WO2025027147A2 - Apparatus and method for examining surface properties - Google Patents

Abstract

The invention relates to an apparatus (1) for examining optical properties of surfaces (10), comprising a first radiation device (2) suitable and intended for radiating radiation in a first incoming radiation direction (R1) onto the surface (10) to be examined, a first radiation detector device (4) suitable and intended for sensing the radiation radiated by the first radiation device (2) onto the surface (10) to be examined and reflected by the surface (10) in a first outgoing radiation direction (R1'), and an optical sensing device (20), which has an irradiation device (22) suitable and intended for radiating radiation in a second incoming radiation direction (R2) onto the surface (10) to be examined and a radiation sensing device (24) suitable and intended for sensing the radiation radiated by the irradiation device (22) onto the surface (10) to be examined and output by the surface (10) in a second outgoing radiation direction (R2'), characterized in that the second incoming radiation direction (R2) and the second outgoing radiation direction (R2') are essentially opposite.

Description

Device and method for investigating surface properties

Description

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 surfaces of motor vehicles, but it is pointed out that the device can also be used for other surfaces, for example of furniture or of electronic components or (small) buttons of electronic devices.

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

The classic gloss measurement has strict specifications regarding the optical configuration. The measured values for the 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 it is on flat samples. If the photo element 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. There is therefore no detailed information about the surface if the photo element is replaced by a camera. However, unlike the photo element, the camera can compensate for any possible tilting of the measuring device in relation to the surface normal. The aperture image can be tracked and the aperture can be virtually reproduced using the camera's pixels.

These camera recordings 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 in a defined area for a correct measurement. The applicant reserves the right to claim protection for such a design.

An area sensor at the position of the classic detector preferably enables tracking of the reflected signal. For example, the brightness center of gravity in the recorded intensity image can be used for tracking.

If the measuring device is tilted, the bright illumination aperture image moves away from the defined position. The sample surface to be measured can also actively tilt away, e.g. with moving web materials in a robotics application. If the center of gravity leaves a defined tolerance range, the measurement is preferably classified as invalid and feedback is given about the excessive tilt.

The area sensor can also be used to measure the gloss value. For this purpose, a virtual aperture can be defined in the size of the mechanical aperture. The summed brightness value of the virtual aperture corresponds to the classic measured value. The virtual aperture can also be placed around the center of gravity and coupled with it. This also allows the tilting of the measuring device to be compensated to a certain extent. HDR images are preferably required for absolute measurement recording.

The area sensor can also be used in combination with the classic sensor.

For this purpose, a part of the detector signal can be decoupled (particularly via a beam splitter) and fed to the area sensor. The detection of the tilt is carried out by the Area sensor. The classic sensor with a mechanical aperture is preferred for simultaneous measurement of the signal.

The present invention is based on the object of enabling a gloss measurement that can be traced back to the classic gloss measurement, even for curved surfaces. A further object of the invention is to enable a determination of the surface properties (in particular gloss values) of very small surfaces. A further object of the invention is to enable a determination of surfaces that have both glossy and matte areas.

For curved surfaces, the invention proposes to combine the characterization of the surface geometry and the classic gloss measurement. However, this procedure can also be applied to small surfaces and surfaces that have matt and glossy areas.

Different methods of observation are known from the state of the art. One such method is the so-called measuring spot observation.

Normally, a spot observation is used to detect dirt or damage on the surface. A common method of incident light illumination is called dark field microscopy. Only the light diffusely reflected from the surface hits the observation unit. This method cannot be used on uneven and/or reflective surfaces. On reflective surfaces, for example, you would see dust particles on which the light is diffusely reflected.

Dark field lighting can be used for matt surfaces, although here too no curvatures can be seen with circular lighting. However, all-round lighting is needed for freedom of rotation, i.e. the measured values should be independent of the positioning of the measuring device. Scratches can be detected in the dark field, although deep scratches will be shadowed.

High-gloss or reflective sample surfaces can only be measured using the inline

Illumination and (as described in the context of the invention) in combination with a te- telecentric lens. The applicant was able to determine that the telecentric lens prevents the image of reflections of the light source on the surface. The effect is based on the limited angle acceptance and depth of field in the telecentric case. A large lens of a telecentric lens can also capture all the light, for example in the case of parallel incident and reflected light. When using a conventional lens, light reflected back at the edges of the measuring area cannot be recorded.

In microscopy, this inline lighting is called bright field lighting. To avoid reflections from the light source (in critical lighting), the so-called Köhler lighting can be used. In contrast to critical lighting, a uniform illumination of the object is achieved.

However, this Köhler illumination is comparatively complex, so that the invention is also based on the provision of a simpler arrangement. As shown in more detail below, a lens with an aperture is used for this purpose.

In industrial image processing, flat, homogeneous lighting is used to avoid the problem of reflection in a cost-effective and user-friendly way. The light source consists of a homogeneously illuminated surface the size of the observation area. This lighting can be implemented using an LED matrix and a diffuser, for example. Within the scope of the invention, it is proposed that the coupling takes place, for example, via a beam splitter (diffuse coaxial lighting).

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

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

Normally, in image processing, the combination of telecentric lenses with telecentric illumination is not used in incident light but in transmitted light. The simple However, an inline structure in reflection is not known from the prior art for the devices in question here and represents an important aspect of the invention.

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

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

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 subclaims.

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 radiation 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 also has an optical detection device with an irradiation device which is suitable and intended to radiate radiation in a second radiation direction onto the surface to be examined and with a radiation detection device which is suitable and intended to detect the radiation radiated by the irradiation device onto the surface to be examined and emitted by the surface in a second radiation direction.

According to the invention, the second irradiation direction and the second radiation direction are essentially opposite. The term "opposite" means that the radiation directions are essentially parallel to one another, but opposite to one another. The term "essentially parallel" means that the beam directions run at an angle to one another that is between 170° and 190°, preferably between 175° and 185°, between 178° and 182°, and particularly preferably between 179° and 181°.

A further device according to the invention for examining optical surface properties of surfaces has 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, and 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 and intended for recording HDR images and records HDR images.

Furthermore, the device has 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 located in a predetermined and/or predeterminable measuring area within the maximum detection area, which is reached by the radiation emitted (by the surface in response to the radiation radiated in (by the irradiation device)), in particular reflected, 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.

In addition, a processor device is provided which is suitable and intended to determine at least one ratio value which is characteristic of a relationship between the area value and the measuring 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.

The device can have all the features of the device described first 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.

Due to the curvature or insufficient 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.

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

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.

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

Fill factor = area value / measuring area (or partial area / total area of the measuring device), whereby both the area value and the measuring area are preferably given in the unit mm ^2. However, it is also conceivable that the area value and the measuring area each indicate an area measured in the same (but in particular any, for example different from mm ² ) (area) unit of measurement.

In a further advantageous embodiment, the device is portable. It is thus 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. The surface to be examined is preferably a curved surface or a very small surface. A very small surface is understood to be a surface that is smaller than 4 cm ^{2 ,} preferably smaller than 3 cm ² , preferably smaller than 2 cm ² , preferably smaller than 1 cm ² , preferably smaller than 0.5 cm ² , preferably smaller 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 smaller than 4 cm ^{2 ,} preferably smaller than 3 cm ² , preferably smaller than 2 cm ² , preferably smaller than 1 cm ² .

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.

Basically, the devices described here or the measurements performed 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 area sizes (less than 1 mm ² ).

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

These surfaces cause 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.

Classic gloss measurement requires flat surfaces. Calibration is also always carried out on flat surfaces. With curved surfaces, a certain proportion of the incident radiation is not reflected in the direction of the radiation detector device, which must be taken into account when evaluating measurement results, especially those generated during classic gloss measurements. With very small surfaces, not all of the incident radiation reaches the surface to be examined. Here, too, a correction is necessary.

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

In a preferred embodiment, the second direction of irradiation, i.e. the direction of irradiation in which the radiation from the irradiation device hits the surface, is essentially perpendicular to the surface to be examined. In this way, it is possible for this (second) direction of irradiation 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 initially irradiated onto the surface by the second radiation device and reflected by it).

In other words, the second irradiation direction, i.e. the irradiation direction in which the radiation originating from the irradiation device hits a measuring plane in which the surface to be examined is arranged (and/or is to be arranged), is essentially perpendicular to the measuring plane. As described above, it is thus possible for this irradiation device to be opposite to the direction of the radiation emitted, in particular reflected, by a surface arranged in the measuring plane (which has a flat design).

Preferably, the surface to be examined is arranged in a (the) measuring plane and/or is to be arranged for its examination. In the case of completely flat surfaces to be examined, this lies within the measuring plane.

In a further preferred embodiment, the first irradiation direction encloses an angle with the surface to be examined (and/or with the measuring plane) which 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 measuring plane) that is less than 80°, preferably less than 70°, preferably less than 65°. The angle is particularly preferably 60°.

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

The device preferably has a second radiation device which is suitable and intended to radiate radiation in a second (glancing angle) direction of incidence onto the surface to be examined, and a second radiation detector device which is suitable and intended to detect 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. The second (glancing angle) direction of incidence and the second (glancing angle) direction of emission preferably form an opposite angle with the measuring plane or with a (flat) surface to be examined.

Preferably, the device has a third radiation device which is suitable and intended to radiate radiation in a third (glancing angle) direction of incidence onto the surface to be examined, and a third radiation detector device which is suitable and intended to detect the radiation radiated by the third radiation device onto the surface to be examined and reflected from the surface in a third (glancing angle) direction of emission. Preferably, the third (glancing angle) direction of incidence and the third (glancing angle) direction of emission form an opposite angle with the measuring plane or with a (flat) surface to be examined.

Preferably, the second radiation device and the second radiation detector device and/or the third radiation device and the third radiation detector device (separated seeing the direction of incidence and the direction of emission) is designed in an analogous or identical manner to the first radiation device and the first radiation detector device.

Preferably, the angles which 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 which includes the ranges 15° - 25°, 40° - 50°, 55° - 65°, 70° - 80° and 80° - 90°, preferably selected from a group which includes angles of substantially 20°, 45°, 60°, 75°, 85°.

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.

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. The measuring plane is preferably also defined by this opening.

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

Preferably, these pins have a height or length that is greater than 0.2mm, preferably greater than 0.3mm, preferably greater than 0.5mm, preferably greater than 0.7mm and particularly preferably greater than 1.0mm. Preferably, these pins have a height or length that is smaller than 10mm, preferably smaller than 8mm, preferably smaller than 6mm and particularly preferably smaller than 5mm and preferably smaller than 4mm.

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

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

Preferably, two adjacent spacer elements are spaced apart from one another by more than 1 cm, preferably more than 2 cm. Preferably, two adjacent spacer elements are spaced apart from one another by more than 10 cm, preferably less than 8 cm, preferably less than 7 cm.

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

In a further advantageous embodiment, the device comprises a housing and this housing comprises 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 from the surface in response to the radiation emitted by the irradiation device and passing through the opening.

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.

Preferably, the radiation deflection device deflects the radiation emanating from the irradiation device at an angle lying between 30° and 150°. Preferably, this 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°.

Preferably, this angle is 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°.

In a further preferred embodiment, the radiation deflection device is designed as a mirror and in particular a partially transparent 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 around 50:50.

Preferably, this radiation deflection device or this mirror has different reflectivity depending on the side from which radiation hits it. Preferably, a portion of the radiation coming 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.

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

In a further preferred embodiment, the device has a lens (or a lens arrangement) and 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).

In a further advantageous embodiment, the (second) radiation detection device is suitable and intended to output a spatially resolved image of the radiation incident on it and/or the surface to be examined. A telecentric lens is particularly preferably provided in order to image the surface (to be examined) on the radiation detection device and in particular an image recording device. As mentioned above, the use of a telecentric lens on the observation side and in particular in the context 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, in particular with a telecentric lens.

The present invention is further directed to an optical detection device for optically detecting surfaces 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 reflected by the surface in a second radiation direction.

According to the invention, the (second) direction of incidence and the second direction of emission are essentially opposite. In this embodiment, a very special form of illumination and detection of the surface is carried out which is not known in the prior art.

In general, the radiation is preferably light and in particular light in the visible wavelength range. The radiation is particularly preferably white light and in particular standardized white light.

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

Particularly preferably, a lens and 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. Preferably, this (telecentric) lens is arranged closer to the detection device than to the surface to be examined. Preferably, this lens has at least two and preferably at least three lenses.

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

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:

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

- 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;

Preferably, the radiation detection device is a device which is suitable and intended for the spatially resolved detection of the radiation impinging on it. In particular, the radiation detection device is a camera.

- Determination of at least one effective area value for an area lying in a given and/or predeterminable measuring area within the maximum detection area. it is characteristic which is achieved 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;

- Determination of at least one ratio value (V) which 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.

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.

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

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.

The predetermined and/or predeterminable measuring surface is that partial area of the maximum measuring surface which would or will result in particular due to an oblique irradiation (of 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 vertical direction. This oval light spot would be recorded by the radiation detection device. In other words, the radiation detection device in this case records an oval, irradiated partial area of the surface to be examined, which is projected onto the measuring surface of the radiation detection device (in particular due to the optical arrangement of the radiation detectors). detection device such that the beam path of radiation emitted perpendicularly from the surface to be examined or 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.

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 measuring spot will appear oval at the relevant observation distances.

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).

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 one after the other.

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

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

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

The effective area value is also influenced by factors such as the curvature of the surface to be examined or the size of the surface to be examined. A curvature of this surface can mean that not all 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 to be examined is so small that not all 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.

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

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

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').

Furthermore, an irradiation device radiates radiation in a second irradiation direction onto the surface to be examined and a radiation detection device detects the radiation radiated by the irradiation device onto the surface to be examined and emitted (and in particular reflected) by the surface in a second radiation direction. These measurements can be carried out both simultaneously (for reflective surfaces) and at different times (for non-reflective surfaces).

According to the invention, the second radiation direction and the second emission direction are substantially opposite.

In a further method according to the invention for optically detecting surfaces, an irradiation device radiates radiation in one irradiation direction onto the surface to be examined and a radiation detection device detects the radiation radiated 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.

According to the invention, the second radiation direction and the second emission direction are substantially opposite.

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

In a further advantageous method, the radiation detection device records a spatially resolved image of the surface to be examined. For this purpose, for example, a camera or a CCD chip is used, on which the surface is preferably imaged. The surface to be examined is preferably imaged onto the radiation detection device using the 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 which has both shiny and matt (or matt reflecting and/or scattering) areas.

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).

The environment of the wearer is preferably chosen 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.

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.

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.

Preferably, the predetermined and/or predeterminable measuring area is an area that can be maximally illuminated by the first radiation device and/or a surface area of a surface to be examined (in particular flat or smooth). 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.

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 vertical direction.

The camera or the radiation detection device only knows the gloss measurement spot virtually (cannot measure the gloss measurement spot). The specified and/or specifiable measuring area is retrieved from a storage device in the device to determine the ratio value or the fill factor.

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

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.

In a further 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 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 surface, 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 preferably completely imaged onto the radiation detection device.

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.

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.

In a further preferred method, the radiation is irradiated 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 which emanates from the irradiation device but does not pass through said opening is disregarded.

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

Preferably, radiation emanating from the irradiation device which does not pass through the opening is absorbed by a wall of the housing and in particular an inner wall. In another preferred method, the maximum value is characteristic of the complete area of the aperture imaged onto the radiation detector.

With an "ideal" surface, the opening is completely imaged onto the radiation detection device. This is the maximum area that can be illuminated and therefore the maximum value. It is therefore assumed here that all radiation passing through the opening is reflected exactly by the surface and thus reaches the radiation detection device, so that the surface is ideally imaged onto the detection device.

Preferably, the maximum value is the area of the opening.

In a further 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 areas of an image recording device are considered as irradiated or not irradiated. In this way, it can be determined for each irradiated pixel of the radiation detection device whether this is still assigned to the illuminated area or not.

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).

A preferential decision is therefore made as to which pixels are still counted as part of the values determining the area value and which are not.

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.

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

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

In a further preferred method, the fill factor is mathematically linked to the gloss value(s). Preferably, the fill factor is placed in a mathematical relationship with (in particular measured) gloss values, for example divided (or multiplied) by these, in particular in order to carry out evaluations for curved or small surfaces.

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.

In a further preferred method, the surface to be examined is curved. In a further 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 measuring area that is predetermined and/or can be illuminated by the first radiation device.

In another preferred method, the surface to be examined has both glossy and matte surface areas.

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.

In this way, it is preferably possible to convert data determined for an actual surface into data that would result for a flat surface. In particular, in this way, for example, a gloss value can be determined for a curved surface to be examined, which in a (classical) gloss measurement for This surface would result in a flat surface shape instead of a curved surface shape (and thus otherwise the same optical properties).

In a further preferred method, the irradiation device radiates the radiation essentially perpendicularly onto the surface and the radiation detection device detects radiation that is emitted and in particular reflected from the surface essentially perpendicularly to the latter. The term "perpendicular" is assumed to refer to an ideal, flat surface. The radiation is preferably also emitted perpendicularly to an opening cross-section of the opening of the housing described above.

In another preferred method, a telecentric lens is used to image the surface onto the radiation detection device.

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

Showing:

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

Fig. 1b is a photograph taken with the device of Figure 1a, the surface being reflective;

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

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

Fig. 4 is a representation of a device according to the invention in its first application; Fig. 5 is a representation of a device according to the invention for a second application;

Fig. 6 shows a representation for carrying out an inline measurement;

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

Fig. 8a, 8b Representations for measuring curved surfaces;

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

Fig. 10 is a diagram illustrating measurement results for matt surfaces;

Fig. 11 is a further illustration to illustrate a further method step of the present invention;

Fig. 12 shows a representation for determining gloss values from the fill factor;

Fig. 13 is a representation of a telecentric optics;

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

Fig. 15 another representation of the telecentric optics to illustrate dimensions; and

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

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

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

Fig. 1b shows an image taken in this way over a reflective surface. 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 different glossy and matte parts, nor for surfaces that are very small.

Fig. 2a, 2b show two basic approaches to observing surfaces. Fig. 2a shows a classic 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 shine onto the surface at a predetermined angle, here 45°, and an image recording device 146 records the light scattered by the surface (but preferably not the reflected light).

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.

Figures 3a to 3d show four images of recorded surfaces. The images in Figures 3a and 3c were recorded using the dark field method and images 3b and 3d using the inline illumination mentioned above.

Fig. 3a and 3b show a black glass surface with a scratch (the gloss value is 95 GU (gloss unit) when measured at a measuring angle of 60°). Fig. 3c and 3d show a structured surface. The gloss value at an angle of 60° is 69.3 GU.

Fig. 4 shows a device according to the invention for examining surface properties in a first embodiment. The reference number 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. In this way, not all of the radiation reflected from the surface 10 reaches the first radiation detector device 4.

The reference number 20 refers in its entirety to an optical detection device for the surface. As will be 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.

Fig. 5 shows the device comparable to the device in Fig. 4, but 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 on an electrical item. This holder 11 is much smaller in cross-section than the surface 10 itself. In this way, radiation reflected from the holder 11 can be prevented from reaching the radiation detector device 4. Here, too, an optical detection device, designated in its entirety by 20, is provided.

In this application, which is also preferred according to the present invention, the area or the geometric extent (in at least one direction) of the surface 10 of the small workpiece to be examined is smaller than the area or the geometric extent of a measuring area (predetermined by the device). The measuring area results in particular from the area that can be irradiated or illuminated by the first radiation device 2 within a measuring plane. In the application shown here in Fig. 5, due to the small (geometric) extent of the surface 10 to be examined in comparison 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.

As the uppermost and lowermost beam paths 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.

Compared with a surface to be examined that fills the measuring surface, for example, a (classical) (gloss) measurement for this smaller surface to be examined 10 without correction of the surface size (incorrectly) 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 surface.

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

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 surface), and/or whether the surface 10 to be examined extends completely over the entire measuring range or the entire measuring surface of the device.

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 functions as a correction value for the measured value obtained from the radiation detector device 4.

Fig. 6 shows the optical detection device 20. This has a telecentric lens device, designated overall by 30. The reference numeral 24 designates an (optical) radiation detection device, such as a camera or a CCD chip.

The reference number 32 designates a light source, such as in particular but not exclusively an LED or a plurality of LEDs, and the reference number 34 designates 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 takes place in the direction R2). The radiation reflected by the surface 10 is reflected in the direction R2', in the direction of the radiation detection device, in particular the image detection device 24 or camera. This arrangement generates (approximately) parallel light for sample illumination.

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

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

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. K could therefore be, for example, the sensor area (used in particular during the measurement) a CCD chip of the irradiation device 22 or the optical detection device 20.

The reference symbol W indicates the effective measuring area of the gloss detector, for example when a curved surface is used to be examined. As mentioned above, this area W is preferably determined from an image. The ratio between W and M gives the fill factor V.

This gives the fill factor as:

Fill factor = effective area W/ maximum area M.

Within the scope of the present invention, it is therefore proposed to combine or unite a classic gloss measurement and an inline observation from above. With such a structure as shown above, the surface areas contributing to the gloss (in particular the surface areas contributing when carrying out a classic gloss measurement) can be determined and their effective area can be determined.

These areas can be areas on curved surfaces that run, for example, normal or parallel to the above-mentioned measuring axis. It is also possible to measure the surface of objects that are smaller than the actual measuring spot when measuring gloss. To do this, as mentioned above, the objects must be placed on suitable holders below a measuring opening. Reflections from the holding devices into the detectors should preferably be excluded.

Another way to measure is to measure surfaces that have both glossy and matte parts. These surfaces can be differentiated according to the matte and glossy parts and these can be calculated separately.

Fig. 8a and 8b show two measurements on curved surfaces 10 as examples. In the examples shown in Fig. 8a and 8b, the surface to be examined is the surface of a (straight) (circular) cylinder. The surface of the cylinder is viewed in a direction MO along the axis of the cylinder. curved. 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 not curved in a direction of the measuring plane (or measuring surface) that is perpendicular to this. Here it is possible, for example, to measure perpendicular to a radius of curvature or along the axis of the cylinder (i.e. in the direction of the arrow MO in Fig. 8b)) or parallel to the radius of curvature or perpendicular to the axis of the cylinder (and along the measuring surface or the measuring plane), i.e. along the direction of the arrow MO shown in Fig. 8b. Depending on the measuring arrangement, significantly different images can be expected.

Fig. 9 shows a representation of different surfaces and the corresponding images taken. Dark field images are shown in the top row. The dark field images cannot reproduce the curvature of the surfaces. The bright spots represent dust particles on the surface. The middle row shows images taken inline and the bottom row shows an illustration of the fill factor. The surface examined here is a glossy surface.

In Fig. 9, all images were taken at a scattering angle, i.e. gloss measurements were performed.

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 surface of a cylinder with a radius of curvature of 200 mm under vertical alignment (in particular the gloss measurement in comparison to the axis of the cylinder). In other words, with this alignment of the device 1 to the cylinder surface to be examined, the irradiation direction R1 of the (first) radiation device 2 and/or the radiation direction R1' run essentially perpendicular to the axis of the cylinder.

The third column and the top row also show an image of a surface, in this case the surface of a cylinder, with a radius of curvature of 200mm, 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. The measurement However, in comparison to the second column, the solution is provided with an orientation of the surface to be examined in relation to the device that is rotated by 90°. In other words, in the orientation of the device 1 in the third column to the lateral surface of the cylinder to be examined, the irradiation direction R1 of the (first) radiation device 2 and/or the radiation direction R1' run essentially parallel to the axis of the cylinder.

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.

The bottom line shows a representation from which the fill factor for each situation can be shown and illustrated.

Analogous to Fig. 7, the reference symbol M designates 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, optical elements such as one or more aperture(s) in the beam path between the (first) radiation device 2 and the (first) radiation detector device 4.

In the case of 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.

The reference symbol W indicates the image of the surface 10 to be examined irradiated by the (first) radiation device 2, which contributes to the radiation of radiation in the radiation direction R1' for the detection of this emitted radiation by the (first) radiation detector device 4. In the case of flat or level surfaces to be examined, this area corresponds to M, since the radiation direction RT at every point on the surface to be examined is opposite to the radiation direction (relative to a measuring plane). In the case of cylindrically curved surfaces, as illustrated in the 2nd to 5th columns, outer dark stripes can be seen in the inline images to the side of the central bright stripe. These dark stripes are created in the inline images because the corresponding surface areas are inclined with respect to the irradiation direction R2 in such a way that the radiation emitted by the irradiation device 22 in the irradiation direction R2 and striking these surface areas is not emitted or reflected in the direction R2' towards the radiation detection device 24, but in a different radiation direction. Therefore, the corresponding areas of the detection surface (K) of the radiation detection device 24 remain dark.

The situation is similar with the surface areas of the surface to be examined that are inclined with respect 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 areas with radiation in the direction of incidence R1 and emitting radiation in response to the irradiated radiation and the (first) radiation detector device. Here too, the radiation irradiated into these surface areas of the surface to be examined that are inclined with respect to the measuring plane is emitted and/or reflected in a direction different from the direction of emission RT due to the inclination of these surface areas, 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.

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

The areas W are significantly narrower in the last two columns 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 stronger curvature than the surfaces examined in the 2nd and 3rd columns with a significantly larger radius of curvature of 200 mm. The smaller radius of curvature or the stronger curvature of the respective cylindrical surface means that only a corresponding sufficiently narrower surface area has a sufficiently low inclination with respect to the measuring plane or measuring surface in order to emit or reflect radiation in the radiation direction RT so that it can be detected by the (first) radiation detector device 4.

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.

In the alignment 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, 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. straight, surface profile along this second surface direction. The first and second surface directions refer to a coordinate system in relation to the surface to be examined and preferably run within the measuring plane.

In the alignment shown in the third and fifth columns, the surface to be examined is rotated by 90° (with respect to a rotation axis perpendicular to the measurement plane). In this alignment, the above-mentioned second surface direction, along which the surface to be examined has a non-curved surface profile, is perpendicular to the direction of incidence R1 or perpendicular to the cross-sectional plane which runs 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 alignment, the (maximum) measurement area M covers a larger surface area of the surface to be examined than in the alignment shown in column 2, which has a sufficiently low inclination to allow the (first) radiation device to illuminate the respective surface area despite the inclined surface. to emit or reflect richly irradiated radiation to the (first) radiation detector device so that it can be detected.

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.

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

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.

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.

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

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

It can also be seen that, as expected, the contrast on the matte surface is much lower than on the glossy surface.

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

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 for this purpose. The linear relationship between fill factor 0 and 1 is preferably used as a guideline.

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

The reference number 50 designates a first lens and the reference number 51 a second lens, which preferably together form an achromat. The reference number 53 designates a third lens, which is preferably biconvex.

Preferably, a distance between the first lens 50 and the second lens 51 (here referring 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.

Preferably, a distance between the first lens 50 and the second lens 51 (here referring 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.

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

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

Preferably, the second lens has a diameter that is greater than 5mm, preferably greater than 6mm and preferably greater than 7mm and particularly preferably greater than 8mm. Preferably, the second lens 51 has a diameter that is smaller than 12mm, preferably smaller than 11mm, preferably smaller than 10mm and particularly preferably smaller than 9mm.

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

The reference number 54 designates a holder or mount for the lens 50 and the reference number 56 a spacer ring. The reference number 55 refers to a coupling ring.

The reference number 64 designates a plug-on adapter which is held by means of a threaded pin on the lens structure of the two lenses 50, 51. The reference number 58 refers to a lock ring.

The reference number 65 designates a diaphragm holder. The reference number 62 designates a mounting bracket and the reference number 68 an adapter (in particular for a test setup).

Fig. 15 shows another representation of the telecentric lens. It can be seen that the distance between the surface to be examined and the first lens is greater than 20mm, preferably greater than 30mm, preferably greater than 40mm, preferably greater than 50mm and preferably greater than 60mm. Preferably, the distance between the surface to be examined and the first lens is less than 100mm, preferably less than 90mm, preferably less than 80mm and particularly preferably less than 70mm.

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.

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.

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

In the case shown, two effective areas result. The first area is the intersection of the ellipse with the light areas A and the second area is the intersection of the ellipse with the dark areas B.

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

Such a calculation of the classic gloss value Gtotai related to the entire (maximum) measuring area M (here represented by the ellipse E) with area A _to tai results in particular from the classic gloss value G1 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:

Gtotal - Gl * Al/Atotal + G2 * A2/Atotal If one of the two values Gi and G2 is known, for example by measuring a location on the sample where only one type occurs, the above equation can be solved.

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:

R = I 1/I2 = G1/G2.

This relationship can be used to solve the above equation.

For example, for a classic gloss value G2 = 100 Gil measured at the edge of the sample plate and an area ratio A2/A _to tai = 2/3 and 12=325110 as well as an area ratio A Atotai = 1/3 and h = 6046, the applicant determined G1 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.

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

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

The device can be a handheld device or a device that can be carried by a user. In addition to the handheld device, the device can also be a device suitable for various robot systems.

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. Convex and concave curved surfaces are therefore possible. It is important to know that for classic gloss measurements, you should stay in the measuring plane or in the measuring range of the device. With robot devices, this is possible at a certain distance from the floor. As mentioned above, the effective measuring area does not have to be continuous. It can also be several (especially horizontal) surface elements.

The fact that there are no shadows for camera observation from above is preferred. Shadows can be problematic for classic measurements at large angles.

The elliptical observation spot for the classic gloss measurement can be detected in production with the telecentric camera (when using a (flat) matt surface). For this purpose, a light source can be used instead of the photo element. Preferably, characteristic data (e.g. as a specified measuring area) is stored in a memory device of the device (for image evaluation).

The applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided that they are new individually or in combination compared to the prior art. It is also pointed out that the individual figures also describe features which can be advantageous in themselves. The person skilled in the art immediately recognizes that a certain feature described in a figure can also be advantageous without adopting further features from this figure. The person skilled in the art also recognizes that advantages can also arise from a combination of several features shown in individual or different figures.

Claims

patent claims 1. Device (1) for examining optical properties of surfaces (10) with a first radiation device (2) which is suitable and intended to radiate radiation in a first irradiation direction (R1) onto the surface (10) to be examined, with a first radiation detector device (4) which is suitable and intended to detect the radiation radiated by the first radiation device (2) onto the surface (10) to be examined and reflected by the surface (10) in a first radiation direction (R1'), and with an optical detection device (20) with an irradiation device (22) which is suitable and intended to radiate radiation in a second irradiation direction (R2) onto the surface (10) to be examined, and with a radiation detection device (24) which is suitable and intended to detect the radiation radiated by the irradiation device (22) onto the surface (10) to be examined and emitted by the surface (10) in a second radiation direction (R2'). to detect radiation, characterized in that the second irradiation direction (R2) and the second radiation direction (R2') are substantially opposite. 2. Device (1) according to claim 1, characterized in that the irradiation direction is substantially perpendicular to the surface to be examined (10). 3. Device (1) according to at least one of the preceding claims, characterized in that the first irradiation direction (R1) encloses an angle with the surface to be examined (10) which is greater than 15°, preferably greater than 30°, preferably greater than 35° and particularly preferably greater than 40° and/or the first irradiation direction (R1) encloses an angle with the surface to be examined (10) which is smaller is less than 80°, preferably less than 75°, preferably less than 70° and particularly preferably less than 65°. 4. Device (1) according to at least one of the preceding claims, characterized in that the device (1) has a housing (21) within which the first radiation device (2), the first radiation detector device (4), the second radiation device (6) and the second radiation detector device (8) are arranged. 5. Device (1) 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 (6) in such a way that this radiation strikes the surface in the second irradiation direction (R2), wherein the radiation deflection device preferably deflects the radiation emanating from the second radiation device at an angle which is between 30° and 150°. 6. Device according to the preceding claim, characterized in that the radiation deflection device (12) is designed as a mirror and in particular a partially transparent mirror. 7. Device (1) according to at least one of the preceding claims, characterized in that the second radiation detector device (8) is suitable and intended to output a spatially resolved image of the radiation impinging on it and/or the surface to be examined. 8. Method for examining optical properties of surfaces, wherein a first radiation device (2) radiates radiation in a first irradiation direction (R1) onto the surface (10) to be examined, and a first radiation detector device (4) detects the radiation emitted by the first radiation device (2) onto the surface to be examined. CORRECTED SHEET (RULE 91) ISA/EP radiation irradiated onto the surface (10) to be examined and reflected from the surface (10) in the radiation direction (RT) is detected, and wherein an irradiation device (6) irradiates radiation in a second irradiation direction (R2) onto the surface (10) to be examined and a radiation detection device (8) detects the radiation irradiated by the second radiation device (2) onto the surface (10) to be examined and emitted by the surface (10) in a second radiation direction (R2'), characterized in that the second irradiation direction (R2) and the second radiation direction (R2') are substantially opposite. 9. Optical detection device (20) for optically detecting surfaces with an irradiation device (22) which is suitable and intended to irradiate radiation in an irradiation direction (R2) onto the surface (10) to be examined and with a radiation detection device (24) which is suitable and intended to detect the radiation irradiated by the irradiation device (2) onto the surface (10) to be examined and reflected by the surface (10) in a second radiation direction (R2'), characterized in that the second radiation direction (R2) and the second radiation direction (R2') are substantially opposite. 10. Optical detection device (20) according to claim 9, 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. 11. Optical detection device (20) according to one of the preceding claims 9 - 10, characterized in that the irradiation device (22) comprises a light source (32), a diaphragm (34) and preferably a a lens (36). 12. Method for optically detecting surfaces, wherein an irradiation device (22) radiates radiation in an irradiation direction (R2) onto the surface (10) to be examined and a radiation detection device (24) detects the radiation radiated by the irradiation device (2) onto the surface (10) to be examined and reflected by the surface (10) in a second radiation direction (R2'), characterized in that the second radiation direction (R2) and the second radiation direction (R2') are substantially opposite. 13. Method according to the preceding claim, characterized in that a telecentric optic is used to detect the radiation, which is preferably arranged between the surface and the radiation detection device. 14. Method according to at least one of the preceding claims 12 -13, characterized in that the radiation detection device records a spatially resolved image of the surface to be examined. 15. Method according to at least one of the preceding claims 12 -13, characterized in that the surface to be examined is a curved surface or a surface of a small component or a surface which has both shiny and matt areas.