JP2797819B2 - Painted surface inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint surface property inspection apparatus for easily measuring the condition of a paint surface of an automobile, for example.

[0002]

2. Description of the Related Art Conventionally, in the production process of automobiles, the condition of painted surfaces has been strictly inspected. For example, as an example of inspection of the painted surface, there is an inspection of sharpness. This sharpness inspection is a test for examining how much the coating surface is flattened, and is conventionally performed by the following method.

First, as an example of a conventional technique, a stripe image having a contrast different from that of a painted surface is projected on the painted surface, and a reflected image from the painted surface is converted into a C image.
An example in which an image is captured by a CD camera and the glossiness is measured based on the captured image can be exemplified. An example of an image obtained by this method is shown in FIG. As shown in the figure, the contrast of the boundary between the painted surface and the stripe is clear for those with good gloss on the painted surface, but not so for those with poor gloss. I'm sick. Image processing is performed on these images to graph the relationship between the luminance and the position, resulting in a graph as shown below the stripe image. The glossiness of the painted surface is calculated based on this graph as follows. As shown in the figure, the brightness value of the dark part at a position sufficiently distant from the bright part in the input image is Z0i,
Let Z1i be the luminance value at the center of the valley between the light and dark areas, and Z1i
The difference from Z0i is calculated for each line, and the value of this sum is used as the glossiness evaluation value. Therefore, the larger the evaluation value, the worse the glossiness.

[0004]

However, in such a conventional inspection method, as described above, the luminance value of the dark portion at a position sufficiently distant from the bright portion and the center of the valley between the bright portion and the dark portion as described above. Since the glossiness is determined based on the luminance value, the measurement result is easily affected by factors such as relatively large irregularities on the painted surface and the spacing between stripes projected on the painted surface, and the measurement reliability is not improved. There was a need for improvement.

For example, if a very fine stripe is projected on a painted surface having a low glossiness, the irregular reflection of light due to the fine unevenness of the painted surface causes the center of the valley between the light and dark portions to be affected. The luminance value does not decrease much. For this reason, a result worse than the actual glossiness is obtained. Conversely, when a rough stripe is projected, the luminance value of the valley almost matches the luminance value of the dark part. This results in better results than the actual glossiness. Therefore, in order to perform accurate measurement, it can be said that it is necessary to project a stripe having a roughness suitable for the glossiness of the painted surface to be measured.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a paint surface property inspection apparatus which has good measurement reliability and can perform quick measurement. .

[0007]

In order to achieve the above object, the present invention projects an image to be inspected having a different contrast from the painted surface on the painted surface, and based on the image to be inspected reflected from the painted surface. In a painted surface property inspection device for inspecting the properties of the painted surface, input means for inputting the image to be inspected from the painted surface, and the painted surface based on the inspected image input to the input means, Density gradient calculating means for calculating the density gradient at the boundary with the image to be inspected, and evaluation calculating means for calculating and evaluating the glossiness of the painted surface based on the density gradient calculated by the density gradient calculating means. It is characterized by having.

[0008]

The present invention thus constructed operates as follows. The input means inputs the image to be inspected reflected from the painted surface, and the density gradient at the boundary between the painted surface and the image to be inspected in the input image is calculated by the density gradient calculating means. Then, based on the calculated density gradient, the evaluation calculating means obtains the glossiness of the painted surface. Therefore, the glossiness can be measured without being significantly affected by the shape of the image to be inspected projected on the painted surface or the unevenness of the painted surface.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a structural view of a measuring head constituting a painted surface property inspecting apparatus according to the present invention. FIG. 1 (A) is a front view mainly showing an internal structure thereof, and FIG. 1 (B) is a bottom view thereof.

The measuring head 25 constituting the coating surface property measuring apparatus is a small and light handy type measuring head, and has a casing 11 having an opening 12 which serves as a light entrance and exit. In the casing 11, a light source 2, a half-diffusion plate 3, a stripe grating 4, a mirror 10, and a convex lens 5 are provided on a light projecting side, and a light receiving lens 7, a diaphragm 8, and a CCD element constituting a CCD camera 6 are provided on a light receiving side. 9 are arranged and stored in order based on the optical axis. The light source 2 includes a halogen bulb 2a and a reflecting mirror 2b, and the stripe grating 4 is made of, for example, a glass plate on which a stripe pattern is printed. Thus, the painted surface 1 is irradiated with the stripe pattern from the light emitting side, and the reflected light is reflected on the CC on the light receiving side.
The image is taken by the D camera 6. The reflection stripe pattern imaged by the CCD camera 6 is displayed on the screen of the built-in monitor 13 and output to the image processing device 30 for digitizing and recording sharpness via the external connector 14. . On the other hand, the opening 12 of the casing 11 is sealed with a transparent glass 15 as a transparent plate, and four free feet 16 whose ends are freely adjustable and whose tip can freely rotate are attached to the bottom surface of the casing 11.

Measuring head 2 having a structure as outlined above
The details of each of the components 5 will be described below in order. First, the optical system of the measuring head 25 will be described. The stop 8 is a pinhole stop having a diameter of about 0.2 to 0.3 mm that is stopped down to the diffraction limit of light, and is arranged between the light receiving lens 7 and the CCD element 9 in the same CCD camera 6. This very small aperture 8 blocks all undesired light beams that cause blurring of the image, so that the image can be clearly captured anywhere before and after the focused object plane, and The depth increases dramatically.
Then, by the dramatic increase in the depth of field due to the aperture 8, the object is brought into focus no matter where it is, and the stripe grating 4 can be moved without moving the light receiving lens 7 or changing its focal length. It becomes possible to focus on both the painted surfaces 1. As a result, three textures (smoothness, solid feeling, glossiness) of sharpness corresponding to the magnitude of the undulation of the painted surface 1 as described later can be simultaneously and accurately measured. In addition, since the depth of field is significantly increased by the aperture 8, the sensitivity can be further improved and the sensitivity can be adjusted, and non-contact measurement can be performed by moving the measuring head 25 away from the painted surface 1. . If the diameter of the pinhole 8 is reduced below the diffraction limit of light, the resolution is lowered due to the diffraction phenomenon, which is not preferable.

Next, the light emitting side optical system will be described. The convex lens 5 included in this optical system is for arranging the stripe grating 4 as far as possible in a pseudo manner in order to increase the sensitivity. By inserting the convex lens 5, the stripe grating 4 is located at infinity. This makes it possible to reduce the size of the device 25 while increasing the sensitivity. Further, as described above, the aperture 8
Since the depth of field is so large that the lens can be focused anywhere, the stripe grating 4 can be placed at any appropriate position in relation to the convex lens 5. Although not visible, the striped grid 4 can be pseudo-separated from the painted surface 1 to infinity or more. This further improves the sensitivity. Further, in the present embodiment, the mirror 10 is provided to increase the optical path, thereby further reducing the size of the apparatus.

The light source 2 includes a halogen bulb 2a and a reflecting mirror 2
The light source is disposed a little farther than the focal point b, and forms a condensing light source that spreads after light is once condensed. This is because, since the painted surface 1 is usually a curved surface, the edge of the illuminated surface tends to be darker than the center in a conventional spot-type light source that emits parallel rays. This is to secure more stable brightness on the curved surface. The light distribution angle of this condensing light source 2 is, for example, 40 ° or more,
It is larger than that of the spot type (light distribution angle 0 to 10 °).

The semi-diffusion plate 3 for eliminating light unevenness includes:
Unlike the diffusion plate used conventionally, it diffuses and transmits incident light within a small scattering angle range. For example, frosted glass or focus glass is used. This semi-diffusion plate 3 is
Is arranged before the light condensing point C of Comparing the light transmittance on the optical axis of the diffuser plate and the semi-diffuse plate,
5% and about 85% for the semi-diffusion plate (both are actually measured values). As described above, unlike the diffusion plate, the semi-diffusion plate has a function of causing light to travel straight to a certain extent, so that the decrease in the amount of light applied to the stripe grating 4 in the optical axis direction can be relatively small. Therefore, by using the semi-diffusion plate 3, it is possible to secure the brightness required for measurement with the light source 2 having a smaller capacity than the conventional one. In addition, as shown in the figure, three half-diffusion plates 3 are used to sufficiently eliminate unevenness. By using an appropriate number of the semi-diffusion plates 3 in this way, it is possible to irradiate the stripe grating 4 with light having no unevenness while securing the light quantity.

Next, the structure of the measuring head 25 will be described. First, the transparent glass 15 is attached to the opening 12 of the casing 11 as a light entrance and exit, and the measuring head 25 itself has a closed structure. This prevents dust or the like from entering the inside of the measuring head 25, contaminating the optical system and causing a decrease in the performance of the apparatus. At this time, since the measuring head 25 is supported by the free foot 16 at a position distant from the painted surface 1, the reflected light from the glass surface does not enter the CCD camera 6 as shown in FIG. Therefore, measurement is possible even if the opening 12 is closed with the transparent glass 15. In addition, in the case of an apparatus of a type in which the measurement is performed by directly contacting the painted surface 1, although not shown, if the glass is arranged in an inverted V-shape so that the glass surface is perpendicular to the optical axis, the glass is sealed.
Since there is no reflection on the glass surface which is not desirable for imaging,
It can be measured even when sealed with glass.

On the bottom surface of the measuring head 25, four free feet 16 are mounted. An example of the free foot 16 is shown in FIG. The free foot 16 has a swivel-type tip of the ball joint 17 at the tip of the ball joint 17, and has a leg with a built-in spring 18 that can be extended and contracted. A felt 19 is attached to the distal end portion 17 so as not to damage the painted surface 1 during measurement. As described above, since the free foot 16 is a swivel type in which the toes can freely rotate and the legs are adjustable, the direction of the toes and the length of the legs can be adjusted regardless of the curved surface of the painted surface 1. By appropriate adjustment, the reflected light from the painted surface 1 can always be captured by the CCD camera 6. Note that the foot 16
Is provided, the head 25 can be separated from the painted surface 1 during measurement. However, as described above, the stop 8 in the CCD camera 6 is very small, about the diffraction limit, so that disturbance light from the opening 12 is reduced by the stop 8. It is almost blocked and the influence of disturbance light is eliminated, so that the measurement head 25 can be measured away from the painted surface 1.

Further, in this embodiment, a timer circuit is incorporated in the operation switch mounting board 20, and if the operation switch is not operated for a certain period of time, the light source 2 and the CCD are automatically turned on.
The power supply to the internal devices such as the camera 6 and the monitor 13 is cut off, and the power is turned on as soon as the operation switch is operated. The image input by the CCD camera 6 of the measuring head 25 configured as described above is processed by the above-described image processing device 30 as follows. Hereinafter, the processing here will be described with reference to FIG. 3 based on the flowchart shown in FIG.

First, the multi-valued image input from the CCD camera 6 is input to an image processing device 30 and the device 30
It is stored in a memory provided inside. An example of the stored image is as shown in FIG. That is, an image corresponding to the reflected light of the stripe reflected on the painted surface is input. Next, the brightness values Zma of the maximum bright portion and the maximum dark portion on an arbitrary Y axis of this image.
Find xi and Zmini respectively. In performing this process, a graph as shown in FIG. 3B is generated from the input image. Then, a value representing the maximum luminance and a value representing the minimum luminance of this graph are obtained, and these values are expressed as Zma.
xi and Zmini (S1). Next, the obtained Zmaxi
And the value of Zmini, Zmidi, which is an intermediate value thereof, is obtained.
The reason for obtaining the intermediate value is to collect data in the most stable area (S2). Then, the intersection with the obtained Zmidi luminance curve of FIG.
The coordinates in the X-axis direction are Xj, Xj + 1, Xj + 2,
………. Further, the width h around the Xj,.
, Respectively. For example, in the graph shown in FIG. 3C, the absolute value of the change in Z of Xj is mj, and the absolute value of the change in Z of Xj + 1 is mj + 1 (S
3). The calculation of the luminance change amount is performed for all the Y axes, and the average value of the obtained luminance change amounts is obtained as a glossiness scale (S4, S5). Therefore, the larger the change in luminance of the painted surface with a better glossiness, the larger the value.

FIG. 4 shows an example of a luminance curve obtained from a sample having good glossiness and a sample having poor glossiness. As shown in the figure, it can be seen that the difference in brightness at the boundary between the bright part and the dark part is very clear in the case of good glossiness. On the other hand, it can be seen that the difference in brightness at the boundary of the sample with poor glossiness changes more smoothly than that of the sample with good glossiness. Therefore, by obtaining the transition state of the luminance change at the boundary between the bright part and the dark part, that is, the density gradient as in the present embodiment, it is possible to accurately evaluate the glossiness. In addition, even if the stripe is very fine or rough, the density gradient according to the glossiness can always be captured in the vicinity of the above-mentioned intermediate value Zmidi, and thus has no effect on the shape of the stripe. Instead, high-precision measurement can be performed.

Although the image to be inspected is exemplified in a stripe shape, it is a matter of course that the image to be inspected is not limited to this as long as it can measure the density difference between light and dark. Also, in this embodiment, a very large number of density gradients are obtained and the glossiness is obtained from the average value. However, if a decrease in measurement accuracy is permitted, the number of density gradients to be obtained is reduced to speed up the measurement. It is also possible. That is, it is possible to select between the measurement accuracy priority and the measurement speed priority.

[0021]

As described above, according to the present invention, it is possible to measure glossiness with high accuracy regardless of the shape of an image to be inspected projected onto a painted surface and the state of the painted surface. become able to.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a measuring head section of a painted surface property inspection apparatus according to the present invention.

FIG. 2 is a processing flowchart of the apparatus shown in FIG. 1;

FIG. 3 is a diagram for explaining an operation of a process for calculating glossiness in the flowchart shown in FIG. 2;

FIG. 4 is a diagram showing a difference between a good gloss and a bad gloss.

FIG. 5 is a diagram showing a conventional gloss calculation method.

[Explanation of symbols]

6 CCD camera (input means) 25 Measurement head 30 Image processing device replacement (density gradient calculation means, evaluation calculation means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-18210 (JP, A) JP-A-63-100310 (JP, A) JP-A-63-274847 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G01B 11/00-11/30 G01N 21/00-21/01 G01N 21/17-21/61

Claims (1)

(57) [Claims] 1. A painted surface property inspection apparatus for projecting an inspected image having a different contrast from the painted surface on the painted surface and inspecting the properties of the painted surface based on the inspected image reflected on the painted surface, Input means for inputting the image to be inspected from the painted surface; density gradient for calculating a density gradient at a boundary portion between the painted surface and the image to be inspected based on the image to be inspected input to the input means A paint surface property inspection device comprising: a calculation means; and an evaluation calculation means for calculating and evaluating the glossiness of the painted surface based on the density gradient calculated by the density gradient calculation means.