Method and Apparatus for Determining a Layer Thickness of a Layer Applied to a Substrate

Abstract

A method for determining a layer thickness of a layer applied to a substrate, in particular a coating layer, in which at least one surface area of the coated substrate is heated by irradiation with at least one radiation source and/or inductively, and thermal radiation emitted from the at least one surface area is detected by a detection device. Expediently, the layer thickness is determined based on the emitted thermal radiation. The at least one surface area is irradiated by the at least one radiation source and heats up and/or is inductively heated. Heat radiation emitted from the surface area is characteristic for a certain layer thickness and is detected by the detection device and transmitted to the evaluation device. Furthermore, the invention relates to an apparatus for determining a layer thickness of a layer applied to a substrate.

Claims

1. A method for determining a layer thickness of a layer applied to a substrate, in particular a coating layer, in which at least one surface area of the coated substrate is heated by irradiation with at least one radiation source and/or inductively heated, and thermal radiation emitted from the at least one surface area is detected by a detection device (8-8g), characterized in that the layer thickness is determined based on the emitted thermal radiation.

2. The method according to claim 1, characterized in that the at least one surface area is irradiated with a monochromatic and/or coherent radiation source or with electromagnetic radiation of a certain wavelength range, preferably between 200 nm and 15 μm, in particular between 200 and 750 nm, between 800 and 3500 nm or between 4 and 13 μm.

3. The method according to claim 1, characterized in that the at least one surface area is irradiated with several identical or different radiation sources.

4. The method according to claim 1, characterized in in that the at least one surface area is irradiated with a plurality of radiation sources, each of which is designed to generate electromagnetic radiation of a specific wavelength range or a specific wavelength.

5. The method according to claim 1, characterized in that the irradiation of the at least one surface area is periodically modulated, in particular with a frequency between 0.01 and 2000 Hz, preferably between 20 to 800 Hz.

6. The method according to claim 1, characterized in that several, preferably adjacent surface areas are successively irradiated by the at least one radiation source, and by means of an evaluation device, a preferably graphically displayable layer thickness profile of a surface to be measured is established.

7. The method according to claim 1, characterized in that the at least one surface area has a size, in particular a diameter, between 0.2 μm and 200 cm, preferably between 1 and 20 μm or between 0.2 and 2 cm.

8. The method according to claim 1, characterized in that the at least one surface area is oblique or parallel to a surface normal.

9. The method according to claim 1, characterized in that the coated substrate is preheated before the beginning of irradiation and/or induction heating.

10. An apparatus for determining a layer thickness of a layer applied to a substrate, in particular a coating layer, characterized in that the device comprises at least one radiation source for heating at least one surface area by irradiation and/or a device for inductively heating the at least one surface area, at least one detection device for detecting thermal radiation emitted from the at least one surface area, and an evaluation device for determining a layer thickness.

11. The apparatus according to claim 10, characterized in that the substrate and/or the layer is/are formed from an electrically conductive, in particular metallic, material and/or comprise an electrically conductive, in particular metallic, material and can be inductively heated.

12. The apparatus according to claim 10, characterized in that the at least one radiation source comprises at least one superluminescent diode, at least one light-emitting diode (LED), at least one polariton laser, at least one thermal radiator and/or at least one quantum cascade laser, and in particular is/are arranged for periodically irradiating the at least one surface area.

13. The apparatus according to claim 10, characterized in that the detection device comprises an IR camera or/and a bolometer camera.

14. The apparatus according to claim 10, characterized in that the detection device is designed for simultaneous or successive detection of several surface areas.

15. The apparatus according to claim 10, characterized in that the at least one radiation source, the device for inductive heating and/or the detection device are movably and is or are arranged to be passed by a plurality of, in particular adjacent surface areas.

16. The apparatus according to claim 10, characterized in that the at least one radiation source, the means for inductive heating and/or the detection device is or are arranged in a stationary manner and a conveying means is provided, which is arranged to guide the coated substrate with the surface areas to be heated past the radiation source, the device for inductive heating and/or the detection device in such way that a heating and a detection of radiation emitted from the at least one surface area can take place.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 A first embodiment of a method according to the invention and an apparatus according to the invention, schematically represented, in a perspective view,

[0040] FIG. 2 a second embodiment of a schematically illustrated apparatus according to the invention in a perspective view,

[0041] FIG. 3 another embodiment of a schematically illustrated apparatus in a perspective view,

[0042] FIG. 4 a fourth embodiment of a schematically illustrated apparatus in a perspective view,

[0043] FIG. 5 a further embodiment of a schematically illustrated device in a perspective view,

[0044] FIG. 6A-6B a sixth embodiment of a schematically illustrated apparatus in a perspective view,

[0045] FIG. 7 a further embodiment of a schematically illustrated apparatus in a perspective view,

[0046] FIG. 8 a further embodiment of a schematically illustrated apparatus in a side view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] An apparatus (1) for determining a lacquer layer (3) applied to a cell phone protective shell (2), shown schematically in a perspective view in FIG. 1, comprises a radiation source (5) having a plurality of light-emitting diodes (LEDs) (4) in the IR range, whose irradiation cone (6), shown schematically with dashed lines, is provided for irradiating a lacquer surface (7) facing the light source (5). Although a pulse-like irradiation of the lacquer surface (7) is conceivable, periodic irradiation with a frequency of 200 Hz is preferred in this embodiment.

[0048] Furthermore, the apparatus (1) comprises a detection device (8), which is designed as a bolometer camera and which can detect the entire paint surface (7). A detection area (9) is represented by a double-dotted, single-dashed line and, in comprises the entire lacquer surface (7) in this embodiment. Each pixel of the bolometer camera (8) generates a measurement signal, i.e. a temperature profile over time in a single measurement point (10, 11, 12) on the lacquer surface (7). For reasons of clarity, FIGS. 1 to 6 each show three measuring points (10-12) as examples.

[0049] An evaluation device (13) uses the measurement signal to determine a thickness of the lacquer layer (3) applied to the cell phone protective shell (2) at the respective measurement point (10-12). For this purpose, calibration curves are stored in the evaluation device (13) which can be used to assign a coating thickness at the measuring point to a measurement signal for the respective measuring point (10-12).

[0050] Furthermore, the evaluation device (13) is connected to a screen (14) on which a single measured value or a coating thickness profile, i.e. a coating thickness distribution over several measuring points, can be displayed.

[0051] It is particularly advantageous if threshold values for a coating layer thickness are stored in the evaluation device (13) and the coating thickness profile is displayed in color, for example by displaying surface areas that are coated too thickly in yellow, those that are coated too thinly in red, and those that lie within a required coating thickness range in green. Advantageously, surface areas coated too thinly or too thickly can be quickly detected by an operator of the apparatus (1).

[0052] Although the detection device (8) in this embodiment is designed as a bolometer camera, it is conceivable to design it as an IR camera or other sensor array for detecting thermal radiation.

[0053] Although it is furthermore conceivable that the device (1) is movable in three dimensions, in this and the following embodiments it is movable in two dimensions in the direction of arrows (15, 16) vertically and horizontally, with a distance to the surface areas preferably being constantly 10 cm.

[0054] It is also conceivable that an assembly comprising a radiation source (5), detection device (8) and/or evaluation device (13) is arranged in a stationary manner and a cell phone protective shell (2) is moved past to determine a lacquer layer thickness. This can be done either manually by an operator of the apparatus or mechanically.

[0055] Reference is now made to FIG. 2, where identical or equal-acting parts are designated with the same reference number as in FIG. 1 and the letter a is added to the respective reference number.

[0056] An apparatus (1a) schematically shown in FIG. 2 comprises a radiation source (5a) having a superluminescent light-emitting diode (4a), which is provided for pulse-like or periodic irradiation of a lacquer surface (7a) with light of a wavelength range of 500 to 800 nm at a frequency of 150 Hz.

[0057] Reference is now made to FIG. 3, where identical or equal-acting parts are designated with the same reference number as in FIGS. 1 and 2, and the letter b is added to the respective reference number.

[0058] An apparatus (1b) shown in a schematic view in FIG. 3 is provided for determining the thickness of a powder coating (3b) applied to a metallic component (2b). In this example, heating of a coating surface (7b) is performed by irradiation with a radiation source (5b) and inductively by an induction device (18) mounted on a side (17) of the component (2b) facing away from a detection device (8b). In this embodiment, the detection device (8b) is designed as a bolometer camera that can detect a powder coating surface (7b). An exclusively inductive heating of the coating surface (7b) is conceivable.

[0059] Reference is now made to FIG. 4, where identical or equal-acting parts are designated with the same reference number as in FIGS. 1, 2 and 3, and the letter c is added to the respective reference number.

[0060] An apparatus (1c) shown in FIG. 4 differs from those shown in FIGS. 1 to 3 in that two radiation sources (5c, 19) different from each other are provided to irradiate a lacquer surface (7c). In this embodiment, a first radiation source (5c) comprises a plurality of blue light-emitting diodes (4c), and a second radiation source (19) comprises a thermal radiator (20) having an irradiation cone (21) that irradiates the entire lacquer surface (7c).

[0061] Reference is now made to FIG. 5, where identical or equal-acting parts are designated with the same reference number as in FIGS. 1 to 4, and the letter d is added to the respective reference number.

[0062] An apparatus (1d) for determining a coating thickness of a coating (3d) shown in FIG. 5 differs from those shown in FIGS. 1 to 4 in that not the entire coating surface (7d) is irradiated, but individual, discrete surface areas (22, 23, 24, 25). The surface areas (22-25) are successively irradiated by a laser (4d) of a radiation source (5d) once or periodically for heating, and emitted thermal radiation is detected by a detection device (8d). Although a size of an excitation spot, i.e. a diameter of a laser beam irradiating the surface (7d) in the respective surface area (22-25), corresponds to the size of the preferably round irradiated surface area (22-25), it is conceivable that a measurement spot is smaller than the excitation spot. An evaluation device (13d) determines the layer thickness of the coating (3d) for each individual surface area (22-25) and can either display thickness values on a display screen (14d) or determine and display a layer thickness profile of the coating surface (7d) by interpolation and extrapolation of the layer thickness values of the surface areas (22-25).

[0063] Reference is now made to FIG. 6, where identical or equal-acting parts are designated with the same reference number as in FIGS. 1 to 5, and the letter e is added to the respective reference number.

[0064] An apparatus (1e) shown in FIG. 6a differs from those shown in FIGS. 1 to 5 in that a beam path of a radiation source (5e) and that of a detection device (8e) are parallel in sections. For this purpose, the radiation source (5e) for irradiating a surface (7e) and a detection device (8e) are arranged perpendicular to each other. Light from the radiation source (5e) is deflected by a dichroic beam splitter (26) in the direction of a surface (7e), while thermal radiation emitted by heating the surface (7e) can pass through the beam splitter (26) in the direction of the detection device (8e). Advantageously, this embodiment enables accurate determination of the layer thickness regardless of a distance between the radiation source (5e) and the surface (7e). Although in this embodiment a determination of the layer thickness takes place in certain surface areas (22e-25e), it is conceivable that the entire surface (7e) is irradiated.

[0065] In addition, it is conceivable that a beam splitter (26) shown in FIG. 6b is designed as a perforated mirror in which light from a radiation source passes through a hole in the perforated mirror and emitted thermal radiation is deflected by a reflective part of the perforated mirror in the direction of a detection device. A hole mirror is particularly advantageous when a laser or a radiation source with high spatial coherence such as a superluminescent diode is used as the radiation source (5e).

[0066] Reference is now made to FIG. 7, where identical or equal-acting parts are designated with the same reference number as in FIGS. 1 to 6, and the letter f is added to the respective reference number.

[0067] An apparatus (1f) shown in FIG. 7 differs from those shown in FIGS. 1 to 6 in that the apparatus (1f) is set up to determine a layer thickness of a coated coil (2f).

[0068] A radiation source (5f) irradiates—pulse-like or periodically modulated—a narrow surface area (27) of the coated coil (2f) moving past the apparatus (1f) in the direction of an arrow (28) extending parallel to a direction of movement of the coil (2f). A conveying means not shown in FIG. 7, which can comprise a reel, for example, can be provided for moving the coil (2f).

[0069] A stationary detection device (8f) detects radiated heat of the narrow, moving surface area (27) and determines an average layer thickness from several determined layer thicknesses by averaging.

[0070] Reference is now made to FIG. 8, where identical or equal-acting parts are designated with the same reference number as in FIGS. 1 to 7, and the letter g is added to the respective reference number.

[0071] An apparatus (1g) shown in a side view in FIG. 8 differs from those shown in FIGS. 1 to 7 in that a radiation source (5g) is provided to form an irradiation cone (6g) whose rays irradiate a coating surface (7g) obliquely to a normal (29). Since a time delay with which thermal radiation is emitted is independent of an angle of incidence of excitation radiation of a radiation source on a coating surface (7g), perpendicular incidence of rays of the irradiation cone (6g) is not required for determining a coating thickness. Advantageously, the method according to the invention can be used to determine a coating thickness on curved, coated substrates such as car body attachments, laptop housings, cell phone housings or cell phone protective covers without repetitive realignment of the radiation source (5g), a device for inductive heating and/or the detection device (8g).

[0072] It is conceivable that an apparatus (1-1g) is movable and preferably attached to an industrial robot. This allows several surface areas (7; 7a; 7b; 7c; 22-25; 22e-25e; 27; 7g) to be detected in succession in an automated manner.

[0073] It is also conceivable that an optical system, which may comprise a lens for example, is introduced into a beam path formed by an irradiation cone (6-g).

[0074] Furthermore, a surface area (22-25; 22e-25e; 27) heated inductively or by irradiation may have a smaller size than a size of the irradiation cone (6-g) incident on the surface (7; 7a; 7b; 7c; 7g), or may be at most the same size.