JPH07306017A - Measurement device of thickness of coating film - Google Patents

Abstract

PURPOSE:To accurately measure a thickness of a coated film by eliminating the affection of a curved surface by providing a curved surface-operation means that obtains information of a curved surface of a coated surface based on image processing data. CONSTITUTION:A vehicle body 1 to be coated is coated by moving on a coating line. An imaging section 2 images a coated surface that is not in a dried condition right after the coating. An image processing section 3 executes image processing of toughness information of the imaged coated surface. A roughness--operation section 4 obtains a roughness-information of the coated surface from the image processing data. A curved surface operation section 5 calculates a curvature of the curved surface of the vehicle body 1 from the image processing data. A curved surface correction operation section 6 applies the correction corresponding to the curvature of the coated surface obtained by the curved surface operation section 5 to the roughness and a wavelength of a unevenness wave obtained by the roughness operation section 4. A film thickness calculation section 8 calculates the coated thickness in the wet condition based on the roughness information after the correction and a coating condition inputted from a coating condition input section 7. The value of the thickness is indicated on an indicator 9 and is transmitted to a control system 10 so that the operation of a coating gun is controlled.

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 the coating film thickness in an undried state immediately after applying a coating, and more particularly to a technique for improving the accuracy of film thickness measurement.

[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. 15 is a cross-sectional view showing the principle of an example of a measuring device using magnetism in the above conventional devices. Figure 15
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). Hei 4-306966, unpublished). 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 applicant who solved the problem of the conventional apparatus as described above, it is possible to perform accurate measurement easily in a non-contact manner. There are two problems. (1) In the above-mentioned prior application, the surface roughness and the uneven wavelength are obtained from the optical information (for example, image) of the coated surface. However, when there is a curved surface on the painted surface, such as the car body of an automobile, the captured image is curved according to the curvature, which makes it difficult to accurately measure the surface roughness and the uneven wavelength. An error may occur in the measurement result. (2) When painting one after another in an automated coating line, such as car body painting, the painting is done in a painting booth surrounded by the surroundings so that paint particles do not scatter around. In order to prevent paint particles from being applied to the next car body during painting, wind is blown (up to 2 to 4 m / sec) from the top of the paint booth to drop paint particles onto the floor surface, which is then sprayed with water. It is designed to be removed. On the other hand, in the prior application of the present applicant, the viscosity η of the paint is included in the film thickness calculation formula, and this η changes depending on the elapsed time after coating and the like. In the above-mentioned prior application, the coating viscosity is estimated and calculated according to the elapsed time after coating based on the initial coating viscosity input from the coating condition input means. In addition to the time, the wind speed affects the wind speed.
When a wind of about 4 m / sec is sent, the estimated value of η does not match the actual value, which causes an error in film thickness measurement.

The present invention is a further improvement of the above-mentioned prior application of the present applicant. A first object of the present invention is to provide a coating film which can eliminate the influence of a curved surface and measure the film thickness with high accuracy. It is to provide a thickness measuring device. A second object is to provide a coating film thickness measuring device capable of highly accurately measuring the film thickness by eliminating the influence of wind speed.

[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 the roughness of the undried coating surface immediately after applying the paint, and an image processing means 101 for image-processing the image information from the image pickup means.
And a roughness calculation means 102 for calculating the roughness of the coating surface and the wavelength of the uneven waveform of the coating surface based on the image processing data processed by the image processing means, and the processing by the image processing means. Curved surface calculation means 103 for obtaining curved surface information of the coating surface based on at least one of the image processing data and the calculation result of the roughness calculation means, and the roughness degree and wavelength calculated by the roughness calculation means. On the other hand, the correction processing according to the result obtained by the curved surface calculation means is performed to set the curved surface correction means 104 for correcting at least one of the roughness and the wavelength, and the coating condition including at least the viscosity of the coating material. Film thickness calculation for calculating the film thickness of the coating based on the coating condition input means 105 to be input, the roughness and wavelength after the correction processing by the curved surface correction means, and the coating conditions from the coating condition input means. It includes a stage 106, a. In addition,
Each of the above means corresponds to, for example, the following portions in the embodiment shown in FIG. That is, the image pickup means 100
To the image pickup unit 2, the image processing means 101 to the image processing unit 3,
The roughness calculating means 102 includes a roughness calculating section 4 and a curved surface calculating means 1
Reference numeral 03 corresponds to the curved surface calculation unit 5, curved surface correction unit 104 corresponds to the curved surface correction calculation unit 6, coating condition input unit 105 corresponds to coating condition input unit 7, and film thickness calculation unit 106 corresponds to film thickness calculation unit 8.

Next, the invention described in claim 2 is as follows.
As shown in (b), the following constituent elements are added to the invention described in claim 1. That is, the imaging position control means 107 that outputs a signal for controlling the angle of the image captured by the imaging means 100 based on the result of the curved surface calculation means 103, and the imaging angle of the imaging means 100 according to the signal of the imaging position control means. Imaging position drive means 108 for adjustment
And are added. Each of the above means corresponds to, for example, the following part in the embodiment shown in FIG. That is, the image pickup position control unit 107 corresponds to the image pickup position control unit 12, and the image pickup position drive unit 108 corresponds to the image pickup position drive unit 13.

Next, the invention described in claim 3 is the same as that of claim 1.
Alternatively, in the invention according to claim 2, the curved surface calculation means 1
Reference numeral 03 is configured to calculate the curvature of the coating surface based on the image processing data of the image processing means 101,
The curved surface correction means 104 is configured to correct the value of the uneven wavelength calculated by the roughness calculation means 102 according to the curvature calculated by the curved surface calculation means 103. Next, the invention according to claim 4 is the invention according to claim 1 or 2, wherein the image capturing means 100 is configured to capture an image of a predetermined striped pattern projected on the coating surface. The curved surface calculation means 103 determines, based on the image processing data of the image processing means 101 or the calculation result of the roughness calculation means 102, the peak wavelength of the basic stripe in the power spectrum of the stripe pattern and the long wavelength region of the unevenness of the painted surface. It is configured to calculate the peak wavelength and the curved surface correction means 104.
Is corrected by multiplying the peak wavelength of the basic fringes in a plane stored in advance divided by the peak wavelength of the basic fringes obtained by the curved surface calculation means 103, and the peak wavelength of the long wavelength region. It is configured to calculate the value of the wavelength of the subsequent uneven waveform.

Next, the invention described in claim 5 is the same as claim 2
In the invention described in (1), the curved surface calculation means 103 calculates the respective curvatures in the x-axis direction and the y-axis direction set in the captured image, and the imaging position control means 107 is calculated by the curved surface calculation means 103. When the curvature values in the x-axis direction and the y-axis direction are compared and the curvature in the x-axis direction is equal to or greater than a predetermined value, the imaging in the y-axis direction is performed until the curvature in the x-axis direction becomes equal to or less than the predetermined value. A rotation instruction signal for rotating the image is output, and the image pickup position driving means 108 is configured to rotate the image pickup means 100 according to the rotation instruction signal.

Next, the invention according to claim 6 is shown in FIG.
As described in (c), an image pickup means 100 for picking up the roughness of the undried coating surface immediately after applying the paint, and an image processing means 101 for image-processing the image information from the image pickup means.
And a roughness calculating means 102 for calculating the roughness of the coating surface and the wavelength of the uneven waveform of the coating surface based on the image processing data processed by the image processing means, and the coating including at least the viscosity of the coating material. Environmental condition input means 109 for inputting conditions and environmental conditions in the coating booth including at least wind speed
And a film thickness calculating means 110 for calculating the film thickness of the coating based on the roughness and wavelength obtained by the roughness calculating means and the conditions from the environmental condition inputting means. Each of the above means corresponds to, for example, the following portion in the embodiment shown in FIG. That is, the image pickup unit 100 is the image pickup unit 2, the image processing unit 101 is the image processing unit 3, the roughness calculation unit 102 is the roughness calculation unit 4, the environmental condition input unit 109 is the environmental condition input unit 14, and the film thickness. The calculation means 110 corresponds to the film thickness calculation section 15, respectively.

[0011]

According to the present invention, the curved surface calculating means and the curved surface correcting means are provided, and the roughness information of the coating surface obtained by the roughness calculating means is corrected according to the curved surface of the coating surface. It was done. With this configuration, the film thickness can be accurately measured even if the coated surface is a curved surface. According to a second aspect of the present invention, the image pickup position control means for outputting a signal for controlling the angle of the image picked up by the image pickup means based on the result of the curved surface calculation means, and the image pickup angle of the image pickup means according to the signal. An image pickup position drive means for adjusting is provided, and the image pickup angle is changed when the curvature of the imaged image is too large.
That is, if the curvature is too large, it becomes difficult to ensure the wavelength reading accuracy, so the above-mentioned measures are taken. Specifically, as described in claim 5, the curvature values in the x-axis direction and the y-axis direction set in the captured image are compared, and when the curvature in the x-axis direction is equal to or greater than a predetermined value, , The imaging means is rotated so as to rotate the captured image in the y-axis direction until the curvature in the x-axis direction becomes equal to or less than a predetermined value. With this configuration, the wavelength reading accuracy can be secured even when the curvature in a certain direction is very large.

Further, claims 3 and 4 show specific configurations of the curved surface calculation means and the curved surface correction means in the invention according to claim 1 or 2. First,
In claim 3, the curvature of the coated surface is obtained to correct the value of the uneven wavelength, and in claim 4, the peak wavelength of the basic stripe in the power spectrum of the striped pattern and the long wavelength region of the uneven surface of the coated surface. The peak wavelength is used to calculate the value of the uneven wavelength in the plane. Further, the invention according to claim 6 is configured such that the influence of wind is included in the calculation of the coating viscosity η of the paint used for the film thickness calculation. With this configuration, it is possible to eliminate the influence of the ventilation air in the coating booth and to accurately measure the film thickness in the actual coating process.

[0013]

FIG. 2 is a first embodiment of the present invention and is a block diagram when the present invention is applied to a vehicle body painting line. First, the outline of the entire configuration will be described with reference to FIG. Reference numeral 1 denotes a vehicle body of a body to be coated, which is coated while moving on a coating line at a predetermined speed. Reference numeral 2 denotes an image pickup unit for picking up an image of the undried (wet) coated 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 adjusts to the moving speed of the coating line,
For example, it is installed at a position where the vehicle body can reach after 1 to 2 minutes. The roughness information of the painted surface (details will be described later) captured by the image capturing unit 2 is subjected to image processing by the image processing unit 3. The image processing unit 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 roughness calculation unit 4. In roughness arithmetic unit 4, the roughness information painted surface from the input image processing data, that is, the roughness of R _a (specifically corresponding to the average surface value of the unevenness of the peak-to-peak of the painted surface, below And the wavelength λ of the concavo-convex waveform (specifically, the long wavelength λ described later is used). In addition, the curved surface calculation unit 5 calculates the curvature of the coating surface of the object 1 to be coated from the image processing data processed by the image processing unit 3 (details will be described later). The curved surface correction calculation unit 6 gives a correction according to the curvature of the coated surface calculated by the curved surface calculation unit 5 to the roughness _Ra and the wavelength λ of the uneven waveform calculated by the roughness calculation unit 4 (details will be described later). ). In general, the correction may be made only for the wavelength λ of the uneven waveform. Further, in the curved surface calculation unit 5 and the curved surface correction calculation unit 6, in addition to the above-described curvature calculation and the correction method of the wavelength λ corresponding thereto, there is also a method of performing correction from the peak wavelength of the power spectrum (details will be described later).

The coating condition input unit 7 is, for example, an input means such as a keyboard, and inputs the component information of the coating such as the type of the coating and the content of the volatile component, the coating conditions such as the viscosity of the coating and the temperature. In addition, the film thickness calculation unit 8 includes the curved surface correction calculation unit 6
Roughness information after correction supplied from (R _a, lambda) calculates a time variation [Delta] R _a roughness degree R _a from and to the coating conditions from the [Delta] R _a and the wavelength lambda and the coating condition input unit 8 Based on this, the wet coating thickness is calculated. The film thickness calculator 8
The value of the film thickness obtained in step 1 is displayed on a display 9 such as a liquid crystal display device or a CRT display device and presented to a worker, and is also sent to a coating condition control system 10 so that the operating conditions of the coating gun 11 are optimized. Control to keep on. The roughness calculation unit 4, the curved surface calculation unit 5, the curved surface correction calculation unit 6, and the film thickness calculation unit 8 are configured by a calculation device such as a computer.

Next, the operation will be described. First, the principle of film thickness measurement in the present invention will be described. The film thickness measuring method in the present invention measures the coating film thickness by paying attention to the smoothing phenomenon of the coating surface in an undried state immediately after coating the coating material, that is, in a wet state. FIG. 3 is a sectional view of the coating film after coating. Immediately after coating, as shown in (a), the coated surface is in an uneven state due to the initial bonding of the adhered particles. Then, with the lapse of time, as shown in (b), it is gradually smoothed by the leveling force, and finally becomes a smoothed state as shown in (c). In the present invention, paying attention to such a smoothing phenomenon, the uneven state of the coating surface in a wet state is measured, and thereby the coating film thickness after smoothing or after drying is calculated. In order to measure the uneven state in the wet state as described above, various methods such as an optical interference type surface roughness meter (for example, “Mechanical Engineering Flight Section, Japan Society of Mechanical Engineers, September 30, 1989”) are used.
3rd edition of new edition, B2, pp. 207-208 ")
However, here, a method will be described in which the coating surface is imaged by an image pickup means (for example, a CCD camera) and the information is image-processed.

FIG. 4 is a sectional view showing an example of the image pickup section 2. As shown in FIG. 4, the basic configuration of the imaging unit is the light source 3
1, bright and dark pattern plate 32, reflecting mirror 33, lens 34, CC
It consists of a D camera 35. The bright / dark pattern plate 32 is an opaque plate (or a transparent plate on which opaque stripe patterns are printed at predetermined intervals) provided with linear slits at predetermined intervals (for example, 1 mm intervals). And light source 3
The parallel light beam from the light source 1 is reflected by the bright / dark pattern plate 32 and the reflecting mirror 33.
By irradiating the coated surface obliquely through the lens 34 and the lens 34, a striped pattern corresponding to the slit is formed on the coated object. This striped pattern has a distorted waveform according to the irregularities on the object to be coated. The reflected light is imaged by the CCD camera 35, and the distorted striped pattern, that is, the information of the surface roughness is input. Image information of the striped pattern as described above is subjected to image processing, and power spectrum frequency analysis (for example, fast Fourier transform processing: FFT) is performed to obtain the power spectrum PS.

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.
Then, the integrated value (area of the shaded area) of the second peak waveform is obtained as a value for displaying the surface roughness, and this is taken as the power spectrum integrated value P. The wavelength λ (peak wavelength in the long wavelength region) and the power spectrum integral value P are related to the film thickness as follows, and based on these values, the film thickness can be calculated by using the following smoothing theoretical formula. It can be calculated.

[0018] First, explaining the smoothing characteristics of the power spectrum integral value P, and the surface of the uneven surface mean corresponding surface roughness value R _a and the power spectrum integral value P (peak-to-peak value), There is a relationship as shown in FIG. 6, and there is a relationship as shown in the following (Formula 1) and (Formula 2). P = Q + k × √R _a (Equation 1) _Ra = {(P−Q) / k} ² (Equation 2) However, in the above equation, Q is a roughness correction value and k is a roughness conversion coefficient. is there. In the derivation of the smoothing theoretical formula based on the power spectrum analysis value, first, the surface roughness R _a is represented by the following (Formula 3) as a wet coating smoothing theoretical formula (approximate formula). R _a = R _a0 · exp (−t / τ) ( _Equation 3) where R _a0 is the initial value of R _a (time point 0, that is, the value immediately after coating), and t is the elapsed time after coating. Further, τ is a time constant derived from the basic formula of the viscous fluid, and is as shown in the following formula (Equation 8). By substituting the equation (2) into the equation (3), the following equation (4) is obtained. {(P−Q) / k} ² = {(P ₀ −Q ₀ ) / k} ² exp (−t / τ) (Equation 4) where P ₀ is the initial value of P (value at time 0) And Q ₀ is the initial value of Q. In the above formula (4), if P and P ₀ are values including the respective correction values Q and Q _0, and expressed as (P ₀ −Q ₀ ) → P ₀ , (P−Q) → P,
The equation (4) can be expressed as the following equation (5). P = P ₀ · exp (−t / 2τ) (Equation 5) The time constant τ is expressed by the following (Equation 6). τ = 3ηλ ⁴ / 16π ⁴ γh ³ (Equation 6) where η is the viscosity of the paint, λ is the peak wavelength of the long wavelength region, γ is the surface tension of the coating film, and h is the film thickness in the wet state (imaging The average value of the part). From the above, the coating film thickness h by the power spectrum analysis value becomes as shown by the following (Formula 7).

[0019]

[Equation 7]

However, P ₁ is the value of the power spectrum integral value P at the time point t ₁ , and P ₂ is the time point t ₂ (where ₋₁ <t ₂ ).
Is the value of P in. Note that τ ′ _i is expressed by the following (Equation 8). τ ′ _i = 3 η (t _i ) · λ ⁴ / 16π ⁴ γ (Equation 8) where i = 1, 2 and η (t _i ) is a function of the viscosity of the paint and the elapsed time after painting. Indicates that. That is, what is input from the coating condition input means 7 is the viscosity η of the coating material before coating, but the coating viscosity after coating is a value η (t _i ) that changes according to the elapsed time after coating. . This value is
It is a value determined by the paint composition (such as the proportion of volatile components in the paint) and the wind speed. As can be seen from the above equation (7),
From the viscosity η of the coating material, the surface tension γ of the coating film, the peak wavelength λ of the long wavelength region of the uneven waveform, and the power spectrum integral value P at _two time points t ₁ and t ₂ after coating, the film thickness h in the wet state Can be asked. Of the above numerical values, the viscosity η of the paint and the surface tension γ of the coating film are values that are determined by the characteristics of the paint, so enter the values that are known in advance, and enter the peak wavelength λ in the long wavelength region and the power spectrum integration. As the value P, a value obtained by processing the image information is used.

FIG. 7 is a characteristic diagram showing a wet smoothing dynamic characteristic (power spectrum integral value P) obtained by comparing a smoothed theoretical value and a measured value using the equation (7). In FIG. 7, the horizontal axis is the elapsed time after coating, and the vertical axis is the power spectrum integral value P. In the above measurement, an image immediately after coating is taken by the imaging unit 2 and power spectrum analysis is performed. From FIG. 7, it can be seen that the measured value has a smoothing characteristic that is substantially in agreement with the theoretical value. Table 1 shows that the film thickness is 6
9 is a table showing the results of measuring the film thickness h using the estimation formula of (Equation 7) for two samples of 0 μm and 54 μm. As shown in Table 1, it can be seen that measurement can be performed with an accuracy of several μm.

[0022]

[Table 1]

In the embodiment shown in FIG. 2, the image pickup section 2, the image processing section 3, the roughness calculating section 4, and the film thickness calculating section 8 perform the above-described processing to obtain the film thickness h at the image pickup point.

Further, in the equation (7), two values P ₁ and P ₂ at _two time points t ₁ and t ₂ after coating are used to calculate using the time variation of roughness information. There is. Therefore, it is necessary to image the same place at two points after painting. For this purpose, it is necessary to move the image pickup unit 2 in accordance with the movement of the vehicle body on the coating line, which complicates the apparatus. To avoid this, there are the following methods. That is, a test piece is prepared in addition to the vehicle body that is the object to be coated, and coating is performed under the same conditions as the object to be coated, and the value P at time t ₁ (for example, t ₁ = 10 seconds, t ₁ <t ₂ ).
₁ uses the value obtained by processing the image information of the test piece. In this way, the image pickup unit 2 is set to the time point t.
_{In 2} (for example, 1 to 2 minutes after coating), the image capturing may be performed only once. In the present embodiment, basic measurement is performed by imaging and image processing of the painted surface, and calculation is performed using the power spectrum integral value P and the peak wavelength λ of the long wavelength region as information on the roughness of the painted surface. The case where it does is illustrated. However, as the coating surface roughness information, for example,
Prior application of the applicant (Japanese Patent Application No. 4-306966)
As described in, using an optical interferometric surface roughness meter, a method of calculating based on the peak-to-peak of unevenness and the wavelength λ of unevenness, or from the measurement result of the optical interference type surface roughness meter of the surface There is a method of calculating using the average roughness R _a and the average wavelength λ _{a of the} unevenness, and any method may be used.

Further, the measurement up to now is to calculate the film thickness in the wet state, but the film thickness in the wet state and the dry film thickness after drying are constant depending on the volatile components in the paint. There is a correlation. Therefore, the dry film thickness can be easily estimated by multiplying the measured wet film thickness by a coefficient determined according to the content of the coating material.

Next, the curved surface correction in the present invention will be described. 8A and 8B are examples of images captured by the image capturing unit 2. FIG. 8A illustrates an image when the coating surface is a flat surface, and FIG. 8B illustrates an image when the coating 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 direction becomes an elliptical shape. In FIG. 8, the intermittent direction of the striped pattern is the x-axis, and the direction orthogonal thereto is the y-axis.

The curvature calculation unit 5 uses the image data as described above to derive the curvature r of the coating surface according to the following procedure. First, as shown in FIG. 8B, the maximum lengths (bright area) x and y in the x-axis and y-axis directions of the 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 of the 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 (Formula 9). The y direction can be calculated in the same manner.

[0028]

[Equation 9]

Here, x: measured maximum x-axis length x ₀ : maximum x-axis 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, a correction coefficient K for the wavelength λ by the curvature r is obtained from the relationship between the curvature r and the correction coefficient K shown in FIG. Note that FIG. 10 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. That is, when the measured wavelength at the curved surface is λ, the actual wavelength λ'corresponding to the corrected plane is λ '.
Is expressed by the following equation (10).

[0030]

[Equation 10]

However, a: constant R = 1 / r If the film thickness is calculated as described above using the actual wavelength λ ′ calculated as described above, the film thickness can be accurately measured even on a curved surface. I can. In the embodiment of FIG. 2,
The curved surface calculation unit 5 performs the calculation to obtain the correction coefficient K, and the curved surface correction calculation unit 6 performs the calculation to obtain the actual wavelength λ ′. In the film thickness calculation unit 8, the curved surface correction calculation unit 6
The coating film thickness h in the wet state is calculated based on the power spectrum integral value P given from the above, the corrected actual wavelength λ ′, and the coating condition from the coating condition input unit 8.

In addition to the wet film thickness h on the display 9,
The power spectrum integral value P, the wavelength λ, the corrected actual wavelength λ ′, the curvature r of the coating film surface, and the like may be displayed. In the above description, the curvature r is obtained and corrected only in the x-axis direction. This is because the intermittent direction of the striped pattern is set as the x-axis as shown in FIG. 8, 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. Further, in the above description, the curved surface correction is performed only for the wavelength λ, but the power spectrum integral value P can be similarly corrected. That is, similar to the relationship between the curvature r with respect to the wavelength λ and the correction coefficient K shown in FIG. 10, the relationship between the curvature r and the correction coefficient K ′ with respect to the power spectrum integral value P is previously obtained by an experiment, Based on the relationship, the correction coefficient K ′ is calculated from the calculated curvature r,
Multiply it by the measured power spectrum integral value P,
The corrected actual power spectrum integral value P ′ may be obtained.

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 ′ of the long wavelength region are It turns out that there is a certain relationship regardless of the curvature. FIG. 11 shows the power spectrum PS
It is a characteristic view which shows the curved surface dependence of the frequency characteristic of. Figure 11
In, the vertical axis shows the power spectrum PS, the horizontal axis shows the frequency f (1 / λ), the solid line (A) shows the characteristics of the coated surface being flat, and the dotted line (B) shows the characteristics of the coating surface having the curvature r ₁ . The broken line (C) shows the characteristic when the coated surface has a curvature r ₂ (r ₁ <r ₂ ).

As can be seen from FIG. 11, the peak frequency increases (the peak wavelength λ decreases) as the curvature increases, but it has been found that the relationship of the following (Equation 11) holds regardless of the curvature.

[0035]

[Equation 11]

However, f ₀ : basic fringe peak frequency on a plane f ₀ ′: long wavelength peak frequency on a plane _fr : basic fringe peak frequency on a curvature r f _r ′: long wavelength peak frequency on a curvature r From equation (11), the long wavelength peak frequency f in the plane
₀ 'is determined by the following equation (12) below.

[0037]

[Equation 12]

In the equation (12), 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. When the wavelength λ is used as described in the film thickness calculation, the correction may be performed according to the following (Equation 13).

[0039]

[Equation 13]

Where λ ₀ : basic fringe peak wavelength in plane λ ₀ ': long wavelength peak wavelength in plane λ _r : basic fringe peak wavelength in curvature r λ _r ': long wavelength peak wavelength in 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 shown in FIG. 2, the curved surface calculation unit 5 calculates λ _r and λ _r ′ from the image processing data of the image processing unit 3, and the curved surface correction calculation unit 6 the calculation from the values of lambda ₀ which has been previously stored their values determine the lambda ₀ 'may be configured to perform. As the value of λ _r ′, the value calculated by the roughness calculator 4 can be used.

Next, FIG. 12 is a block diagram of a second embodiment of the present invention. In FIG. 12, 12 is an image pickup position control unit, 13 is an image pickup position drive unit, and the others are the same as in FIG. In the embodiment of FIG. 2, the value of the wavelength λ is corrected according to the curvature of the coated surface,
If the curvature is too large, it becomes difficult to secure the wavelength reading accuracy. In this embodiment, the countermeasure is taken.

In FIG. 12, the image pickup position control unit 12 is
The curvature values in the x-axis direction and the y-axis direction calculated by the curved surface calculation unit 5 are compared, and when the curvature in the x-axis direction is extremely large (equal to or more than a predetermined value), the curvature in the x-axis direction is a predetermined value. A rotation instruction signal for rotating the captured image in the y-axis direction is output until the following. Then, the image pickup position drive unit 13 rotates the image pickup unit 2 in accordance with the rotation instruction signal to rotate the picked-up image. When the curvature in the x-axis direction becomes equal to or less than the predetermined value in this way, the curvature data of the x-axis is sent to the curved surface correction calculation unit 6 and the value is corrected as described above. as mentioned above,
When the curvature in a certain axial direction is very large, the wavelength reading accuracy can be secured by rotating the captured image in the axial direction having a small curvature. The image pickup position drive unit 13 is, for example, a servomotor or the like, and rotates the image pickup unit 2 in the z-axis ← → y-axis direction while facing the coated surface.

Next, FIG. 13 is a block diagram of the third embodiment of the present invention. In FIG. 13, the environmental condition input unit 1
Reference numeral 4 is used to input paint component information such as paint type and volatile content, paint conditions such as paint viscosity and temperature, and environmental conditions inside the paint booth, such as wind speed. In addition, the film thickness calculation unit 1
Reference numeral 5 calculates the coating film thickness based on the roughness degree and wavelength obtained by the roughness calculation unit 4 and the condition from the environmental condition input unit 14.

The wind speed information input from the environmental condition input unit 14 will be described in detail below. As shown in the equation (8), the viscosity η (t _i ) of the paint is a function of time and is represented by the following equation (14). η (t _i ) = (η ₀ + k ₁ T) + (η ₁ + k ₂ T) t + k ₃ t ² (Equation 14) where η ₀ , η ₁ : initial viscosity coefficient T: coating temperature k ₁ , k ₂ : temperature correction coefficient k _3: t ² correction coefficient the equation (14) is a formula that ignores the effects of the wind in the painting booth, the coating viscosity eta (t _i) 'is the following, including the effects of wind It is shown by the equation (15). η (t _i ) '= (η ₀ + k ₁ T) + (η ₁ + k ₂ T) t + (eH + k ₃ ) t ² (Equation 15) where H: wind speed in coating booth (m / sec) e: wind Correction factor Generally, the ventilation wind speed in the coating booth is about 2 to 4 m / sec.

FIG. 14 is a characteristic diagram of coating viscosity.
(A) shows the characteristics of the windless state in the laboratory (Equation 14).
The characteristic obtained by the equation, (B) is the characteristic obtained when the wind speed H = 3.5 m / sec in the equation (15).
In this way, by calculating the coating viscosity η including the effect of the ventilation wind in the coating booth, the coating film thickness can be accurately measured even in the actual coating line. It is of course possible to combine the embodiment shown in FIG. 13 with the embodiment shown in FIG. 2 or 12 to perform both curved surface correction and wind speed correction.

[0046]

As described above, according to the present invention,
Since the surface roughness and wavelength values used for film thickness calculation are corrected according to the curved surface of the painted surface, the film thickness can be accurately measured even if the painted surface is curved. The effect that it becomes possible is obtained. In addition, since the influence of wind is included in the calculation of the coating viscosity η of the paint used for calculating the film thickness, the effect of ventilation wind in the coating booth is eliminated, and the film is accurately applied in the actual coating process. The effect is that the thickness can be measured.

[Brief description of drawings]

FIG. 1 is a functional block diagram of the present invention.

FIG. 2 is a block diagram of the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a state of a coating film after coating.

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 surface roughness R corresponding to an average value of surface irregularities.
_The characteristic view which shows the relationship of _a and power spectrum integral value P.

FIG. 7 is a characteristic diagram showing wet smoothing dynamic characteristics obtained by comparing a smoothed theoretical value using Equation (7) and a measured value.

FIG. 8 is an example diagram of an image captured by the image capturing unit 2,
FIG. 6A is a diagram showing an image when the coated surface is a flat surface, and FIG.

FIG. 9 is a diagram showing an imaging system 2 and an optical system of a coating surface having a convex curved surface.

FIG. 10 is a characteristic diagram showing a relationship between a curvature r and a correction coefficient K.

FIG. 11 is a characteristic diagram showing the curved surface dependence of the frequency characteristic of the power spectrum PS.

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 characteristic diagram of coating viscosity.

FIG. 15 is a cross-sectional view of an example of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Body to be coated (body) 8 ... Film thickness calculation part 2 ... Imaging part 9 ... Indicator 3 ... Image processing part 10 ... Coating condition control system 4 ... Roughness calculation part 11 ... Coating gun 5 ... Curved surface calculation part 12 ... Imaging position control unit 6 ... Curved surface correction unit 13 ... Imaging position driving unit 7 ... Painting condition input unit 14 ... Environmental condition input unit 15 ... Film thickness calculation unit 100 ... Imaging unit 106 ... Film thickness calculation unit 101 ... Image processing unit 107 ... Imaging position control means 102 ... Roughness calculation means 108 ... Imaging position drive means 103 ... Curved surface calculation means 109 ... Environmental condition input means 104 ... Curved surface correction means 110 ... Film thickness calculation means 105 ... Painting condition input means

Claims (6)

[Claims] 1. An image pickup means for picking up the roughness of the undried coating surface immediately after applying the paint, an image processing means for image-processing the image information from the image pickup means, and an image processed by the image processing means. Roughness calculating means for calculating the roughness of the coating surface and the wavelength of the uneven waveform of the coating surface based on the processing data, image processing data processed by the image processing means, and calculation of the roughness calculating means Based on at least one of the results, the curved surface calculating means for obtaining the curved surface information of the coating surface, and the roughness degree and the wavelength calculated by the roughness calculating means,
Curved surface correction means for performing a correction process according to the result obtained by the curved surface calculation means to correct at least one of the roughness and the wavelength, and a coating condition input for inputting coating conditions including at least the viscosity of the coating material. Means, and a film thickness calculating means for calculating the film thickness of the coating based on the roughness and wavelength after the correction processing by the curved surface correcting means and the coating condition from the coating condition inputting means. A coating film thickness measuring device characterized by. 2. An image pickup means for picking up the roughness of the undried coating surface immediately after applying the paint, an image processing means for image-processing the image information from the image pickup means, and an image processed by the image processing means. Roughness calculating means for calculating the roughness of the coating surface and the wavelength of the uneven waveform of the coating surface based on the processing data, image processing data processed by the image processing means, and calculation of the roughness calculating means Based on at least one of the results, the curved surface calculating means for obtaining the curved surface information of the coating surface, and the roughness degree and the wavelength calculated by the roughness calculating means,
Curved surface correction means for performing correction processing according to the result obtained by the curved surface calculation means to correct at least one of the roughness and wavelength, and imaging by the imaging means based on the result of the curved surface calculation means. Image pickup position control means for outputting a signal for controlling the image angle, image pickup position drive means for adjusting the image pickup angle of the image pickup means according to the signal of the image pickup position control means, and coating conditions including at least the viscosity of the paint. Coating condition input means for inputting, a roughness and wavelength after correction processing by the curved surface correcting means, and a film thickness calculating means for calculating a coating film thickness based on the coating conditions from the coating condition input means. A coating film thickness measuring device comprising: 3. The curved surface calculating means calculates the curvature of the painted surface based on the image processing data of the image processing means, and the curved surface correcting means responds to the curvature calculated by the curved surface calculating means. The coating film thickness measuring device according to claim 1 or 2, wherein the value of the uneven wavelength obtained by the roughness calculating means is corrected. 4. The image pick-up means picks up an image of a predetermined striped pattern projected on a painted surface, and the curved surface calculation means outputs image processing data of the image processing means or a calculation result of the roughness calculation means. On the basis of the above, the peak wavelength of the basic stripe in the power spectrum of the striped pattern and the peak wavelength of the long wavelength region of the unevenness of the coating surface are calculated, and the curved surface correction means is a flat surface stored in advance. The value obtained by dividing the peak wavelength of the basic fringes at the value obtained by dividing the peak wavelength of the basic fringes obtained by the curved surface calculating means by the peak wavelength of the long wavelength region, to obtain the wavelength value of the uneven waveform after correction. The coating film thickness measuring device according to claim 1 or 2, which is calculated. 5. The curved surface calculating means calculates the respective curvatures in the x-axis direction and the y-axis direction set in the imaged image, and the imaging position control means is calculated by the curved surface calculating means. If the curvature values in the x-axis direction and the y-axis direction are compared and the curvature in the x-axis direction is equal to or larger than a predetermined value, a captured image in the y-axis direction until the curvature in the x-axis direction becomes equal to or smaller than the predetermined value. 3. A rotation instruction signal for rotating the image pickup device is output, and the image pickup position driving means rotates the image pickup means according to the rotation instruction signal. Coating film thickness measuring device. 6. An image pickup means for picking up the roughness of the undried coating surface immediately after applying the coating material, an image processing means for image-processing the image information from the image pickup means, and an image processed by the image processing means. Roughness calculation means for calculating the roughness of the coating surface and the wavelength of the uneven waveform of the coating surface based on the processing data, the coating conditions including at least the viscosity of the coating, and the environment in the coating booth including at least the wind speed. Environmental condition input means for inputting conditions, a roughness degree and a wavelength obtained by the roughness calculation means, and a film thickness calculation means for calculating a coating film thickness based on the conditions from the environmental condition input means. And a coating film thickness measuring device.