JPH0626844A - Surface inspection apparatus using inverse reflection screen - Google Patents

Abstract

PURPOSE:To obtain a surface inspecting apparatus with an inverse reflection screen, which can accurately perform the detection of defects and quantization of the irregularity defects by keeping the illuminance ratio by the environment light around an object under inspection and the light from a light source at a constant value. CONSTITUTION:In a surface inspecting apparatus with an inverse reflection screen, an illuminance meter 6, which measures the environment illuminance at the position of an object under inspection 5, a comparison operating part 7, which adjusts the luminous intensity of a light source 4 in response to the measured value of the illuminance meter 6, and power regulating means 8, are provided. The environment illuminance at the position of the object under inspection 5 is measured with the illuminance meter 6. The electric power, which is supplied into the light source 4 for keeping the illuminance ratio between the environment light and the emitted light from the light source constant, is operated with the comparison operating part 7. The luminous intensity of the light source is adjusted with the power adjusting part 8. Therefore, the surface can be inspected under the constant conditions all the time regardless of the change in environment light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection apparatus for automobile outer panels, plastic surfaces, and the like. More specifically, a retroreflective screen is used to emphasize a defective portion on the surface of an object to be inspected as a light and dark image to thereby detect a defect. The present invention relates to a surface inspection device that makes it easy to detect a portion.

[0002]

2. Description of the Related Art The basic structure of a surface inspection apparatus using a retroreflective screen is shown in FIG.
0, a camera 31, and a light source 32. As shown in the figure, the surface of the inspection object 33 is arranged between the retro-reflection screen 30 and the light source 32, and the light of the light source 32 hits the surface of the inspection object 33 and is reflected and directed toward the retro-reflection screen 30. To form a simple optical path. With the above arrangement, the light from the light source 32 is reflected by the inspection object 33, enters the retro-reflective screen 30, and is reflected in almost the same direction as the incident optical axis. It is caught by the camera 31 arranged slightly above. With this configuration, the camera 31 can capture an image in which the unevenness of the surface of the inspection object 33 is optically emphasized, and the defect location on the surface that should be smooth can be easily found. The principle of detecting the surface defect by the retroreflective screen will be described with reference to FIGS. 5 shows the case where there is no defect on the surface of the inspection object 33, and FIG. 6 shows the case where there is a defect. Retroreflective screen 30
Are closely packed with bead-shaped reflecting spheres 34, and each reflecting sphere 34 has a directional reflection pattern for incident light as shown in the figure. As shown in FIGS. 5 and 6, the light coming from the light source direction is reflected by the surface of the inspection object 33 in the direction of the retroreflective screen 30. On the other hand, the camera arranged slightly above the light source near the light source faces the surface of the inspection object 33 from the camera viewing direction in the figure,
The reflected light from the retroreflective screen 30 captures the light that is re-reflected by the inspection object 33. When the respective points A, B and C on the surface of the inspection object 33 are viewed from the camera, as shown in FIG. 5, in a plane having no defects, the same intensity reflected at the angle α of each reflecting sphere 34 of the retroreflective screen 30. You will be seeing the light of, and the camera will see it as a surface with an intermediate brightness without any change in shade. On the other hand, when there is a defect on the surface of the inspection object 33 as shown in FIG. 6, the reflected light of the angle α of the reflecting sphere 34 of the retroreflective screen 30 is captured at the point A where there is no defect as in the above. Light having a strong reflection angle γ is captured at a point (downhill viewed from the camera side), and weak reflected light having a angle β is captured at point C (uphill viewed from the camera side). Therefore, the downhill like point B looks bright and the uphill like point C looks dark. Since the width of the directivity of the reflection pattern of the reflection sphere 34 of the retro-reflection screen 30 is as sharp as about ± 1 degree, even if the defect has a slight inclination, the amount of change in light and shade is large, and the unevenness of the defect is emphasized and observed. Become.

[0003]

In the surface inspection using the retro-reflective screen, when the environmental illuminance to be inspected exceeds the illumination illuminance of the inspection object by the light source, the characteristic that the defect portion is bright and dark enhanced is impaired. ， There was a problem that was greatly affected by the environmental illuminance. Especially when the inspection environment is exposed to strong sunlight, when quantifying unevenness defects, the ambient illuminance was measured with an illuminometer by selecting the same time period, and the predetermined illuminance was obtained. It is necessary to measure at the time point. For example, Fig. 7 shows the situation where the luminous intensity of ambient light is 8LUX and a 20W halogen lamp is used as the light source.
It is a gray level graph on the line AB of the inspection object 33 captured by the camera, and a grayscale image due to slight irregularities on the line AB is clearly shown. However, even though the light source and the inspection object under the same conditions as those shown in FIG. 7 are used and the ambient illuminance is 380 LUX, the gray level on the same AB line shows almost no change in gray level as shown in FIG. ， The defect cannot be detected. The present invention was devised in view of the above-mentioned problems, and it is possible to accurately detect defects and quantify uneven defects by maintaining a constant illuminance ratio by ambient light around the inspection object and light from the light source. It is an object of the present invention to provide a surface inspection device using a retro-reflective screen that can be performed according to the above method.

[0004]

In order to achieve the above object, the means adopted by the present invention is a retroreflective screen, a light source, and an inspection object, and the light from the light source hits the inspection object and is reflected. Then, it is placed at a relative position so as to face the retro-reflective screen, the reflected light when the surface of the inspection object is illuminated by the light source is returned to the inspection object by the retro-reflection screen, and is re-exposed on the surface of the inspection object. In a surface inspection device using a retro-reflective screen, which captures the reflected light with a camera placed near the light source to obtain the unevenness change of the defect portion of the inspection object surface as an image emphasized by the light and dark changes,
A retroreflective screen comprising: an illuminometer for measuring the environmental illuminance at the position of the inspection object; and a light source luminosity adjusting means for adjusting the luminosity of the light source according to the measurement value of the illuminometer. Configured as a surface inspection device.

[0005]

According to the present invention, the ambient illuminance at the inspection object position can be measured by the illuminometer, and the luminous intensity of the light source can be adjusted by the light source luminous intensity adjusting means in accordance with the measured value. The illuminance ratio between the ambient light and the light emitted from the light source is kept constant. Therefore, the surface inspection by the retroreflective screen due to the change of the ambient light can be always performed under a constant condition.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and do not limit the technical scope of the present invention. FIG. 1 is a schematic diagram showing the structure of a surface inspection apparatus using a retroreflective screen according to the first embodiment of the present invention, and FIG. 2 is a structure of a surface inspection apparatus using a retroreflective screen according to the second embodiment of the present invention. And FIG. 3 is a gray level graph showing a change in shading when the illuminance ratio between the ambient light and the light from the light source is corrected to be constant by the apparatus of the embodiment. In FIG. 1, the surface inspection device 1
Puts the inspection object 5 between the basic elements of the retro-reflective screen 2, the camera 3 and the light source 4 in which beads-like reflection spheres are densely arranged on the surface, and the light of the light source 4 hits the surface of the inspection object 5 and is reflected. Are arranged at relative positions so as to face the retro-reflective screen 2. The light from the light source 4 is reflected by the inspection object 5, is incident on the retro-reflective screen 2 and is reflected in almost the same direction as the incident optical axis, so that it is reflected again on the surface of the inspection object 5 and slightly above the light source 4. It is caught by the camera 3 arranged at. With this configuration, the camera 3 can capture an image in which the unevenness of the surface of the inspection object 5 is optically emphasized, and the defect location on the surface that should be smooth can be easily found. The principle of surface defect detection is as described in the related art. In addition to the basic configuration described above, the surface inspection apparatus 1 according to the present embodiment calculates an illuminance meter 6 for measuring the environmental illuminance of the inspection object 5 and the luminosity of the light source 4 from the measured value of the illuminance meter 6. And a power adjustment unit 8 for adjusting the power supplied to the light source 4 according to the light source operating power value calculated by the comparison operation unit 7. Since the light source light intensity adjusting means is configured by the comparison operation unit 7 and the power adjusting unit 8, the change in the environmental illuminance is measured by the illuminance meter 6 and the light intensity of the light source 4 is adjusted, so that the inspection object 5 is The illuminance ratio between the ambient illuminance and the light source illuminance is kept substantially constant. FIG. 3 shows an example in which the illuminance ratio is kept constant by increasing the power of the light source 4 (200 W) in a state where the illuminance of ambient light is large (680 LUX). In the case of the second embodiment shown in FIG. 2, only the ambient illuminance is measured by the illuminometer 6 in a state where the switch 9 is turned off and the irradiation from the light source 4 is stopped. Then, switch 9 is turned on and illuminance meter 6
The total illuminance of ambient light and light from the light source is measured by. The comparison calculation unit 7a to which the measured value of the illuminance meter 6 in each of the ON and OFF states of the switch 9 is input, calculates the illuminance ratio between the illuminance when the switch 9 is off and the illuminance when the switch 9 is on,
The power supplied from the power adjusting unit 8a to the light source 4 is adjusted until the ratio reaches a predetermined constant value. According to this configuration, even when the distance between the light source 4 and the inspection object 5 changes, the illuminance ratio between the ambient light and the light source light can be adjusted to be constant.
With the configurations of the first and second embodiments described above, there is no influence on the quantification of uneven defects due to changes in ambient light, and the detection and quantification of defects regardless of the day / night time zone of the inspection environment or changes in the installation location. Can be carried out accurately.

[0007]

As described above, according to the present invention, the ambient illuminance at the inspection object position can be measured by the illuminometer, and the luminous intensity of the light source can be adjusted by the light source luminous intensity adjusting means in accordance with the measured value. Therefore, the illuminance ratio between the ambient light at the position of the inspection object and the irradiation light from the light source is kept constant. Therefore, surface inspection with a retro-reflective screen due to changes in ambient light
It is possible to provide a surface inspection device that can be always performed under constant conditions.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a surface inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing the configuration of a surface inspection apparatus according to the first embodiment of the present invention.

FIG. 3 is a gray level graph when the light source light intensity is adjusted by the light source light intensity adjusting means of the embodiment apparatus.

FIG. 4 is a schematic diagram showing a basic configuration of a surface inspection using a retroreflective screen.

FIG. 5 is an explanatory diagram showing the principle of surface inspection using a retroreflective screen (when there is no surface defect).

FIG. 6 is an explanatory diagram showing the principle of surface inspection using a retroreflective screen (when there is a surface defect).

FIG. 7 is a gray level graph in a state where the illuminances of ambient light and light from the light source are appropriate.

FIG. 8 is a gray level graph in a state where the ambient light is strong.

[Explanation of symbols]

 1-Surface inspection device 2-Reverse reflection screen 3-Camera 4-Light source 5-Inspection object 6-Illuminance meter 7,7a-Comparison unit (light source light intensity adjusting means) 8,8a- Power adjustment unit (light source light intensity adjustment means)

Claims (1)

[Claims] 1. A retroreflective screen, a light source, and an inspection object are arranged at relative positions such that the light from the light source hits the inspection object and is reflected toward the retroreflective screen. The reflected light when the surface of the object is illuminated by the light source is returned to the object to be inspected by the retroreflective screen, and the light re-reflected on the surface of the object to be inspected is captured by the camera arranged in the vicinity of the light source, so that the object to be inspected In a surface inspection device using a retro-reflective screen that obtains the unevenness change of the defective portion of the surface as an image emphasized by the light and dark changes, an illuminance meter that measures the environmental illuminance at the position of the inspection target and a measurement value of the illuminance meter And a light source light intensity adjusting means for adjusting the light intensity of the light source.