Device and method for detecting surface characteristics

Abstract

The invention relates to a method for detecting optical surface properties of a surface to be inspected (10), comprising the following steps: irradiating the surface to be inspected (10) with radiation by an irradiation device (22); a radiation detection device recording a spatially resolved image of radiation emitted and in particular reflected by the surface (10) in response to the irradiated radiation, the radiation detection device having a maximum detection area (K) for detecting radiation reaching this area; determining at least one effective area value (W) characterizing a region within a predetermined and / or predeterminable measurement region (M) located within the maximum detection region (K), the emitted, in particular reflected radiation reaching the region in a predetermined and / or predeterminable manner, in particular with respect to luminance and / or color values; and determining at least one ratio value (V) characterizing a relationship between the effective area value (W) and the measurement region (M).

Description

TECHNICAL FIELD

[0001] The present invention relates to a device and method for detecting properties of optical surfaces. The invention is described with reference to the detection of surfaces of motor vehicles, but it is noted that the device can also be used for other surfaces, such as (small) buttons on furniture, electronic components or electronic devices. BACKGROUND

[0002] There are various methods and devices in the prior art for detecting properties of such surfaces. One of the properties to be detected is the so-called gloss, which is determined by illuminating the surface to be detected and measuring or detecting the reflected radiation.

[0003] Conventional gloss measurements have strict requirements on the optical configuration. The measurement values of conventional gloss measurements are defined only for a flat polished black glass (GU100 - n = 1.567 from ISO 2813). If these specifications are not strictly followed, for different surface types, the measurement values will not be recorded in linear correlation with the standard. This means that a measurement that complies with the standard must remain unchanged for uneven samples as for flat samples.

[0004] If the photoelectric cell in the standard configuration is replaced by a camera, an image of the illumination aperture can be obtained. The sample surface is not imaged sharply enough to measure the surface shape and texture indirectly. Therefore, when the photoelectric cell is replaced by a camera, no detailed information about the surface can be obtained. However, unlike the photoelectric cell, the camera can compensate for any tilt of the measurement device with respect to the surface normal. The aperture image can be tracked and the aperture can be virtually reproduced by the pixels of the camera.

[0005] These camera images can also be used to indicate the correct position of the measurement device. The aperture image on the area detector must be within defined limits in order to make a correct measurement. The applicant reserves the right to claim protection for such a design.

[0006] The area sensor at the position of the conventional detector is preferably able to track the reflected signal. For example, for tracking, the brightness barycenter in the recorded intensity image can be used.

[0007] If the measurement device is tilted, the bright illumination aperture image will deviate from the defined position. The sample surface to be measured can also be actively tilted, for example when a web is moved in a robotic application. If the barycenter deviates from the defined tolerance range, the measurement is preferably classified as invalid and feedback is given about the excessive tilt.

[0008] The area sensor can also be used to measure the gloss value. For this purpose, a virtual aperture can be defined which has the same size as the mechanical aperture. The total brightness value of the virtual aperture corresponds to the conventional measurement value. The virtual aperture can also be placed near the center of gravity and coupled with the center of gravity. This can compensate for the tilt of the measuring device to some extent. The HDR image is the preferred option for making an absolute measurement record.

[0009] The area sensor can also be used in combination with the conventional sensor. For this purpose, part of the detector signal can be decoupled, in particular by means of a beam splitter, and supplied to the area sensor. The area sensor detects the tilt. The signal is preferably measured simultaneously using the conventional sensor with the mechanical aperture. SUMMARY

[0010] It is an object of the present application to enable gloss measurement, in particular gloss measurement which is traceable to conventional gloss measurement, even for curved surfaces. It is a further object of the present application to be able to determine the surface properties, in particular the gloss value, of very small surfaces. It is a further object of the present application to be able to determine surfaces which have both glossy and matt regions.

[0011] For curved surfaces, the present application proposes to combine the surface geometry description with the conventional gloss measurement. However, this method can also be used for smaller surfaces and for surfaces which have both matt and glossy regions.

[0012] Various observation methods are known from the prior art. One such method is the measurement point observation method.

[0013] The measurement point observation method is generally used to detect contamination or damage on a surface. A frequently used method of illumination is called dark field (dark field microscopy). Only light which is diffusely reflected from the surface can hit the observation unit. This method cannot be used for uneven surfaces and / or shiny surfaces. On shiny surfaces, for example, dust particles are visible in the case of diffuse reflection of the light.

[0014] Dark field illumination can be used on matt surfaces, but even so, curved surfaces cannot be seen using circular illumination. However, for rotational freedom, omnidirectional illumination is required, i.e. the measurement value should be independent of the position of the measuring device. Scratches can be detected in the dark field, but deep scratches can lead to shadows.

[0015] Only using direct view illumination and, as described in the present application, in combination with a telecentric objective, can high-gloss or reflective sample surfaces be captured. The applicant was able to determine that the telecentric objective prevents the reflected light of the light source from being captured on the surface. This effect is based on the limited angle of acceptance and the depth of field in the telecentric case. In addition, the large lens of the telecentric objective can capture all light, for example in the case of parallel incidence and reflected light. Using a conventional objective, the reflected light at the edge of the measurement range cannot be captured.

[0016] In a microscope, this direct illumination is called bright-field illumination. To avoid light source reflection (in critical illumination), so-called Köhler illumination can be used here. Compared to critical illumination, Köhler illumination can achieve uniform illumination of the object.

[0017] However, Kohler lighting is relatively complex, therefore the object of this invention is also to provide a simpler arrangement. This will be described in more detail below, and requires the use of a lens with an aperture.

[0018] In industrial image processing, flat and uniform illumination is used to avoid reflection problems in a cost-effective and user-friendly manner. The light source consists of a uniform illumination area the same size as the observation area. For example, this illumination can be achieved using an LED matrix and a diffuser disk. Within the scope of this invention, it is suggested, for example, that the connection be made using a beam splitter (diffuse coaxial illumination).

[0019] Another objective of this invention is to use a cost-effective and easy-to-use lighting method.

[0020] The advantageous new measuring device generates clearer and more detailed surface images. Curvature can be interpreted from the brightness gradient in the image. The new device is preferably non-rotational. Even deep surface damage can be seen without shadows.

[0021] In image processing, the combination of telecentric objectives and telecentric illumination is typically used for transmitted light rather than non-incident light. However, for the apparatus described herein, this simple reflective direct-view design is not known in the prior art and is an important aspect of the invention.

[0022] Another object of the present invention is to provide an apparatus and method that also allows for standardized evaluation of non-flat surfaces or surfaces that are not uniformly glossy or uniformly diffuse (i.e., matte surfaces).

[0023] Another object of the present invention is to provide an apparatus and method that are also capable of evaluating the surface of very small components (e.g., electronic components). Furthermore, it should also be possible to evaluate small operating units, such as small buttons (e.g., on a smartphone).

[0024] The above-mentioned objectives are achieved by the apparatus and method described in the independent patent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

[0025] An apparatus for detecting the optical properties of a surface according to the present invention includes: a first radiation device adapted to irradiate a surface to be inspected with radiation along a first irradiation direction; and a first radiation detector device adapted to detect radiation irradiated by the first radiation device onto the surface to be inspected and reflected by the surface along a (first) emission direction. The apparatus further includes an optical detection device comprising: an irradiation device adapted to irradiate a surface to be inspected with radiation along a second irradiation direction; and a radiation detection device adapted to detect radiation irradiated by the irradiation device onto the surface to be inspected and emitted by the surface along a second emission direction.

[0026] According to the present invention, the second irradiation direction and the second emission direction are substantially opposite.

[0027] "Opposite" means that the radiation directions are basically parallel but opposite to each other. "Basically parallel" means that the angle between the radiation directions is between 170° and 190°, preferably between 175° and 185°, between 178° and 182°, and especially preferably between 179° and 181°.

[0028] Another apparatus for detecting the optical properties of a surface according to the invention comprises: an irradiation device adapted to irradiate a surface to be inspected with radiation along a predetermined irradiation direction (particularly an irradiation direction referred to above as a second irradiation direction); and a radiation detection device adapted to record a spatially resolved image of radiation emitted (particularly 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 incident thereon. Preferably, the radiation detection device is adapted to record HDR images and records HDR images.

[0029] Furthermore, the device has an image evaluation apparatus (particularly processor-based) suitable for determining at least one effective area value characterizing a region within a predetermined and / or predeterminable measurement region located within the maximum detection region. This is achieved by emitting (particularly reflecting) radiation from the surface in a predetermined and / or predeterminable manner (particularly with respect to brightness and / or color values) in response to radiation irradiated by the (radiating device). Preferably, exactly one effective area value is determined. However, it is also conceivable to determine two, three, or more effective area values.

[0030] Furthermore, a processor device is provided suitable for determining at least one ratio value that characterizes the relationship between an area value and a measured area. The processor device may be an image evaluation device. However, it is also contemplated that the processor device may (at least partially) differ from an image evaluation device. Preferably, exactly one ratio value is determined. However, it is also contemplated that two, three, or more ratio values ​​may be determined.

[0031] The device may have all the features of the aforementioned device, either individually or in combination, and vice versa. Furthermore, the two devices may have all the following features, either individually or in combination.

[0032] Due to insufficient surface curvature or size, not all radiation emitted by a radiation or irradiation device that hits the surface will be reflected back to the radiation detection device.

[0033] The aforementioned relationship or ratio between area values ​​and measured areas takes this situation into account. This relationship will also be referred to as the fill factor below. This value can be used to derive conclusions about the optical properties of the corresponding plane from the optical properties of the curved surface.

[0034] Therefore, the fill factor is a factor that depends on the curvature, the size of the object, or the gloss or matte finish of the surface.

[0035] Preferably, the fill factor is calculated as follows: Fill factor = Area value / Measured area (or Partial area of ​​the measuring device / Total area). Preferably, both the area value and the measured area are expressed in mm. 2 The unit is given. However, it is also conceivable that the area value and the measured area are expressed in the same (but especially any, for example, different from mm) units. 2 (area) is a unit of measurement for the area measured.

[0036] In another advantageous embodiment, the device is portable. This allows the device to be guided by a user's hand, but it can also be guided by a robot or robotic arm.

[0037] The surface to be inspected is preferably a curved surface or a very small surface. A very small surface is understood to be less than 4 cm. 2 Preferably less than 3 cm 2 Preferably less than 2 cm 2 Preferably less than 1 cm 2 Preferably less than 0.5 cm 2 Preferably less than 0.3 cm 2 Preferably less than 5mm 2 The surface to be inspected. Specifically, the maximum (geometric) range of the surface to be inspected in at least one direction (preferably in at least two mutually perpendicular directions) is less than 4 cm. 2 Preferably less than 3 cm 2 Preferably less than 2 cm 2 Preferably less than 1 cm 2 .

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

[0039] In principle, when the area of ​​the measurement point is small (less than 1 mm) 2 When the device described herein and the measurements performed by these devices are sensitive to changes in tilt and distance (the distance between the device and the surface under test), the following applies.

[0040] For repeatable measurements, a minimum spot size is required in traditional gloss measurements. Because the measurement point size is very small, positioning the measuring device on the object is extremely difficult, and the measured value is highly dependent on accurate positioning.

[0041] These surfaces present challenges to existing technologies for the following reasons: due to the small curvature or size of the surface under inspection, for example in the context of conventional gloss measurement, not all the radiation emitted by the radiation device can pass through the surface to reach the radiation detector device.

[0042] Traditional gloss measurements require a flat surface. Calibration is also always performed only on flat surfaces. For curved surfaces, a certain proportion of incident radiation will not be reflected back to the radiation detector equipment, and this must be taken into account when evaluating measurement results, especially those generated using traditional photometric methods.

[0043] For very small surfaces, not all incident radiation can reach the surface being inspected. This also requires correction.

[0044] Therefore, this invention proposes to combine conventional observation and / or illumination with direct illumination, especially telecentric direct observation.

[0045] In a preferred embodiment, the second irradiation direction, i.e., the direction in which radiation from the irradiation device hits the surface, is substantially perpendicular to the surface to be inspected. Thus, the (second) irradiation direction may be opposite to the direction of radiation emitted (especially reflected) from the surface. Preferably, the radiation emitted from the surface is reflected radiation (i.e., radiation that is first irradiated by the second irradiation device onto the surface and then reflected by the surface).

[0046] In other words, the second irradiation direction, that is, the direction in which the radiation from the irradiation device hits the measurement plane where the surface under test is located (and / or will be located), is substantially perpendicular to the measurement plane. As described above, this allows the irradiation device to be positioned opposite to the direction of radiation emitted (especially reflected) by surfaces arranged (similarly designed) on the measurement plane.

[0047] Preferably, the surface to be inspected is arranged on and / or positioned on the measuring plane for inspection. If the surface to be inspected is completely flat, then the plane lies within the measuring plane.

[0048] In another preferred embodiment, the angle formed between the first irradiation direction and the surface to be inspected (and / or the measurement plane) is greater than 15°, preferably greater than 30°, preferably greater than 35°, preferably greater than 40°, and especially preferably greater than 50°.

[0049] In another preferred embodiment, the angle formed between the first irradiation direction and the surface to be inspected (and / or the measurement plane) is less than 80°, preferably less than 70°, and more preferably less than 65°. This angle is particularly preferably 60°.

[0050] Particularly preferably, the first radiation device emits radiation onto the surface (and / or the measuring plane) at an angle of approximately 45° or 60°, and the first radiation detector device detects radiation reflected from the surface at an angle of approximately 45° or 60°. Preferably, the irradiation angle and the angle of receiving radiation are opposite to each other.

[0051] Preferably, the apparatus includes a second radiation device adapted to irradiate the surface to be inspected with radiation along a second (gloss angle) irradiation direction; and a second radiation detector device adapted to detect radiation emitted by the second radiation device onto the surface to be inspected and reflected by the surface along the second (gloss angle) emission direction. Preferably, the second (gloss angle) irradiation direction and the second (gloss angle) emission direction are opposite to the angle formed by the measuring plane or the surface to be inspected (flat).

[0052] Preferably, the device includes a third radiation device adapted to irradiate the surface to be inspected with radiation along a third (gloss angle) irradiation direction; and a third radiation detector device adapted to detect radiation emitted by the third radiation device onto the surface to be inspected and reflected by the surface along the third (gloss angle) emission direction. Preferably, the third (gloss angle) irradiation direction and the third (gloss angle) emission direction are opposite to the angle formed by the measuring plane or the surface to be inspected (flat).

[0053] Preferably, the design of the second radiation device and the second radiation detector device and / or the third radiation device and the third radiation detector device (except for the irradiation direction and the emission direction) is similar to or the same as that of the first radiation device and the first radiation detector device.

[0054] Preferably, the angle formed by the first and / or second and / or third radiation device (or the first and / or second and / or third radiation detector device) and the measuring plane or the surface to be inspected (flat) is selected from the group consisting of the following ranges: 15°-25°, 40°-50°, 55°-65°, 70°-80° and 80°-90°, and more preferably from the group consisting of the following angles: approximately 20°, 45°, 60°, 75° and 85°.

[0055] In another preferred embodiment, the device has a housing, within which are disposed a first radiation device, a first radiation detector device, an irradiation device, and a radiation detection device.

[0056] In a particularly preferred embodiment, the housing has an opening through which the first radiating device and the irradiation device can irradiate the surface. Particularly preferably, this opening is the only opening in the housing, through which light can exit and enter the housing. This opening also preferably defines a measuring plane.

[0057] In a preferred embodiment, the device has a spacer element that separates the housing (particularly the opening of the housing) from the surface to be inspected during measurement. During measurement, pins or feet can be positioned on the bottom of the housing or on the side facing the surface to maintain a distance between the opening and the surface. These pins offer particular advantage when inspecting curved surfaces.

[0058] The height or length of these pins is preferably greater than 0.2 mm, more preferably greater than 0.3 mm, more preferably greater than 0.5 mm, more preferably greater than 0.7 mm, and especially preferably greater than 1.0 mm. Preferably, the height or length of these pins is less than 10 mm, more preferably less than 8 mm, more preferably less than 6 mm, especially preferably less than 5 mm, and preferably less than 4 mm.

[0059] Particularly preferably, at least three such pins or feet are provided.

[0060] Particularly preferably, a light-shielding element is provided between the spacer element and the opening. This light-shielding element is preferably a flexible element that (completely) surrounds the opening, such as a rubber seal.

[0061] Preferably, the distance between two adjacent spacer elements is greater than 1 cm, more preferably greater than 2 cm. Preferably, the distance between two adjacent spacer elements is less than 10 cm, more preferably less than 8 cm, and more preferably less than 7 cm.

[0062] Preferably, a cavity is formed within the housing, into which both the radiation device and the irradiation device irradiate. The cavity is preferably completely (except for the opening) surrounded by a radiation-absorbing wall.

[0063] In another advantageous embodiment, the device has a housing with an opening through which an irradiation device is adapted to irradiate a surface, and a radiation detection device is adapted to detect radiation from the surface in response to radiation emitted by the irradiation device and passing through the opening.

[0064] In another advantageous embodiment, the device has a radiation deflection device (also called a beam splitter, preferably 50:50) adapted to deflect the radiation emitted by the irradiation device so that the radiation impacts the surface along a second irradiation direction.

[0065] Preferably, the radiation deflection device deflects the radiation emitted by the irradiation device by an angle of 30° to 150°.

[0066] Preferably, the angle is 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°.

[0067] Preferably, the angle is less than 150°, more preferably less than 140°, more preferably less than 130°, more preferably less than 120°, more preferably less than 110°, more preferably less than 100°, and more preferably less than 95°.

[0068] In another preferred embodiment, the radiation deflection device is designed as a mirror, particularly a partially transparent mirror. Preferably, the ratio between transmitted and reflected radiation is between 30:70 and 70:30, more preferably between 35:65 and 65:35, more preferably between 40:60 and 60:40, more preferably between 45:55 and 55:45, and particularly preferably around 50:50.

[0069] Preferably, the reflectivity of the radiation deflection device or mirror varies depending on which side the radiation impacts from. Preferably, a portion of the radiation from the irradiation device is reflected onto the surface, and a portion of the radiation reflected from the surface is transmitted and reaches the (second) radiation detection device.

[0070] By using such a radiation deflection device, a surface can be irradiated in a predetermined direction (e.g., vertical direction), and radiation (especially spatially resolved radiation) in that direction (or more precisely, in the opposite direction) can also be detected.

[0071] In another preferred embodiment, the device has an objective lens (or objective lens assembly), particularly a telecentric objective lens. This telecentric objective lens is preferably positioned between the surface to be inspected and the (radiation) detection equipment (particularly an image detection equipment).

[0072] In another advantageous embodiment, the (second) radiation detection device is adapted to output a spatially resolved image of the radiation incident on it and / or the surface to be inspected.

[0073] A telecentric objective lens is particularly preferred for imaging the surface to be inspected on a radiation detection device (especially an image recording device). As mentioned above, the use of a telecentric objective lens on the observation side, especially in the case of direct observation, is unknown in the prior art related to this invention. However, the applicant has recognized that direct observation is particularly effective using a telecentric objective lens.

[0074] The present invention also relates to an optical inspection apparatus for optically inspecting a surface, comprising: an irradiation apparatus adapted to irradiate radiation onto the surface to be inspected along a (second) irradiation direction; and a radiation detection apparatus adapted to detect radiation irradiated onto the surface to be inspected by the irradiation apparatus and reflected by the surface along a second emission direction.

[0075] According to the present invention, the (second) irradiation direction and the second emission direction are substantially opposite. In this embodiment, a very special form of surface illumination and detection is employed, which is unknown in the prior art.

[0076] Generally, radiation is preferably light, especially light in the visible light wavelength range. Radiation is preferably white light, especially standard white light.

[0077] In a preferred embodiment, the irradiation device and / or radiation device has at least one or more LEDs, particularly white LEDs. Preferably, only one light source is provided, particularly an LED-type light source, and preferably, an aperture associated with this light source is provided. This aperture may preferably be located within the focal length of the lens. In this case, the light source can be considered as a point light source.

[0078] In another preferred embodiment, the illumination device has a light source, an aperture or stop, and preferably a lens. These elements are preferably arranged in front of the beam splitter along the illumination direction, particularly in front of the aforementioned beam splitter (or (beam) deflection device).

[0079] Particularly preferably, an objective lens, particularly a telecentric objective lens, is positioned between the surface (and / or the measuring plane containing the surface under inspection and / or the measuring plane on which the surface under inspection is to be arranged for inspection) and the testing equipment. Preferably, the (telecentric) objective lens should be positioned closer to the testing equipment than the surface under inspection. Preferably, the objective lens has at least two, and more preferably at least three, lenses.

[0080] Optical inspection equipment is preferably designed in the manner described above.

[0081] The present invention also relates to a method for detecting optical surface properties (of a surface to be inspected), the method comprising at least the following steps: Use irradiation equipment to irradiate the surface to be inspected; A radiation detection device records a spatially resolved image of radiation emitted (especially reflected) by a surface in response to radiation irradiated (by an irradiation device), and the radiation detection device has a maximum detection area for detecting (especially spatially resolved) radiation reaching that area. The radiation detection device is preferably a device suitable for spatially resolving the detection of radiation impacted by an object. Specifically, the radiation detection device is a camera; Determine at least one effective area value characterizing a region within a predetermined and / or predeterminable measurement region located within the maximum detection region, wherein emitted (especially reflected) radiation arrives at the region in a predetermined and / or predeterminable manner, particularly relating to luminance and / or color values. Preferably, exactly one effective area value is determined. However, it is also conceivable to determine two, three, or more effective area values; and Determine at least one ratio value (V) that characterizes the relationship between the area value (W) and a predetermined maximum value (M). Preferably, exactly one ratio value is determined. However, it is also conceivable to determine two, three, or more ratio values.

[0082] As mentioned above, due to insufficient surface curvature or size, not all radiation incident on the surface will be reflected back to the radiation detection device, or not all radiation emitted by the irradiation device will hit the surface under inspection.

[0083] As mentioned above, the ratio value is a fill factor that can depend on the curvature of the surface, the size of the object, or the gloss or matte areas of the surface.

[0084] The maximum detection area is especially the measurement area that characterizes the corresponding detection device (such as a CCD chip or camera).

[0085] The predetermined and / or predeterminable measurement area is a portion of the maximum measurement area, which is produced particularly by oblique illumination (from the radiating device (especially the first radiating device) onto the surface). For example, if the radiating device has a rectangular aperture, this rectangular aperture will be imaged on the surface when radiation is incident in a perpendicular direction. The radiation detection device will detect this elliptical spot. In other words, in this case, the radiation detection device detects an elliptical irradiated local area on the surface under test, which is also imaged as an elliptical area on the measurement surface of the radiation detection device (particularly due to the optical arrangement of the radiation detection device, such that the path of the radiation beam emitted perpendicularly from the surface under test or the measurement plane is parallel to and / or along the detection direction and / or optical axis of the radiation detection device).

[0086] The aperture preferably has a rectangular cross-section. The aspect ratio of the aperture is preferably 5:1 to 2:1. Although it is a rectangular aperture, the measurement point will appear elliptical at the relevant observation distance.

[0087] Radiation detection equipment cannot observe or detect the measurement point produced by the first radiation device on the surface under test (at least in the case of reflective surfaces).

[0088] Preferably, the measurements performed by the irradiation device and the radiation detection device on one hand are performed sequentially with the measurements performed by the first radiation device and the first radiation detection device on the other hand.

[0089] If the radiating device (especially if it is the first radiating device) illuminates the surface at an angle, an elliptical image will be produced on the surface. The radiation detection device will then detect this elliptical image accordingly. Therefore, this elliptical image represents a predetermined and / or predeterminable measurement area, particularly depending on parameters such as the illumination angle and aperture of the radiating device. However, these parameters are preferably fixed and / or device-specific.

[0090] In other words, when the (first) radiating device irradiates the surface at an angle, an elliptical portion of the surface is formed. If only this (irradiated) local area is considered, then when the radiation is irradiated only by the irradiating device (using the above-described optical arrangement of the irradiating device and / or the radiation detection device), this (irradiated) local area of ​​the surface corresponds to the elliptical area on the detection surface of the radiation detection device.

[0091] Preferably, the predetermined and / or predeterminable measurement area depends on at least one parameter, which depends on the irradiation of the device by radiation, particularly selected from a set of parameters including the irradiation angle, the aperture shape of the irradiation device, the light source of the irradiation device, etc. Preferably, these parameters are specific and / or fixed parameters for the device used.

[0092] The effective area value is still affected by factors such as the curvature or size of the surface under inspection. The curvature of the surface can mean that not all radiation reflected from it reaches the measurement area. For example, if a radiation detection device illuminates a fully illuminated ellipse on a flat surface, this ellipse will not be fully illuminated on a curved surface. The same applies if the surface under inspection is so small that not all radiation passing through the aperture of the radiation detection device reaches it. Radiation not only illuminates the object but also its surroundings.

[0093] For planar samples, the illumination and observation points are at most elliptical. For curved surfaces (non-planar), the effective shape of the light spot depends on the surface morphology.

[0094] This effective area value can be determined, in particular, by using a thresholding method, as will be described in more detail below. For example, the radiant intensity value illuminating the pixels can be specified to classify these pixels as either illuminated or unilluminated. In this way, a binary distinction can be made between illuminated and unilluminated areas, or which area elements contribute to the measurement value can be distinguished.

[0095] In another method for detecting the optical properties of a surface according to the invention, a first radiation device emits radiation along a first irradiation direction onto the surface to be tested, and a first radiation detector device detects the radiation emitted by the first radiation device onto the surface to be tested and emitted (especially reflected) by the surface along the emission direction (R1').

[0096] In addition, the irradiation device irradiates the surface under test with radiation along a second irradiation direction, and the radiation detection device detects the radiation irradiated by the irradiation device onto the surface under test and emitted (especially reflected) by the surface along the second emission direction. These measurements can be performed simultaneously (for reflective surfaces) or delayed (for non-reflective surfaces).

[0097] According to the present invention, the second irradiation direction and the second emission direction are substantially opposite.

[0098] In another method for optically inspecting a surface according to the invention, an irradiation device irradiates the surface to be inspected along an irradiation direction, and a radiation detection device detects the radiation irradiated by the irradiation device onto the surface to be inspected and reflected by the surface along a second emission direction, preferably recording a spatially resolved image of the surface.

[0099] According to the present invention, the second irradiation direction and the second emission direction are substantially opposite.

[0100] In an advantageous method, a telecentric optical system, particularly a telecentric objective lens, is used to detect radiation, preferably with the telecentric optical system positioned between the surface and the radiation detection device.

[0101] In another advantageous method, the radiation detection device records a spatially resolved image of the surface under inspection. For this purpose, a camera or CCD chip is used, preferably imaged on the camera or CCD chip. Preferably, telecentric optics are used to image the surface under inspection onto the radiation detection device.

[0102] In another advantageous method, the surface to be inspected is a curved surface, the surface of a small component, or a surface that has both glossy and matte (or matte reflective and / or scattering) areas.

[0103] If the surface is that of a small component, it is preferable to mount the small component on a carrier that is smaller than the component itself on the observation or measurement plane. This prevents radiation reflected from the carrier (which would tamper with the measurement results) from reaching the radiation detection equipment (and / or radiation detector equipment).

[0104] The environment of the carrier is preferably selected so that unwanted reflections do not enter the detector or radiation detection equipment, for example, a thick matte surface or a light trap.

[0105] In another preferred method, the predetermined and / or predeterminable measurement surface is predetermined by a first radiation device (in particular, a radiation device referred to above as the first radiation device), which is adapted to irradiate the surface to be inspected in a predetermined direction, which is in particular a direction deviating from the vertical direction, the (first) irradiation direction.

[0106] In this method, as described above, a predetermined and / or predeterminable measurement area is determined by the fact that radiation strikes the surface at an angle, particularly by recording the radiation reflected from the surface.

[0107] The predetermined and / or predeterminable measurement area is preferably the area that the first radiation device can irradiate to the maximum extent, and / or the area of ​​the surface to be inspected (especially a flat or smooth surface).

[0108] Preferably, the radiation reaching the surface and / or radiation cross section of the first radiation device is limited by a radiation limiting element, particularly the aperture.

[0109] Specifically, this radiation is applied to the surface at a predetermined angle relative to the vertical direction, such as 45° or 60° (or possibly 20°, 75° or 85°).

[0110] The camera or radiation detection equipment can only virtually know the gloss measurement point (it cannot actually measure the gloss measurement point). Predefined and / or predefined measurement areas are retrieved from the equipment's storage to determine the ratio value or fill factor.

[0111] In another preferred method, the first radiation device is suitable for use in conjunction with a radiation detector device to perform gloss measurement. The radiation detector device can be a radiation detector device that records a spatially resolved image of the radiation incident upon it. However, it can also be a radiation detector device whose output value characterizes the (integral) intensity of the radiation incident upon it.

[0112] In a preferred method, a predetermined and / or predeterminable measurement area characterizes the area size of the radiation detection device assembly, where radiation emitted by the (first) radiation device reaches when using a plane that emits radiation.

[0113] In another preferred method, a predetermined and / or predeterminable measurement area characterizes the area size of the radiation detection device assembly, which is generated when radiation emitted by the (first) radiation device is completely reflected to the (first) radiation detector device.

[0114] When considering a predetermined and / or predeterminable measurement area, it is therefore specifically assumed that all radiation emitted by the radiation device (especially radiation emitted through openings in the device housing) reaches the surface, and all radiation reflected from the surface also reaches the radiation detection device. Therefore, in this case, it is preferable to completely image the surface to be inspected onto the radiation detection device.

[0115] In another preferred method, the measurement area characterizes the size (and / or arrangement) of the area reached by radiation emitted from the first radiation device within the maximum detection area when using a plane as the surface to be inspected.

[0116] In another preferred method, the measurement area characterizes the surface size formed when the radiation emitted by the first radiation device is completely reflected to the radiation detector device.

[0117] In another preferred method, radiation is incident on the surface to be inspected through an opening in the housing, and radiation emitted from the surface to be inspected passes through the opening. Preferably, radiation emitted from the irradiation device that does not pass through the opening is ignored.

[0118] Particularly preferably, the opening is located directly above or very close to the surface to be inspected. "Very small distance" is understood to mean that the distance is less than one-third of the distance between the first radiating device and the opening, preferably less than one-fifth, more preferably less than one-seventh, and more preferably less than one-tenth.

[0119] Preferably, radiation emitted by the irradiation device that does not pass through the opening is absorbed by the walls of the housing (especially the inner wall).

[0120] In another preferred method, the maximum value represents the area that the opening maps to on the radiation detection device.

[0121] In the “ideal” region, the opening is perfectly mapped onto the radiation detection device. This is the maximum illuminateable area, and therefore the maximum value. Therefore, this paper assumes that all radiation passing through the opening is precisely reflected by the surface to reach the radiation detection device, such that the surface is ideally mapped onto the detection device.

[0122] The maximum value is preferably the opening area.

[0123] In another preferred method, a threshold method is used to determine the area and / or ratio values. This means that a threshold or limit is used as the basis for considering whether certain pixels or pixel areas of illumination or lighting of the image recording device should be irradiated. This allows determination of whether each irradiated pixel of the radiation detection device still belongs to the illuminated area.

[0124] In another preferred method, a thresholding method is used to determine the brightness distribution (and / or color distribution) in the image recorded by the radiation detection device, and / or to evaluate the brightness distribution (and / or color distribution).

[0125] Therefore, an optimal decision is made regarding which pixels are still included in the values ​​that determine the area value and which pixels are not.

[0126] A threshold value is preferably determined. Intensity values ​​higher than this threshold are assessed as belonging to the region, while intensity values ​​lower than this threshold are not considered to belong to the region.

[0127] The fill factor can be determined in several ways. The simplest algorithm is the thresholding method described above for the cross-section of brightness distribution in the image.

[0128] In another preferred method, a standard surface is used to determine the threshold for the thresholding method.

[0129] Therefore, glass standards with different radii of curvature and gloss values ​​are preferably selected. A linear relationship between fill factors of 0 and 1 is preferably used as a guiding principle for this.

[0130] In another preferred method, the fill factor is mathematically correlated with the gloss value. Preferably, a mathematical relationship is established between the fill factor and the gloss value (especially the measured value), for example, by dividing (or multiplying) the gloss value, particularly for evaluating curved or small surfaces.

[0131] These assessments can also take into account the corresponding gloss angle, especially the angle size when recording gloss.

[0132] In another preferred method, the surface to be inspected is curved. In yet another preferred method, the surface to be inspected is smaller than the area illuminated by the irradiation device through an opening and / or the measurement area predetermined and / or illuminated by the first radiation device.

[0133] In another preferred method, the surface to be inspected has both glossy and matte surface areas.

[0134] In another advantageous method, the gloss value of such a surface is determined using a ratio value obtained for an ideal surface, which corresponds to the measuring surface in terms of optical properties, but the ideal surface is flat and at least as large as the area that the irradiation device can irradiate through the opening.

[0135] Thus, it is preferable to convert data determined for an actual surface into data formed from a plane. In particular, this can, for example, determine the gloss value of the surface under test, which is derived from a (conventional) gloss measurement of the surface having a planar rather than curved shape (and therefore, the same optical properties in other respects).

[0136] In another preferred method, the irradiation device irradiates the surface substantially perpendicularly, and the radiation detection device detects the radiation emitted (and particularly reflected) from the surface substantially perpendicular to it. The perpendicularity assumption is based on an ideal plane. Preferably, radiation is also emitted perpendicular to the cross-section of the aforementioned housing opening.

[0137] In another preferred method, a telecentric objective lens is used to image the surface onto a radiation detection device. Attached Figure Description

[0138] Further advantages and implementation methods are apparent from the accompanying drawings: In the attached diagram: Figure 1a A structure for gloss measurement according to the prior art is shown, which is derived from EN ISO 2813; Figure 1b It shows the use of according to Figure 1a The recording was performed by a device in which the surface is reflective; Figure 2a and Figure 2b The diagram illustrates a structure known in the prior art and a structure for detecting surface properties according to a preferred embodiment of the present invention; Figures 3a to 3d It shows the use of according to Figure 2a and Figure 2b The four measurement results obtained from the structure are represented; Figure 4 The device according to the invention is shown in a first application; Figure 5 An illustration of the device according to the invention in a second application is shown; Figure 6 A representation of how direct-view measurement is implemented is shown; Figure 7 This shows a first representation of determining the fill factor; Figure 8a and Figure 8b A diagram illustrating surface measurement is provided. Figure 9 A general representation for determining the properties of a glossy surface is shown; Figure 10 A schematic diagram showing the measurement results for a matte surface is provided. Figure 11 Another schematic diagram of another method step of the present invention is shown; Figure 12 This shows a representation of the gloss value determined from the fill factor; Figure 13 A representation of a telecentric optical device is shown; Figure 14 It shows Figure 13 A cross-sectional view of the telecentric optical device shown; Figure 15 Another representation of the telecentric optics is shown in the illustrated dimensions; and Figure 16a and Figure 16b Two illustrations show how the method can be applied to surfaces with different gloss levels. Detailed Implementation

[0139] Figure 1a The structure for detecting the gloss properties of surface and / or coating 10 is schematically shown. A light source 120 is provided that illuminates surface 10 at an illumination angle a1 (relative to the central plane M).

[0140] A lens 122 is also provided, which aligns the light rays or radiation in parallel. The surface 10 reflects the light rays, which pass through the second lens 124 at an angle α2 and reach the radiation detector device through the aperture 126, where the image 130 is displayed. Here, α2 represents the angle of radiation reflected from the surface, or the angle between the central plane M and the beam path of the radiation emitted (especially reflected) from the surface 10.

[0141] Figure 1b An image recorded above a reflective surface in this manner is shown. Therefore, the image displays the signal from the sensor in the conventional setup shown in Figure 1. However, this recording method is not suitable for curved surfaces or surfaces with varying ratios of gloss and matte finishes, nor for very small surfaces.

[0142] Figure 2a and Figure 2b Two basic methods for surface observation are shown. Figure 2a It shows traditional dark-field lighting, while Figure 2b Direct illumination proposed in the context of this invention is illustrated. Figure 2a In the dark field illumination shown, two radiating devices 142 and 144 illuminate the surface at a predetermined angle (45° in this example), and the image recording device 146 records the light scattered by the surface (but preferably not the reflected light).

[0143] like Figure 2b As shown, the light source 144 illuminates the surface through the beam splitter device 148, and the light reflected from the surface reaches the image detection device 146.

[0144] Figures 3a to 3d Four representations of the recorded surface are shown. Figure 3a and Figure 3c The images in the image were recorded using the dark-field method. Figure 3b and Figure 3d The images in the image were recorded using the direct illumination method described above.

[0145] Figure 3a and Figure 3b The image shows a black glass surface with scratches (with a gloss value of 95 GU (gloss unit) when measured at a 60° measurement angle).

[0146] Figure 3c and Figure 3d The structured surface is shown. The gloss value at a 60° angle is 69.3 GU.

[0147] Figure 4An apparatus for detecting surface characteristics according to a first embodiment of the present invention is shown. Reference numeral 2 refers to a first radiation device that irradiates radiation (particularly light) onto the surface 10 to be inspected along the irradiation direction R1. It can be seen that the surface is curved, causing the radiation emitted along the direction R1' to diffuse or diverge. Thus, not all radiation reflected from the surface 10 reaches the first radiation detector device 4.

[0148] Reference number 20 generally refers to an optical inspection device for a surface. As described in more detail below, the device emits radiation in direction R2 (i.e., the direction perpendicular to surface 10) and also detects radiation from surface 10 in the opposite direction to R2 (i.e., direction R2').

[0149] Figure 5 It shows the relationship with Figure 4 The devices described herein are similar but have different applications. Here, the surface to be inspected is a small workpiece, such as a microchip mounted on bracket 11 or a button on an electronic device. The cross-section of bracket 11 is significantly smaller than that of surface 10 itself. This prevents radiation reflected from bracket 11 from reaching radiation detector device 4. An optical inspection device, generally designated 20, is also provided here.

[0150] In this application (and preferably according to the invention), the area or geometric extension (in at least one direction) of the surface 10 of the small workpiece to be inspected is smaller than the area or geometric extension of the measurement area (predetermined by the device). This measurement area is particularly derived from the area within the measurement plane that can be irradiated or illuminated by the first radiation device 2.

[0151] exist Figure 5 In the application shown, since the (geometric) size of the surface 10 to be inspected is relatively small compared to the measurement area, not all of the radiation emitted by the first radiation device 2 or the radiation emitted along the direction of the measurement surface (or the radiation irradiated onto the measurement surface or measurement plane along the irradiation direction R1) can reach the surface 10 to be inspected.

[0152] As shown in the upper and lower beam paths emitted from the first radiation device, due to the small size of the surface 10 under test, some radiation emitted along the direction of the measurement surface is reflected off the surface under test and does not reach the first radiation detector device.

[0153] For example, performing a (conventional) (gloss) measurement on this smaller surface 10, without (incorrect) correction for the surface size, compared to a surface that fills the measurement area, will yield a lower (gloss) value. This is because only the portion of the radiation incident on the measurement surface corresponding to the smaller surface contributes to the (gloss) value measured by the radiation detector device 4. Therefore, the (gloss) value measured by the radiation detector device 4 is lower than the value obtained for the same surface under inspection, which...Figure 5 The only difference in the surface shown is that it fills the entire measurement area.

[0154] The optical inspection device 20 proposed in this paper is preferably used to adapt the (gloss) value measured by the radiation inspection device 4 to the curvature of the surface 10 under inspection (see...). Figure 4 ) and / or the geometric extension of the surface to be inspected (see Figure 5 This allows for the acquisition of a (measured) (gloss) value that is independent of the curvature and / or geometric extension of the surface 10 under inspection.

[0155] To this end, the optical inspection device 20 specifically determines whether the surface to be inspected 10 has any curvature within the relevant measurement range (i.e., the measurement area) of the device, and / or whether the surface to be inspected 10 extends completely into the entire measurement range or the entire measurement area of ​​the device.

[0156] If the surface to be inspected 10 is curved within the measurement area or if the surface to be inspected 10 does not extend completely into the measurement area, the optical inspection device determines a ratio value V, which serves as a correction value for the measurement value obtained by the radiation inspection device 4.

[0157] Figure 6 An optical inspection device 20 is shown. This optical inspection device has a telecentric objective lens device with an overall number of 30. Reference number 24 indicates a (optical) radiation inspection device, such as a camera or CCD chip.

[0158] Reference numeral 32 indicates a light source, specifically, but not limited to, one or more LEDs, and reference numeral 34 indicates an aperture. Light emitted from the light source 32 is directed onto the surface 10 to be inspected (along direction R2) via lens 36 and beam splitter 12. Radiation reflected from surface 10 is reflected along direction R2' to a radiation detection device, specifically an image detection device 24 or a camera. This arrangement produces (approximately) parallel light for sample illumination.

[0159] The recorded images can be significantly improved by using the telecentric objective device described in detail below.

[0160] Figure 7 A diagram is shown illustrating the determination of the aforementioned ratio value or fill factor. Here, the reference symbol M represents the maximum measurement range of the first radiation detector device 4 (e.g., a measurement arrangement including the first radiation device 2 and the first radiation detector device 4, for example, for measuring gloss), such as a gloss detector.

[0161] The reference symbol K represents the (maximum) measurement area of ​​the radiation detection device 24 (of the irradiation device 22 or the optical detection device 20), which can be provided by an image recording device or a camera. Therefore, K can be given, for example, by the sensor area of ​​the CCD chip of the irradiation device 22 or the optical detection device 20 (especially for measurement).

[0162] The reference symbol W represents the effective measurement area of ​​the gloss detector, for example, when detecting a curved surface. As mentioned above, this area W is preferably determined from the image. The ratio of W to M is the fill factor V.

[0163] Therefore, the fill factor is: Fill factor = effective area W / maximum area M.

[0164] Therefore, within the scope of this invention, it is proposed to combine or integrate conventional gloss measurement with direct observation from above. With this structure as shown above, surface regions that contribute to gloss (particularly those contributing to conventional gloss measurement) can be identified, and the effective area of ​​these regions can be determined.

[0165] These areas can be ranges on curved surfaces, such as those perpendicular or parallel to the aforementioned measurement axes. The surface of an object smaller than the actual measurement point can also be measured during gloss measurement. As mentioned above, these objects must be placed on a suitable support below the measurement aperture. Preferably, reflected light from the support device should be prevented from entering the detector.

[0166] Another measurement option is to measure surfaces that have both glossy and matte areas. Using these surfaces, matte and glossy areas can be distinguished and calculated separately.

[0167] Figure 8a and Figure 8b Two examples of measurements taken on surface 10 are shown. Figure 8a and Figure 8b In the examples shown, the surface to be inspected is, in every case, the outer surface of a (straight) (circular) cylinder. The outer surface of the cylinder appears to be straight along the axial direction MO of the cylinder. Figure 8a As shown, the outer surface under test is curved in the direction MO perpendicular to the axis of the cylinder (located within the measurement area and / or measurement plane). Therefore, the outer surface 10 under test has curvature in one direction of the measurement plane (or measurement area), while it is flat in the direction perpendicular to that direction. This curvature can be, for example, perpendicular to the radius of curvature or along the axis of the cylinder (i.e., along...). Figure 8b Measurements can be taken along the direction of the middle arrow MO, or parallel to the radius of curvature or perpendicular to the cylinder axis (and along the measurement area or measurement plane), i.e., along... Figure 8bThe measurement is performed in the direction of the middle arrow MO. Depending on the measurement setup, drastically different images can be expected.

[0168] Figure 9 The diagram shows representations of different surfaces and corresponding images. The top row shows dark-field images. Dark-field images cannot reproduce the curvature of a surface. Bright spots represent dust particles on the surface. The middle row shows images taken directly, and the bottom row shows a diagram of the fill factor. Here, the surface under examination is a glossy surface.

[0169] exist Figure 9 In this study, all images were taken at the scattering angle, i.e., gloss was measured.

[0170] The first image in the top row shows a planar image record. The image in the second column of the first row shows a recorded image of the surface of a cylinder with a radius of curvature of 200 mm in the vertical direction (particularly a gloss measurement relative to the axis of the cylinder). In other words, by utilizing this alignment of the device 1 with respect to the surface of the cylinder under test, the irradiation direction R1 and / or emission direction R1' of the (first) radiating device 2 are substantially perpendicular to the axis of the cylinder.

[0171] The top row, third column also shows an image of a surface, in this example the outer surface of a cylinder with a radius of curvature of 200 mm, but in this example the image was taken along the radius of curvature. Specifically, the surface under test in the third column is a surface from the second column. However, compared to the second column, the surface under test is rotated 90° relative to the device before measurement. In other words, using the alignment of device 1 with the outer surface of the cylinder under test as shown in Figure 3, the irradiation direction R1 and / or emission direction R1' of the (first) radiation device 2 are substantially parallel to the axis of the cylinder.

[0172] The images in the top right columns show corresponding images of the surface of a cylinder with a radius of curvature of 50 mm, one along the vertical direction and the other along the axial direction.

[0173] The bottom row shows a representation from which the fill factor for each case can be derived and explained.

[0174] and Figure 7 Similarly, reference symbol M denotes the predetermined (maximum) measurement area in each case. This area is predetermined by device 1, particularly by the arrangement and alignment (irradiation direction R1) of the (first) radiating device 2 and the arrangement and alignment (emission direction R1') of the (first) radiating detector device 4, and if necessary, by optical elements (e.g., one or more apertures) in the beam path between the (first) radiating device 2 and the (first) radiating detector device 4.

[0175] For a plane (column 1), the entire surface 10 to be inspected (shown in M) contributes to the emission of radiation from the (first) radiation device 2 along the direction of the (first) radiation detector device 4.

[0176] Reference symbol W represents an image of the surface 10 to be inspected, which is illuminated by the (first) radiation device 2 and contributes to emitting radiation along the emission direction R1' so that the (first) radiation detector device 4 can detect the emitted radiation. For the plane to be inspected, this area corresponds to M, because the emission direction R1' at each point on the surface to be inspected is opposite to the illumination direction (relative to the measurement plane).

[0177] For cylindrical surfaces, as shown in columns 2-5, dark stripes can be seen on both sides of the central bright stripe in the orthographic image. These dark stripes appear in the orthographic image because the corresponding surface areas are tilted relative to the illumination direction R2, causing radiation emitted by the illumination device 22 along the illumination direction R2 and striking these surface areas to be emitted or reflected along direction R2' to the radiation detection device 24, but rather along a different emission direction. Therefore, the corresponding area of ​​the detection surface (K) of the radiation detection device 24 remains dark.

[0178] The situation is similar for surface regions on the surface under test that are inclined relative to the measurement plane (or measurement area) (due to the curvature of the surface under test). In this case, the (first) radiation device irradiates these surfaces with radiation along the irradiation direction R1 and emits radiation in response to the irradiated radiation and the (first) radiation detector device. Similarly, the radiation irradiated onto these surface regions on the surface under test that are inclined relative to the measurement plane is emitted and / or reflected in a direction different from the emission direction R1' due to the inclination of these surface regions, making the emitted radiation undetectable by the (first) radiation detector device 4. Therefore, these (inclined) surface regions do not contribute to the measured values ​​(e.g., gloss values) determined by the (first) radiation detector device 4.

[0179] Starting from the (maximum) measurement area M, only the area marked W in the last row (due to the inclination relative to the measurement plane or measurement area) contributes to the measurement value determined by the (first) radiation detector device.

[0180] The regions W in the last two columns are significantly narrower than the surfaces detected in the second and third columns because the surfaces detected in the last two columns have a greater radius of curvature (50 mm) than those detected in the second and third columns, which have a significantly larger radius of curvature (200 mm). The smaller or larger radius of curvature of the corresponding cylindrical surface design means that only the correspondingly narrower surface region has a sufficiently small tilt relative to the measurement plane or measurement area to emit or reflect radiation in the emission direction R1', thus enabling it to be detected by the (first) radiation detector device 4.

[0181] This further illustrates the effect of rotating the surface under inspection by 90° within the measurement plane on the orientation of the surface under inspection.

[0182] In the alignment methods shown in the second and fourth columns, the first surface direction (along the measurement plane) of the surface under inspection is curved and perpendicular to the irradiation direction R1. The second surface direction differs from the first surface direction, is perpendicular to the first surface direction, and also lies within the measurement plane, extending particularly into the cross-sections passing through the measurement plane and / or the surface under inspection, the (first) irradiation device 2, and the (first) irradiation detector device 4. The surface under inspection has a non-curved (i.e., straight) surface profile along the second surface direction. The first and second surface directions refer to a coordinate system about the surface under inspection, preferably within the measurement plane.

[0183] In the alignment methods shown in columns three and five, the surface under test is rotated 90° (relative to a rotation axis perpendicular to the measurement plane). In this alignment method, the aforementioned second surface direction (along which the surface under test has a non-curved surface profile) is perpendicular to the irradiation direction R1 or perpendicular to the cross-section passing through the measurement plane and / or the surface under test, the (first) irradiation device 2, and the (first) radiation detector device 4. In this alignment method, compared to the alignment method shown in column two (with a sufficiently small tilt), the surface area of ​​the surface under test covered by the (maximum) measurement area M is larger, so that even if the surface is tilted, radiation irradiated from the irradiation device to the corresponding surface area can be emitted or reflected to the (first) radiation detector device and thus detected.

[0184] Therefore, the fill factor of the alignment method shown in the third column is greater than the fill factor of the alignment method of the surface under inspection shown in the second column.

[0185] Figure 10 A similar image recording is shown, this time for a matte surface, in which illumination is performed once perpendicular to the radius of curvature and once parallel to the radius of curvature.

[0186] The dark-field image shown in the first row here also fails to reproduce the surface curvature. Bright spots represent dust particles on the surface.

[0187] It can be seen that the stripes produced by images of surfaces with larger radii of curvature are significantly wider than those produced by images of surfaces with smaller radii of curvature.

[0188] The larger the radius of curvature, the smoother the surface; the smaller the radius of curvature, the more curved the surface.

[0189] The bottom row shows the fill factor representation when recording each surface. The fill factor is 1 when the ellipse is completely filled. It can be seen that the filled area is significantly reduced in the vertical images (second and fourth columns), which is expected because the stripes extend perpendicular to the major axis.

[0190] It can also be seen that, as expected, the contrast of matte surfaces is significantly lower than that of glossy surfaces.

[0191] Figure 11 Another illustration showing the measurement results is provided. Here, the grayscale image is simplified to a binary image, that is, an image that only displays black or white pixels.

[0192] Figure 12 A schematic diagram illustrating the determination or calculation of the threshold factor is shown. The fill factor is plotted on the x-axis, and the corresponding gloss value (measured here at a gloss angle of 60°) is plotted on the y-axis. As mentioned above, the fill factor can be determined in several ways.

[0193] The simplest algorithm is a thresholding method for the cross-section of the image brightness distribution. A threshold is then preferably taught. For this, glass standards with different radii of curvature and gloss values ​​are preferably selected. A linear relationship between fill factors 0 and 1 is preferably used as a guiding principle for this.

[0194] Figure 13 and Figure 14 An overall view of the telecentric objective lens 30 is shown. Radiation emitted or reflected from the surface under inspection passes through this objective lens and reaches the inspection device.

[0195] Reference numeral 50 indicates the first lens, and reference numeral 51 indicates the second lens. These two lenses are preferably used together to form an achromatic lens. Reference numeral 53 indicates the third lens, which is preferably a biconvex lens.

[0196] Preferably, the distance between the first lens 50 and the second lens 51 (which refers to the distance between the first surface of the first lens facing the second lens and the 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.

[0197] Preferably, the distance between the first lens 50 and the second lens 51 (which refers to the distance between the first surface of the first lens facing the second lens and the first surface of the second lens facing the first lens 50) is less than 50 mm, preferably less than 45 mm, preferably greater than 40 mm, and preferably greater than 35 mm.

[0198] Preferably, the maximum thickness of the first lens 50 is greater than 3 mm, more preferably greater than 4 mm. Preferably, the maximum thickness of the first lens 50 is less than 7 mm, more preferably less than 6 mm, more preferably less than 5 mm, and especially preferably less than 4.5 mm.

[0199] Preferably, the diameter of the first lens is greater than 10 mm, more preferably greater than 15 mm, and especially preferably greater than 20 mm. Preferably, the diameter of the first lens is less than 40 mm, more preferably less than 35 mm, and especially preferably less than 30 mm.

[0200] Preferably, the maximum thickness of the second lens 51 is greater than 3 mm, more preferably greater than 4 mm, and even more preferably greater than 5 mm. Preferably, the thickness of the second lens 51 is less than 9 mm, more preferably less than 8 mm, and especially preferably less than 7 mm.

[0201] Preferably, the diameter of the second lens is greater than 5 mm, more preferably greater than 6 mm, more preferably greater than 7 mm, and especially more preferably greater than 8 mm. Preferably, the diameter of the second lens 51 is less than 12 mm, more preferably less than 11 mm, more preferably less than 10 mm, and especially preferably less than 9 mm.

[0202] The applicant reserves the right to claim protection for the telecentric objective described herein and its application in the device described herein.

[0203] Reference number 54 indicates the bracket or mounting bracket for lens 50; reference number 56 indicates the spacer ring; and reference number 55 indicates the cover ring.

[0204] Reference numeral 64 indicates an insert adapter that is secured to the lens assemblies of lenses 50 and 51 by a threaded pin. Reference numeral 58 indicates a counter ring.

[0205] Reference number 65 indicates the aperture frame. Reference number 62 indicates the mounting bracket, and reference number 68 indicates the adapter (particularly for testing equipment).

[0206] Figure 15 Another representation of the telecentric objective lens is shown. It can be seen that the distance between the surface under test 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. Preferably, the distance between the surface under test and the first lens is less than 100 mm, preferably less than 90 mm, preferably less than 80 mm, and particularly preferably less than 70 mm.

[0207] The distance between the second lens and the image recording device (e.g., a CCD chip) is preferably greater than 10 mm, preferably greater than 12 mm, preferably greater than 14 mm, and preferably greater than 16 mm.

[0208] The distance between the second lens and the image recording device (e.g., a CCD chip) is preferably less than 30 mm, preferably less than 25 mm, preferably greater than 20 mm, and preferably greater than 18 mm.

[0209] Figure 16a andFigure 16b A flat sample with a glossy area A and a matte area B is shown. The elliptical area E represents the conventional observation point or the predetermined (maximum) measurement area M.

[0210] In the case shown, there are two valid regions. The first region is the intersection of the ellipse and the bright area A, and the second region is the intersection of the ellipse and the dark area B.

[0211] The conventional gloss value is preferably a linear combination of the two surfaces. This means that the conventional gloss values ​​of A and B can be calculated from the surface distribution.

[0212] Regarding area A 总 The conventional gloss value G of the entire (maximum) measurement area M (represented here by an ellipse E) 总 This calculation is obtained specifically from the conventional gloss value G1 of the gray sub-region within ellipse E and the area A1 of sub-region B, as well as the conventional gloss value G2 of region A within ellipse E and the area A2 of region A: G 总 = G1 A1 / A 总 + G2 A2 / A 总 .

[0213] If one of the two values ​​G1 and G2 is known, for example by measuring that only one type of point appears on the sample, the above equation can be solved.

[0214] Alternatively, the ratio R of G1 and G2 can be (approximately) determined from the luminance values ​​I1 and I2 in the camera image or radiation detection device 24: R = I1 / I2 = G1 / G2.

[0215] This relationship can be used to solve the above equation.

[0216] For example, the applicant measured the conventional gloss value of the sample plate edge as G2 = 100 GU, and the area ratio as A2 / A 总 = 2 / 3 and I2 = 325110, and the area ratio A1 / A 总 = 1 / 3 and I1 = 6046. G1 is determined by the following formula: G1 = R G2 = 0.019 G2 = 1.9GU. Thus, G 总 = 1.9 GU 0.33 + 100 GU 0.66 = 66.6 GU.

[0217] Using conventional equipment, the gloss value was measured at 60° as G. 总 = 64.8 GU.

[0218] The apparatus according to the invention preferably includes conventional gloss measurement and camera observation within the housing.

[0219] The device can be a handheld device or a user-portable device. In addition to handheld devices, the device can also be applicable to various robotic systems.

[0220] These robotic systems can include, for example, multi-axis robots, inline systems, and / or XY stages. In these cases, these devices can perform measurements at a distance of 3 to 5 mm from the surface. This means that both convex and concave surfaces are feasible. It is worth noting that for conventional gloss measurements, the measurement plane or range of the device should be maintained. Measurements using robotic equipment are given at a certain distance from the ground.

[0221] As mentioned above, the effective measurement range does not have to be continuous. Multiple (especially horizontal) surface elements can also exist.

[0222] Prioritize situations where there are no shadows obstructing the view from above. Shadows can cause problems for traditional measurements at large angles.

[0223] In production, a telecentric camera can be used to detect elliptical observation points used for conventional gloss measurements (when using a (flat) matte surface). For this purpose, a light source can be positioned at the location of the photoelectric element. Preferably, feature data (e.g., a predetermined measurement area) is stored in the device's storage (for image evaluation).

[0224] The applicant reserves the right to declare all features disclosed in the application documents as essential to the present invention, provided that such features are novel relative to the prior art, whether as a single feature or a combination of features. It should also be noted that the figures also depict features that may be advantageous in themselves. Those skilled in the art will readily recognize that a particular feature described in the figure may be advantageous even without employing other features from that figure. Furthermore, those skilled in the art will recognize that advantages may also arise from a single figure or a combination of several features shown in different figures.

Claims

1. A method for detecting optical surface properties of a surface (10) to be inspected, comprising the following steps: The irradiation device (22) irradiates the surface to be inspected (10) with radiation; The radiation detection device records a spatially resolved image of the radiation emitted and, in particular, reflected by the surface (10) in response to irradiated radiation, the radiation detection device having a maximum detection area (K) for detecting radiation reaching the area; Determine at least one effective area value (W) of a region located within a predetermined and / or predeterminable measurement region (M) within the maximum detection region (K), wherein emitted, in particular reflected radiation reaches the region in a predetermined and / or predeterminable manner, particularly with respect to luminance and / or color values; as well as Determine at least one ratio value (V) that characterizes the relationship between the effective area value (W) and the measurement area (M).

2. The method according to claim 1, characterized in that, The predetermined and / or predeterminable measurement area is predetermined by a first radiation device (2), which is adapted to irradiate the surface to be inspected with radiation along a predetermined first irradiation direction (R1), particularly deviating from the vertical direction.

3. The method according to at least one of the preceding claims, characterized in that, The first radiation device (2) is suitable for performing gloss measurement in conjunction with the first radiation detector device (4).

4. The method according to at least one of the preceding claims, characterized in that, The measurement area (M) characterizes the size of the area reached by radiation emitted from the first radiation device within the maximum detection area (K) when the plane is used as the surface to be inspected (10), and / or the measurement area (M) characterizes the size of the area generated when radiation emitted by the first radiation device (2) is completely reflected to the first radiation detector device (4).

5. The method according to at least one of the preceding claims, characterized in that, The radiation is directed onto the surface to be inspected (10) through an opening in the housing, and the radiation emitted by the surface to be inspected passes through the opening.

6. The method according to at least one of the preceding claims, characterized in that, The area value (W) and / or the ratio value (V) are determined using a threshold method.

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

8. The method according to at least one of claims 5-6, characterized in that, The threshold for the thresholding method is determined using a standard surface.

9. The method according to at least one of the preceding claims, characterized in that, The surface to be inspected is curved, and / or smaller than the measurement area predetermined / able to be illuminated by the first radiation device, and / or has both glossy and matte surface areas.

10. The method according to at least one of the preceding claims, characterized in that, The gloss value of an ideal surface is determined using the ratio value (V) for the surface to be inspected obtained according to the preceding claim, wherein the ideal surface corresponds to the surface to be inspected in terms of optical properties, but the ideal surface is flat and at least as large as the measurement area and / or the effective surface value (W).

11. The method according to at least one of the preceding claims, characterized in that, The irradiation device (22) irradiates the surface (10) substantially perpendicularly, and the radiation detection device (24) detects the radiation emitted from the surface under test that is substantially perpendicular to the surface under test.

12. A device (1) for detecting surface optical properties, comprising: An irradiation device (22) is suitable for irradiating a surface to be inspected with radiation along a predetermined irradiation direction. A radiation detection device suitable for recording spatially resolved images of radiation emitted and, in particular, reflected by a surface in response to irradiated radiation, wherein the radiation detection device has a maximum detection area (K) for detecting radiation incident thereon. An image recording apparatus adapted to determine at least one effective area value (W) characterizing a region within a predetermined and / or predeterminable measurement region (M) located within the maximum detection region (K), wherein emitted, particularly reflected radiation arrives at the region in a predetermined and / or predeterminable manner, particularly relating to luminance and / or color values; and A processor device adapted to determine at least one ratio value (V) characterizing the relationship between the surface value (W) and the measurement area.

13. The apparatus according to the preceding claim, characterized in that, The device (1) has a housing with an opening, the irradiation device being adapted to irradiate the surface through the opening, and the radiation detection device being adapted to detect radiation from the surface in response to radiation emitted by the irradiation device and passing through the opening.

14. The apparatus according to at least one of the preceding claims, characterized in that, The optical inspection device (20) has a telecentric objective lens device (30), wherein the telecentric objective lens device is preferably disposed between the surface to be inspected (10) and the radiation inspection device.

15. The apparatus according to at least one of the preceding claims, characterized in that, The device has a radiation deflection device (12) adapted to deflect the radiation emitted by the irradiation device so that the radiation strikes the surface along the second irradiation direction (R2), wherein the radiation deflection device preferably deflects the radiation emitted by the irradiation device by an angle of 30° to 150°.

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