Apparatus and method for inspecting a lateral surface

Abstract

The invention relates to an apparatus (1) and a method for optically inspecting a reflective, convexly curved lateral surface (2) of an object (3) to be inspected, of a multiplicity of such objects (3), in an inspection section (6), wherein the multiplicity of objects (3) and the apparatus (1) perform a relative movement relative to one another at least in the inspection section, said apparatus and method being simple and economical and allowing continuous inspection of the objects (3). The apparatus comprises an illumination device (12), a data processing device (20) and at least three capturing devices (19). The capturing devices (19) are arranged in an outer region which extends around the lateral surface (2) of the object (3) to be inspected, such that each capturing device (19) produces images of part of the lateral surface (2) of the object (3) to be inspected, said lateral surface being illuminated by the illumination device (12), and such that all capturing devices (19) of the apparatus (1) together produce images which capture, in the inspection section, a peripherally extending specified lateral surface portion of the lateral surface of the object (3) to be inspected. The illumination device (12) has a first concave lighting surface (11) and at least one second concave lighting surface (11), the first lighting surface (11) and the at least one second lighting surface (11) each having, at least in parts, the shape of a portion of a lateral face of a cylinder. The lighting surfaces (11) each produce an illumination pattern which the lateral surface (2) of the object (3) to be inspected reflects from the particular lighting surface (11) into at least one of the at least three capturing devices (19). The field of view of each capturing device (19) and the capturing times of each capturing device can be set such that, during the relative movement during which the object (3) to be inspected is in the inspection section (6), each of the at least three capturing devices (19) produces at least two images of the lateral surface (2) of the object (3) to be inspected, each image containing a reflection of an illumination pattern of the illumination device (12) by the lateral surface (2).

Description

[0001] IS RA VISION GmbH

[0002] Our reference number: 240280WO

[0003] Device and method for inspecting a side surface

[0004] DESCRIPTION

[0005] The invention relates to a device and a method for the optical inspection of a reflective, convexly curved, for example cylindrical, side surface of an object to be inspected from a plurality of objects. In particular, the device and the method relate to the inspection of the entire side surface of such an object when the plurality of these objects and the inspection device perform a relative movement and the objects are arranged in a row with variable distances between them.

[0006] The inspection of reflective and curved surfaces is currently carried out using various methods.

[0007] Document US 2019 / 0257692 A1 discloses, for example, a method for monitoring the color decoration of cylindrical objects using a spectrophotometer or spectrometer, wherein the spectrophotometer or spectrometer uses spot color reading in the viewing area of ​​at least one camera whose position in the viewing area is known. This method allows for spot monitoring of a color decoration, but not for large-area inspection of the entire cylindrical side surface of an object.

[0008] German patent application DE 10 2010 032 410 B4 discloses and describes an inspection method for examining vessels that are fixedly arranged at a predetermined distance on a processing machine. The vessels are inspected in an inspection position on the processing machine using a camera and two optical elements. The first optical element is fixed in position relative to the inspection position to capture images of at least one view towards the vessel opening, while the second, movable optical element is positioned to capture images of at least one view towards the side of the vessel facing away from the opening. The second optical element can be moved towards the vessel to capture images and then retracted, allowing the next vessel to be inspected to enter the inspection position unimpeded.This method is discontinuous and unsuitable for continuous inspection. The method described in this publication is also unsuitable for inspecting objects not fixed to a processing machine, such as objects moving along a conveyor belt at unequal intervals.

[0009] The task is therefore to specify a simple and cost-effective method or to create a corresponding device so that a large number of objects with convexly curved side surfaces can be continuously inspected, which perform a relative movement to the inspection device and are arranged in a row with variable distances.

[0010] The above problem is solved by an inspection device having the features of claim 1 and a corresponding method having the features of claim 10.

[0011] In particular, the problem is solved by a device for the optical inspection of a reflective, convexly curved side surface of an object to be inspected, or of a plurality of such objects in an inspection section, wherein the plurality of objects are arranged individually one behind the other and spaced apart from each other along the row, wherein the plurality of objects and the device perform a relative movement to each other in a predetermined direction of movement, at least in the inspection section, wherein the device comprises a lighting device, a data processing device and at least three recording devices connected to each other, wherein the at least three recording devices are arranged in an outer area extending around the side surface of the object to be inspected, such thatthat each recording device produces images of a portion of the side surface of the object to be inspected, illuminated by the lighting device, and that all recording devices of the apparatus together produce images which, in the inspection section, capture a circumferential, predetermined side surface section of the side surface of the object to be inspected, wherein the lighting device has a first concave illuminating surface and at least one second concave illuminating surface, wherein the first illuminating surface and the at least one second illuminating surface each have, at least partially, the shape of a cylindrical shell section, wherein the first illuminating surface and the at least one second illuminating surface are arranged laterally to the row of objects during the relative movement in a predetermined period of time, wherein the first illuminating surface and the at least one second illuminating surface each produce an illumination pattern.which is reflected from the respective illuminating surface via the side surface of the object to be inspected into at least one of the at least three recording devices, wherein the field of view of each recording device and its recording times are adjustable (i.e., each recording device is configured) such that during the relative movement in which the object to be inspected is located in the inspection section, at least two images of the side surface of the object to be inspected are generated by the respective recording device, so that with regard to the images thus obtained from all recording devices, each area of ​​the specified side surface section is depicted in at least two different images.wherein the respective image capture includes a reflection of an illumination pattern of the illumination device (i.e., the respective illuminating surface of the first and at least one second illuminating surface) on the side surface, wherein the at least three recording devices are designed such that the image data of the at least two generated image captures of the side surface of the respective object to be inspected, or data derived from these image data, are made available at the data output of each recording device of the data processing device for further processing to determine an inspection result for the specified side surface section of this object.

[0012] The inspection device defined above is used in particular for inspecting a reflective, circumferential, convexly curved side surface of an object to be inspected. This side surface has the property that, due to its essentially convex curvature, which may include round, elliptical, and partially flat surfaces (possibly with edges), it partially or completely circumferentially surrounds the object to be inspected, i.e., forms a lateral surface. The side surface may, for example, have an essentially cylindrical shape, where "essentially cylindrical shape" means that the object's side surface may exhibit slight deviations from a cylindrical shape, for example, on a maximum of 20% of the side surface's area. In the latter case, the object is, for example, cylindrical. The side surface of the respective object is a surface that does not constitute a base or top surface of the object.The base is the surface on which the object stands, and the top surface is a surface substantially parallel to the base. For the purposes of this description, an object axis is used that is perpendicular to the plane of the relative movement between the object and the inspection device. In the case of a cylindrical object with a substantially cylindrical side surface, the object axis corresponds to the axis of the cylinder. The image acquisition for inspection takes place within a predefined, circumferential section of the side surface. For example, at least 95% of the cylindrical surface of a cylindrical object is inspected. In one embodiment, the data processing device can process data from a digital model (e.g.,The system uses data from a CAD model of the object and / or its surface from a corresponding storage device connected to the data processing unit to determine an inspection result for the respective object. The numerous objects to be inspected are arranged individually in a row, one behind the other. Furthermore, the objects and the inspection device perform relative movement in the specified direction of movement, at least during one inspection segment. Along the row, the objects are spaced apart from each other in the specified direction of movement; that is, each object is spaced apart from its neighboring objects, and these distances can be variable.The distance between the objects in the direction of movement and the viewing angles of the at least three recording devices are linked, as a superposition of reflections of the lighting pattern from different objects must be avoided. In one embodiment, the distance between the objects in the direction of the relative movement is set such that it is at least The value is where r represents the radius of the object. Furthermore, the quantity 9 represents the viewing angle, which is the smallest viewing angle of the at least three recording devices relative to the direction of the relative movement of the object and the inspection device. Additionally, the adjacent objects can have a distance Ay in a direction transverse (perpendicular) to the direction of the relative movement, for example, offset laterally by Ay relative to the direction of the relative movement. This calculation assumes a field of view of 0° (telecentricity). For large field of view, the required distance may be further reduced. This means that each object must have a minimum distance d relative to its two adjacent objects. m / n (minimum distance) in the direction of movement. As can be seen from the above explanations, the minimum distance of the objects depends on the speed of the objects' relative movement to the inspection device. The relative movement between the multitude of objects and the inspection device can be uniform motion, i.e., motion at a constant speed. At the beginning and end of each inspection cycle, the series of objects can be terminated by a first object and a second object, respectively, with the first and last objects each having only a single adjacent object in the series.As explained above, the multitude of objects also performs a relative movement to the inspection device in the predetermined direction of movement. For example, the inspection device can be stationary, and the multitude of objects can move past the inspection device individually, one after the other, in a row on a conveyor belt. The conveyor belt can, for example, move continuously at a speed of 10 m / s to 60 m / s. The objects move at the same speed. Alternatively, the inspection device or parts thereof can be moved relative to the objects arranged in a row. The direction of the relative movement essentially corresponds to the direction of the row of objects, whereby, in one embodiment, the individual objects can be offset in a direction perpendicular to the direction of movement, for example, by a maximum of 1 mm to 5 mm.The inspection of the multitude of objects takes place in an inspection section, the length of which is defined in relation to the respective stationary element (inspection device or parts thereof, or series of the multitude of objects) prior to the inspection of the multitude of objects. The inspection section can, for example, have a length of 30 mm to 200 mm, preferably 50 mm to 130 mm, along the predetermined direction of relative movement. Depending on the position of the first illuminating surface and at least one second illuminating surface or the corresponding receiving devices along the direction of relative movement, several such inspection sections can also be provided.The inspection section is positioned, for example, approximately in the region of the axis of curvature of the respective illuminated surface, which illuminates the predetermined side surface section to be inspected, of which at least two images are generated within the inspection section. This means that the inspection section begins slightly in front of the position of the axis of curvature in the direction of the relative movement – ​​depending on the length of the inspection section – and ends correspondingly slightly behind the axis of curvature.

[0013] The maximum speed of the relative movement between the objects and the inspection device depends on the minimum image resolution required for the specific inspection task. Other factors in this context include the exposure time of the at least three imaging devices, the reflectivity of the surface of the objects to be inspected, the brightness of the first and at least one second illumination surface of the lighting device, the aperture setting of the lenses, and the minimum exposure time of the photosensors of the at least three imaging devices. If the illumination surface is not continuously lit, the flash duration of the first and at least one second illumination surface may also be significant.

[0014] The inspection device comprises a lighting unit, a data processing unit, and at least three recording units. For example, the inspection device may also be equipped with four or five recording units. The maximum number of usable recording units depends on whether shadowing effects caused by the recording units or, if applicable, by the deflecting mirrors, prevent or at least significantly impede the complete capture of the specified side surface section by image recording. Each of the at least three recording units is, for example, designed as a matrix camera or a line scan camera.In this system, the lighting device, the at least three recording devices, and the data processing device can be interconnected in such a way that the lighting device and / or the at least three recording devices are controlled by the data processing device, and that the at least three recording devices are also connected to the data processing device for transmitting the acquired images. Accordingly, the lighting device, the data processing device, and the at least three recording devices are electronically connected for data exchange. The control mechanism: The data processing device can, for example, control the lighting pattern generated by the lighting device on the first illuminated surface and the at least one second illuminated surface, e.g., when this pattern is modified for generating the images.The generated lighting pattern can remain constant during the period of relative movement of a single object within the inspection section, or it can be changed according to a predefined sequence. This period can be easily determined from the speed of relative movement of the multitude of objects to the inspection device and from the length of the inspection section.

[0015] As explained above, any recording device can be designed as a matrix camera, for example, a CCD or CMOS camera, which is also known as an area scan camera. The matrix camera captures the light intensity of a large number of pixels arranged in rows and columns, i.e., in a matrix, from the illuminated area. For this purpose, the matrix camera has a light-sensitive element (e.g., a CCD or CMOS sensor) for each pixel. The size of the area captured by each light-sensitive element determines the resolution of the matrix camera. For example, the matrix camera can have a field of view of 9344 x 7000 pixels, 8192 x 8192 pixels, or 2448 x 2448 pixels. The matrix camera is focused in such a way that it exhibits the most uniform sharpness possible across the entire field of view. This is achieved by an appropriate aperture setting that provides the necessary depth of field.

[0016] In one embodiment, the focal plane of one or more of the at least three recording devices can be tilted according to the so-called Scheimpflug arrangement in order to achieve a sharp image recording over an extended area of ​​the side surface of the respective object.

[0017] According to the invention, the at least three receiving devices are arranged in an outer area that extends around the side surface of the object to be inspected. In one embodiment, the outer area described above lies outside a volume that encloses the object with its convexly curved side surface. In another embodiment, when projected onto a plane perpendicular to the object's axis, the at least three receiving devices are arranged outside the side surface, which appears circular in this projection. In yet another embodiment, the at least three receiving devices also lie outside a volume that encloses opposing illuminating surfaces of the lighting device.In all arrangements of at least three recording devices, it is important that each recording device, when the respective object is located in the respective inspection section, has a direct line of sight to at least one section of the object's predefined, circumferential side surface when generating the at least two images. The at least two images are each generated at a predetermined time, depending on the speed of the relative movement, such that shadows generated by the recording device or, if necessary, a deflecting mirror, are located in different areas of the respective image, allowing them to be removed during image data processing by the data processing device.The at least three recording devices are arranged, for example, such that each recording device produces images of a portion of the side surface of the object to be inspected, illuminated by the lighting device, and that all recording devices of the apparatus together produce images such that, with regard to the images thus obtained from all recording devices, each area of ​​the specified side surface section is depicted in at least two different images. In the case of a cylindrical side surface of a cylindrical object, the specified side surface section can, for example, comprise at least 95%, at least 98%, or 100% of the side surface of the object to be inspected.This means that the field of view of each imaging device in the inspection section captures a portion of the specified side surface segment of the object being inspected. The object being inspected moves relative to the inspection device, so the captured area of ​​the specified side surface segment differs between two different images. All three imaging devices together capture the entire specified side surface segment in the inspection section, such that each area of ​​the specified side surface segment is depicted in at least two different images, generated by the same or different imaging devices. The specified side surface segment may optionally also include the edges and / or corners of the respective side surface.In one embodiment, the fields of view of the at least three recording devices are arranged such that they partially overlap, so that at least a portion of the specified side surface section of the respective object appears in images from any two of the at least three recording devices. To achieve this, the positions and viewing angles of the at least three recording devices, and the times at which the respective recording devices generate images, are simulated for the respective system, for example, using visualization software (e.g., Blender), as part of a system design. The positions, viewing angles, and image acquisition times are determined in such a way that the side surface of the object to be inspected is captured as described above, i.e., as completely as possible.

[0018] In one embodiment, the image captures, in particular, a curvature of the side surface that forms a continuously curved transition to a base or top surface of the object. Such a curvature of the side surface can render an edge or corner at the transition to a base or top surface of the object obsolete.

[0019] The inspection device includes a lighting unit comprising a first concave illuminating surface and at least one second concave illuminating surface, wherein the first illuminating surface and the at least one second illuminating surface each have at least partial portions resembling a cylindrical shell segment. In one embodiment, the first illuminating surface and the at least one second illuminating surface each have the complete shape of a cylindrical shell segment. In another embodiment, the first illuminating surface and / or the at least one second illuminating surface may, for example, in the circumferentially arranged edge regions, also have a different shape that is not cylindrical shell segment-shaped. In one embodiment, the first illuminating surface and / or the at least one second illuminating surface has a cylindrical shell segment shape, particularly in the central section viewed in the circumferential direction.The circumferential direction runs around the axis of an (imaginary) cylinder representing the cylindrical shape. Due to their concavity, the illumination direction of the first and at least one second illuminating surface is designed such that they shine, as it were, into the interior of an imaginary cylinder that forms the (partial) cylindrical shape of the respective illuminating surface. During the relative movement, each of the first and at least one second illuminating surface is positioned laterally to the row of objects or the predetermined direction of the relative movement for a given period of time. This means that the respective concave illuminating surface is opposite the respective predetermined section of the convex side surface of the object, so that the illuminating surface surrounds and illuminates the respective predetermined section of the side surface.The first illuminating surface and at least one second illuminating surface each generate an illumination pattern which is reflected from the respective illuminating surface, via the side surface of the object to be inspected, into at least one of the at least three receiving devices. The illumination pattern reflected from the respective side surface of the object to be inspected can be imaged directly from the side surface or via at least one deflecting mirror into at least one of the at least three receiving devices. The cylindrical section of the illuminating surfaces can be arranged such that the axis of the respective cylindrical section of the illuminating surface is essentially perpendicular to the direction of the relative movement, for example, parallel to the object axis of the objects that are moving relative to the inspection device.Furthermore, the first illuminating surface and the at least one second illuminating surface are arranged such that they surround the objects at least in part of the inspection section and, with respect to the entire inspection section, surround them on all sides. For example, the first illuminating surface and the at least one second illuminating surface enclose the largest possible angle perpendicular to the axis of the cylindrical shell section (excluding the openings for the objects to pass through during relative movement). The radius of the (imaginary) cylinder forming the cylindrical shell section of the illuminating surface is designed to be approximately 5 to 10 times, for example 7 to 10 times, the radius of the object to be inspected, taking into account the space available for inspection.Depending on the focal length and the recording equipment used, this ratio can be adjusted. The height H of the illuminated surfaces is greater than the height h of the predetermined side surface sections of the objects to be inspected (measured perpendicular to the direction of relative movement); for example, H > 2 ■ h.

[0020] The inspection device is further characterized in that the field of view of each recording device and its recording times are adjustable such that, during the relative movement in which the object to be inspected is located within the inspection section, at least two images of the side surface of the object to be inspected are generated by the respective recording device, so that each area of ​​the specified side surface section is depicted in at least two different images, each image including a reflection of an illumination pattern from the illumination device on the side surface. Each recording device is thus controlled in such a way that at least two images of the side surface in the specified side surface section of each object are generated within the inspection section. In one embodiment, three, four, or more than four images can also be generated.The field of view of each recording device is therefore large enough, and the images are captured at appropriately timed intervals, to ensure that at least two images can be taken during the relative movement of the object and the inspection device. Furthermore, the field of view of each recording device is selected such that each image captures the illumination pattern reflected from the side surface of the object in the respective predefined section of that side surface and generated by a light source of the illumination device.

[0021] Furthermore, the at least three recording devices are designed such that the image data from the at least two generated image captures of the specified side surface section of the respective object to be inspected, or data derived from these image data, are made available at the data output of each recording device to the data processing unit for further processing to determine an inspection result for the specified side surface section of this object. Derived image data is generated by data processing in the respective recording device, for example, by filtering, data compression, scaling / deformation, translation, brightness adjustments, contrast adjustments, dynamic range adjustments, each, for example, to a specified value range, and anomaly detection.In one embodiment, for each image captured of the specified side surface section of the object to be inspected, or for each imaging device, a data record is made available at the data output of the respective imaging device. This data is then transmitted to the data processing unit and used there to determine an inspection result with respect to the specified side surface section of the object to be inspected.

[0022] The data processing unit for processing image information and determining whether an irregularity exists on the specified side surface section, as well as for controlling the at least three recording devices and the lighting device, and, if necessary, determining which quality indicator can be assigned to the object, comprises a processor that represents a functional module which interprets and executes instructions / commands from algorithms and includes an instruction control unit, an arithmetic unit, and a logic unit. The processor can include at least one microprocessor, one digital signal processor (DSP), one application-specific integrated circuit (ASIC), one field-programmable gate array (FPGA – a digital integrated circuit into which a logic circuit can be programmed), one discrete logic circuit, and any combination of these components.The data processing unit may also include a storage unit, an input module (e.g., keyboard or touchpad), a power supply module (e.g., battery), and a display module (e.g., display). The data processing unit may be a physical hardware resource, such as a smartphone, desktop computer, server, notebook, cluster / warehouse-scale computer, embedded system, or similar, or a virtualized computer resource. Furthermore, the data processing unit may include a transceiver for exchanging data / image information with a display. The data processing unit also has an interface for exchanging data with the at least three recording devices and / or with the lighting device.

[0023] With the device according to the invention, an object can be easily inspected in a predetermined side surface section with a convexly curved side surface, for example with a cylindrical shell shape, for example with regard to the presence of irregularities (defects) on, in or on the side surface such as a surface scratch (e.g. sidewall impression), a deformation (crater or dent, protrusion or bump, staple dent (i.e. dent pattern)), contamination, orange peel, pore, cracking, grinding marks, specks, surface defects, blister, residues, rust, grease film on the side surface, electrolyte residues, optionally wet impression, inclusion, e.g. particles under foil, curved sections (e.g. sidewall finning).The previously mentioned irregularities (defects) can be referred to as irregularity types or defect types, whereby – depending on the application – only individual types from this multitude of irregularity types can be determined. If necessary, a quality indicator can be calculated from the presence or absence of irregularities, representing a specific measure of the object's quality. In particular, it is possible to inspect a large number of such objects, or their surfaces, individually and sequentially. The objects and the inspection equipment can move relative to each other, allowing for a high throughput (e.g., several objects per second) and tolerating variable distances between the objects in the row.Furthermore, by determining the deviation of the surface curvature from the value of a given digital model, it is possible to determine the depth of a deformation at the location of the irregularity.

[0024] In one embodiment, the cylindrical shell-shaped section of the first illuminating surface and / or the at least one second illuminating surface extends over an angle of at least 90°, for example at least 120°, and in another example at least 160°. The specified angle is relative to the axis of an imaginary cylinder that forms the respective cylindrical shell section of the first illuminating surface or the at least one second illuminating surface.

[0025] In one embodiment, two illuminating surfaces—the first illuminating surface and the at least one second illuminating surface—are spaced apart or overlapping in the direction of the predetermined direction of relative movement. The first illuminating surface and the at least one second illuminating surface are, for example, arranged on both sides of the predetermined direction of movement or the row of objects. If two illuminating surfaces overlap, they are arranged such that they are at least partially directly opposite each other along the direction of movement and partially offset from each other. They can also be arranged such that they are completely opposite each other, with no offset in the direction of movement. Alternatively, they can be completely offset from each other along the direction of movement, i.e., with a distance along the direction of movement that is greater than zero.In particular, this allows the inspection device to be adapted to the available space. If at least two illuminating surfaces are offset from each other in the direction of relative movement, the inspection section can have at least two subsections, with at least one receiving device in each subsection generating at least two images of the light reflected from the object by the respective illuminating surface. Each subsection of the inspection section lies in the region of the axis of the cylindrical shell that forms the section of the cylindrical shell which at least partially constitutes the respective illuminating surface. In one embodiment, two illuminating surfaces of the first illuminating surface and the at least one second illuminating surface are arranged on opposite sides of the row of objects.This allows for easy inspection of the entire specified side surface section of the respective object to be inspected.

[0026] In one embodiment, the illumination pattern is a striped pattern consisting of alternating parallel light and dark stripes, or a quadrilateral pattern consisting of alternating parallel light and dark quadrilaterals, for example, rectangles or trapezoids. Light stripes or quadrilaterals can be used to create bright-field illumination of the respective area of ​​the side surface, and dark stripes or quadrilaterals can create dark-field illumination of the respective area. In one embodiment, the adjacent quadrilaterals can be arranged in strips, creating a checkerboard pattern or a pattern similar to a checkerboard, in which, for example, similar (light or dark) quadrilaterals arranged in adjacent strips overlap.For example, each illuminated surface can be composed of a multitude of light-emitting diodes (LEDs), which, depending on their respective control, either illuminate (i.e., create a bright area of ​​the illuminated surface) or do not illuminate (i.e., create a dark area of ​​the illuminated surface). The stripe or square pattern can be designed as a rectangular profile or a continuous profile, e.g., in a sinusoidal shape. Other profile shapes are also possible. The stripes of the stripe pattern have a width of, for example, 1 mm to 10 mm (corresponding to the width of a bright or a dark stripe), while a sinusoidal profile can, for example, have a period length of 5 mm to 20 mm. The first illuminated surface and at least one second illuminated surface can create the same or different illumination patterns. The illumination patterns can differ, for example, in the inclination angle of the stripes or axes.The strip width or period length suitable for the respective inspection task depends, for example, on the size of the object or the size of its specified side surface section to be inspected, the distance of the object to the first and to at least one second illuminated surface, and on the resolution necessary for the defects (irregularities) to be detected.

[0027] In one embodiment, the stripes of the stripe pattern, or the axes of stripes arranged side by side in adjacent quadrilaterals, run at an angle of -60° to -30° and from 30° to 60° to the object axis. The axis of stripes arranged side by side in adjacent quadrilaterals is understood to be the center line of such a stripe. The oblique arrangement of the stripes or the axes of the stripes has the advantage that ring-shaped, circumferential defects (irregularities) can be detected whose path is perpendicular to the object axis. In one embodiment, the illumination pattern reflected from the side surface of the object to be inspected is directed into the respective receiving device via a deflecting mirror. This means that a separate deflecting mirror is provided for each receiving device.The respective deflecting mirror is arranged, for example, at an angle of 30° to 80° to the object axis, for instance, between the side surface and the first illuminated surface and / or the at least one second illuminated surface. In one embodiment, the mirror surface of the deflecting mirror is just large enough that the light deflected from the side surface of the object to be inspected into the respective receiving device covers the entire field of view of the receiving device, thereby enabling the capture of a portion of the circumferential, predetermined side surface section. The mirror surface can also be somewhat smaller, as this reduces any shadowing effect of the mirror. By using a deflecting mirror, the receiving device can be very easily positioned outside the area enclosed by the lighting device and the object to be inspected.The deflecting mirror can be positioned within a defined area so that it does not interfere with the light path. Furthermore, the lighting device can be designed to be more compact overall, as the deflecting mirror allows the camera to be positioned axially along the object axis instead of radially, resulting in a smaller radial footprint for the inspection device. However, the deflecting mirror is located within the area between the light source and the object, meaning that any "disturbance" in the image data caused by reflections and interruptions of the light path by the deflecting mirror must be compensated for. This compensation can be achieved, for example, by capturing at least one second image with the camera, which, due to the relative movement of the inspection device and the object, captures a different configuration of the object being inspected, the light source, and the deflecting mirror.

[0028] In one embodiment, the illumination pattern reflected from the side surface, in particular from the circumferential, predetermined side surface section of the object to be inspected, passes through a continuous opening in the illuminating surface into the respective recording device. The opening can, for example, have a diameter corresponding to the diameter of the imaging optics of the respective recording device. This eliminates the need for a deflecting mirror.Analogous to the use of a deflecting mirror, an interruption of the respective illumination pattern formed by the continuous opening for the passage of light in the illuminating surface is compensated for by at least one second image acquisition by the respective recording device. This second image acquisition, due to the relative movement of the inspection device and the objects, includes a different configuration of the inspected object, the illuminating surface of the lighting device, and the recording device. In one embodiment, the illumination pattern can be generated using light from a predetermined wavelength range of 400 nm to 850 nm.

[0029] In one embodiment, motion information regarding the relative movement between the multitude of objects and the inspection device is acquired by means of a motion detection device and transmitted to the data processing unit. In particular, the entry of an object into the inspection section and / or the exit of a single object from the inspection section can be detected, e.g., by means of or based on a light barrier or another optical or non-optical sensor, for example, an ultrasonic sensor, and transmitted to the data processing unit, so that the generation of image data by the at least three recording devices and the control of the lighting device can be carried out by the data processing unit based on the motion information.In one embodiment, the speed of movement of a conveyor belt on which the objects are arranged in a row and from which the objects are moved can also be included as motion information in the control of the at least three receiving devices and the lighting device.

[0030] The above problem is further solved by a method for the optical inspection of a reflective, convexly curved side surface of an object to be inspected, or of a plurality of such objects in an inspection section, by means of a device, wherein the plurality of objects are arranged individually one behind the other and spaced apart from each other along the row, wherein the device comprises a lighting device, a data processing device and at least three recording devices connected to each other, wherein the at least three recording devices are arranged in an outer area extending around the side surface of the object to be inspected, with the following steps:

[0031] • Execution of a relative movement in a predetermined direction of movement of the objects arranged in the series and the device, at least in the inspection section,

[0032] • Generation of an illumination pattern by a first illuminating surface and at least one second illuminating surface of the illumination device, wherein the first illuminating surface and the at least one second illuminating surface each have at least sectional form of a cylindrical shell segment, wherein the first illuminating surface and the at least one second illuminating surface are arranged laterally to the row of objects during relative movement over a predetermined period, wherein the first illuminating surface and the at least one second illuminating surface each generate an illumination pattern, wherein the respective illumination pattern is reflected from the respective illuminating surface via the side surface of the object to be inspected into at least one of the at least three receiving devices,

[0033] • Generation of image recordings of a portion of the side surface of the object to be inspected, illuminated by the lighting device, by each recording device such that all recording devices of the device together generate image recordings which capture a circumferential, predetermined side surface section of the side surface of the object to be inspected in the inspection section,

[0034] • Adjusting the field of view of each recording device and its recording times such that, during the relative movement in which the object to be inspected is located in the inspection section, at least two images of the side surface of the object to be inspected are generated by the respective recording device, so that, with regard to the images thus obtained from all recording devices, each area of ​​the specified side surface section is depicted in at least two different images, wherein each image includes a reflection of an illumination pattern of the illumination device on the side surface.

[0035] • Provision of the image data of at least two generated image recordings of the side surface of the respective object to be inspected, or of data derived from these image data, at the data output of each recording device for the data processing device for further processing, in particular for determining an inspection result for this object.

[0036] The above method is carried out, for example, with the inspection device described above and also has the advantages and embodiments explained above.

[0037] In one embodiment of the method, the illumination pattern is generated with light from a predetermined wavelength range, which includes wavelengths in the range of 400 nm to 850 nm.

[0038] The further processing of the image data from the at least two generated images of the specified side surface section of the object involves, after transmission to the data processing device, for example, that a portion of the image data identified as belonging to a different object is not used to determine the inspection result and is treated as a "forbidden zone." These "forbidden zones" can be identified, for example, using visualization software during the system design described above.Further data processing includes, for example, examining the distortion of the stripe pattern or the pattern composed of squares, investigating the contrast of the light and dark stripes or squares, the width of the stripes or squares, the frequency of the stripes or squares, applying a bandpass filter, Fourier transform, or subtracting averages determined over a large number of objects.

[0039] Furthermore, segmentation can be performed during the evaluation of the image data. For segmentation, layout recipes, for example, can be used to extract desired sections of the image recordings from the respective image data matrix, which is determined by matrix-wise or row-wise acquisition.

[0040] In principle, segmentation using a layout recipe defines a specific section of the object within the field of view of the matrix camera. Since the object is not always in the ideal position during image acquisition by the matrix camera, but may be shifted or rotated by a few pixels, a position correction is performed, for example, using predefined fixed points on the object. This means registering the object to the expected position, so that the image data matrix is ​​adjusted accordingly to the ideal position of the object. The image data matrices are rotated and / or shifted as required. Once this adjustment is complete, the desired sections of the image can be reliably identified and extracted using the predefined layout recipe.Furthermore, the sections from different image recordings can be assembled to form the surrounding, predetermined side surface section.

[0041] To evaluate the image data from all images of an object generated as described above, a neural network (NN) algorithm trained on the respective object and / or the respective expected irregularity types (error types) can be used. The NN algorithm represents, for example, a mapping based on a neural network, such as a convolutional neural network (CNN).

[0042] Furthermore, a data model of the respective object (e.g. a CAD model) can be included in the evaluation of the image data of all generated image recordings of the respective object.

[0043] From the processing steps described above, an inspection result can be determined that includes, for example, the location of irregularities (defects) on the specified side surface section of the respective object, the type of each irregularity (defect), e.g., from the irregularity types mentioned above, and the dimensions of each irregularity (defect). The location and dimensions can be specified, for example, in an object coordinate system. The inspection method and inspection device described above can be used, for example, for inspecting a reflective side surface of a cylindrical battery cell, a turned metal part, a body panel, a silicon ingot, a can (e.g., a beverage can), or the like.

[0044] As already stated above, the procedure described above can be implemented, at least in part, as a computer program or computer-implemented procedure comprising instructions which, when executed, cause a processor of the data processing device to perform the steps of the procedure described above, wherein the computer program includes a combination of the steps and data definitions described above which enable the computer hardware to perform computational or control functions, and / or which represents a syntactic unit which conforms to the rules of a particular programming language and which consists of declarations and statements or instructions required for the functions, tasks, or problem solutions described above.

[0045] Furthermore, a computer program product is disclosed which includes instructions that, when executed by a processor of the data processing device, cause the device to perform the steps of one or all of the procedures or parts of procedures defined above. Correspondingly, a computer-readable data carrier that stores such a computer program product is disclosed. The computer program product may be a software routine.

[0046] Further advantages, features, and applications of the invention are described below with reference to exemplary embodiments and the figures. All features described and / or illustrated constitute the subject matter of the present invention, even independently of their compilation in the claims and their cross-references.

[0047] It shows schematically:

[0048] Fig. 1 shows an embodiment of an inspection device in a perspective side view.

[0049] Fig. 1 shows an embodiment of an inspection device 1, which is used for inspecting a convexly curved, in particular cylindrical, side surface 2 of an object 3 with a radius of approximately 23 mm, which is, for example, a cylindrical sleeve for a battery cell. For simplicity, the entire cylindrical side surface 2 is to be inspected; that is, the specified side surface section is the entire side surface 2. The cylindrical object 3 has, for example, a diameter of 46 mm and a height h of, for example, 60 mm, 80 mm, or 120 mm. A plurality of these objects 3 are transported one after the other on a conveyor belt 5 in a direction of movement (see arrow 7) relative to the inspection device 1. Here, the reference numerals 2 and 3 denote only the object 3 that is currently located in an inspection section. As shown in Fig.As shown in Figure 1, a series consisting of numerous individual objects 3 is arranged one behind the other on the conveyor belt 5 and is moved by the conveyor belt 5 through the inspection device 1. The objects 3 are spaced at least 21.5 mm apart. The conveyor belt 5 runs at a constant speed in the direction of arrow 7, for example, at a speed of 40 m / s. Images of the object 3 are generated in the inspection section 6, which extends in the central area between the two concave, cylindrical-section-shaped illuminating surfaces 11 of the lighting device 12, located on either side of the conveyor belt 5 and opposite each other, in the direction of movement and is marked with dotted lines and a dotted arrow indicating the extent (length) of the inspection section in the direction of movement of the conveyor belt 5.The inspection section 6 extends along the axis of the cylindrical-shaped illuminated surfaces 11. The object 3 is illuminated by these surfaces. Images of the object 3 are generated by four imaging devices in the form of matrix cameras (CCD cameras) 19. These are arranged at 90° intervals when viewed from above and generate images of the side surface 2 of the object 3. Each matrix camera 19 is positioned above the illuminated surfaces 11 and has, for example, 5 megapixels to achieve high resolution. The viewing direction of the matrix camera is parallel to or slightly inclined to the object axis. One edge of the light-sensitive matrix of the camera, e.g., the long edge, runs radially to the object axis.

[0050] Each illuminating surface 11 is generated by a plurality of LEDs arranged on the inner, concave surface of two illuminating units 13, the concave surfaces each having the shape of a cylindrical shell section, the radius of the (imaginary) cylinder forming the cylindrical shell section being, for example, approximately 190 mm. Each LED or group of LEDs of each illuminating surface can be controlled separately, so that each illuminating surface 11 can form any desired illumination pattern, the light of which falls onto and is reflected from the side surface 2 of the object 3. In the present example, each illuminating surface forms a striped pattern, concavely curved according to the shape of the illuminating surface 11, consisting of alternating adjacent white and black stripes, the white stripes having, for example, a width of 6 mm and the black stripes having, for example, a width of 6 mm. The striped pattern is shown in Fig.The path of light is indicated by a striped hatching pattern. The stripes are inclined at approximately 45° to the object axis. The light reflected from the side surface 2 of the object 3 then passes via a deflecting mirror 15, assigned to each matrix camera 19, to the respective matrix camera 19. This light path is indicated in Fig. 1 for the object 3 arranged in the inspection section 6 by means of a dashed line with an arrow for each of the two cameras 19. The inspection device 1 therefore has four deflecting mirrors 15. The field of view of each matrix camera 19 and the associated deflecting mirror 15 are designed such that at least two, for example four, images of the side surface 2 of the object 3 can be generated during the relative movement of the object 3 on the conveyor belt 5 in the inspection section 6. In addition, the reflected illumination pattern of the entire side surface 2 of the object 3 is captured by the images of the four matrix cameras 19.

[0051] In addition, a data processing unit 20 is provided, which is connected to the four matrix cameras 19 and the lighting units 13 (see dashed lines; for clarity, Fig. 1 only shows the connection of the data processing unit 20 to a single matrix camera 19 - the three other matrix cameras 19 are also connected to the data processing unit 20).

[0052] The four image images produced by the matrix cameras 19, for example at intervals of 25 ms, which are produced as long as the object 3 moves in the inspection section 6, are subsequently pre-processed in the respective data processing unit of the respective matrix camera 19 and made available as image data at the output of the respective matrix camera 19 for transmission to the data processing unit 20.

[0053] In the data processing unit 20, the image data from all four matrix cameras are processed as described above to obtain an inspection result for the side surface 2 of object 3. The images of the other objects are acquired analogously and processed further by the data processing unit 20.

Claims

1. P a t e n t a n s p r ü c h e 1. Device (1) for optically inspecting a reflective, convexly curved side surface (2) of an object (3) to be inspected, or a plurality of such objects (3) in an inspection section (6), wherein the plurality of objects (3) are arranged individually one behind the other and spaced apart from each other along the row, wherein the plurality of objects (3) and the device (1) perform a relative movement to each other in a predetermined direction of movement, at least in the inspection section (6), wherein the device comprises a lighting device (12), a data processing device (20), and at least three recording devices (19), wherein the at least three recording devices (19) are arranged in an outer area extending around the side surface of the object to be inspected,that each recording device produces images of a portion of the side surface (2) of the object (3) to be inspected, illuminated by the lighting device, and that all recording devices of the device together produce images which, in the inspection section, capture a circumferential, predetermined side surface section of the side surface (2) of the object (3) to be inspected, wherein the lighting device (12) has a first concave illuminating surface (11) and at least one second concave illuminating surface (11), wherein the first illuminating surface (11) and the at least one second illuminating surface (11) each have, at least partially, the shape of a cylindrical shell section, wherein the first illuminating surface (11) and the at least one second illuminating surface (11) are arranged laterally to the row of objects (3) during the relative movement in a predetermined period of time.wherein the first illuminating surface (11) and the at least one second illuminating surface (11) each generate an illumination pattern which is reflected from the respective illuminating surface (11) via the side surface of the object (3) to be inspected into at least one of the at least three recording devices (19), wherein the viewing area of ​​each recording device (19) and its recording times are adjustable such that during the relative movement in which the object (3) to be inspected is located in the inspection section (6), at least two images of the side surface (2) of the object to be inspected are generated by each of the at least three recording devices (19), so that with regard to the images thus obtained from all recording devices (19), each area of ​​the specified side surface section is depicted in at least two different images.wherein the respective image capture includes a reflection of an illumination pattern of the illumination device (12) on the side surface (2), wherein the at least three recording devices (19) are designed such that the image data of the at least two generated image captures or data derived from these image data are output at the data output of each recording device (19) of the data processing device (20) for, Further processing for determining an inspection result for the specified side surface section of this object (3) will be provided.

2. Device according to claim 1, characterized in that the cylindrical shell section of the first illuminating surface (11) and / or the at least one second illuminating surface (11) extends over an angle of at least 90°.

3. Device according to one of the preceding claims, characterized in that two luminous surfaces of the first luminous surface (11) and of the at least one second luminous surface (11) are spaced apart from each other or arranged overlapping in the direction of the relative movement.

4. Device according to one of the preceding claims, characterized in that two luminous surfaces of the first luminous surface (11) and of the at least one second luminous surface (11) are arranged on opposite sides of the row of objects (3).

5. Device according to one of the preceding claims, characterized in that the lighting pattern is a stripe pattern consisting of alternating light and dark stripes arranged next to each other or a square pattern consisting of alternating light and dark squares arranged next to each other.

6. Device according to claim 5, characterized in that the stripe pattern or the axes of stripes of adjacent quadrilaterals run at an angle of -60° to -30° and of 30° to 60° to an object axis of the object to be inspected.

7. Device according to one of the preceding claims, characterized in that the illumination pattern reflected from the side surface (2) of the object (3) to be inspected is directed into the respective receiving device (19) via a deflecting mirror (15).

8. Device according to one of claims 1 to 6, characterized in that the illumination pattern reflected from the side surface of the object to be inspected passes through a continuous opening in the illuminating surface into the respective receiving device.

9. Device according to one of claims 1 to 8, characterized in that the illumination pattern can be generated with light from a predetermined wavelength range, which includes wavelengths in the range from 400 nm to 850 nm.

10. Method for optically inspecting a reflective, convexly curved side surface (2) of an object (3) to be inspected, or a plurality of such objects (3) in an inspection section (6) by means of a device (1), wherein the plurality of objects (3) are arranged individually one behind the other and spaced apart from each other along the row, wherein the device (1) comprises a lighting device (12), a data processing device (20) and at least three recording devices (19), wherein the at least three recording devices (19) are arranged in an outer area extending around the side surface (2) of the object (3) to be inspected, comprising the following steps: • Execution of a relative movement in a predetermined direction of movement of the objects (3) arranged in the series and the device (1) at least in the inspection section (6), • Generation of a lighting pattern by means of a first concave illuminating surface (11) and at least one second concave luminous surface (11) of the lighting device (12), wherein the first illuminating surface (11) and the at least one second illuminating surface (11) each have at least partially the shape of a cylindrical shell section, wherein the first illuminating surface (11) and the at least one second illuminating surface (11) are arranged laterally to the row of objects (3) during the relative movement in a predetermined period of time, wherein the first illuminating surface (11) and the at least one second illuminating surface (11) each generate an illumination pattern, wherein the respective illumination pattern is reflected from the respective illuminating surface (11) via the side surface (2) of the object (3) to be inspected into at least one of the at least three receiving devices (19), • Generation of image recordings of each part of the side surface (2) of the object (3) to be inspected, illuminated by the lighting device (12), by each recording device (19) such that all recording devices (19) of the device (1) together generate image recordings which capture a circumferential, predetermined side surface section of the side surface (2) of the object (3) to be inspected in the inspection section, • Adjusting the field of view of each recording device (19) and its recording times such that, during the relative movement in which the object (3) to be inspected is located in the inspection section, at least two images of the side surface (2) of the object (3) to be inspected are generated by the respective recording device (19), so that, with regard to the images thus obtained from all recording devices (19), each area of ​​the specified side surface section is depicted in at least two different images, wherein each image includes a reflection of an illumination pattern of the illumination device (12) on the side surface (2), • Provision of the image data of at least two generated image recordings of the side surface (2) of the respective object (3) to be inspected or of data derived from these image data at the data output of each recording device (19) for the data processing device for further processing, in particular for determining an inspection result for the specified side surface section of this object (3).

11. Method according to claim 10, characterized in that the illumination pattern is generated with light from a predetermined wavelength range, which includes wavelengths in the range from 400 nm to 850 nm.

Images