JPS63108249A - Surface defect inspecting device - Google Patents

Abstract

PURPOSE:To inspect whether or not there is a defect in the surface of a body objectively, quantitatively, and automatically by detecting an image of a light- dark pattern projected on the surface to be inspected as a high-low level signal of light, and detecting an irregular signal contained in the level signal and extracting the defect part in the surface to be inspected. CONSTITUTION:An image pickup means M2 detects the image of the light-dark pattern projected on the surface to be inspected by a light-dark pattern projecting means M1 as the high-low level signal of light and a light-dark level detecting means M3 lowers the level of the detected level signal relatively by a specific quantity corresponding to the property of the surface to be inspected, thereby extracting a level signal based upon the light-dark pattern. Then, a defect part extracting means M4 detects the irregular signal contained in the level signal based upon the light-dark pattern to extract the defect part in the surface to be inspected. Thus, the defect part such as an irregularity on a body to be inspected is detected automatically and the unmanned surface inspection of the body is realized by using industrial equipment such as a robot, thereby improving operation efficiency greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Industrial Application Field] The present invention relates to an apparatus for inspecting defects such as surface morphology of an object.

[Prior Art] Conventionally, the presence or absence of irregularities on the surface of an object has been inspected by an inspector based on visual or tactile sense.

This visual or tactile inspection by the inspector is likely to be influenced by the inspector's subjectivity or skill level, and there are problems with the uniformity of the inspection, and the inspection requires a lot of effort and time, which reduces efficiency. Rarely. As a solution to these problems, for example, Japanese Patent Application Laid-Open No. 52-90988
Inventions and proposals have been made, such as the [Method for inspecting surface defects of objects] as shown in the issue. These inventions and proposals project a striped light-dark pattern on the surface of the object being inspected, and if there is a defect such as unevenness on the object surface, the projected light-dark pattern is distorted or disturbed. This is used to inspect the surface for defects.

[Problems to be Solved by the Invention] The above inventions and proposals can determine the presence or absence of defects on the surface of an object based on distortions and disturbances of the bright and dark patterns projected on the surface of the object to be inspected. Although it has the excellent effect of improving work efficiency and improving work efficiency, it is still necessary for inspectors to determine the presence or absence of defects on the surface of objects by determining the degree of distortion and disturbance in bright and dark patterns, etc. However, there still remained the problem that the test results lacked uniformity. For this reason, attempts have been made to quantify the distortions and disturbances of the bright and dark patterns, etc., and use quantitative values to determine the presence or absence of defects on the object surface, but the above problem has not yet been solved. As a result, labor-saving inspection for defects on the surface of objects and unmanned inspection using robots and the like are hindered.

The present invention has been made to solve the above problems, and its purpose is to provide a surface defect inspection device that can objectively, quantitatively, and automatically inspect the presence or absence of defects on the surface of an object. It is said that

1. Texture [Means for solving the problem] The surface defect inspection device of the present invention is configured as follows. That is, as the basic configuration is illustrated in FIG. 1, the surface defect inspection apparatus of the present invention includes: a bright and dark pattern projection means (Ml) that projects a predetermined bright and dark pattern on the surface to be inspected; an imaging means (M2) for detecting the image of the light and dark pattern projected on the surface to be inspected by Ml) as a light intensity level signal; and the wL imaging means (M2).
a light-dark level detection means (M3) for relatively lowering the level of the level signal detected by a predetermined level corresponding to the property of the surface to be inspected to extract a level signal based on a light-dark pattern; and a defect extracting means (M4) for detecting an irregular signal included in the level signal based on the bright and dark pattern extracted by step (M3) and extracting a defect on the surface to be inspected.

Here, the bright and dark pattern projection means (Ml) is a means for projecting a predetermined bright and dark pattern onto the surface to be inspected. Various configurations can be considered, such as configuring it to be projected on the surface. Note that the bright and dark pattern projected on the surface to be inspected may be a virtual image generated by reflection from the surface to be inspected, or may be simply a projected image.

The light/dark level detection means (M3) relatively lowers the level of the light intensity level signal detected by the imaging means (M2) by a predetermined level corresponding to the properties of the surface to be inspected to produce a level signal based on a light/dark pattern. Various configurations are conceivable, such as configuring the means for extracting the light intensity level signal to reduce a value by a predetermined level corresponding to the properties of the surface to be inspected from the level of the light intensity level signal to extract a level signal based on a bright and dark pattern. It will be done. Note that the predetermined level corresponding to the properties of the surface to be inspected refers to a light level signal, a so-called offset signal, that the surface to be inspected itself has.

The defect extracting means (M4) is a light/dark level detecting means (M4).
3) means for detecting an irregular signal included in the level signal based on the bright and dark pattern extracted by step 3) and extracting a defective portion on the surface to be inspected, the irregular signal being detected according to a predetermined direction. It may be configured such that the area is integrated and if the integrated value is greater than or equal to a predetermined value, it is determined to be a defective area. Incidentally, the irregular signal included in the level signal due to the bright and dark pattern is a signal that is generated when the image of the bright and dark pattern projected on the surface of the object being inspected is distorted or disturbed due to defects such as unevenness on the object surface. It is possible to use a comparator or the like to detect this as a level that does not belong to either the bright or dark area, or to detect it using a filter circuit or the like as a part where the level signal of a predetermined cycle of the bright and dark pattern is disturbed. .

[Function] The surface defect inspection apparatus of the present invention having the above-mentioned configuration functions as follows.

The surface defect inspection apparatus of the present invention detects an image of a light and dark pattern projected on the surface to be inspected by a light and dark pattern projection means (Ml) as a light intensity level signal using an imaging means (M2), and detects the detected level signal. The level is relatively lowered by a predetermined level corresponding to the properties of the surface to be inspected using the light and dark level detection means (M3), a level signal based on the light and dark pattern is extracted, and an irregular signal included in the level signal based on this light and dark pattern is detected as a defect. Part extraction means (M4)
It works to detect and extract defects on the surface to be inspected.

[Example] Next, a preferred example will be described with reference to the drawings in order to further clarify the structure of the surface defect inspection apparatus of the present invention.

FIG. 2 is a block diagram showing the configuration of a surface defect inspection apparatus according to an embodiment of the present invention.

The surface defect inspection apparatus of this embodiment mainly includes a light-dark pattern projection device 1 as a light-dark pattern projection means for projecting a striped light-dark pattern onto the surface of an object to be inspected OB to be inspected for the presence or absence of defects such as irregularities. , an ili imaging device 2 as an imaging means that photographs a virtual image of a light and dark pattern projected on the surface of the object to be inspected OB and outputs the imitated virtual image as a light intensity level (hereinafter also referred to as brightness) signal. and a light/dark level detecting means for extracting a level signal based on the light/dark pattern after relatively lowering the brightness corresponding to the surface properties of the object to be inspected OB from the level signal outputted from the vR imaging device 2. A detection circuit 3 and a defect extraction device as a defect extraction means for detecting irregular signals included in a level signal based on a light-dark pattern output from the light-dark level detection circuit 3 and extracting a defect on the surface of the object to be inspected 08. It consists of 4 and. The defect extraction device 4 further includes an irregular signal detection circuit 5 for detecting irregular signals and an irregular region extraction circuit 6.

The bright and dark pattern projecting device 1 is composed of a flat plate 10 having a large number of equally spaced slits and a light source 11 that emits scattered light, and projects a bright and dark pattern (
In this embodiment, the distance between the bright and dark areas is 1.5 mm).

In this embodiment, the object to be inspected OB is made of a glossy iron plate, and the bright and dark pattern is projected as a virtual image.

The imaging device 2 includes an imaging tube (hereinafter referred to as a TV camera) 20
It is composed of etc. The TV camera 20 photographs a virtual image on the surface of the object to be inspected OB, and outputs the bright virtual image to the distributor 30 of the brightness level detection circuit 3 as a light intensity level signal based on a predetermined scanning line. Note that the CRT display DP1 displays an image copied by the TV camera 20 on its screen.

The bright/dark level detection circuit 3 includes a distributor 309 superimposing circuit 31 .
It is composed of a bypass filter circuit 32 and the like. As shown in FIG. 3, the superimposition circuit 31 includes a low-pass filter circuit 35. Comparator 36. Inverter 37. It is composed of analog switches 38 and 39, etc.

The irregular signal detection circuit 5 of the defect extraction device 4 includes an absolute value circuit 50. Low pass filter circuit 51. It is comprised of a comparator 52, a mixer 53, etc., and the irregular part extraction circuit 6 is comprised of an image shrinkage circuit 60, a defect part extraction circuit 61, etc. As shown in FIG. 4, this irregular organ part extraction circuit 6 is
The so-called CPLJ 70, ROM 71 and RAM 72 are the main components, as well as an external input circuit 73 and an external output circuit 7.
4 are connected to each other by a bus 75 as a logic operation circuit. Here, the mixer 53 and the like are connected to the external input circuit 73. Furthermore, CRT display D
P2 displays the video (image) signal output from the mixer 53, and the CRT display DP3 displays the video signal output from the image shrinking circuit 60 as images.

Next, the operation of the surface defect inspection apparatus of this embodiment will be explained using the timing charts of FIGS. 5, 6, and 7 as appropriate. These timing charts are for the image carrier 2.
It represents the output signals of each part of the bright/dark level detection circuit 3 and the defect extraction device 4.

The virtual image of the bright and dark pattern projected onto the inspection object OB by the bright and dark pattern projection device 1 is converted into a video signal vD1 (video signal VDI in the timing chart in FIG. 5) by the TV camera 20 of the image carrier 2, and the brightness level is detected. Distributor 3 of circuit 3
Output to 0. Moreover, this video signal VD1 is CR
The image is also output to the T display DP1, and the image captured by the TV camera 20 is reproduced on the screen of the CRT display DPI. When the surface of the object to be inspected OB is smooth, the video signal VD1 outputted from the TV camera 20 is a sinusoidal signal that regularly has high levels in bright areas and low levels in dark areas, which are originally the characteristics of a bright and dark pattern. However, when there are defects such as unevenness, the bright and dark pattern is distorted and disturbed by the defect, resulting in a so-called intermediate brightness signal ( Irregular signal) will have (
Fig. 5 timing chart video signal VD1). The intermediate brightness part bad, which is distorted and disturbed by this defective part, is
As illustrated pictorially in the figure, it can also be observed on the screen of the CRT display DP1. Note that the video signal VD1 from the TV camera 20 is necessarily a video signal obtained by scanning orthogonal to the bright and dark pattern on the object to be inspected OB. Therefore, the timing chart shown in FIG.
is taken as a parameter.

The video signal VD1 input to the distributor 30 of the bright/dark level detection circuit 3 is separated into the video signal VD2 of the image and the synchronization signal SS (see timing chart in FIG. 5).
Video signal VD2. synchronization signal SS). Video signal VD1
The video signal VD2 has a positive level, and the synchronization signal SS
Since this is a negative level, the distributor 30 can be easily constructed using a rectifier or the like. The video signal VD1 shown in the timing chart of FIG. 5 corresponds to one scanning line.

Video signal VD2 output from distributor 30 is input to superimposition circuit 31. This input video signal VD2
includes the brightness of the surface of the object to be inspected OB (hereinafter simply referred to as brightness ■S). This surface brightness vS varies depending on the surface coating color of the object to be inspected OB. The superimposition circuit 31 functions to lower the voltage level of the video signal VD2 to within a voltage corresponding to the surface brightness VS.

Hereinafter, the function of this superimposition circuit 31 will be explained using the timing charts shown in FIGS. 6 and 7, respectively: + <1> When the surface coating color is white, (ii) When the surface coating color is black. The case will be explained below.

(i) When the surface coating color is white, the video signal VD2 input to the input terminal m1 of the superimposing circuit 31 shown in FIG. (Figure 6 timing chart video signal VD2>).

The superimposition circuit 31 uses a low-pass filter circuit 35 and a comparator 36 to detect the section of the level signal based on the bright and dark pattern within the video signal VD2.

That is, the video signal VD2 is annealed by a low-pass filter circuit 35 configured as a so-called integral circuit, and the annealed video signal 21 (Figure 6 timing chart video signal 21) and a predetermined reference voltage 2] A comparator 36 is used to compare the period signal SPI with the period signal SPI (section signal SP1 in the timing chart of FIG. 6). This section signal S
The section where P1 is at a high level indicates the section where the video signal VD2 has a bright and dark pattern. This section signal SP1 is input to the gate of the analog switch 38, and the section signal SP2 (section signal 5P2 in the timing chart in FIG. 6) obtained by inverting the section signal SP1 using the inverter 37 is input to the gate of the analog switch 39. . This results in
The analog switch 38 outputs its input when the section signal SP1 is at a high level, and the analog switch 39 outputs its input when the section signal SP1 is at a low level.

On the other hand, the analog switch 38 is connected to the video signal VD2.
is input, and the set voltage V2 is input to the analog switch 39. This analog switch 38 and 39
The output sides of are connected to the output terminal m2 of the superimposing circuit 31, respectively. Here, the set voltage V2 is a voltage set in advance to correspond to the surface brightness VS described above.

With the above configuration, the superimposing circuit 31 outputs from the output terminal m2 a video signal V22 (video signal 22 in the timing chart of FIG. 6) in which the set voltage V2 is superimposed on the signal in the section excluding the level signal due to the bright and dark pattern. This results in
This means that the level signal due to the bright and dark pattern is relatively lowered by the set voltage V2.

(ii) If the surface coating color is black, in this case,
The video signal VD2 input to the input terminal m1 is a signal with an overall lower voltage level than when the surface coating color is white (Figure 7 Timing Chart Video Signal VD2
2>.

As in the case of m above, the superimposition circuit 31 uses the low-pass filter circuits 35 . Comparator 3
6. From the inverter 37, each video signal v231 section signal SP3. 7. Timing chart for outputting section signal SP4 Video signal V232 section signal SP3. Using the analog switches 38 and 39, the video signal 24 (timing chart 1 to video signal 24 in FIG. 7) is output from the output terminal m2.

As described above, the video signal VD2 input to the input terminal m1 of the superimposition circuit 31 has a level difference in each case, but the video signal V22 . V24 is each lowered relative to the set voltage V2. Thereby, the signal output from the superimposition circuit 31 is a signal that does not have sudden rises or falls.

Video signal V22 or V2 output from the superimposition circuit 31
4 is input to the bypass filter circuit 32. The bypass filter circuit 32 configured as a differentiating circuit removes so-called low frequency signals. As a result, the video signal V22
Alternatively, V24 is converted into a video signal VD3 in which bright parts of the bright and dark pattern have a positive level and dark parts have a negative level. Therefore,
The intermediate brightness part bad or the boundary part between the bright part and the dark part of the bright and dark pattern becomes a signal of almost zero level (video signal VD3 in the timing chart of FIG. 5). At this time, video signal V22
Or, since V24 is made into a signal that does not have sudden rises or falls due to the function of the superimposition circuit 31,
The video signal VD3 passes through a bypass filter circuit 32 serving as a differentiating circuit and has the surface brightness VS (so-called offset voltage) cut off, resulting in a video signal VD3 free of noise signals.

The video signal VD3 from which the offset voltage has been removed by the bypass filter circuit 32 is input to the absolute value circuit 50 of the irregular signal detection circuit 5. A negative level signal such as a dark part of the video signal VD3 inputted to the absolute value circuit 50 is converted to a positive level signal here (Fig. 5 timing chart video signal VD4>. That is, inputted to the absolute value circuit 50). The converted video signal VD3 becomes a full-wave rectified video signal VD4.

The video signal VD4 outputted from the absolute value circuit 50 is input as is to the plus side of the comparator 52, and is also input to the minus side of the comparator 52 via the low-pass filter circuit 51.

The low-pass filter circuit 51 receives the input video signal VD.
A floating threshold signal SL is generated based on 4 (timing chart in FIG. 5, floating threshold signal SL). As shown in the timing chart of FIG. 1, this floating threshold signal SL is a signal that is smaller than the high level signal of the bright portion of the video signal VD4 and larger than the intermediate brightness portion bad.

Comparator 52 that uses floating threshold signal @SL as a reference value for comparison
outputs a binary video signal VD5 in which bright areas are at high level and dark areas are at low level (video signal VD5 in the timing chart of FIG. 5).

The video signal VD5 is input to the mixer 53, and the synchronization signal SS separated by the above-mentioned distributor 30 is also input to the mixer 53 in order to output the image to the CRT display DP2. The video signal VD6 includes the synchronization signal SS (timing chart in FIG. 5, video signal VD6). The video signal VD6 containing the synchronization signal @SS is output to the image contraction circuit 60 of the irregular front part extraction circuit 6. Note that the video signal VD6 is also output to the CRT display DP2, and the low level signal of the video signal VD6 is displayed as a dark area on the screen of the CRT display DP2.

That is, the boundary line between the bright area and the dark area and the intermediate brightness area bad displayed on the above-mentioned CRT display DPI are displayed as a dark area on the screen.

As is well known, the video signal VD6 input to the image contraction circuit 60 of the irregular front part extraction circuit 6 is a signal that follows the scanning line shown in FIG. That is, in the scanning line rn where the intermediate brightness area bad appears, the number of pixels in the dark area forming the bright and dark pattern of the video signal VD6 is small, and the number of pixels in the intermediate brightness area bad is large. As a result, the image contraction circuit 60
If the number of pixels forming a dark area is equal to or greater than a predetermined number, a so-called image shrinking operation is performed in which the pixels forming a dark area are converted into pixels of a bright area.

This image contraction work is performed until the dark part of the bright and dark pattern disappears (Fig. 5 timing chart video signal VD7
). Here, CRT display DP1. DP2. DP
The screen size of No. 3 is 10,100 mm x 100, and the number of pixels in each horizontal and vertical scanning line is 512. Therefore, the area of one pixel is approximately 0.2 x 0.2 mm2. Further, the image shrinking work is performed as follows.

That is, in one scanning line, only when a predetermined number of dark pixels (in this example, 2 to 3 pixels) continue, is one pixel dark, and this process is performed by forming vertical stripes (
Do this until the dark part) disappears.

The video signal VD7 from which the dark portions of the bright and dark patterns have been removed is output to the defect extraction circuit 61. Furthermore, this video signal VD
7 is also output to the CRT display DP3, and the intermediate brightness portion (irregular portion) bad is displayed on the screen. At this time, the intermediate brightness portion bad is an image that has been slightly contracted by the image contraction circuit 60.

The defective portion extraction circuit 61 determines the size of the area of the intermediate brightness portion bad. In this embodiment, when the size of the intermediate brightness part bad is equal to or larger than the size equivalent to a circle with a diameter of about 1 mm, that is, when the number of pixels in the intermediate brightness part bad is 25 or more, the intermediate brightness part bad is determined to be a defective part. , outputs an NG signal.

Incidentally, the flowchart shown in FIG. 9 is a flowchart representing the operations performed by the brightness level detection circuit 3 and the defect extraction device @4 of the present embodiment, which have been described in detail above. Therefore, the video signal VD from the TV camera 20
1 into a digital image signal, and in addition to the irregular part extraction circuit 6, a brightness level detection circuit 3 and a defect part extraction circuit 5 are used.
If the circuit is configured as a logic operation circuit, the above-described processing may be implemented according to the flowchart shown in FIG. The operations of the irregular front portion extraction circuit 6 described above correspond to steps 180 to 200 of the process shown in FIG.

According to the surface defect inspection apparatus of this embodiment, defects such as irregularities on the object to be inspected OB are detected accurately and automatically using the intermediate brightness portion included in the image of the surface of the object to be inspected 08 captured by the TV camera 20. can be detected. Moreover, the defective portion can be detected by clearly distinguishing between the intermediate brightness portion that occurs at the boundary between the bright and dark portions of the bright and dark pattern and the intermediate brightness portion bad due to the defect by the image shrinking operation.

As a result, surface inspection of objects can be performed unmanned using industrial equipment such as robots, which has the excellent effect of significantly increasing work efficiency. In addition, the size of the intermediate brightness area bad on the object to be inspected OB can be quantified and compared with a quantitative value (in this example, 25 pixels or more) and determined to be a defective area, so the inspection results are uniform. It also has the effect of being able to obtain extremely reliable test results. Furthermore, the effect of the superimposing circuit 31 is that the brightness of the surface itself of the object to be inspected 08 is relatively reduced, thereby further increasing the accuracy of inspection. In addition, since defects such as irregularities can be detected as intermediate brightness areas bad, even when the surface of the object to be inspected O8 is a curved surface, even if the interval between the bright and dark patterns becomes narrow, the defects may cause distortion or This has the excellent effect that the area of the disturbed stripes is constant and accurate inspection results can be obtained. In addition, in this example, the interval between the bright and dark areas of the bright and dark pattern was set to 1.5 mm, but the accuracy of defect detection can be improved by making the stripe interval narrower than the size of the defect you want to detect. It also has the effect that it can be improved.

Although one embodiment of the surface defect inspection device of the present invention has been described above in detail, the surface defect inspection device of the present invention is not limited to the above embodiment, and can be implemented in various ways without departing from the scope of the present invention. Of course, it is possible to do this. For example, in this embodiment, one predetermined value is used as the set voltage V2 used in the superimposing circuit 31, but a plurality of set voltages each corresponding to the paint color of the object to be inspected 08 are prepared in advance. It is also conceivable to configure it so that it is used differently depending on the paint color, or to store the brightness of the object to be inspected OB measured in advance before the inspection and use that value.

Incidentally, the timing chart shown in FIG. 10 shows the bypass filter circuit 32 when the superimposing circuit 31 is not used when the surface coating color of the object to be inspected OB is white in this embodiment. The output signals of the absolute value circuit 50 and the low-pass filter circuit 51 (video signal VD3, video signal VD4 and floating threshold signal SL, respectively) are shown. As can be seen from this timing chart, when the surface of the object to be inspected OB itself has high brightness, a high noise signal appears at the beginning and end of the level signal due to the bright and dark pattern after passing through the bypass filter circuit 32 ( Figure 10 Timing chart
Video signal @VD3), a suitable floating threshold signal SL cannot be created in the low bass filter circuit 51.

Effects of the Invention According to the surface defect inspection apparatus of the present invention, it has an excellent effect of being able to automatically detect defects such as irregularities on an object to be inspected. As a result, surface inspection of objects can be performed unmanned using industrial equipment such as robots, which has the excellent effect of significantly increasing work efficiency. In addition, the size of the intermediate brightness area on the object to be inspected can be quantified and compared with the quantitative value and determined to be a defective area, so the inspection results are uniform and extremely reliable. It also has the effect of being able to obtain the following.

Furthermore, the present invention has the excellent effect that a level signal based on a bright and dark pattern can be extracted from a level signal detected by an imaging means using a bright and dark level detection means, thereby further improving the accuracy of inspection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the basic configuration of a surface defect inspection apparatus according to the present invention, FIG. 2 is a block diagram illustrating the configuration of a surface defect inspection apparatus according to an embodiment of the present invention, and FIG. 3 is a superimposition circuit 3 thereof.
1, FIG. 4 is a block diagram showing the configuration of the irregular recess extraction circuit 6, FIGS. 5, 6, and 7 are timing charts showing the output signals of each part, and FIG. Explanatory diagram showing scanning lines of CRT display DP2, No. 9
The figure shows the brightness level detection circuit 3 and defect extraction device 4.
FIG. 10 is a timing chart showing the output signals of the bypass filter circuit 32 and the like when the superimposing circuit 31 is not used. 1... Brightness pattern projection device 2... Imaging device 3... Brightness level detection circuit 4... Defect part extraction device 5... Irregular signal detection circuit 5... Irregular recessed part extraction circuit 31. ...Superimposition circuit 38.39...Analog switch DPI, DP2. DP3...CRT display ba
d...Defect part

Claims (2)

[Claims] (1) Light and dark pattern projection means for projecting a predetermined light and dark pattern onto the surface to be inspected; and imaging for detecting the image of the light and dark pattern projected on the surface to be inspected by the light and dark pattern projection means as a light intensity level signal. means, brightness level detection means for relatively lowering the level of the level signal detected by the imaging means by a predetermined level corresponding to the properties of the surface to be inspected to extract a level signal based on a brightness and darkness pattern; A surface defect inspection apparatus comprising: defect extracting means for detecting irregular signals included in the level signal based on the bright and dark pattern extracted by the level detecting means and extracting a defective portion of the surface to be inspected. (2) The light-dark level detection means detects the light-dark pattern by comparing the light-dark pattern of the level signal detected by the imaging means with a predetermined reference value; 2. The surface defect inspection apparatus according to claim 1, further comprising set voltage superimposing means for superimposing a predetermined set voltage on the level signal excluding the bright and dark sections detected by the means.