DE10063293A1 - Multi-channel inspection of moving surfaces involves synchronizing two radiation sources with image generation frequency of image acquisition device to alternately illuminate surface - Google Patents

Abstract

The method involves exposing the surface to radiation with a first characteristic from a source in a first alignment to the surface and acquiring an image, exposing the surface to radiation with a second characteristic from a second source with a second alignment and acquiring a second image acquired and determining information based on both images. The sources are synchronized with image acquisition device and alternately illuminate the surface. The method involves using an image acquisition device (106) and at least two radiation sources (102,104). The surface (118) is exposed to radiation with a first characteristic from one source in a first alignment to the surface and an image acquired, the surface is exposed to radiation with a second characteristic from a second source with a second alignment and a second image acquired and surface information is determined based on both images. The sources are synchronized with the image generation frequency of the image acquisition device and alternately illuminate the surface. An Independent claim is also included for an arrangement for multi-channel inspection of moving surfaces.

Description

The present invention relates to a method and an automatic inspection device itself moving surfaces; in particular on a procedure and a device for acquiring multi-channel information of surfaces with the help of just one camera taking pictures with one of the feed speed of the inspected Surface controlled frame rate is generated, and at least two radiation sources that alternate the surface to shine.

The automatic inspection of surfaces is generally mean a "multisensory task". Under a "multi sensory "arrangement is first understood to be a setup device in which sensors of different quality are involved are, e.g. B. in the tile test a sound analysis and egg ne image analysis. However, measuring arrangements are also multisensory conditions with multiple cameras, e.g. B. a camera for Hellfeldbe lighting and a second for dark field lighting.

With automatic inspection of surfaces one would like z. B. Information about color, gloss and three-dimensional egg properties (elevations or depressions) of the surface determine. That is with a single light source and one single camera not possible. Man also has to careful inspection of a surface from different Look at the specimen to see all kinds of directions  To be able to recognize defects. To do this, move more normally instruct the examinee during the observation.

Technical means are used to solve demanding tests tasks (such as the inspection of steel strips or tiles) this problem usually so that you have several (at least two) Set up test stations, e.g. B. a first with dark field lighting for assessing the color of the test object and a second to assess the gloss or the height pro fils. Such a test is e.g. B. in EP 0 898 163 A. described. This method has the disadvantage that the images from the different test stations are not exact match each other - they are adjusted with different cameras different positions added. A direct assignment the information from the different pictures in small it is not possible (at the pixel level). That would but e.g. B. for the classification of small defects very much advantageous.

Systems for automatic inspection of surfaces are known and used in industrial applications such as B. in the inspection of steel and wood surfaces or of tiles. Such products are typically used at high speeds in a continuous process manufactured and must be checked continuously. The too investigating properties of the surface relate usually on color, texture, gloss and the three dimensions sional dimensions. In the past, the Mes solution of the color and the acquisition of the three-dimensional in formation by means of separate measuring devices at different Places. Because of this approach, the exact assignment z. B. of color information and three-dimensional naler information difficult. The exact assignment is however  for improved analysis of the examined products sticky and desirable.

In the prior art, line cameras are preferably used for the inspection of moving surfaces. Compared to matrix cameras, line scan cameras offer the following advantages:

• - Simple facilities for homogeneous illumination the measuring line,
• - Easy handling of variable feed speeds, and
• - Flexible adaptation of the image formats to the geometry of the test item (general cargo or sheet goods).

The currently known color-efficient line scan cameras have ty typically a length of approx. 2000 pixels with Zei Len rates of up to 10,000 lines per second. With such Cameras can be color images according to the state of the art high quality of moving surfaces. As well State of the art is the detection of the height profile of Textured light surfaces. Information about Far be and height profile, however, so that these pass exact match is not common. Especially not for the inspection of surfaces in continuous operation.

WO 99/58930 A describes a device which based on triangulation with structured light and also Provides color information about the object. The object will alternate with struktu from the same direction light as well as with homogeneous white light tet. In order to carry out a three-dimensional measurement up to four pictures taken with a matrix camera. The Method is particularly for measuring three-dimensional  Objects, such as B. of humans or animals. For the automatic inspection of (essentially ebe surfaces in the pass it is not very suitable.

M. Gökstorp and K. Gunnarsson describe in their article "CMOS Sensors: Smart Sensors yield fast and robust machine vision" in Laser Focus World, USA PennWell Publishing 36 : 101-103, No. 2, February 2000 an application of a 512 × 512 Pixel CMOS matrix camera, in which color and height information are recorded simultaneously. The sensor contains processing circuits with which rows of the sensor can be addressed and processed separately. Certain lines of the matrix sensor are used to record color information from the test object. Additional lines of the matrix sensor are used to detect a laser profile, which is used for height measurement. The color and height measurements are obtained from different locations on the object. There is no direct match between the two types of information.

DE 196 04 076 A1 describes the extraction of information about the color of a surface (wood), the height profile and the density of the material (via the tracheid effect). here is the surface by a laser scanner with tele centric beam path illuminated. By combining Lasers of different wavelengths can be multicolored generate a (e.g. white) light spot. By observation direction of the illuminated surface elements over the beam lighting path (with several photo sensors) wins to get a color picture of the surface. By observing the be shone surface elements over a second beam path that is inclined to the first beam path,  information about the height profile is obtained simultaneously the surface (triangulation method).

The disadvantage here is that the measurement setup a number of contains special optical and mechanical components (poly gon mirror, parabolic mirror, gradient filter,. , .). Dement speaking, the measuring apparatus is difficult to move adapt applications (e.g. to different In inspection width or different angular relationships for triangulation). In addition, the measuring apparatus hardly any further "information channels", in particular not a transmitted light channel.

Starting from the prior art described above is the object of the present invention improved method and an improved device for automatic multi-sensor inspection of surfaces to create, being from the different sensor channels Information obtained (e.g. about color and height profile of the Surface) is precisely related to each other.

This object is achieved by a method according to claim 1, by a device according to claim 12, and by a ver drive solved according to claim 24.

The present invention provides a method for the automatic inspection of moving surfaces ( 118 ) using an image capture device ( 106 ) that generates images with a predetermined or a given image generation frequency determined by the feed of the test object, and at least two radiation sources ( 102 , 104 ), the method comprising the following steps:

• - Irradiating the surface ( 118 ) with a radiation from a first radiation source ( 102 ) which is arranged with respect to the surface ( 118 ) in a first geometrical direction, the radiation having a first characteristic;
• - capturing a first image from the surface ( 118 );
• - Irradiating the surface ( 118 ) with radiation from a second radiation source ( 104 ) which is arranged with respect to the surface ( 118 ) in a second geometric direction, the radiation having a second characteristic;
• - capturing a second image from the surface ( 118 ); and
• - determining properties of the surface ( 118 ) based on information from the first image and from the second image;
• - The first radiation source ( 102 ) and the second radiation source ( 104 ) are controlled such that they are synchronized with the imaging frequency of the image capture device ( 106 ) so that the first radiation source ( 102 ) and the second radiation source ( 104 ) alternately irradiate the surface ( 118 ).

The present invention provides an apparatus for the automatic inspection of moving surfaces, comprising:

• - a first radiation source ( 102 ) which emits radiation with a first characteristic onto the surface ( 118 ) and which is arranged in a first geometric arrangement with respect to the surface ( 118 );
• - A second radiation source ( 104 ) which radiates a radiation with a second characteristic onto the surface ( 118 ) and which is arranged in a second geometric orientation with respect to the surface;
• - An image capture device ( 106 ) that generates images of the surface ( 118 ) with a given image capture frequency;
• - A control unit ( 108 ) which is operatively connected to the first radiation source ( 102 ), the second radiation source ( 104 ) and the image capture device ( 106 ), and which has the first radiation source ( 102 ) and the second radiation source ( 104 ) the image generation frequency of the image generating device ( 106 ) synchronized such that the first radiation source ( 102 ) and the second radiation source ( 104 ) alternately irradiate the upper surface ( 118 ) to alternately an image of the surface ( 118 ) based on the irradiation by the first Generating the radiation source ( 102 ) and an image of the surface ( 118 ) based on the radiation from the second radiation source ( 104 ); and
• - An evaluation device that determines the surface ( 118 ) based on information of the alternately generated surface properties.

The present invention also provides a method for multisensorial inspection of moving surfaces with a multi-channel sensor device that generates images from the surface, each of the images generated providing information about the surface in at least one channel of the multi-channel sensor device, the multi-channel sensor device at least two images generated under different irradiation conditions, the multi-channel sensor device alternately generating the images synchronously with an image generation cycle.

In one embodiment, the multi-channel sensor is a single color camera, and the Surface is covered by at least two lighting devices to generate multi-channel images of the surface che illuminated, the light sources being time-division multiplexed driven and synchronized with the recording clock of the camera can be switched alternately, with the light sources additionally can be distinguished by their color (R, G, B) and the number of distinguishable sensor channels Product of the number of timeslots and the number of There are color separations, with each sensor channel a Kombina tion from the camera and a light source and whereby by design and geometric arrangement of Light sources in the various sensor channels Information different types can be detected over the surface can, the information from the various sensors neln is related to each other.

The aim of the present application is to obtain multisen sorial information of surfaces (especially color and height profile) in such a way that even in small (on picture point level) an exact assignment of the detailed information  (in particular of height measurements and color image) is possible. The measuring apparatus should be easy to implement and thus compared to the prior art (arrangements with several Cameras) not only technical, but also economical Offer advantages.

This is achieved according to the invention in that preferably only a single (color proof) camera is used, however several lighting devices. With every combination Camera / lighting becomes another sensor (sensor channel) realized, e.g. B. a first sensor for recording a Color image with white diffuse lighting and a second Sensor for obtaining height information with the help of structured light. The lighting devices will synchronous to the image recording frequency of the line scan camera (e.g. 10 kHz) switched alternately. One operates the "sensors" So in time division multiplex.

The color line camera used is more accurate Look at a three-channel sensor. It delivers simultaneously three separate pictures, the red extract, the green extract and the blue separation of the color image. Which operated in time division bene color camera with multiple lighting devices can therefore also be understood as a six-channel image sensor - the camera is used twice by time division (two Time slots), with three channels (R, G, B) are available. This is of course expandable even on more than two time slots.

According to a preferred embodiment of the present According to the invention, the imaging sensor is a line scan camera or a matrix camera, and the first radiation source is a light source that produces homogeneous white light.  

The second radiation source is a light source, which structured monochrome light is generated, e.g. B. the color red.

In this embodiment, the camera in Time division multiplexing creates two images simultaneously: a first image due to the lighting with homogeneous white light, the contains information about the color of the surface and a second picture due to the lighting with textured tem (red) light that contains the height information. The Both light sources are synchronized with the line frequency flashed alternately by the camera. So the two bil the related to each other in the line direction, in front push direction but by a line spacing from each other added. This offset in the direction of feed disturbs in space not mean. In the event that another improved Fitting accuracy in the feed direction is desired, it leaves itself by interpolation between the lines of one of the reach the pictures. So you get through the invent method according to the invention and the device according to the invention two precisely matched images of the surface che, in which exactly assigned information about color and Height of the surface elements is included. As a profit Compared to the prior art, this is a reliable A closer analysis of the surface properties is possible.

According to a preferred embodiment of the present the approach of the invention is to a single line scan camera and at least two pulsed ones Light sources to use multiple channels of information record such. B. Color and height information. The Light sources are synchronized with the line frequency of the Line scan camera pulsed.  

The advantage of the present invention is that this enables different information modalities with only one egg regarding the surface to be examined a single camera. Another advantage be is that this information, which is given under different lighting channels were obtained, a perfect fit are related to each other, yet another advantage is that the inventive solution for the In surface inspection in a continuous process is suitable. On Another advantage is that only standard components (like cameras and LED lamps) and no moving parts are necessary for the implementation of the method.

In the case of the present application, under "Sensor" not the imaging sensor in the narrower sense (the camera) alone, but the combination camera / lighting understood the. With pictures from a color camera one speaks i. a. of "three-channel" pictures (R, G, B), generally from multi-channel pictures. A well-known example is the multispek central images from satellites.

Preferred developments of the present invention are defined in the subclaims.

Below will be with reference to the accompanying drawings preferred embodiments of the present invention explained in more detail. Show it:

Fig. 1A is an illustration of the invention Vorrich processing according to a first embodiment,

Fig. 1B is a schematic diagram for explaining the process of the invention,

Fig. 2 is an illustration of the picture line the contents of a line scan camera,

Fig. 3 is a schematic representation of the Bildzeilenin halts a line camera in the embodiment of FIG. 1,

Fig. 4 shows a second embodiment of the erfindungsge MAESSEN device,

Fig. 5 shows a third embodiment of the device according to the invention, and

Fig. 6 shows a fourth embodiment of the device according to the invention.

In Fig. 1 a first embodiment of the device according to the inven tion is shown, which is provided in its entirety with the reference numeral 100 .

The device 100 comprises a first light source 102 , a second light source 104 and a color line camera 106 . Furthermore, a processing unit 108 is provided, which comprises a processor 110 , a control unit 112 and a frame reading unit 114 .

The first light source 102 never illuminates an examination line 116 of a surface 118 that moves in the direction of the arrow 120 . A displacement sensor 122 is provided to output a position signal corresponding to the position of the moving surface. As shown schematically at 124, surface 118 is three-dimensionally curved.

The first light source 102 and the second light source 104 are connected to the control unit 112 of the processing unit 108 via a control line 126 . The control unit 112 also detects the output signal of the encoder 122 , with which it is connected via a line 128 . Furthermore, the control unit 112 is connected to the frame reading device 114 , which in turn is connected to the camera 106 via the connecting lines labeled R, G and B. The frame readout unit 114 , under the control of the processor 110, reads out the three frames generated for the red, green and blue video signals by the camera for each imaging cycle.

As shown by the dashed lines emanating from the camera 106 , this produces an image of the examination line 116 from the inspected surface 118 .

The first light source 102 is arranged such that it emits essentially diffuse light onto the examination line 116 . The second light source 104 emits directed, structured light onto the examination line 116 at an angle with respect to the surface. The light fan of the light source 104 and the receiving fan of the line camera 106 are in the same plane.

Fig. 1A illustrates a general overview of the device according dung OF INVENTION The main components are in this embodiment, the color-efficient Zei steering using the camera 106 with the three color channels, R, G, B. two or more light sources 102 , 104 , which are operated in a pulsed manner in order to measure different modalities of the examined surface or the examined object, and the control unit 112 , which synchronizes the line-by-line image acquisition with the pulsed activation of the light sources 102 and 104 .

The line camera 106 is arranged such that it "sees" the examination line 116 , which extends perpendicular to the direction 120 of the movement of the object. Because of the control 112 , the examination line 116 is alternately illuminated by two or more light sources in a cycle of two or more time slots.

The cycle of the time slots and the associated clocking of the lighting, like the reading of the camera 106 , is controlled by the control unit 112 , either according to the movement information from the travel sensor 122 , or according to a constant rate. The frame reading device 114 , which is synchronized with the control unit and with the camera, transmits the data of the captured line image to the processor 110 .

The number of time slots is not limited to two depends on the number of for each measurement necessary sensor channels. A picture can have up to three Color channels include, so that a set of up to three color encoded lighting systems can be used to Different modalities within one time slot of the surface. With a color image (color separations R, G, B) one time slot is fully occupied.

A decisive feature of the present invention is that the information from the different sensor channels is related to one another in a precisely fitting manner. With reference to FIG. 1B, this property is briefly explained for two lighting sets. In FIG. 1B, in the left half, two images 200 and 202 are exemplarily shown, which were recorded by the camera 106 in FIG. 1A in a first time slot and in a second time slot, respectively. After only two lighting sets were available in the example shown, the cycle in this example comprises only two images. As an example, a black spot is shown on the surface in each of the images in FIG. 1B (reference numeral 204 ). The same spot is also present in the second image 202, but this is slightly offset from the first image - due to the further movement of the surface - so that it is provided with the reference symbol 204 '. This offset between the two images is shown in the right-hand side of the figure at reference numeral 206 . It corresponds to a line spacing. For typical application data with a line frequency of 10 kHz and a transport speed of the test object of 3 m / s, the offset is 0.3 mm. If the task requires it, the offset between the two images can be compensated for by interpolating between the lines in one of the two images.

For the first image 200, first information relating to the error 204 based on the selected recording modality is obtained. Due to the second recording modality, further information regarding the error 204 'is obtained in the second image 202. Because of the exact fit of both images, the two sources of information can be used to complement each other. This novel approach, taught by the present invention, enables the improved analysis of the surface properties.

As an example, consider a case where the surface to be examined has an undesirable increase. This increase appears as a spot in the first image 200, but this does not yet allow a reliable decision as to what type of disturbance is present on the surface. Based on the statement regarding image 200, this can be contamination, inclusion of foreign particles or the like. Only the information of the second image 202, for example to obtain height-relevant information, results from the exact fit of the two images that the error in the first image represents an undesirable increase in the surface. The present invention thus enables reliable statements to be made about certain errors.

In Fig. 2 an example of the content of the image lines of a line camera is shown, which is operated with two time slots be. The pixel columns are listed from left to right in FIG. 2 and the rows are listed from top to bottom, as is illustrated by the terms "pixel columns" and "row index". In this example, each time slot contains all of the information that can be read from the camera in Fig. 1A: each time slot contains information from the red, green and blue channels.

As from the above explanation of the present invention it becomes clear that the information of the differ Chen measurement modalities in the time slots both in the time mul tiplex as well as color-coded via the color channels of the camera in front.  

Hereinafter, with reference to FIGS. 1 and Fig. 3 From a management example of the present invention for the height and color measurement explained in more detail. The measurement setup of FIG. 1 can be used to height and color measurements under USAGE dung of two time slots to perform. During the most time slot it is by means of the second light source 104 , which, for. B. is a projector for structured light based on a red diode laser, the upper surface 118 with a line pattern at an angle radiates be. The camera 106 captures an image line in the red channel which contains information about the line pattern. In this example, the green and blue color channels remain unused. During a second time slot, the surface 118 is illuminated with diffuse light by means of the first light source 102 , which is a homogeneous white light source in this exemplary embodiment, in order to obtain a color image on the red channel, the green channel and the blue channel. In Fig. 3 the camera line order resulting from this arrangement is shown. Similar to FIG. 2, the pixel columns are shown from left to right and the lines of the image from top to bottom. As can be seen, the time slot 1 only contains information based on the red channel, and the time slot 2 contains the RGB color information.

The homogeneous lighting consists of one or more light sources that can be pulsed with the line frequency of the line camera. The properties of the lighting device, such as color and geometry, depend on the application. For applications that use color analysis, white light illumination is typically preferred. The projector for structured light (light source 104 ) is arranged in the plane which is never spanned by the optical axis of the camera 106 and the examination line 116 . The distance and the lighting angle of the projector is set in accordance with the desired resolution and the desired range of the height measurement as well as the opening angle and the size of the elements of the projected pattern.

A laser diode module with projection optics is called Structured light projector preferred. As a project manager onsoptik will be a diffractive optic for several lines moves a number of parallel short lines per jiziert. The short projected lines and the subs line of the camera are perpendicular to each other and cut each other. The camera "sees" the intersections as intensity peaks. The positions of the intensity peak zen contain the height information (light section process ren). The dependence of the height information on the positi The tip is calibrated to an object determines which one is a known three-dimensional shape points, e.g. B. an inclined flat plate.

A known problem when using the light section The procedure using structured light is the Kor responder problem, which is a problem of identification of the individual elements of the projected structured Mu sters is. A well-established solution to this problem to solve, is to ha a limited measuring range ben so that every element of structured lighting can be found within a defined framework, which is defined for each element. In practice, a Area that is defined by a minimum and a maximum Ko ordinate value is defined for each element.  

The coordinate area should not be with an adjacent one Overlap area to avoid ambiguity.

Although this limits the range of height measurement, this area can be easily moved, e.g. B. basie rend on a rough height estimate based on Prior knowledge of the shape of the surface to be examined is obtained, or due to another structured Light source, which provides a larger measuring range, however with lower height resolution. These approaches are due to the use of the invention, the Zeitmul tiplex and color coding properties used, easy to implement.

After the present invention accurately registered color and provides height information, the color information used to determine the position of the object under investigation to be determined in the image line. Based on before this can be known about the height of the object Use information to estimate the height of the property. This approach creates a high measurement accuracy over a wide measuring range.

An extension of the measuring range can also be implemented with two time-multiplexed or color-coded illuminations for structured light. Such an arrangement is shown in Fig. 4, which represents the inventive device according to this further embodiment. Similar elements that have already been described with reference to FIG. 1 have the same reference symbols. Ge genüber the embodiment of Fig. 1A, the embodiment shown in Fig. 4 comprises a further, drit te light source 130 which irradiates under a further angle to investigate line 116th The third angle differs from the angle at which the light source 104 emits. The first projector 104 creates a Höhenmes solution with a large measuring range, but a coarse resolution. The second projector 130 creates an improved resolution, but a smaller measuring range. The height information of the first measurement can be used to shift the measuring range of the second measurement.

The local density of the elements of the structured light limits the range of the height measurement. If a higher density is desired, the measuring range is reduced. A solution to increase the density and at the same time to maintain the measuring range is an arrangement with two time-multiplexed or color-coded sources for structured light in almost the same place, so that the two projected patterns are interleaved. FIG. 5 shows such an arrangement, in which, similarly to FIG. 4, elements already described with reference to FIG. 1A have the same reference numerals. In Fig. 5, in addition to the first light source 104 of Fig. 1, a third light source 104 'is provided, the pattern from the light source 104 and the pattern from the light source 104 ' on the measuring line 116 by half a period of the projected Structure are offset from each other. This doubles the number of structural elements on the measuring line and thus increases the local resolution of the measured values for the height measurement.

Another problem with the light section method with structured light is the casting of shadows. If the inclination of the observed surface is close to or exceeds the angle of the structured lighting used, only sparse measuring points are obtained on the inclined surface or even shadowing occurs, as a result of which height measurements are completely absent. A symmetrical structure of two time-multiplexed or color-coded projectors for structured light can be used to avoid this shadow problem. Fig. 6 shows such an arrangement in which, in turn, elements that have already been described with reference to FIG. 1 have the same reference characters. In addition to the second light source 104 , a further light source 132 is provided which illuminates the examination line 116 . The light sources 104 and 132 are arranged symmetrically with respect to the optical axis of the camera 106 .

Depending on the geometry, the camera resolution and the Width of the projected lines of structured light can be the tips of a projected pattern ele be observed, a width of several pixels in the camera sensor. Tips that differ from a homogeneous dif fused surface are in the form of a Gaussian distribution. The position of the tips can be found under Ver avert this assumption with sub-pixel accuracy can be estimated, reducing the accuracy of the altitude measurement is improved. If the surface is not a homogeneous reflect activity at the location of the interface is the Gaussian form disturbed and the position estimate based on the Gaussian form is not exact.

After the color and height information is assigned to fit net, the color information z. B. from before resulting or subsequent color image lines were obtained, in principle used to correct this estimate the. But since the lighting angle of the homogeneous light source and the structured light source different  are due to fluctuating gloss properties of the Different backscattering of light done from these sources, and corrected the spit Zenform appears to be unreliable. Therefore, there is before drafted execution to improve the reliability of the Height measurement in using the color information to to mark such height measurements as unreliable, those in a place with a high gradient of reflectivity were carried out.

In the preferred embodiments described above len of the present invention, was used as an image capture device uses a line scan camera, the image lines synchronized with the feed of the waiter detected by the travel sensor area or with a given line frequency. The Synchronization of the pulsed first and second beams tion sources is such that these with the line frequency the line scan camera are synchronous, so that the radiation source len are alternately pulsed.

Instead of the described embodiments, the one Line scan camera can use the image capture device be realized by a matrix camera, the images syn chron with the feed of the surface detected by the travel sensor or generated at a given frequency. Here too the first radiation source and the second radiation source synchronized with the image change of the matrix camera to egg ne alternating pulsed control of these sources possible.

The above exemplary embodiments were all based on Light sources described as radiation sources, which generate visible light as radiation. In addition to the visible  Light is another type of radiation for examination of surfaces and their characteristics can be used, so that depending on the surfaces to be examined and the admission modality to be applied, e.g. B. transmitted light, also on whose radiation is used as visible light can, e.g. B. infrared radiation.

Furthermore, the above exemplary embodiments were based on a Configuration described in the first time slot all three channels of the line scan camera are used, and in second time slot only one channel, usually the red Channel. However, the present invention is not limited to one limited such application. When using two times slits and a color camera with the 3 channels R, G and B have a total of six "sensor channels" available which can be documented differently depending on the application can. An arrangement with six separate ones would therefore be conceivable Lighting devices (two red, two green and two blue), whereby by arrangement and type of the respective Be different information from the surface is detected. In the above embodiments three channels (one red, one green and one blue light source) combined to form a white light source, around which Determine the color of the surface. Of these three channels a time slot is fully occupied. In the second time slot height information is recorded. Another preferred option The use of the available sensor channels are meas orders with one or more channels for transmitted light, one or more channels for side lighting the objects to be tested and / or a channel for the groove of the "tracheid effect".  

A transmitted light channel is created by arranging a light source, which from the point of view of the camera lies under the test object. Holes and gaping cracks can be seen in transmitted light Detect the surface safely. When testing whole or partially transparent materials such as glass or foils provides the transmitted light channel z. B. Information about A conclusions or fluctuations in the thickness of the test specimen.

A side lighting shines more or more less flat from the side. Under side lighting tion can be z. B. when inspecting tiles Kan Detect faults or when testing wood bark free forest edges.

The tracheid effect occurs with fibrous materials and is characterized by the light crawling through the fibers records. It is particularly useful when inspecting wood surfaces used. To do this, the surface is illuminated a line that is as sharply defined as possible (laser line) across to the direction of transport of the surface and observed with the line camera not the illuminated line itself, but a line running parallel to it at a slight ab was standing. Then you can see dense (e.g. metallic) mate rialien nothing. You can see that with fibrous fabrics light crawling through the fibers. That is quite a lot Light with long-fiber soft wood (softwood) and little with hard wood, especially with branches in softwood. One can also knots in softwood due to this effect recognize that do not stand out in color from the surroundings. In the above-mentioned embodiments, general spoken, six channels of information during the two time period slots provided that depend on the perform individual examination. By extension  the number of Increase sensor channels further.

The method and the device according to the invention are used in addition to other applications also in wood testing, all six information channels of the measuring device being used here. In the first time slot, a color image of the surface is generated in the manner described above by means of a homogeneous white light source. In the second time slot, three light sources, a red, a green and a blue are pulsed simultaneously. The red light source is used to record height information and corresponds to the light source 104 shown in FIG. 1A. The second, green light source illuminates the back of the wood and provides transmitted light information in the green channel of the line camera in the second time slot for the detection of holes and gaping cracks. The blue channel provides information about the density of the material by using the tracheid effect.

This description is an example. In another variant ante you can z. B. the transmitted light channel through lateral loading replace lights. In particular, the assignment The colors of the channels naturally vary.

Through the individual allocation of the six described above Image channels thus give you freedom, depending on the Application can use differently. The following are three Examples of this use are shown:

Checking a surface for color and gradient

• - First time slot: three-channel color image (R, G, B). Illumination: white light (from LEDs that are switch at 10 kHz).
• - second time slot: structured light for altitude measurement solution. Lighting: laser diode with grating. The Be lighting is monochrome, e.g. Loaf. So the picture shows only one channel in the second time slot

Testing of wooden surfaces

• - First time slot: three-channel color image (R, G, B). Lighting: white light (that's the first time slot fully occupied.
• - Second time slot:
• - Red channel (color channel 1 ): structured light for height measurement (e.g. red laser diode with line grating)
• - Color channel 2 : transmitted light illumination (to show cracks and holes in the wood; lighting realized e.g. with green LEDs).
• - Color channel 3 : tracheid effect. Lighting realized e.g. B. with blue laser and line optics.

Testing transparent materials

• - First time slot: three-channel color image (R, G, B). Illumination: white light (incident light)
• - Second time slot: transmitted light (color or monochrome).

In the inventive method and the inventive ß device for multi-channel inspection of surfaces Only one color camera (Zei steering camera or matrix camera), but at least two light sources. The light sources are synchronized with Recording cycle of the camera switched alternately, which means simultaneous  at least two pictures are taken that fit are closely related. Depending on the design of the Light sources can use different types of images Contain information about the surface; in particular Color information when the surface is illuminated with white homogeneous light, information about the height of the Surface when illuminated with structured light (light cutting process) or information about the transparency of the Surface when illuminated by transmitted light.

Claims (25)

1. A method for the automatic inspection of moving surfaces ( 118 ) using an image capturing device ( 106 ) which generates images with a predetermined or a given image generation frequency determined by the feed of the test specimen, and at least two radiation sources ( 102 , 104 ), the method has the following steps:
Irradiating the surface ( 118 ) with radiation from a first radiation source ( 102 ) which is arranged in a first geometric orientation with respect to the surface ( 118 ), the radiation having a first characteristic;
Capturing a first image from the surface ( 118 );
Irradiating the surface ( 118 ) with radiation from a second radiation source ( 104 ) which is arranged with respect to the surface ( 118 ) in a second geometrical orientation, the radiation having a second characteristic;
Capturing a second image from the surface ( 118 ); and
Determining properties of the surface ( 118 ) based on information from the first image and from the second image;
wherein the first radiation source ( 102 ) and the second radiation source ( 104 ) are controlled such that they are synchronized with the imaging frequency of the image detection device (106), so that the first radiation source ( 102 ) and the second radiation source ( 104 ) alternately Irradiate surface ( 118 ). 2. The method according to claim 1, wherein the image capturing device ( 106 ) is a line camera, the image lines with a be determined by the feed of the test specimen be or with a given line frequency, the first radiation source ( 102 ) and the second radiation source ( 104 ) are alternately pulsed synchronously with the line frequency of the line camera. 3. The method of claim 1, wherein the image capturing device ( 106 ) is a matrix camera that generates images with a determined by the feed of the test specimen or with a given frequency, wherein the first radiation source ( 102 ) and the second radiation source ( 104 ) are alternately pulsed synchronously with the image change of the matrix camera. 4. The method according to any one of claims 1 to 3, wherein the image capture device ( 106 ) is arranged substantially vertically spaced from the surface ( 118 ) and images from an examination line ( 116 ) on the surface ( 118 ), wherein radiation from the first radiation source ( 102 ) essentially perpendicular to the examination line ( 116 ) on the surface ( 118 ), radiation from the second radiation source ( 104 ) at an angle to the examination line ( 116 ) on the surface ( 118 ) strikes or the back of the surface ( 118 ) is irradiated in an area which lies opposite the examination line ( 116 ). 5. The method according to claim 4, with the following step:
Irradiating the surface ( 118 ) with a radiation from a third radiation source ( 104 ';130; 132 ) which is arranged in a third geometric orientation with respect to the surface ( 118 ), the second radiation source ( 104 ) and the third radiation source ( 104 ';130; 132 ) can be activated simultaneously to illuminate the surface at the same time,
wherein radiation from the third radiation source ( 130 ; 132 ) onto the examination line ( 116 ) on the surface ( 118 ) occurs at an angle which is not equal to the angle at which radiation from a second radiation source ( 104 ) on the Un tesuchungslinie ( 116 ) impinges, or wherein a radiation from the third radiation source ( 104 ') impinges on the examination line on the surface at an angle which is substantially equal to the angle at which radiation from the second radiation source ( 104 ) of the examination line ( 116 ), wherein the second radiation source ( 104 ) and the third radiation source ( 104 ') irradiate at least partially different sections of the examination line ( 116 ). 6. The method according to claim 5, in which the second radiation source ( 104 ) and the third radiation source ( 104 ') produce radiation with the same characteristic. 7. The method according to claim 5, wherein the second radiation source ( 104 ) and the third radiation source generate radiation with different characteristics. 8. The method according to any one of claims 1 to 7, wherein the first radiation source ( 102 ) is a light source that generates homogeneous white light, and wherein the second radiation source ( 104 ) is a light source that generates structured light. 9. The method of claim 8, wherein the third beam source is a light source that is structured Generates light. 10. The method of claim 8 or 9, wherein the first image contains information about the color gradient of the surface ( 118 ), and wherein the second image contains information about the height gradient. 11. The method according to any one of claims 4 to 10, in which the surface is a wooden surface, with three Images are generated, with the first image from the Surface is a three-channel color image (R, G, B) and the first radiation source provides white light, wherein the second picture is a single channel picture and the second radiation source with structured light a first color for a height measurement provides where where the third picture is another single-channel picture and the third radiation source with a second color be a linear illumination of the surface to the Er version of the tracheid effect provides.   12. Device for the automatic examination of moving surfaces, with:
a first radiation source ( 102 ) which radiates radiation with a first characteristic onto the surface ( 118 ) and which is arranged in a first geometric arrangement with respect to the surface ( 118 );
a second radiation source ( 104 ) which emits radiation with a second characteristic onto the surface ( 118 ) and which is arranged in a second geometric orientation with respect to the surface;
an image capture device ( 106 ) which generates images of the surface ( 118 ) at a given image capture frequency;
a control unit ( 108 ) which is operatively connected to the first radiation source ( 102 ), the second radiation source ( 104 ) and the image capture device ( 106 ), and which connects the first radiation source ( 102 ) and the second radiation source ( 104 ) to the Image generation frequency of the image generation device ( 106 ) synchronized in such a way that the first radiation source ( 102 ) and the second radiation source ( 104 ) alternately irradiate the surface ( 118 ) in order to alternate an image of the surface ( 118 ) based on the irradiation by the first radiation source ( 102 ) and to generate an image of the surface ( 118 ) based on the radiation from the second radiation source ( 104 ); and
an evaluation device which determines properties of the surface ( 118 ) based on information of the alternately generated images. 13. The apparatus of claim 12, wherein the image capturing device ( 106 ) is a line camera that generates image lines with a line frequency determined or given by the feed of the test specimen, where in the control unit ( 108 ) the first radiation source ( 102 ) and second radiation source ( 104 ) pulsates synchronously with the line frequency of the line camera. 14. The apparatus of claim 12, wherein the image capturing device ( 106 ) is a matrix camera, the image with the be determined by the feed of the specimen be generated or given frequency, wherein the control unit ( 108 ) the first radiation source ( 102 ) and second radiation source ( 104 ) alternately pulses synchronously with the image change of the matrix camera. 15. The device according to one of claims 12 to 14, wherein the image capture device ( 106 ) is arranged substantially perpendicularly spaced from the surface ( 118 ) and generates images of an examination line ( 116 ) on the surface ( 118 ), the first Radiation source ( 102 ) directs radiation essentially perpendicularly to the examination line ( 116 ) on the surface ( 118 ), the second radiation source ( 104 ) directing radiation at an angle onto the examination line ( 116 ) on the surface ( 118 ) or onto one Area of the rear side of the surface that never opposite the examination line ( 116 ). 16. The apparatus of claim 15, having the following feature:
a third radiation source ( 104 ';130; 132 ) which radiates radiation onto the surface ( 118 ) and which is arranged in a third symmetrical orientation with respect to the surface ( 118 );
wherein the control unit ( 108 ) controls the second radiation source ( 104 ) and the third radiation source ( 104 ', 130 , 132 ) simultaneously in order to irradiate the surface ( 118 ) simultaneously,
wherein the third radiation source ( 130 , 132 ) radiates radiation onto the examination line ( 116 ) of the surface ( 118 ) at an angle that is not equal to the angle at which the second radiation source ( 104 ) emits radiation onto the examination line ( 118 ), or wherein the third radiation source ( 104 ') directs radiation onto the inspection line ( 116 ) of the surface ( 118 ) at an angle which is substantially equal to the angle at which the second radiation source ( 104 ) radiation is directed towards the examination line ( 116 ), the second radiation source and the third radiation source irradiating at least partially different sections of the examination line ( 116 ). 17. The apparatus of claim 16, wherein the second radiation source ( 104 ) and the third radiation source ( 130 , 132 ) radiation with the same characteristic he testify. 18. The apparatus of claim 16, wherein the second radiation source ( 104 ) and the third radiation source generate radiation of different characteristics. 19. Device according to one of claims 12 to 18, wherein the first radiation source ( 102 ) is a light source that generates homogeneous white light, and wherein the second radiation source ( 104 ) is a light source that generates structured light. 20. The apparatus of claim 19, wherein the third Radiation source is a light source that struktu generated light. 21. The apparatus of claim 19 or 20, in which the first image contains information about the color gradient of the upper surface ( 118 ), and in which the second image contains information about the height profile. 22. The device according to one of claims 12 to 21, at of the radiation sources through LED components or Laser diode components are formed. 23. The device according to any one of claims 16 to 22, the surface of which is a wooden surface, with three Images are generated, with the first image from the Surface is a three-channel color image (R, G, B) and the first radiation source provides white light, wherein the second picture is a single channel picture and the second radiation source with structured light  a first color for a height measurement provides where where the third picture is another single-channel picture and the third radiation source with a second color be a linear illumination of the surface to the Er version of the tracheid effect provides. 24. A method for multisensorial inspection of moving surfaces with a multichannel sensor device that generates images from the surface, each of the generated images providing information about the surface in at least one channel of the multichannel sensor device, the multichannel sensor device at least two images below generated different irradiation conditions, wherein the multi-channel sensor device alternately generates the images synchronously with an image generation cycle. 25. The method of claim 24, wherein the multi-channel Sensor device a single color camera and the surface is divided by at least two Lighting devices for generating multi-channel Illuminated images from the surface, the Light sources operated in time multiplex and synchronously switched alternately with the recording clock of the camera be, the light sources additionally by their Color (R, G, B) can be distinguished and the Number of distinguishable sensor channels thus the pro derives from the number of time slots and the number of There are color separations, with each sensor channel having a com combination of the camera and a light source speaks and by design and geometric Arrangement of the light sources in the different sen information channels of various types about the  Surface can be captured with the information from the different sensor channels which is related.