WO2024260777A1 - Apparatus and method for examining optical properties of surfaces - Google Patents

Abstract

The invention relates to an apparatus (1) for examining optical properties of surfaces, comprising a first radiation device (2) which is suitable and intended for irradiating radiation in an irradiation direction (R1), characterised by a first irradiation angle (a1), onto the surface to be examined, and comprising a first radiation detection device (12) which is suitable and intended for detecting radiation, and in particular scattered radiation, emitted at a first emission angle (b1) from the surface (10) to be examined in response to the irradiated radiation, and comprising a second radiation detection device (14) which is suitable and intended for detecting radiation emitted at a second emission angle (b2) from the surface (10) to be examined in response to the irradiated radiation, characterised in that the apparatus (1) has a second radiation device (4) which is suitable and intended for irradiating radiation in a second irradiation direction (R2), characterised by a second irradiation angle (a2), onto the surface to be examined, wherein the first irradiation angle (a1) and the second irradiation angle (a2) are substantially mirror-inverted in relation to a direction perpendicular to the surface to be examined.

Description

Device and method for investigating optical properties of surfaces

Description

The present invention relates to a device and a method for examining surface properties. Surfaces, such as the surfaces of motor vehicles, have a wide variety of surface properties. In particular, the optical impression of such a surface varies greatly depending on the light irradiation.

Various devices and methods are known from the state of the art with which the optical surface properties of, for example, motor vehicles, but also other objects such as furniture, can be examined. Usually, light is shone on the surface to be examined and one or more intensity sensors record the radiation scattered and/or reflected by the surface in order to get an impression of the surface properties.

A wide variety of properties can be checked, such as shine, orange peel, color impression and the like.

The present invention is based on the object of making existing devices for examining surface properties more versatile. This is achieved according to the invention by the subject matter of the independent patent claims. Advantageous embodiments and further developments are the subject matter of the subclaims. Another application concerns the evaluation of so-called retro-reflective surfaces. For example, measurements are taken on special effect pigments that reflect incident light and, in particular, reflect it back regardless of the direction of incidence.

In addition, coatings or surfaces that use crystal glass pigments have recently become known, sometimes in combination with already known metallic particles. Such coatings can significantly improve the visibility of objects for both people and machines, for example so-called LIDAR (light detection and ranging) systems. Such crystal glass pigments can be special beads embedded in solutions.

The optical detection and assessment of such surfaces is also not easily possible with devices and methods known from the state of the art, since on the one hand a high level of precision is required and on the other hand a local arrangement, size or orientation of such pigments must be detected with high accuracy. In particular, it should be noted that such surfaces are also sometimes curved.

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 onto the surface to be examined in a first radiation direction characterized by a first radiation angle.

Furthermore, a first radiation detection device is provided which is suitable and intended to detect radiation emitted and in particular scattered at a first radiation angle from the surface to be examined in response to the irradiated radiation. Preferably, this first radiation detection device (in particular due to its positioning) is not suitable to detect radiation reflected at a first radiation angle from the surface to be examined in response to the irradiated radiation.

Furthermore, a second radiation detection device is provided which is suitable and intended to detect at a second radiation angle from the surface to be examined in response to the radiation radiated (by the first radiation device) emitted and in particular scattered radiation. Preferably, this second radiation detection device (in particular due to its positioning) is not suitable for detecting radiation reflected at a first radiation angle from the surface to be examined in response to the irradiated radiation.

According to the invention, the device has a second radiation device which is suitable and intended to radiate radiation onto the surface to be examined in a second radiation direction characterized by a second radiation angle, wherein the first radiation angle and the second radiation angle are substantially opposite with respect to a direction perpendicular to the surface to be examined.

A further device according to the invention for examining optical properties of surfaces has a first radiation device which is suitable and intended to radiate radiation onto the surface to be examined in a first radiation direction characterized by a first radiation angle.

Furthermore, a first radiation detection device is provided which is suitable and intended to detect radiation emitted and in particular scattered at a first radiation angle from the surface to be examined in response to the irradiated radiation. Preferably, this first radiation detection device (in particular due to its positioning) is not suitable to detect radiation reflected at a first radiation angle from the surface to be examined in response to the irradiated radiation.

Furthermore, a second radiation detection device is provided which is suitable and intended to detect radiation emitted and in particular scattered at a second radiation angle from the surface to be examined in response to the radiation radiated in (by the first radiation device). Preferably, this second radiation detection device (in particular due to its positioning) is not suitable to detect radiation reflected at a first radiation angle from the surface to be examined in response to the radiated in.

According to the invention, the device has a further radiation detection device which is suitable and intended to detect radiation from the surface to be examined in a direction of radiation characterized by a further radiation angle in response to the to detect emitted and, in particular, reflected radiation, whereby the direction of incidence and the direction of emission are essentially opposite.

In this embodiment according to the invention, it is therefore proposed that the light or radiation emitted by the surface in the direction opposite to the direction of incidence is observed.

In a preferred embodiment, the surface is a surface provided with pigments and in particular effect pigments and/or with reflective particles.

Particularly preferably, the surface is a surface which reflects at least a portion and preferably a significant portion of the radiation radiated onto it (in particular regardless of the direction of incidence), wherein this surface particularly reflects a significant portion of this radiation in a direction opposite to the direction of incidence even when the direction of incidence is not perpendicular to this surface but at an angle deviating from this perpendicular direction by at least 10°, preferably by at least 20° and preferably by at least 30°. This portion is in particular greater than the radiation scattered in this direction.

In a further preferred embodiment, the device has a control device which causes the radiation emitted by the first radiation device to strike the surface and the radiation emitted by the surface in response to this incident radiation to strike the further radiation detection device.

In a further preferred embodiment, the control device is suitable and intended to control the further radiation detection device in such a way that it receives the radiation emitted by the first radiation device and reflected by the surface and preferably outputs at least one signal which is characteristic of this radiation.

Preferably, the further radiation detection device is suitable and intended to record a spatially resolved image of the radiation impinging on it. In a further preferred embodiment, the further radiation detection device is suitable and intended to output at least one signal which is characteristic of an intensity of the radiation incident on it.

Preferably, the control device controls the further radiation detection device such that the further detection device is activated when, i.e. at least temporarily in the same period of time, radiation is emitted into the first radiation device.

In a further preferred embodiment, the further radiation detection device is suitable and intended to detect radiation in the visible wavelength range.

In a further preferred embodiment, the further radiation detection device is suitable and intended to detect radiation in the infrared wavelength range and in particular in the near-infrared wavelength range. In a further preferred embodiment, the further radiation detection device is suitable and intended to detect radiation in a wavelength range of 880 nm - 930 nm, preferably from 890 nm - 920 nm and particularly preferably from 900 nm - 910 nm.

In a further preferred embodiment, the further radiation detection device comprises a silicon-based sensor device.

Preferably, the surface to be examined is a painted surface and in particular a surface provided with an effect paint.

Preferably, the radiation is light and in particular light in the visible wavelength range or the radiation contains at least light in the visible wavelength range.

It is proposed that not only is radiation radiated onto the surface in a specific direction of incidence, but conversely, radiation that is reflected and/or emitted and in particular reflected by the surface is also guided away from the surface in a direction opposite to this first direction of incidence. This approach is unusual in that attempts are usually made to separate the direction of incidence and the direction of reflection from one another. The advantage of this approach, however, is that on the one hand the scattered light can be detected in different directions, but on the other hand the same device also allows a determination of gloss effects (or more generally of effects observed in reflection).

In a preferred embodiment, the first radiation device is suitable and intended to emit consecutive or sequential monochromatic or essentially monochromatic light of various wavelengths, using preferably filter devices and in particular the filter wheel described in more detail below for this purpose. In this way, this first radiation device is used in particular for color measurement at different angles. Monochromatic light is understood to mean in particular light with a predetermined wavelength or a (particularly) narrow wavelength range. This wavelength range preferably comprises less than 50 nm, preferably less than 40 nm and particularly preferably less than 30 nm and particularly preferably less than 20 nm.

The second radiation device is preferably a white light illumination or has such. The second radiation device preferably serves on the one hand for camera measurement under vertical observation.

On the other hand, the subject matter of this application is also the additional use of this second radiation device for gloss measurement using the path also used for illumination as a detection path.

However, it would also be possible to use a further radiation detection device in addition to or instead of the second radiation device. In this way, the first radiation device could be used for the additional purpose of measuring gloss.

Such 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 onto the surface to be examined in a first radiation direction characterized by a first radiation angle.

Furthermore, a first radiation detection device is provided, which is suitable and is intended to detect radiation emitted and in particular scattered at a first radiation angle from the surface to be examined in response to the irradiated radiation. Preferably, this first radiation detection device (in particular due to its positioning) is not suitable for detecting radiation reflected at a first radiation angle from the surface to be examined in response to the irradiated radiation.

Furthermore, a second radiation detection device is provided which is suitable and intended to detect radiation emitted and in particular scattered at a second radiation angle from the surface to be examined in response to the radiation radiated in (by the first radiation device). Preferably, this second radiation detection device (in particular due to its positioning) is not suitable to detect radiation reflected at a first radiation angle from the surface to be examined in response to the radiated in.

According to the invention, the device has a further radiation detection device which is suitable and intended to detect radiation reflected from the surface in a further radiation direction characterized by a further radiation angle, wherein the first angle of incidence and this further radiation angle are substantially opposite with respect to a direction perpendicular to the surface to be examined.

In this case, the further radiation device is preferably also used for gloss measurements. In this embodiment, a further deflection device and/or a beam splitter device is preferably provided between the surface and the further radiation detection device.

Preferably, the device has a control device which causes the irradiation of light by the first radiation device and the irradiation of light by the second radiation device to occur at different times and/or in different time periods.

The device is preferably a portable device. However, it is also possible for the device to be arranged on a robot or robot arm, for example, in order to be guided over a surface in this way. the second radiation device is (at least) one LED and in particular (at least) one white light LED.

Preferably, the first radiation device and the second radiation device are symmetrical to each other with respect to a plane perpendicular to the surface to be examined.

Particularly preferably, at least one lens is arranged in the beam path between the first radiation device and the surface. Preferably, at least two lenses are arranged in the beam path between the first radiation device and the surface.

By substantially oppositely equal is meant that the first of the two angles has a predetermined size and the oppositely equal angle deviates from the exact oppositely equal position by no more than 5°, preferably by no more than 4°, preferably by no more than 3°, preferably by no more than 2° and particularly preferably by less than 1°.

In a further preferred embodiment, the second radiation device is positioned such that the radiation emitted by the second radiation device is reflected by the surface to be examined in a direction opposite to the first direction of incidence.

In a further preferred embodiment, the first radiation device is arranged in a first radiation arm and the second radiation device in a second radiation arm and these two radiation arms are symmetrical with respect to the above-mentioned plane perpendicular to the surface to be examined.

In a further preferred embodiment, the device has a further (radiation) detection device which is suitable and intended to detect radiation emitted by the second radiation device and reflected by the surface to be examined. This is therefore radiation which (at least in sections) runs in the direction opposite to the above-mentioned first radiation direction.

Particularly preferably, this further radiation detection device comprises a photodiode Preferably, a radiation deflection element such as a mirror is provided in a beam path between the surface to be examined and the further (radiation) detection device, which deflects the radiation reflected from the surface in the direction of the further (radiation) detection device.

In a further preferred embodiment, the device has a housing within which the first radiation device, the first radiation detection device, the second radiation detection device and preferably also the further (radiation) detection device are arranged.

Particularly preferably, this housing has an opening through which the first radiation device illuminates the surface to be examined. Particularly preferably, the light reflected from the surface, for example scattered or reflected light, or the scattered or reflected radiation, also enters the housing again through this opening.

Particularly preferably, said opening can be placed against the surface to be examined, so that during a measurement the surface is preferably arranged substantially directly outside the opening or outside the housing.

In a further advantageous embodiment, the interior of said housing is radiation-absorbing, for example made black.

Preferably, all of said radiation devices radiate the light through said opening onto the surface. Particularly preferably, said opening is the only opening in the housing through which radiation can enter the housing.

In a further preferred embodiment, the first radiation device is suitable and intended to emit radiation of different colors. For this purpose, it would be possible for the first radiation device to have a plurality of LEDs in different colors. In this way, the surface can be illuminated in different colors.

However, the first radiation device particularly preferably has a light source and a plurality of color filter devices which can be optionally inserted into a beam path between view of this light source and the surface to be examined. In this case, the radiation device is understood to be the light source with the respective color filter device(s).

Particularly preferably, the radiation device and/or the apparatus has a filter wheel which can be rotated about a predetermined axis of rotation and on which the said filters or color filter devices are arranged.

Preferably, at least three color filter devices are provided, preferably at least four, preferably at least five, preferably at least six, preferably at least eight, preferably at least twelve, preferably at least 15 and preferably at least 20.

In a further preferred embodiment, fewer than 50 filter devices, preferably fewer than 40, preferably fewer than 30 color filter devices are provided.

Preferably, all filter devices are at the same distance from a rotation axis of the filter wheel.

It is possible to provide a drive device such as a drive motor that can move the individual filter devices (by rotating the filter wheel) in front of the light source and/or into the beam path between the light source and the surface. The drive motor is preferably an electric motor and in particular a stepper motor. This can preferably move the filter wheel to a variety of rotational positions.

Preferably, the housing is optically sealed in such a way that no ambient light can enter the housing. In particular, the filter wheel is preferably designed in such a way that it is optically sealed with the housing so that no ambient light can enter the housing in the region of the beam path between the light source of the first radiation device and the filter wheel.

In known devices, a large number of light-emitting diodes are provided, for example 26 light-emitting diodes, whereby these were monochromatic or partially interference-filtered light-emitting diodes. Now it is provided that only one light source or a large number of similar light sources are provided, whereby the light sources These are in particular white light sources. These white light sources are particularly preferably interference-filtered. This large number of filters also makes it possible to achieve backwards compatibility with older devices from the same applicant.

The use of filters does have the disadvantage that the light reaching the surface is greatly attenuated. However, the applicant was able to determine that the light sources available on the market today are available with sufficient intensity and power so that, despite the color filters, sufficient radiation still reaches the surface.

A key advantage is that significantly fewer LEDs need to be used, for example only one LED now compared to 26 LEDs in previous versions. This improves cost efficiency.

Another advantage of using a filter wheel is that it does not need to be supplied with electricity as it does not contain any electronic elements.

On the other hand, as mentioned above, the light intensity can be lower in the manner described than in the case of chromatic LEDs. It is therefore proposed that a special optic, in particular a collimating optic, be provided on the white light LED. In this way, the radiation can be concentrated.

Preferably, a camera or image recording device with an achromatic camera lens is used. A high-performance achromatic display lens enables uniform illumination with fewer chromatic or spherical disturbances.

In further preferred embodiments, the device has a beam steering device which is designed such that, on the one hand, radiation emanating from the first radiation device strikes the surface through this beam steering device and, on the other hand, radiation reflected from the surface strikes the further radiation detection device and/or is directed accordingly by this beam steering device.

The beam steering device preferably has a beam splitter. It is possible and preferred that this beam splitter is movable. In one position of this beam splitter, for example, radiation emitted by the first radiation device can be unhindered pass through the beam steering device and is therefore preferably not deflected.

In a second position of the beam splitter, the radiation reflected from the surface can be reflected by the beam splitter in such a way that it reaches the further radiation detection device.

Preferably, at least one lens is arranged between the first radiation device and the beam steering device. Particularly preferably, a lens is arranged between the beam steering device and the surface to be examined. Preferably, at least one of these lenses is achromatic and preferably both lenses are achromatic. It would also be conceivable and preferred for these two lenses to form an achromatic objective.

In a further preferred embodiment, the said first angle at which the first radiation device radiates onto the surface is between 40° and 50° with respect to a direction perpendicular to the surface, preferably between 42° and 48°, preferably between 43° and 47°, particularly preferably between 44° and 46° and particularly preferably 45°.

In a further advantageous embodiment, the device has a third radiation detection device which is suitable and intended to detect emitted and in particular scattered radiation at a third radiation angle from the surface to be examined in response to the irradiated radiation (in particular irradiated by the first irradiation device).

In a further advantageous embodiment, the device has a fourth radiation detection device which is suitable and intended to detect radiation emitted and in particular scattered at a fourth radiation angle from the surface to be examined in response to the irradiated radiation.

Preferably, none of the first to fourth radiation detection devices is arranged such that radiation reflected from the surface to be examined (which was irradiated by the first radiation device) is detected.

Particularly preferably, a fifth radiation detection device is also provided, which is suitable and intended to detect the radiation emitted by the object to be detected at a fifth radiation angle. investigate the surface in order to detect the radiation emitted and, in particular, scattered radiation in response to the incident radiation.

In a further particularly preferred embodiment, a sixth radiation detection device is also provided, which is suitable and intended to detect radiation emitted and in particular scattered at a sixth radiation angle from the surface to be examined in response to the irradiated radiation.

In the latter case, the radiation scattered onto the surface by the radiation device is observed at six different angles. By observing or detecting the radiation in this way, a very precise image of the surface can be obtained and/or the optical properties of the surface can be analyzed in a very precise manner.

Preferably, at least one of these radiation detection devices is suitable and intended to detect an intensity of the radiation impinging on it. Preferably, at least two, preferably at least three and particularly preferably all of these radiation detection devices are suitable and intended to detect an intensity of the radiation impinging on them.

It is possible that these radiation detection devices are suitable and intended to detect light (and in particular its intensity) in different wavelengths. In particular, these radiation detection devices are suitable for detecting light at least in the entire visible spectrum.

Preferably, starting from the first radiation device, light in different colors or wavelengths is irradiated onto the surface by means of the filters described above, and the light scattered by the surface is detected by the four, five or six radiation detection devices mentioned above.

In a further advantageous embodiment, the device has an image capture device which is suitable and intended to capture radiation emitted by the surface, in particular scattered radiation, in a spatially resolved manner. This image capture device is particularly preferably arranged vertically above the surface to be examined. This image capture device is particularly preferably focused on the surface to be examined and therefore records in particular an image of the surface illuminated by the control device. This image capture device is preferably also suitable and intended to determine a light intensity occurring on it.

Preferably, the image capture device is a high-resolution image capture device and in particular a color camera. This can, for example, have a 5 megapixel camera chip.

Particularly preferably, an imaging optics which serves to project the image or the surface to be examined onto the image research device is designed in such a way that it produces a uniformly illuminated image field with few deviations.

This image capture device is particularly preferably also suitable and intended for recording effect pigments that may be present in the surface to be examined. The procedure described above, according to which an angle of incidence is also provided for gloss measurements, offers the advantage that a further measurement method can be integrated in a particularly cost-effective manner. This can be done, for example, by simply adding a lens and a diode to the device.

In this way, a gloss measurement can also be carried out with at least medium accuracy. This is particularly useful if additional information is to be given to the customer to supplement the color measurements.

In a further preferred embodiment, the device has a further radiation detector device which is suitable and intended to detect radiation emitted by the surface in the radiation direction and preferably to output at least one signal which is characteristic of this radiation. The further radiation detection device and the further radiation detector device are preferably spatially separated from one another and in particular spatially separated from one another within the housing. The above-mentioned radiation directing device is particularly preferably arranged between the radiation detection device and the further radiation detector device.

In a further preferred embodiment, the radiation directing device can direct radiation both to the further radiation detection device and to the further radiation detector device. In a further preferred embodiment, the radiation detector device is located opposite the further radiation detection device with respect to the radiation directing device.

In a further preferred embodiment, the further radiation detector device is also suitable and intended to detect further radiation components reflected and/or scattered by the surface.

In a further preferred embodiment, the further radiation detector device is suitable and intended to output a signal relevant to the intensity of the radiation incident on it.

In a further preferred embodiment, the further radiation detector device is arranged within the housing substantially at the same height as the further radiation detection device.

The present invention is further directed to a beam steering device, in particular for a device of the type described above. This beam steering device has a housing and a first radiation inlet through which radiation can enter the housing in a first radiation direction. Furthermore, the beam steering device has a first radiation outlet through which the radiation that entered through the first radiation inlet can exit the housing in the first radiation direction.

According to the invention, a beam splitter device or a beam splitter is arranged in the housing, which is suitable and intended to deflect radiation entering through the radiation outlet in a direction opposite to the direction of incidence in a deflection direction which deviates from the direction of incidence and the direction opposite to the direction of incidence and is in particular perpendicular to the direction of incidence. The housing also has a second radiation outlet through which the radiation deflected by the beam splitter device can exit the housing.

A beam steering device is therefore proposed in which radiation can simultaneously enter and be deflected through a radiation output.

The beam splitter device is particularly preferably a glass element and in particular a thin glass element. This thin glass element particularly preferably has a thickness which is greater than 0.1mm, preferably greater than 0.2mm, preferably greater than 0.3mm. Particularly preferably, this thin glass element has a thickness which is less than 2.0mm, preferably less than 1.5mm, preferably less than 1.0mm, preferably less than 0.8mm and particularly preferably less than 0.6mm and particularly preferably less than 0.4mm.

Preferably, this beam splitter device is highly transparent over a wide wavelength range (i.e. preferably has a (pure) transmittance of more than 90%, preferably more than 95% and particularly preferably more than 98%).

Preferably, the beam splitter device is arranged in a fixed position and in particular at a fixed angle with respect to the incident radiation. This angle is preferably between 30° and 60°, preferably between 35° and 55°, preferably between 40° and 50° and particularly preferably around 45°.

Preferably, this beam splitter device splits all rays, regardless of whether they hit its front or back, into a transmitted portion and a reflected portion. The type of splitting takes place according to the Fresnel equation depending on the refractive index and the angle of incidence.

In the application described here, there are preferably 2 transmission paths and 2 reflection paths. The transmitted radiation (preferably the majority) preferably experiences a parallel beam offset when passing through the beam splitter.

The radiation directing device described here makes it possible, as mentioned above, for radiation to be emitted onto the surface from a first radiation device and for radiation traveling in the opposite direction to be deflected, in particular, to a further radiation detection device.

In a preferred embodiment, at least one optical element and in particular a lens is integrated in the first radiation input of the beam steering device.

Preferably, at least one optical element and in particular a lens is also integrated into the first radiation output. In a further advantageous embodiment, the beam steering device can be integrated in its entirety into a housing.

The beam splitter device is particularly preferably a mirror and in particular a pivotable mirror. This mirror is preferably pivotable with respect to an axis that is perpendicular to the direction of incidence. This mirror is preferably pivotable by an angle that is between 20° and 90°, preferably between 30° and 70° and particularly preferably between 40° and 50°.

In a further preferred embodiment, the beam steering device has a third exit through which deflected radiation can exit.

Particularly preferably, this third output is spaced apart from the second and the first output. Particularly preferably, the third output is located opposite the second output. Particularly preferably, the beam splitter device is arranged between the second output and the third output.

Furthermore, the beam splitter device is preferably suitable both for directing radiation in the direction of the second output and for directing radiation in the direction of the third output.

In a further preferred embodiment, the beam direction in which radiation exits the second exit is opposite and parallel to the beam direction in which radiation exits the third exit.

The present invention further relates to a method for examining optical properties of surfaces, wherein a first radiation device radiates radiation onto the surface to be examined in a first radiation direction characterized by a first radiation angle, and a first radiation detection device and/or radiation detector device detects radiation emitted and in particular scattered radiation at a first radiation angle from the surface to be examined in response to the radiated radiation.

Furthermore, a second radiation detection device detects at a second radiation angle from the surface to be examined in response to the irradiated radiation. radiation emitted and especially scattered radiation.

According to the invention, a second radiation device of the apparatus radiates radiation onto the surface to be examined in a second radiation direction predetermined by a second radiation angle, wherein the first radiation angle and the second radiation angle are substantially opposite with respect to a direction perpendicular to the surface to be examined (which in particular also intersects the surface to be examined) and/or plane.

It is therefore also proposed in terms of the method that, on the one hand, the light is irradiated onto the surface in a certain direction, but on the other hand, radiation reflected from the surface in the opposite direction to this direction is also detected.

In a further method according to the invention for examining optical properties of surfaces, a first radiation device radiates radiation onto the surface to be examined in a first radiation direction characterized by a first angle of incidence, and a first radiation detection device detects radiation emitted and in particular scattered by the surface to be examined in response to the radiated radiation at a first radiation angle, and a second radiation detection device detects radiation emitted and in particular scattered by the surface to be examined in response to the radiated radiation at a second radiation angle.

According to the invention, the device has a further radiation detection device which detects radiation emitted and in particular reflected from the surface to be examined in response to the irradiated radiation under an irradiation direction characterized by a further irradiation angle, wherein the irradiation direction and the irradiation direction are substantially opposite.

Preferably, the surface examined by this method is a surface which is designed in such a way that it reflects a significant part of the radiation irradiated onto it (in particular independently of an angle of incidence) in a direction opposite to the direction of incidence.

Particularly preferably, the surface is one with reflective particles. surface with no and/or reflective pigments.

Preferably, the radiation reflected from the surface is initially reflected in the direction of the first radiation device, but preferably does not reach it but is subsequently deflected by a predetermined angle (in particular by the beam splitter device mentioned above). This angle is advantageously between 30° and 150°, preferably between 60° and 120°, preferably between 70° and 110°, preferably between 80° and 100° and particularly preferably between 85° and 95°.

Particularly preferably, the irradiation of the radiation by the first radiation device onto the surface and the reflection of the radiation in the direction opposite to the first irradiation direction take place at different time periods.

In a further preferred method, the surface to be examined is irradiated (in particular by the first radiation device) with light of different wavelengths and/or with light of different colors.

Particularly preferably, a filter arrangement is used for the purpose of irradiation with different colors, wherein (one after the other) different color filters are placed in the beam path between the radiation device and the surface.

Preferably, a filter wheel is used to irradiate the surface to be examined with different colors, which filter wheel carries a plurality of filter elements that can be optionally placed or moved into the beam path between the radiation device and the surface.

In a further preferred method, at least one spatially resolved image of the surface illuminated by the first radiation device is recorded. Preferably, at least one image of the surface illuminated by the second radiation device is recorded.

Particularly preferably, the said spatially resolved image is taken at an angle of 90° with respect to the surface. The present invention is further directed to the use of a device of the type described above and/or a method of the type described above for investigating optical surface properties of retroreflective surfaces.

Retroreflective surfaces are understood to mean in particular those surfaces which reflect a significant proportion of the radiation irradiated onto them in a direction opposite to the direction of incidence and in particular reflect a significant proportion independently of an irradiation direction (in particular an irradiation direction which deviates from an irradiation direction perpendicular to the surface by at least 10°, preferably by at least 20° and preferably by at least 30°).

A significant proportion is understood to mean a proportion which considerably exceeds the proportion of radiation scattered in this direction, i.e. is at least (in terms of intensity) twice as large, preferably at least three times as large, preferably at least five times as large, and preferably at least ten times as large.

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

In it show:

Fig. 1 is a schematic representation of a device according to the invention;

Fig. 2 is a partial view of Fig. 1 to illustrate the angles;

Fig. 3 is a representation of a filter wheel for a device according to the invention;

Fig. 4 is a representation of a beam steering device according to the invention; and

Fig. 5 shows another embodiment of the invention for an application with retroreflective surfaces.

Fig. 1 shows a representation of a device 1 according to the invention for examining the optical properties of a surface 10. This device 1 has a first radiation device 2 which emits radiation and in particular light in a first beam direction. direction R1 onto the surface 10.

The reference numeral 12 designates a first radiation detection device which detects radiation scattered by the surface 10 in response to the incident radiation at a first radiation angle b1.

The reference numeral 14 denotes a second radiation detection device which detects radiation scattered from the surface 10 in response to the incident radiation at a second radiation angle b2.

The reference numeral 16 designates a third radiation detection device which detects radiation scattered by the surface 10 in response to the incident radiation at a third radiation angle b3.

The reference numeral 17 designates a fourth radiation detection device which detects radiation scattered by the surface 10 in response to the incident radiation at a fourth radiation angle.

The reference numeral 18 designates a fifth radiation detection device which detects radiation scattered from the surface 10 in response to the incident radiation at a fifth radiation angle.

In addition, a sixth radiation detection device is provided which detects radiation scattered by the surface 10 in response to the incident radiation at a sixth radiation angle.

Preferably, this sixth radiation detection device is arranged vertically above the surface to be examined. Preferably, this sixth radiation detection device is a radiation detection device which is also suitable and intended to record a spatially resolved image of the radiation impinging on it.

The reference number 4 designates a second radiation device which radiates radiation in the second irradiation direction R2 onto the surface 10. The surface reflects this radiation in a direction opposite to the first irradiation direction and therefore in the direction of the first irradiation device 2. The reference numeral 20 designates a housing in which the individual radiation detection devices as well as the radiation devices are arranged.

The reference numeral 30 designates a filter wheel which carries a plurality of color filters which can be selectively pushed into the beam path between the first radiation device 2 and the surface.

Fig. 2 shows a partial representation of the device shown in Fig. 1. The angle of incidence a1 is shown, which characterizes the direction of incidence R1 under which the first radiation device 2 radiates radiation onto the surface 10.

In addition, the first radiation angle b1 and the second radiation angle b2 are also shown, under which the first and second radiation detection devices detect scattered radiation from the surface 10. The other radiation angles are not shown for reasons of clarity. The dashed line indicates the second radiation direction R2 under which the second radiation direction 4 (see Fig. 1) radiates radiation onto the surface 10.

Fig. 3 shows a filter wheel 30 which is used to illuminate or irradiate the surface in different colors. This filter wheel has a plurality of color filters 32, 34, 36 which can be pushed (or rotated) into the beam path between the first radiation device 2 and the surface.

Fig. 4 shows a detailed representation of the device according to the invention. The reference number 40 refers to a beam steering device. This has a housing 42. The reference number 44 designates a radiation inlet through which radiation can enter the housing in the direction R1.

The reference numeral 46 designates a radiation outlet through which radiation radiated in the radiation direction R1 can exit the housing 42.

However, this radiation output 46 also functions as a radiation input for radiation reflected from the surface 10. A beam splitter 48 directs this radiation entering through the radiation output in the direction of a second radiation output 52 and thus directs it to a further radiation detection device (shown only schematically).

Fig. 5 shows a further embodiment of a device according to the invention, which is used in particular for the examination of retroreflective surfaces. These surfaces reflect light, generally radiation, even in a direction opposite to the direction of incidence, if this direction of incidence is arbitrary and in particular is not perpendicular to the surface.

Fig. 5 thus shows a design which is similar to that shown in Fig. 4. With regard to the design of the first radiation device as well as the filter wheel, reference is made to the above explanations.

The radiation device emits radiation in the direction R1 through an opening 23 in the housing onto a surface (not shown). The radiation reflected from this surface in the direction RT opposite to the direction R1 is deflected by 90° and reaches a further radiation detection device 15.

This further radiation detection device 15 can detect at least one characteristic property of this radiation reflected in the direction R1', such as an intensity. However, it would also be possible for this further radiation detection device to record a spatially resolved image of the radiation impinging on it and/or for the further radiation detection device to be suitable and intended for this purpose.

The reference number 19 designates a control device which in particular also controls the first radiation device and the further radiation detection device. Preferably, control is carried out in such a way that the further radiation detection device receives the radiation emitted by the first radiation device in the beam direction R1 and reflected by the surface in the opposite direction.

The arrows shown in Fig. 5 illustrate several directions in which radiation scattered from the surface can be detected by radiation detection devices, as explained above. In the representation shown in Fig. 5, radiation scattered from the surface can advantageously be detected in six or seven different directions.

The reference number 21 designates a further radiation detector device or a further radiation detection device, which is also suitable and intended to record radiation emitted in the direction RT from the surface and preferably to output at least one signal which is characteristic of this radiation. This further device 21 can preferably be used for referencing.

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 with a first radiation device (2) which is suitable and intended to radiate radiation in a first radiation direction (R1) characterized by a first angle of incidence (a1) onto the surface to be examined, with a first radiation detection device (12) which is suitable and intended to detect radiation emitted and in particular scattered at a first radiation angle (b1) by the surface to be examined (10) in response to the radiated radiation, and with a second radiation detection device (14) which is suitable and intended to detect radiation emitted and in particular reflected at a second radiation angle (b2) by the surface to be examined (10) in response to the radiated radiation, characterized in that the device (1) has a further radiation detection device (15) which is suitable and intended to detect radiation emitted and in particular reflected at a radiation direction (RT) characterized by a further radiation angle To detect radiation, wherein the direction of incidence (R1) and the direction of emission (RT) are substantially opposite and/or the device (1) has a second radiation device (4) which is suitable and intended to radiate radiation in a second direction of incidence (R2) characterized by a second angle of incidence (a2) onto the surface to be examined, wherein the first angle of incidence (a1) and the second angle of incidence (a2) are substantially opposite with respect to a direction perpendicular to the surface to be examined. 2. Device (1) according to claim 1, characterized in that the device (1) has a control device which causes the radiation emitted by the first radiation device to strike the surface and the radiation emitted from the surface in response to this incident radiation hits the further radiation detection device. 3. Device (1) according to claim 1 or 2, characterized in that the second radiation device is positioned such that the radiation emitted by the second radiation device (4) is reflected by the surface to be examined in a direction opposite to the first irradiation direction (R1). 4. Device (1) according to at least one of the preceding claims, characterized in that the device has a further detection device (22) which is suitable and intended to detect radiation emitted by the second radiation device (4) and reflected by the surface. 5. Device (1) according to at least one of the preceding claims, characterized in that the device has a housing (20) within which the first radiation device (2), the first radiation detection device (12), the second radiation detection device (14) and the further radiation detection device are arranged, wherein this housing has an opening through which the first radiation device illuminates the surface to be examined (10). 6. Device (1) according to at least one of the preceding claims, characterized in that the first radiation device is suitable and intended to emit radiation in different colors, wherein the first radiation device preferably has a light source and a plurality of color filter devices which can be selectively moved into a beam path between the light source and the surface to be examined, wherein the radiation device preferably has a filter wheel which can be rotated about a predetermined axis of rotation and on which the color filter devices are arranged. 7. Device (1) according to at least one of the preceding claims, characterized in that the device (1) has a beam steering device (40) which is designed and arranged such that radiation emanating from the first radiation device strikes the surface (10) through this beam steering device (40) and that, on the other hand, radiation reflected from the surface strikes the further detector device or the further radiation detection device through this beam steering device, wherein the beam steering device preferably has a beam splitter. 8. Device (1) according to at least one of the preceding claims, characterized in that the first angle (a1) is between 40° and 50° with respect to a direction perpendicular to the surface, preferably between 42° and 48°, preferably between 43° and 47° and particularly preferably between 44° and 46° and particularly preferably at 45°. 9. Device (1) according to at least one of the preceding claims, characterized in that the device has a third radiation detection device (16) which is suitable and intended to detect radiation emitted and in particular scattered at a third radiation angle (b3) by the surface to be examined (10) in response to the irradiated radiation, and preferably the device has a fourth radiation detection device (16) which is suitable and intended to detect radiation emitted and in particular scattered at a fourth radiation angle (b4) by the surface to be examined (10) in response to the irradiated radiation. 10. Device (1) according to at least one of the preceding claims, characterized in that the device (1) has an image capture device which is suitable and intended to capture radiation emitted and in particular scattered by the surface (10) in a spatially resolved manner, wherein this image capture device is preferably arranged vertically above the surface to be examined. 11. Device (1) according to at least one of the preceding claims, characterized in that the device (1) has a further radiation detector device (..) which is suitable and intended to detect radiation emitted by the surface in the radiation direction (R1') and preferably to output at least one signal which is characteristic of this radiation. 12. Beam steering device (40) with a housing (42) and with a radiation inlet (44) through which radiation can enter the housing in a first radiation direction (R1), and with a first radiation outlet (46) through which the radiation entering through the radiation inlet (44) can exit the housing in the radiation device, characterized in that a beam splitter device (48) is arranged in the housing (42), which is suitable and intended to deflect through the radiation outlet (46) in a direction (R1') opposite to the radiation direction (R1) in a deflection direction (Q) which deviates from the radiation direction (R1) and the direction opposite the radiation direction and in particular is perpendicular to the radiation direction, wherein the housing (42) furthermore has a second radiation outlet (52) through which the radiation deflected by the beam splitter device can exit the housing (42). 13. Method (1) for examining optical properties of surfaces, wherein a first radiation device (2) radiates radiation in a first radiation direction (R1) characterized by a first angle of incidence (a1) onto the surface to be examined, and a first radiation detection device (12) detects radiation emitted and in particular scattered by the surface to be examined (10) in response to the radiated radiation at a first radiation angle (b1), and a second radiation detection device (14) detects radiation emitted and in particular scattered by the surface to be examined (10) in response to the radiated radiation at a second radiation angle (b2), characterized in that the device (1) has a further radiation detection device which, at a radiation direction (RT) characterized by a further radiation angle, from the surface to be examined (10) detects radiation emitted and in particular reflected in response to the irradiated radiation, wherein the direction of incidence (R1) and the direction of emission (R1') are substantially opposite and/or a second radiation device (4) of the device irradiates radiation onto the surface to be examined in a second direction of incidence (R2) predetermined by a second angle of incidence (a2), wherein the first angle of incidence (a1) and the second angle of incidence (a2) are substantially opposite with respect to a direction perpendicular to the surface to be examined. 14. Method according to the preceding claims, characterized in that the first radiation device illuminates the surface, in particular one after the other, with light of different wavelengths. 15. Use of a device according to at least one of the preceding claims and/or a method according to at least one of the preceding claims for examining optical surface properties of retroreflective surfaces.