JPH0459563B2 - - Google Patents

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention provides a hollow hole measuring method suitable for measuring the dimensions of circular or slit-shaped hollow holes formed on a running steel strip. and devices.

(Prior Art) A shadow mask for a color cathode ray tube has a precise structure in which openings are formed with a certain regularity.
If the position or size of this aperture is inaccurate, the electron beam will not correctly reach the corresponding phosphor, deteriorating the image characteristics of the color cathode ray tube. Therefore, with the recent increase in the definition of color cathode ray tubes, techniques have been developed to manufacture the apertures of shadow masks with high precision.

A two-step etching method has been proposed as one of such manufacturing techniques. This is a method in which the second stage etching is controlled by parameters obtained by measuring the recessed holes (not penetrating) formed in the first stage etching. in this case,
The finished dimensions of the opening are determined by the dimensions of the recessed hole formed in the first stage of etching. Therefore, it is essential to control the process by measuring the dimensions of the recessed holes formed in the first step in order to improve the yield.

By the way, the following two methods have conventionally been used to achieve this purpose. That is, a steel plate punching machine is installed on the line, and the punched steel plates are measured offline. Using a microscopic microscope, an inspector visually measures the steel plate as it moves.

However, in the above method, (a) there is a lower limit to the traveling speed of the steel plate for efficiency reasons, and the impact caused by punching causes an adverse effect. (b) Since the punched part cannot be used as a product, there is a limit to the amount of data that can be collected. (c) It takes time to obtain measurement results. As a result, feedback to the process is delayed,
There is a possibility that many defective products will be produced. (d) It is difficult to monitor a fixed location.

In addition, in the above method, (a)' resolution is low;
Additionally, there are variations in measurement accuracy among inspectors.
(b) If the iron plate travels at a high speed, measurement may become impossible. (c) In many cases, the steel plate is damaged during measurement, resulting in that part being defective.
(d)' Since the inspector has to follow the iron plate, there is a problem with work safety.

(Problems to be solved by the invention)
This was done to solve the problems in (d) to (d) and (a) to (d). It is an object of the present invention to provide a method and apparatus for measuring the dimensions of a recessed hole.

[Structure of the Invention] (Means and Effects for Solving the Problems) The present invention has been made in consideration of the above-mentioned problems, and includes an imaging step of imaging a test object and outputting an image signal, and A binarization process in which the signal is binarized using a preset threshold value and outputs binarized image data consisting of "1" and "0"; After performing a reduction process that converts "0" points that have at least one "0" signal into "1", "1" points that have at least one "0" signal as neighbors are converted to "0". The first noise removal process performs an enlargement process to convert into The second noise removal step converts the data to “0” and fills in the holes, and the pattern formed by the “0” points of the binarized image data obtained in the second noise removal step. The third step is to determine pass/fail by comparing the shape with a preset reference value and convert the "0" point of the defective pattern to "1".
and a shape measuring step of measuring the shape of a pattern formed by "0" points based on the binarized image data obtained in the third noise removing step. This is a hollow hole measurement method.

The present invention also provides an imaging means for capturing an image of a test object and outputting an image signal, and a binarization of the image signal into "1" and "0" by binarizing the image signal using a preset threshold value. Binarization means for outputting image data, reduction processing for converting "0" points that have at least one "1" signal as a neighborhood in the binary image data into "1", and a reduction process as a neighborhood. A first noise removing means performs an enlargement process of converting a "1" point that has at least one "0" signal into a "0"; A second noise removing means performs a hole-filling process by converting a "1" point surrounded by "0"s into "0" in the digitized image data; “0” of the binarized image data
A third noise that determines pass/fail by comparing the shape of the pattern formed by the points with a preset reference value and converts the "0" points of the defective pattern to "1". It is characterized by comprising a removing means and a shape measuring means for measuring the shape of a pattern formed by "0" points based on the binarized image data obtained by the third noise removing means. It is a hollow hole measuring device.

(Example) Hereinafter, an example of the present invention will be explained in detail with reference to the drawings.

1 to 3 show a hollow hole measuring device according to an embodiment of the present invention. This device includes an imaging section 3 that captures an image of a steel plate 1, which is an object to be inspected, and converts it into an image signal, and an arithmetic control section that controls the operation of the imaging section 3 and performs arithmetic processing on the image signal output from the imaging section 3. 4. In FIGS. 1 and 2, the imaging section is disposed facing the iron plate 1. As shown in FIG. The iron plate 1 has a band-like shape, and circular holes 2 are formed regularly on its surface by etching or other processing.
... are formed and run in the direction of arrow X driven by rollers R.

The imaging unit 3 is an ITV that images the iron plate 1.
(Industrial Television) A camera 6, an optical system 8 that illuminates the surface of the iron plate 1 and forms an enlarged optical image of the reflected light on the imaging surface of the ITV camera 6;
and an automatic focus section 9 that adjusts the focus position of the camera to be on the iron plate 1, and is supported by a support section 7.

The optical system 8 includes a strobe light source 20 that projects strobe light onto the iron plate 1 and an enlarged light image of the reflected light.
It also includes a lens system 17 that forms an image on the imaging surface of the ITV camera 6. In FIG. 2, the optical system 8 is housed in a housing 16, and the measuring section of the housing 16 includes a storage section 19 that stores a strobe light source 18 so that the optical axis of the lens system 17 and the strobe light are perpendicular to each other. An ITV camera 6 is placed on the top. In the figure, strobe light emitted from a strobe light source 20 is refracted by a half mirror 24 via a lens system 23 and projected onto the iron plate 1 by a lens system 17. This reflected light passes through the half mirror 24 via the lens system 17 again, and then passes through the ITV camera 6 disposed above.
The image is formed on the imaging surface of The magnification of the lens system 17 is set so that the ITV camera 6 can image several circular holes 2 . Note that the other measuring parts of the housing 16 have a rack 25 in the Z direction.
is formed, and a rejection sensor 26 is disposed at the bottom.

The automatic focus unit 9 includes a measurement/rejection sensor 2 that measures the distance to the iron plate 1 and outputs an electric signal SD according to the measured value.
6, a servo circuit 27 that outputs a control signal SC that eliminates the difference between the actual position of the optical system 8 and the focal position of the strobe light based on this electric signal SD, and a motor 29 that is operated by this control signal SC. It is equipped with The motor 29 rotates a pinion 28 that meshes with the rack 25, thereby moving the housing 16 up and down to align it with the focal position. Note that the automatic focus section 9 is attached to a mounting base 14, which will be described later.
installed on.

The support portion 7 includes a feed screw 13 whose axis extends in the Y direction and whose both ends are supported by bearings (not shown).
A mount 14 is screwed into the feed screw 13, and a handle 15 is connected to one end of the feed screw 13 and rotates the feed screw 13 to adjust the position of the mount in the Y direction.

Note that in this device, the mark detection section 12 is arranged adjacent to the imaging section 3. Mark detection section 12
includes a light projector that projects inspection light onto the iron plate 1, and a light receiver that receives the reflected light and outputs a detection signal SM. Usually, one mark 11 is placed on each measurement part of the iron plate 1, corresponding to the shadow mask part 10.
... are formed, the mark detection section 12 detects the marks 11 ... and sends the detection signal SM to the calculation control section 4.
It is now output to .

Next, the configuration of the calculation control section 4 will be explained.

In FIG. 3, the calculation control section 4 includes an A/D conversion circuit 33, an image memory 35, and a calculation section 36.

The A/D conversion circuit 33 has a circuit configuration that performs analog/digital conversion on the image signal SI1 output from the ITV camera 6 and outputs a digital image signal SI2.

The image memory 35 is connected to the A/D conversion circuit 33 and the calculation section 36, and receives the digital image signal SI.
2 can be temporarily stored as image data.

The calculation unit 36 processes the image data stored in the image memory 35 according to the flowchart shown in FIG. It is equipped with functions that control operations, and usually consists of a minicomputer and various hardware circuits.

Note that the arithmetic control unit 4 of this device includes a console 5.
0 is connected to a display unit 5 consisting of a printer, display, etc., which allows input of various commands from the outside and allows monitoring of each process.

Next, a method of measuring the circular holes 2 using the recessed hole measuring device having the above configuration will be explained.

After driving the roller R to move the iron plate 1 in the X direction and rotating the handle 15 to align the ITV camera 6 to the position in the Y direction where the iron plate 1 should be imaged, the depression hole measuring device is activated. .

First, the automatic focus section 9 receives a command from the calculation section 36 and adjusts the focal position of the optical system 8. That is, the measurement/rejection sensor 26 outputs an electric signal SD according to the distance from the iron plate 1, and the servo circuit 27 that receives this outputs a control signal SC to the motor to eliminate the difference between the actual position and the focal position of the strobe light. Issued on the 29th. Then, the motor 29 starts and attaches the optical system 8 to the mounting base 14.
The focus position is adjusted by moving it in the Z direction. Note that such focus position adjustment is performed consistently during measurement.

Next, in the mark detection section 12, the inspection light is projected from the light projecting section, the light receiving section receives the reflected light from the iron plate 1, and when the mark on the iron plate 1 is detected, the detection signal SM is output.

The calculation unit 36 detects, based on the detection signal SM, that the shadow mask portion of the iron plate 1 has reached the imaging position, and outputs the illumination signal SL to the optical system 8 after a predetermined delay time _tR . Then, the strobe light source 20
A strobe light is emitted from the vehicle, and the strobe light passes through a lens system 23, is refracted by a half mirror 24, and is projected onto the running iron plate 1 via a lens system 17. At this time, the reflected light from the iron plate 1 is imaged by the lens system 17 on the imaging surface of the ITV camera 6 as a stationary enlarged optical image.

The ITV camera 6 converts the captured enlarged optical image into an image signal SI1 and outputs it (step S ₁ in FIGS. 5 and 4). Next, the A/D conversion circuit 33 performs analog/digital conversion on the imaging signal SI1 and outputs a digital imaging signal SI2. The image memory 35 temporarily stores the digital imaging signal SI2 as image data.

Therefore, when strobe light is projected onto the shadow mask part of the iron plate 1, the base part is reflected and becomes a bright part, and the recessed hole part becomes a dark part, so if this reflected light is imaged, theoretically The surface shape can be accurately captured. however,
In reality, since the iron plate 1 base is rough, dark areas are formed in areas other than the recessed holes 2, causing type 1 noise 51...
Also, since the center of the recessed hole 2 is flat, it is reflected and becomes a bright part, causing type 2 noise 52 . . . . Therefore, the captured image forms a binarized image as shown in FIG. It should be noted that some of the first type noises 51 exist apart from the hollow holes 2 and others exist coupled to each other, and some of the second type noises 52 exist from the hollow holes 2... There are things that exist internally, isolated, and things that exist in combination with the outside. These type 1 noises 51... and type 2 noises 52... cause a decrease in measurement accuracy.

The calculation unit 36 performs processing such as noise removal and shape measurement on the image data stored in the image memory 35 according to the flowchart shown in FIG. below,
The processing in the calculation unit 36 will be explained in detail.

First, the digital image signal SI2 is smoothed to obtain a smoothed signal SI3 (step S ₂ in FIG. 4). Then,
The smoothed signal SI3 is binarized using a threshold value VT, and converted into a binarized signal SI4 in which the bright part is a signal of "1" and the dark part is a signal of "0" (fifth
Figures and Figure 4 Step _S3 ). Here, hollow hole 2
The ... part has been etched to make the surface smooth, so there is less variation in the brightness of the reflected light.
Since the surface of the base of the iron plate 1 is rough, the brightness of the reflected light varies greatly. Therefore, when a brightness (voltage value) histogram is taken for the smoothed signal SI3, as shown in FIG. 7, the recessed hole 2...
The dark area is the steep mountain part 53 on the left side, and the iron plate 1
The bright part of the substrate etc. becomes a gentle hill part 54 on the right side. In this embodiment, the voltage value related to the boundary between the mountain part 53 and the hill part 54 is set as the threshold value VT, and the above-mentioned binarization processing is performed to efficiently remove noise, but this alone is not enough as shown in FIG. As such, the removal of the first type noise 51 and the second type noise 52 is insufficient.

Next, as shown in FIG. 9, the entire image data is reduced (step S 4 in FIG. ₄ ). In general, reduction processing of a binarized image involves converting a "0" point in the binarized image data that has at least one "1" signal nearby into a "1" signal, that is, " 0”
This is done by removing the surrounding area of the island, reducing the size of the island. As a result, protrusions and minute lines on the image data are removed, and the first type noise 51 remains as isolated points.

Next, as shown in Figure 10, "1" and "0"
After carrying out an inversion process to invert the pixel, the isolated point is removed by converting the remaining "1" point of one pixel to "0" (step _S5 in FIG. 4). At this time, large noise 51 formed from multiple pixels,
52... and the point "1" related to depression hole 2... remains without being removed.

Next, as shown in FIG. 11, an enlargement process is performed to restore the reduced image to its original size (step S ₆ in FIG. 4). Here, in the enlarging process of the binarized image, since the image data is inverted, a "0" point that has even one "1" signal is converted to "1", that is, "0" This is done by fleshing out the area around the island. As a result, the size of the “0” island existing on the image data is restored, but
Protrusions and minute lines that have already disappeared will not return.

Here, in the image data shown in FIG. 11, it is not possible to measure the dimensions of "0" islands such as the hollow hole 60, which is cut at the periphery and a part is missing.
These are removed as shown in the figure (step _S7 in Figure 4). Furthermore, as shown in FIG. 13, the second type noise 52 is removed by converting "0" in the recessed hole 2 to "1" and performing hole filling processing (step S ₈ in FIG. 4). ). In this way, only islands in which "1"s are clustered together, such as the hollow hole 2 . . . and the large type 1 noise 51 . . . , are left in the image data.

Next, labeling is performed for each of these "1" islands (step S ₉ in FIG. 4). Each labeled island is converted to an individual brightness, and from then on, by specifying the brightness, islands can be read and processed for each label.

Therefore, parameters indicating the shape of each labeled island, such as area, circumference, and moment of inertia, are calculated, and these values are compared with standard values set in advance based on the dimensions and shape of the hollow hole 2. . Here, if the area of the island is smaller than the area of the hollow hole 2 as shown in FIG. As shown in Figure 16, if the difference between the second moment of the island and that of the hollow hole 2 is too large, this is determined to be type 1 noise or a hollow hole with a defective shape, and "1" is changed to "0". ” and delete it (Step _S10 in Figure 4).

Next, measurements and other processing are performed on the remaining islands. In this embodiment, the recessed hole is circular, and for example, the diameter of the circle is determined by the following procedure. That is, first, the diameter D of each island in the image data is determined by the following equation (step S ₁₁ in FIG. 4). However, S is the area of the island.

D=2√ Next, calculate the average value of the obtained D, and use this as the diameter of the hollow hole 2.

The measurement result is displayed on the display unit 5, and the measurement value is compared with a reference value set in advance via the console 50, and if the measurement value deviates from the reference value by a predetermined amount or more, the measurement result is displayed on the display unit 5. At this time, a defect occurrence signal SN is output to the process control computer 41 that controls the entire etching line.

As described above, the hollow hole measuring device of this embodiment is capable of measuring the hollow holes 2 formed in the iron plate 1 running at high speed.
The dimensions of ... can be automatically measured online with high precision (resolution of several μm). Furthermore, since the inspection is performed without contact, the iron plate 1 is not damaged.
Further, since the measurement time can be carried out in a few seconds, it is possible to obtain a large amount of measurement data, and even if a defect occurs, feedback to the process can be quickly carried out. In addition, the iron plate 1 is detected by the detection signal SM output from the mark detection section 12.
It becomes possible to measure the position of the shadow mask area. Furthermore, the burden on inspectors is reduced, labor and manpower can be saved, and work safety is improved.

In addition, Y of the ITV camera 6 in the above embodiment
The directional movement mechanism is not limited to a feed screw, and may be implemented using, for example, a pulley and a roller. Also, the imaging means is instead of the ITV camera 6.
For example, a CCD (Charge Coupled Device) camera,
Other image sensors such as line sensors may also be used. In addition, the mark 11 is detected by the mark detection unit 12.
Instead of detecting..., shadow mask region 10
... itself may be detected.

Further, in this embodiment, the measurement item for the recessed holes 2 is only the diameter, but ellipticity, maximum diameter, minimum diameter, etc. may also be measured. Further, smoothing, reduction, and enlargement may be repeated as necessary. Furthermore, the smoothing process may be omitted if there is little high-frequency noise.

Next, a method of measuring slit-shaped depressions 55 having a constant longitudinal direction using the depression measuring device shown in FIGS. 1 to 3 will be described.

FIG. 17 shows image data obtained by imaging the iron plate 1 in which the slit-shaped recesses 55 are formed. In this case as well, as in the case of FIG. 6, type 1 noise 56 and type 2 noise 57 exist, so in order to measure the width W and interval T of the recessed hole 55 with high accuracy, these noises are necessary. Noise needs to be removed. Noise removal is performed by steps _S1 to _S10 shown in the flowchart of FIG. 18, but since it is exactly the same as that of FIG. 4, the explanation thereof will be omitted.

Figure 18 After Step S ₁₀ , the recessed hole 55...
(Step S ₁₂ in Fig. 18). This correction is performed by moving the image data so that the longitudinal direction of the recessed holes 55 is parallel to the vertical axis based on the average value of the angle of the principal axis of the secondary moment obtained in step _S10 of FIG. Figure 19).

Next, based on a command from the console 50, it is determined whether or not to move to the width gauge side (step S'). Width measurement is performed using the following steps. First, as shown in FIG. 20, one recessed hole 55 for each label is projected onto the horizontal axis. Next, this projection data is scanned in the horizontal axis direction, and several percent of the area at both ends of the chevron is cut out as noise to determine edges E1 and E2 in the width direction (step S ₁₃ in FIG. 18). Find the width W.

After step _S13 is completed, it is determined whether or not to measure the distance based on a command from the console 50 (step S'').The distance measurement is performed using the data after step _S6 in FIG. First, as shown in Fig. 21, only the recessed holes 55 in one column direction of the corrected image data are surrounded by a window 58 (step 58 in Fig. 18).
_S14 ). Next, open window 5 as shown in Figure 22.
Project 8 onto the vertical axis. This projection data is binarized using a pair of thresholds VTD1 and VTD2, and the interval T
seek. The above threshold values VTD1 and VTD2 are respectively 80 to 90% of the width of the recessed hole 55 that has already been determined.
%, 10 to 20%. First, scanning for binarization is performed sequentially using the threshold value VTD1, and then
When the projection value becomes smaller than VTD1, the threshold
Switch to VTD2 and continue binarization processing. Then, the point where the projection value is smaller than the threshold value VTD2 is defined as the lower edge of the recessed hole 55. Further, the threshold value is returned to VTD1, and scanning for binarization is continued again. Then, when the projection value becomes larger than the threshold value VTD1, it is switched to the threshold value VTD2, and this time scanning is performed in the opposite direction, and the point where the projection value becomes smaller than the threshold value VTD2 is defined as the upper edge of the slit hole 55. By repeating this process, the hollow hole 5
Edge detection can be performed accurately without being affected by the noise that exists between 5 and 5.

Then, the average values of the width W and the interval T are calculated, and these are used as the width and interval of the slit-shaped recessed holes 55, and a predetermined process is performed in the same manner as the circular recessed holes 2. .

As described above, the hollow hole measuring method and apparatus of the present invention achieves the same effect when measuring the slit-shaped hollow holes 55 as in the case of the circular hollow holes 2 described above. Further, the shape is not limited to a circular shape or a slit shape, and any shape such as a square shape, an ellipse shape, a diamond shape, a rectangular shape, a trapezoid shape, an egg shape, etc. can be applied. Furthermore, in FIG. 18, it is not necessary to perform both width measurement and distance measurement, and only one of them may be performed. Further, the object to be tested according to the present invention is not limited to the iron plate 1, but can be applied to shape measurement of a hollow hole formed in any object.

[Effect of the invention] According to the hollow hole measuring method and device of the present invention,
It is possible to automatically measure recesses formed in a moving test object online and with high precision.
Therefore, the burden on inspectors is reduced and work safety is improved, and it becomes possible to perform 100% inspection instead of sampling inspection, and when used for process control, it is possible to improve reliability and yield.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a hollow hole measuring device according to an embodiment of the present invention, Fig. 2 is a cross-sectional front view thereof, Fig. 3 is a block diagram showing its electric circuit system, and Fig. 4 is a flowchart showing its operation. Chart, Figure 5 is a timing chart of electrical signals generated in Figure 3,
Figure 6 is an enlarged plan view of the circular hole, Figure 7 is a diagram showing how to determine the binarization threshold, Figures 8 to 13 are diagrams showing image data in the noise removal process, and Figures 14 to 13 are diagrams showing image data in the noise removal process. Figure 16 shows a circular hole with a defective shape, Figure 17
The figure is an enlarged plan view of the slit hole, Fig. 18 is a flowchart for measuring the dimensions of the slit hole, Fig. 19 is an enlarged plan view of the slit hole whose inclination has been corrected, and Figs. 20 to 22 are the width and width of the slit hole. It is a figure which shows interval measurement. 1... Iron plate (object to be inspected), 2... Circular hole (dented hole), 4... Arithmetic control section (image processing section), 6...
...ITV camera (imaging means), 34... Binarization circuit (binarization means), 36... Arithmetic unit.

Claims (1)

[Scope of Claims] 1. An imaging step of capturing an image of a test object and outputting an image signal, and binarizing the image signal using a preset threshold value to set bright areas as "1" and dark areas as "0". A binarization process that outputs binarized image data as ``, and converting ``0'' points in the binarized image data that have at least one nearby signal of ``1'' to ``1.'' a first noise removal step of performing an enlargement process of converting a “1” point that has at least one “0” signal as a neighbor into a “0” after performing a reduction process;
A second noise removal process that performs hole-filling processing by converting "1" points surrounded by "0"s into "0"s in the binarized image data obtained in the first noise removal step. and a reference value set in advance as a value indicating the feature of the shape of a pattern formed by clusters of “0” in the binarized image data obtained by the second noise removal step. a third noise removal step of determining the quality of the pattern by comparing it with the pattern and converting the "0" point of the defective pattern to "1";
A hollow hole measuring method characterized by comprising a shape measuring step of measuring the shape of a pattern formed by clusters of "0" based on the binarized image data obtained in the third noise removal step. . 2. An imaging means for capturing an image of the object to be examined and outputting an image signal, and binarizing the image signal using a preset threshold value to set bright areas as "1" and dark areas as "0". Binarization means for outputting image data, reduction processing for converting "0" points that have at least one "1" signal as a neighborhood in the binary image data into "1", and a reduction process as a neighborhood. A first noise removing means performs an enlargement process of converting a "1" point that has at least one "0" signal into a "0"; A second noise removing means performs a hole-filling process by converting a "1" point surrounded by "0"s into "0" in the digitized image data; The value representing the characteristic of the shape of the pattern formed by clusters of "0" out of the binarized image data is compared with a preset reference value to determine whether the pattern is defective or not. a third noise removing means for converting "0" points of the pattern into "1";
1. A hollow hole measuring device comprising shape measuring means for measuring the shape of a pattern formed by clusters of "0" based on the binarized image data obtained by the noise removing means.