JPH08122024A - Thickness measuring apparatus of coating film - Google Patents

Abstract

PURPOSE: To obtain a thickness measuring apparatus with which a film thickness can be detected with high accuracy by picking up an undried coating surface immediately after a coating operation so as to be image-processed, finding the wavelength distribution of an uneven waveform on the coating surface on the basis of processed data, and computing the thickness of a coating film on the basis of the wavelength distribution. CONSTITUTION: While an object 1 to be coated is being moved at a prescribed speed on a coating line, it is coated. An image pickup part 2 picks up the image of the surface of a wet state after about one to two minutes from a coating operation, and its image data is processed such as binary-coded or the like by an image processing part 3. The processed data is inputted to a wavelength arithmetic part 4, a power spectrum frequency is analyzed, the power spectrum of the unevenness of a coating surface is computed, and a peak wavelength in a long-wavelength region is found. A film-thickness arithmetic part 7 operates a coating film thickness on the basis of the peak wavelength. The value of the film thickness is displayed on a display device 8, it is sent to a coating- condition control system 9, it is fed back to the operating condition of a coating gun 10, and a desired film thickness is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating film thickness measuring technique capable of measuring a coating film thickness in an undried state immediately after applying a coating, and particularly to a coating film suitable for measuring a very thin film thickness. Regarding film thickness measurement technology.

[0002]

2. Description of the Related Art As an apparatus for measuring the coating film thickness in a non-dried state immediately after coating, there are, for example, a contact type apparatus utilizing a needle gauge, or an electromagnetic or eddy current type non-contact type apparatus. FIG. 21 is a cross-sectional view showing the principle of an example of a measuring device using magnetism in the above conventional devices. FIG.
First, as shown in (a), first, the non-contact film thickness sensor 82 is preliminarily positioned at the short distance h _{0 so as} to face the coating surface of the object 81 to be coated of a steel plate. A transmission / reception coil (not shown) provided in the non-contact film thickness sensor 82 generates a magnetic field between the object 81 to be coated and the non-contact film thickness sensor 82. In this state, when the wet coating material 83 is applied to the surface of the coating object 81, the magnetic field between the coating object 81 and the non-contact film thickness sensor 82 after coating is attenuated by the electromagnetic resistance due to the coating film thickness. , It is detected by the transmitting and receiving coil in a state where it is lower than before painting. In this way, the coating film thickness can be measured by detecting the change in the magnetic flux that attenuates in proportion to the film thickness h. However, in the conventional film thickness measuring device as described above, the distance between the object to be coated 81 and the non-contact film thickness sensor 82 is set to a predetermined close distance before coating,
Since it is necessary to maintain the positional relationship precisely before and after painting, it is necessary to keep the sensor set to the close distance even during painting, which is not practical. In addition, since it is necessary to perform the measurement twice before and after coating, it is troublesome and the measurement accuracy is poor. Further, the contact type device using the needle gauge has a problem that the coating quality is deteriorated because the coated surface is scratched.

In order to solve the above problems, the present applicant has already applied for a device for measuring the coating film thickness in a non-contact manner based on the roughness of the undried coating surface immediately after coating with the coating material (Japanese Patent Application No. 2000-242242). No. 4-306966). The above measuring device measures the roughness of the undried coating surface immediately after coating with an optical surface roughness meter or an imaging device, and the wavelength of the uneven waveform of the coating surface, and based on them, the film thickness in the undried state. It measures the (wet film thickness) and predicts the film thickness after drying (dry film thickness).

[0004]

As described above, the conventional contact type apparatus has a problem that the coating quality is deteriorated because the coated surface is scratched, and the non-contact apparatus utilizing magnetism is used. However, there is a problem that the measurement is troublesome and the measurement accuracy is poor. Further, in the prior application of the present applicant, which has solved the problem of the conventional apparatus as described above, it is possible to perform accurate measurement easily in a non-contact manner. Very thin coating, that is, extremely thin coating having a film thickness of about several tens of μm, has the following problems. That is, in the above-mentioned prior application, the film thickness is obtained from the amount of change over time of the roughness of the undried coating surface, but when the film thickness is extremely thin as described above, the volatilization rate of the volatile components of the paint is high. Therefore, the viscosity rapidly increases, so the amount of change in roughness over time becomes extremely small, making accurate measurement difficult,
Therefore, there is a problem that the measurement accuracy of the coating film thickness is significantly reduced.

The present invention is a further improvement of the applicant's prior application as described above. Even if it is a very thin coating of about several tens of μm such as an overcoat base coating for automobile body coating, the film thickness can be accurately adjusted. An object is to provide a coating film thickness measuring device capable of measuring.

[0006]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, the invention described in claim 1 is
As shown in FIG. 1A, an image pickup means 100 for picking up an image of the undried coating surface immediately after applying the paint, an image processing means 101 for image-processing the image information from the image pickup means, and a processing by the image processing means. The wavelength calculation means 102 for calculating the wavelength distribution of the corrugated waveform on the coating surface based on the image processing data, and the film thickness calculation for calculating the coating film thickness based on the wavelength distribution calculated by the wavelength calculation means. Means 103
And Each of the above means corresponds to, for example, the following means in the embodiment shown in FIG.
That is, the image pickup unit 100 corresponds to the image pickup unit 2, the image processing unit 101 corresponds to the image processing unit 3, the wavelength calculation unit 102 corresponds to the wavelength calculation unit 4, and the film thickness calculation unit 103 corresponds to the film thickness calculation unit 7. Further, as described in claim 2, the wavelength calculating means 102 obtains a peak wavelength in a long wavelength region in the power spectrum of the corrugated waveform on the coating surface, and the film thickness calculating means 103 calculates the long wavelength. The film thickness in the wet state is calculated from the relationship between the value of the peak wavelength in the wavelength region and the coating film thickness obtained by experiments in advance, and this is output as the film thickness value.

Next, the invention described in claim 3 is as shown in FIG.
As shown in (b), the following configuration is added to the invention described in claim 1. That is, the imaging means 100 images a plurality of locations on the coating surface, the wavelength calculating means 102 calculates a plurality of wavelength distributions corresponding to the plurality of coating surfaces, and the plurality of wavelength distributions are calculated. A wavelength averaging means 105 for averaging and a coating condition input means 104 for inputting coating conditions including at least the type of coating material are provided, and the film thickness calculating means 103 is
The coating film thickness is calculated based on the average value of the wavelength distribution obtained by the wavelength averaging means 105 and the coating conditions. The above configuration corresponds to, for example, the embodiment shown in FIG.

Next, the invention described in claim 4 is as shown in FIG.
As shown in (c), the following configuration may be added to the invention described in claim 3 above. That is, at least the non-volatile component information (content rate or content) after coating of the paint
Coating condition input means 104 for inputting coating conditions including
A dry film thickness calculating unit 106 for calculating the film thickness in the dry state based on the film thickness in the wet state obtained by the film thickness calculating unit 103 and the coating condition is added.
It should be noted that the coating condition input means 104 is also equivalent to one that inputs a volatile amount instead of a non-volatile component. The above configuration corresponds to, for example, the embodiment shown in FIG. 13 described later.

Next, the invention described in claim 5 is the invention according to claim 3.
Further, in claim 4, a plurality of image pickup means are provided for picking up images of the undried coating surface immediately after the coating is applied, respectively, at different points on the coating surface, and image information of the plurality of points picked up by these image pickup means is sequentially processed. To do. Note that FIG. 1D shows a block diagram corresponding to claim 4. The above configuration corresponds to, for example, the embodiment shown in FIG.

Next, the invention according to claim 6 is shown in FIG.
As shown in (a), a plurality of image pickup means 100 for picking up an image of the undried coating surface immediately after applying the coating material at different points on the coating surface, and image processing of the image information from the plurality of image pickup means, respectively. Image processing means 101
And a wavelength calculation means 102 for calculating the wavelength distribution of the corrugated waveform on the coating surface for each of the above points based on the image processing data processed by the image processing means, and a coating condition including at least the type of coating material is input. A film for calculating the coating film thickness at each of the above-mentioned locations based on the coating condition inputting means 104, the plurality of wavelength distributions calculated by the wavelength calculating means, and the coating condition from the coating condition inputting means. Average thickness calculating means 103 and average thickness calculating means 1 for calculating the average thickness of the coated surface based on the calculation results of the above thickness calculating means.
07, and is configured to perform parallel processing on image information at a plurality of locations imaged by a plurality of imaging means. Although FIG. 2A illustrates the case where a plurality of image processing means 101, a plurality of wavelength calculation means 102, and a plurality of film thickness calculation means 103 are provided, image information from a plurality of image pickup means is displayed. As long as it is a device that can process each independently, only one means may be used. The above configuration
For example, it corresponds to the embodiment of FIG. 15 described later.

Next, the invention according to claim 7 is as shown in FIG.
As shown in (b), the following configurations are added to the invention described in claims 1 to 6. That is,
Curved surface calculation means 1 for obtaining curved surface information of a coated surface based on at least one of the image processing data processed by the image processing means 101 and the wavelength distribution calculated by the wavelength calculation means 102.
08, and a curved surface correction calculation unit 109 that performs curved surface correction processing according to the result obtained by the curved surface calculation unit 108 with respect to the wavelength distribution calculated by the wavelength calculation unit 102. Note that FIG. 2B illustrates the case where the configuration is added to the configuration of FIG. The above configuration corresponds to, for example, the embodiment shown in FIG. 16 described later.

[0012]

According to the first aspect of the present invention, the wavelength distribution of the uneven waveform of the coating surface is calculated from the image information of the undried coating surface, and the coating film thickness is calculated based on the wavelength distribution. Specifically, as described in claim 2, the peak wavelength of the long wavelength region in the power spectrum of the corrugated waveform of the coating surface is obtained, and from the relationship between the value of the peak wavelength and the coating film thickness obtained in advance by the experiment. , Calculate the film thickness in the wet state. As described above, in the present invention, the roughness measurement as in the prior application is not performed, only the peak wavelength of the long wavelength region in the power spectrum of the uneven waveform is calculated, and the value and the coating film obtained in advance by an experiment The film thickness is determined from the relationship with the thickness. Therefore, since it is not affected by the viscosity of the coating film after coating, accurate film thickness measurement can be performed even when the film thickness is as thin as several tens of μm. The film thickness obtained as described above can be used by displaying the numerical value as it is, or can be given as a numerical value for automatic control of the coating line.

The third aspect of the present invention is to image a plurality of locations on the coating surface and calculate the film thickness using the average value of the wavelength distributions of the plurality of locations. By averaging the values at a plurality of points in this way, a more accurate film thickness can be measured.

The calculation accuracy can be improved by giving information such as the type of paint by the coating condition input means 104. Next, the invention according to claim 4 is
The content information of the non-volatile component of the coating material is input from the coating condition input means 104, and the dry film thickness after drying is calculated from the information and the measured wet film thickness. That is, since the dry film thickness is the state after the volatile components have evaporated from the wet coating film, the dry film thickness can be calculated by knowing the content of the non-volatile component of the paint and the wet film thickness. I can.

Next, the invention according to claim 5 is provided with a plurality of image pickup means, and is configured to sequentially process image information of a plurality of places imaged by these image pickup means. By providing a plurality of imaging means in this way, a plurality of locations on the coating surface can be imaged in a short time, so that accurate film thickness calculation can be performed quickly. Next, the invention according to claim 6 is
The image processing means 101, the wavelength calculation means 102, and the film thickness calculation means 103 also perform the processing in parallel, and the value obtained by averaging the obtained plurality of film thicknesses is used as the final film thickness value. In this way, by accurately processing the image information of a plurality of positions imaged by a plurality of imaging means, an accurate film thickness calculation can be performed more quickly. Next, the invention according to claim 7 is provided with a curved surface correction function when the surface to be coated is a curved surface. As a result, accurate film thickness measurement can be performed even on a curved surface.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a first embodiment of the present invention and is a block diagram when the present invention is applied to an automatic coating line. First, the outline of the entire configuration will be described with reference to FIG. Reference numeral 1 is a body to be coated (for example, a vehicle body), which is coated while moving on a coating line at a predetermined speed. Two
Is an image pickup unit (details will be described later) for picking up an image of the wet coating surface immediately after coating. The image is taken after a predetermined time (for example, 1 to 2 minutes) after spraying the paint. Therefore, the imaging unit 2 is installed at a position where the object to be coated 1 arrives after 1 to 2 minutes, for example, according to the moving speed of the coating line. The image of the painted surface captured by the image capturing unit 2 is subjected to image processing such as binarization by the image processing unit 3. The image processing unit 3 is composed of an image memory that stores image information and a computing device such as a computer. The image processing data processed by the image processing unit 3 is sent to the wavelength calculation unit 4. The wavelength calculation unit 4 performs power spectrum frequency analysis (for example, fast Fourier transform: FFT) of the input image processing data, and from the input image data, a power spectrum PS of unevenness on the coating surface (details described later).
To calculate.

Further, the film thickness calculation unit 7 calculates the film thickness h in the wet state based on the power spectrum PS obtained by the wavelength calculation unit 4 (details will be described later). The wavelength calculation unit 4 and the film thickness calculation unit 7 are configured by a calculation device such as a computer. The coating film thickness h obtained as described above is displayed on the display device 8 such as a liquid crystal display device or a CRT display device and presented to the worker, and is also sent to the coating condition control system 9 to be transferred to the coating gun 10. The operating conditions (paint discharge rate, bell rotation speed, air pressure, etc.) are controlled so as to be kept at the optimum conditions for achieving the desired coating film thickness.

Next, the detailed structure and operation of each part will be described. First, the image pickup unit 2 will be described. FIG. 4 is a cross-sectional view showing an example of the image pickup unit 2. As shown in FIG.
The basic structure of the image pickup unit includes a light source 31, a light / dark pattern plate 32,
It is composed of a reflecting mirror 33, a lens 34 and a CCD camera 35. The light / dark pattern plate 32 has a predetermined interval (for example, 1 m).
It is an opaque plate (or a transparent plate on which opaque stripe patterns are printed at predetermined intervals) provided with linear slits at m intervals). Then, a parallel light beam from the light source 31 is radiated onto the coating surface from an oblique direction through the light-dark pattern plate 32, the reflecting mirror 33, and the lens 34 to form a striped pattern corresponding to the slit on the object to be coated. This striped pattern is a waveform that is distorted according to the irregularities on the object to be coated (see FIG.
The waveform is as shown in. The reflected light is imaged by the CCD camera 35, and the distorted striped pattern, that is, information on the surface irregularities is input. The image information of the striped pattern as described above is subjected to image processing by the image processing unit 3, and power spectrum frequency analysis (for example, fast Fourier transform processing: F
FT) to obtain the power spectrum PS (especially the peak wavelength λp in the long wavelength region).

FIG. 5 is a frequency characteristic diagram of the power spectrum PS, in which the vertical axis represents the power spectrum PS and the horizontal axis represents the frequency f (the reciprocal of the wavelength λ f = 1 / λ). In FIG. 5, the first peak waveform is the power spectrum of the basic waveform formed by the basic stripes corresponding to the slits, and the second peak waveform is the long wavelength region (10) of the uneven waveform on the coating surface.
Power spectrum corresponding to ~ 1 mm), the third peak waveform is the uneven wavelength waveform in the middle wavelength region (1 to 0.1 mm).
The fourth peak waveform shows the power spectrum corresponding to the short wavelength region (0.1 mm or less) of the uneven waveform. In the above power spectrum waveform, the peak wavelength in the long wavelength region of the uneven waveform, that is, the wavelength λ corresponding to the peak value of the second peak waveform.
Since p has a correlation with the coating film thickness as described later, the coating film thickness can be measured by obtaining the wavelength λp.

Next, the film thickness calculation processing in the film thickness calculation unit 7 will be described. A basic experiment of the adhesion mechanism of paint particles as shown in FIG. 6 (described later in detail), specifically, the film thickness was changed by controlling the paint spraying time, and the wavelength distribution on the paint film surface at that time was measured. According to the result of the experiment, it was confirmed that the particles adhering to the surface to be coated grow due to particle bonding as shown in FIG. Further, it has been derived that the relationship between the coating film thickness h and the wavelength λ of the unevenness of the coating surface has the relationship of the following (Equation 1) or (Equation 2), and is as shown in FIG. 11.

[0021]

[Equation 1]

H = k '× λ-k "(Equation 2) However, k, k', k", α: constant determined depending on the paint, as can be seen from the above formulas and the characteristics of the figure, the particle size of the adhered particles (That is, the wavelength of the unevenness of the coated surface) increases as the film thickness increases, because the number of bonded particles increases. That is, it is shown that the growth of the coating film surface depends on the film thickness value which is a coating condition. When estimating the film thickness value, the above equation (1) or equation (2) is used. It is possible to calculate the film thickness value from the wavelength of the unevenness of the coating film surface.

The principle of coating film thickness measurement in the present invention will be described in detail below. First, with reference to FIG. 6, a process of adhering paint particles to a coating surface and forming a coating film surface during coating will be described. As shown in FIG. 6 (a), atomized paint particles are sprayed from the paint gun toward the paint surface. At this time, the average particle size of the paint particles is basically determined by the paint conditions such as paint velocity (below), air velocity (below) and paint physical properties (below). However, the above-mentioned items are as follows. Discharge rate of coating gun Bell rotation speed of coating gun Applied voltage Air pressure Paint physical properties (viscosity, surface tension, density) Bell rotation speed is the rotation speed of the rotating body that atomizes the paint, and applied voltage is the paint It is a static voltage (about 50 kV) applied to add static electricity to the particles, and the air pressure is an atmospheric pressure for creating a wall of airflow around the paint particles so that the paint particles do not scatter around. The paint particles sprayed as described above collide with the painted surface and adhere in a crushed form.

Next, as shown in FIG. 6B, in the initial stage of coating film formation, the small paint particles that have adhered are combined with the large paint particles to form larger particles. Then, the bonding of particles further progresses, and the initial coating film surface is formed by the surface tension and the boundary tension. As described above, since the coating film is formed by the adhesion and bonding of the particles, the initial coating film surface condition is the particle diameter r of the large coating particles, the particle collision velocity vx,
It depends on the physical properties of the coating (surface tension γ, viscosity η) and the like. For example, in the case of a top coating, the height of the unevenness on the surface of the initial coating film is about several to several tens of μm, and the wavelength distribution of the unevenness is 3 to 6 μm.
It was confirmed that the long wavelength region of about mm is dominant. Experiments have confirmed that there is a correlation between the peak wavelength λp in the long wavelength region and the particle diameter r of large paint particles. Next, as shown in FIG. 6C, the coating film surface after the initial coating film formation is gradually flattened by the leveling force (composite force of surface tension γ and gravity g). This flattening speed is determined by the above-mentioned leveling force, coating material properties (surface tension γ, viscosity η) and film thickness h. For example, in the case of a topcoat paint, it has been confirmed that the flattening speed is a time constant of several tens of seconds to several hundreds of seconds.

Next, the relationship between the paint particle size and the unevenness of the coating film surface will be described in detail with reference to FIGS. Figure 7
As shown in, the particle diameter of the paint particles sprayed from the coating gun is r, and the width of the adhered particles attached to it is λ /
2. If the thickness (peak value) is h, a coating film surface having irregularities of wavelength λ is formed. The width of the adhered particles λ / 2
The relationship between the wavelength and the wavelength λ is experimentally obtained,
It has been confirmed that the value is almost this level. The paint particle diameter r in the above case is expressed by the following equation (3).

[0026]

(Equation 3)

When the above theoretical formula is shown in a graph, a curve as shown by the broken line in FIG. 8 is obtained. However, in reality, since the adhered particles are bonded, the characteristics shown by the solid line in FIG. 8 are obtained. The characteristic obtained in this experiment is expressed by a mathematical expression as shown in the following (Equation 4).

[0028]

[Equation 4]

The relationship between the peak wavelength λp of the unevenness and the paint particle diameter r obtained in the above-mentioned experiment is analyzed in consideration of the bond of the adhered particles. First, as shown in FIG. 9, the adhered particle diameter R increases sequentially as the coating time increases.
When this relationship is shown by a mathematical expression, it becomes as shown in the following (Equation 5).

[0030]

(Equation 5)

In FIG. 9, the application time is the duration of application at one location, the initial particle size is the paint particle size before adhesion, and the adhered particle size is the particle size when first applied. Is. The diameter R of the adhered particles gradually increases as the coating time increases because the particles that are sequentially coated combine.

Further, FIG. 10 is a characteristic diagram comparing the relationship between the coating time and the uneven wavelength of the coating surface with the measured value (broken line) and the result obtained from the power spectrum by frequency analysis. As can be seen from FIG. 10, the value obtained from the power spectrum is in good agreement with the actually measured value. Therefore, the particle diameter R of the adhered particles can be obtained by using the uneven wavelength (peak wavelength λp of the long wavelength) obtained from the power spectrum. Furthermore, in an automatic coating machine, the coating time is constant, so the paint particle diameter r can also be determined by the following equation (6). 2r (t) = λp (t) (Equation 6) Based on the above consideration, the peak wavelength λp of the long wavelength region of the unevenness obtained from the power spectrum is basically used by the equation (Equation 4). The paint particle diameter r can be obtained. Specifically, if the characteristics shown in FIG. 8 are obtained by an experiment and then the respective coefficients ks and a of the equation (4) are obtained in advance, the paint particle diameter r can be calculated by using the peak wavelength λp obtained from the captured image. You can ask. Since the particle size r of the paint particles corresponds to the degree of atomization of the paint, the particle size r of the paint particles may be used as it is to represent the degree of atomization, or the reciprocal of r or a reference value. It is also possible to express the degree of atomization by using the percentage and the like.

Further, as shown in FIG. 9, the adhered particle diameter R gradually increases as the coating time, that is, the film thickness increases. This relationship is further analyzed by measuring the film thickness value, not the coating time, and analyzing the relationship between the film thickness and the adhered particle size, that is, the relationship between the film thickness and the wavelength of the irregularities on the coating surface. The relationship with the peak wavelength λp) is as shown in FIG. That is, as the film thickness increases, the peak wavelength λp also increases, and the relations shown in the equations (1) and (2) are experimentally obtained. Therefore, the film thickness in the wet state can be calculated by obtaining the peak wavelength λp in the long wavelength region of the corrugated waveform on the surface of the coating film.

In the embodiment of FIG. 3, the wavelength calculator 4
Then, the power spectrum PS of the corrugated waveform on the coating surface is obtained from the input image processing data, and the peak wavelength λp in the long wavelength region is calculated. Then, in the film thickness calculation unit 7, the characteristics of FIG. 11 previously obtained by experiments (Equation 1 or Equation 2)
Is used to calculate the coating film thickness value from the peak wavelength λp. Note that, in the above calculation, the characteristics of FIG.
The coefficient values of the formulas (1) and (2) are calculated according to the type of paint such as intermediate coat, top coat base, and clear top coat (not shown in FIG. 3 and described in the following embodiment). change.

As described above, in this embodiment, only the peak wavelength in the long wavelength region in the power spectrum of the uneven waveform was calculated from the image of the undried coating surface after coating, and the value and the value were obtained in advance by experiments. The film thickness is determined from the relationship with the coating film thickness. Therefore, since it is not affected by the viscosity of the coating film after coating, accurate film thickness measurement can be performed even when the film thickness is as thin as several tens of μm. Therefore, even on an extremely thin coating surface such as the base coating of an automobile body, it is possible to easily measure without contact immediately after coating, and feedback control of coating conditions can be performed immediately, thus maintaining and improving coating quality. It is possible to significantly reduce the number of coating film thickness measurement steps.

Next, FIG. 12 is a block diagram of a second embodiment of the present invention. Generally, in an automated coating line such as car body painting, various paints are used such as topcoat, middlecoat, or difference in paint color, so it is necessary to enter conditions according to the type of paint. . Further, in the case of a large body to be coated such as a vehicle body, since the sprayed area is large, the coating conditions may not always be uniform depending on the coating site. Therefore, in order to perform accurate measurement, it is desirable to image a plurality of locations on the coated surface and calculate the film thickness using the average value of the peak wavelength λp at each of those locations. In the embodiment of FIG. 12, for the above reason, the image pickup unit 2 picks up an image of a plurality of locations on the painted surface, sequentially processes the image information, and the wavelength averaging unit 5 determines the obtained peak wavelengths λp. Averaging
The coating condition input unit 6 is provided to input information according to the type of coating, and the film thickness calculation unit 7 calculates the film thickness according to the averaged peak wavelength λp value and the coating condition. Is configured. The painting condition input unit 6 is, for example, an input means such as a keyboard, and is necessary information according to the type of paint by the operator's operation (coefficients of the above-mentioned mathematical formula, etc.).
Enter

Next, FIG. 13 is a block diagram of a third embodiment of the present invention. In this embodiment, a dry film thickness calculator 11 for calculating the dry film thickness after drying is added to the structure of the embodiment shown in FIG. Calculation of the dry film thickness requires information on the content of the non-volatile components in the coating material, that is, the components remaining after drying. Therefore, in this embodiment, the content of non-volatile components NV of the paint is input from the paint condition input unit 6.
Then, the dry film thickness H is calculated by the following equation (7) from the wet film thickness h and the non-volatile content NV which are obtained by the above calculation. H = NV × h (Equation 7) Even if the volatile component content (= 1-NV) is used instead of the nonvolatile content N.V, the dry film thickness H is similarly obtained. It can be calculated.

Next, FIG. 14 is a block diagram of a fourth embodiment of the present invention. In the embodiments shown in FIGS. 12 and 13, since the image pickup unit 2 is used to sequentially pick up images at a plurality of locations, there is a problem that the measurement time becomes long and the measurement procedure becomes complicated. Therefore, in this embodiment, a plurality of image pickup units 2-1 and 2-2 are provided, and image information of a plurality of places is input at the same time. As a result, the measurement time can be shortened and the measurement procedure can be simplified.

Next, FIG. 15 shows a fifth embodiment of the present invention. In this embodiment, in addition to the image pickup unit, an image processing unit, a wavelength calculation unit, and a film thickness calculation unit are provided in parallel in the embodiment of FIG. 14, and the image information picked up by the respective image pickup units is subjected to parallel calculation processing and is obtained. A value obtained by averaging a plurality of film thickness values by the average film thickness calculation unit 12 is used as a film thickness value. By parallelizing each calculation in this way, the film thickness measurement process can be further speeded up.

Next, the curved surface correction calculation when the surface to be coated is a curved surface will be described. In the embodiments described so far, the peak value of the uneven wavelength is obtained from the image information of the coated surface, and the film thickness value is calculated from this. However, when there is a curved surface on the painted surface, as in the case of a car body, the captured image is curved according to the curvature,
It becomes difficult to accurately measure the uneven wavelength of the surface, which may cause an error in the measurement result. 16
It is a block diagram of the 6th Example of this invention, and shows the Example which added the said curved surface correction function. Note that this embodiment shows a case where the curved surface correction is added to the embodiment of FIG. 13, but it is of course possible to combine it with other embodiments. In FIG. 16, the curved surface calculation unit 19 is the image processing unit 3.
Curved surface information of the painted surface is obtained based on at least one of the image processing data processed in step 1 and the wavelength distribution calculated by the wavelength calculator 4. Further, the curved surface correction calculation unit 20 performs curved surface correction processing on the wavelength distribution calculated by the wavelength calculation unit 4 according to the result obtained by the curved surface calculation unit 19. The curved surface calculation unit 19 and the curved surface correction calculation unit 20 are configured by a calculation device such as a computer. Other configurations are the same as those in FIG.

Next, the curved surface correction in this embodiment will be described in detail. 17A and 17B are examples of images captured by the image capturing unit 2. FIG. 17A shows an image when the coated surface is a flat surface, and FIG. 17B shows an image when the coated surface is a curved surface (curved in the x-axis direction).
When the coated surface is flat, as shown in (a), the outer shape of the image becomes the same circle as the image projected from the image pickup unit 2 in FIG. 4, and the striped pattern of the light-dark pattern plate 32 becomes uneven on the coated surface. Appears in a distorted form accordingly. On the other hand, in the case of a curved surface,
As shown in (b), the curved surface has an elliptical shape with a contracted direction. In FIG. 17, the intermittent direction of the striped pattern is x
The axis is the y-axis, which is the direction perpendicular to the axis.

The curvature calculation unit 19 derives the curvature r of the coating surface by the following procedure using the image data as described above.
First, as shown in FIG. 17B, the maximum lengths (bright area) x and y in the x-axis and y-axis directions of an elliptical image area are derived on the image. The derivation method calculates the maximum length by searching the binarized initial bright point position on each axis from the left and right. Next, since the coating surface having a convex curvature generally acts as a concave lens, the image pickup unit 2 of FIG. 4 and the optical system of the coating surface having a convex curved surface are as shown in FIG. From the distance constant of such an optical system, the curvature r in the x direction of the coating film surface is given by the following (Equation 8). The y direction can be calculated in the same manner.

[0043]

(Equation 8)

However, x: measured x-axis maximum length x ₀ : x-axis maximum length when coating surface is flat (known value) L ₁ : distance between CCD camera 35 and coating surface L ₂ : light source Distance between 31 and coating surface Next, the correction coefficient K by the curvature r for the wavelength λ is obtained from the relationship between the curvature r and the correction coefficient K shown in FIG. Note that FIG. 19 is a relational expression obtained by experiments, in which the vertical axis represents the correction coefficient K and the horizontal axis represents the reciprocal of the curvature r (1 / r = R: curved surface). Based on the correction coefficient K obtained as described above, the peak wavelength λ in the long wavelength region in the above film thickness calculation.
Correct the value of p. That is, when the measured wavelength in the curved surface portion is λp, the actual wavelength λp ′ corresponding to the plane corrected for it is shown by the following (Formula 9).

[0045]

[Equation 9]

However, a: constant R = 1 / r If the film thickness is calculated as described above using the actual wavelength λp ′ calculated as described above, the film thickness can be accurately measured even on a curved surface. I can. In the embodiment shown in FIG. 16, the curved surface calculation unit 19 performs the calculation for obtaining the correction coefficient K, and the curved surface correction calculation unit 20 performs the calculation for obtaining the actual wavelength λp ′. In addition to the wet film thickness h, the display 8 shows the wavelength λp, the corrected actual wavelength λp ′, and the curvature r of the coating surface.
Etc. may be displayed. Also, in the above description, x
The curvature r is obtained and corrected only in the axial direction. This is because the intermittent direction of the striped pattern is set as the x-axis as shown in FIG. 17, but the curvature is similarly obtained in the y-axis direction, and the correction coefficient K is obtained using the larger value of the curvature. You may comprise.

Next, another method of curved surface correction will be described. As shown in FIG. 5, in the frequency characteristic of the power spectrum PS, the first peak waveform is the image pickup unit 2
The power waveform and the peak waveform of the basic waveform by the basic stripes corresponding to the slit are the power spectrum corresponding to the long wavelength region (about 10 to 1 mm) of the uneven waveform of the coating surface. Although the peak values of these power spectra change according to the curvature of the coated surface, according to the experiments by the present inventors, the peak frequency f of the basic fringe and the peak frequency f ′ (= 1 / λp) of the long wavelength region are shown. Have been found to have a certain relationship regardless of the curvature of the painted surface. FIG. 20 is a characteristic diagram showing the curved surface dependence of the frequency characteristic of the power spectrum PS. 20, the vertical axis represents the power spectrum PS,
The horizontal axis represents the frequency f (1 / λ), the solid line (A) shows the characteristics of the painted surface being flat, the dotted line (B) shows the characteristics when the painted surface has a curvature r ₁ , and the broken line (C) shows the curvature of the painted surface. The characteristics in the case of r ₂ (r ₁ <r ₂ ) are shown.

As can be seen from FIG. 20, the peak frequency increases (peak wavelength λp decreases) as the curvature increases, but it has been found that the relationship of the following (Equation 10) holds regardless of the curvature.

[0049]

[Equation 10]

However, f ₀ : basic fringe peak frequency on a plane f ₀ ′: long wavelength peak frequency on a plane f _r : basic fringe peak frequency on a curvature r f _r ′: long wavelength peak frequency on a curvature r From equation 10), the long wavelength peak frequency f in the plane
₀ 'is determined by the following equation (11).

[0051]

[Equation 11]

In the equation (11), the value of the basic fringe peak frequency f ₀ in the plane is a known value that can be measured in advance. Further, the basic fringe peak frequency _fr and the long wavelength peak frequency _fr 'when the curvature is r are obtained as actual measurement values by the image processing described above. Therefore, in order to convert the long-wavelength peak frequency f _r ′ with the curvature r to the value f ₀ ′ on the plane, f
to _r 'may do it by multiplying the f ₀ / f _r. In the case of expressing with the wavelength λ as described in the above film thickness calculation, it may be corrected as in the following (Equation 12).

[0053]

(Equation 12)

Where λ ₀ : basic fringe peak wavelength on a plane λ ₀ ′: long wavelength peak wavelength on a plane λ _r : basic fringe peak wavelength on a curvature r λ _r ′: long wavelength peak wavelength on a curvature r According to the method, the curved surface can be easily corrected only by obtaining the basic fringe peak wavelength λ _r and the long wavelength peak wavelength λ _r '. When the above method is applied to the embodiment of FIG. 4, the curved surface calculation unit 19 performs a calculation to obtain λ _r and λ _r ′ from the image processing data of the image processing unit 3, and the curved surface correction calculation unit 20 the calculation from the values of lambda ₀ which has been previously stored their values determine the lambda ₀ 'may be configured to perform.

[0055]

As described above, according to the present invention,
Calculate the wavelength distribution of the uneven waveform of the coating surface from the image information of the undried coating surface, and calculate the coating film thickness based on the wavelength distribution. Specifically, the long wavelength in the power spectrum of the uneven waveform of the coating surface The peak wavelength of the area is obtained, and the film thickness in the wet state is calculated from the relationship between the value of the peak wavelength and the coating film thickness obtained in advance by an experiment. Even if it is thin, accurate film thickness measurement can be performed. Further, more accurate film thickness can be measured by imaging a plurality of locations on the coating surface and calculating the film thickness using the average value of the wavelength distributions of the plurality. Further, the dry film thickness after drying can be calculated from the measured wet film thickness. Further, in the case of including a plurality of image pickup means and sequentially processing image information of a plurality of places picked up by those image pickup means, since a plurality of places on the coating surface can be picked up in a short time, accurate film thickness calculation can be performed quickly. You can do it. Further, in the case of parallel processing of image information at a plurality of positions imaged by a plurality of imaging means, accurate film thickness calculation can be performed more quickly. Further, in the case where the curved surface correction is provided in the case where the surface to be coated is a curved surface, it is possible to obtain an effect that the film thickness can be accurately measured even when the object to be coated is a curved surface.

[Brief description of drawings]

FIG. 1 is a diagram showing a part of functional blocks of the present invention.

FIG. 2 is a diagram showing another part of the functional blocks of the present invention.

FIG. 3 is a block diagram of a first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing an example of an imaging unit 2.

FIG. 5 is a frequency characteristic diagram of a power spectrum PS.

FIG. 6 is a diagram showing a process of adhering paint particles to a coated surface and forming a coated film surface during coating.

FIG. 7 is a diagram showing a relationship between paint particles and adhered particles during flight.

FIG. 8 is a characteristic diagram showing the relationship between the average diameter of paint particles and the wavelength of a corrugated waveform.

FIG. 9 is a characteristic diagram showing the relationship between the particle size of the coating material and the coating time.

FIG. 10 is a characteristic diagram showing the relationship between wavelength λ and coating time.

FIG. 11 is a characteristic diagram showing the relationship between the wavelength λ and the wet film thickness h.

FIG. 12 is a block diagram of a second embodiment of the present invention.

FIG. 13 is a block diagram of a third embodiment of the present invention.

FIG. 14 is a block diagram of a fourth embodiment of the present invention.

FIG. 15 is a block diagram of a fifth embodiment of the present invention.

FIG. 16 is a block diagram of a sixth embodiment of the present invention.

FIG. 17 is an example diagram of an image captured by the image capturing unit 2,
FIG. 9A is a diagram showing an image when the coating surface is a flat surface, and FIG. 9B is a diagram showing an image when the coating surface is a curved surface (curved in the x-axis direction).

FIG. 18 is a diagram showing an imaging system 2 and an optical system for a coating surface having a convex curved surface.

FIG. 19 is a characteristic diagram showing the relationship between the curvature r and the correction coefficient K.

FIG. 20 is a characteristic diagram showing curved surface dependence of frequency characteristics of the power spectrum PS.

FIG. 21 is a sectional view of an example of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Body to be coated (body) 7 ... Film thickness calculation part 2 ... Imaging part 8 ... Indicator 3 ... Image processing part 9 ... Coating condition control system 4 ... Wavelength calculation part 10 ... Coating gun 5 ... Wavelength average processing part 19 ... Curved surface calculation unit 6 ... Painting condition input unit 20 ... Curved surface correction calculation unit 100 ... Imaging unit 105 ... Wavelength average processing unit 101 ... Image processing unit 106 ... Dry film thickness calculation unit 102 ... Wavelength calculation unit 107 ... Average film thickness calculation unit 103 ... Film thickness calculation means 108 ... Curved surface calculation means 104 ... Painting condition input means 109 ... Curved surface correction calculation means

Claims (7)

[Claims] 1. An image pickup means for picking up an image of the undried coating surface immediately after applying a paint, an image processing means for image-processing the image information from the image pickup means, and image processing data processed by the image processing means. A wavelength calculating means for calculating the wavelength distribution of the corrugated waveform on the coating surface, and a film thickness calculating means for calculating the coating film thickness based on the wavelength distribution calculated by the wavelength calculating means. A coating film thickness measuring device characterized by. 2. The wavelength calculating means obtains a peak wavelength in a long wavelength region in a power spectrum of a corrugated waveform on a coating surface, and the film thickness calculating means calculates in advance a peak wavelength value in the long wavelength region. The coating film thickness measuring device according to claim 1, wherein the film thickness in a wet state is calculated from the relationship with the coating film thickness obtained by an experiment, and the calculated film thickness value is output. 3. The image pickup means images a plurality of locations on the coating surface, the wavelength calculating means calculates a plurality of wavelength distributions corresponding to the plurality of coating surfaces, and the plurality of wavelength distributions. A wavelength averaging means for averaging, and a coating condition input means for inputting coating conditions including at least the type of paint, and the film thickness calculating means is a wavelength distribution calculated by the wavelength averaging means. The coating film thickness is calculated based on an average value and the coating conditions.
Alternatively, the coating film thickness measuring device according to claim 2. 4. A coating condition input means for inputting a coating condition including at least the non-volatile component information after the coating of the coating material, based on the film thickness in a wet state obtained by the film thickness calculating means and the coating condition. 4. The coating film thickness measuring device according to claim 1, further comprising: a dry film thickness calculating unit that calculates a film thickness in a dry state. 5. The undried coated surface immediately after the coating is applied,
The coating film according to claim 3 or 4, further comprising a plurality of image pickup means for picking up images of different portions of the painted surface, and sequentially processing image information of the plurality of portions picked up by these image pickup means. Thickness measuring device. 6. The undried coated surface immediately after the coating is applied,
Based on the image processing data processed by the image processing means, the image processing means for respectively image processing the image information from the plurality of imaging means, respectively, a plurality of imaging means for imaging different parts of the painted surface, Wavelength calculation means for calculating the wavelength distribution of the uneven waveform of the coating surface at each of the above points, coating condition input means for inputting the coating conditions including at least the type of paint, and a plurality of wavelengths calculated by the wavelength calculation means Based on the distribution and the coating conditions from the coating condition inputting means, the film thickness calculating means for calculating the coating film thickness at each of the above points, and the coating surface based on the calculation result of the film thickness calculating means. A coating film thickness measuring device, comprising: an average film thickness calculating means for calculating the average film thickness of; and parallel processing of image information of a plurality of locations imaged by the plurality of imaging means. 7. A curved surface calculating means for obtaining curved surface information of a painted surface based on at least one of image processing data processed by the image processing means and a wavelength distribution calculated by the wavelength calculating means, and the wavelength calculating means. 7. The curved surface correction calculation means for performing curved surface correction processing according to the result obtained by the curved surface calculation means with respect to the wavelength distribution calculated in step 4. The coating film thickness measuring device described in.