JPH08101017A - Dimension measuring instrument - Google Patents

Abstract

PURPOSE: To provide a dimension measuring instrument which can prevent the dropping of working efficiency and, at the same time, can measure the dimension of a moving object to be measured with high accuracy by constituting the instrument so that the instrument can measure the object in a moving state. CONSTITUTION: Of two cameras 14 and 16, the movable camera 16 can be moved in parallel with x-axis by means of a movable table 18. The interval between the cameras 14 and 16 is set at the nominal value of the dimension to be measured of an object 10 to be measured. The object 10 is carried in parallel with x-axis by means of a carrying means 12. When the object 10 enters a measuring area, a stroboscope 22 emits light. Since the light emitting period of the stroboscope 22 is as short as about 10μsec, the movement of the object 10 is negligible. Synchronously with the light emitted from the stroboscope 22, the pictures taken with the cameras 14 and 16 are frozen and fetched to a memory. After the pictures are suitably processed and the end sections of the object 10 are recognized, the dimension of the object 10 is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimension measuring apparatus for automatically measuring the dimension of a machined product or a molded product (shaped steel, caterpillar block, etc.) which is moving by a conveyer or the like.

[0002]

2. Description of the Related Art The simplest method for measuring the dimensions of a measuring object with a camera is shown in FIG. In FIG. 5A, the background illumination 52 is provided behind the conveyed measurement target 50, and the one-dimensional CCD camera 54 is provided in front of the measurement target 50. When the object 50 to be measured enters the field of view of the one-dimensional CCD camera 54, the transporting means is once stopped and illumination is applied from behind, and the object to be measured 5 is measured by the one-dimensional CCD camera.
Image 0. At this time, the one-dimensional CCD camera 54 outputs an image signal 56 as shown in FIG. This signal will have zero values where the illumination is directly on and high levels where the illumination is shadowed. When this is binarized with an appropriate threshold value SL, a binary signal as shown in FIG. 6C is obtained, and the rising edge of this signal corresponds to the left end of the measurement object 50 and the falling edge corresponds to the right end. Therefore,
By counting the number of pixels for which this signal is high, the length of the measuring object 50 can be obtained.

A method for measuring the size of a moving object to be measured by using two cameras is disclosed in Japanese Patent Laid-Open No. 1-260303.
Proposed in the issue. In this method, two cameras are arranged in advance at intervals of a reference size, and these cameras synchronously image the length measurement region. Then, this image is processed to specify the length measurement region with each of the two cameras, and the dimension of the measurement object is obtained from these positions and the distance between the two cameras. In this method, the cameras may be arranged at intervals of the reference size, and therefore, the feature is that the measurement can be performed even if the size of the measurement object is large.

[0004]

By the way, in the conventional method using one one-dimensional CCD camera, it is necessary to temporarily stop the object to be measured, so that there is a problem that the original production efficiency is lowered. Further, since the image is captured by only one camera, when the size of the measurement target becomes large, the resolution per pixel decreases because it is necessary to keep the camera away from the measurement target so that the entire measurement target fits in the visual field. There is a drawback that the measurement accuracy is reduced. Further, when the size of the measurement target becomes large, the camera images the measurement target from an angle, which also causes a decrease in measurement accuracy.

In order to avoid a decrease in measurement accuracy, it is common to prepare a calibration plate or the like having the same dimensions as the object to be measured in advance and measure the dimensions with this as a reference. Therefore, it is necessary to prepare and store a large number of calibration plates, which results in an extra cost. Moreover, the calibration plate must be replaced and calibrated every time the object to be measured changes, which inevitably results in a decrease in production efficiency.

Further, the length measuring device for a moving body proposed in Japanese Patent Laid-Open No. 1-260303 is capable of measuring a dimension even when an object to be measured is moving, which is described in the specification. As described above, when the measurement target is imaged for 1/60 second, the length measurement site in the image captured by the camera becomes unclear due to the movement of the measurement target during this period. For example, if the measurement target moves at a speed of 15 meters per minute, the measurement target moves about 3.8 mm in 1 / 60th of a second. Therefore, a blur of this degree occurs in the image, and a measurement error similar to this length occurs. Therefore, such a device cannot be used in a measurement field that requires an accurate measurement accuracy of several μm.

The present invention has been made based on the above-mentioned circumstances, and it is possible to measure the size of a moving object to be measured while it is being moved, thereby preventing a decrease in work efficiency and achieving high accuracy. It is an object of the present invention to provide a dimension measuring device that enables dimension measurement.

[0008]

According to a first aspect of the present invention for achieving the above object, there is provided a first means for conveying an object to be measured, and a first image-capturing portion of the object in the conveying direction. The second image pickup means for picking up the image pickup means and the second end portion in the transport direction, and the interval between the reference point of the first image pickup means and the reference point of the second image pickup means is from the front end to the rear end of the measurement object. Up to a distance equal to the nominal value of the moving means for moving one or both of the first and second imaging means in parallel with the transport direction, and the tip of the measurement object is the first. The flash unit that emits light when the rear end of the measuring object enters the field of view of the second image capturing unit and enters the field of view of the image capturing unit, and the first and second flash units in synchronization with the light emission of the flash unit. An image capturing means for capturing an image captured by the image capturing means, and an image capturing means based on the captured image. It is characterized in that it comprises a calculating means for calculating a size of up to the rear end from the tip of the measurement object are.

According to a second aspect of the present invention, in the first aspect of the invention, there is provided means for adjusting a distance between the measurement object and the first and second imaging means according to the type of the measurement object. It is characterized by having.

According to a third aspect of the present invention, in the first or second aspect of the invention, the first and second image pickup means images the measurement object from a lateral direction, and a certain range. All of the upper end of the measuring object having a height within the first and second imaging means to fit within the field of view, has a plurality of height levels discretely set in advance, the measuring object It is characterized by comprising means for moving the upper and lower positions of the first and second image pickup means between the plurality of height levels according to a change in height.

[0011]

According to the present invention, the first and second image pickup means take images with a period of, for example, 1/30 second, because the flash means is used as illumination, so that the image captured by the image capturing means is Only the image is captured while the flash means is emitting light. Since the flashing means emits light for a very short time, if the moving speed of the measuring object is set at 15 meters per minute, for example, the moving distance of the measuring object during this period is so small that it can be ignored, and therefore, it is taken in. The positions of the front end and the rear end are clear in the image. Furthermore,
Since the distance between the reference points of the first and second image pickup means is set in advance to the same value as the nominal value of the measurement object, the positions of the front end and the rear end in the captured image, and both reference points From the distance to the distance, the dimension from the front end portion to the rear end portion of the measurement object can be obtained by the calculation means.

Since the distance between the first and second image pickup means and the measurement object may change depending on the type of the measurement object, the distance between the measurement object and the first and second image pickup means may be different. By providing a means for adjusting the interval of, for example, the distance between the measurement object and the first and second imaging means is kept constant, and focusing of the imaging means and adjustment of resolution are omitted. You can

Further, when measuring the dimension of the measuring object in the moving direction, the position of the measuring portion in the height direction within the visual field of the image pickup means may be within the range of the visual field and does not have to be always constant. . Therefore, even if a discrete height level is set in advance for the position of the image pickup means in the height direction and the height of the image pickup means is adjusted therein, the required height can be adjusted. By doing so, the mechanism for adjusting the height of the image pickup means is simplified.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an overall configuration of a dimension measuring apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing a positional relationship between the visual fields of two cameras and an object to be measured according to the embodiment of the present invention. Is.

The apparatus shown in FIG. 1 uses a caterpillar block as the measuring object 10 as an example. The caterpillar block is an individual block that is connected in an annular shape to form a caterpillar such as a bulldozer, and is obtained by cutting an elongated steel material cast into a predetermined shape with a shear into a predetermined dimension. The size of one caterpillar block, which is an object to be measured in this embodiment, is large and the length is 1000.
mm, width about 500 mm.

The size measuring device of FIG. 1 measures the size of the cut caterpillar block. Incidentally, the conveying means 12, the cameras 14 and 16 and the moving table 1 in FIG.
8, the sensor 20, the strobe 22, and the defective product removing mechanism 32 are shown from above (from the z-axis direction), the controller 24, the personal computer 26,
The image processing device 28 and the warning light 30 are shown as a block diagram.

The apparatus of FIG. 1 comprises two cameras 14 and 16. The former is a fixed camera and the latter is a moving camera, both of which are arranged on a straight line parallel to the x-axis, but the moving camera 16 can be moved left and right by a moving table 18. This movement is automatically controlled by the controller 24. The caterpillar block, which is the measurement object 10, is moved from the right to the left (in the direction of the arrow) along the x-axis at a speed of, for example, 15 meters per minute by the conveying means 12 such as a conveyor.
Be transported. At that time, the measuring object 10 is conveyed by the conveying means 1 so that the dimension from the front end to the rear end to be measured is parallel to the x axis.
Place on top of 2.

When the measuring object 10 enters the measuring area,
When the front end of the measuring object 10 enters the visual field of the fixed camera 14 and the rear end thereof enters the visual field of the moving camera 16, the sensor 20 including a photo sensor detects this and sends a signal to that effect to the controller 24.

When the controller 24 receives a signal from the sensor 20, the controller 24 causes the strobe 22 provided at a position facing the cameras 14 and 16 with the carrying means 12 interposed therebetween to emit light.
The strobe 22 is 10 even if a commercially available strobe is used.
It is possible to realize an extremely short light emission time of about μ seconds. The controller 24 controls to freeze the images captured by the cameras 14 and 16 in synchronization with the light emission of the strobe 22, and captures this image in the image memory inside the image processing device 28. The strobe 22 is provided on the camera 1 with the measuring object 10 interposed therebetween.
Since it is on the opposite side of 4 and 16, the measuring object 10 appears as a shadow in the captured image.

The captured image information is subjected to image processing, which will be described later, by the image processing device 28, and the size of the measuring object 10 is calculated by the personal computer 26 based on the image processing. If this measured dimension exceeds the preset allowable range, a signal to that effect (NG signal)
The warning lamp 30 is turned on to call the operator's attention, and the defective article removing mechanism 32 is operated to remove the defective track block from the transport means 12. The image memory may be provided inside the cameras 14, 16 and the controller 24. Further, as a warning means, a message to that effect may be displayed on the personal computer screen.

Next, with reference to FIG. 2, a method for measuring the dimensions of the measuring object 10 will be described. In the figure, 14a
And 16a are the visual fields of the two cameras 14 and 16, respectively, and their sizes are, for example, about 3 cm × 3 cm. L
₀ indicates the distance between two cameras with the left end of each field of view as the reference point. The distance L ₀ is originally a nominal value of the measurement object 10, that is, a cutout dimension when the measurement object 10 is cut out in a predetermined length. In response to this, the moving camera 16
Is adjusted so that the distance between the two cameras 14 and 16 matches L ₀ . The accuracy of the dimensional measurement depends on the alignment accuracy of the moving camera 16. Therefore, the moving table 18 has an error of 30μ per meter.
It is desirable to use a moving table of m or less. still,
Such a moving table is commercially available and can be easily obtained.

On the other hand, L is an individual measurement object 10
Is the actual length of. Since an error is unavoidable in cutting out the measurement target 10, the actual length L of the measurement target 10 does not necessarily match L ₀ .

In FIG. 2, L ₁ is the distance from the reference point (left end) of the visual field 16a to the right end of the measuring object 10, and L ₂ is the distance from the reference point of the visual field 14a to the left end of the measuring object 10. If L exactly matches L ₀ , L ₁ = L ₂ , but if L is different from L ₀ , these values are also different. The values of L ₁ and L ₂ are obtained by multiplying the number of pixels in each visual field by the resolution per pixel. This resolution is, for example, when the size of the visual fields 14a and 16a is 3 cm × 3 cm,
3 cm if the resolution of 16 and 16 is 500 x 500 pixels
÷ 500 = 60 μm. When the values of L ₁ and L ₂ are obtained, the length L of the measuring object 10 is obtained by the following formula. L = L ₀ + L ₁ − L ₂

As described above, the measuring object 10 moves on the conveying means 12 at a speed of about 15 meters per minute. Therefore, if the time taken to capture the image from the camera is, for example, 1/60 second, the measuring object 10 will be about 3.8 m in the meantime.
Move a distance of m. Then, the image captured by the camera shakes and an unclearness of about 3.8 mm occurs, and the end portion of the measuring object 10 becomes unclear. On the other hand, in the present embodiment, since the stroboscope 22 having the light emission time of 10 μs is used, the time interval of the images captured by the cameras 14 and 16 is limited to 10 μs. Measurement object 1 during this period
The distance that 0 moves is 2.5 μm. Although this distance causes a measurement error, it is practically negligible because it is extremely small, and therefore the edge of the measurement object 10 is sufficiently clear.

Next, the image processing of the image of the end portion of the measuring object 10 captured by the cameras 14 and 16 will be described. FIG. 3 is a diagram showing a procedure of processing an image of the upper left end of the measuring object 10 captured by the camera 14 of FIG. It should be noted that the image on the upper right end is image-processed in the same procedure.

FIG. 3A shows a normal image having 256 gradations, which is picked up by the camera 14. Here, it is assumed that the hatched portion is the upper left end of the measuring object 10 and the inside of the dotted line 40 next to it is a spot caused by noise. By applying a two-dimensional filter to such an image, FIG. 3B in which the contour portion is emphasized is obtained, and further binarization processing is performed at a preset binarization level to obtain FIG. 3C. Then, well-known processing such as expansion / contraction is applied to this binary image to remove noise, and a final binary image FIG. 3 (d) is obtained.

From the binary image of FIG. 3 (d) thus obtained, L ₁ and L ₂ of FIG. ₂ are obtained. To do so,
The problem is which part of the image in (d) is recognized as the end of the measuring object 10. This is because the line 42 indicating the end in FIG. 3D is not necessarily a straight line due to burrs or dents on the end of the measurement object 10, or due to an error in the shear angle at the time of cutting, or the like. Moreover, even if it is a straight line, it may not be perpendicular to the longitudinal direction of the measuring object 10. The length of H in FIG. 3D is 40 in terms of the number of pixels.
If it is 0, 400 edges will be obtained for one image, but this is too many, so
In this embodiment, one image has a width of 1 as shown in FIG.
No. 1 of 25 strip-shaped areas with 0 pixels and 10 pixels
Think about No.25.

Here, in the visual field 14a, as shown in FIG. 4, it is assumed that the edges of the object to be measured are obtained in the areas of No. 2 to No. 25 excluding No. 1. In the figure, the state in which the end portion of the No. 4 area is greatly different from the other areas is exaggeratedly shown. In the present embodiment, the following three methods are used to determine which position is recognized as the end from these data. (1) The second region from the top of the region where the edge is obtained (see FIG. 4).
Then, the end of No. 3 area) is the end of the whole. (2) A histogram is created using the data of the region where the edge is obtained, and the most frequent position is set as the edge of the whole. (3) The average value of all the data in the region where the edge is obtained is set as the entire edge.

In the above (1), the "second area from the top" means that the upper side of the measuring object 10 is not always horizontal in the uppermost area, so that the end portion may not be accurately specified. Because there is. (1) to (3) may be may be composed of a system by selecting any advance, what meet most circumstances actually performed tests in work site to choose each time .

When the lot of the caterpillar block is changed, that is, when another type of caterpillar block is the object to be measured, the dimension to be measured also changes. Therefore, it is necessary to move the moving camera 16 and readjust the distance between the fixed camera 14 and the moving camera 16. The length change in the x-axis direction is performed by the moving camera 16 as described above.
Can be done by moving.

Since the thickness of the measuring object 10, that is, the width of the measuring object 10 in the y-axis direction may change,
There is a mechanism (not shown) that moves the camera back and forth,
This keeps the distance between the cameras 14 and 16 and the measuring object 10 constant. If the distance between the camera and the object to be measured is kept constant, focus adjustment is unnecessary, and once the resolution per pixel is set, it is not necessary to change it. However, when a focus adjustment mechanism or a resolution resetting function is provided, these functions are complicated, but a mechanism for moving the camera back and forth is unnecessary or simple.

Further, in order to deal with the case where the lot of the caterpillar block is changed and the height of the measuring object is changed, the dimension measuring apparatus of this embodiment has six height level adjusting mechanisms (20 mm intervals). (Not shown) is provided. As described above, even when the heights are discretely set, it is sufficient that the end portion of the caterpillar block that is the measurement target is within the visual field of 30 mm × 30 mm, and it is not always necessary to set the accurate height. In this way, the discrete height levels that must be prepared in advance can be considerably smaller than the lot type. Therefore, the height setting mechanism can be simplified, which is advantageous in terms of cost.

For the movement of the cameras 14 and 16 as described above, the model number of each lot and the positions of the moving table on which the cameras are placed in the x-axis direction, the y-axis direction and the z-axis direction are stored in advance in the personal computer 26. Let's
It is desirable for the operator to enter the model number of a particular lot into a personal computer so that the cameras 14 and 16 are automatically repositioned to positions for measuring that lot. This significantly reduces the burden on the operator.

The present invention is not limited to the above embodiments, but various modifications can be made within the scope of the invention. For example, although the case where the measurement object is a caterpillar block has been described in the above-described embodiments, the present invention is not limited to this, and any measurement object whose dimension needs to be measured can be used. Further, in the above embodiment, the case where the two cameras are arranged so as to image from the side surface of the measurement target has been described, but the present invention is not limited to this, and for example, images from above the measurement target. It is also possible to have such an arrangement.

[0035]

As described above, according to the present invention,
Since the reference points of the two image pickup means are separated by a distance equal to the nominal value of the dimension to be measured of the measurement object, and the dimension is measured with this distance as a reference, when measuring the dimension with one image pickup means. In comparison, larger dimensions can be measured with less error, and the measurable length range is widened. Further, since the flashing means having an extremely short light emission time is used and the image of the measurement object is captured in synchronization with this light emission, the moving distance of the measurement object during this period is small enough to be ignored, and therefore, the edge portion of the measurement object is reduced. Therefore, it is possible to provide a dimension measuring device that makes it possible to accurately measure.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of a dimension measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a positional relationship between fields of view of two cameras and an object to be measured in one embodiment of the present invention.

FIG. 3 is a diagram showing a procedure of processing an image of an upper left end of a measurement target captured by a camera.

[Fig. 4] View No. 1 to No. 1 taken by the camera.
It is the figure which showed the method of forming the strip | belt-shaped area | region of 25 and recognizing the edge part of a measuring object.

5A and 5B are a schematic configuration diagram and a diagram showing a state of an output signal thereof when the dimension of an object to be measured is measured using one one-dimensional CCD camera.

[Explanation of symbols]

 10 Measuring Object (Caterpillar Block) 12 Conveying Means 14 Fixed Camera 16 Moving Camera 18 Moving Table 20 Sensor 22 Strobe 24 Controller 26 Personal Computer 28 Image Processing Device 30 Warning Light 32 Defective Product Exclusion Mechanism 50 Measuring Object 52 Background Illumination 54 Primary Original CCD camera

Claims (3)

[Claims] 1. Conveying means for conveying an object to be measured, first imaging means for imaging a front end portion of the measuring object in a conveying direction, and second imaging means for imaging a rear end portion in the conveying direction, The distance between the reference point of the first image pickup means and the reference point of the second image pickup means is a distance equal to the nominal value of the length from the front end to the rear end of the measurement object, Moving means for moving one or both of the image pickup means in parallel with the transport direction, the tip of the measurement target is within the field of view of the first image pickup means, and the rear end of the measurement target is the second image pickup means. A flash unit that emits light when entering the field of view of the unit, an image capturing unit that captures images captured by the first and second image capturing units in synchronization with the emission of the flash unit, and based on the captured image A calculator that calculates the dimension from the front end to the rear end of the measurement target Dimension measuring apparatus, characterized by the, the equipped. 2. The dimension measuring apparatus according to claim 1, further comprising means for adjusting a distance between the measurement object and the first and second imaging means according to a type of the measurement object. . 3. The first and second imaging means images the measurement object from a lateral direction, and all the upper end portions of the measurement object having a height within a certain range are first images. It has a plurality of height levels that are discretely set in advance so as to be included in the fields of view of the first and second imaging means, and the first and second imaging means of the first and second imaging means have a height corresponding to a change in the height of the measurement object. The dimensional measuring device according to claim 1 or 2, further comprising means for moving a vertical position between the plurality of height levels.