Surface inspection apparatus and method using high-resolution imaging

Abstract

The present invention provides an apparatus and method for inspecting the optical properties of a surface containing an effect pigment. [Solution] The apparatus (1) comprises a first irradiation device (2) suitable for and used for irradiating the surface of an object to be inspected with radiation in a first irradiation direction (R1) characterized by a first irradiation angle (a1); a second irradiation device (4) suitable for and used for irradiating the surface of an object to be inspected with radiation in a second irradiation direction (R2) characterized by a second irradiation angle (a2); and a first imaging device (6) suitable for capturing an image having spatial resolution of the surface of an object to be inspected irradiated by at least one irradiation device. The apparatus is further characterized by comprising a second imaging device (8) suitable for capturing an image having spatial resolution of the surface of an object to be inspected, particularly the surface of an object to be inspected irradiated by at least one irradiation device.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for inspecting surface characteristics. Although the present invention is described by taking the surface of an automobile as an example, it should be noted that the present invention is also applicable to other surfaces such as the surface of furniture.

Background Art

[0002] In the prior art, so-called multi-angle measuring devices have been known for a long time. In this device, radiation, particularly visible light, is irradiated onto the surface of the inspection object from different directions, the radiation scattered and / or reflected by the surface is analyzed, and / or an image of the irradiated or illuminated surface is captured.

[0003] For this purpose, it is known that a plurality of irradiation devices are provided in a housing, and they irradiate the surface with radiation, particularly light, from different angles. Further, an image camera for capturing an image of the surface illuminated by each irradiation device is often provided.

[0004] So-called effect pigment coatings have been known in the prior art for a long time. These contain effect pigments within the actual coating layer or in its underlying layer, thereby changing the visual impression of the surface. Such an effect pigment layer is optically difficult to detect compared to a conventional surface, and particularly difficult to classify in some cases. Further, the visual impression of such an effect pigment layer also varies greatly depending on the direction of illumination and the direction of observation.

[0005] For this reason, various methods and devices that enable more objective evaluation of these effect pigment surfaces have already been disclosed.

[0006] However, it is desirable to more accurately characterize these surfaces.

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, the present invention is based on the objective of improving the evaluation of such surfaces and enabling more accurate inspection of these surfaces. According to the present invention, this is achieved by the objective of the independent claim. Advantageous embodiments and further developments are the subject of the dependent claims. [Means for solving the problem]

[0008] The apparatus for inspecting the optical properties of a surface, particularly a surface containing an effect pigment, according to the present invention, comprises a first irradiation device suitable for and used for irradiating a surface to be inspected with radiation (particularly light, and more particularly light in the visible wavelength range) in a first irradiation direction characterized by a first irradiation angle. Furthermore, a second irradiation device is provided, suitable for and used for irradiating a surface to be inspected with radiation (particularly light, and more particularly light in the visible wavelength range) in a second irradiation direction characterized by a second irradiation angle.

[0009] Furthermore, a first imaging device is provided which is suitable for and used to acquire an image having spatial resolution of a surface illuminated and / or lit by at least one irradiation direction.

[0010] According to the present invention, the apparatus comprises a second imaging device suitable for and used for capturing images having (in particular, further) spatial resolution of a surface, in particular a surface irradiated and / or illuminated by at least one illumination device.

[0011] Accordingly, the present invention proposes an apparatus that uses (at least) two imaging devices, where these imaging devices preferably have different resolutions and / or enable imaging of a surface at different resolutions (and / or different magnifications of the image relative to the surface).

[0012] A further apparatus for inspecting the optical properties of a surface having an effect pigment according to the present invention comprises a first irradiation device suitable for and used for the purpose of irradiating a surface to be inspected with radiation (particularly light, particularly light in the visible wavelength range) in a first irradiation direction characterized by a first irradiation angle.

[0013] Furthermore, a second irradiation device is preferably provided, which is suitable for and used to irradiate the surface of the object to be inspected with radiation (particularly light, particularly light in the visible wavelength range) in a second irradiation direction characterized by a second irradiation angle.

[0014] Furthermore, a first imaging device is provided that is suitable for and used to capture images having spatial resolution of a surface, particularly a surface irradiated by an illumination device.

[0015] According to the present invention, the apparatus comprises a second imaging device suitable for and used for capturing an image having spatial resolution of a surface, particularly a surface irradiated by (at least one) irradiating device, and an evaluation device suitable for and used for evaluating an image captured by the second imaging device in order to determine at least one characteristic of an effect pigment and / or individual effect pigments.

[0016] Therefore, in both methods, it is proposed to observe the surface using two imaging devices. In the latter case, the properties of the effect pigment, in particular, are determined based on the image (or set of images).

[0017] In a more preferred embodiment, the surface contains the aforementioned so-called effect pigment. Therefore, within the scope of the present invention, it is proposed that the captured image be of (high) resolution such that the effect pigment can be observed at least in groups, preferably individually.

[0018] In a preferred embodiment, the first imaging device and the second imaging device are arranged to observe or capture an image of the same area of ​​the illuminated surface.

[0019] However, it is also conceivable that the second imaging device may capture images of a surface area different from that of the first imaging device, particularly an area offset laterally from the area captured by the first imaging device. This offset is preferably less than 10 cm, more preferably less than 8 cm, even more preferably less than 6 cm, and particularly preferably less than 5 cm. This offset is preferably 0.5 cm or more, more preferably 1.0 cm or more, and particularly preferably 2.0 cm or more.

[0020] Preferably, the second imaging device has an autofocus unit and / or is configured as an autofocus camera module. This is true regardless of where the second imaging device is located.

[0021] The first imaging device may also have an autofocus unit.

[0022] In a further preferred embodiment, the second imaging device includes an additional illumination device that illuminates the area of ​​the surface from which the image is captured by the second imaging device. This may be a ring-shaped illumination device in particular.

[0023] In this configuration, it is proposed that the second imaging device is preferably designed as an independent unit. On the one hand, this means that the first and second imaging devices image different areas of the surface. On the other hand, however, this also means that a beam splitter unit, which is provided when imaging the same area of ​​the surface and / or at the same angle, can be omitted.

[0024] In a more preferred embodiment, the apparatus comprises a further detection device suitable for and used for detecting radiation emitted from the irradiator and reflected by the surface. This detection device may be suitable for and used for detecting the intensity and / or wavelength of radiation reflected by the surface.

[0025] In a further preferred embodiment, the device comprises a further detection device suitable for detecting the intensity of the radiation scattered by the surface and used for that purpose.

[0026] In a further preferred embodiment, the first, preferably at least one irradiation device is suitable for emitting radiation of different colors and is used for that purpose. For example, it is possible to use LEDs that can emit light of different wavelengths. However, it is also conceivable to use a filter arranged in the optical path between the light source (for example, a white light source consisting of one or more LEDs) and the surface of the inspection object. In this way, the control device can control the irradiation of the surface in different colors, particularly in the visible wavelength range.

[0027] In a further preferred embodiment, the first irradiation device comprises a light source and a plurality of color filter devices that can be selectively moved in the optical path between the light source and the surface of the inspection object. Particularly preferably, the irradiation device is rotatable about a predetermined axis of rotation and comprises a filter wheel on which the color filter devices are arranged.

[0028] However, it is also conceivable that such filter elements are movable within the optical path between the surface and at least one detection device and / or imaging device.

[0029] In a further preferred embodiment, the device comprises a second radiation detection device suitable for detecting the radiation emitted, particularly scattered, from the surface of the inspection object at a second emission angle in response to the irradiated radiation and used for that purpose.

[0030] Particularly preferably, the device comprises a further radiation detection device suitable for imaging the radiation emitted, particularly scattered, from the surface of the inspection object at a further emission angle in response to the irradiated radiation and used for that purpose.

[0031] Preferably, the imaging device, and preferably both imaging devices, are arranged to image radiation emitted from the surface of the object being inspected in a direction perpendicular to the surface of the object being inspected.

[0032] Preferably, at least one of the imaging devices is an image camera, and more preferably a color image camera. Particularly preferably, both imaging devices are color image cameras.

[0033] In a more preferred embodiment, the second imaging device has a higher imaging resolution than the first imaging device, or (particularly in combination with an objective lens) achieves a higher image resolution than the first imaging device. In particular, the second imaging device achieves image quality resolution of microscopic images of the surface and / or individual effect pigments.

[0034] Preferably, the first imaging device enables a surface magnification greater than 0.2, preferably greater than 0.3, preferably greater than 0.4, and preferably greater than 0.5 (meaning the image is reduced relative to the actual size of the surface). Preferably, the first imaging device enables surface magnification or magnification at a magnification of less than 1.2, preferably less than 1.0, preferably less than 0.9, and particularly preferably less than 0.8.

[0035] The second imaging device can preferably perform surface magnification and / or magnification, i.e., image magnification relative to the actual surface, at a magnification greater than 2.0, preferably greater than 3.0, and more preferably greater than 4.0.

[0036] Particularly preferably, the second imaging device enables the magnification and / or magnification of the surface or the image of the surface at a magnification of less than 15, preferably less than 12, preferably less than 10, preferably less than 8, preferably less than 7, preferably less than 6. Particularly preferably, the magnification is about 5.

[0037] The first imaging device is preferably suitable for, and used for, capturing images of surfaces suitable for characterizing the visual properties produced by effect pigments.

[0038] The applicant was able to confirm that this approximately 5x magnification was a good compromise, in that it did not overcomplicate the optical system, on the one hand, while on the other hand, it enabled practical image magnification (especially in the inspection of effect pigments).

[0039] In particular, the second imaging device should be suitable for capturing and used for capturing images that are suitable for measuring or determining the characteristics of individual effect pigments (e.g., their size, shape, orientation, color, and / or color gradation) from these images.

[0040] In a more preferred embodiment, the apparatus comprises a housing in which a first irradiation device, optionally a second irradiation device, a first imaging device, and a second imaging device are arranged. Particularly preferably, the housing comprises an opening for the first irradiation device and optionally the second irradiation device to irradiate the surface of the object to be inspected. Preferably, this opening is the only opening within the housing from which light from the outside can reach the imaging device and / or radiation can leak out of the housing.

[0041] In a preferred embodiment, the device is a portable device, or a device that can be carried by a user without the use of assistive devices.

[0042] Preferably, the weight of the device is less than 3 kg, preferably less than 2 kg, and particularly preferably less than 1 kg. Preferably, a control device for controlling the irradiation device and / or imaging device is also located within the housing. Furthermore, a storage device for storing captured images is also provided within the housing.

[0043] Particularly preferably, the objective lens described above is housed within this housing.

[0044] In a more preferred embodiment, a first imaging device is assigned a first objective lens, and / or a second imaging device is assigned a second objective lens, where the second objective lens preferably has a longer focal length than the first objective lens.

[0045] Preferably, at least one aperture is located in the optical path between the surface to be inspected and the second imaging device. Preferably, multiple apertures are located in this optical path. Particularly preferably, at least one of these apertures is located in one of the objective lenses, particularly the second objective lens.

[0046] Particularly preferably, the length of the second objective lens (along the optical path) is at least 1.5 times, preferably at least 2.0 times, the length of the first objective lens.

[0047] Particularly preferably, the two objective lenses extend in different directions, and especially preferably in directions perpendicular to each other. Particularly preferably, the objective lenses extend in the same plane.

[0048] In a more preferred embodiment, the first and second imaging devices are arranged to image the surface at the same imaging angle. In particular, the first and second imaging devices, or their arrangement, make it possible to observe the surface from a substantially perpendicular direction. A substantially perpendicular observation direction means that the observation angle deviates by no more than 10°, preferably 7°, more preferably 5°, and even more preferably 3° from the exact perpendicular direction.

[0049] The first and second imaging devices can, or may, enable imaging of the surface at different imaging angles.

[0050] In a more preferred embodiment, the apparatus includes a first beam splitter device positioned between the imaging device and the surface to be inspected. This beam splitter device can be used, for example, to ensure that both imaging devices observe the surface from the same angle. This beam splitter device can be designed so that the same amount of light reaches both imaging devices.

[0051] However, it is also possible and preferable to design the beam splitter device so that more light reaches the second imaging device. Preferably, the ratio of the amount of radiation reaching the first imaging device to the amount of radiation reaching the second imaging device is 1:1 to 1:5, preferably 1:1 to 1:4, more preferably 1:1 to 1:3, and particularly preferably 1:1.5 to 1:3.

[0052] In a more preferred embodiment, the apparatus includes a second beam splitter device positioned between the imaging device and the surface. This allows coupling to different photodetectors and / or imaging devices at two different locations.

[0053] Particularly preferably, the first beam splitter device and the second beam splitter device are arranged in the optical path between the surface and at least one imaging device, and preferably in series in the optical path between the surface and both imaging devices.

[0054] In a more preferred embodiment, at least one beam splitter device is selected from a group of beam splitter devices comprising a beam splitter plate, a beam splitter cube, and a pellicle. The pellicle is an ultrathin and ultralight translucent mirror used in the light spot of an optical instrument to split a beam of light into two parallel beams of light with reduced light intensity. Splitting the beam of light makes it possible to use it for multiple purposes simultaneously. The pellicle effectively eliminates overlap of beams and images due to non-conjugate weak secondary reflections from nominally non-reflective surfaces.

[0055] Preferably, the pellicle has an extremely thin film, in particular a cellulose film, more specifically an optical-quality nitrocellulose film (or film), which is stretched and bonded onto the body, in particular a ring, more specifically an aluminum ring. In its function, the pellicle beam splitter serves the same purpose as a conventional plate beam splitter. More specifically, a plate beam splitter (or "mirror" beam splitter) produces two reflected lights for a single incident light. One light is reflected from the first (or front) surface, and the other is reflected from the second (or back) surface.

[0056] As a result, so-called "ghost images" or secondary reflections occur. Furthermore, due to the thickness of the glass substrate (1-3 mm depending on the size), plate beam splitters slightly shift the transmitted beam laterally relative to the input beam. For these reasons, plate beam splitters minimize these effects and perform best when the glass thickness is minimal, the coated surface is aligned with the light source, they are used with collimated beams, and the back surface has an AR (anti-reflective) coating.

[0057] In a more preferred embodiment, the apparatus comprises a third irradiation device suitable for and used for irradiating the surface of an object to be inspected with radiation in a third irradiation direction characterized by a third irradiation angle.

[0058] Preferably, the irradiation angle at which the irradiation device irradiates the surface with radiation is between 30 and 60 degrees with respect to the vertical, preferably between 35 and 55 degrees, more preferably between 40 and 50 degrees, and particularly preferably between 42 and 48 degrees.

[0059] Preferably, the first and / or second irradiation device emits directional radiation. Preferably, the first and / or second irradiation device comprises a light source having at least one white LED.

[0060] Preferably, the irradiation angle at which the irradiation device irradiates the surface with radiation is between 60 and 90 degrees, preferably between 65 and 85 degrees, preferably between 70 and 80 degrees, and particularly preferably between 72 and 78 degrees with respect to the vertical. Preferably, the irradiation device irradiates directional radiation. Preferably, the first irradiation device and / or the second irradiation device comprises a light source having at least one white LED in the form of a light source.

[0061] Preferably, the irradiation angle at which the irradiation device irradiates the surface with radiation is between 5 and 25 degrees with respect to the vertical, preferably between 10 and 20 degrees, preferably between 12 and 18 degrees, and particularly preferably between 14 and 16 degrees. Preferably, the irradiation device irradiates directional radiation. Preferably, the first irradiation device and / or the second irradiation device comprises a light source having at least one white LED in the form of a light source.

[0062] In a more preferred embodiment, diffuse illumination of the surface is also provided. White LEDs can be used for this purpose as well. An integrating sphere can be used to realize this diffuse illumination.

[0063] In this case, the light is preferably shone onto the surface from at least three different angles.

[0064] The apparatus preferably comprises a fourth irradiation device suitable for and used to irradiate the surface of an object to be inspected with radiation in a fourth irradiation direction characterized by a fourth irradiation angle. Thus, in this configuration, light is irradiated onto the surface from at least four different directions.

[0065] In a more preferred embodiment, the apparatus comprises a further illumination device suitable for and used for diffusing illumination of a surface. Preferably, this further illumination device also comprises at least one white LED.

[0066] Preferably, a scattering surface, particularly in the form of a so-called Ulbricht sphere, is provided to generate this diffuse illumination. The Ulbricht sphere is a component of optical technology. It is used as a light source to obtain diffuse radiation from directional radiation or to collect radiation from a light source with a large divergence angle.

[0067] This is preferably a hollow sphere that performs diffuse reflection internally, and its surface is provided with an exit aperture (often positioned perpendicular to the light entrance aperture). The light or radiation source is positioned in front of the light entrance aperture. The internal coating is made of a material with the best possible diffuse reflection properties. Barium sulfate (BaSO4) is a preferred material. However, good reflection properties can also be obtained over a wide wavelength range using optical PTFE.

[0068] It is preferable to provide a control device that ensures that only a maximum of one irradiation device irradiates the surface with radiation within a predetermined time period.

[0069] In a more preferred embodiment, the second imaging device is capable of achieving an image resolution in the range of 1500 × 1200 to 3000 × 2500, preferably 2000 × 1500 to 2800 × 2300, and particularly preferably 2300 × 1800 to 2700 × 2000, with an effective pixel count.

[0070] Preferably, the pixel size is between 1.0 μm × 1.0 μm and 4.0 μm × 4.0 μm, more preferably between 1.2 μm × 1.2 μm and 3.0 μm × 3.0 μm, and even more preferably between 1.5 μm × 1.5 μm and 2.5 μm × 2.5 μm.

[0071] In a more preferred embodiment, the focal length of the objective lens associated with the second imaging device is greater than 1.0 mm, preferably greater than 2.0 mm, preferably greater than 2.5 mm, preferably greater than 3.0 mm, preferably greater than 3.5 mm, preferably greater than 4.0 mm, and particularly preferably greater than 4.5 mm.

[0072] Preferably, the focal length of the objective lens associated with the second imaging device is less than 50 mm, preferably less than 40 mm, preferably less than 30 mm, preferably less than 20 mm, preferably less than 15 mm, preferably less than 10 mm, preferably less than 8.0 mm, preferably less than 7.0 mm, and particularly preferably less than 6.0 mm.

[0073] In a more preferred embodiment, the focal length of the objective lens associated with the first imaging device is greater than 2.0 mm, preferably greater than 3.0 mm, preferably greater than 4.0 mm, preferably greater than 6.0 mm, preferably greater than 8.0 mm, preferably greater than 10.0 mm, and particularly preferably greater than 12.0 mm.

[0074] Preferably, the focal length of the objective lens associated with the first imaging device is less than 50 mm, preferably less than 45 mm, preferably less than 40 mm, preferably less than 35 mm, preferably less than 30 mm, preferably less than 25 mm, preferably less than 20 mm, preferably less than 18.0 mm, and particularly preferably less than 16.0 mm.

[0075] These focal lengths have been demonstrated to be particularly preferable for achieving good surface imaging (especially when installation space is limited).

[0076] In a more preferred embodiment, the properties of the effect pigment are selected from a group of properties consisting of the size of the effect pigment, the geometric shape of the effect pigment, the color of the effect pigment, the curvature of the effect pigment, the orientation of the effect pigment, the inclination of the effect pigment within the surface, the manufacturer of the surface, the manufacturer of the effect pigment, the material of the effect pigment, and similar properties.

[0077] In a more preferred embodiment, the evaluation device is suitable for and used for determining characteristic properties of the effect pigment using artificial intelligence.

[0078] Preferably, the image evaluation of images captured by the second imaging device is performed using artificial intelligence. Particularly preferably, a machine learning image evaluation model is created for image evaluation.

[0079] The machine learning-based image evaluation model is preferably based on an (artificial) neural network. The neural network is preferably a deep neural network (DNN) having multiple processing layers as a parameterizable processing chain, and / or a so-called convolutional neural network (CNN) and / or recurrent neural network (RNN).

[0080] Preferably, the data (to be processed), particularly images with spatial resolution (or data derived therefrom), is supplied as input variables to an image evaluation model or (artificial) neural network. Preferably, the image evaluation model or artificial neural network maps the input variables to output variables as a function of a parameterizable processing chain, where the output variables preferably include the type of effect pigment, the size of the effect pigment and / or individual effect pigments, the size range of the effect pigment and / or individual effect pigments, the number of effect pigments per unit area, the size variation of the effect pigments, the slope of the effect pigment and / or individual effect pigments, the curvature of the effect pigments, the color of the effect pigments, the curvature profile of the effect pigments and / or individual effect pigments, or the type of effect pigments (i.e., whether they are metallic effect pigments, pearlescent pigments, interference pigments, or glitter pigments).

[0081] Preferably, the machine learning-based image evaluation model is trained using predetermined training data, and in that training, the parameterizable processing chain is parameterized.

[0082] A preferred method is to use training data consisting of multiple images with spatial resolution (images of the surface of the object to be inspected, including effect pigments) captured by at least one imaging device, particularly a second imaging device, in the training process of the image evaluation model. This has the advantage that the learning process is already specifically adapted to the inspection and / or imaging device (including its optical system) in use and / or planned for use, and therefore can directly take into account specific conditions of a particular device, such as the optical properties of the imaging device or specific lighting conditions within the inspection device.

[0083] Preferably, spatial resolution images intended for use as training data (captured by at least one imaging device, i.e., a second imaging device) are assigned (surface) type and / or classification features.

[0084] Furthermore, parameters used for optical settings when capturing individual images, such as the aperture, lens, or objective lens used, can also be used to create training data.

[0085] Preferably, spatial resolution images are stored and / or used as training datasets (particularly on volatile and / or non-volatile storage devices) along with surface type and / or effect pigment type and / or features characteristic of the effect pigment (such as color, material, manufacturer, and type of effect pigment), and / or classification features. Preferably, multiple training datasets are generated in this manner.

[0086] Classification features preferably include the type of effect pigment, the genus of the effect pigment (i.e., whether it is a metallic effect pigment, pearlescent pigment, interference pigment, or glitter pigment), the size of the effect pigment and / or the size of individual effect pigments, the size range of the effect pigment and / or the size range of individual effect pigments, the number of effect pigments per unit area, the size dispersion of the effect pigment, the gradient of the effect pigment and / or the gradient of individual effect pigments, the curvature of the effect pigment, the color of the effect pigment, the curvature profile of the effect pigment or individual effect pigments, the manufacturer or surface of the effect pigment, or the characteristics of any further layers of the surface.

[0087] The use of machine learning-based image evaluation models ensures that the optimal combination of different (complex) features and / or reference ranges (in the learning process) for data processing, as well as features (or feature combinations) adapted to a wide variety of surface types and / or effect pigment types, are identified or determined.

[0088] This offers the advantage of being able to accurately determine the characteristic parameters (size, color, gradient, density, etc.) of the surface and / or effect pigments when evaluating at least one spatial resolution image using a trained image evaluation model.

[0089] Furthermore, effect pigments may also differ in other properties such as brightness, dynamics, density, color gradation, or saturation.

[0090] The effective pigment preferably has an intermediate particle area of ​​15 μm 2 From 700 μm 2 The range is, more preferably 30 μm 2 From 500 μm 2 It is within the range.

[0091] The effect pigments can be selected from the following types, for example:

[0092] The effect pigment may be, for example, a metallic effect pigment (e.g., aluminum flakes). These preferably have a particle size of 5 to 50 μm. Smaller particles, especially those with a particle size of 5 to 20 μm, produce a smooth and delicate metallic appearance. Larger particles (especially those with a particle size of 20 to 50 μm) produce a more intense and shimmering effect.

[0093] Furthermore, as effect pigments, pearlescent pigments mainly composed of glimmer, titanium dioxide, or silicon dioxide can also be used. These preferably have a particle size of 5 to 60 μm. Fine particles (especially those with a particle size of 5 to 20 μm) produce a delicate, silky luster. Coarser particles (especially those with a particle size of 20 to 60 μm) result in a stronger color shimmer and reflective effect.

[0094] Furthermore, the effect pigments may also be interference pigments. These preferably have a particle size of 5 to 50 μm. They are often compared to pearlescent pigments because they are based on similar materials.

[0095] Finally, the effect pigment may be a glitter pigment. These preferably have a particle size of 5 to 200 μm (or more). Such glitter pigments produce an impressive glitter effect and are often used in specialty paints and tuning paints.

[0096] The effect pigment may comprise one or more oxide layers.

[0097] The effect pigment is preferably in the form of effect pigment flakes. These are preferably incorporated into a surface layer or a coating layer on a surface.

[0098] In a more preferred embodiment, the magnification of at least the second imaging device is variable, thereby enabling adaptation to different surfaces.

[0099] In a more preferred embodiment, at least one imaging device and / or at least one objective lens associated with at least one imaging device (preferably both imaging devices and / or objective lenses associated with them) are equipped with an autofocus device. This is particularly useful because each magnifying optical system, including the one associated with the second imaging device, has a relatively shallow depth of field.

[0100] In a more preferred embodiment, the evaluation device includes a storage device that stores reference data of an effect pigment or group of effect pigments. Furthermore, captured images or image data can also be stored in this storage device.

[0101] The present invention further relates to a method for inspecting the optical properties of a surface, particularly a surface coated with an effect pigment. In this method, a first irradiation device irradiates the surface to be inspected with radiation in a first irradiation direction characterized by a first irradiation angle, and preferably a second irradiation device irradiates the surface to be inspected with radiation in a second irradiation direction characterized by a second irradiation angle (where the first and second irradiation angles are preferably different). A first imaging device captures an image of the surface irradiated by at least one irradiation device having at least one spatial resolution.

[0102] According to the present invention, the second imaging device acquires an image having spatial resolution of a surface, particularly a surface irradiated by at least one illumination device.

[0103] Preferably, the image captured by the second imaging device is a color image; that is, the second imaging device is preferably suitable for capturing color images and is used for that purpose. Preferably, the first imaging device is also suitable for capturing color images and is used for that purpose.

[0104] The present invention further relates to a method for inspecting the optical properties of a surface, particularly a surface coated with an effect pigment. In this method, a first irradiation device irradiates the surface to be inspected with radiation in a first irradiation direction characterized by a first irradiation angle.

[0105] Preferably, the second irradiation device also irradiates the surface of the object to be inspected with radiation in a second irradiation direction defined by the second irradiation angle.

[0106] Furthermore, the first imaging device acquires an image having at least one spatial resolution of the surface of the object to be examined, which has been irradiated by the irradiation device or at least one irradiation device.

[0107] Furthermore, the evaluation device evaluates the images captured by the second imaging device and determines at least one characteristic of the effect pigment and / or individual effect pigments.

[0108] A more preferable method is for the second imaging device to acquire surface images with higher resolution than the first imaging device, particularly microscopic images of the surface.

[0109] Particularly preferably, the second imaging device magnifies the captured image (with respect to the surface of the object to be inspected) at a predetermined magnification, where this magnification is preferably greater than 2, preferably greater than 3, and preferably greater than 4. This magnification is preferably less than 40, preferably less than 30, preferably less than 25, preferably less than 20, preferably less than 15, preferably less than 8, and preferably less than 6.

[0110] Preferably, the irradiation device irradiates the surface with two, preferably multiple, different colors or wavelengths.

[0111] A more preferred method is for the first and second imaging devices to capture images of the surface at the same imaging angle.

[0112] A more preferred method is for the second imaging device to enlarge the captured image (relative to the actual surface) by more than 2 times, preferably more than 3 times, preferably more than 4 times, preferably more than 5 times, or 5 times.

[0113] Preferably, the second imaging device enables magnification of less than 20 times (relative to the surface), preferably less than 15 times, preferably less than 10 times, preferably less than 8 times, particularly preferably less than 7 times, and even more preferably less than 6 times.

[0114] A more preferred method is to split the radiation reflected and / or scattered by the surface by a beam splitter before it reaches a second imaging device. Particularly preferred is that the optical path from the surface under inspection to the imaging device passes through at least two beam splitter devices.

[0115] Preferably, the surface is irradiated from at least three different angles, preferably at least four different angles.

[0116] Furthermore, it is preferable that light is shone onto the surface at a 45-degree angle, and that the radiation reflected from the surface is detected by a detection device. Preferably, a detection device is provided to detect the intensity of the radiation incident on it.

[0117] Particularly preferably, the color of light irradiated onto the surface by at least one irradiation device is altered. This is preferably done by a filter set and / or a filter wheel.

[0118] Preferably, the surface of the object to be inspected is exposed by a second imaging device for an exposure time of more than 1 ms, preferably more than 2 ms, preferably more than 4 ms, preferably more than 6 ms, preferably more than 8 ms, preferably more than 10 ms, preferably more than 12 ms, preferably more than 14 ms, preferably more than 16 ms, preferably more than 18 ms, preferably more than 20 ms, and preferably more than 25 ms.

[0119] Preferably, the surface to be inspected is imaged by a second imaging device with an exposure time of less than 500 ms, preferably less than 400 ms, preferably less than 300 ms, preferably less than 200 ms, preferably less than 150 ms, preferably less than 120 ms, preferably less than 100 ms, particularly preferably less than 90 ms, and even more particularly preferably less than 85 ms.

[0120] Preferably, the apparatus and / or method described herein is designed to inspect both the original surface, for example, the original surface of an object, in particular the original surface of an automobile, i.e., the surface present in the automobile in its state of manufacture, and any subsequent surfaces (for example, as a result of an accident).

[0121] Preferably, the surface to be inspected is a painted surface. Preferably, these surfaces have a thickness (perpendicular to the direction of surface extension) greater than 20 μm, preferably greater than 40 μm, preferably greater than 60 μm, and particularly preferably greater than 80 μm. In a more preferred embodiment, the surface thickness is less than 400 μm, preferably less than 350 μm, and preferably less than 200 μm.

[0122] The surface to be inspected is preferably composed of at least 3 layers, preferably at least 4 layers, and particularly preferably at least 5 layers. The surface to be inspected is preferably composed of up to 12 layers, preferably up to 10 layers, and even more preferably up to 8 layers.

[0123] These specifications are extremely important with respect to the optical parameters of the second imaging device and / or the objective lens associated with the second imaging device. Preferably, the effect pigment is placed in the intermediate layer of the surface of the object to be inspected.

[0124] For further advantages and practical details, please refer to the following description in conjunction with the drawings. [Brief explanation of the drawing]

[0125] [Figure 1] A schematic diagram of the apparatus according to the present invention is shown. [Figure 1a] A schematic diagram of another apparatus according to the present invention is shown. [Figure 2a] A detailed view of the apparatus shown in Figure 1 is provided. [Figure 2b] A detailed view of the apparatus shown in Figure 1 is provided. [Figure 2c] A detailed view of the apparatus shown in Figure 1 is provided. [Figure 3] The image shown was captured by the second imaging device. [Figure 4a] Three views of further embodiments of the apparatus according to the present invention are shown. [Figure 4b] Three views of further embodiments of the apparatus according to the present invention are shown. [Figure 4c] Three views of further embodiments of the apparatus according to the present invention are shown. [Modes for carrying out the invention]

[0126] Figure 1 shows a schematic diagram of the apparatus 1 according to the present invention. This apparatus comprises an optical block 51 and a housing 50 in which electrical and optical components, described later, are arranged. The housing has an opening 52 through which the surface 10 to be inspected can be illuminated or irradiated, and radiation reflected and / or scattered by the surface returns to the inside of the housing 50.

[0127] Reference numeral 2 indicates a first irradiation device that irradiates radiation, particularly light, in the irradiation direction R1 and at an irradiation angle a1 with respect to the surface 10. Preferably, a filter wheel (not shown in detail) is provided in the optical path between the first irradiation device 2 and the surface. This filter wheel preferably has multiple color filters, which allow light of different colors or wavelengths to be irradiated onto the surface 10.

[0128] Reference numeral 4 indicates a second (optional) irradiation device, which irradiates surface 10 with radiation, in particular light, in irradiation direction R2 and irradiation angle a2 with respect to surface 10.

[0129] Reference numeral 32 indicates a third (optional) irradiation device which irradiates the surface 10 with radiation, in particular light, in a further irradiation direction and at a further irradiation angle to the surface 10.

[0130] Reference numeral 6 denotes a first imaging device positioned perpendicular to the surface 10 and capturing a first image of this surface. For this purpose, the first imaging device preferably captures radiation scattered by the surface 10 (or a portion thereof).

[0131] Preferably, this first imaging device 6 and its associated optical system enable image magnification of approximately 0.7 times. Preferably, the size of the corresponding observation spot is between 6.0 mm × 4.0 mm and 12.0 mm × 9.00 mm, preferably between 7.0 mm × 5.0 mm and 9.0 mm and 7.0 mm.

[0132] Preferably, the image scale of this first imaging device is between 2.0 μm / pixel and 4.0 μm / pixel.

[0133] Reference numeral 8 indicates a second imaging device, preferably arranged in combination with an optical system described later, to capture an image of a surface irradiated by at least one irradiator in a vertical direction. As described above, the second imaging device can capture images with significantly higher resolution than the first imaging device. Reference numeral 25 indicates an aperture.

[0134] Preferably, this second imaging device 8 and its associated optical system enable image magnification of approximately 5 times. Preferably, the size of the corresponding observation spot is between 0.9 mm × 0.6 mm and 1.8 mm × 1.6 mm, preferably between 1.0 mm × 0.8 mm and 1.4 mm and 1.1 mm.

[0135] Preferably, the image scale of this second imaging device is between 0.3 μm / pixel and 0.55 μm / pixel.

[0136] Reference numeral 28 indicates a lens, particularly a chromatic aberration correction lens, which preferably forms an entrance for radiation emitted from the surface to enter the imaging device.

[0137] Preferably, the distance between the lens 28 and the surface 10 is greater than 20 mm, preferably greater than 30 mm, preferably greater than 40 mm, and particularly preferably greater than 45 mm. Preferably, the distance between the lens 28 and the surface is less than 90 mm, preferably less than 80 mm, preferably less than 70 mm, preferably less than 60 mm, and particularly preferably less than 55 mm.

[0138] Figure 1a shows a further embodiment of the apparatus according to the present invention, in which a second imaging device is omitted for clarity. This apparatus comprises a generator 60 that generates diffuse radiation in the form of a so-called Ulbricht sphere (integrating sphere) 60. Reference numeral 62 indicates an illumination device, such as a white light LED, for illuminating the generator 60.

[0139] Figure 2a schematically shows an optical structure or optical arrangement that enables images to be captured by two imaging devices 6 and 8. Light emitted from surface 10 travels along a straight line perpendicular to the surface (not shown) upwards.

[0140] Reference numeral 42 indicates a first lens assembly through which radiation emitted from the surface passes.

[0141] Reference numeral 22 indicates a beam splitter that allows a portion of the radiation to pass through and then splits another portion to reflect to another radiation detection device (not shown). This other radiation detection device is suitable for and provided for detecting the intensity of the radiation incident upon it. Preferably, a portion of this radiation is reflected in a direction perpendicular to the plane of the drawing.

[0142] Reference numeral 44 indicates a second lens assembly through which radiation emitted from the surface passes. This second lens assembly is preferably located between the first beam splitter device 22 and the second beam splitter device 24.

[0143] Reference numeral l1 indicates the distance between the first lens assembly 42 and the second lens assembly. This distance is preferably greater than 10 mm, preferably greater than 12 mm, preferably greater than 14 mm, preferably greater than 16 mm, preferably greater than 18 mm, and particularly preferably greater than 20 mm. Furthermore, this distance l1 is preferably less than 50 mm, preferably less than 40 mm, preferably less than 35 mm, preferably less than 30 mm, and particularly preferably less than 25 mm. These limit values ​​for distance were determined by the applicant through extensive research to achieve a particularly favorable design of the optical system.

[0144] Reference numeral 24 indicates the beam splitter referred to as the first beam splitter device described above, which divides the radiation incident on it into a first portion that reaches the first imaging device 6 and a second portion (preferably larger than the first portion) that reaches the second imaging device 8.

[0145] Reference numeral 16 indicates the first objective lens associated with the first imaging device 6, and reference numeral 18 indicates the second objective lens associated with the second imaging device 8. It can be seen that the second objective lens 18 is considerably longer than the first objective lens 16.

[0146] Preferably, the second objective lens is at least twice as long as the first objective lens. Preferably, the second objective lens is up to four times as long as the first objective lens 16. Preferably, the second objective lens 18 extends perpendicularly to the first objective lens 16.

[0147] A lens assembly 46 is positioned inside the first objective lens 16, and a second lens assembly 48 is positioned inside the second objective lens 18.

[0148] Therefore, as a whole, an optical system 30 is provided that enables imaging by the first imaging device 6 and the second imaging device 8. Preferably, the optical system 30 comprises at least two separate lens assemblies, preferably three separate lens assemblies, and particularly preferably four separate lens assemblies.

[0149] Reference numeral 36 indicates a first aperture, which is preferably located within the first objective lens 16. Preferably, the first aperture 36 is located between the beam splitter device 24 and the first imaging device. Preferably, the cross-sectional dimensions of this aperture are greater than 0.5 mm, preferably greater than 1.0 mm, and more preferably greater than 1.5 mm. Preferably, the cross-sectional dimensions of this aperture are less than 10 mm, preferably less than 8.0 mm, preferably less than 6.0 mm, particularly preferably less than 4.0 mm, and more particularly preferably less than 3.0 mm.

[0150] Reference numeral 38 indicates a second opening, which is preferably located between the beam splitter plates. Preferably, the cross-sectional dimensions of this second opening are greater than 2.0 mm, preferably greater than 4.0 mm, and preferably greater than 6.0 mm. Preferably, the cross-sectional dimensions of this second opening are less than 16 mm, preferably less than 14.0 mm, preferably less than 12.0 mm, particularly preferably less than 10.0 mm, and even more particularly preferably less than 9.0 mm.

[0151] Preferably, the opening size of this second opening is greater than 8 mm, preferably greater than 10 mm, preferably greater than 11 mm, particularly preferably greater than 12 mm, particularly preferably greater than 14 mm, and even more particularly preferably greater than 15 mm.

[0152] Preferably, the aperture size of the second aperture 36 is less than 25 mm, preferably less than 22 mm, preferably less than 20 mm, preferably less than 18 mm, and particularly preferably less than 17 mm. Preferably, the first aperture 36 is located between the beam splitter device 24 and the second imaging device 8.

[0153] Reference numeral l2 indicates the distance between the lens assembly 44 and the first aperture.

[0154] This distance is preferably greater than 6 mm, preferably greater than 8 mm, preferably greater than 10 mm, preferably greater than 11 mm, preferably greater than 12 mm, and particularly preferably greater than 14 mm. Furthermore, this distance is preferably less than 40 mm, preferably less than 30 mm, preferably less than 25 mm, preferably less than 20 mm, and particularly preferably less than 17 mm. These limit values ​​for distance were determined by the applicant through extensive research to achieve a particularly favorable design of the optical arrangement.

[0155] Figure 2b shows a further embodiment of the optical structure. In this embodiment, beam splitter cubes 22a and 24a are used instead of beam splitter plates 22 and 24.

[0156] Figure 2c shows the optical system inside the housing of the device.

[0157] Figure 3 shows an example of an image captured by the second imaging device. This image was captured with a free transmission distance of 16 mm for the first lens group and an exposure time of 30 ms.

[0158] Here, multiple individual effect pigments can be identified. By using appropriate image analysis and, if necessary, artificial intelligence (AI), a wide variety of data about the effect pigments can be output. For example, it is possible to identify the color of the effect pigment or to determine the proportion of effect pigments with a specific color.

[0159] Furthermore, it is possible to determine the number of effect pigments per unit area. It is also possible to determine values ​​such as the size of individual effect pigments and the average size of the effect pigments. In addition, it is possible to determine the curvature of the effect pigments and values ​​characteristic of the color behavior of the effect pigments, such as their behavior when irradiated from different directions.

[0160] In order to make an objective judgment about the effective pigments, it is preferable for the AI ​​to utilize a very large number of images, as shown in Figure 3.

[0161] Figures 4a to 4c show further embodiments of the apparatus 1 according to the present invention. Here again, a first imaging device 6 and a second imaging device 8 are provided. Preferably, the second imaging device is an imaging device equipped with an autofocus unit and / or the imaging device has an autofocus function.

[0162] However, in the embodiments shown in Figures 4a to 4c, as shown in Figure 4b, the second imaging device 8 is positioned laterally adjacent to the first imaging device 6. Preferably, the second imaging device observes a slightly different or offset area of ​​the surface of the object to be inspected compared to the first imaging device.

[0163] In this embodiment, it is proposed that the second imaging device be configured as an independent unit. Reference numeral 82 indicates an objective lens 82 with a lens 84. Reference numeral 86 indicates an illumination device for illuminating the surface. This illumination device is preferably configured as a ring illumination and is preferably positioned to at least partially surround the lens 84 with respect to the observation direction. Preferably, this illumination device comprises at least one, and particularly preferably more than one, LED.

[0164] Therefore, preferably, the second imaging device 8 also observes the surface 10 from a vertical direction, but as described above, preferably observes a region of the surface 10 that is offset laterally.

[0165] It should be noted that all features described in this method are also disclosed for the corresponding apparatus. This means, in particular, that the corresponding apparatus is suitable for performing each method and comprises the apparatus used for that purpose. Furthermore, the features described for the apparatus are also applicable to the method or group of methods. This means that the method is performed using the features of the corresponding apparatus.

[0166] The applicant reserves the right to claim all features disclosed in the application documents as essential elements of the invention, insofar as they are novel to the prior art, individually or in combination. It should also be noted that individual drawings may contain features that are advantageous in themselves. A person skilled in the art will immediately recognize that certain features described in a drawing may be beneficial without employing other features in that drawing. Furthermore, a person skilled in the art will recognize that advantages can also be obtained from combinations of multiple features shown in individual drawings or different drawings.

Claims

1. An apparatus (1) for inspecting the optical properties of a surface, comprising: a first irradiation device (2) suitable for and used for irradiating a surface to be inspected with radiation in a first irradiation direction (R1) characterized by a first irradiation angle (a1); a second irradiation device (4) suitable for and used for irradiating a surface to be inspected with radiation in a second irradiation direction (R2) characterized by a second irradiation angle (a2); and a first imaging device (6) suitable for capturing an image having spatial resolution of the surface irradiated by at least one of the irradiation devices. The apparatus is characterized by comprising a second imaging device (8) suitable for capturing an image having spatial resolution of a surface, particularly the surface irradiated by at least one of the irradiating devices.

2. The apparatus according to claim 1, wherein the second imaging device (8) enables a higher imaging resolution than the first imaging device (6), and in particular, the second imaging device (8) enables microscopic images of the surface.

3. The apparatus according to claim 1 or 2, wherein the apparatus has a housing (50) in which the first irradiation device (2), the second irradiation device (4), the first imaging device (6), and the second imaging device (8) are arranged, and the housing preferably has at least one opening (52) for the first and second irradiation devices to irradiate the surface (10) to be inspected.

4. The apparatus according to any one of claims 1 to 3, wherein the first imaging device (6) is assigned a first objective lens (16), and the second imaging device (8) is assigned a second objective lens (18), and the second objective lens (18) preferably has a longer focal length than the first objective lens (16).

5. The apparatus according to any one of claims 1 to 4, characterized in that the first imaging device (6) and the second imaging device (8) are arranged to image the surface at the same imaging angle, or the first imaging device (6) and the second imaging device are arranged to image two different regions of the surface.

6. The apparatus according to any one of claims 1 to 5, characterized in that the apparatus (1) comprises a first beam splitter apparatus (22) disposed between the imaging apparatus (6, 8) and the surface.

7. The apparatus according to claim 6, wherein the apparatus (1) comprises a second beam splitter apparatus (24) disposed between the imaging apparatus (6, 8) and the surface, and the first beam splitter apparatus (22) and the second beam splitter apparatus (24) are preferably arranged in series in the optical path between the surface and at least one of the imaging apparatus, and preferably in the optical path between the surface and both of the imaging apparatus.

8. The apparatus according to any one of claims 1 to 7, wherein the apparatus (1) comprises a third irradiation device (32) suitable for and used for irradiating the surface of an object to be inspected with radiation in a third irradiation direction characterized by a third irradiation angle, and the apparatus (1) comprises a fourth irradiation device suitable for and used for irradiating the surface of an object to be inspected with radiation in a fourth irradiation direction characterized by a fourth irradiation angle.

9. The apparatus according to any one of claims 1 to 8, characterized in that the second imaging apparatus enables an image resolution higher than 2 MP, preferably higher than 3 MP, more preferably higher than 4 MP, and particularly preferably higher than 5 MP.

10. The apparatus according to any one of claims 1 to 9, characterized in that the second imaging device (8) enables magnification of more than 2 times, preferably more than 4 times, preferably more than 5 times, and / or the second imaging device (8) enables magnification of less than 20 times, preferably less than 15 times, preferably less than 10 times, preferably less than 8 times.

11. The apparatus according to any one of claims 1 to 10, characterized in that the focal length of the objective lens associated with the second imaging device is greater than 1 mm, preferably greater than 1.5 mm, preferably greater than 2.0 mm, preferably greater than 2.5 mm, preferably greater than 3.0 mm, particularly preferably greater than 3.5 mm, particularly preferably greater than 4.0 mm, and / or the focal length of the objective lens associated with the second imaging device is less than 50 mm, preferably less than 40 mm, preferably less than 30 mm, preferably less than 20 mm, preferably less than 15 mm, preferably less than 10 mm, particularly preferably less than 6 mm.

12. A method for inspecting the optical properties of a surface, particularly a surface coated with an effect pigment, comprising: a first irradiation device (2) irradiating the surface to be inspected with radiation in a first irradiation direction (R1) characterized by a first irradiation angle (a1); a second irradiation device (4) irradiating the surface to be inspected with radiation in a second irradiation direction (R2) characterized by a second irradiation angle (a2); and a first imaging device (6) capturing an image of the surface irradiated by at least one of the irradiation devices having at least one spatial resolution. A method characterized in that a second imaging device (8) captures an image having spatial resolution of a surface, particularly the surface irradiated by at least one of the irradiating devices.

13. The method according to claim 12, characterized in that the second imaging device captures a high-resolution image of the surface, particularly a microscopic image of the surface.

14. The method according to claim 12 or 13, characterized in that the first imaging device (6) and the second imaging device (8) capture an image of the surface at the same imaging angle.

15. The method according to any one of claims 12 to 14, characterized in that the second imaging device (8) magnifies the captured image by more than 2 times, preferably more than 4 times, preferably more than 5 times, and / or the second imaging device (8) enables magnification of less than 20 times, preferably less than 15 times, preferably less than 10 times, preferably less than 8 times.

Images