DE102007014475A1 - Method for determining surface properties, involves evaluating locally resolved sketch of surface to be examined with multiple measured values, where sketch represents certain physical properties that are characterized by measured values - Google Patents

Abstract

The method involves evaluating a locally resolved sketch of a surface (8) to be examined with multiple measured values. The measured values are analyzed for the determination of the surface parts of the sketch. The sketch represents certain physical properties that are characterized by the measured values. The result value of the physical properties and further value characteristic of the surface are determined. The further characteristic value is represented together with the result value or a value dependent on the result value. An independent claim is also included for a device for the quantitative determination of surface properties.

Description

The The present invention relates to a method and an apparatus for quantitative determination of surface properties.

The Texture of surfaces is an essential feature of everyday objects, such as of motor vehicles and other commodities, and determines significantly the overall impression on the human Viewer. An example of this are high gloss or metallic paints of vehicle bodies.

Under Surface properties are within the scope of the invention in particular those physical properties of a surface understood the appearance of a surface for determine the human viewer. This includes in particular Properties such as macro and microstructure, topography, color, color location, Brightness of the color, gloss, sharpness of image, glossy haze, Surface texture, roughness and surface waviness (English: "orange peel") or coarseness (coarseness).

to reproducible assessment of the quality of surfaces, in particular, these high gloss finishes, are measuring devices required just those physical quantities capture the overall impression on the human viewer determine in a decisive way.

In Recently, so-called effect pigment coatings are gaining increasingly popular. These coatings have effect pigments which reflect the light irradiated to them differently. Devices and methods are known from the prior art, to assess also such effect pigment coatings quantitatively. The Invention is particularly for such effect pigment coatings applicable.

at a known method, for example, a certain threshold set for an intensity of the reflected light and only those areas of an observed surface taken into account whose intensity is above this Threshold. The measurement result is about the respective Intensities of the individual considered area segments integrated. This evaluation provides a clue about the optical properties of the examined surface. there However, it has been found that surfaces, which same or similar result values of this evaluation when viewed directly by the human eye can act very differently.

Of the The present invention is therefore based on the object, a more accurate To allow classification of surfaces to be examined. This is inventively by a method according to claim 13 and an apparatus according to claim 13 achieved. advantageous Embodiments and developments are the subject of Dependent claims.

at the inventive method for quantitative Determination of surface properties becomes a spatially resolved Evaluated image of a surface to be examined, wherein this spatially resolved image has a plurality of measured values. In doing so, this image is analyzed to those area proportions to determine the surface to be examined, the one certain, in particular characterizable by the measured values, have or represent physical property. Farther a result value of this physical property is determined this result value being characteristic for the measured values the physical property (exactly) of all those areas that was determined by the analysis of the image.

According to the invention next to the result value another for the surface characteristic value and this characteristic value is shared with the result value or one of this result value derived value.

By the determination of this second characteristic value, which is preferred independent of the first result value, it is possible also the optical differences of such surfaces capture the same by prior art methods or leave a similar visual impression.

As mentions, is a corresponding spatially resolved Image evaluated. It is possible that this spatially resolved Picture is taken, for example, immediately before the evaluation and the evaluation follows accordingly. It but would also be possible, first one To capture a variety of spatially resolved images and then this evaluate.

In This relationship is based on that of the applicant at the same time filed in the present application further patent application entitled "Method and apparatus for quantitative determination of surface properties. "The disclosure this application is hereby incorporated by reference in its entirety to the disclosure content of the present application.

In another preferred method the further characteristic value represents the contrast of the evaluated image. For example, it is possible that images that provide similar integrals with regard to their intensities and the respective surface segments, on the other hand, differ considerably in terms of contrasts. A possible parameter for the contrast of the image may be, for example, a variance or a scattering over a multiplicity of ascertained intensity values of the evaluated image.

at represents another method according to the invention the more characteristic value the color properties of the evaluated Image. In turn, certain area proportions can and, for example, the individual effect pigments be differentiated according to their color.

The Presentation of the result value and the characteristic value can be done for example in a biaxial coordinate system. However, it would also be possible to have a one-dimensional Coordinate system to use and the different characteristic tables Represent values in a different way, for example by different colors different measuring points.

Preferably The image to be evaluated is generated by the fact that radiation on the surface to be examined is irradiated and at least one Proportion of radiation reflected back from the surface is received by a radiation detector device and this Radiation detector device, the measured values or for the fair values outputs characteristic data. In the radiation detector device it may be, for example, a CCD chip, the radiation receives and outputs corresponding measured values.

at Another preferred method is compared with the result value the size of the determined area shares displayed or output.

at Thus, this process is no longer an integral value that the Taking into account intensities and the area segments, but the intensities are added spent against the surface segments. at This variant is thus in the representation of a third size taken into account by the fact that the previously used integral value is split into its two components.

there this result has to be compared to the size of certain area proportions not necessarily directly to be issued to the user, it is also possible that a processor processes a multiplicity of such results, in an internal comparison to then, for example output a result of this comparison to the user. there may, for example, be input to the user as a result of this comparison Warning signal are output, which shows that a currently measured Area of the surface to be examined no longer acceptable is or from other surface portions also optically through an observer can be distinguished.

With in other words, a large number of measured values is spatially resolved recorded which characteristic properties of the surface represent. The picture consists in particular of a multiplicity of pixels, each of these pixels being at least one particular one Measured value can be assigned.

Preferably is the result value by forming an average of the values the physical properties of all those areas determined, which were determined by the analysis of the image. It can however, integrals, distribution functions, sums and the like Operations are formed.

In order to are inventively first those Area proportions determines the particular physical Feature, for example, those area shares, their scattering intensity above a certain threshold lies. Subsequently, an average over the certain intensity values are formed, in which case only those areas are considered, whose Intensities are above the threshold mentioned. This will be preferably a relative intensity value is output, i. H. from the determined intensity value is still the threshold deducted.

Subsequently the named result value, i. H. the average intensity value versus the size of the given area shares shown. The size of the specific area shares results in particular from a determination of the number of those Pixels that represent such areas, whose intensity is above the threshold. More precisely, an illuminated area on, for example imaged a camera and this in turn gives a corresponding spatially resolved image.

While in the prior art only an integrative method is used, in which a product is output from the result value and the associated surface portion, as it were, it is proposed to output both the size of the area proportions and the result values separately. This idea is based on the experience that, for example, a high number of pixels or a high area proportion with a low In In contrast, the intensity of the reflection is different from a low surface area with a high intensity value and, nevertheless, the respective product can be of the same size and therefore no measurable difference between these two surface types is output with the methods known from the prior art.

Preferably The image to be evaluated is generated by the fact that radiation on the surface to be examined is irradiated and at least one Proportion of radiation reflected back from the surface is received by a radiation detector device and this Radiation detector device, the measured values or for the fair values outputs characteristic data. In the radiation detector device it may be, for example, a CCD chip, the radiation receives and outputs corresponding measured values. It is possible that first taken a picture and this picture directly following the inclusion in the invention Way is processed.

Preferably the mean is taken from a group of means, which arithmetic means, geometric means; integrals weighted averages, combinations thereof, and the like.

Preferably the physical property is an intensity and in particular a threshold intensity. It would be too possible, the method with reference to other physical quantities, such as the color, or the like. More specifically, every single image pixel of the captured image in terms of intensity which it judges represents, so that the total invention Method is not an integrative but a differential method.

Preferably becomes the size of those area proportions determines that at a given value interval this characteristic Property corresponds. More specifically, as mentioned above, a certain threshold and the lower limit of this Value interval is the mentioned threshold, leaving only those Area proportions of the observed surface are taken into account, which are above this characteristic threshold. It will be in the image processing the specific actual Intensity values certain digital values, for example 1024 assigned different values.

at another method according to the invention for a variety of spatially resolved images this characteristic value is preferred together with the result value shown in the same illustration. That way you can a variety of measurements, for example, at different Areas of a body are compared with each other, wherein for each single measurement both the result value as well the characteristic value is taken into account.

at Another advantageous method is for a variety of spatially resolved images compared to the result the size of the particular area preferred applied in the same way. This can be a variety from single shots to a larger one Area can be carried out and the individual shots each be applied in the illustration. From this overall presentation can then be determined which of the individual partial areas the surface to be examined within a given Tolerance range, and which outside. Also can on a basis of a variety of spatially resolved Images are set to a tolerance value. So, for example an image taken on a fuel cap with one or more compared to the bonnet taken picture.

at Another preferred method is shown in the illustration Tolerance region determined, which determines whether given result values and characteristic values correspond to predetermined tolerance criteria.

at This method makes it possible to have a tolerance region both in terms of the results as well as in terms of the characteristic Values to be determined and, for example, in a two-dimensional Position a surface segment to characterize within whose acceptable values must be.

Preferably In the illustration, a tolerance zone is determined, which determines whether certain specified partial surfaces predefined tolerance criteria correspond. This can be used to assess, for example, whether certain Areas of a radiator hood coating still tolerable are or not. Advantageously, the tolerance zone is an ellipse. In order to Advantageously, the tolerance zone is an area that the sub-areas or the size of the faces opposite the intensities, whereas the one mentioned above Tolerance region versus the intensity values the other characteristic values. However, it is also possible to change the tolerance zone and the tolerance region to summarize a common tolerance area, for example in a three-dimensional representation by the formation of a tolerance ellipsoid within which are both the acceptable values in terms of intensity and acceptable values the area shares as well as the acceptable values in terms of of further characteristic value.

Preferably The tolerance zone is calculated using a variety of result values certainly. However, it is also possible that the tolerance zone is determined in advance, for example by manufacturer specifications or like. Also, the tolerance zone can be made using a variety of area sizes. Particularly preferred is a certain tolerance range with respect to Area sizes set and as well certain tolerance range with regard to the result values and the Tolerance zone is taking into account both tolerance ranges educated. To form the tolerance zone can continue from a Reference surface or of predetermined values for the size of the area shares and the Result value can be assumed. The term "tolerance range" is used doing a one-dimensional or only one size understood area.

at Another advantageous method is shown in the illustration Guidelines given which have different properties symbolize the surfaces to be examined. there For example, these lines may be lines act, which are each constant products of the area sizes and the result value or corresponding indirect proportionalities symbolize. Thus, the orientation lines are preferred characteristic of a product value resulting from the Result value and the size of the area shares results. About these guidelines is a rough classification into different surface types possible.

Preferably are the surfaces to be examined with coatings Effect pigments. However, it would also be possible in principle Other types of coatings by the invention Procedure to investigate.

Furthermore, the further characteristic value may be a value for the structuring of the surface or the so-called Coarseness. This Coarseness is a measure of how to repeat certain surface properties, or how certain surface properties act depending on the observation distance. To represent the Coarseness (coarseness), it is possible to represent a statistical parameter, for example against a certain resolution. In this connection, the German patent application DE 103 24 104 A1 the Applicant, the disclosure of which is hereby incorporated by reference into the subject matter of the present description.

So is possible, for example, a variance or scattering different intensity values on another axis compared to the respective area shares or Apply measurements. In this way, the individual can Area shares or measurements also with regard to their coarseness, d. H. characterized in terms of their coarseness become. As mentioned above, each is a result value Average of the individual intensities output. Advantageous will be in addition to this mean also about one Variance or dispersion, which in turn draw conclusions on the intensity distributions in the individual observed surface areas allows.

These for example, another variable such as the variance represent the contrast of a recorded image or its coarseness. Furthermore, it is also possible, the effect pigments to differentiate according to further characteristic features, such as z. B. their color. Instead of introducing another Axis could also be single measurement points in other ways be differentiated from each other, for example by different Color of the measuring points.

at a further advantageous method results in the location of Tolerance zone from at least one of the orientation lines. More accurate that is, the long semiaxis of the tolerance zone formed as an ellipse to the slope of the orientation line at a predetermined point customized. This will be explained in more detail with reference to the figures.

The The present invention is further directed to a quantitative device Determination of surface properties directed, wherein the device comprises a radiation device, which radiation directed to a surface to be examined, as well as a Radiation detector device, which from the surface recovers reflected radiation and a spatially resolved Output image that corresponds to the reflected radiation. Again, the surface on the radiation detector device displayed.

According to the invention the device has a processor device containing those Area proportions determined that have a specific physical Have property and that determines a result value for the physical properties of those area shares, which have the particular physical property, characteristic is, wherein the processor device is designed such that they another characteristic for the surfaces Value determined. Preferably, the device has an output device on which the result value and the other for the surface represents characteristic value together. It is also preferred evaluated here by the processor device a plurality of measured values or a variety of recorded images.

Farther can the process of the invention and the device according to the invention also used to catalog the individual readings shown, to find specific surface types. That's it For example, the determined result values are dependent on to apply an area fraction and for example to compare with a reference table in which a variety of comparable measurement results is included. This application is particular relevant in car repair area. Furthermore, the invention can be used to become one with a specially adapted formulation system certain surface effect or a certain appearance to create a surface. Furthermore you can issued by the method according to the invention Measured values for simulation purposes, in particular but not exclusively be used on the screen.

Further Advantages and embodiments will be apparent from the attached Drawings. Show:

1 a highly schematic representation of a device according to the invention;

2 a schematic comparison of two recorded images;

3 a corresponding integrative representation according to the prior art;

4 a first illustration according to the invention;

5 another illustration of the invention, and

6 another illustration of the invention.

1 a highly schematic representation of a device according to the invention for the quantitative determination of surface properties. This device has a radiation device 2 on which radiation, for example light, on a surface to be examined 8th directed. That from this surface 8th reflected and in particular scattered and reflected light is from a radiation detector device 4 added. More specifically, the surface on this radiation detecting device 4 which may for example comprise a CCD chip or a camera. The reference number 6 refers to a processor device which is that of the radiation detector device 4 recorded image evaluates and the reference number 9 to an output device.

This processor device 6 determines, based on a specific threshold, those surface segments at which the respective incident radiation exceeds a certain intensity value. In addition, the determined intensity values are also output in digitized form. Subsequently, averaging over all those intensity values which are above the determined threshold. This averaged value is then the result value to be evaluated. In an output device 9 this result value is plotted against the size of the determined area proportions. In addition, also a memory device 7 be provided, which stores the respective result values and the sizes of the respective surface portions for a plurality of measurements. When specifying the result values, normalization can be carried out by the mean sample illumination.

Farther the processor device also determines one or more others characteristic values, such as values for the contrast of the image are characteristic or values for the Color of the picture are characteristic. In determining this Values, it is possible only those area proportions to take into account the one mentioned above Feature. But it would also be possible in the determination of the further characteristic value the whole All area shares, which recorded or considered have to be taken into account.

2 shows a schematic comparison of two simulated images. To illustrate the problem underlying the invention, only two different intensity values I1 and I2 were assumed. In the upper part of the picture results as sum of the surface segments 14 a certain area proportion A1, wherein the individual area segments 14 each the constant uniform intensity value 11 have or represent. In the lower part of the picture results as the sum of the surface segments 16 a corresponding area proportion A2, in which case the individual area segments 16 each the (also only theoretical) intensity value 12 exhibit.

Here is the intensity value 12 twice as high as the intensity value 11 and conversely, the area A1 is twice as large as the area A2. This means that in the prior art the output product value I1 × A1 would be equal to the value I2 × A2 and so in the prior art the two surfaces would be considered as optically equivalent. It turns out, however, that there are actually significant differences between the two images, which, however, can not be detected with the integrative observation of the prior art.

However, if a further characteristic variable is represented, for example a variable that is characteristic of the contrast, then a distinction between the two in FIG 2 shown pictures possible.

3 is a corresponding linear representation according to the prior art, which is also a plurality of values 11a - 11e shows that have been recorded in different areas of a vehicle, for example on the body, on the wheel arch, on the bumper and the like. In this integral representation, it also follows here that the values are all in a similar range, which according to the prior art would indicate an equivalence of the surfaces. The corresponding values are also shown in the following figures.

4 shows a representation according to the invention, in addition to the value P is still a second axis with the characteristic value B is used. The value B is here a value representative of the contrast of the image. It can be seen that in this illustration the individual points 11a - 11e are relatively easy to distinguish. The value B may be, for example, a characteristic value for color evaluation. It is possible to evaluate individual camera pixels or the pixels of the detection device by color. For example, three colors would result in three different area shares and each area share could be assigned a specific color. Instead of a second axis, however, other types of evaluation would be conceivable. Thus, if there are a large number of knife values, for example, in the case of a division according to different colors, one could use several of them 3 use shown representations for the individual color components.

Also in this way it is possible to distinguish the individual measured values from each other. The reference number 22 in 4 refers to a tolerance region. This tolerance region indicates an area within which acceptable values lie, ie values that can not be visually distinguished by the viewer. In this case, for example, certain tolerance specifications or tolerance ranges with respect to the axis P and also the axis D can be assumed, and these values are respectively used as long and short axes of the ellipse. A long axis means that in this respect high tolerances possible and vice versa means a short axis that only small tolerances are allowed.

Instead of However, a color value could also be additional a representative value for coarseness or the contrast of the image are applied. It would be too possible, both a value for the coarseness as well as a color value optionally on a further or third Apply axis.

5 shows a further advantageous illustration of in 3 shown measured values, and other measured values, in which case the respective result values of the intensity are plotted against area proportions A and the number of pixels.

One recognizes here that the in 3 measured values considered to be equivalent are sometimes to be found in very different areas of the representation. This is especially evident when comparing the two values 11a and 11b , While these values in the integrative representation after 3 be very close to each other and thus imply similar surface properties is shown by 4 that the values are composed of very different result values and area proportions and thus can cause very different visual impressions.

The seven marked lines 10a - 10f are orientation lines in the application of the representation according to the invention. Along each individual line, the product of the area A and the intensity I is always constant. This means that with the method of the prior art on this line lying points can not be distinguished from each other.

In other words, according to the state of the art, only those differences can be detected that are at different distances from the marked lines. Since each individual point represents a different measurement, it becomes clear that measurements taken at different areas of the motor vehicle sometimes differ considerably from one another optically or that individual surfaces no longer optically meet the requirements. Through the orientation lines 10a - 10f At the same time grid areas are defined.

6 shows a further representation of the intensity relative to the surface portions.

In this case, however, the intensity or the area fraction is not specified here, but the difference value dJ or dA with respect to a respectively normalized value. The reference number 12 indicates a tolerance zone. Within this tolerance zone lying measuring points or areas of the surface to be examined are still defined as acceptable or can not be distinguished from each other by the observer. However, surface areas lying beyond this tolerance range can be perceived as different by the observer.

Here is this tolerance zone 12 designed in the form of an ellipse and understood to mean that even measuring points, the maximum distance in the tolerance zone after 6 have to one another, that is, at the opposite ends of the long half-axis L are not yet to be distinguished from the observer. In contrast, readings outside the tolerance zone 12 lie, are visually distinguished by the observer, of such surface areas, for example, lie at the directly opposite end of the ellipse. More precisely, for example, the measuring points 11a and 11b corresponding surface areas are visually distinguished from each other.

The long axis L of the tolerance ellipse 12 results from the slope of the orientation line 10b out 5 in a given normalization point. This may be the in 5 point (0, 0) shown, ie the crossing point of the two coordinates. However, it is also possible to use this point on the orientation line in 4 in advance, for example, according to manufacturer specifications.

The arrangement of the long semiaxis after the slope in the selected point is dependent on the position of this point on the orientation line 10a , If, as in 5 As this central point is shown to be in a region with large area proportions and low intensity, certain variations of the area proportions will have less effect on their absolute difference than corresponding deviations in intensity. This is best seen, considering that is already in 5 low intensity fluctuations have a strong effect on the product, but the differences or fluctuations in the area proportions have only a minor effect on the product.

If, for example, the selected central point were in a region with small area proportions and a correspondingly high intensity, the long semiaxis of the elliptical tolerance zone would also be in 5 much steeper. In the 4 and 5 could be applied on a third coordinate axis a measure of the Coarsness, ie the coarseness. This coarsness, also referred to as "texture," is another important characteristic aspect of the visual appearance of effect coatings.

there can on the additional axis, for example, a statistical Parameter, which is also a measure of the intensity distribution of the individual areas is to be spent with. This statistical parameter leaves a distinction to, whether in certain areas substantially the same Intensities are found, or whether in the said Surface areas these intensities vary greatly. For example, this statistic parameter may be a variance or scattering of the individual measured intensity values act.

Here is to be noted that the invention provided spatially resolved observation of the surface in principle allowed, for each individual pixel of the image capture element, like a camera, in each case the incoming intensity determine. A variety of these intensities, at least those intensities that are above the specified threshold are included in the calculation and next to it the result value is also the said statistical parameter such as the variance or the dispersion is spent.

Furthermore, it is possible at the in 6 to introduce a third axis for the values dB. This axis is shown here by dashed lines. dB here denotes the further characteristic value or its difference with respect to a reference value. However, it would also be possible, for example, in a division into different colors, in 6 shown diagrams for different color values apply in order to allow in this way the distinction. Furthermore, could also at the in 6 shown representation of the tolerance region 22 be drawn or a tolerance ellipsoid or another three-dimensional geometric shape are formed, which in turn the tolerance zone 12 and the tolerance region 22 combined together.

As mentions, is a corresponding spatially resolved Image evaluated. It is possible that this spatially resolved Picture is taken, for example, immediately before the evaluation and the evaluation follows accordingly. It but would also be possible, first one To capture a variety of spatially resolved images and then this Also, the evaluation of the images can be independent of their generation take place.

All Features disclosed in the application documents are considered to be essential to the invention as far as they are individually or in combination the prior art are new.

2

radiation device

4

Radiation detector device

6

processor means

7

memory device

8th

surface

9

output device

10a-10f

orientations

11a-11e

values

12

tolerance zone

14 16

surface segment

22

tolerance region

I, I1, I2

intensity values

A, A1, A2

area shares

d1

difference the intensities

there

difference the area shares

L

long half-axis of the tolerance zone 12

B

Another characteristic value

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10324104 A1 [0037]

Claims (14)

Method for the quantitative determination of surface properties, wherein a spatially resolved image of a surface to be examined ( 8th ) is evaluated with a multiplicity of measured values with the following steps: - analysis of the measured values for the determination of the area proportions (A) of the image which represent a specific physical property that can be characterized by the measured values; - determining a result value (I) of this physical property, this result value being characteristic of the physical property measurements of all those area components (A) determined by the analysis of the measured values; characterized in that, in addition to the result value, a further characteristic value (B) is determined for the surface and this further characteristic value (B) is displayed together with the result value (I) or a value dependent on this result value. Method according to claim 1, characterized in that that the further characteristic value (B) evaluates the contrast of the Picture represents. Method according to at least one of the preceding Claims, characterized in that the further characteristic Value (B) represents color properties of the evaluated image. Method according to at least one of the preceding claims, characterized in that the image to be evaluated is generated by applying radiation to the surface to be examined ( 8th ) and at least a portion of the radiation reflected from the surface is radiated by a radiation detector device ( 4 ) and this radiation detector device ( 4 ) outputs the measured values or data characteristic of these measured values. Method according to at least one of the preceding Claims characterized in that the result value (I) versus the size of the particular Area shares (A) is output. Method according to claim 5, characterized in that that the result value (I) is obtained by forming an average of the Values of the physical property of all those area shares (A) determined by the analysis of the image. Method according to claim 5 or 6, characterized that the mean is taken from a group of means is which arithmetic mean, geometric mean, Integral weighted averages, combinations and the like contains. Method according to at least one of the preceding Claims, characterized in that the physical Property an intensity and preferably a minimum intensity is. Method according to at least one of the preceding Claims, characterized in that the size that area is determined, which determines a certain Value interval characterized this characteristic property. Method according to at least one of the preceding Claims, characterized in that for a Variety of spatially resolved images of this characteristic Value together with the result value (I) preferably in the same Representation is shown. Method according to at least one of the preceding claims, characterized in that in the representation a tolerance region ( 22 ), which determines whether predetermined result values (I) and characteristic values (B) correspond to predetermined tolerance criteria. Method according to at least one of the preceding Claims, characterized in that to be examined Surface coatings with effect pigments are. Device for the quantitative determination of surface properties with a radiation device ( 2 ), which radiation onto a surface to be examined ( 8th ), with a radiation detector device ( 4 ) which receives the radiation reflected back from the surface and outputs a spatially resolved image which corresponds to the reflected radiation, characterized in that the device has a processor device which determines those surface areas of the surface ( 8th ) having a certain physical property and determining a result value (I) characteristic of the physical properties of those area portions having the determined physical property, and wherein the processor means determines another surface characteristic value (B) , Device according to claim 13, characterized that the device has an output device, which the Result value (I) and the other for the surface characteristic value (B) together.