WO2022189327A1

WO2022189327A1 - Iterative method for determining the surface shape of a sheet- or layer-like object with high measurement accuracy

Info

Publication number: WO2022189327A1
Application number: PCT/EP2022/055688
Authority: WO
Inventors: Michael Balduin; Günther SCHALL; Ildar KHISAMITOV; Anton Lord; Eugen NEU
Original assignee: Saint-Gobain Glass France
Priority date: 2021-03-12
Filing date: 2022-03-07
Publication date: 2022-09-15
Also published as: CN115349076A

Abstract

The present invention relates to a method for determining the surface shape of a sheet- or layer-like object (1, 2, 3, V), wherein the shape of at least one region (B) of at least one surface (I, II, III, IV) of the object (1, 2, 3, V) is ascertained with a measurement accuracy below a predefined accuracy value by (a) providing an assumed surface shape of the surface (I, II, III, IV) as an initial shape (F1), (b) defining a plurality of measurement points (4) on the initial shape (F1), (c) ascertaining the spatial position (4') of the measurement points (4) by means of an optical measuring method, wherein the surface (I, II, III, IV) is irradiated by an electromagnetic radiation source (5) and the reflected radiation is detected by a sensor (6), (d) ascertaining the deviation of the position (4') measured in method step (c) from the position assumed in method step (b) for each measurement point (4), (e) determining an adapted surface shape (F2) from the position (4') of the measurement points (4) measured in method step (c), (f) repeating method steps (b) to (e), wherein the adapted surface shape (F2) is used as a new initial shape (F1), wherein the method is terminated after method step (e) as soon as a mean value of the deviations ascertained in method step (d) is lower than the accuracy value.

Description

Iterative method for determining the surface shape of a plate or layered object with high measurement accuracy

The invention relates to a method for determining the surface shape of a plate-like or layer-like object.

Increasingly high demands are being placed on the optical quality of vehicle windows. This applies in particular to windshields, which are increasingly being equipped with additional functions that depend on high optical quality. An example are cameras or other electromagnetic sensors that are mounted in a so-called camera or sensor area of the windshield and are directed forward in the direction of travel. Another example is head-up displays (HUD), in which a so-called HUD area of the windshield is illuminated by a projector, which means that information can be displayed to the driver without having to take his or her eyes off the road.

Especially for development projects, but also for quality control during production, it is often important to characterize the optical properties of at least one area of the vehicle window, for example the camera or sensor area or the HUD area, to ensure functionality. The optical quality is influenced in particular by the bending process of the glass panes, but also by the surface properties of the components of the vehicle pane, which can be subject to certain stochastic fluctuations. To characterize the optical properties, it is customary, for example, to measure a refractive power distribution on the finished pane using optical instruments, for example using the commercially available ISRA measuring system from Isravision.

Since the optical refractive power is essentially determined by the pane thickness, which is locally dependent on the shape of the pane surfaces, it is in principle conceivable to simulate the refractive power distribution. This requires very precise measuring methods to determine the surface shape. A common method for measuring glass panes is, for example, chromatic-confocal distance measurement with a so-called confocal sensor. The radiation from a light source is chromatically dispersed, so that the focus is strongly dependent on the wavelength. The reflected radiation is detected according to the confocal principle and analyzed with regard to wavelength. From the dominant wavelength of the detected radiation, the distance between the pane surface and the light source can be deduced.

Measurements from confocal sensors and similar devices are then possible with a particularly high level of accuracy if the light beam hits the pane surface at an angle of incidence of 90°. The arrangement of the confocal sensor must therefore already be based on information about the pane surface. In the case of curved glass panes in particular, there are typically slight deviations from the actually specified surface shape (nominal geometry) due to inaccuracies and statistical fluctuations during the bending process, so that the angle of incidence deviates from 90°, which impairs the measurement accuracy. With conventional confocal sensors, for example, a measurement accuracy of about 30 pm can be achieved, which is not sufficient for an exact simulation of the optical properties. There is a need for improved methods for determining the surface shape of vehicle windows with greater measurement accuracy.

The problem described above of determining a distribution of the optical refractive power is to be understood merely as an exemplary motivation. Exact knowledge of the surface shape of transparent or non-transparent plate-like or layer-like objects may also be required for other optical, mechanical or other questions.

The object of the present invention is to provide a method for determining the surface shape of a plate-like or layer-like object, with which better measurement accuracy can be achieved. The method should be suitable in particular for mathematically determining the optical properties, for example the local refractive power, of window panes, in particular vehicle panes, from the determined surface shape.

The object of the present invention is achieved according to the invention by a method according to claim 1. Preferred embodiments emerge from the dependent claims.

The method according to the invention serves to determine the surface shape of a plate-like or layer-like object. The surface shape can also be referred to as surface geometry. It is an iterative process based on a measurement of the spatial Position of a variety of measurement points is based. Starting from the specified nominal geometry, the measured surface shape is further approximated to the real surface shape with each iteration, with the iterations being carried out until the deviations are smaller than a previously specified accuracy value. The measuring accuracy of optical measuring methods can be significantly improved by the iterative method. In particular, it is possible to choose the measurement accuracy required for the intended purpose (for example a simulation of the optical properties) according to the requirements in the individual case. These are great advantages of the present invention.

The sheet or sheet-like article has two major surfaces and an edge surface extending therebetween. The item is characterized by a length, a width, and a thickness. The length and width dimensions are those spatial directions in which the main surfaces are spanned. The thickness corresponds to the distance between the main surfaces - the edge surface therefore extends in the thickness dimension between the main surfaces. The thickness is significantly smaller than the width and length, which gives the object its plate-like or layered character.

In the method according to the invention, the shape of at least one area of at least one surface of the plate-like or layer-like object is determined with a measurement accuracy which is less than a predetermined accuracy value by:

(a) an assumed surface shape of the surface is provided as the initial shape,

(b) a plurality of measuring points is defined on the initial form, (c) the spatial position of the measuring points is determined using an optical measuring method, the surface being irradiated by an electromagnetic radiation source and the reflected radiation being detected by a sensor, (d) the deviation of the position measured in method step (c) from the position assumed in method step (b) is determined for each measuring point, (e) an adapted position of the measuring points measured in method step (c).

surface shape is determined,

(F) process steps (b) to (e) are repeated, with the adjusted

Surface shape is used as the new initial shape. The process steps are carried out in the order given. The iterative process is terminated after process step (e) as soon as at least one mean value of the deviations determined in process step (d) is less than the specified accuracy value. The adapted surface shape determined in this way represents the result of the measurement (final shape).

Said sheet or sheet-like object is preferably a rigid sheet or sheet-like object, in particular a curved rigid sheet or sheet-like object, such as a glass pane or plastic sheet, or a flexible sheet or sheet-like object, such as a polymer film. The plate-like or layer-like object is particularly preferably a vehicle window or is provided as part of a vehicle window.

Said vehicle window can be designed as:

- Single pane of glass, in particular thermally toughened single pane of glass as so-called toughened safety glass (ESG)

- Single plastic disc

- Laminated pane comprising a first glass or plastic pane and a second

Glass or plastic pane, which are connected to each other via at least one thermoplastic polymer film.

Said components of a vehicle pane are, in particular, two glass or plastic panes and at least one thermoplastic polymer film, which are to be connected to form a composite pane, so that the glass or plastic panes are laminated to one another via the at least one polymer film.

As a starting point for the iterative method, a surface shape of said surface is first assumed, which is referred to as the initial shape within the meaning of the invention. The initial form can also be referred to as the nominal form. In the case of a curved rigid object such as a curved glass or plastic pane, the specified pane geometry is preferably used as the starting shape, which the pane should ideally have and for which the bending process and the bending tools have been designed. In the case of a flat object such as a flat pane of glass or plastic or a polymer film, for example, a perfectly flat surface can be used as the initial shape. The shape of the entire surface of the object can be determined or only a portion of the surface. If the surface shape is used to determine optical properties, often only an area of the surface is measured whose optical properties are decisive for the respective application, for example a camera or sensor area or a HUD area. In said area (or on the whole surface) a plurality of measurement points are defined on the initial shape. The measurement points are those points whose spatial position is then to be determined.

The measuring points are preferably distributed in a grid-like manner in the area of the surface, that is to say as a regular pattern distributed in said area, for example in the form of rows and columns. In principle, however, the measuring points can also be distributed irregularly. The higher the density of the measuring points, the more precisely the surface shape can be approximated, but the more complex and time-consuming the process is. In an advantageous embodiment, the distance between adjacent measuring points is at most 20 mm, preferably at most 15 mm, particularly preferably at most 10 mm, very particularly preferably at most 5 mm, in particular at most 2 mm or even at most 1 mm. Good results are achieved with this. The distance between adjacent measuring points is at least 0.01 mm or at least 0.1 mm, for example.

The spatial position of the individual measuring points is then determined using an optical measuring method. The surface of the object at the measuring point is irradiated with electromagnetic radiation, which is emitted by a radiation source directed at the measuring point. The radiation reflected from the surface is detected by a sensor and used to determine the spatial position of the respective measuring point. Depending on the measurement principle, the reflected radiation can be, in particular, reflected or scattered radiation. Said electromagnetic radiation is preferably light in the visible spectral range. In principle, however, radiation from other spectral ranges can also be used, for example UV or IR radiation.

In an advantageous embodiment, such an optical measuring method is used, the measuring accuracy of which depends on the relative positioning of the radiation source to the surface, in particular on the angle of incidence with which the surface is irradiated. This This is the case in particular with measurement methods that are based on the detection of reflected radiation. In such measurement methods, the radiation thrown back by the surface to be measured is reflected radiation. Since a deviation of the real surface shape from the nominal shape (which is used to align the radiation source) reduces the measurement accuracy in such measurement methods, the method according to the invention has a particularly advantageous effect and can improve the measurement accuracy to a particular extent.

In a preferred embodiment, said optical measurement method is carried out using a confocal sensor, with which a chromatic-confocal distance measurement is carried out. The confocal sensor is also often referred to as a confocal chromatic sensor or chromatic confocal sensor. A punctiform radiation source, typically realized by a radiation source behind a pinhole, is focused onto the surface with at least one non-color-corrected, i.e. dispersive lens. Typically, a white point light source is used, which emits visible light with a uniform spectral distribution. However, other spectral distributions can also be used as long as they are taken into account accordingly in the evaluation. The spectral range used determines the measuring range, i.e. the distance range that is accessible through the measurement - it can be selected according to the requirements in the individual case. If the radiation intensity is not evenly distributed, the detected radiation must be weighted accordingly. Due to the chromatic aberration, the focal plane is wavelength-dependent, with shorter-wave radiation components being focused at a smaller distance from the lens and longer-wave radiation components at a greater distance from the lens. The light reflected from the surface passes through the same lens (or the same lens system) according to the confocal principle, is decoupled from the illumination beam path with a beam splitter and typically imaged on a pinhole diaphragm behind which the sensor is arranged. The sensor is suitable for detecting the reflected radiation in a spectrally resolved manner. The sensor is essentially a spectrometer, with which the dominant wavelength of the reflected radiation is determined. Due to the dispersion of the radiation, this dominant wavelength depends on the distance between the radiation source and the reflecting surface, which means that a statement can be made about this distance, which in turn results in the spatial position of the respective measuring point. With a confocal sensor, relatively precise measurements are technically easily possible, since no moving components are required. The confocal sensor is preferably arranged at each measuring point with an angle of incidence of 90° to the initial shape. This means that the confocal sensor is arranged at each measuring point in such a way that the radiation source irradiates the surface assumed as the initial shape at the respective measuring point with an irradiation angle of 90°. The measurement accuracy of the confocal sensor is optimal at an angle of incidence of 90°. Since the actual surface shape typically deviates more or less from the original shape, the measurement accuracy is reduced. The measured shape is gradually approximated to the actual shape by the iterations according to the invention, so that a significantly improved measurement accuracy is obtained.

The spatial position of the measurement points can be determined, for example, in the form of spatial coordinates or as a distance from the radiation source in the radiation direction. If the position of the radiation source and the direction of radiation are known, both specifications are equivalent and can be converted into one another. The described measurement with the confocal sensor provides the stated distance from the radiation source as a measurement result.

However, other optical measuring methods can also be used to determine the spatial position of the measuring points. For example, the spatial position can be determined by optical triangulation, in particular laser triangulation, or by optical phase shifting, in particular laser phase shifting. With these methods, too, the measurement accuracy can be improved by the iterative method according to the invention.

The laser triangulation is based on a distance measurement by angle calculation. Laser radiation is directed at a measuring point on the surface of the object to be measured and reflected or scattered there. Depending on the distance, the reflected radiation hits a spatially resolving sensor at a certain angle. The distance to the measuring point is calculated from the position of the point of light on the sensor and from the distance from the radiation source to the sensor.

The deviation of the measured spatial position from the position assumed on the basis of the initial shape is then determined for each measuring point. This determination of the deviation can already take place for measured measuring points before all measuring points have been measured, or collectively for all measuring points after the measurement all measuring points. This deviation is a measure of the extent to which the assumed initial shape matches the measured surface shape - it is also a measure of the measurement accuracy that has already been achieved.

Said deviation is the absolute value of the vector between the assumed position of the measuring point and the measured position. In the preferred chromatic-confocal distance measurement with a confocal sensor, it results as the absolute difference between the measured and the assumed distance of the measuring point from the radiation source in the radiation direction.

An adapted surface shape is then determined from the measured position of all measuring points, for example by means of a suitable simulation using interpolation. The higher the density of the measuring points, the more precisely the adapted surface shape can be determined.

If the desired measurement accuracy has not yet been achieved, the next iteration of the measurement method is carried out. The adjusted surface shape determined in the previous iteration is used as the new starting shape. In turn, measurement points are defined, the radiation source is arranged relative to these measurement points on the adapted initial shape, its spatial position is determined and its deviation from the assumed position is determined. A comparison of these deviations with the previously defined accuracy value provides the decision as to whether a further iteration is necessary.

Once the desired measurement accuracy has been reached, the iterative process is terminated. The fitted surface shape determined in the last iteration is the result of the measurement and is treated as the measured surface shape (final shape).

A comparison of the deviation that occurs and the previously specified accuracy determine whether the desired measuring accuracy has been achieved. In a preferred embodiment, the deviation is determined for each measuring point and then a mean value of all deviations is determined. The measuring accuracy is considered to be achieved when the mean value is smaller than the accuracy value. Which type of averaging is used (e.g. arithmetic mean, geometric mean or root mean square) is left to the expert and should be taken into account when determining the accuracy value. The arithmetic mean as the sum of all absolute deviations divided by the number of measuring points and the square mean as the square root of the quotient of the sum of all squared deviations divided by the number of measuring points are particularly suitable. Alternatively, instead of averaging, the deviation of each measuring point can be compared individually with the accuracy value. The measuring accuracy is considered to have been achieved when the deviation for each measuring point is smaller than the accuracy value.

In an advantageous embodiment, the specified accuracy value is at most 10 μm, preferably at most 5 μm, particularly preferably at most 2 μm, for example from 0.5 μm to 10 μm, from 0.5 μm to 5 μm or from 0.5 μm to 2 μm . With such an accuracy, the optical properties of the plate-like or layer-like object in particular can be determined with high precision.

In an advantageous embodiment, the object whose surface shape is to be determined is a transparent object. For the purposes of the invention, a transparent object is understood to mean an object which has a transmission of at least 10%, preferably at least 20%, particularly preferably at least 50%, very particularly preferably at least 70%, in the visible spectral range from 380 nm to 780 nm. The stated values particularly preferably apply to the entire visible spectral range, so that the transmission is not below the stated values at any point in the spectral range. The transparent object is preferably a glass pane, a plastic pane, a polymer film or a composite thereof, for example a composite pane made from a first glass or plastic pane and a second glass or plastic pane which are connected to one another via at least one polymer film.

If visible light is used in the optical measuring method, this is largely transmitted through the transparent object. This has the advantage that both main surfaces of the object become accessible for the measurement without the object having to be rotated or the radiation source and sensor having to be moved to the other side of the object. In an advantageous embodiment, the surface shape of the surface facing the radiation source (main surface) and the surface facing away from the radiation source (main surface) is therefore determined. In this sense, in the case of a laminated pane, the two external surfaces are considered to be the main surfaces. If the spatial position of the measuring points is determined using the preferred method of chromatic-confocal distance measurement, it is possible to determine the measuring points of both surfaces with a single measurement (simultaneously) if the dispersed radiation of the confocal sensor has a larger extent than the thickness of the plate-like or sheet-like object. Two dominant wavelengths can then be identified in the reflection spectrum, the distance to the surface facing the radiation source being able to be determined from the one with the shorter wavelength and the distance to the surface facing away from the radiation source being determined from the one with the longer wavelength. If the thickness of the object is too great for both surfaces to be measured simultaneously, the two surfaces can be measured independently of one another by adjusting the distance between the radiation source and the object, or the radiation first on one surface and then on the other is focused.

It is also possible to measure two or more transparent plate-like or layer-like objects which are arranged one on top of the other. The two or more objects are in particular independently selected from glass panes, plastic panes and polymer films. Again, it is possible to measure all surfaces of the objects simultaneously with a confocal sensor if its measuring range is large enough. If the measuring range is only sufficient for measuring a single surface or a subgroup of all surfaces, the measurement is carried out in several steps, whereby the confocal sensor is moved or focused differently.

In principle, however, it is also possible to measure the surface of an opaque plate-like or layer-like object. Then, of course, only the surface facing the radiation source and the sensor is accessible. In order to measure both surfaces, the object must be rotated relative to the radiation source in the meantime.

The method according to the invention can be carried out, for example, on window panes in architecture or their individual components, on window panes in vehicles or their individual components, on glass panes as part of furnishings, furniture or electronic devices or on optical lenses. The glass panes can optionally be provided with coatings, in particular transparent coatings, such as are customary, for example, as IR-reflecting sun protection coatings or low E coatings. In a preferred embodiment, the method according to the invention is carried out on window panes, in particular curved vehicle panes or their individual components. These vehicle panes or individual components can be designed in particular as: a curved single pane of glass, preferably thermally toughened single pane of glass (ESG, single-pane safety glass); a curved laminated pane, comprising a first and a second pane of glass or plastic, in particular pane of glass, which are connected to one another via at least one thermoplastic polymer film; two curved panes of glass or plastic, in particular panes of glass, which are intended to be connected via at least one thermoplastic polymer film to form a composite pane; for this purpose, the two panes of glass or plastic essentially have the same curvature; the two panes of glass or plastic can be measured individually or simultaneously one on top of the other; two curved glass or plastic panes, in particular glass panes, and at least one thermoplastic polymer film, the glass or plastic panes being intended to be connected via the at least one thermoplastic polymer film to form a composite pane; for this purpose, the two panes of glass or plastic essentially have the same curvature; the two panes of glass or plastic and the at least one polymer film can be measured individually; it is also possible to measure two, several or all components simultaneously one on top of the other.

The single glass pane mentioned above can in particular be a side window, a rear window or a roof window of a vehicle, in particular a motor vehicle, for example a passenger car. The composite panes mentioned above can in particular be a windshield, a roof pane, a rear window or a side window of a vehicle, in particular a motor vehicle, for example a passenger car.

In advantageous developments of the invention, the method according to the invention is used on window panes, in particular curved vehicle panes (in particular single glass panes or composite panes) or their individual components (in particular two panes of glass or plastic and at least one polymer film which are intended to be laminated to form a composite pane) and the surface shape determined according to the invention is used to determine optical or mechanical properties on the basis thereof. Simulation methods known per se are used for this determination, for example so-called ray tracing methods for determining optical properties. Exemplary applications are:

Determination of a distribution of the local refractive power of the entire window pane or a central viewing area of the window pane, from which in turn the quality of the transmission optics (in particular any optical distortions or the occurrence of double images) or the reflection optics (in particular the occurrence of reflections) are determined;

Determination of a distribution of the local refractive power in a camera or sensor area of the window pane, from which in turn the quality of the transmission optics (in particular any optical distortions or the occurrence of double images) is determined, which influences the information recorded by the camera or the sensor; A camera or sensor area is understood to be an area of the window pane that lies in the detection beam path of a camera or sensor mounted on or in the window pane, which is therefore traversed by electromagnetic radiation, which is then detected by the camera or sensor;

Simulation of the representation of a head-up display (HUD), in particular with regard to distortions, image rotations or blurring;

Calculating a wedge angle required to overlap the main and ghost images of a head-up display; for HUDs, a HUD area of the disk is illuminated by a projector to generate a virtual display image; both the inside and outside surfaces of the pane constitute a reflection plane, so that a ghost image (reflection on the outside surface) is also generated in addition to the main image (reflection on the inside surface); the two images are made to overlap by placing the two surfaces at a wedge angle to each other; this is typically achieved in laminated panes by using a wedge shaped thermoplastic film to laminate the two panes of glass together;

Measurement of the local wedge angles of a wedge-shaped glass pane or polymer film; Measurement of the distribution of local thicknesses and the local distance between two glass panes lying on top of each other in order to determine an influence on stresses in the glass due to mechanical deformation when these two glass panes are connected by lamination to form a composite pane; optionally, the surface shape of the thermoplastic polymer film used for lamination can also be determined in order to achieve an even more precise result;

determination of the surface waviness of the window pane (also referred to as rate of change (ROC) by those skilled in the art);

Quantitative evaluation of the reflection optics of the window pane, for example within a see-through area or a camera or sensor area.

The glass panes can also be provided with additional elements whose surface shape and local thickness distribution can be determined using the method according to the invention. Examples of this are transparent or opaque coatings, printed elements (especially in the screen printing process), primer layers, adhesive layers, solder contacts, camera mounting plates or other add-on parts (for example made of plastic or metal).

For the purposes of the present invention, refractive power refers to the optical refractive power, which can also be referred to as the refractive index and represents the reciprocal of an optical focal length. The refractive power is typically given in units of diopters (dpt) (1 dpt = 1 rrr ¹ ).

The aforementioned camera or sensor area can be provided for sensors and/or cameras as part of a driver assistance system (Advanced Driver Assistance System, ADAS). In this case, optical cameras, IR cameras, radar sensors and/or lidar sensors are used in particular. The HUDs mentioned above can be classic or contact-analogous HUDs (augmented reality HUD, AR-HUD). With an AR-HUD, elements of the environment are included in the display, for example pedestrians or traffic signs are marked or navigation arrows are projected onto the road. The AR-HUD differs from the classic HUD in particular by a larger HUD area and a larger projection distance (distance of the virtual image from the projector).

In a particularly preferred embodiment, the object is a single pane of glass or plastic, preferably a curved pane of glass or plastic preferably a curved glass pane, in particular thermally toughened glass pane. The object is intended in particular as a vehicle window, for example as a side window, rear window or roof window. With the method according to the invention, the surface shape of the surface facing the radiation source and the surface facing away from the radiation source is determined (preferably simultaneously). Either the shape of the entire surfaces or a portion of them is determined. A refractive power distribution (distribution of local refractive powers) is very particularly preferably simulated from the surface shape of the two surfaces determined in this way, from which, for example, the quality of the transmission optics (in particular any optical distortions or the occurrence of double images) of the entire pane or a region thereof is determined. The area can be, for example, a central viewing area or a camera or sensor area. Alternatively, the surface waviness determined in this way is determined from the surface shape of the two surfaces, the reflection optics (in particular the occurrence of reflections) or the surface shape and local thickness distribution of additional elements applied to the pane surface, such as screen prints, coatings, solder contacts, adhesive or primer layers or add-on parts.

In a further particularly preferred embodiment, the object is a composite pane, preferably a curved composite pane, comprising a first glass or plastic pane (particularly glass pane) and a second glass or plastic pane (particularly glass pane), which are connected to one another via at least one polymer film. The object is intended in particular as a vehicle window, for example as a windshield, side window, rear window or roof window, very particularly preferably as a windshield. With the method according to the invention, the surface shape of the two external surfaces of the two glass or plastic panes facing away from the polymer film is determined (preferably simultaneously). During the measurement, one of these surfaces preferably faces the radiation source and the other faces away from the radiation source. The shape of the surface of the first glass or plastic pane facing away from the radiation source and away from the polymer film and of the surface of the second glass or plastic pane facing away from the radiation source and away from the polymer film is thus determined. Either the shape of the entire surfaces or a portion of them is determined. Very particularly preferably, a refractive power distribution (distribution of local refractive powers) is simulated from the surface shape of the surfaces determined in this way, from which, for example, the quality of the transmission optics (in particular any optical distortions or the occurrence of double images) of the entire pane or a portion thereof is detected. The area can be, for example, a central viewing area (in the case of a windshield, in particular field of vision A or field of vision B according to ECE- ^R43 (Regulation No. 43 of the Economic Commission of the United Nations for Europe (UN/ECE)), a HUD area or a camera or sensor area Alternatively, the representation of a head-up display (HUD) is determined from the surface shape of the surfaces determined in this way, in particular with regard to distortions, image rotations, blurring, or the occurrence of ghost images as a result of multiple reflection of the radiation of the HUD projector Alternatively, the local wedge angle of a wedge-shaped composite pane, the reflection optics (in particular the occurrence of reflections), the surface waviness or the surface shape and local thickness distribution of additional elements attached to the pane surface are determined from the surface shape determined in this way , such as screen prints, coatings, Solder contacts, adhesive or primer layers or attachments.

In a further particularly preferred embodiment, the surface shape of the surface facing the radiation source and the surface facing away from the radiation source of a first glass or plastic pane (in particular glass pane) and a second glass or plastic pane (in particular glass pane) is determined, as well as the surface shape of the surface facing the radiation source Surface and facing away from the radiation source surface of at least one polymer film. The two glass or plastic panes are intended to be connected via the at least one polymer film to form a composite pane and are preferably curved, in particular have the same curvature. The resulting laminated pane is intended in particular as a vehicle pane, for example as a windshield, side window, rear window or roof pane, very particularly preferably as a windshield. Either the shape of the entire surfaces or a portion of them is determined. A refractive power distribution (distribution of local refractive powers) is very particularly preferably simulated from the surface shape of the surfaces determined in this way, from which, for example, the quality of the transmission optics (in particular any optical distortions or the occurrence of double images) of the entire resulting composite pane or a region thereof is determined. The area can be, for example, a central see-through area (in the case of a windshield, in particular field of view A or field of view B according to ECE-R43), a HUD area or a camera or sensor area. Alternatively, from the surface shape determined in this way Surfaces determine the representation of a head-up display (HUD), in particular with regard to distortions, image rotations, blurring or the appearance of ghost images as a result of multiple reflections of the radiation from the HUD projector. Alternatively, an influence on stresses in the glass due to mechanical deformation during lamination can be determined from the surface shape determined in this way. Alternatively, the local wedge angle of a wedge-shaped pane of glass or polymer film, the reflection optics (in particular the occurrence of reflections), the surface waviness or the surface shape and local thickness distribution of additional elements such as screen prints, coatings, solder contacts, adhesive or primer layers are determined from the surface shape determined in this way or attachments.

In a further particularly preferred embodiment, the method is carried out on two glass or plastic panes (in particular glass panes) lying on top of one another, in particular on two curved glass or plastic panes (in particular glass panes) lying on top of one another. The surface shape of the surface facing the radiation source and the surface of the two glass or plastic panes facing away from the radiation source is determined. From this, a distribution of the local thicknesses of the two panes of glass or plastic and a distribution of the local distance between the surfaces of the two panes of glass or plastic facing one another are determined. The two panes of glass or plastic are intended to be connected via at least one thermoplastic polymer film to form a composite pane, and an influence on stresses in the glass due to mechanical deformation during lamination is determined from the thickness and distance distribution. The resulting composite pane is intended in particular as a vehicle pane, for example as a windshield, side pane, rear pane or roof pane.

In a further particularly preferred embodiment, the method is carried out on two panes of glass or plastic (in particular panes of glass) which are intended to be connected via at least one thermoplastic polymer film to form a composite pane. The two panes of glass or plastic are preferably curved, in particular have the same curvature. The laminated pane is preferably a vehicle windscreen. The two areas are arranged congruently with one another in the composite pane and form a HUD area as a reflection surface for a HUD projector. From the surface shape thus determined, a wedge angle is calculated (or a distribution of local wedge angles) required to capture the main image (reflection from one of the two said surfaces) and the ghost image (reflection on the other of said two surfaces) of the HUD to overlap. The two panes of glass or plastic can be measured individually or simultaneously one on top of the other. In the context of the present invention, glass panes are preferably made of soda-lime glass, as is customary for window panes. The thickness of the glass pane can be freely selected according to the requirements in the individual case. Typical thicknesses for glass panes as vehicle panes or components thereof are in the range from 0.5 mm to 20 mm, in particular 1 mm to 5 mm.

The invention is explained in more detail with reference to a drawing and exemplary embodiments. the

Drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way. Show it:

1 shows a schematic view of a confocal sensor during an embodiment of the method according to the invention,

2 shows a plan view of a laminated pane as the subject of the method according to the invention,

3 shows a schematic view of the assumed initial shape and the real surface shape of a plate-like object during an embodiment of the method according to the invention,

4 shows a schematic representation of an iteration of an embodiment of the method according to the invention,

5 shows a cross section of a laminated pane as the subject of the method according to the invention and

6 shows a cross section through two glass panes lying one on top of the other as the subject of the method according to the invention.

FIG. 1 illustrates an optical measuring method for determining the spatial position of a measuring point on the surface of a plate-like or layer-like object, which can be used in the iterative method according to the invention. The measuring method is carried out as a chromatic-confocal distance measurement with a K confocal sensor. The confocal sensor K contains a radiation source 5 which emits visible, white light. The radiation source 5 is arranged behind a pinhole 7, as a result of which it acts as a point light source. The radiation S from the radiation source 5 is focused via a system of lenses 9, 10 onto a plate-like or layer-like object, for example a pane of glass 1. The lenses 9, 10 shown are only to be understood as examples—in reality, a significantly larger number of lenses can be used in order to suitably shape the radiation S. The focusing lens 10 (or the focusing lens system) is not chromatically corrected, so that the focal point is strongly dependent on the wavelength (chromatic aberration). As a result, the radiation S is split up along the optical axis depending on the wavelength, with the focal point being closer to the confocal sensor K the higher the energy of the steel S is. This principle is illustrated in the figure using three exemplary wavelengths l=420 nm (blue), l=530 nm (green) and l=650 nm (red) - in reality, of course, there is a continuum of focal points. The radiation S ideally strikes the surface I of the glass pane 1 at an angle of incidence of 90°, is reflected by it again in the direction of the confocal sensor K and is collected by the lens 10 . The reflected radiation S is at least partially decoupled from the excitation beam path by a beam splitter 12 and focused by at least one additional lens 11 onto an additional pinhole diaphragm 8 behind which a sensor 6 is located. According to the confocal principle, the pinhole diaphragm 8 ensures that those radiation components that do not come from the object plane are largely masked out. The pinholes 7 and 8 are preferably identical in construction. The sensor 6 is a radiation detector in the manner of a spectrometer and is suitable for determining the spectral distribution of the reflected light. In this way, that wavelength can be determined which dominates the reflection spectrum - that is, in the focus of which the reflecting surface I was arranged. From the knowledge of the focal widths of the individual wavelengths, the distance between the surface I and the confocal sensor K can be determined directly from the dominant wavelength.

The figure also makes it clear that both surfaces I, II of the transparent glass pane 1 can be measured simultaneously if the thickness of the glass pane 1 is less than the measuring range of the confocal sensor K. The measuring range is limited by the dispersion of the radiation S due to chromatic aberration is determined and corresponds to the expansion of the dispersed radiation along the optical axis. If both surfaces I, II are within the measuring range, two reflection signals can be determined and the distance between the two and the confocal sensor K can be determined.

In preferred applications of the invention, the measured plate-like or sheet-like object is curved. In the figure, on the other hand, the glass pane 1 is shown planar for the sake of simplicity.

FIG. 2 shows a plan view of a composite pane V as an example of a plate-like or layer-like object (FIG. 2(a)) whose surface shape is to be determined using the method according to the invention. The laminated pane V is the windshield of a motor vehicle and consists of two panes of glass which are connected to one another via a thermoplastic polymer film. An area B of the laminated pane V is provided as a camera and sensor area. Optical cameras and other sensors are to be mounted on the surface of the laminated pane V on the interior side (For example, radar and lidar sensors) for a driver assistance system (Advanced Driver Assistance System, ADAS) are attached, which electromagnetic radiation passing through the area B can detect. In order to characterize the functionality, display quality or similar properties of the ADAS, the optical properties of the area B are to be determined by calculation, for example using ray tracing methods. This requires precise knowledge of the surface shape of the laminated pane V in area B, in particular the surface shape of the two external surfaces of the glass panes facing away from the polymer film, i.e. the outside surface of the outer pane and the interior surface of the inner pane. This results in particular in a local distribution of the slice thicknesses. The area B is shown enlarged in Figure 2(b). A large number of measuring points 4 are defined within the area B, which are distributed in a grid-like manner in the form of rows and columns, the distance between adjacent measuring points 4 (within a row or column) being 1 mm, for example. In order to determine the surface shape with a high degree of accuracy, the spatial positions of the surfaces at these measuring points are to be measured using the iterative method according to the invention.

Figure 3 schematically illustrates the measurement of a measuring point 4 using the confocal sensor K from Figure 1. In order to provide the best possible measuring accuracy, the confocal sensor K must be arranged at each measuring point 4 in relation to the surface to be measured in such a way that the radiation S has an angle of incidence a of 90 ° strikes said surface. Since the operator initially has no other data available, this alignment of the confocal sensor K is carried out using the theoretical nominal geometry - i.e. in the case of a bent glass pane using the specified surface shape for which the glass bending process and the glass bending tools were designed. The method is based on this nominal geometry as the initial form F1. However, due to surface inaccuracies and bending errors that occur in the real, non-ideal glass bending process, the real shape R of the surface deviates from this initial shape F1. The consequence of this is that the real angle of incidence a' is not 90°, but deviates from it to a greater or lesser extent. This reduces the measurement accuracy of the measurement with the confocal sensor K.

FIG. 4 schematically illustrates an iteration of the measurement method according to the invention. A large number of measurement points 4 are defined on the initial form F1. The confocal sensor K is arranged at each measuring point 4 with an angle of incidence a of 90° the spatial position 4' of the respective measurement point 4 is measured, in particular as the distance of the measurement point 4 from the confocal sensor K in the beam direction (FIG. 4(a)). An adapted form F2 of the surface is determined from the positions 4' thus determined, for example by interpolation (FIG. 4(b)). Because of the limited measurement accuracy of the confocal sensor K, this adapted form F2 still deviates from the real form R of the surface. A more accurate result is achieved with a further iteration of the method, with the adapted form F2 determined in the first iteration being used as the new initial form F1. The confocal sensor K is now arranged at each measuring point with an angle of incidence of 90° to this new initial form F1. The deviation of the real angle of incidence a' from 90° is now less pronounced than in the first iteration, and the measurement result is therefore more accurate. In this way, the operator can gradually approach the real shape R through the iterations. The iteration process is aborted when the deviation of the measured positions 4' from the respective measuring point 4 determined in one iteration is less pronounced than a previously specified accuracy value. When comparing the deviations with the accuracy value, the mean value of the deviations can be used and the method can then be aborted if the mean value is less than the accuracy value. Alternatively, each deviation value can be compared individually with the accuracy value and the method can only be terminated when the deviation at each individual measuring point is less than the accuracy value. The adjusted shape F2 determined in the last iteration forms the final result of the method (final shape). This final shape can now be used, for example, to carry out optical simulations in order to predict the optical properties.

FIG. 5 shows the cross section of the composite pane V from FIG. 2. For the sake of simplicity, the composite pane V is again shown planar, although in reality the windshield is curved. The composite pane V is formed from a first glass pane 1 and a second glass pane 2 which are connected to one another via a thermoplastic polymer film 3 . The first glass pane 1 is, for example, the outer pane, which in the installed position faces the outside environment, and the second glass pane 2 is the inner pane, which in the installed position faces the vehicle interior. The first glass pane 1 has an outside surface I and an inside surface II. The second glass pane 2 has an outside surface III and an inside surface IV. The interior surface II of the first glass pane 1 and the outside surface III of the second glass pane 2 face the polymer film 3 and the respective other glass pane. The outside surface 1 of the first glass pane 1 and the interior-side surface IV of the second glass pane

2 face away from the polymer film 3 and the other glass pane - they form the external surfaces of the composite pane V. In particular, the surface shapes of these external surfaces I, IV must be determined with great accuracy in order to simulate the optical properties of a region B.

If the measuring range of the confocal sensor K is sufficiently large, the surface shape of both external surfaces I, IV can be determined simultaneously, as is illustrated in FIG. 1 for a single pane of glass. Otherwise, two separate measurements are performed.

If area B is a camera or sensor area, this can be used to determine the transmission and reflection behavior, for example, in order to determine the effectiveness of the cameras and sensors. If the area B is a HUD area, distortions or rotations of the HUD display can be determined or a

Wedge angle required to match the HUD reflections on the external surfaces I, IV as closely as possible, thereby avoiding ghosting.

FIG. 6 shows the cross section of two glass panes 1, 2 lying one on top of the other as a further exemplary application of the method according to the invention. In reality, these glass panes 1, 2 are also bent and intended for this purpose via a polymer film

3 to be laminated into a composite pane V. Those surfaces II, III of the glass panes 1, 2 which should face one another in the laminated pane V also face one another in the stack of glass panes 1, 2. The surface shape of all surfaces I, II, III, IV can be determined with the method according to the invention. A distribution of the local thicknesses of the glass panes 1, 2 and the local distance between the surfaces II, III facing each other can be determined from this, which in turn has an influence on the stress distribution in the glass panes 1, 2, for example, due to mechanical deformations that occur during the lamination of the Composite pane V occur. If the surfaces of the polymer film 3 are also determined, the optical properties of the resulting laminated pane V can also be determined. Reference list:

(1, 2) plate or layer-like object: glass pane (3) plate or layer-like object: polymer film (V) plate or layer-like object: composite pane

(4) measuring point

(4') measured spatial position of measuring point 4

(5) Radiation source of the optical measurement method (6) Sensor of the optical measurement method

(S) electromagnetic radiation from radiation source 5

(B) Region of the surface of the sheet or sheet-like article (F1) Initial shape of the surface of the sheet or sheet-like article

(F2) adapted shape of the surface of the plate-like or sheet-like object (R) real shape of the surface of the plate-like or sheet-like object

(K) Confocal sensor (a) Angle of incidence of the confocal sensor K on the initial form F1

(a') Angle of incidence of the confocal sensor K on the real form R

(7, 8) Pinholes of the K confocal sensor (9, 10, 11) Lenses of the K confocal sensor (12) Beam splitter of the K confocal sensor

(I, II) surfaces of item 1 (III, IV) surfaces of item 2

Claims

patent claims

1. Method for determining the surface shape of a plate-like or layer-like object (1, 2, 3, V), wherein the shape of at least one region (B) of at least one surface (I, II, III, IV) of the object (1, 2 , 3, V) is determined with a measurement accuracy which is smaller than a predetermined accuracy value by

(a) an assumed surface shape of the surface (I, II, III, IV) is provided as the initial shape (F1),

(b) a plurality of measuring points (4) is defined on the initial form (F1),

(c) the spatial position (4') of the measuring points (4) is determined using an optical measuring method, the surface (I, II, III, IV) being irradiated by an electromagnetic radiation source (5) and the reflected radiation by a sensor (6) is detected,

(d) the deviation of the position (4') measured in method step (c) from the position assumed in method step (b) is determined for each measuring point (4),

(e) an adapted surface shape (F2) is determined from the position (4') of the measuring points (4) measured in method step (c),

(f) process steps (b) to (e) are repeated, with the adapted surface shape (F2) being used as the new initial shape (F1), with the process being terminated after process step (e) as soon as an average value of the values specified in process step (d ) certain deviations, the accuracy value is lower.

2. The method according to claim 1, wherein the optical measuring method is carried out by means of chromatic-confocal distance measurement with a confocal sensor (K), which is arranged at each measuring point (4) with an angle of incidence (a) of 90° to the initial shape (F1).

3. The method according to claim 1 or 2, wherein the measuring points (4) are distributed in a grid-like manner in the area (B) of the surface (I, II, III, IV) and wherein the distance between adjacent measuring points (4) is at most 20 mm, preferably at most 10 mm, particularly preferably at most 5 mm, very particularly preferably at most 2 mm.

4. The method according to any one of claims 1 to 3, wherein the method is aborted after method step (e) as soon as each deviation determined in method step (d) is less than the accuracy value.

5. The method according to any one of claims 1 to 4, wherein the accuracy value is at most 10 μm, preferably at most 5 μm, particularly preferably at most 2 μm.

6. The method according to any one of claims 1 to 5, wherein the object is a transparent object, preferably a glass pane (1), a plastic pane, a polymer film or a composite thereof, and wherein the shape of a surface (I ) and a surface (II, IV) facing away from the radiation source (5).

7. The method according to any one of claims 1 to 6, wherein the object is a single pane of glass (1) or plastic pane, in particular a curved pane of glass (1) or plastic pane, and wherein the shape of a surface (I) facing the radiation source (5) and a surface (II) facing away from the radiation source (5).

8. The method according to claim 7, wherein a refractive power distribution is simulated from the shape of the surfaces (I, II) or the reflection optics.

9. The method according to any one of claims 1 to 6, wherein the object is a composite pane (V), in particular a curved composite pane (V), comprising a first glass pane (1) or plastic pane and a second glass pane (2) or plastic pane, which at least one polymer film (3) are connected to one another, and wherein the shape of a surface (I) of the first glass pane (1) or plastic pane that faces the radiation source (5) and faces away from the polymer film (3) and one that faces away from the radiation source (5). and is determined by the polymer film (3) facing away from the surface (IV) of the second glass pane (1) or plastic pane.

10. The method according to any one of claims 1 to 6, wherein the shape of the radiation source (5) facing surface (I) and of the radiation source (5) facing away from the surface (II) of a first glass pane (1) or plastic pane, the shape of a the Surface (III) facing the radiation source (5) and a surface (IV) facing away from the radiation source (5) of a second glass pane (2) or plastic pane and the shape of a surface facing the radiation source (5) and a surface facing away from the radiation source (5). surface of at least one polymer film (3), the first glass pane (1) or plastic pane and the second glass pane (2) or plastic pane being intended to be connected via the at least one polymer film (3) to form a composite pane (V), and are preferably curved.

11. The method according to claim 9 or 10, wherein the laminated pane (V) is a vehicle pane and wherein said area (B) is a central viewing area, a sensor area, a camera area or a HUD area.

12. The method according to any one of claims 9 to 11, wherein from the shape of the surfaces (I, II, III, IV) a refractive power distribution within the at least one region (B) of the composite pane (V) is simulated, the representation of a head-up -Displays (HUD) or the reflection optics.

13. The method according to any one of claims 1 to 6, which is carried out on two superimposed glass panes (1, 2) or plastic panes, in particular on two superimposed curved glass panes (1, 2) or plastic panes, the shape of one of the radiation source (5) facing Surface (I, III) and a surface (II, IV) facing away from the radiation source (5) of the two glass panes (1, 2) or plastic panes is determined and from the shapes of the surfaces (I, III; II, IV) a Distribution of the local thicknesses of the two glass panes (1, 2) or plastic panes and a distribution of the local distance between the facing surfaces (II, III) of the two glass panes (1, 2) or plastic panes is determined.

14. The method according to claim 13, wherein the two glass panes (1, 2) or plastic panes are intended to be connected via at least one polymer film (3) to form a composite pane (V) and wherein the distribution of the local thicknesses and the distribution of the Local distance caused by mechanical deformation stresses of the laminated pane (V) can be determined.