Apparatus and method for measuring optical properties, in particular color measuring apparatus

Abstract

An apparatus for inspecting optical properties of a surface, comprising a housing, a first radiation device arranged in the housing and suitable and intended for emitting radiation, in particular light, onto the surface to be inspected, and a first radiation detection device arranged in the housing and suitable and intended for receiving radiation emitted onto the surface to be inspected and reflected and / or scattered by the surface, wherein the housing has an opening through which the first radiation device emits radiation onto the surface, the apparatus comprises a first calibration element which can be positioned so that radiation emitted from one radiation device onto the first calibration element and reflected and / or scattered by the first calibration element reaches the first radiation detection element, instead of the surface to be inspected and instead of the first calibration element, the apparatus comprises a second calibration element which can be positioned so that radiation irradiated from the first radiation device onto the second calibration element and reflected and / or scattered by the second calibration element reaches the first radiation detection element, instead of the surface to be inspected and instead of the first calibration element.

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for measuring optical properties, in particular for determining the optical properties of a surface. In particular, the apparatus is described with reference to a color measurement apparatus, but it is pointed out that the invention is also suitable for other apparatus for measuring or determining optical properties (of surfaces), such as gloss. [Background technology]

[0002] Calibration standards (hereafter referred to as calibration elements) are often used in color measurement devices to allow for the detection, blocking and / or correction of possible ageing changes, such as a decrease in light wave intensity. This correction is known to be performed using calibration coefficients, which ensure that the color measurements (especially the L value in laboratory systems) are always the same for the same sample, regardless of the quality of the lighting.

[0003] However, it has been shown that such measurements are often affected by dirty calibration elements, for example: dirty or damaged calibration elements can simulate illuminant aging, which does not exist in reality, and thus can corrupt measurements such as color measurements through incorrectly set calibration coefficients. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention therefore aims to provide a more accurate calibration of such devices, and in particular to eliminate and / or take into account various error sources that may affect the calibration. [Means for solving the problem]

[0005] The device according to the invention for inspecting optical properties of a surface comprises a housing and a first radiation device arranged in the housing and suitable and intended for emitting radiation, in particular light, in particular light in the visible wavelength range, for example light in the wavelength range of 300 nm to 700 nm, onto the surface to be inspected.

[0006] The apparatus further comprises a first radiation detection device disposed within the housing, the first radiation detection device being suitable and intended to receive radiation projected onto the surface to be inspected and radiation reflected and / or scattered by the surface to be inspected, and the housing further comprises an opening through which the first radiation detection device projects radiation onto the surface to be inspected.

[0007] Furthermore, the apparatus has a first calibration element that can be positioned so that radiation is irradiated from the first radiation device onto the first calibration element instead of the surface to be inspected, and radiation reflected and / or scattered by the first calibration element reaches the first radiation detection device.

[0008] According to the invention, the device has, instead of the surface to be inspected and instead of the first calibration element, a second calibration element, which can be positioned so that radiation irradiated from the first radiation device onto the second calibration element and reflected and / or scattered by the second calibration element reaches the first radiation detection device.

[0009] It is therefore proposed to use two calibration elements or two calibration standards independently of each other to perform the calibration as a whole, so that certain errors due to faulty calibration elements can be eliminated or made recognizable.

[0010] Preferably, the first and / or second calibration element has a white surface facing the radiation device, which is particularly preferably a predetermined white standard, which preferably has, in addition to the property of being "white", also a gloss level suitable for gloss calibration.

[0011] For example, the surface of the calibration element can be made of ceramic, or other materials can be used that are stable and / or color stable and preferably resistant to aging.

[0012] In a preferred embodiment, the calibration element is arranged on a holder. Particularly preferably, the first and / or second calibration element is permanently arranged in the housing. However, it is also conceivable that the first and / or second calibration element is arranged outside the housing, for example on a (particularly pivotable) support arm.

[0013] Preferably, the first and / or second calibration element is movable, in particular swivellable, in the beam path between the radiation device and the detection device. Particularly preferably, the calibration element is arranged in a holder. Particularly preferably, the holder is designed to absorb light and / or is made of a light-absorbing material.

[0014] In a preferred embodiment, the first and / or second calibration elements may be positioned so that the surface irradiated by the radiation device is coincident with or parallel to the surface being inspected. For example, the first calibration element within the housing may be pivoted to a position where its surface is parallel to the surface of the surface being used or inspected during operation.

[0015] Preferably, the second calibration element can be placed in the opening, and therefore preferably at the position where the surface to be analysed in the measurement mode is located.

[0016] In a preferred embodiment, the device is provided with a closing device, in particular a shutter cleaning device, suitable and intended to close the opening during certain periods, in particular during periods when no measurements are being taken or when the device is switched off, in order to prevent contamination from entering the device and / or the housing when not in operation.

[0017] In a further preferred embodiment, the radiation detection device is suitable and intended to record spatially resolved images of the surface to be inspected.

[0018] In a further embodiment, the radiation detection device is suitable and intended to measure the intensity of radiation incident thereon.

[0019] In a further preferred embodiment, the radiation detection device is suitable and intended to perform wavelength resolution of the radiation incident on it, in other words, the radiation detection device allows analysing the radiation incident on it with respect to its wavelength and / or outputting wavelength-dependent measurement results.

[0020] Particularly preferably, the radiation detection device allows a wavelength-dependent analysis of the radiation incident on it, especially in the visible wavelength range.

[0021] The radiation detection device is particularly preferably a spectrometer device.

[0022] Particularly preferably, the device has a holding device or holding volume for holding one of the calibration elements. Particularly preferably, the device has a holding compartment or holding volume for holding both calibration elements. Preferably, the two calibration elements are stored separately from each other.

[0023] In a further preferred embodiment, the two calibration elements are stored in different orientations, in particular with respect to the orientation of said opening through which the surface to be inspected is illuminated in working mode. In this way, a space-saving arrangement can be achieved.

[0024] Particularly preferably, a second calibration element can be removed from the receiving volume and placed in an opening of the device, for example to perform a calibration measurement.

[0025] In a particularly preferred embodiment, the interior surface of the housing is light absorbing, for example black.

[0026] In a further advantageous embodiment, the device has a processor device that determines a measurement value, in particular a calibration value, from the values ​​output by the radiation detection device. Particularly preferably, the processor device can use the calibration value for this purpose. Particularly preferably, the calibration value is or can be stored in a memory device of the device. Particularly preferably, this calibration value is changeable, in particular changeable as a result of a calibration measurement.

[0027] Particularly preferably, one calibration element can be arranged in the housing, preferably movable within the housing in the beam path between the first radiation device and the first radiation detection device, and particularly preferably, this one calibration element can be arranged relative to the opening from the inside.

[0028] In a further advantageous embodiment, the device has a processor device for detecting a first value characteristic of a first calibration measurement by a first calibration element and a second value characteristic of a second calibration measurement by a second calibration element, and preferably the device has a comparison device for comparing the first value and the second value with each other.

[0029] Particularly preferably, the comparison of the first value with the second value can be used to draw conclusions about a fault state of the device and / or the calibration element. Particularly preferably, the first value and the second value are comparative values. In a preferred embodiment, this comparison can be used to infer sources of error in the context of a calibration measurement.

[0030] In a further preferred embodiment, the device comprises an output and / or display device suitable and intended for outputting at least one signal that is characteristic of a particular error, for example, a display may indicate that one of the calibration elements is dirty or that a calibration element is not properly positioned.

[0031] The display device is particularly preferably a display, which is particularly preferably integrated into the housing of the device, and which is particularly preferably suitable and intended for alphanumeric output of information.

[0032] For example, in order to be able to recognize without doubt that the calibration coefficients may be correctly changed by a white standard calibration, it is proposed that the recorded measurement variables are correlated with each other and clear statements regarding the state of the device, e.g., the spectrophotometer and / or the calibration elements, are derived from this.

[0033] It is proposed here to use two calibration elements: preferably an external calibration element, which is placed in the measurement opening like the sample to be measured, and preferably an internal calibration element, which is integrated into the sealing cap and closes the measurement opening, preferably electrically, when no measurements are being taken.

[0034] Particularly preferably, the at least one calibration element is integrated into a closing device for closing an opening through which the surface to be inspected is illuminated in the working mode.

[0035] It is particularly preferred that the calibration coefficients are determined separately for both calibration elements.

[0036] Preferably, the device is selected from the group of devices comprising a color measuring device, a gloss measuring device, an orange peel measuring device, etc. Particularly preferred is a color measuring device.

[0037] Particularly preferably, the device has a second radiation device arranged in the housing, which radiation device is suitable and intended for emitting radiation, in particular light, onto the surface to be inspected.

[0038] Particularly preferably, this radiation, or the reflected and / or scattered radiation (from the surface to be inspected) resulting from this radiation, is also detected by the above-mentioned detection device.

[0039] Particularly preferably, the second radiation device is arranged to irradiate the surface at a different angle to the first radiation device described above, for example the first radiation device could irradiate the surface at an angle of e.g. 60° or 45° and the second radiation device could irradiate the surface at an angle of 20°.

[0040] Preferably, the at least one radiation device emits radiation onto the surface at an angle between 30° and 60° relative to the surface, preferably between 40° and 50°. Preferably, the at least one radiation device irradiates the surface with radiation at an angle between 10° and 30° relative to the surface, preferably between 15° and 25°.

[0041] Preferably, these radiations are illuminated or directed towards the detector by a calibration element.

[0042] In a further advantageous embodiment, the device also comprises a second detector, i.e. a second radiation detector, for detecting radiation incident thereon, which in particular can be arranged at a different angle to the surface than the first radiation deflection device described above.

[0043] Particularly preferably, the apparatus comprises a plurality of radiation devices, each radiation device being suitable and intended for irradiating the surface to be inspected with light, which may for example be a plurality of light sources, which particularly preferably partially emit white light, and particularly preferably at least partially emit light of different colors and / or wavelengths.

[0044] Radiation devices can have a variety of emission characteristics, such as directional illumination, illumination within a given angular acceptance range, or diffuse illumination.

[0045] It is particularly preferred that the plurality of radiation devices are arranged along a circular line, which particularly preferably runs parallel to the surface to be analysed.

[0046] Particularly preferably, the radiation detection device is arranged substantially perpendicularly above the surface to be inspected, in particular the direction in which it picks up radiation from the surface is substantially perpendicular to the surface.

[0047] Particularly preferably, the apparatus also comprises a gloss measuring device (and / or a reflection measuring device), wherein the gloss measuring device, in particular the radiation device of the gloss measuring device, preferably emits light onto the surface at a predetermined angle, and the detection device detects light from a corresponding reflection angle.

[0048] This gloss measurement device can also be used to evaluate calibration. Operating the device with the measurement aperture facing upwards can contaminate the optics in very dusty environments, even if the measurement aperture is closed with a shutter or similar. However, small gloss angles, such as 20°, are more susceptible to this than larger gloss angles, such as 60°.

[0049] If only one gloss angle is measured, the gloss value of the first calibration element can be related to the gloss value of the second calibration element using a calibration factor. As will be shown in more detail below, different conclusions can be drawn from appropriate combinations of observations.

[0050] For example, if the 20° gloss of an internal calibration element deviates significantly from the original calibrated gloss value, but the 60° gloss remains almost unchanged, this indicates that the optical element is contaminated.

[0051] In a further advantageous embodiment, the apparatus comprises a gloss measuring device which comprises a further radiation device for irradiating radiation onto the surface at a predetermined angle of incidence, and the gloss measuring device also comprises a further radiation detection device for detecting radiation irradiated onto the surface by the further radiation device and reflected from the surface at the predetermined angle, the angle of incidence and the further angle being preferably the same.

[0052] The present invention further provides a method for inspecting the optical properties, in particular the color properties, of a surface, wherein a radiation device arranged in a housing irradiates radiation, in particular light, onto the surface to be inspected and a first radiation detection device arranged in the housing receives the radiation that is irradiated onto the surface to be inspected and that is reflected and / or scattered by the surface (and / or that strikes the radiation detection device), characterized in that the housing has an opening through which the first radiation device irradiates the surface, and the device has a first calibration element that is arranged in calibration mode in place of the surface to be inspected so that the radiation that is irradiated onto the first calibration element by the first radiation device and that is reflected and / or scattered by the first calibration element reaches the first radiation detection device.

[0053] According to the invention, a second calibration element is placed in calibration mode in place of the surface to be inspected and the first calibration element such that radiation is irradiated onto the second calibration element by the first radiation device and the radiation reflected and / or scattered by the second calibration element reaches the first radiation detection device.

[0054] It is therefore also recommended to carry out different measurements, in particular at least two measurements using different calibration elements, which can be used to draw conclusions about different sources of error.

[0055] Preferably, the calibration factor is modified based on at least one calibration measurement performed, in particular when the calibration measurement indicates that deviations in the measurements are due to changes in the optical properties of the radiation device, in particular to take into account and / or compensate for ageing of the at least one radiation device.

[0056] A first value characteristic of a first calibration measurement with a first calibration element and a second value characteristic of a second calibration measurement with a second calibration element are recorded with particular priority.

[0057] Particularly preferably, the first value and the second value are compared with one another and particularly preferably, in view of this comparison, an indication or information regarding the error is issued to the user.

[0058] Preferably, the first and second values ​​are mathematically related to each other. Therefore, it is possible to form a difference between the first and second values. However, it would also be possible to form a quotient between the first and second values. It is particularly preferred to form both the difference between the first and second values ​​and the quotient between the first and second values. For example, it can be determined which of the two values ​​is larger. This can be used to draw conclusions regarding possible error states of the device and / or the calibration element. Furthermore, the ratio can be used to determine whether the two values ​​are approximately the same or significantly different from each other.

[0059] In another preferred method, further measurements are also determined, in particular the measured gloss value (especially at a specific angle of incidence). The gloss measurement is preferably carried out in so-called gloss units, as detailed in current standards (e.g., ISO 2813 or ASTM D 253). Preferably, this measured gloss value is compared with a predetermined value, for example, an initial value.

[0060] It can be determined whether the measured value is approximately equal to the initial value, deviates from the initial value, or is particularly small. This gloss value measurement can be used for both the first calibration element and the second calibration element.

[0061] It is particularly preferred to take into account the above determined values ​​or analyses to draw conclusions regarding the fault state of the device, the fault state of the calibration element, the fault state of the optical device. The table below shows a corresponding list of the various error sources:

[0062] It is particularly preferred that the above comparison distinguishes between different sources of error.

[0063] It is particularly preferred to modify the calibration value taking into account at least one of the measured values, which can be seen in particular in the table above. [Table 1]

[0064] The table above shows four cases of errors or conditions, numbered 1 through 4 at the top.

[0065] The second row shows the possible measurement results of the calibration coefficient ca_i of the first calibration element (specifically the calibration element located inside the housing during the calibration measurement), which is either greater than 1 (indicating an error condition) or approximately equal to 1 (indicating the target condition).

[0066] The third row shows the possible measurement results of the calibration coefficient ca_a of the second calibration element (specifically, the calibration element located outside the housing during the calibration measurement), which is either greater than 1 (indicating an error condition) or approximately equal to 1 (indicating the target condition).

[0067] The fourth row shows the ratio between the measured calibration coefficients ca_i and ca_a. If this ratio is approximately 1, i.e. the two calibration coefficients are approximately equal, this indicates the target state regarding the contamination of the two calibration elements, especially the second calibration element. If this ratio ca_i / ca_a is less than 1, this indicates that the outer calibration element is contaminated (see the third column and the penultimate row of the table).

[0068] In line 5, the measured gloss value gi (and / or the measured reflectance value) is determined using a first calibration element at an angle of incidence of 20°. In line 6, the measured gloss value ga (and / or the measured reflectance value) is determined using a second calibration element at an angle of incidence of 20°.

[0069] These determined gloss measurements are preferably compared with the respective initial measurements gloss_i0 and gloss_e0. If both values ​​deviate (second column), this indicates that the optics is dirty. If only the value of the second calibration element deviates, this indicates that the element is dirty or has not been applied correctly to the aperture.

[0070] Optionally, the gloss measurement can be performed at a second angle, for example 60°.

[0071] In another preferred method, the surface to be inspected is irradiated in working mode by a plurality of radiation devices. Preferably, the surface to be inspected is irradiated by at least two radiation devices. Particularly preferably, these two radiation devices irradiate at least two different angles. Particularly preferably, the irradiation by a first radiation device is offset in time with respect to the irradiation by a second radiation device.

[0072] In a further preferred embodiment, the radiation detection device detects radiation incident on it as a function of wavelength.

[0073] The radiation detection device is particularly preferably a spectrometer. Particularly preferably, the radiation detection device outputs a value characteristic of a specific wavelength. Particularly preferably, this value is output both during measurement on the surface to be analyzed and during calibration.

[0074] In a further preferred method, at least one calibration (note that the terms calibration and calibration are used interchangeably herein) is used to determine and take into account the ageing state of at least one radiological device.

[0075] In another preferred method, the surface to be analyzed is illuminated with light of different wavelengths and / or with white light.

[0076] In another preferred method, the surface to be analyzed is illuminated from at least two different angles of incidence.

[0077] In another preferred method, at least one color measurement is essentially constant for the same sample at all times, regardless of the quality of the illumination. [Brief explanation of the drawings]

[0078] Further advantages and embodiments are shown in the enclosed drawings.

[0079] Shows the following:

[0080] [Figure 1] a perspective view of the device according to the invention; [Figure 2] View of the inside of the device through the measurement opening; [Figure 3] Internal view of the device according to the invention; [Figure 4] 10 is a further internal view of the device according to the invention; [Figure 5] 1 is a further internal view of the device according to the present invention; and [Figure 6] Further internal views of the device according to the invention DETAILED DESCRIPTION OF THE INVENTION

[0081] 1 shows an external view of an apparatus 1 according to the invention for inspecting the optical properties of a surface. The apparatus 1 comprises a housing 10. Furthermore, the housing has a receiving opening 38 or receiving volume for receiving a second calibration element 16 (external calibration element), which receiving opening 38 or receiving volume serves in particular to accommodate the second calibration element 16 (external calibration element).

[0082] This external calibration element 16 is here arranged on a pivot flap 36. Reference number 30 denotes a display device which can display, for example, measured values ​​or error states. Reference number 22 denotes an opening through which the color and / or other optical properties, such as gloss value, of the surface to be inspected (not shown) can be inspected. Preferably, light can only enter the interior of the housing 30 via this opening 22.

[0083] In the embodiment shown in Figure 1, the device comprises a pressure device 35 having a pivoting arm 32 on which a pressure element 34 is arranged for pressing the sample against the opening 22. The pressure device 35 can be stored or lowered into a recess 36 in the housing. In one embodiment, a first calibration element can be arranged on the sealing device 35. Preferably, however, a second calibration element is arranged inside the housing 10.

[0084] 2 shows a view into the housing through opening 22. In particular, this is a vertical view, e.g., from above, through measurement opening 22. Here, the optical block of the color measurement device can be seen, which preferably also includes a quantitative fluorescence measurement device and / or a gloss measurement device.

[0085] Here, a number of first radiation devices or light sources 2a, 2b, 2c are provided, more precisely ten. Each of these is a white light LED and is used to illuminate the color measurement. These light sources 2a, 2b, 2c are preferably positioned so that they illuminate the surface to be analyzed at a 45° angle.

[0086] The references 2d, 2e, and 2f refer to numerous other light sources that specifically project colored light onto the surface. This can be achieved by using colored light LEDs. However, it is also possible and preferable to use white light LEDs at this point, albeit with narrow-band filtering. Monochrome LEDs additionally equipped with narrow-band filters, whose bandwidth is narrower than the natural bandwidth of the monochrome LEDs, can also be considered as a further lighting option.

[0087] Particularly preferably, these light sources 2d, 2e, 2f emit light of different wavelengths, particularly in the wavelength range of 300 to 660 nm.

[0088] Reference number 4 denotes a radiation detection device, in particular a spectrometer, suitable and intended to record light from the irradiating devices 2a to 2f or reflected light from a surface (not shown).

[0089] Reference number 12 denotes a preferably available second radiation device, which also serves to irradiate the surface to be inspected (not shown) with light. This light is reflected by the surface and can thus reach the second radiation detection device 13. Preferably, the second radiation device and the second radiation detection device 13 form a gloss measurement device.

[0090] Figure 3 shows an internal view of the apparatus described herein, showing a first internal calibration element 6, which is arranged on a holder 62 and is pivotable about a pivot axis S between a position not in the beam path (position shown in Figure 3) and a position inwardly relative to the aperture 22 (Figure 4).

[0091] Reference number 41 denotes a tubular element capable of directing radiation to a radiation detection element (not shown), and reference number 45 denotes optical means such as a lens used to focus the radiation impinging on the radiation detection device.

[0092] The reference number 52 identifies a housing portion adjacent to the opening 22. This housing portion is particularly radiation-absorbent and is particularly black in color.

[0093] Reference number 32 indicates generally a processor unit which is used in particular to control the device 1 and to determine or modify the calibration coefficients. Reference number 34 indicates a memory unit which is used in particular to store the calibration coefficients.

[0094] FIG. 4 is an illustration of the device according to the invention, in which the first calibration element 6, ie the internal standard, has been pivoted into a position in which a calibration can be performed.

[0095] Reference numeral 27 denotes an optical block in which the radiation devices 2a to 2c and further 2d to 2f are arranged.

[0096] 5 is a further illustration of the device according to the invention, showing the radiation detection device 4 and the flow path 41 through which the radiation is guided to the radiation detection device 4. Furthermore, the opening 22 is again shown, which is now closed and the first calibration element 6 faces downwards, i.e. towards the radiation detection device 4.

[0097] Figure 6 is a bottom view of the device shown in Figure 5. Here, a further radiation detection device 13 is shown, which is used in particular for gloss measurements. The first radiation detection device 4 is also shown again.

[0098] The applicant reserves the right to claim that all features disclosed in the application documents are essential to the invention, provided that they are novel, individually or in combination, over the prior art. It should also be noted that the individual figures also depict features that may be advantageous in their own right. Those skilled in the art will readily recognize that a particular feature depicted in a figure may be advantageous even without adopting additional features from that figure. Furthermore, those skilled in the art will recognize that advantages may also arise from the combination of several features depicted in individual figures or in different figures.

Claims

1. An apparatus (1) for inspecting optical properties of a surface, comprising a housing (10), a first radiation device (2a, 2b, 2c) arranged in the housing (10) and suitable and intended for emitting radiation, in particular light, onto the surface to be inspected, and a first radiation detection device (4) arranged in the housing (10) and suitable and intended for receiving radiation emitted onto the surface to be inspected and reflected and / or scattered by the surface, wherein the housing (10) has an opening (22) through which the first radiation device (2a) emits radiation onto the surface, and the apparatus comprises a first calibration element (6) which can be arranged so that radiation emitted from the first radiation device (2a) onto the surface instead of the surface to be inspected and reflected and / or scattered by the first calibration element reaches the first radiation detection device (4), The apparatus is characterized in that, instead of the surface to be inspected and instead of the first calibration element (6), it comprises a second calibration element (16) which can be positioned so that radiation irradiated from the first radiation device (2a) onto the second calibration element (16) and reflected and / or scattered by the second calibration element reaches the first radiation detection device (4).

2. 2. A device (1) according to claim 1, The apparatus is characterized in that one of the calibration elements (6) can be arranged in a housing (10) and is preferably movable within the housing into the beam path between the first radiation device (2a) and the first radiation detection device (4).

3. A device (1) according to at least one of the preceding claims, The apparatus (1) comprises a processor unit for detecting a first value characteristic of a first calibration measurement by a first calibration element (6) and a second value characteristic of a second calibration measurement by a second calibration element (16), and preferably further comprises a comparison unit for comparing the first value with the second value.

4. A device (1) according to at least one of the preceding claims, The device (1) is selected from a group of devices (1) including a color measuring device, a gloss measuring device, an orange peel measuring device, etc.

5. A device (1) according to at least one of the preceding claims, The device (1) comprises a second radiation device (12) arranged in the housing, the second radiation device being suitable and intended for emitting radiation, in particular light, onto the surface to be inspected.

6. A device (1) according to at least one of the preceding claims, The apparatus comprises a gloss measuring device (12, 13), which comprises a further radiation device for irradiating radiation onto the surface at a predetermined angle of incidence, and which further comprises a further radiation detection device for detecting radiation irradiated onto the surface by the further radiation device and reflected from the surface at the predetermined angle, wherein the angle of incidence and the further angle are preferably the same.

7. A method for inspecting optical properties of a surface, comprising: a radiation device (2a) arranged in a housing, emitting radiation, in particular light, onto the surface to be inspected; a first radiation detection device (4) arranged in a housing (10), receiving radiation irradiated onto the surface to be inspected and reflected and / or scattered by the surface; the housing (20) having an opening through which the first radiation device (2a) emits radiation onto the surface; and the device having a first calibration element (6) arranged in a calibration mode such that radiation emitted by the first radiation device (2a) instead of the surface to be inspected and reflected and / or scattered by the first calibration element reaches the first radiation detection device (4); characterized in that:

1. A method according to claim 1, wherein in a calibration mode, instead of the surface to be inspected and instead of the first calibration element (6), a second calibration element (16) is arranged such that radiation emitted from the first radiation device (2a) onto the second calibration element (16) and reflected and / or scattered by the second calibration element reaches the first radiation detection device (4).

8. 1. A method according to any preceding claim, comprising: characterized in that: A method characterized in that a first value (ca_i) characteristic of a first calibration measurement using a first calibration element (6) is recorded, and a second value (ca_a) characteristic of a second calibration measurement using a second calibration element (16) is recorded.

9. 1. A method according to any preceding claim, comprising: A method characterized in that the first value (ca_i) and the second value (ca_a) are compared with each other and, preferably taking into account this comparison, an indication or information regarding the error is output to a user.

10. 10. A method according to at least one of the preceding claims, comprising: A method, characterized in that the calibration values ​​are changed taking into account at least one value.

11. 10. A method according to at least one of the preceding claims, comprising: A method characterized in that in a working mode the surface to be inspected is exposed to a plurality of radiation devices.

12. 10. A method according to at least one of the preceding claims, comprising: A method characterized in that the radiation detection device (4) detects the radiation incident on it as a function of wavelength.

13. 10. A method according to at least one of the preceding claims, comprising: A method, characterized in that at least one calibration is used to determine and / or take into account an aging state of at least one radiological device.

14. 10. A method according to at least one of the preceding claims, comprising: A method characterized in that the surface to be inspected is illuminated with light of different wavelengths and / or with white light.

Images