LED matrix lighting device

Abstract

The present invention relates to an LED matrix illumination device (20) for illuminating an illumination pattern with uniform intensity. The LED matrix illumination device includes a plurality of LEDs (22), a collimating lens (23) in front of each LED (22) for collimating the light of that LED (22), and a light-refractive element (24) in front of the collimating lens (23) configured to refract the light of at least a first portion of the plurality of LEDs (22) at a different refraction angle than the light of at least a second portion of the plurality of LEDs (22). The present invention further relates to a machine vision system, method, and computer program product.

Description

[Technical Field]

[0001] (Technical field) The present invention relates to an LED matrix illumination device configured to create a uniform and homogeneous illumination pattern on a surface of a surveillance target, such as a continuous wood fiber web. The present invention further relates to a machine vision system including at least one LED matrix illumination device, a method of utilizing the LED matrix illumination device, and a computer program product for causing the system to perform the method. [Background technology]

[0002] (background) In continuous manufacturing processes, such as paper, pulp, and corrugated board machines, materials or products are constantly being formed and moving through the machine. In such processes, multiple cameras, e.g., 10 to 40 cameras, are used to monitor the process to detect possible misalignments or web breaks in different parts of the machine. For imaging, the continuous material web must be illuminated. Because paper webs can move at speeds exceeding 120 km / h, the cameras must use very short shutter speeds to freeze the motion. Therefore, the quality of images from a moving web is highly dependent on lighting.

[0003] Nowadays, LED illumination devices are also often used to illuminate a moving web. The idea is to provide a uniform illumination pattern across the surface of the web. However, this is not always possible due to the lack of space above (or below) the moving web, which prevents the LED illumination devices from being mounted perpendicular to the paper web to be illuminated and monitored; the web is instead illuminated from the side of the paper-making machine, often at an angle of 30 to 60 degrees relative to the paper web. Therefore, the illumination pattern may not be uniform, with different parts of the pattern having different brightness levels. Summary of the Invention

[0004] (overview) Improved methods and technical equipment for implementing the methods have now been invented. Various aspects of the invention include an LED matrix illumination device configured to create a uniform and homogeneous illumination pattern on a surface of a surveillance target, such as a continuous wood fiber web. The invention further relates to a machine vision system including at least one LED matrix illumination device, methods for utilizing and controlling LED matrix illumination devices, and computer program products for causing the system to perform the methods and control the LED matrix illumination device.

[0005] According to a first aspect of the present invention, there is provided an LED matrix illumination device for illuminating an illumination pattern with uniform intensity, the LED matrix illumination device comprising a plurality of LEDs, a collimating lens in front of each LED for collimating light of that LED, and a light-refractive element in front of the collimating lens configured to refract light of at least a first portion of the plurality of LEDs at a different refraction angle than at least a second portion of the plurality of LEDs.

[0006] In one embodiment, the LED matrix illumination device further comprises at least one power supply circuit for the plurality of LEDs, and an amount of current supplied to a first portion of the plurality of LEDs is different from an amount of current supplied to at least a second portion of the plurality of LEDs. In one embodiment, the first portion of the plurality of LEDs comprises a single LED, a row of the plurality of LEDs of the LED matrix, or a column of the plurality of LEDs of the LED matrix. In one embodiment, the refraction angle is determined based on the position of the LED in the LED matrix illumination device. In one embodiment, the refraction angle is the angle between the central optical axis of the collimated light of the LED and the central optical axis of the refracted light of the same LED. In one embodiment, the FWHM viewing angle of the collimated light of the LEDs is at least as large as the difference between the refraction angles. In one embodiment, the current supplied to at least one LED is adjustable. In one embodiment, the current supplied to at least one LED is adjustable based on a detected intensity deviation in the captured image.

[0007] According to a second aspect of the present invention there is provided a machine vision system for detecting deviations from a wood fibre web, the machine vision system comprising an LED matrix illumination device according to the first aspect and embodiments thereof, at least one imaging device for capturing images of the illuminated area, and a data processing device.

[0008] According to one embodiment, the data processing device is configured to analyze the image data to detect intensity deviations in the captured images.

[0009] According to one embodiment, the data processing device is configured to adjust the current supplied to the at least one LED based on the detected intensity deviation.

[0010] According to a third aspect of the present invention, there is provided a method comprising acquiring image data, analysing the image data, detecting in the captured image intensity deviations in an illumination pattern provided by an LED matrix illumination device according to the first aspect and embodiments thereof, and adjusting a current supplied for at least one LED of the LED matrix illumination device.

[0011] The present invention 4 According to an aspect of the present invention, there is provided a computer program product embodied on a non-transitory computer-readable medium, comprising computer program code configured to, when executed on at least one processor, cause a system to perform a method comprising acquiring image data in a captured image, analyzing the image data, detecting intensity deviations in an illumination pattern provided by an LED matrix illumination device according to the first aspect and embodiments thereof, and adjusting a current supplied to at least one LED of the LED matrix illumination device. [Brief explanation of the drawings]

[0012] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings.

[0013] [Figure 1a-b] 1 shows the optical axes of the LEDs of a prior art LED matrix illumination device from above and from the side. [Figure 1c-d] 1a and 1b show the viewing angles of the LEDs of the LED matrix illumination device; [Figure 2a-b] 1 illustrates the optical axes of LEDs in an LED matrix illumination device according to an exemplary embodiment. [Figure 2c-d] 2a and 2b show the viewing angles of the LEDs of the LED matrix illumination device. [Figure 3a] 1 illustrates an LED matrix illumination device according to an exemplary embodiment. [Figure 3b] 3b shows an exploded view of the LED matrix lighting device of FIG. 3a. [Figure 4] 1 illustrates a machine vision system including an LED matrix illumination device, according to an exemplary embodiment. [Figure 5] 1 illustrates a machine vision system including an LED matrix illumination device, according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] (Detailed explanation) In continuous manufacturing processes, such as paper, cellulose, and cardboard manufacturing machines, materials or products are constantly being formed and moving through the machine. A machine vision system including multiple cameras, e.g., 10-40 cameras, can be used to monitor the process at different parts of the process. Monitoring can include imaging the monitored target, e.g., the moving web, storing the image data, and analyzing the image data. The camera, i.e., the image sensor, can be, for example, a CMOS or CCD camera, a matrix or line scan camera, a black and white or color camera, a regular or smart camera, or any suitable camera.

[0015] To image a surveillance target, the surveillance target must be illuminated. For example, to image a web product, the web product must be illuminated by an illumination pattern or line having a width corresponding to the width of the web product. The term "web product," i.e., "web," in this context refers to any type of wood fiber web produced by a paper, cellulose, or cardboard manufacturing machine, and the term "wood fiber," in this context, refers to any suitable wood fiber, such as paper, cellulose, or cardboard fiber. The wavelength of the light used can vary over a wide spectrum depending on the surveillance target and / or surveillance system, and the wavelength can vary from the ultraviolet (UV) region to the short-wave infrared thermal region (SWIR).

[0016] As previously mentioned, suitable illumination depends on the surveillance target. However, a uniform illumination pattern with uniform intensity across the entire pattern illuminated on the surveillance target provides a good starting point for high-quality imaging, as it improves the probability of detecting a given object of interest, such as a misalignment or web break in a web product. The type of illumination device, the number of illumination devices, the light direction, the operation of the illumination device, or the illumination devices used may depend on the object positioned to be imaged and the type of camera used. Illumination devices used to illuminate a surveillance target, e.g., a web, typically include at least two, several, or multiple light sources, such as LEDs. LEDs require at least one LED circuit, LED driver, or current source circuit, which is an electronic circuit configured to power the LEDs, i.e., a power supply circuit. Typically, one electronic circuit powers several or multiple LEDs. The power supply circuit is configured to supply current to the LEDs so that they reach the required or desired light intensity and to limit the current to prevent damage to the LEDs. While LEDs are discussed throughout this application, other suitable light sources may be used instead of LEDs.

[0017] Image data of the captured images may be stored and analyzed by a data processing device in each camera, e.g., a smart camera, used to capture the manufacturing process, and / or the image data of the captured images may be transmitted to an external data processing device for storage and analysis. An external data processing device is a data processing device that is not an integral part of the camera. The data processing device monitors the data to locate predetermined objects of interest. Image data may also be stored and analyzed in the above-described systems, i.e., systems that include both cameras with integrated data processing devices and cameras with external data processing devices. All systems, cameras with integrated data processing devices, cameras with external data processing devices, and combinations thereof, include or are connected to databases, user interfaces, and possible interfaces to factory systems and manufacturing processes.

[0018] Cameras capturing images of a continuous manufacturing process can be part of a web monitoring system (WMS) that monitors web breaks. The web monitoring system can continuously store image data received from multiple cameras in a computer program product memory. This stored image data can be used to determine the cause of a paper web break after a web break has occurred. Because paper webs can travel at speeds exceeding 120 km / h, cameras must use very short shutter speeds to freeze the motion. Therefore, the quality of images captured from a fast-moving web depends heavily on the uniform intensity of the illumination and how it is distributed across the image area.

[0019] The camera may also be part of a web inspection system (WIS), which is an event capture camera system that monitors for possible web misalignment. The term "web misalignment" in this context includes any detectable misalignment of a web product, such as defects, holes, stains, obvious variations, gray or dark spots, streaks, wrinkles, bubbles, or patterns within the web product. In a web inspection system, a camera is mounted to capture the entire cross-web width of the paper web and store the captured image data. The illumination used may be, for example, reflected light, or the web may be illuminated through the web. The angle of the reflected light may also vary widely, depending on the paper web defect being sought. Again, the quality of the image depends on the quality of the illumination.

[0020] From the above, it is clear that illumination is an important part of quality process monitoring. Therefore, the idea of ​​the present invention is to provide an illumination device that provides conditions that are as efficient as possible to detect a given object from a captured image.

[0021] An illumination device according to an exemplary embodiment of the present invention is a matrix-type light-emitting LED illumination device, i.e., an LED matrix illumination device configured to create a uniform illumination pattern on a surface of a monitoring target, such as a web product, having uniform luminous intensity, i.e., brightness, throughout the pattern. The LED matrix illumination device may include a base, LEDs, at least one power supply circuit for the LEDs, a collimating lens, and an optical refractive element. The LEDs are arranged in a matrix on the surface of the base, for example, by mounting a circuit board or other surface or substrate on which the LEDs are mounted on the surface of the base.

[0022] The power supply circuit is configured to supply current to the plurality of LEDs so that the plurality of LEDs illuminate at a necessary or desired intensity. A portion of the plurality of LEDs may be controlled differently from at least one other portion of the plurality of LEDs, i.e., the power supply circuit may supply a different amount of current to the portion of the plurality of LEDs than to at least one other portion of the plurality of LEDs. It is also possible for each LED to be controlled differently from the other LEDs, for a column of LEDs in an LED matrix to be controlled differently from at least one other column of LEDs in the LED matrix, or for a row of LEDs in an LED matrix to be controlled differently from at least one other row of LEDs in the LED matrix. The amount of current supplied may depend, for example, on the position of the LED within the matrix, i.e., where the light beam of the LED is directed, i.e., whether it is positioned to be refracted by the light refractive element, or which portion of the surface the light of the LED is positioned to illuminate, taking into account the portion of the surface illuminated by the light positions of the other LEDs. For example, if a first portion of the plurality of LEDs (e.g., a row of LEDs) is located at a greater distance from the illumination surface than at least one other portion of the plurality of LEDs (other rows), the LEDs in the first portion are deflected such that a larger angle of refraction is formed between the optical central axis of the LEDs' light beams (before the light beams are deflected by the refractive element) and the optical central axis of the deflected LED light beams, and the amount of current supplied to the first portion of LEDs can be higher than the current supplied to the at least one other portion of LEDs, with the higher current making these LEDs brighter, so that despite their greater distance to the surface, the first portion of LEDs can illuminate the surface similarly to the at least one other portion of LEDs that are closer to the surface and controlled by a lower current. The amount of current supplied may be controlled by a data processing device integrated into the LED matrix illumination device or an external data processing device, for example, a data processing device that also analyzes image data of the captured image, or a user may control the amount of current supplied by setting the amount of current to the LEDs.

[0023] A collimator is an optical element that collects and refracts light rays from an LED into parallel beams. A collimator can be constructed using a parabolic mirror or lens, with the LED positioned at its focal point. A collimating lens can be placed in front of each LED; that is, a collimating lens mounted on an LED matrix to collimate the output light from the LEDs in the LED matrix is ​​present. However, the collimating lens can be an integral part of the LED, in which case a separate collimating lens on the LED is not required. Together, one LED and one collimating lens define the viewing angle of the LED, i.e., the light beam angle of the LED, which indicates the usable light emitted from a single LED source. The viewing angle can be defined using the full-width-at-half-maximum (FWHM) method and can be expressed in degrees. FWHM defines the angle at which 50% of the peak intensity is reached. For example, if an LED is measured to have 50% intensity at a 40° angle, the viewing angle (FWHM) of the LED is 40°.

[0024] The optical refractive element is disposed in front of each collimating lens, either in the form of a matrix of refractive lenses attached to the LED matrix so that each LED has a collimating lens and a refractive lens, or as a single refractive lens attached to all the LEDs in the LED matrix. The lenses of the refractive lens matrix may be, for example, prisms, such as Fresnel prisms, and the single refractive lens may be, for example, a membrane or film forming a Fresnel-type lens or prism. The optical refractive element is configured to direct, i.e., refract, the central optical axis of each collimated LED light beam gradually outward from the central optical axis of the collimated LED light. The refractive element is configured to direct the LED light beams over a wider area so that the light is not directed to the same area on the surface of the surveillance target or so that the illuminated areas on the surface barely overlap. The non-overlapping, i.e., refracted, light beams enable the formation of a uniform illumination pattern with uniform luminous intensity, i.e., brightness, across the pattern on the surface of the surveillance target, since the current supplied to the LEDs is controlled and the current control affects the intensity of the illuminated areas. When light beams overlap, controlling the current of the LEDs has no effect on the lighting pattern, or at least is not as efficient as when each LED illuminates its own area in the lighting pattern, since the same area is illuminated by several LEDs.

[0025] 1a shows the optical axes 14 of the LEDs 12 of a prior art LED matrix illumination device 10 from above, i.e. showing the horizontal optical axis of the LED matrix illumination device 10. The LED matrix illumination device 10 comprises a base 11, an LED matrix and a collimator matrix. The LED matrix is × The LED matrix illumination device 10 has a size of 4, i.e., there are 36 LEDs 12 in the LED matrix of the LED matrix illumination device 10. The base 11 is where the electronic circuitry of the LEDs 12 of the matrix illumination device is arranged. The collimator matrix is ​​arranged above the LEDs 12 and has 9 ×1a and 1b, each optical axis 14 extends from the LED 12 in a straight line, i.e., it is not refracted.

[0026] FIG. 1c shows the viewing angle of the LEDs 12 of the LED matrix illumination device 10 of FIG. 1a from above, and FIG. 1d shows the viewing angle of the LEDs 12 of the LED matrix illumination device 10 of FIG. 1b from the side. The viewing angle 15 of the LEDs 12 has a conical shape; initially narrow, it widens as the light moves away from the LED 12. The full width at half maximum (FWHM) viewing angle of the LEDs 12 is 40 degrees. To achieve a uniform illumination pattern across the web from the side, the FWHM (full width at half maximum) viewing angle of each LED in the illumination device must be wide, for example, 20-60 degrees.

[0027] The viewing angles 15 of the central LEDs 12 are shown in the line pattern. Because the optical axes 14 of the LEDs are straight and parallel, the viewing angles of the LEDs 12 overlap when a certain distance is reached from the LEDs, and therefore the illumination pattern formed on the surface 16 has a non-uniform luminous intensity, with the central region of the illumination pattern being illuminated by several LEDs 12, which in this embodiment are all the LEDs, and the outermost portion of the pattern being illuminated by only the light generated by one LED. Thus, the central region of the illuminated line or pattern is brighter than the edge regions, e.g., the center of the illumination pattern. Department Different parts of the paper web are illuminated with different intensities depending on the distance of the part from the center of the illumination pattern. Department There is bright light nearby, but less light at the edge areas of the illumination pattern. Furthermore, even if the LED current of this prior art illumination device 10 is adjusted, which is not the case in this case, controlling the power of the LEDs does not have much effect on the formed pattern because the same area is illuminated by several LEDs.

[0028] 2a shows from above, the central optical axes 25 of the light beams of the LEDs 22 of the LED matrix illumination device 20 according to an exemplary embodiment of the present invention, i.e., the central horizontal optical axes 25 of the collimated and refracted LED light beams, after the light of the LEDs 22 passes through the collimating lens 23 and the optical refractive element 24. FIG. 2b shows from the side, the central optical axes 25 of the light beams of the LEDs 22, i.e., the central vertical optical axes of the collimated and refracted LED light beams. 25 The LED matrix illumination device 20 includes a base 21, an LED 22, a collimating lens 23, and a light refractive element 24. The size of the LED matrix is ​​9 mm in this embodiment. * 4(column * In some embodiments, the number of columns may be, for example, 1 to 25, and the number of rows may be, for example, 1 to 25, or any other suitable number. In the smallest matrix, the number may be 2, i.e., the matrix is ​​2 * 1. The LEDs 22 may be mounted, for example, on circuit board(s) or some other board(s) that are mounted on the base 21.

[0029] There may be at least one power supply circuit for the LEDs 22 internal to the base 21 and other possible electronic circuits, or the at least one power supply circuit for the LEDs 22 may be an external power supply circuit for the LEDs 22 electrically connected to the LEDs 22. The at least one power supply circuit is configured to power the LEDs 22 so that each LED 22 illuminates with the required or desired intensity defined therefor. The amount of current supplied by the at least one power supply circuit may be controlled and / or determined by a data processing device integrated in the LED matrix illumination device 20 or by an external data processing device (not shown).

[0030] A collimating lens 23 is placed in front of each LED 22, i.e., there is a matrix of collimators, collimating lenses 23, mounted on the LED matrix to collimate the output light of the LEDs. The LEDs and collimating lenses together define the FWHM viewing angle of the LED, i.e., the beam of light provided by each LED 22, which may be expressed in degrees as explained above. Note that the central axis of the collimated LED light beam corresponds to the central axis of the LED light that has not yet passed through the collimating lens.

[0031] An optical refractive element 24 is disposed in front of each collimating lens 23 (and LEDs 22). In this embodiment, the optical refractive element 24 is a single refractive film mounted in front of all the LEDs 22 of the LED matrix and the collimating lenses 23 of the matrix of collimating lenses 23. The optical refractive element 24 may also be a matrix of refractive lenses / films mounted on the matrix of collimating lenses 23. The optical refractive element 24 is positioned to direct the central optical axis of the collimated LED light beam gradually outward from the central axis of the collimated LED light (and the center of the LED matrix illumination device 20) so that a refraction angle 25 is formed between the central optical axis of the collimated LED light beam and the central axis 25 of the refracted LED light beam. The refraction angle is determined based on the position of the LEDs 22 in the LED matrix illumination device 20. For example, if an LED 22 is configured to illuminate a more distant area, its refraction angle will be larger than the refraction angle of an LED configured to illuminate a closer area, thereby illuminating the more distant area. This refraction can be seen in Figures 2a and 2b by comparing the optical axis 25 of the refracted LED light beam of LED 22 in Figures 2a and 2b with the optical axis 14 of the unrefracted LED light beam of LED 12 shown in Figures 1a and 1b. The optical refraction element 24 is configured to be easily variable. This is because the magnitude of the required refraction angle produced by the optical refraction element 24 depends on the distance of the LED from the surface to be illuminated, i.e., the distance from the surface of the monitoring target, which can change if the position of the LED matrix illumination device changes relative to the target surface 27. Different types of optical refraction elements can achieve different refraction angles. The refraction angle can be, for example, 5 to 10 degrees.

[0032] Figure 2c shows the viewing angle 26 of the LEDs 22 of the LED matrix illumination device 20 of Figure 2a, and Figure 2d shows the viewing angle 26 of the LEDs 22 of the LED matrix illumination device 20 of Figure 2b. The viewing angle 26 of the LEDs 22 has a conical shape; initially narrow near the LED and widening as the light moves away from the LED 22. A central axis 25 of one of the refracted LED light beams is shown in both Figures 2c and 2d.

[0033] The viewing angles 26 of each LED 22 in Figures 2c and 2d are indicated by different checkered patterns. Because the central optical axes 25 of the light beams of the LEDs 22 are straight and are refracted outward by the optical refractive element 24, the viewing angles 26 of the LEDs 22 do not overlap when reaching the target surface 27. Therefore, each portion of the illumination pattern is illuminated by only one LED 22, and each LED, column, or row of LEDs can be individually powered to provide the desired intensity, so that the formed illumination pattern on the surface 27 can have a uniform luminous intensity. Furthermore, because the viewing angles 26 of the LEDs 22 do not overlap when reaching the target surface 27 and therefore each portion of the illumination pattern is illuminated by only one LED 22, controlling the power of one LED, column, or row of LEDs will have a distinct effect on the intensity of the formed pattern on the target surface 27.

[0034] In this exemplary embodiment, the FWHM viewing angle of each LED 22 is 10 degrees in both the vertical and horizontal directions. Generally, in an LED matrix illumination device according to an embodiment of the present invention, the FWHM viewing angle of the LED's light beam is defined to be at least as large as the difference in the refraction angle of the optical axes of two adjacent LEDs. The difference in the refraction angle of the optical axes of adjacent LEDs occurs because, depending on the position of the LED in the LED matrix and thus the distance from the monitored target, the optical refraction element directs the central optical axis of the collimated LED light beam laterally, e.g., gradually outward from the central optical axis of the collimated LED light, and away from the center of the illumination device, so that each LED illuminates a different part of the illumination pattern, i.e., the viewing angles do not overlap. However, if the FWHM viewing angle of the LED's light beam is larger, e.g., 20 degrees or more, the adjustment accuracy of the illumination pattern may decrease, i.e., the intensity adjustment achieved by controlling the power of the LEDs may not be as precise.

[0035] FIG. 3a illustrates an LED matrix illumination device 30 according to an exemplary embodiment. The LED matrix illumination device 30 comprises a body 31, a matrix of LEDs 32, a matrix of collimating lenses 33, and a matrix of light-refracting elements 34. The LEDs 32 are disposed on the body 31, for example, by themselves or by using a separate surface arranged to be attached to the body 31. The body 31 further includes electronic circuitry 35 configured to power the LEDs, and may also include a data processing device including at least one processor, at least one memory containing computer program code for one or more program units, and means for receiving configuration information on how to power the LEDs from a data processing device of a machine vision system or other external data processing device, wirelessly or via a wired connection, for example, from a receiver or transceiver. A collimating lens 33 of the collimating lens matrix is ​​disposed in front of each LED 32 of the LED matrix. The photorefractive elements 34 of the photorefractive element matrix are positioned on the opposite side of the collimating lenses 33 from the LEDs 32 and in front of each collimating lens 33 to refract the collimated light of the LEDs 32 laterally away from the central optical axis of the collimated LED light 37 of the LEDs 32. The central optical axis of the refracted light is indicated by reference numeral 38 in FIG. 3b. The LED matrix light element 30 is connected to a power source. One or more of the photorefractive elements 34 may have different refractive properties than the other photorefractive elements 34, i.e., one or more of the photorefractive elements 34 may have different refractive properties compared to the other photorefractive elements 34, because the need to refract the central optical axis of the collimated light 37 depends on the distance of the LEDs 32 (and the photorefractive elements 34) from the target / area of ​​the surface to be illuminated. If there is only one photorefractive element 34 instead of a matrix of photorefractive elements 34, the refractive properties within the element may vary.

[0036] By means of the collimating lens 33 and the refractive element 34, the LED matrix illumination device 30 illuminates the imaging target such that the light uniformly illuminates the imaging target. However, because the intensity of the illuminated pattern must also be uniform for imaging, the amount of current supplied by the electronic circuitry 35 to a first portion of the LEDs differs from the amount of current supplied to at least a second portion of the LEDs. The amount of current supplied depends, for example, on the arrangement of the LEDs within the LED matrix of the illumination device, and thus the angle between the central optical axis of the LEDs (before refraction) and the central optical axis of the refracted LED light beam, but also on the illumination angle, i.e., how far away from the imaging target the illumination device is positioned.

[0037] Figure 3b shows an exploded view of the LED matrix illumination device 30 of Figure 3a. 3b Shown in the figure are a light ray 36 from the LED, the optical axis of the collimated LED light 37, and the central optical axis of the refracted LED light 38. Also shown is the refraction angle 39 between the central optical axis of the collimated LED light 37 and the central optical axis of the refracted LED light 38.

[0038] 4 illustrates a disclosed WMS or WIS machine vision system 40 in conjunction with a moving paper web 43 as a target object, according to one embodiment. The direction of movement of the web 43 is toward the image, away from a viewer of the image. The machine vision system 40 includes a camera 41, an LED matrix illumination device 44 according to an embodiment of the present invention, and a data processing device 42. The camera 41 is configured to capture images from the illuminated paper web 43 and transmit data for each image to the data processing device 42. The LED matrix illumination device 44 is a separate illumination device, although the illumination device 44 may be an integral part of the camera 41.

[0039] Data processing device 42 is configured to analyze the received image data captured and transmitted by camera 41 to detect misalignments in web 43. Data processing device 42 may further analyze illumination pattern 46 in the image. If data processing device 42 detects from the image data that pattern 46 does not have uniform luminous intensity throughout the pattern, it may reconfigure the electronic circuitry of LED matrix illumination device 44 so that the amount of current supplied to one or more LEDs is changed so that the intensity of the illumination pattern is constant throughout the pattern, thereby allowing misalignments in web 43 to be more accurately detected across the width of the web.

[0040] The data processing device 42 may, for example, control the power of the LEDs such that the amount of current supplied to a first portion of the LEDs is different from the amount of current supplied to at least a second portion of the LEDs. The amount of current supplied may again, for example, depend on the arrangement of the LEDs in the LED matrix of the illumination device 44, i.e., the refraction angle, and thus also on the distance of the LEDs from the portion of the paper web 43 that they are configured to illuminate. Thus, an LED matrix illumination device 44 according to one embodiment of the present invention, comprising LEDs whose power supply is adjusted individually or in groups, is arranged to illuminate the paper web 43 (or other material web) for imaging with an illumination pattern 46 having a uniform intensity, for example an illumination line having a uniform intensity.

[0041] The illumination angle is the angle between the horizontal central axis of the LED matrix illumination device 44 and the surface of the web 43. In this embodiment, the angle is forty-five degrees (45°), but the angle may also be larger or smaller and may depend on the space configured for the illumination device 44 or, for example, the width of the lighting pattern configured to be illuminated.

[0042] The data processing device 42 includes at least one processor, at least one memory containing computer program code for one or more program units, and means for receiving image data from the camera 41 wirelessly or via a wired connection, e.g., a receiver or transceiver, and means for transmitting trigger signals wirelessly or via a wired connection, e.g., a transmitter or transceiver. There may be multiple processors, such as general-purpose processors and graphics processors, as well as DSP processors, and / or multiple different memories, e.g., volatile memory for storing data and programs during execution and non-volatile memory such as a hard disk for permanently storing data and programs. The data processing device 42 is an external data processing device and may be any computing device, such as a computer, suitable for handling image data and, in some cases, determining or controlling the current supplied to the LEDs. The data processing device 42 is in electronic communication with the camera 41 and the illumination device 44 via signal lines or wirelessly. The camera 41 may also include a video controller and an audio controller for generating signals that can be generated for the user by a computer accessory. The camera 41 may generate output for the user via output means. The video controller may be connected to a display. The display may be, for example, a flat panel display or a projector for producing a larger image. The audio controller may be connected to an audio source such as a loudspeaker or earphones. The camera 44 may also include an acoustic sensor such as a microphone.

[0043] 5 illustrates an embodiment of the present invention in which a WMS or WIS machine vision system 50 according to one embodiment is positioned to monitor a moving web 57. The machine vision system 50 includes two LED matrix illumination devices 58, 59 according to an embodiment of the present invention and two smart cameras 51, 54 including image sensors 52, 55 and data processing devices 53, 56. The LED matrix illumination devices 58, 59 may also be an integral part of the smart cameras 51, 54. LED Matrix Illumination Device 58 Move do The web 57 is illuminated at a 40 degree angle, and the LED matrix illumination device 59 moves do The web 57 is illuminated at a 50 degree illumination angle. The LED matrix illumination devices 58, 59, not clearly visible in FIG. 5, are located to the side, i.e., they illuminate the pattern so as to be positioned away from the axis of symmetry of the illuminated pattern. The image sensors 52, 55 are moved do The smart cameras 51, 54 are configured to capture images from the web 57 and transmit the image data to the data processing devices 53, 56 of the smart cameras 51, 54.

[0044] The data processing devices 53, 56 may have a similar structure and functionality to the data processing device 42.

[0045] Image sensors 52, 55 are configured to capture images of web 57, and LED matrix illumination devices 58, 59 illuminate web 57 with illumination patterns 58a, 59a on the surface of web 57. Patterns 58a, 59a span the entire width of web 57. However, the patterns could be narrower and span the entire width of web 57.

[0046] Various embodiments of the present invention may be implemented with the aid of computer program code residing in a memory and causing an apparatus to perform the invention. For example, an apparatus that is a computing device, e.g., a data processing device, may include circuitry and electronics for analyzing, receiving, and transmitting data, computer program code in a memory, and a processor that, when executing the computer program code, causes the apparatus to perform features of the embodiments.

[0047] The present invention achieves significant advantages when compared with existing LED matrix illumination devices or at least machine vision system methods and systems that include LED matrix illumination devices. According to the arrangement of the present invention, because the LED matrix illumination device has optical refractive elements in front of the collimating lens (i.e., on the side of the collimating lens opposite the LEDs) and in front of the LEDs that refract the central optical axes of the LEDs' light beams in a direction such that the areas illuminated by the LEDs do not overlap or only slightly overlap, and because the power of the LEDs can be controlled individually or as a group so that each LED illuminates the target with the same or essentially the same intensity, it is possible to place the LED matrix illumination device to the side of the web or other target to be illuminated and still illuminate the entire pattern with a uniform intensity.

[0048] It is obvious that the invention is not limited solely to the above-described embodiments, but it can be modified within the scope of the appended claims. The present application provides the following aspects of the invention. (Aspect 1) 1. An LED matrix illumination device (20) for illuminating an illumination pattern with uniform intensity, comprising: a plurality of LEDs (22); a collimating lens (23) in front of each LED (22) for collimating the light of that LED (22); and a light refractive element (24) in front of the collimating lens (23) configured to refract at least a first portion of the light of the plurality of LEDs (22) at a different refraction angle (39) than the light of at least a second portion of the plurality of LEDs (22), wherein the current supplied to at least one LED (22) is adjustable based on an intensity deviation detected in a captured image. (Aspect 2) The LED matrix illumination device (20) of aspect 1, further comprising at least one power supply circuit (35) to the plurality of LEDs (22), wherein the amount of current supplied to the first portion of the plurality of LEDs (22) is different from the amount of current supplied to at least the second portion of the plurality of LEDs (22). (Aspect 3) 3. The LED matrix illumination device (20) of claim 1 or 2, wherein the first portion of the plurality of LEDs (22) includes one LED (22), one row of the plurality of LEDs (22) of the LED matrix, or one column of the plurality of LEDs (22) of the LED matrix. (Aspect 4) 4. The LED matrix illumination device (20) of any one of aspects 1 to 3, wherein the refraction angle (39) is determined based on the position of the LEDs (22) within the LED matrix illumination device (20). (Aspect 5) 5. The LED matrix illumination device (20) according to any one of aspects 1 to 4, wherein the refraction angle (39) is the angle between the central optical axis of the collimated light (37) of the LED (22) and the central optical axis of the refracted light (38) of the same LED (22). (Aspect 6) 6. The LED matrix illumination device (20) of any one of aspects 1 to 5, wherein the FWHM viewing angle (26) of the collimated light (37) of the LEDs (22) is at least as large as the difference between the refraction angles (39). (Aspect 7) 7. The LED matrix illumination device (20) according to any one of the preceding embodiments, wherein the current supplied to the at least one LED is adjustable. (Aspect 8) A machine vision system (40) for detecting misalignments from a wood fiber web, comprising: an LED matrix illumination device (20) according to any one of aspects 1 to 7, and at least one imaging device (41) for capturing an image of the illuminated area; and a data processing device (42). (Aspect 9) 9. The machine vision system (40) of claim 8, wherein the data processing device (42) is configured to analyze image data to detect intensity deviations in the captured images. (Aspect 10) acquiring image data; analyzing the image data; and Detecting in the captured image intensity deviations in the illumination pattern provided by the LED matrix illumination device (20) according to any one of aspects 1 to 7; and adjusting a current supplied to at least one LED (22) of the LED matrix illumination device (20) based on the intensity deviation detected in the captured image. (Aspect 11) A computer program product embodied on a non-transitory computer-readable medium, comprising computer program code that, when executed on at least one processor, causes a system to: acquiring image data; analyzing the image data; and Detecting, in the captured image, intensity deviations in the illumination pattern provided by the LED matrix illumination device (20) according to any one of aspects 1 to 7; and adjusting a current supplied to at least one LED (22) of the LED matrix illumination device (20) based on an intensity deviation detected in the captured image.

Claims

1. An LED matrix illumination device (20) for illuminating an illumination pattern with uniform intensity, comprising: a plurality of LEDs (22); a collimating lens (23) in front of each LED (22) for collimating the light of the LED (22); a light-refractive element (24) in front of the collimating lens (23), the light-refractive element (24) being configured to refract a first portion of light from the LED (22) at a different refraction angle (39) than a second portion of light from the LED (22); Equipped with The current supplied to the at least one LED (22) is configured to be adjusted by the data processing device (42) based on the detected non-uniform luminosity of the illumination pattern in the captured image captured and received by the camera; and The LED matrix illumination device (20), wherein the FWHM viewing angle (26) of the collimated light (37) of the LEDs (22) is as large as the difference between the refraction angles (39).

2. The LED matrix illumination device (20) further comprises at least one power supply circuit (35) for the LEDs (22); and 2. The LED matrix illumination device (20) of claim 1, wherein an amount of current supplied to the first portion of LEDs (22) is different from an amount of current supplied to the second portion of LEDs (22).

3. 3. The LED matrix illumination device (20) of claim 1 or 2, wherein the first portion of LEDs (22) comprises one LED (22), one row of LEDs (22) of the LED matrix, or one column of LEDs (22) of the LED matrix.

4. The LED matrix illumination device (20) according to any one of claims 1 to 3, wherein the refraction angle (39) is determined based on the position of the LEDs (22) within the LED matrix illumination device (20).

5. 5. The LED matrix illumination device (20) according to claim 1, wherein the refraction angle (39) is the angle between the optical central axis of the collimated light (37) of the LED (22) and the optical central axis of the refracted light (38) of the same LED (22).

6. The LED matrix illumination device (20) according to any one of claims 1 to 5, wherein the current supplied to at least one LED is adjustable.

7. 1. A machine vision system (40) for detecting defects, holes, blemishes, obvious variations, gray or dark spots, streaks, wrinkles, bubbles, or patterns in a wood fiber web, comprising: An LED matrix illumination device (20) according to any one of claims 1 to 6, at least one imaging device (41) for capturing an image of the illuminated area; a data processing device (42); The machine vision system (40) comprises:

8. 8. The machine vision system (40) of claim 7, wherein the data processing device (42) is configured to analyze image data to detect non-uniform light intensity in the captured image.

9. acquiring image data; analyzing the image data; and - detecting in the captured image non-uniform luminous intensity in the illumination pattern provided by the LED matrix illumination device (20) according to any one of claims 1 to 6; adjusting the current supplied to at least one LED (22) of the LED matrix illumination device (20) based on the intensity deviation detected in the captured image; A method comprising:

10. A computer program product embodied on a non-transitory computer-readable medium, comprising computer program code that, when executed on at least one processor, causes a system to: acquiring image data; analyzing the image data; and - detecting in the captured image non-uniform luminous intensity in the illumination pattern provided by the LED matrix illumination device (20) according to any one of claims 1 to 6; adjusting the current supplied to at least one LED (22) of the LED matrix illumination device (20) based on the intensity deviation detected in the captured image; The computer program product is configured to cause the computer to perform a method comprising:

Images