dirt, etc. present on the surface or inside, and / or the presence or absence of unevenness.

[0029] In one embodiment of the method, the inspection includes bright-field illumination and / or dark-field illumination.

[0030] The electromagnetic radiation used for the inspection may be, for example, electromagnetic radiation in the visible wavelength range (wavelength range of 380 nm to 780 nm), electromagnetic radiation in the infrared range (wavelength greater than 780 nm), and / or electromagnetic radiation in the ultraviolet range (wavelength less than 380 nm). In each case, the electromagnetic radiation used may include individual segments or combinations of multiple segments of these wavelength ranges.

[0031] In one embodiment, the vibration generator includes or consists of one or more materials from the group consisting of aluminum, aluminum alloys, and glass.

[0032] In one embodiment, as described above, gas (e.g., air) is discharged substantially toward the buoyancy surface from the space between the lower surface of the object and the buoyancy surface.

[0033] Other advantages, features, and applicability of the present invention will also be apparent from the following description of the embodiments and the drawings. All features described and / or illustrated, individually or in any combination, constitute the subject matter of the present invention, independent of how the claims are presented or the reference relationships between the claims. [Brief explanation of the drawing]

[0034] A schematic representation is shown below. [Figure 1] Figure 1 is a perspective side view of an embodiment of the inspection apparatus according to the present invention. [Figure 2] Figure 2 is a perspective side view of the embodiment shown in Figure 1 with an object added. [Figure 3] Figure 3 is a front view illustrating the principle of the embodiment shown in Figure 1. [Figure 4] Figure 4 is a perspective side view of the elements necessary for optical inspection of an object, among the elements of the embodiment shown in Figure 1. [Figure 5] Figure 5 is a magnified view of a portion of Figure 1. [Figure 6] Figure 6 is a magnified view of a portion of Figure 3 in the gap area. [Modes for carrying out the invention]

[0035] Figures 1 to 6 schematically illustrate one embodiment of the inspection apparatus 1 according to the present invention in various drawings, and also show the path of electromagnetic radiation.

[0036] An optical sensor in the form of a line scan camera (hereinafter referred to as camera 11), as well as a first illumination device 21, a second illumination device 22, and a third illumination device 23, are mounted on the frame 5 of the inspection device 1. Furthermore, a vibration generator (sonotrode 30) having a gap 31 is provided, and an object (in this case, a thin glass plate 7) is transported on the flat levitation surface 33 on its upper surface from the first end 35 to the second end 36 of the levitation surface 33. The sonotrode 30 is mounted on an aluminum profile. The sonotrode 30 is integrally molded, for example, as an aluminum block.

[0037] To levitate and transport a glass plate 7 measuring 200 mm × 300 mm from the first end 35 to the second end 36 of the levitation surface 33, the sonotrode 30 is operated at a frequency of 30 kHz to 40 kHz and an amplitude of 1 μm to 10 μm. The distance A (see Figure 6) between the lower surface of the glass plate 7 and the levitation surface 33 is, for example, 20 μm to 100 μm. The movement of the glass plate 7 described above is carried out by conveyor belts 41 and 42 positioned on both sides of the gap 31 of the sonotrode 30 within the recess 38 of the sonotrode 30. The glass plate 7 is transported by each conveyor belt 41 and 42 in the transport direction (arrow 40, see Figures 2 and 3) with its lower edge resting on the upper surface of each conveyor belt 41 and 42. Each conveyor belt 41 includes an annular belt, and its surface is formed from, for example, a plastic material.

[0038] The gap 31 located in the central region of the sonotrode 30 extends perpendicular to the transport direction (arrow 40), penetrating the entire sonotrode 30 from the levitation surface 33 to the side 34 of the sonotrode 30 opposite to the glass plate 7 (side 34 is on the opposite side of the levitation surface 33). As a result, the third lighting device 23 located below the sonotrode (i.e., below the side 34 of the sonotrode 30 opposite to the glass plate 7) can directly illuminate the glass plate 7 through the gap 31 (see Figures 3 and 6). However, as is clear from Figures 1, 2, 4 and 5, the gap 31 is not cut out across the entire width of the levitation surface 33, and the portions of the sonotrode 30 located before and after the gap 31 in the transport direction are interconnected by rigid webs 37 and 39, so that the portions of the sonotrode 30 located before and after the gap 31 vibrate with the same frequency, amplitude, and phase. Therefore, above the levitation surface 33, a standing wave is uniformly formed across the gap 31, ensuring that the glass plate 7 moves uniformly on the levitation surface 33 and does not deform in the region of the gap 31. For example, as shown in Figure 6, the gap has a trapezoidal cross-sectional shape and extends along the transport direction (arrow 40). In the region of the levitation surface 33, for example, the width 31b of the gap is 2 mm, and in the region opposite the glass plate 7 or the levitation surface 33, for example, its width 31B is 9 mm. Furthermore, the gap 31 has a dimension of, for example, L = 200 mm along the longer direction (length) intersecting the transport direction. The length L of the gap 31 is usually greater than the width of the glass plate 7 measured in the direction intersecting the transport direction, i.e., on the upper surface of the glass plate 7. The gap 31 has sides that are inclined at a predetermined angle, which allows the electromagnetic radiation generated by the lighting device to be incident at a small angle (e.g., 5° or more) with respect to the normal line erected on the lower surface of the glass plate 7.

[0039] The optical components of the inspection apparatus 1 are arranged such that the first illumination device 21 generates electromagnetic radiation 21a, which directly illuminates a linear area on the upper surface of the glass plate 7. The electromagnetic radiation 21 is incident at an angle of, for example, 10° (referring to the angle of the illumination axis 21b measured with respect to the normal to the upper surface of the glass plate 7). The electromagnetic radiation reflected by the glass plate 7 is reflected by the camera 11 (along the beam 11a having axis 11b) and recorded by the camera 11 (bright-field measurement).

[0040] Furthermore, a second illumination device 22 is positioned above the glass plate 7 and directly illuminates the glass plate 7 in a linear region along beam 22a at a second angle of 10° (see the angle of illumination axis 22b). Camera 11 observes the glass plate 7 under dark-field conditions along beam 11a and axis 11b in relation to this illumination described above. Finally, a third illumination device 23 is positioned below the side 34 of the sonotrode 30. As already described above, the third illumination device 23 illuminates the underside of the glass plate 7 in a linear region with electromagnetic radiation along beam 23a and illumination axis 23b. This electromagnetic radiation reaches the underside of the glass plate 7 directly through the gap 31, at least a portion of which passes through the glass plate and exits the glass plate 7, and is then observed by camera 11 along beam 11a. In each case, this electromagnetic radiation may include, for example, radiation from the visible wavelength range, and the illumination devices 21, 22, and 23 are illuminated continuously and individually for a predetermined period of time, thereby allowing the camera 11 to continuously record the reflected or transmitted electromagnetic radiation and separate them from each other. This separation may be performed (as described above) by the respective wavelength ranges of the electromagnetic radiation used.

[0041] Illumination devices 21, 22, and 23 are each configured as linear illumination devices that illuminate the glass plate 7 in a linear region across its entire width. For this purpose, each is equipped with, for example, a row of LEDs. Camera 11 is configured as, for example, a line scan camera and acquires electromagnetic radiation reflected or transmitted across the entire width of the glass plate 7 in each illuminated linear region. Each pixel of the line scan camera detects a color signal and / or luminance signal, which are then transmitted to the data processing unit 50 for evaluation regarding the presence or absence of defects or stains on or inside the glass plate 7. The data processing unit 50 may combine the individually acquired luminance and / or color values ​​of the linear regions of the glass plate 7 to form an image of the glass plate 7, and further, by relating / adjusting the movement of the glass plate 7 with the measured values, the location / area of ​​defects and / or stains detected on or inside the glass plate 7 can be identified.

[0042] As is particularly clear from Figures 1 and 2, the levitation surface 33 is inclined with respect to the direction of gravity (perpendicular in Figures 1 and 2). For example, the levitation surface 33 forms an angle of α = 30° with respect to the direction of gravity (see Figure 1). The upper surfaces of the two conveyor belts 41 and 42 on which the lower edge of the glass plate 7 rests extend perpendicular to the levitation surface 33. This inclined arrangement and the aforementioned arrangement of the conveyor belts 41 and 42 prevent slippage between the glass plate 7 and the respective conveyor belts 41 and 42. In addition, a gap 43 is formed between the conveyor belts 41 and 42 in the region of the slot 31, so that the conveyor belts 41 and 42 do not obstruct the optical inspection of the glass plate 7.

[0043] Overall, the above inspection device allows for easy and accurate optical inspection while moving ultrathin objects without scratching or contaminating optical components.

Claims

1. An apparatus (1) for inspecting a web-like or plate-like object (7) having an upper and lower surface, wherein the apparatus (1) includes a vibration generator (30), 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) is movable on the levitation surface from a first end (35) to a second end (36) by a transport device (41, 42), the vibration frequency and amplitude of the vibration generator (30) are adjustable such that the object (7) is able to move in a floating state substantially parallel to the levitation surface, and the object (7) An apparatus that can be inspected by lighting devices (21, 22, 23) and an optical sensor (11), wherein the vibration generator (30) is integrally formed and includes one or more through gaps (31) that are partially cut out and penetrate the levitation surface, and the object (7) can be directly inspected through the gaps (31) by the optical sensor (11) located on the side (34) of the vibration generator (30) opposite to the object (7), and / or the gaps (31) can be directly illuminated by the lighting device (23) located on the side (34) of the vibration generator (30) opposite to the object (7).

2. The apparatus (1) according to claim 1, wherein the buoyancy surface (33) of the vibration generator (30) is inclined at a maximum of 65° with respect to the direction of gravity, such that the object (7) is transported from the first end (35) of the buoyancy surface to the second end (36) in a direction intersecting with respect to the direction of gravity, and the transport devices (41, 42) are provided at the lower end of the inclined buoyancy surface of the vibration generator (30).

3. The conveying device (1) according to claim 1 or 2, wherein the conveying device includes two or more conveyor belts, each having a belt surface extending in a direction intersecting the levitation surface of the vibration generator (30), the first conveyor belt (41) being positioned in the region between the first end (35) of the levitation surface (33) and the one or more gaps (31), and the second conveyor belt (42) being positioned in the region between the one or more gaps (31) and the second end (36) of the levitation surface (33).

4. The apparatus (1) according to any one of claims 1 to 3, wherein the width (31b) at the first gap end of one or more gaps (31) of the vibration generator (30) located on the levitation surface (33) is smaller than the width (31B) at the second gap end of the gap (31) located on the side (34) of the vibration generator (30) opposite to the object (7).

5. The apparatus (1) according to any one of claims 1 to 4, wherein the gap (31) has a trapezoidal shape in a cross-section along the transport direction of the object (7).

6. The apparatus (1) according to any one of claims 1 to 5, wherein the inspection axis (11b) of the optical sensor (11) or the illumination axes (21b, 23b) of the illumination devices (21, 23) extend at an angle of 5° or more with respect to the surface normal of the levitation surface (33).

7. The apparatus (1) according to any one of claims 1 to 6, wherein the optical sensor (11) is a line scan camera and / or the illumination device (21, 22, 23) is a linear illumination device.

8. The apparatus (1) according to any one of claims 1 to 7, wherein a suction device is provided for drawing gas substantially toward the buoyancy surface from the space between the lower surface of the object (7) and the buoyancy surface (33).

9. A method for inspecting a web-like or plate-like object (7) having an upper surface and a lower surface, The apparatus (1) includes a vibration generator (30) and an optical sensor (11) and corresponding lighting devices (21, 22, 23), wherein the vibration generator (30) has a planar levitation surface (33) on the side facing the object (7), and the vibration generator (30) is integrally formed and includes one or more through gaps (31) that are partially cut out and penetrate the levitation surface. The method includes the step of moving the object (7) from the first end (35) to the second end (36) of the buoyancy surface using a transport device, wherein the vibration frequency and amplitude of the vibration generator (30) are set such that the object (7) can move in a floating state substantially parallel to the buoyancy surface. A method comprising the step of inspecting the object (7) with the illumination devices (21, 22, 23) and the optical sensor (11), wherein the step includes directly inspecting the object (7) through the gap (31) with the optical sensor (11) located on the side (34) of the vibration generator (30) opposite to the object (7), and / or directly illuminating the object (7) through the gap (31) with the illumination device (23) located on the side (34) of the vibration generator (30) opposite to 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 buoyancy surface (33) in a direction intersecting with respect to gravity by the transport devices (41, 42) provided at the lower end of the inclined buoyancy surface of the vibration generator (30), via the buoyancy surface of the vibration generator (30), which is positioned at an angle of up to 65° with respect to the direction of gravity.

11. The method according to claim 9 or 10, wherein the conveying is performed by a conveying device comprising two or more conveyor belts, each having a belt surface extending in a direction intersecting the levitation surface of the vibration generator (30), the first conveyor belt (41) being positioned in the region between the first end (35) of the levitation surface (33) and one or more of the gaps (31), and the second conveyor belt (42) being positioned in the region between the one or more of the gaps (31) and the second end (36) of the levitation surface (33).

12. The method according to any one of claims 9 to 11, wherein the object (7) is inspected in such a manner that the inspection axis (11b) of the optical sensor (11) or the illumination axes (21b, 23b) of the illumination devices (21, 23) extend at an angle of 5° or more with respect to the surface normal of the levitation surface.

13. The method according to any one of claims 9 to 12, wherein the inspection includes an evaluation of electromagnetic radiation obtained through the object (7) and / or electromagnetic radiation obtained reflected from the object (7).

14. The method according to any one of claims 9 to 13, wherein the inspection includes bright-field illumination and / or dark-field illumination.

15. The method according to any one of claims 9 to 14, wherein gas is drawn substantially in the direction of the buoyancy surface from the space between the lower surface of the object (7) and the buoyancy surface (33).

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