EP2391884A1

EP2391884A1 - Device for optically inspecting an at least partially reflecting surface of an item

Info

Publication number: EP2391884A1
Application number: EP09810743A
Authority: EP
Inventors: Joachim Reimann; Volker Huss; Volker Schöllkopf; Klaus-Georg Knupfer
Original assignee: Carl Zeiss OIM GmbH
Current assignee: Carl Zeiss OIM GmbH
Priority date: 2008-12-29
Filing date: 2009-12-23
Publication date: 2011-12-07
Also published as: JP2012514186A; JP5613682B2; US20110310242A1; US8605146B2; WO2010075846A1; DE102008064562A1

Abstract

The invention relates to a device for optically inspecting an at least partially reflecting surface of an item, having a first and at least one second crossbeam (12, 14) each forming a section (32) largely in the shape of a circular segment. The crossbeams (12, 14) are disposed at a longitudinal distance (D) from one another, defining a longitudinal axis (17). The two crossbeams (12, 14) are held at the longitudinal distance (D) by means of a plurality of longitudinal beams (16). The longitudinal beams (16) are disposed at a defined radial distance (38) from the sections (32) in the shape of circular segments. The crossbeams (12, 14) support a light-transparent diffusing screen (34) forming a tunnel-shaped inspection space (36). A plurality of light sources (48) are disposed outside of the tunnel-shaped inspection space (36) behind the diffusing screen, said sources being controllable individually or in small groups in order to generate variable light-dark patterns (90) on the diffusing screen. At least one camera (74, 78) is set up in the tunnel-shaped inspection space (36).

Description

Device for optically inspecting an at least partially shiny surface on an object

The present invention relates to a device for optically inspecting an at least partially shiny surface on an object. In particular, it relates to a device which enables a largely automated or even fully automatic inspection of shiny surfaces under industrial conditions.

In industrial manufacturing of products, product quality has been playing an increasingly important role for many years. On the one hand, high product quality can be achieved through suitably designed and stable production processes. On the other hand, the

Quality parameters of a product as reliable and fully controlled to detect quality defects at an early stage. In many cases, the quality of a product surface plays a role. These may be decorative surfaces, such as painted surfaces in motor vehicles or household items, or technical surfaces, such as the surfaces of finely machined metallic pistons or bearing surfaces.

There are already a large number of proposals and concepts for automatically inspecting reflective surfaces. Frequently, however, the known methods and apparatus can only be used for a specific application because they require high a priori knowledge about the surface to be inspected. Moreover, the known methods and devices for many applications are not mature enough to allow efficient and reliable inspection of surfaces under industrial conditions. In this case, industrial conditions include adhering to cycle times relevant for integration into industrial manufacturing, the ability to perform surface inspection in a shop floor, and / or the ability to quickly and easily adapt surface inspection to changing products.

As a result, for example, in the automotive industry, to a considerable extent, visual inspection of paint surfaces by experienced and trained people has been carried out. The degree of automation in the inspection of glossy paint surfaces is significantly lower than the degree of automation in the manufacturing itself. An example of a device for visually inspecting the paint surface of a motor vehicle is described in US 5,636,024. The device includes a tunnel through which the motor vehicles are transported with the paint surfaces to be inspected. The inner walls of the tunnel have light sources that create a striped pattern of light and dark stripes. These striped patterns are reflected by the paint surface of the motor vehicles. Inspection of the paint surface is performed by persons standing in the tunnel visually inspecting the reflections of the striped patterns on the paint surface. It is easily understood that such an approach relies to a considerable extent on the ability of the viewer and therefore offers only limited reliability. Moreover, such an approach is labor intensive and accordingly expensive. DE 103 17 078 A1 describes a deflektometriscb.es method and a corresponding device. In this method, a striped pattern having a sinusoidal brightness pattern is projected on a screen which is disposed obliquely over a surface to be inspected. The projected pattern is changed or moved so that correspondingly altered striped patterns fall on the surface. During or after changing / moving the pattern, an image of the surface with the reflected pattern is taken each time. By a mathematical combination of the images taken at different times, a result image is to be generated, on the basis of which defective areas and defect-free areas of the surface can be distinguished computationally and / or visually. A similar method and apparatus are known from a publication by Sören Kammel entitled "Deflektomelrie for quality testing of specularly reflective surfaces", published in the German magazine tm-technical measuring, Issue 4/2003, pages 193-198. In this case, the image data obtained is evaluated by comparison with a reference, which requires an exact alignment of the object to be examined with the reference data.

Further methods and devices for optical inspection of at least partially reflecting surfaces are disclosed in DE 198 21 059 C2 or in US 6,100,990. Again, striped patterns with a sinusoidal brightness gradient over the surface to be inspected are considered. In all cases, the fringe patterns are produced on a flat screen, which is arranged obliquely to the surface to be inspected. These methods thus have the disadvantage that in each case only a relatively small surface can be inspected, which also has to be arranged in an at least largely known and defined position and orientation to the strip pattern. A fast, reliable and efficient inspection of shiny surfaces under industrial conditions is therefore not possible.

US Pat. Nos. 5,726,706 and DE 37 12 513 A1 each disclose a method and a device in which a motor vehicle passes under a bridge-like arrangement on which a plurality of cameras are arranged. The detection of paint defects or other surface defects is carried out by means of light strips or light bands whose reflection is evaluated. For a defect-free surface Each camera sees the respective light or dark stripes. A surface defect, such as a bulge, causes the light to be deflected from a light stripe into the image of a dark stripe so that a bright spot of light is visible in the image of the dark stripe. These methods have a limited detection security. Small scratches or dull paint spots, which do not produce significant reflections in a spatial direction other than the surrounding areas, can not be detected with these devices.

DE 10 2005 038 535 A1 has recognized the problems with the adaptation of the surface inspection to cycle times of industrial production and proposes a rotationally symmetrical, in particular cylindrical strip projector for illuminating an object with a surface to be inspected. A cylindrical hollow body should be coated or coated on its inner wall with an electroluminescent film. The film should be provided with colored or graustufigen stripes that are either printed or realized with the help of a second film. The cylindrical hollow body should be mounted in a second outer hollow body so that it can be mechanically offset in a rotational movement. The rotational movement is intended to produce the change in the fringe pattern relative to the surface to be inspected. However, the mechanical movement of the cylindrical hollow body is a disadvantage of this concept, in particular if the device is to be used for the inspection of large-area objects.

Against this background, it is an object of the present invention to provide a device that allows a fast and at least largely automated inspection of objects with reflective surfaces under industrial conditions. It is desirable that the device can be realized as inexpensively and wear-resistant and in principle allows the inspection of very large or very small objects.

This object is achieved according to one aspect of the invention by a device of the type mentioned, with a first and at least a second

Cross member, each forming a largely circular segment-shaped cutout, wherein the cross member are arranged at a longitudinal distance from each other, the one Defined longitudinally, with a number of longitudinal beams, which hold the first and second cross member in the longitudinal spacing, wherein the longitudinal beams are arranged at a defined radial distance from the circular cutouts, with a translucent screen held by the cross members in the circular segment-shaped cutouts, to form a tunnel-shaped inspection space, with a plurality of light sources, which are arranged outside the tunnel-shaped inspection space behind the ground glass and individually or in small groups to generate variable light-dark patterns on the ground glass, with a workpiece holder for the object in the tunnel-shaped inspection room, with at least one camera which is directed into the tunnel-shaped inspection space, and with an evaluation and control unit which is designed to control the light sources and the camera in order to produce different light-dark patterns on the ground glass z u and to capture and evaluate a plurality of images of the object depending on the light-dark patterns.

Thus, the new device uses a tunnel-shaped inspection space, in which the object is brought to the surface to be inspected. The tunnelfbrmige inspection space surrounds the article over an arc length of at least 90 °, preferably over an arc length of more than 120 ° and in particularly preferred exemplary embodiments with an arc length of about 180 ° or more. As a result, the light-dark patterns generated on the ground-glass screen fall on the surface to be inspected from several directions, which facilitates and accelerates the inspection of objects with complex free-form surfaces. It is sufficient if the object to be inspected is arranged in the tunnel-shaped inspection space. A special and / or exact positioning of the object in the inspection space can be omitted in general, unless the object has hidden surfaces and / or undercuts, which must be arranged so that they are facing the at least one camera.

The plurality of light sources, which can be controlled individually or in small groups, makes it possible to generate a multiplicity of different light-dark patterns. Thus, the new device can be easily and quickly adapted to different requirements. In addition, a mechanical movement of the tunnel can be omitted, which especially in the inspection of large items, such as motor vehicles or automotive parts, is beneficial. Since the plurality of individually controllable light sources also allows a displacement or movement of a defined light-dark pattern relative to the object, the workpiece holder can be fixed in principle. In some embodiments, the floor of a workshop or the like may form the workpiece holder. The latter is advantageous if the objects to be inspected are self-propelled and / or transportable on a pallet or a trolley in the tunnel-shaped inspection room.

The arrangement with the at least two cross members and the longitudinal members allows a modular and scalable structure and as a result, a cost-effective implementation.

The evaluation and control unit is designed in preferred embodiments to control the light sources and the camera so that the surface to be inspected is recorded in at least four different positions relative to a defined light-dark pattern, i. there are at least four images of the surface to be inspected in which a defined light-dark pattern is at four different positions relative to the surface. The light-dark pattern preferably has a sinusoidal brightness profile in this case. The evaluation and control unit is advantageously designed to determine the phase angle of the brightness profile relative to the surface to be inspected on the basis of the images, since the phase position correlates with a local inclination of the surface. Based on local inclinations, various surface defects on glossy surfaces can be detected with high accuracy and reliability.

Overall, the new device is based on a concept that allows in principle an automated and therefore fast and reliable surface inspection of different and different sized items. Due to the modular and largely scalable concept, the new device can be realized cost-effectively for different applications. The device can be easily and quickly adapted to changing inspection tasks due to the individually controllable light sources. Due to the tunnel-shaped Inspection room, which forms a defined and outwardly delimited inspection volume, the device can be quite easily used in real production environments, allowing a production-quality control. The above object is therefore completely solved.

In a preferred embodiment, the new device has a plurality of mutually identical light modules, which are arranged between the ground glass and the longitudinal members, each light module having a plurality of light sources. It is particularly advantageous if the structurally identical light modules each have a front which is completely covered with light sources.

The arrangement of the light modules between the ground glass and the longitudinal beams allows undisturbed, shadow-free generation of the light-dark patterns on the screen. This is advantageous to be able to generate largely any light-dark pattern and "wander" over the screen. For the same reason, it is advantageous if the front sides of the light modules are completely covered with light sources and together form a substantially homogeneous surface on which the light sources are arranged with uniform lateral distances from each other in rows and columns. The use of identical light modules reduces the production and maintenance costs.

In a further embodiment, the light modules have a metallic carrier body with a length which is approximately equal to the defined longitudinal distance, wherein the carrier body has a front side, on which the light sources are arranged, and a back, are formed on the cooling fins. Preferably, the light sources are arranged on a thin, flexible and less intrinsically stiff carrier film, which is glued directly onto the front side of the heat sink.

In this embodiment, the light modules have a metallic, preferably inherently stiff and thus self-supporting support body, which has a good thermal conductivity. On the back of the support body cooling fins are formed, preferably integrally, and also preferably extending in the longitudinal direction. The latter has the consequence that the cooling fins of all light modules have radially outward. The variety of G

Light modules thus forms an integrated heat sink, which promotes a direct heat transfer and a defined air flow through the light modules. The arrangement of the light sources on a thin carrier film and the direct bonding of this film to the heat sink also contributes very favorably to the good heat transfer. In a particularly preferred variant of this embodiment, a printed circuit board which contains the control and driver circuits for driving the light sources is arranged directly on one of the cooling fins. Furthermore, it is preferred that the carrier foil with the light sources on at least one side has integral (integrally connected to the carrier film) tabs, which are bent around the heat sink and connected to the circuit board. These variants allow a very compact electrical connection of the light sources to the control electronics. In addition, the light sources can be easily mounted and it is achieved a maximum large thermal coupling of the light sources to the heat sink.

These embodiments are individually and in combination very advantageous to accommodate a desirably large number of separate, individually controllable light sources with small lateral distances and stable to operate. As has been shown in practical experiments, it is difficult for many to have efficient cooling

Light sources in a compact and optimized for the flexible pattern generation

Integrate design. The present embodiments have proven to be very advantageous in this regard as they provide direct heat dissipation radially outward and inward

Longitudinal benefits.

In a further embodiment, the light modules are mounted in the longitudinal direction floating on the cross members. In one embodiment, the light modules are each mounted at a first end in a fixed bearing and at an opposite second end via a spring-loaded floating bearing.

In this embodiment, the at least two cross members are held in the defined longitudinal spacing substantially or even exclusively with the aid of the longitudinal members. Although the light modules extend from one cross member to the other. However, they are exempted to mechanically fix the cross members at the longitudinal distance. A floating mounting of the light modules with a spring-loaded movable bearing allows In a simple and cost-effective manner, a defined orientation of the light sources, but allows an extension of the light modules in the longitudinal direction. This expansion is favored if the length of the individual light modules is substantially greater than their width. In a preferred embodiment, the length of the light modules in the longitudinal direction by a factor of 10 or more is greater than the width, measured in each case at the front of the light modules on which the light sources are arranged. Such proportions of the light modules favor a thermally induced expansion in the longitudinal direction, which can be largely compensated stress-free by a spring-loaded floating bearing. Surprisingly, a movable storage of the light sources is acceptable, although this may change the patterns on the ground glass. The embodiments advantageously contribute to reducing thermally induced stresses within the new device.

In a further embodiment, each light module has two rows of light sources which are parallel in the longitudinal direction and can be driven separately.

In principle, each light module could have on its front side only a row of light sources or more than two rows of separately controllable light sources. However, two series are advantageous because, on the one hand, they offer a higher integration density compared to light modules with only one set of light sources. On the other hand, two parallel rows have the advantage that circles with almost arbitrary radii can be defined transversely to the parallel rows. This makes it possible to position all separately controllable light sources at an optimum radial distance to the ground glass, largely independent of the actual inner radius of the ground glass. Therefore, this embodiment is particularly advantageous for scaling the new device. No matter how large the inner radius of the tunnel-shaped inspection space is selected, the light modules can always be positioned at an optimal distance to the ground glass due to this configuration.

In a further embodiment, the light sources are each arranged with the same radial distances to the ground glass. This ensures a consistently high level of detail and accuracy of the light-dark patterns.

In a particularly preferred embodiment, each light module has four rows of light sources on its front side, wherein in each case four light sources from two adjacent rows which form a quadratic 4-tuple are jointly controlled. Each 4-tuple forms a virtual light source with four times the light output of a single light source.

This embodiment allows a very cost-effective implementation of universally applicable light modules, and it therefore contributes to a particularly cost-effective implementation of the new device.

In a further embodiment, the ground glass is a frosted glass-like ground glass.

In this embodiment, the ground glass is a translucent, but opaque and preferably diffusely diffusing screen. In one embodiment, the ground glass can be a flexible plastic plate, in particular made of Plexiglas (PMMA) or a full-volume PTFE material. A frosted-glass-type ground glass "mixes" the light radiation from neighboring light sources due to its scattering characteristic, which is very advantageous for producing light-dark patterns with soft light-dark transitions. As has been shown in the investigations of the Applicant, such light-dark patterns are particularly well suited for a comprehensive inspection of shiny surfaces.

In a further embodiment, the ground glass is mounted floating on the cross members.

In this embodiment, only the radius of the ground glass is fixed by the cross member. Moreover, the ground glass can move in the longitudinal direction and / or tangentially to the longitudinal direction. This embodiment is of great advantage in order to reduce thermal stresses in the device. In addition, it has been shown that a floating mounting the screen in the longitudinal and / or tangential direction no noticeably negative impact on reliability and detection safety when inspecting glossy surfaces. Regardless, embodiments of the new apparatus may include where the ground glass is coupled to a position detector that detects a change in size and / or position of the ground glass. Such a position detector can be realized for example by means of reference marks, which are arranged on the ground glass. With these embodiments, a temperature compensation can be realized, which compensates for a thermally induced change in the light-dark pattern. The presently preferred embodiments of the new device, however, do without such a temperature compensation, especially when the radius of the ground glass is fixed by the cross member.

In a further embodiment, the cross member on retaining clips, which are adapted to fix the ground glass exchangeable. In some embodiments, the ground glass is a flexible plate that is held in a defined radius by means of the cross members. In other embodiments, the ground glass is bent to measure. Advantageously, the circular segment-shaped cutouts of the at least two transverse beams are aligned with one another in the longitudinal direction, which facilitates a simple insertion of the ground-glass screen into the cut-outs. Furthermore, it is preferred if the cross members and the retaining clips are formed so that the ground glass is integrally inserted into the largely circular segment-shaped cutouts.

In the new device, the tunnel-shaped inspection space is essentially delimited by the translucent screen. Therefore, the ground glass is susceptible to contamination that can be avoided in a real production environment only with great effort. On the other hand, contamination of the ground glass affects the quality of the light-dark patterns. Therefore, it is advantageous if the ground glass can be easily and quickly replaced, which allows the present embodiment in a comfortable manner. In a further embodiment, the device has a plurality of fans, which are arranged on the longitudinal members. Preferably, each side member has at least one fan which generates a defined air flow radially inward.

This embodiment is advantageous because the fans thermally stabilize the side members. On the other hand, since the longitudinal members serve to hold the cross members in the defined longitudinal spacing, this configuration advantageously contributes to reducing thermally induced stresses. This embodiment is particularly advantageous in combination with a floating screen and / or floating light modules, because then the stability in the longitudinal direction is ensured mainly by the directly cooled side members. The fans suck in fresh cooling air from the outside and blow it out via the light modules. Preferably, the fresh cooling air is sucked in via air filters in order to avoid the injection of dust particles into the device. Alternatively, the fans could suck in fresh cooling air via the light modules and blow out the warm exhaust air. However, the sucking and blowing in of the fresh cooling air is preferred because it produces a positive side effect of a continuous cleaning of the device by blowing existing in the device dirt particles are discharged to the outside.

In a further embodiment, the side members form a substantially closed envelope, which is arranged approximately concentrically with the ground glass.

This embodiment is also very advantageous in order to enable a thermally stable and largely stress-free construction of the new device. The longitudinal members form a closed shell, which allows a defined and aerodynamically optimized cooling air flow past the hot light sources.

In a further embodiment, the cross members are arranged vertically one above the other.

In this embodiment, the new device includes a "standing tunnel" or a tunnel-like column which forms the inspection space. The supply of objects in the inspection room can advantageously from below or by a lateral access. Alternatively, the new device can be realized with a "horizontal" tunnel and also with a longitudinally open tunnel. The latter is advantageous if the test object and / or the at least one camera are arranged on a robot arm which can travel along the open tunnel longitudinal side. In contrast, a standing tunnel allows a very compact device with a small "footprint". In addition, a standing tunnel is also advantageous for efficient cooling, in particular if the individual light modules have cooling fins extending in the longitudinal direction, because in this case a chimney effect occurs.

In a further embodiment, the device has a transverse bar on which the at least one camera is arranged, wherein the transverse bar is arranged in the longitudinal direction outside of the tunnel-shaped inspection space. In preferred variants, the transom is attached to one of the cross members. Advantageously, the cross member has a plurality of prepared mounting positions to which the crossbar can be attached. On the one hand, this embodiment enables a variable viewing angle of the camera in the tunnel-shaped inspection space. On the other hand, it allows easy replacement of the ground glass in the longitudinal direction.

In a further embodiment, the at least one camera has an optical axis which is arranged substantially perpendicular to the longitudinal direction. In one embodiment, the apparatus has a plurality of cameras, one of which faces the inspection space perpendicular to the longitudinal direction. This camera may advantageously be a line camera if the workpiece holder allows a rotational movement of the object about an axis parallel to the longitudinal direction. The latter is particularly preferred when the line scan camera looks through a narrow slot between the light sources into the inspection space.

These embodiments allow a very fast and flexible recording of images of the surface to be inspected with the light-dark pattern.

In a further embodiment, the device includes at least one end plate, which the tunnel-shaped inspection space in the longitudinal direction closes, wherein the end plate has a directed into the inspection space inside, which is adapted to produce a further pattern with light and dark areas. The inside of the end plate may be provided with mirrors which reflect a light-dark pattern generated by means of the light sources on the surface to be inspected. Alternatively or in addition to this, the inside can be provided with further light sources which can be activated individually or in small groups. In principle, the inside can also be printed with a defined light-dark pattern, which is illuminated by means of the existing light sources. These embodiments are advantageous for allowing inspection of surfaces that are substantially transverse or nearly parallel to the longitudinal direction of the inspection space. The end plate therefore simplifies a quick and comprehensive inspection of arbitrarily shaped objects.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Exemplary embodiments of the invention are illustrated in the drawing and will be explained in more detail in the following description. Show it:

1 is a perspective view of a preferred embodiment of the new device,

2 shows the device from FIG. 1 in a view from obliquely behind, with some parts being omitted for reasons of clarity, FIG.

Fig. 3 is an enlarged detail view of the device of Figs. 1 and 2, and

Fig. 4 is a perspective view of a light module, which is used in the apparatus of Fig. 1. In Figs. 1 to 3, a preferred embodiment of the new device is designated in its entirety by the reference numeral 10. The device 10 is realized here in the form of a "standing tunnel" or in the form of a column with a vertical, tunnel-shaped inspection space. Deviating from this, the device 10 may be realized in other embodiments with a "horizontal tunnel" or with an extending in the horizontal direction inspection space. It is also conceivable to realize the tunnel-shaped inspection space with the help of two or more pincers, which can be opened and closed. Such an embodiment is particularly advantageous if the tunnel-shaped inspection space is to be closed all around. In the illustrated embodiment according to FIGS. 1 to 3, however, the "vertical tunnel" is open at the top and bottom. Furthermore, the device 10 here has a lateral access to the inspection room.

The device 10 has an upper cross member 12 and a lower cross member 14. The cross member 12, 14 are here C-shaped with an arc length of slightly more than 180 °. The cross members 12, 14 are held by a plurality of longitudinal members 16 in a defined longitudinal distance D, which defines a longitudinal direction 17.

In the present embodiment, the longitudinal members 16 are rectangular metal plates. The plurality of metal plates has an upper opening 18, a central opening 20 and a lower opening 22. The central opening 20 is circular here and serves for mounting a fan 24. The upper and lower openings 18, 22 are here approximately rectangular. The fans 24 draw cold fresh air from the outside (preferably by an air filter, not shown here, which is mounted over the fan 24) and blow them as cooling air through the central opening 20 in the device 10 a. The openings 18, 22 serve as outlet openings, through which the warm exhaust air reaches the outside again. The fans 24 thus generate a defined air flow, which allows efficient cooling of the light sources described below. The efficient cooling is supported here by the plate-shaped design of the longitudinal members 16, since the closed plate portions of the side members 16 form a substantially closed shell 26 which is arranged approximately concentric with the tunnel-shaped inspection space (Fig. 3). According to a particularly preferred implementation, each longitudinal member 16 below the upper opening 18 and above the lower opening 22 still each have a mounting plate 28. In the preferred embodiments, an upper (not shown here) and lower air guide plate 30 is mounted on the mounting plates 28, which separates the cool supply air and the heated exhaust air from each other. The side members 16 thus fulfill an advantageous dual function here. They are on the one hand mechanically connected to the cross members 12, 14 to hold the cross member 12, 14 fixed in the defined longitudinal distance D. The cross members 12, 14 and longitudinal members 16 may be welded together or, as here, be bolted together. In addition, the plate-shaped side members 16 limit the flow channel for the cooling air and exhaust air.

The cross members 12, 14 each have a largely circular segment-shaped cutout 32. In the preferred embodiment, the C-shaped cross members 12, 14 are formed exactly circular, that is. Accordingly, the outer circumference of the cross members 12, 14 here concentric with the circular segment-shaped cutout 32. Circular segment-shaped cutouts 32 are advantageous to hold the designated by reference numeral 34, translucent ground glass in a defined orientation. The ground glass 34 forms the tunnel-shaped inspection space 36. In principle, however, it is conceivable to realize the tunnel-shaped inspection space 36 with a cross section which deviates from an exact circular shape or from a circle segment. The inspection space 36 could, for example, have a polygonal cross section or an elliptical cross section.

As can be seen in Fig. 1, the plate-shaped side members 16 are arranged in the illustrated embodiment largely concentric with the tunnel-shaped inspection space 36. In other words, the longitudinal members 16 are arranged at a defined radial distance from the circular segment-shaped cutouts 32, wherein the radial distance is indicated in Fig. 1 at reference numeral 38. The radial distance is here related to the longitudinal central axis 40, which intersects the center of the circular segment-shaped cutouts 32. In the illustrated embodiment, the circular segment-shaped cutouts 32 are aligned along the longitudinal central axis 40. Between the ground glass 34 and the longitudinal members 16, a plurality of light modules 42 is arranged. As shown in Fig. 4, each light module 42 here has a self-rigid and self-supporting metallic support body 44 having a front side 46. At the front 46 a plurality of light sources 48 are arranged. In the preferred embodiment, the light sources 48 are arranged on a flexible carrier film 47, as is commonly used for the realization of flexible printed conductors, such as for the electrical connection of folding notebook displays. The carrier film 47 is adhesively bonded directly to the front side 46 of the carrier body 44 with a thermally conductive adhesive. The light sources are thus given their defined orientation only by the inherently rigid support body. In preferred embodiments, the entire front surface 46 of each light module 42 is uniformly covered with light sources 48 having mutually equal lateral spacings. The light sources 48 are here arranged in a matrix which includes four columns in the longitudinal direction 17 and sixty-four lines transversely thereto. In the presently preferred embodiment, the light sources 48 are white LEDs attached to the carrier film 47. Four LEDs each, which form the corner points of a square, are combined into a 4-tuple 49. The LEDs 48 in each 4-tuple 49 are electrically connected in series and thus only jointly controllable, so that they act as a virtual light source with a four times higher light intensity. The series connection is preferred over a likewise possible parallel connection, because then all the LEDs of a 4-Tupels 49 are flowed through by the same stream and as a result shine uniformly bright. The 4-tuples 49 are arranged in two parallel rows 50, 51 which extend over the length LL 'of the light modules 42. Within the two rows 50, 51 each 4-tuple 49 can be controlled individually. Likewise, the 4-tuple 49 of different rows 50, 51 are separately controllable. Advantageously, the LEDs 48 can not only be switched on and off, but also be changed in their brightness from 0% to 100%.

In the preferred embodiments, each light module has two separate power supplies 52. The 4-tuples 49 of each row 50, 51 are alternately connected to one or the other power supply so that two adjacent 4-tuples 49 are each connected to different power supplies. In other words, the 4-tuples 49 of the two rows 50, 51 are in two This is advantageous for creating checkerboard-like chiaroscuro patterns that are particularly suitable for certain surface inspections.

On the back 53 of the carrier body 44, a number of cooling fins 54, 56 are formed, which extend here over the entire length L-L 'of the light modules 42. In the illustrated exemplary embodiment, each light module 42 has three cooling fins, wherein an outer (lower) cooling fin 56 has a larger surface area than the two adjacent cooling fins 54. The cooling fin 56 thus protrudes radially outward beyond the cooling fins 54. On the cooling fin 56, a conventional circuit board 58 is arranged, advantageously on a thermally conductive paste. The control electronics include, among other things, the two separate voltage sources 52 and a microprocessor 60 with associated memory 61. The memory 61 here contains a zero-voltage-safe memory in which, inter alia, a plurality of pattern fragments are stored in a predefined manner can. The pattern fragments of all light modules 42 complement each other to a defined overall pattern, which can be generated by means of the light sources 48 on the ground glass 34. In other words, the pattern fragments in the memories 61 represent the drive information that each individual light module 42 requires in order to control the light sources 48 in each case in such a way that a defined overall pattern results on the ground glass 34. Advantageously, each light module 42 has a bus connection, via which the pattern fragments can be loaded into the memories 61. Furthermore, it is advantageous if each light module has an additional, separate control line 63, which is designed to generate a trigger signal for the sequential switching through of the different pattern fragments in the memory 61. The provision of a separate control line 63 enables a uniform, synchronous "hardware trigger" for simultaneously switching over the pattern fragments of all the light modules 42, which is advantageous for changing very quickly between different patterns.

Furthermore, it is advantageous if individual calibration data for each light module are stored in the zero-voltage-safe memory. With the help of such Calibration data, the radiation intensity of all light modules 42 can be easily adapted to each other, which contributes to very uniform patterns. In addition, at least one temperature sensor 65 is preferably arranged on the front side 46 of the carrier film 47 between the light sources 48. The temperature sensor 65 serves to avoid a thermal overload of the light modules. In addition, it is advantageously used for online calibration of the light modules 42.

The carrier film 47 here has two integral tabs 66, which are guided via the upper cooling rib 54 to the circuit board 58. The integral tabs 66 include printed conductors (not shown here for reasons of clarity), with which the light sources 48 are connected to the control electronics.

Each light module 42 has an upper end 62 and a lower end 64. At the ends 62, 64 here each screw 67 are arranged, by means of which the light modules 42 can be attached to the cross members 12, 14. Fig. 3 shows in an enlarged view how the light modules 42 are mounted in the preferred embodiment by means of the screw 67. In the preferred embodiment, the light modules 42 are floating on the cross beams 12, 14 in the longitudinal direction 17, i. the light modules 42 can expand or contract in the longitudinal direction 17, without resulting in mechanical stresses within the device 10. This is advantageously achieved here by a fixed bearing and a movable bearing in the longitudinal direction 17.

As can further be seen in FIG. 3, the cooling ribs 54, 56 form cooling channels which run parallel to the longitudinal direction 17 and expand radially from the inside to the outside. The cooling channels are radially outwardly covered by the shell 26, which generates a defined air flow through the openings 18, 20, 22 with the aid of the fan 24. In a preferred exemplary embodiment, cooling air outlets 68 are also arranged in the cross members 12, 14. The cooling air outlets 68 are advantageously arranged directly above the cooling ribs 54, 56.

As can be seen further with reference to FIG. 3, a number of retaining clips 70 are arranged on the cross beams 12, 14, which in the present case are arranged around the respective kreissegmentfbrmigen cutout 32 are distributed. The retaining clips 70 here are U-shaped elements which are designed to fix the ground-glass screen 34 in an exchangeable manner. In the exemplary embodiment illustrated here, the ground glass 34 can be inserted tangentially from the lateral opening of the inspection space 36 into the retaining clips 70. In the preferred embodiment, the ground glass 34 is a flexible plastic sheet of Plexiglas. In another embodiment, the ground glass consists of a full-volume, translucent, but opaque PTFE material. It could also be another, preferably frosted glass-like plastic plate. The plastic plate is brought by insertion into the retaining clips 70 in the circular shape of the cutouts 32. The inner material tension of the plastic plate pushes the ground glass 34 radially outward, so that the ground glass 34 is held in a radially fixed position by means of the cross members 12, 14 and the retaining clips 70. Tangentially, the focusing screen 34 can expand or contract. Furthermore, the retaining clips 70 offer a certain play in the longitudinal direction 17, so that the ground-glass screen 34 is also floating in the longitudinal direction in the present exemplary embodiment.

Reference numeral 72 designates in FIG. 3 a transverse bar on which a camera 74 is arranged. Another camera 74 'may be disposed on another beam 76. The cameras 74, 74 'are in a preferred embodiment surface cameras, ie cameras with a sheet-like image sensor with a plurality of pixels arranged in a matrix. In a preferred embodiment, the device 10 also has another camera 78 disposed in a housing on the back of the device 10. The camera 78 in the preferred embodiment is a line scan camera with a cellular image sensor. The optical axis 80 of the line scan camera 78 is arranged here exactly perpendicular to the longitudinal central axis 40. Likewise, the optical axis 80 of the camera 74 'here transversely, but not necessarily exactly perpendicular to the longitudinal central axis 40 of the device 10. In contrast, the camera 74 here looks approximately parallel to the longitudinal center axis 40 from the outside into the tunnel-shaped inspection space 36th Die Kamera 74, 74 'are advantageously pivotable, so that the viewing direction in the inspection space 36 can be varied. As further illustrated in FIG. 3, the crossbar 72 is secured to the cross member 12 outside of the inspection space 36. In the embodiment shown here, the cross member 12 has predefined mounting positions for the crossbar 72 and the camera 74 is displaceable along the crossbar 72. The predefined, indexed mounting positions for the crossbar 72 allow for easy assembly and disassembly of the camera 74, for example, to replace the focusing screen 34 or for other reasons. Due to the indexed mounting positions, the camera 74 can be quickly returned to its original position. It is also conceivable that the position and viewing direction of the cameras 74, 74 'is varied by means of a robot on which the cameras 74, 74' are mounted.

The reference numeral 82 in Fig. 3 denotes an end plate which can be secured in preferred embodiments in the cutout 32 of the cross member 12 in order to close the tunnel-shaped inspection space 36 upwards. A corresponding end plate 82 may be mounted at the lower end of the inspection space 36. In one embodiment, the end plate 82 at the lower end of the inspection space 36 may be formed by a workpiece holder on which the object to be inspected is placed. The workpiece holder (not shown in detail here) can advantageously be arranged on a lift 84, with which the object to be inspected can be transported from below into the inspection space 36.

The end plate 82 at the top of the inspection room 36 here has an aperture 86 through which the camera 74 can look into the inspection space 36 when the end plate 82 is secured to the cross member 12. In preferred embodiments, the inner side 88 of the end plate 82 is mirrored or provided with light sources 48 (not shown here).

As shown in FIG. 1, the device 10 is configured to generate a light-dark pattern 90 on the ground glass 34 with the aid of the light sources 48. For reasons of clarity, the pattern 90 in FIG. 1 is only partially indicated. An evaluation and control unit, which controls the light sources 48 and the cameras 74, 78, is shown at reference numeral 92 in FIG. It is understood that the Evaluation and control unit 92 can also be realized separately from the mechanical arrangement with the cross members 12, 14 and the longitudinal members 16. In particular, a PC with suitable interface hardware for controlling the light sources 48 and cameras 74, 78 and possibly for driving the lift 84 can be used as the evaluation and control unit 92.

In the preferred exemplary embodiments, the evaluation and control unit is designed to generate, with the aid of the light sources 48, a light / dark pattern 90 on the ground glass 34, which contains a sinusoidal brightness profile. Furthermore, the evaluation and control unit 92 is designed to move the light-dark pattern 90 with the sinusoidal brightness profile relative to the surface to be inspected. This can be done either by suitable control of the light sources 48 electronically and / or by a mechanical movement of the object to be inspected. The latter can be advantageously realized by means of a workpiece holder, which is rotatable about the longitudinal axis 40 (not shown in detail here).

In the preferred embodiments, the light-dark pattern includes 90 stripes that are shifted transversely to the strip direction. The evaluation and control unit 92 is designed to evaluate a plurality of images of the surface to be inspected with the (relative thereto) shifted stripe patterns 90. Through phase reconstruction based on the images, the local inclinations of the surface to be inspected can be determined. A particularly preferred method for evaluating the images is described in the German patent application DE 10 2007 063 530.5, to which reference is made in its entirety. Furthermore, it is advantageous if the evaluation and control unit 92 is designed to generate a plurality of superimposed stripe patterns simultaneously, as described in the PCT application with the file reference PCT / EP 2008/005683, to which also here is fully referenced.

As can be seen with reference to FIGS. 1 to 3, the cross members 12, 14 are largely identical in the illustrated embodiment, but mirror-inverted to each other mounted on a frame 94. The frame 94 allows easy loading of the inspection space 36 from below by means of the lift 84. In a preferred In the exemplary embodiment, the lift 84 is connected to a conveyor belt (not shown here) via which objects to be inspected are automatically fed. In principle, it is conceivable to design the device 10 such that for each object to be inspected or for each type of object to be inspected, an individual ground glass 34 is manually or automatically inserted into the cutouts 32. In this case, the light-dark patterns 90 can be printed on the ground glass used 34 or otherwise permanently applied. The light-dark patterns 90 are then "activated" by uniform illumination with the aid of the light sources 48.

Furthermore, it is conceivable that the light sources 48 are realized with the aid of organic LEDs, so-called OLEDs. Furthermore, mirrors may be arranged within the inspection space 36 and / or at the bottom, in order, for example, to make visible undercuts on objects to be inspected for the cameras 74, 78.

Claims

claims

1. A device for optically inspecting an at least partially shiny surface on an object, with

- A first and at least one second cross member (12, 14), each forming a largely kreissegmentfδrmigen cutout (32), wherein the transverse beams (12, 14) at a longitudinal distance (D) are arranged to each other, which defines a longitudinal direction (17) .

- A number of longitudinal members (16) holding the first and second cross member (12, 14) in the longitudinal distance (D), wherein the longitudinal members (16) are arranged at a defined radial distance (38) to the circular segment-shaped cutouts (32) .

- a translucent ground glass (34) held by the transverse beams (12, 14) in the circular segment-shaped cutouts (32) to form a tunnel-shaped inspection space (36),

- A plurality of light sources (48), which are outside the tunnelformigen inspection space (36) behind the ground glass (34) and individually or in small groups can be controlled to variable light-dark pattern (90) on the ground glass (34) produce,

- A workpiece holder (84 for the object in the tunnelformigen

Inspection room (36),

- At least one camera (74, 78) which is directed into the tunnel-shaped inspection space (36), and an evaluation and control unit (92) which is adapted to the light sources (48) and the camera (74, 78) to control to produce different light-dark patterns (90) on the ground glass (34) and by a Record and evaluate a variety of images of the object in dependence on the light-dark patterns (90).

2. The apparatus of claim 1, further comprising a plurality of mutually identical light modules (42) disposed between the ground glass (34) and the longitudinal beams (16), each light module (42) having a plurality of the light sources (48).

3. Device according to claim 2, wherein the light modules have a metallic carrier body (44) having a length (L-L ') which is approximately equal to the longitudinal distance (D), wherein the carrier body (44) has a front side (46) on which the light sources (48) are arranged, and a rear side (53) on which cooling fins (54) are formed.

4. Apparatus according to claim 2 or 3, wherein the light modules (42) in the longitudinal direction floating on the cross beams (12, 14) are mounted.

5. Device according to one of claims 2 to 4, wherein each light module (42) has two longitudinally parallel rows (50, 51) of light sources (48) which are separately controllable.

6. Device according to one of claims 1 to 5, wherein the light sources (48) each having the same radial distances from the ground glass (34) are arranged.

7. Device according to one of claims 1 to 6, wherein the ground glass (34) is a frosted glass-like ground glass.

8. Device according to one of claims 1 to 7, wherein the ground glass (34) on the cross beams (12, 14) is mounted floating.

9. Device according to one of claims 1 to 8, wherein the cross member (12, 14) retaining clips (70) which are adapted to fix the ground glass (34) interchangeable.

10. Device according to one of claims 1 to 9, further comprising a plurality of fans (24) which are arranged on the longitudinal members (16).

11. Device according to one of claims 1 to 10, wherein the longitudinal members (16) form a substantially closed envelope (26) which is arranged approximately concentrically with the ground glass (34).

12. Device according to one of claims 1 to 11, wherein the cross member (12, 14) are arranged vertically one above the other.

13. Device according to one of claims 1 to 12, further comprising a transverse bar (72) on which the at least one camera (74) is arranged, wherein the transverse bar (72) arranged in the longitudinal direction (17) outside of the tunnel-shaped inspection space (36) is.

14. Device according to one of claims 1 to 13, wherein the at least one camera (78) has an optical axis (80) which is arranged substantially perpendicular to the longitudinal direction (17).

15. Device according to one of claims 1 to 14, further comprising at least one

End plate (82) which closes the tunnel-shaped inspection space (36) in the longitudinal direction (17), wherein the end plate (82) one in the

Inspection space (36) directed inside (88), which is adapted to produce a further pattern with light and dark areas.