Apparatus and method for examining surface properties

Abstract

The invention relates to a method for examining optical surface properties of a surface (10) to be examined, including the following steps: - using an irradiation device (22) to radiate radiation onto the surface (10) to be examined; - using a radiation capturing device (24) having a maximal capturing area (K) for capturing the radiation reaching it to record a spatially resolved image of the radiation that is output and, in particular, reflected by the surface (10) in response to the radiation radiated in; - ascertaining at least one effective area value (W) that is characteristic of an area located in a predetermined and / or predeterminable measuring area (M) within the maximal capturing area (K) and reached by the output, in particular reflected, radiation in a predetermined and / or predeterminable manner, in particular in respect of a brightness and / or color value; - ascertaining at least one ratio value (V) that is characteristic of a relationship between the effective area value (W) and the measuring area (M).

Description

[0001] Device and method for investigating surface properties

[0002] Description

[0003] The present invention relates to a device and a method for examining optical surface properties. The invention is described with reference to the examination of motor vehicle surfaces, but it should be noted that the device can also be used for other surfaces, for example, furniture or electronic components or (small) buttons on electronic devices.

[0004] Various methods and devices for examining such surface properties are known from the prior art. One of the properties to be examined is so-called gloss, which is determined by irradiating the surface to be examined and measuring or examining the reflected radiation.

[0005] Classic gloss measurement has strict specifications regarding the optical configuration. The measured values ​​for classic gloss measurement are only defined for flat, polished black glass (GU100 - n=1,567, from ISO2813). If these specifications are not adhered to exactly, no measured values ​​that correlate linearly with the standard will be recorded for different surface types. This means that the standard-compliant measurement must remain the same on uneven samples as on flat samples. If the photocell from the standard configuration is replaced by a camera, the image of the illumination aperture is obtained. The surface of the sample is not sharply imaged, and the surface shape and texture are only measured indirectly. Therefore, no detailed information about the surface is available if the photocell is replaced by a camera. However, unlike a photocell, the camera can compensate for any tilt of the measuring device relative to the surface normal.The aperture image can be tracked and the aperture can be virtually recreated by the camera pixels.

[0006] These camera images can also be used to create an indicator for the correct positioning of the measuring device. The aperture image on the area detector must be within a defined range for a correct measurement. The applicant reserves the right to claim protection for such a design.

[0007] An area sensor positioned at the position of the conventional detector allows for tracking of the reflected signal. For tracking, for example, the brightness center of gravity in the recorded intensity image can be used.

[0008] If the measuring device is tilted, the bright illumination aperture image moves away from the defined position. The sample surface being measured can also actively tilt, for example, with moving web materials in a robotics application. If the center of gravity leaves a defined tolerance range, the measurement is classified as invalid, and feedback is provided about the excessive tilt.

[0009] The area sensor can also be used to measure gloss. For this purpose, a virtual aperture can be defined that is the size of the mechanical aperture. The accumulated brightness value of the virtual aperture corresponds to the conventional measured value. The virtual aperture can also be positioned around the center of gravity and coupled to it. This also compensates for the tilt of the measuring device to a certain extent. HDR images are preferred for absolute measurement recording.

[0010] The area sensor can also be used in combination with the conventional sensor. For this purpose, a portion of the detector signal can be extracted (particularly via a beam splitter) and fed to the area sensor. The area sensor detects the tilt. The conventional sensor with a mechanical aperture preferably performs simultaneous signal measurement.

[0011] The present invention is based on the object of enabling a gloss measurement, particularly traceable to conventional gloss measurement, even for curved surfaces. A further object underlying the invention is to enable the determination of surface properties (in particular, gloss values) of very small surfaces. A further object underlying the invention is to enable the determination of surfaces that have both glossy and matte areas.

[0012] For curved surfaces, the invention proposes combining the characterization of the surface geometry with conventional gloss measurement. However, this approach can also be applied to small surfaces and surfaces with matte and glossy areas.

[0013] Various observation methods are known from the state of the art. One such method is the so-called spot observation.

[0014] Typically, spot observation is used to detect dirt or damage on a surface. A common method of incident illumination is called dark-field microscopy. Only the light diffusely reflected from the surface reaches the observation unit. This method is not applicable to uneven and / or reflective surfaces. On reflective surfaces, for example, one would see dust particles where the light is diffusely reflected.

[0015] Dark-field illumination is suitable for matte surfaces, although even here, curvatures are not visible with circular illumination. However, all-round illumination is necessary for rotational freedom, meaning that the measured values ​​should be independent of the measuring device's position. Scratches are detectable in dark-field illumination, although deep scratches will be shadowed.

[0016] High-gloss or reflective sample surfaces can only be imaged using inline illumination and (as described within the scope of the invention) in combination with a telecentric lens. The applicant was able to determine that the telecentric lens prevents the imaging of reflections from the light source on the surface. This effect is due to the limited angular acceptance and depth of field in the telecentric case. Furthermore, a large lens of a telecentric lens can capture all the light, for example, in the case of parallel incident and reflected light. When using a conventional lens, reflected light at the edges of the measurement area cannot be detected.

[0017] In microscopy, this inline illumination is called brightfield illumination. To avoid reflections from the light source (during critical illumination), so-called Köhler illumination can be used. In contrast to critical illumination, this achieves uniform illumination of the specimen.

[0018] However, this Köhler illumination is comparatively complex, so the invention also aims to provide a simpler arrangement. As described in more detail below, a lens with an aperture is used for this purpose.

[0019] In industrial image processing, homogeneous, flat illumination is used to circumvent the problem of reflection in a cost-effective and user-friendly manner. The light source consists of a homogeneously illuminated surface the size of the observation area. This illumination can be realized, for example, with an LED matrix and a diffuser. Within the scope of the invention, it is proposed that the coupling be carried out, for example, via a beam splitter (diffuse coaxial illumination).

[0020] Another object underlying the invention is to use a cost-effective and easy-to-use lighting.

[0021] The advantageous new measurement setup produces sharper and more detailed images of the surface. Curvatures can be interpreted using the brightness gradient in the images. The new setup is preferably rotation-free. Even deep damage in the surfaces can be seen without shadowing.

[0022] In image processing, the combination of telecentric lenses with telecentric illumination is typically used in transmitted light rather than reflected light. The simple inline design in reflected light, however, is not known from the prior art for the devices under consideration here and represents a significant aspect of the invention.

[0023] A further object underlying the invention is to provide a device and a method which also allow a standardized evaluation of non-planar surfaces, or of surfaces which are not uniformly shiny or not uniformly diffusely scattering, i.e. matt.

[0024] A further object underlying the invention is to provide a device and a method that also enables the assessment of surfaces of very small components, such as electronic components. In addition, the assessment of small control units, such as small buttons (e.g., on a smartphone), should also be possible.

[0025] The above-mentioned objects are achieved by devices and methods according to the independent patent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

[0026] A device according to the invention for examining optical properties of surfaces has a first radiation device which is suitable and intended to radiate radiation in a first irradiation direction onto the surface to be examined, and a first radiation detector device which is suitable and intended to detect the radiation radiated by the first radiation device onto the surface to be examined and reflected by the surface in a (first) radiation direction.The device further comprises an optical detection device with an irradiation device which is suitable and intended to irradiate radiation in a second irradiation direction onto the surface to be examined and with a radiation detection device which is suitable and intended to detect the radiation irradiated by the irradiation device onto the surface to be examined and emitted by the surface in a second radiation direction.

[0027] According to the invention, the second direction of incidence and the second direction of emission are essentially diametrically opposed. "Diametrically opposed" means that the radiation directions are essentially parallel to each other, but opposite to each other. "Essentially parallel" means that the beam directions extend at an angle to each other that lies between 170° and 190°, preferably between 175° and 185°, between 178° and 182°, and particularly preferably between 179° and 181°.

[0028] A further device according to the invention for examining optical surface properties of surfaces comprises an irradiation device which is suitable and intended to irradiate radiation in a predetermined irradiation direction (in particular in the irradiation direction referred to above as the second irradiation direction) onto the surface to be examined, as well as a radiation detection device which is suitable and intended to record a spatially resolved image of the radiation emitted and in particular reflected by the surface in response to the radiation irradiated (by the irradiation device), wherein the radiation detection device has a maximum detection area for detecting the radiation impinging on it. Preferably, the radiation detection device is suitable for recording HDR images and determines and records HDR images.

[0029] Furthermore, the device comprises an image evaluation device (in particular a processor-based one) which is suitable and intended to determine at least one effective area value which is characteristic of an area lying in a predetermined and / or predeterminable measuring area within the maximum detection area, which area is reached by the radiation emitted, in particular reflected, by the surface in response to the radiation radiated in (by the irradiation device) in a predetermined and / or predeterminable manner, in particular with regard to a brightness and / or color value. Preferably, exactly one effective area value is determined. However, it is also conceivable that two, three or more effective area values ​​are determined.

[0030] In addition, a processor device is provided, which is suitable and intended to determine at least one ratio value that is characteristic of a relationship between the area value and the measurement area. The processor device can be the image evaluation device. However, it is also conceivable that the processor device is (at least partially) different from the image evaluation device. Preferably, exactly one ratio value is determined. However, it is also conceivable that two, three, or more ratio values ​​are determined.

[0031] The device can have all the features of the device first described above, individually or in combination, and vice versa. Furthermore, both devices can have all the features mentioned below, individually or in combination with one another.

[0032] Due to the curvature or the small size of the surface, not all radiation incident on the surface or all radiation emanating from the irradiation device is reflected to the radiation detection device.

[0033] This circumstance is taken into account by the aforementioned relationship value or ratio between the area value and the measuring area. This relationship value is also referred to below as the fill factor. Using this value, one can, for example, draw conclusions from the optical properties of a curved surface to the optical properties of a corresponding, flat surface.

[0034] This fill factor is therefore a factor that can depend on the curvature or the size of the object or the shiny or matte parts of the surface.

[0035] Preferably, the fill factor is a value that is calculated as follows:

[0036] Fill factor = area value / measuring area (or partial area / total area of ​​the measuring device), whereby preferably both the area value and the measuring area are each in the unit mm 2 It is also conceivable that the area value and the measuring area each have a value in the same (but especially any, for example, mm 2 different) (area) unit of measurement.

[0037] In a further advantageous embodiment, the device is portable. This makes it possible for the device to be guided by a user by hand, but it is also possible for the device to be guided by a robot or robot arm. Preferably, the surface to be examined is a curved surface or a very small surface. A very small surface is understood to be a surface smaller than 4 cm. 2 preferably smaller than 3cm 2preferably smaller than 2cm 2 , preferably smaller than 1cm 2 , preferably less than 0.5 cm 2 , preferably less than 0.3 cm 2 , preferably smaller than preferably smaller than 5 mm 2 In particular, the maximum (geometric) extent of the surface to be examined in at least one direction and preferably in at least two mutually perpendicular directions is less than 4 cm 2 preferably smaller than 3cm 2 preferably smaller than 2cm 2 , preferably smaller than 1cm 2 .

[0038] For example, this very small surface can be the surface of an electronic component or the surface of a button or key on a device such as a smartphone.

[0039] In principle, the devices described here or the measurements carried out by these devices are sensitive to tilting and changes in distance (of the device relative to the surface to be examined) with small measuring spot areas (less than 1 mm 2 ).

[0040] For a repeatable measurement, a minimum spot size is required for traditional gloss measurement. With very small spot sizes, positioning the measuring device on the object is very difficult, and the measured value is highly dependent on correct positioning.

[0041] These surfaces pose difficulties in the prior art because, due to the curvature or the small size of the surface to be examined, for example in the context of a classic gloss measurement, not all radiation emanating from the radiation device reaches the radiation detector device via the surface.

[0042] Conventional gloss measurements require flat surfaces. Calibration is always performed only on flat surfaces. On curved surfaces, a certain portion of the incident radiation is not reflected toward the radiation detector, which must be taken into account when evaluating measurement results, especially those generated during conventional gloss measurements. On very small surfaces, not all of the incident radiation reaches the surface under investigation. Here, too, a correction is necessary.

[0043] Within the scope of the invention, it is therefore proposed to combine a classic observation and / or illumination with an inline illumination and, in particular, telecentric, inline observation.

[0044] In a preferred embodiment, the second irradiation direction, i.e., the direction in which the radiation originating from the irradiation device strikes the surface, is substantially perpendicular to the surface to be examined. This makes it possible for this (second) irradiation direction to be opposite to the direction of the radiation emitted, in particular reflected, by the surface. The radiation emitted by the surface is preferably reflected radiation (i.e., radiation that was first irradiated onto the surface by the second radiation device and reflected by it).

[0045] In other words, the second irradiation direction, i.e., the irradiation direction in which the radiation originating from the irradiation device strikes a measuring plane in which the surface to be examined is arranged (and / or is to be arranged), is substantially perpendicular to the measuring plane. As described above, this irradiation device can be diametrically opposed to the direction of the radiation emitted, in particular reflected, by a surface arranged (flatly configured) in the measuring plane.

[0046] Preferably, the surface to be examined is located in one of the measuring planes and / or is to be positioned for examination. For completely flat surfaces to be examined, this surface lies within the measuring plane.

[0047] In a further preferred embodiment, the first irradiation direction forms an angle with the surface to be examined (and / or with the measurement plane) that is greater than 15°, preferably greater than 30°, preferably greater than 35°, preferably greater than 40°, and particularly preferably greater than 50°. In a further preferred embodiment, the first irradiation direction forms an angle with the surface to be examined (and / or with the measurement plane) that is less than 80°, preferably less than 70°, preferably less than 65°. The angle is particularly preferably 60°.

[0048] Particularly preferably, the first radiation device radiates the radiation onto the surface (and / or the measurement plane) at an angle of substantially 45° or 60° relative to the surface, and the first radiation detector device records the radiation reflected from the surface, also at an angle of substantially 45° or 60°. Preferably, the angle of incidence and the angle at which the radiation is recorded are opposite.

[0049] Preferably, the device comprises a second radiation device, which is suitable and intended for radiating radiation onto the surface to be examined in a second (glancing angle) direction of incidence, and a second radiation detector device, which is suitable and intended for detecting the radiation radiated by the second radiation device onto the surface to be examined and reflected by the surface in a second (glancing angle) direction of emission. Preferably, the second (glancing angle) direction of incidence and the second (glancing angle) direction of emission form an opposite angle with the measuring plane or with a (flat) surface to be examined.

[0050] Preferably, the device comprises a third radiation device, which is suitable and intended for radiating radiation onto the surface to be examined in a third (glancing angle) direction of incidence, and a third radiation detector device, which is suitable and intended for detecting the radiation radiated by the third radiation device onto the surface to be examined and reflected by the surface in a third (glancing angle) direction of incidence. Preferably, the third (glancing angle) direction of incidence and the third (glancing angle) direction of incidence form an opposite angle with the measuring plane or with a (flat) surface to be examined.

[0051] Preferably, the second radiation device and the second radiation detector device and / or the third radiation device and the third radiation detector device (apart from the direction of irradiation and the direction of emission) are designed in an analogous or identical manner to the first radiation device and the first radiation detector device.

[0052] Preferably, the angles that the first and / or second and / or third radiation device (or the first and / or second and / or third radiation detector device) encloses with the measuring plane or with a (flat) surface to be examined are selected from a group that includes the ranges 15° - 25°, 40° - 50°, 55° - 65°, 70° - 80° and 80° - 90°, preferably selected from a group that includes angles of substantially 20°, 45°, 60°, 75°, 85°.

[0053] In a further preferred embodiment, the device comprises a housing within which the first radiation device, the first radiation detector device, the irradiation device and the radiation detection device are arranged.

[0054] In a particularly preferred embodiment, this housing has an opening through which the surface can be irradiated by the first radiation device and by the irradiation device. This opening is particularly preferably the only opening in the housing through which light can exit the housing and through which light can enter the housing. This opening preferably also defines the measurement plane.

[0055] In a preferred embodiment, the device comprises spacer elements that space the housing, in particular the opening of the housing, from the surface to be examined during the measurement. For example, pins or feet can be arranged on the underside of the housing or the side facing the surface to be examined during the measurement, which keep the opening at a defined distance from the surface. These pins offer advantages, particularly when examining curved surfaces.

[0056] These pins preferably have a height or length greater than 0.2 mm, preferably greater than 0.3 mm, preferably greater than 0.5 mm, preferably greater than 0.7 mm, and particularly preferably greater than 1.0 mm. These pins preferably have a height or length less than 10 mm, preferably less than 8 mm, preferably less than 6 mm, and particularly preferably less than 5 mm, and preferably less than 4 mm.

[0057] Particularly preferably, at least three such pins or feet are provided.

[0058] Particularly preferably, a light-shielding element is provided between the spacer elements and the opening. This light-shielding element is preferably a flexible element that (completely) surrounds the opening, such as a rubber seal.

[0059] Preferably, two adjacent spacer elements are spaced apart by a distance greater than 1 cm, preferably greater than 2 cm. Preferably, two adjacent spacer elements are spaced apart by a distance less than 10 cm, preferably less than 8 cm, preferably less than 7 cm.

[0060] Preferably, a cavity is formed within the housing, into which both the radiation device and the irradiation device radiate. This cavity is preferably completely bounded (with the exception of the opening) by radiation-absorbing walls.

[0061] In a further advantageous embodiment, the device comprises a housing and this housing has an opening and the irradiation device is suitable and intended to irradiate the surface through this opening and the radiation detection device is suitable to detect radiation from the surface in response to the radiation emitted by the irradiation device and passing through the opening.

[0062] In a further advantageous embodiment, the device has a radiation deflection device (also referred to as a beam splitter, preferably 50:50) which is suitable and intended to deflect the radiation emanating from the irradiation device in such a way that this radiation strikes the surface in the second irradiation direction.

[0063] The radiation deflection device preferably deflects the radiation emanating from the irradiation device at an angle between 30° and 150°. This angle is preferably greater than 30°, preferably greater than 40°, preferably greater than 50°, preferably greater than 60°, preferably greater than 70°, preferably greater than 80°, and preferably greater than 85°.

[0064] This angle is preferably less than 150°, preferably less than 140°, preferably less than 130°, preferably less than 120°, preferably less than 110°, preferably less than 100° and preferably less than 95°.

[0065] In a further preferred embodiment, the radiation deflection device is designed as a mirror, in particular a partially transmissive mirror. The ratio between transmitted and reflected radiation is preferably between 30:70 and 70:30, preferably between 35:65 and 65:35, preferably between 40:60 and 60:40, preferably between 45:55 and 55:45, and particularly preferably approximately 50:50.

[0066] Preferably, this radiation deflection device or this mirror has different reflectivity depending on the side from which the radiation impinges on it. Preferably, a portion of the radiation coming from the irradiation device is reflected onto the surface, and a portion of the radiation reflected by the surface is transmitted and reaches the (second) radiation detection device.

[0067] By using this radiation deflection device, it is possible to irradiate the surface in a given direction (for example, vertically) and also to detect radiation (in particular spatially resolved) in this direction, or more precisely the opposite direction.

[0068] In a further preferred embodiment, the device comprises a lens (or lens arrangement), in particular a telecentric lens. This telecentric lens is preferably arranged between the surface to be examined and the (radiation) detection device (which is in particular an image detection device).

[0069] In a further advantageous embodiment, the (second) radiation detection device is suitable and intended to output a spatially resolved image of the radiation impinging on it and / or the surface to be examined. Particularly preferably, a telecentric lens is provided to image the surface (to be examined) on the radiation detection device and in particular on an image recording device. As mentioned above, the use of a telecentric lens on the observation side, and in particular within the framework of inline observation, is not known from the prior art relevant to the present invention. However, the applicant has recognized that inline observation is particularly efficient, especially with a telecentric lens.

[0070] The present invention is further directed to an optical detection device for optically detecting surfaces, comprising an irradiation device which is suitable and intended to irradiate radiation in a (second) irradiation direction onto the surface to be examined, and comprising a radiation detection device which is suitable and intended to detect the radiation irradiated by the irradiation device onto the surface to be examined and reflected by the surface in a second irradiation direction.

[0071] According to the invention, the (second) direction of incidence and the second direction of emission are essentially opposite. In this embodiment, a very specific form of illumination and detection of the surface is used, which is unknown in the prior art.

[0072] In general, the radiation is preferably light, especially light in the visible wavelength range. The radiation is particularly preferably white light, especially standardized white light.

[0073] In a preferred embodiment, the irradiation device and / or the radiation device comprises at least one or a plurality of LEDs, and in particular white light LEDs. Preferably, only one light source, in particular in the form of an LED, is provided, and preferably an aperture associated with this light source. This aperture can preferably be located at the focal length of a lens. In this case, this one light source can be regarded as a point light source. In a further preferred embodiment, the irradiation device comprises a light source, an aperture or aperture, and preferably a lens. These elements are preferably arranged in the direction of irradiation upstream of a beam splitter, and in particular the aforementioned beam splitter (or the (beam) deflection device).

[0074] Particularly preferably, a lens, in particular a telecentric lens, is arranged between the surface (and / or the measuring plane in which, in particular, the surface to be examined is arranged and / or is to be arranged for its examination) and the detection device. This (telecentric) lens is preferably arranged closer to the detection device than to the surface to be examined. This lens preferably has at least two and preferably at least three lenses.

[0075] The optical detection device is preferably designed in the manner described above.

[0076] The present invention is further directed to a method for examining optical surface properties (of a surface to be examined), which comprises at least the following steps:

[0077] - irradiation of radiation onto the surface to be examined by means of an irradiation device;

[0078] - Recording a spatially resolved image of the radiation emitted and in particular reflected by the surface in response to the radiation radiated in (by the irradiation device) by means of a radiation detection device which has a maximum detection area for the (in particular spatially resolved) detection of the radiation reaching it;

[0079] Preferably, the radiation detection device is a device suitable and intended for the spatially resolved detection of the radiation impinging upon it. In particular, the radiation detection device is a camera.

[0080] - Determining at least one effective area value that is characteristic of an area located in a predetermined and / or predeterminable measuring area within the maximum detection area, which is reached by the emitted, in particular reflected, radiation in a predetermined and / or predeterminable manner, in particular with regard to a brightness and / or color value. Preferably, exactly one effective area value is determined. However, it is also conceivable that two, three, or more effective area values ​​are determined;

[0081] - Determining at least one ratio value (V) that is characteristic of a relationship between the area value (W) and a predetermined maximum value (M). Preferably, exactly one ratio value is determined. However, it is also conceivable that two, three, or more ratio values ​​are determined.

[0082] As mentioned above, due to the curvature or insufficient size of the surface, not all radiation incident on the surface is reflected to the radiation detection device or not all radiation emanating from the irradiation device hits the surface to be examined.

[0083] As mentioned above, the ratio value mentioned above is the fill factor, which can depend on the curvature of the surface, the size of the object, or the glossy or matte parts of the surface.

[0084] The maximum detection area is in particular the measuring area which is characteristic for the respective detection device, for example a CCD chip or a camera.

[0085] The predetermined and / or predeterminable measuring area is that partial area of ​​the maximum measuring area which would or will result in particular from oblique irradiation (from a radiation device, which can in particular be the first radiation device, onto the surface). If, for example, a radiation device has a rectangular aperture, this rectangular aperture would be imaged on the surface in the event of irradiation in a perpendicular direction. This oval light spot would be detected by the radiation detection device. In other words, in this case the radiation detection device detects an oval, irradiated partial area of ​​the surface to be examined, which is incident on the measuring area of ​​the radiation detection device (in particular due to the optical arrangement of the radiation detection device such that the beam path diverges from perpendicular to the surface to be examined orradiation emitted from the measuring plane is parallel and / or along the detection direction and / or the optical axis of the radiation detection device) is also imaged as an oval surface.

[0086] The aperture preferably has a rectangular cross-section. The ratio of the length of this aperture to the width of this aperture is preferably between 5:1 and 2:1. Despite the rectangular aperture, the measurement spot will appear oval at the relevant observation distances.

[0087] The radiation detection device cannot observe or detect the measuring spot generated by the first radiation device on the surface to be examined (at least in the case of reflective surfaces).

[0088] Preferably, the measurements carried out by the irradiation device and the radiation detection device on the one hand and the measurements carried out by the first radiation device and the first radiation detector device on the other hand are carried out sequentially in time.

[0089] If this radiation device (in particular, the radiation device is the first radiation device) radiates obliquely onto the surface, an elliptical image would result on the surface. This elliptical image is then detected by the radiation detection device. This elliptical image is accordingly the predeterminable and / or predetermined measurement area, which depends in particular on parameters such as the angle of incidence and the aperture of the radiation device. However, these parameters are preferably fixed and / or device-specific parameters.

[0090] In other words, when the (first) radiation device irradiates the surface at an angle, an elliptically irradiated partial area of ​​the surface is created. If only this (irradiated) partial area is considered, this (irradiated) partial area of ​​the surface, with radiation now exclusively irradiated by the irradiation device (with the above optical arrangement of the irradiation device and / or the radiation detection device), corresponds to an elliptical area on the detection surface of the radiation detection device.

[0091] Preferably, the predetermined and / or predeterminable measuring area depends on at least one parameter that is dependent on the irradiation of the radiation by the irradiation device, which parameter is selected in particular from a group of parameters that includes an angle of incidence, the shape of an aperture of the irradiation device, the light source of the irradiation device, and the like. These are thus preferably specific and / or fixed parameters for the device used.

[0092] The effective area value is also influenced by factors such as the curvature or size of the surface being examined. A curvature of this surface can, for example, mean that not all of the radiation reflected from the surface reaches the measuring surface. For example, if a flat surface were to illuminate a fully illuminated ellipse on the radiation detection device, this ellipse would not be fully filled in the case of a curved surface. The same would apply if the surface being examined was so small that not all of the radiation passing through the aperture of the radiation device reaches the surface. The radiation would then not only hit the object but also its surroundings.

[0093] In the case of a flat sample, the illumination and observation spot would be at most an ellipse. In the case of a curved (non-flat) surface, the effective shape of the spot depends on the surface topography.

[0094] This effective area value can be determined, in particular, using a threshold method, as described in more detail below. For example, it can be determined at which intensity value of the radiation incident on the pixels these pixels are considered illuminated or unilluminated. In this way, a binary distinction can be made, preferably between illuminated and unilluminated surface areas, or which surface elements contribute to the measured value.

[0095] In a further method according to the invention for examining optical properties of surfaces, a first radiation device radiates radiation in a first irradiation direction onto the surface to be examined, and a first radiation detector device detects the radiation radiated by the first radiation device onto the surface to be examined and emitted and in particular reflected by the surface in the radiation direction (R1').

[0096] Furthermore, an irradiation device radiates radiation onto the surface to be examined in a second direction, and a radiation detection device detects the radiation radiated onto the surface to be examined by the irradiation device and emitted (and in particular reflected) by the surface in a second direction. These measurements can be performed both simultaneously (for reflective surfaces) and staggered in time (for non-reflective surfaces).

[0097] According to the invention, the second radiation direction and the second radiation direction are substantially opposite.

[0098] In a further method according to the invention for the optical detection of surfaces, an irradiation device radiates radiation in one irradiation direction onto the surface to be examined and a radiation detection device detects the radiation irradiated by the irradiation device onto the surface to be examined and reflected by the surface in a second radiation direction and preferably records a spatially resolved image of the surface.

[0099] According to the invention, the second radiation direction and the second radiation direction are substantially opposite.

[0100] In an advantageous method, a telecentric optic and in particular a telecentric lens is used to detect the radiation, which is preferably arranged between the surface and the radiation detection device.

[0101] In a further advantageous method, the radiation detection device records a spatially resolved image of the surface to be examined. For this purpose, a camera or a CCD chip, for example, is used, onto which the surface is preferably imaged. The surface to be examined is preferably imaged onto the radiation detection device using telecentric optics. In a further advantageous method, the surface to be examined is a curved surface or a surface of a small component, or a surface that has both shiny and matte (or matte-reflecting and / or scattering) areas.

[0102] If the surface is the surface of a small component, this small component is preferably mounted on a carrier which is smaller than the component itself in the observation plane or measurement plane. In this way, radiation reflected from this carrier (which would falsify the measurement result) can be prevented from reaching the radiation detection device (and / or radiation detector device).

[0103] The environment of the carrier is preferably selected in such a way that unwanted reflections do not reach the detector or the radiation detection device, e.g. a heavily matted surface or via a light trap.

[0104] In a further preferred method, the predetermined and / or predeterminable measuring surface is predetermined by a first radiation device (which is in particular the radiation device referred to above as the first radiation device), which is suitable and intended to radiate radiation onto the surface to be examined under a predetermined (first) irradiation direction, in particular deviating from a vertical direction.

[0105] In this method, as mentioned above, the predetermined and / or predeterminable measuring surface is determined as a result of a particularly oblique irradiation of the radiation onto the surface and in particular a recording of the radiation reflected from the surface.

[0106] Preferably, the predetermined and / or predeterminable measuring area is a maximum area illuminable by the first radiation device and / or a surface area of ​​a surface to be examined (in particular a flat or smooth surface). Preferably, the radiation reaching the surface and / or a radiation cross-section of this first radiation device is limited by a radiation limiting element, in particular a diaphragm.

[0107] In particular, this radiation is radiated onto the surface at a predetermined angle, for example an angle of 45° or 60° (20°, 75° or 85° would also be conceivable), relative to a perpendicular direction.

[0108] The camera or radiation detection device only has a virtual knowledge of the gloss measurement spot (it cannot measure the gloss measurement spot). The specified and / or specifiable measurement area is retrieved from a memory device in the device to determine the ratio value or fill factor.

[0109] In a further preferred method, the first radiation device, in conjunction with a radiation detector device, is suitable and intended for performing a gloss measurement. The radiation detector device can be a radiation detector device that captures a spatially resolved image of the radiation impinging on it. However, a radiation detector device that outputs a value characteristic of an (integral) intensity of the radiation impinging on it could also be used.

[0110] In a preferred method, the predetermined and / or predeterminable measuring area is characteristic of a size of that area of ​​a component of the radiation detection device which is reached by the radiation emitted (by the (first) radiation device) when using a flat surface.

[0111] In a further preferred method, the predetermined and / or predeterminable measuring area is characteristic of a size of the area of ​​a component of the radiation detection device which results when the radiation emanating from the (first) radiation device is completely reflected to a (first) radiation detector device. When considering the predetermined and / or predeterminable measuring area, it is therefore assumed in particular that all radiation emanating from the irradiation device (and in particular passing through an opening in a housing of the device) reaches the surface and that all radiation reflected from the surface also reaches the radiation detection device. In this case, the surface to be examined is therefore preferably completely imaged onto the radiation detection device.

[0112] In a further preferred method, the measuring area is characteristic of a size (and / or arrangement) of that area within the maximum detection area which is reached by radiation emitted by a first radiation device when using a flat surface as the surface to be examined.

[0113] In a further preferred method, the measuring area is characteristic of a size of the area which results when the radiation emanating from a first radiation device is completely reflected to a radiation detector device.

[0114] In another preferred method, the radiation is directed onto the surface to be examined through an opening in a housing, and the radiation emitted by the surface to be examined passes through this opening. Preferably, the radiation emitted by the irradiation device but not passing through said opening is disregarded.

[0115] Particularly preferably, said opening is placed directly or at a very close distance from the surface to be examined. A very close distance is understood to be a distance that is less than one-third of the distance between the first radiation device and the opening, preferably less than one-fifth, preferably less than one-seventh, and preferably less than one-tenth.

[0116] Preferably, radiation emanating from the irradiation device that does not pass through the opening is absorbed by a wall of the housing, particularly an inner wall. In another preferred method, the maximum value is characteristic of the entire area of ​​the opening imaged onto the radiation detector.

[0117] With an "ideal" surface, the opening is completely imaged onto the radiation detection device. This is the maximum illuminable area and thus the maximum value. It is therefore assumed that all radiation passing through the opening is precisely reflected by the surface and thus reaches the radiation detection device, resulting in an ideal image of the surface on the detection device.

[0118] Preferably, the maximum value is the area of ​​the opening.

[0119] In another preferred method, a threshold method is used to determine the area value and / or the ratio value. This means that threshold values ​​or limit values ​​are used as a basis, which are decisive for the question of whether certain irradiated or illuminated pixels or pixel regions of an image recording device are considered irradiated or non-irradiated. In this way, it can be determined for each irradiated pixel of the radiation detection device whether or not it is still assigned to the illuminated region.

[0120] In a further preferred method, the threshold method determines a brightness distribution (and / or color distribution) in the image recorded by the radiation detection device and / or evaluates this brightness distribution (and / or color distribution).

[0121] It is therefore preferentially decided which pixels are still counted as values ​​that determine the area value and which are not.

[0122] Preferably, a threshold value is determined. Intensity values ​​above this value are considered to belong to the area, while those below this value are not.

[0123] The fill factor mentioned above can be determined in several ways. The simplest algorithm is the thresholding method described above for the cross-section of the brightness distribution in the image. In another preferred method, thresholds for the thresholding method are determined using standard surfaces.

[0124] For this purpose, glass standards with different curvature radii and gloss values ​​are preferably selected. The linear relationship between fill factors 0 and 1 is preferably used as a guideline.

[0125] In another preferred method, the fill factor is mathematically linked to the gloss value(s). Preferably, the fill factor is mathematically related to (particularly measured) gloss values, for example, divided (or multiplied) by them, particularly to perform evaluations for curved or small surfaces.

[0126] In these evaluations, the respective gloss angle can also be taken into account, in particular the size of the angle at which the gloss is recorded.

[0127] In another preferred method, the surface to be examined is curved. In another preferred method, the surface to be examined is smaller than an area that can be illuminated by the irradiation device through the opening and / or a measurement area defined and / or illuminated by the first radiation device.

[0128] In a further preferred method, the surface to be examined has both glossy and matte surface areas.

[0129] In a further advantageous method, a gloss value for an ideal surface is determined using the ratio value resulting for such a surface, wherein this ideal surface corresponds to the measured surface in terms of its optical properties, but the ideal surface is flat and is at least as large as an area that can be illuminated by the irradiation device through the opening.

[0130] In this way, it is preferably possible to convert data determined for an actual surface into data that would result from a flat surface. In particular, this method can be used to determine, for example, a gloss value for a curved surface under investigation that would result from a (conventional) gloss measurement for this surface with a flat or planar surface shape instead of the curved one (and thus otherwise identical optical properties).

[0131] In a further preferred method, the irradiation device radiates the radiation substantially perpendicularly onto the surface, and the radiation detection device detects radiation that is emitted and, in particular, reflected from the surface substantially perpendicularly to the surface. "Perpendicular" assumes an ideal, flat surface. Preferably, the radiation is also emitted perpendicularly to an opening cross-section of the opening of the above-described housing.

[0132] In a further preferred method, a telecentric lens is used to image the surface onto the radiation detection device.

[0133] Further advantages and embodiments can be seen from the attached drawings:

[0134] Showing:

[0135] Fig. 1a shows a state-of-the-art setup for gloss measurements, taken from EN ISO 2813;

[0136] Fig. 1b shows a photograph taken with the device according to Fig. 1a, the surface being reflective;

[0137] Fig. 2a, 2b show a structure known in the prior art and a structure according to the invention according to a preferred embodiment for investigating surface properties;

[0138] Fig. 3a-d, four representations of measurement results obtained with the setups according to Fig. 2a, b;

[0139] Fig. 4 shows a representation of a device according to the invention for its first application; Fig. 5 shows a representation of a device according to the invention for a second application;

[0140] Fig. 6 shows a representation of how to carry out an inline measurement;

[0141] Fig. 7 shows a first representation to illustrate a determination of a fill factor;

[0142] Fig. 8a, 8b representations for measuring curved surfaces;

[0143] Fig. 9 shows an overall representation for determining properties of glossy surfaces;

[0144] Fig. 10 is a diagram illustrating measurement results for matte surfaces;

[0145] Fig. 11 is a further diagram illustrating a further method step of the present invention;

[0146] Fig. 12 shows a representation for determining gloss values ​​from the fill factor;

[0147] Fig. 13 is a representation of a telecentric optic;

[0148] Fig. 14 is a sectional view of the telecentric optics shown in Fig. 13;

[0149] Fig. 15 is another view of the telecentric optics to illustrate dimensions; and

[0150] Fig. 16a, b two representations to illustrate the application of the method to surfaces with different gloss areas.

[0151] Fig. 1a schematically shows a setup for examining gloss properties of surfaces and / or coatings 10. A light source 120 is provided which radiates light onto the surface 10 at an angle of incidence a1 (viewed relative to a center plane M).

[0152] A lens 122 is also provided, which aligns the light or radiation in parallel. Surface 10 reflects the light, and the light passes through a second lens 124 at angle a2 and through an aperture 126 to a radiation detector device, on which an image 130 is projected. Here, a2 denotes the angle at which the radiation is reflected from the surface, or rather, the angle between the center plane M and the beam path of the radiation emitted and, in particular, reflected by surface 10.

[0153] Fig. 1b shows a correspondingly recorded image over a reflective surface.

[0154] This image shows the signal from a sensor in a classic setup, as shown in Fig. 1. However, this type of recording is not suitable for curved surfaces or surfaces with varying levels of gloss and matte, nor for very small surfaces.

[0155] Figs. 2a and 2b show two basic approaches for observing surfaces. Fig. 2a shows a conventional dark-field illumination, and Fig. 2b shows an inline illumination now proposed within the scope of the invention. In the dark-field illumination shown in Fig. 2a, two radiation devices 142 and 144 illuminate the surface at a predetermined angle, here 45°, and an image recording device 146 captures the light scattered by the surface (but preferably not the reflected light).

[0156] In the illustration shown in Figure 2b, a light source 144 illuminates the surface via a beam splitter device 148 and the light reflected from there reaches the image capture device 146.

[0157] Figures 3a to 3d show four images of recorded surfaces. The images in Figures 3a and 3c were acquired using the dark-field method, while images 3b and 3d were acquired using the aforementioned inline illumination.

[0158] Figures 3a and 3b show a black glass surface with a scratch (the gloss value measured at a 60° angle is 95 GU (gloss unit). Figures 3c and 3d show a textured surface. The gloss value at a 60° angle is 69.3 GU.

[0159] Fig. 4 shows a first embodiment of a device according to the invention for examining surface properties. Reference numeral 2 refers to a first radiation device, which radiates radiation, and in particular light, onto a surface 10 to be examined in an irradiation direction R1. It can be seen that this surface is curved, so that the radiation emitted in the direction R1' is expanded or divergent. Thus, not all of the radiation reflected from the surface 10 reaches the first radiation detector device 4.

[0160] Reference numeral 20 refers in its entirety to an optical detection device for the surface. As explained in more detail below, this device radiates radiation in the direction R2, i.e., in a perpendicular direction, onto the surface 10, and also detects radiation from the surface 10 in a direction R2' opposite to this direction.

[0161] Fig. 5 shows a device comparable to the device in Fig. 4, but with a different application. Here, the surface to be examined is a small workpiece, such as a microchip mounted on a holder 11, or a button of an electronic device. This holder 11 is significantly smaller in cross-section than the surface 10 itself. This prevents radiation reflected by the holder 11 from reaching the radiation detector device 4. Here, too, an optical detection device, designated overall by 20, is provided.

[0162] In this application, which is also preferred according to the present invention, the area or geometric extent (in at least one direction) of the surface 10 of the small workpiece to be examined is smaller than the area or geometric extent of a measuring surface (specified by the device). The measuring area results in particular from the area within a measuring plane that can be irradiated or illuminated by the first radiation device 2. In the application shown here in Fig. 5, due to the small (geometric) extent of the surface 10 to be examined compared to the measuring surface, not all of the radiation emitted by the first radiation device 2 or emitted in the direction of the measuring surface (or not all of the radiation radiated onto the measuring surface or the measuring plane in the irradiation direction R1) reaches the surface 10 to be examined.

[0163] As the uppermost and the lowermost beam path emanating from the first radiation device illustrate, due to the small extent of the surface 10 to be examined, part of the radiation emitted in the direction of the measuring surface is not reflected in the direction of the first radiation detector device due to reflection at the surface to be examined.

[0164] Compared to a surface to be examined that fills the measuring area, for example, a (classical) (gloss) measurement for this smaller surface to be examined 10 without correction of the surface size (erroneously) results in a lower (gloss) value, because only the portion of the radiation incident on the measuring surface corresponding to the smaller surface contributes to the (gloss) value measured by the radiation detector device 4. This therefore results in a lower (gloss) value measured by the radiation detector device 4 than would result for the same surface to be examined, which differs from the surface shown in Fig. 5 only in that it fills the entire measuring area.

[0165] The optical detection device 20 proposed here preferably serves to adapt the (gloss) values ​​obtained, measured by the radiation detector device 4, to a curvature of the surface 10 to be examined (see Fig. 4) and / or a geometric extent of the surface to be examined (see Fig. 5) in such a way that a (measured) (gloss) value is obtained which is independent of the curvature of the surface 10 to be examined and / or of the geometric extent of the surface 10 to be examined.

[0166] For this purpose, the optical detection device 20 determines in particular whether there is a curvature of the surface 10 to be examined in the relevant measuring range of the device (i.e. within the measuring area) and / or whether the surface 10 to be examined extends completely over the entire measuring range or the entire measuring area of ​​the device.

[0167] If the surface 10 to be examined is curved within the measuring area or if the surface 10 to be examined does not extend completely over the measuring area, the optical detection device determines a ratio value V, which acts as a correction value for the measured value obtained from the radiation detector device 4.

[0168] Fig. 6 shows the optical detection device 20. This device comprises a telecentric lens device, designated overall by 30. Reference numeral 24 denotes an (optical) radiation detection device, such as a camera or a CCD chip.

[0169] Reference numeral 32 denotes a light source, such as, in particular but not exclusively, an LED or a plurality of LEDs, and reference numeral 34 denotes an aperture. The light emitted by the light source 32 is directed via a lens 36 and a beam splitter 12 onto the surface 10 to be examined (this occurs in the direction R2). The radiation reflected by the surface 10 is reflected in the direction R2', toward the radiation detection device, in particular the image detection device 24 or camera. This arrangement generates (approximately) parallel light for sample illumination.

[0170] By using the telecentric lens device, which is described in detail below, the captured image can be significantly improved.

[0171] Fig. 7 shows an illustration for determining the above-mentioned ratio value or fill factor. Here, reference symbol M denotes the maximum measuring range for a first radiation detector device 4 (for example, a measuring arrangement comprising a first radiation device 2 and a first radiation detector device 4, for example, for measuring a gloss value), such as a gloss detector.

[0172] The reference symbol K denotes the (maximum) measuring area of ​​the radiation detection device 24 (the irradiation device 22 or the optical detection device 20), which can be provided by an image recording device or camera. Thus, K could, for example, be provided by the sensor area of ​​a CCD chip (used in particular during the measurement) of the irradiation device 22 or the optical detection device 20.

[0173] The reference symbol W denotes the effective measuring area of ​​the gloss detector, for example, when a curved surface is being examined. As mentioned above, this area W is preferably determined from an image. The ratio between W and M yields the fill factor V.

[0174] This results in the fill factor being:

[0175] Fill factor = effective area W / maximum area M.

[0176] Within the scope of the present invention, it is therefore proposed to combine or unify a conventional gloss measurement and an inline observation from above. With such a setup as shown above, the surface areas contributing to the gloss (in particular, the surface areas contributing to the gloss when performing a conventional gloss measurement) can be determined, and their effective area can be determined.

[0177] These areas can be areas on curved surfaces that, for example, run perpendicular or parallel to the aforementioned measurement axis. It is also possible to measure the surface of objects that are smaller than the actual measurement spot for gloss measurement. For this purpose, as mentioned above, the objects must be placed on suitable holders below a measurement aperture. Reflections from the holders into the detectors should be avoided.

[0178] Another measurement option is to measure surfaces that have both glossy and matte components. These surfaces can be differentiated according to the matte and glossy components, and these can be calculated separately.

[0179] Figs. 8a and 8b show two exemplary measurements on curved surfaces 10. In the examples shown in Figs. 8a and 8b, the surface to be examined is the lateral surface of a (straight) (circular) cylinder. The lateral surface of the cylinder is uncurved in a direction MO along the axis of the cylinder. In a direction MO shown in Fig. 8a, seen perpendicular to the axis of the cylinder (which lies within the measuring surface and / or the measuring plane), the lateral surface to be examined here is curved. The lateral surface 10 to be examined therefore has a curvature in one direction of the measuring plane (or measuring surface) and is uncurved in a direction of the measuring plane (or measuring surface) perpendicular to this. Here, for example, it is possible to measure perpendicular to a radius of curvature or along the axis of the cylinder (i.e. in the direction of arrow MO in Fig. 8b)) or parallel to the radius of curvature orperpendicular to the cylinder axis (and along the measuring surface or the measuring plane), i.e., along the arrow direction MO shown in Fig. 8b. Depending on the measurement setup, significantly different images can be expected.

[0180] Fig. 9 shows a representation of different surfaces and the corresponding images acquired. The top row shows dark-field images. These dark-field images cannot reproduce the curvature of the surfaces. The bright spots represent dust particles on the surface. The middle row shows images acquired inline, and the bottom row shows an illustration of the fill factor. The surface examined here is a glossy surface.

[0181] In Fig. 9, all images were taken at a scattering angle, ie gloss measurements were performed.

[0182] The first image in the top row shows a recorded image of the flat surface. The image in the first row and second column shows a recorded image of a cylinder surface with a radius of curvature of 200 mm, oriented vertically (in particular, the gloss measurement relative to the cylinder axis). In other words, with this orientation of the device 1 relative to the cylinder's lateral surface to be examined, the direction of incidence R1 of the (first) radiation device 2 and / or the direction of emission R1' run essentially perpendicular to the cylinder axis.

[0183] The third column and the top row also show an image of a surface, in this case the outer surface of a cylinder, with a radius of curvature of 200 mm, but here it was taken parallel to the radius of curvature. In particular, the surface examined in the third column is the one from the second column. However, compared to the second column, the measurement is carried out with the surface to be examined rotated by 90° in relation to the device. In other words, with the orientation of the device 1 to the outer surface of the cylinder to be examined shown in the third column, the direction of incidence R1 of the (first) radiation device 2 and / or the direction of emission R1' run essentially parallel to the axis of the cylinder.

[0184] The images in the two right columns of the top row each show a corresponding image of a surface of a cylinder with a radius of curvature of 50 mm, once in the vertical direction and once along the axis.

[0185] The bottom line shows a representation from which the fill factor for each situation can be displayed and illustrated.

[0186] Analogous to Fig. 7, the reference symbol M denotes the predetermined (maximum) measuring area. This is predetermined by the device 1, in particular by the arrangement and orientation (irradiation direction R1) of the (first) radiation device 2 and the arrangement and orientation (radiation direction RT) of the (first) radiation detector device 4 and, if appropriate, by optical elements such as one or more apertures in the beam path between the (first) radiation device 2 and the (first) radiation detector device 4.

[0187] For flat surfaces (1st column), the entire surface 10 to be examined, imaged within M, contributes to the emission of radiation radiated by the (first) radiation device 2 in the direction of the (first) radiation detector device 4.

[0188] The reference symbol W denotes the image of the surface 10 to be examined irradiated by the (first) radiation device 2, which contributes to the radiation emission in the emission direction R1' for the detection of this emitted radiation by the (first) radiation detector device 4. For planar or flat surfaces to be examined, this area corresponds to M, since the emission direction RT at every point on the surface to be examined is opposite to the incident radiation direction (relative to a measurement plane). For cylindrically curved surfaces, as illustrated in columns 2-5, outer dark stripes can be seen in the inline images laterally to the central bright stripe.These dark stripes in the inline images arise because the corresponding surface areas are tilted relative to the irradiation direction R2 in such a way that the radiation emitted by the irradiation device 22 in the irradiation direction R2 and impinging on these surface areas is not emitted or reflected in the direction R2' toward the radiation detection device 24, but rather in a different radiation direction. Therefore, the corresponding areas of the detection surface (K) of the radiation detection device 24 remain dark.

[0189] A similar situation applies to the surface regions of the surface to be examined that are inclined relative to the measuring plane (or the measuring surface) (due to the curvature of the surface to be examined) during the measurement carried out by the (first) radiation device by irradiating these surface regions with radiation in the irradiation direction R1 and emitting radiation in response to the irradiated radiation and the (first) radiation detector device. Here, too, the radiation irradiated into these surface regions of the surface to be examined that are inclined relative to the measuring plane is emitted and / or reflected in a radiation direction different from the radiation direction RT due to the inclination of these surface regions, so that the emitted radiation cannot be detected by the (first) radiation detector device 4.These (inclined) surface areas therefore do not contribute to the measured value (such as a gloss value) determined by means of the (first) radiation detector device 4.

[0190] Of the (maximum) measuring area M, only the areas marked with W in the last line (due to their inclination with respect to the measuring plane or the measuring area) contribute to the measured value determined by means of the (first) radiation detector device.

[0191] The areas W in the last two columns are significantly narrower compared to the surfaces examined in the 2nd and 3rd columns, since the surfaces examined in the last two columns, with a radius of curvature of 50 mm, have a greater curvature than the surfaces examined in the 2nd and 3rd columns, which have a significantly larger radius of curvature of 200 mm. The smaller radius of curvature or the greater curvature of the respective cylindrically shaped surface means that only a correspondingly narrower surface area has a sufficiently low inclination with respect to the measuring plane or measuring surface to emit or reflect radiation in the radiation direction RT, so that this can be detected by the (first) radiation detector device 4.

[0192] The effect of the orientation of the surface to be examined with respect to a rotation of the surface to be examined by 90° within the measuring plane is further illustrated.

[0193] In the orientation shown in the second and fourth columns, a first surface direction (which runs along the measuring plane), along which the surface to be examined is curved, runs perpendicular to the irradiation direction R1. A second surface direction which is different from the first surface direction, which is perpendicular to the first surface direction and also runs within the measuring plane, extends in particular within a cross-sectional plane which runs through the measuring plane and / or the surface to be examined, the (first) radiation device 2 and the (first) radiation detector device 4. The surface to be examined has a non-curved, i.e. rectilinear, surface profile along this second surface direction. The first and second surface directions relate to a coordinate system with respect to the surface to be examined and preferably run within the measuring plane.

[0194] In the orientation shown in the third and fifth columns, the surface to be examined is rotated by 90° (relative to a rotation axis perpendicular to the measurement plane). In this orientation, the above-mentioned second surface direction, along which the surface to be examined has a non-curved surface profile, is perpendicular to the irradiation direction R1 or perpendicular to the cross-sectional plane passing through the measurement plane and / or the surface to be examined, the (first) radiation device 2, and the (first) radiation detector device 4.In this orientation, the (maximum) measuring area M covers a larger surface area of ​​the surface to be examined compared to the orientation shown in column 2, which has a sufficiently low inclination to emit or reflect radiation radiated onto the respective surface area by the (first) radiation device to the (first) radiation detector device, so that this can be detected, despite the inclined surface.

[0195] For the orientation shown in the third column, the fill factor is therefore larger than for the orientation of the surface to be examined shown in the second column.

[0196] Fig. 10 shows the similar images, this time for a matte surface, where the irradiation is once perpendicular to the radius of curvature and once parallel to it.

[0197] The dark-field images shown here in the first row cannot reproduce the curvature of the surfaces. The bright spots represent dust particles on the surface.

[0198] It can be seen that the images of the surfaces with the larger radius of curvature result in significantly wider stripes than the images of the surfaces with the smaller radius of curvature.

[0199] Larger radii of curvature imply a flatter surface, while smaller radii of curvature result in a more curved surface.

[0200] The bottom row shows representations of the fill factor for each surface when scanning. When the ellipse is completely filled, the fill factor is 1. It can be seen that the filled area is significantly reduced in the vertical scans (second and fourth columns), which is to be expected since the strip's extension is perpendicular to the longer axis.

[0201] It can also be seen that, as expected, the contrast on the matte surface is significantly lower than on the glossy surface.

[0202] Fig. 11 shows another illustration of how to obtain the measurement results. Here, a grayscale image is reduced to a binary image, i.e., an image that displays either black or white pixels. Fig. 12 shows a diagram for determining the threshold factor or threshold calculation. The fill factor is plotted on the abscissa, and the respective gloss value (measured here at a gloss angle of 60°) is plotted on the ordinate. As mentioned above, the fill factor can be determined in various ways.

[0203] The simplest algorithm is a thresholding method for the cross-section of the brightness distribution in the image. The thresholds are then preferably learned. Glass standards with different curvature radii and gloss values ​​are preferably selected. The linear relationship between fill factors 0 and 1 serves as a preferred guideline.

[0204] Figs. 13 and 14 show an overall view of a telecentric lens 30. The radiation emerging or reflected from the surface to be examined passes through this lens onto the detection device.

[0205] Reference numeral 50 denotes a first lens, and reference numeral 51 a second lens, which together preferably form an achromatic lens. Reference numeral 53 denotes a third lens, which is preferably biconvex.

[0206] Preferably, a distance between the first lens 50 and the second lens 51 (wherein reference is made here to the distance between a first surface of the first lens facing the second lens and that of a first surface of the second lens facing the first lens 50) is greater than 10 mm, preferably greater than 20 mm, preferably greater than 25 mm, preferably greater than 27 mm, and preferably greater than 30 mm.

[0207] Preferably, a distance between the first lens 50 and the second lens 51 (wherein reference is made here to the distance between a first surface of the first lens facing the second lens and that of a first surface of the second lens facing the first lens 50) is less than 50mm, preferably less than 45mm, preferably greater than 40mm, and preferably greater than 35mm.

[0208] Preferably, the first lens 50 has a maximum thickness that is greater than 3 mm, preferably greater than 4 mm. Preferably, the first lens 50 has a maximum thickness that is less than 7 mm, preferably less than 6 mm, preferably less than 5 mm, and particularly preferably less than 4.5 mm. Preferably, the first lens has a diameter that is greater than 10 mm, preferably greater than 15 mm, and particularly preferably greater than 20 mm. Preferably, the first lens has a diameter that is less than 40 mm, preferably less than 35 mm, and particularly preferably less than 30 mm.

[0209] Preferably, the second lens 51 has a maximum thickness greater than 3 mm, preferably greater than 4 mm, and preferably greater than 5 mm. Preferably, the second lens 51 has a thickness less than 9 mm, preferably less than 8 mm, and particularly preferably less than 7 mm.

[0210] Preferably, the second lens has a diameter greater than 5 mm, preferably greater than 6 mm, preferably greater than 7 mm, and particularly preferably greater than 8 mm. Preferably, the second lens 51 has a diameter less than 12 mm, preferably less than 11 mm, preferably less than 10 mm, and particularly preferably less than 9 mm.

[0211] The applicant reserves the right to claim protection for the telecentric lens described here and its application to the devices described here.

[0212] Reference numeral 54 denotes a holder or mount for the lens 50, and reference numeral 56 denotes a spacer ring. Reference numeral 55 refers to a retaining ring.

[0213] Reference numeral 64 denotes a plug-on adapter that is held to the lens assembly of the two lenses 50, 51 by means of a threaded pin. Reference numeral 58 refers to a lock ring.

[0214] Reference numeral 65 denotes a diaphragm mount. Reference numeral 62 denotes a mounting bracket, and reference numeral 68 denotes an adapter (particularly for a test setup).

[0215] Fig. 15 shows a further illustration of the telecentric lens. It can be seen that the distance between the surface to be examined and the first lens is greater than 20 mm, preferably greater than 30 mm, preferably greater than 40 mm, preferably greater than 50 mm, and preferably greater than 60 mm. The distance between the surface to be examined and the first lens is preferably less than 100 mm, preferably less than 90 mm, preferably less than 80 mm, and particularly preferably less than 70 mm.

[0216] Preferably, the distance between the second lens and the image recording device, for example a CCD chip, is greater than 10mm, preferably greater than 12mm, preferably greater than 14mm and preferably greater than 16mm.

[0217] Preferably, the distance between the second lens and the image recording device, for example a CCD chip, is less than 30mm, preferably less than 25mm, preferably greater than 20mm and preferably greater than 18mm.

[0218] Fig. 16 a,b show a flat sample having shiny areas A and matte areas B. The elliptical area E marks the classic observation spot or the specified (maximum) measuring area M.

[0219] In the case shown, two effective surfaces result. The first surface is the intersection of the ellipse with the bright areas A, and the second surface is the intersection of the ellipse with the dark areas B.

[0220] The classic gloss value is preferably a linear combination of both areas. This means that the respective classic gloss values ​​for A and B can be calculated from the area distribution.

[0221] Such a calculation of the classical gloss value Gtotai based on the total (maximum) measuring area M (here represented by the ellipse E) with area A to tai results in particular from the classic gloss value Gi of the grey marked partial areas and the area Ai of the partial areas B within the ellipse E as well as the classic gloss value G2 of the area A and the area A2 of the area A within the ellipse E from:

[0222] Gtotai = Gl * Al / Atotal + G2 * A2 / Atotal If one of the two values ​​Gi and G2 is known, for example by measuring on a spot of the sample where only one type occurs, the above equation can be solved.

[0223] Otherwise, the ratio R of G1 and G2 can preferably be determined (approximately) via the brightnesses h and I2 in the camera image or in the radiation detection device 24:

[0224] R = I1 / I2 = G1 / G2.

[0225] This relationship can be used to solve the above equation.

[0226] For example, the applicant has used a classic gloss value of G2 = 100 Gil measured at the edge of the sample plate and an area ratio of A2 / A to tai = 2 / 3 and 12 = 325110, as well as an area ratio A Atotai = 1 / 3 and h = 6046, G1 was determined by G1 = R * G2 = 0.019 * G2 = 1.9 Gil. This resulted in Gtotai = 1.9 Gil * 0.33 + 100 Gil * 0.66 = 66.6 Gil.

[0227] With the classic device, a gloss value of Gtotai = 64.8 Gil was measured at 60°.

[0228] The device according to the invention preferably includes the classic gloss measurement and the camera observation in one housing.

[0229] The device can be a handheld device or a device portable by a user. In addition to the handheld device, the device can also be a device suitable for various robotic systems.

[0230] These robot systems can be multi-axis robots, in-line systems, and / or XY tables. In these cases, the devices can measure at distances of between 3 and 5 mm from the surface, for example. Therefore, both convex and concave curved surfaces are possible. It is important to note that for classic gloss measurements, one should remain within the measuring plane or the measuring range of the device. With robotic devices, this is achieved at a certain distance from the floor. As mentioned above, the effective measuring range does not have to be contiguous. It can also include multiple (particularly horizontal) surface elements.

[0231] The absence of shadows is preferred for camera observation from above. Shadows can be problematic for conventional measurements at large angles.

[0232] The elliptical observation spot for classic gloss measurement can be detected in production using a telecentric camera (when using a (flat) matte surface). For this purpose, a light source can be substituted for the photoelectric element. For this purpose, characteristic data (e.g., a predefined measurement area) is preferably stored in a memory device of the device (for image analysis).

[0233] The applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided they are novel, individually or in combination, over the prior art. It is further noted that the individual figures also describe features that may be advantageous in and of themselves. The skilled person will immediately recognize that a specific feature described in a figure may be advantageous even without adopting additional features from that figure. Furthermore, the skilled person will recognize that advantages may also arise from a combination of several features shown in individual or different figures.

Claims

Patent claims 1. Method for examining optical surface properties of a surface to be examined (10) comprising the steps: - irradiating radiation onto the surface to be examined (10) by means of an irradiation device (22); - recording a spatially resolved image of the radiation emitted and in particular reflected by the surface (10) in response to the incident radiation by means of a radiation detection device (24) which has a maximum detection area (K) for detecting the radiation reaching it; - Determination of at least one effective area value (W) which is characteristic of an area lying in a predetermined and / or predeterminable measuring area (M) within the maximum detection area (K), which is reached by the emitted, in particular reflected, radiation in a predetermined and / or predeterminable manner, in particular with regard to a brightness and / or color value; - Determination of at least one ratio value (V) which is characteristic of a relationship between the effective area value (W) and the measuring area (M).

2. Method according to claim 1, characterized in that the predetermined and / or predeterminable measuring surface is predetermined by a first radiation device (2) which is suitable and intended to radiate radiation onto the surface to be examined under a predetermined first irradiation direction (R1), in particular deviating from a vertical direction.

3. Method according to at least one of the preceding claims, characterized in that the first radiation device (2) in cooperation with a first radiation detector device (4) is suitable and intended for carrying out a gloss measurement.

4. Method according to at least one of the preceding claims, characterized in that the measuring area (M) is characteristic of a size (and / or arrangement) of that area within the maximum detection area (K) which is reached by radiation emitted by a first radiation device (2) when using a flat surface as the surface to be examined (10) and / or the measuring area (M) is characteristic of a size of that area which results when the radiation emanating from a first radiation device (2) is completely reflected to a first radiation detector device (4).

5. Method according to at least one of the preceding claims, characterized in that the radiation is irradiated onto the surface to be examined (10) through an opening in a housing and the radiation emitted by the surface to be examined passes through this opening.

6. Method according to at least one of the preceding methods, characterized in that a threshold method is used to determine the area value (W) and / or the ratio value (V).

7. Method according to the preceding claim, characterized in that the threshold method determines and / or evaluates a brightness distribution in the image recorded by the radiation detection device (24).

8. Method according to at least one of the preceding claims 5 - 6, characterized in that Threshold values ​​for the thresholding method are determined using standard surfaces.

9. Method according to at least one of the preceding claims, characterized in that the surface to be examined is curved and / or smaller than a ne / the first radiation device has a predetermined / illuminable measuring surface and / or both shiny and matt surface areas.

10. Method according to at least one of the preceding claims, characterized in that using the ratio value (V) which results for a surface to be examined according to the preceding claim, a gloss value for an ideal surface is determined, wherein this ideal surface corresponds to the examined surface in terms of its optical properties, but the ideal surface is flat and is at least as large as the measuring area and / or the effective area value (W).

11. Method according to at least one of the preceding claims, characterized in that the irradiation device (22) radiates the radiation substantially perpendicularly onto the surface (10) and the radiation detection device (24) detects radiation which is emitted by the surface to be examined substantially perpendicularly thereto.

12. Device (1) for examining optical surface properties of surfaces, comprising an irradiation device (22) which is suitable and intended to irradiate radiation in a predetermined irradiation direction onto the surface to be examined, comprising a radiation detection device which is suitable and intended to record a spatially resolved image of the radiation emitted and in particular reflected by the surface in response to the irradiated radiation, wherein the radiation detection device has a maximum detection area (K) for detecting the radiation impinging on it, and comprising an image evaluation device which is suitable and intended to determine at least one effective area value (W) which is characteristic of an area lying in a predetermined and / or predeterminable measuring area (M) within the maximum detection area (K), which area is covered by the output,in particular reflected radiation in a predetermined and / or predeterminable manner, in particular with regard to a brightness and / or color value, and with a processor device which is suitable and intended to at least, to determine at least one ratio value (V) which is characteristic of a relationship between the area value (W) and the measuring area.

13. Device according to the preceding claim, characterized in that the device (1) has a housing and this housing has an opening and the irradiation device is suitable and intended to irradiate the surface through this opening and the radiation detection device is suitable to detect radiation from the surface in response to the radiation emitted by the irradiation device and passing through the opening.

14. Device according to at least one of the preceding claims, characterized in that the optical detection device (20) has a telecentric lens arrangement (30), wherein this telecentric lens arrangement is preferably arranged between the surface to be examined (10) and the radiation detection device.

15. Device according to at least one of the preceding claims, characterized in that the device has a radiation deflection device (12) which is suitable and intended to deflect the radiation emanating from the irradiation device in such a way that this radiation strikes the surface in the second irradiation direction (R2), wherein preferably the radiation deflection device deflects the radiation emanating from the irradiation device at an angle which is between 30° and 150°.

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