JP2000230814A - Shape measuring method using laser light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable highly precise shape measurements on objects to be measured of various surface shapes by changing the intensity of laser light to acquire each image and obtaining shape lines from their synthetic image. SOLUTION: A switch SW1 is turned to a weak side to reduce the light intensity (light quantity) of laser 2, and the surface of an object to be measured is irradiated with it to pick up the image of reflected light by a camera 5 to obtain an image X1 in a region in large reflected light. The image X1 is absent as an image in a region in little reflection and becomes intermittent lines. The intermittent lines are detected by a region determining part 31, and a switch SW2 is changed. In other words, the switch SW1 is changed to a strong side to obtain an image X2 of a multi-valued image even in a region in little reflected light by the reflected light of the light of the intensified laser 2. The region determining part 31 determines regions in which an image is present or absent from the image X1, and an image synthesizing part 12 interpolates and synthesizes the image X2 into the image X1 according to the results of the determination. A shape line extracted from the synthesized image by a line thinning device 8 is measured as the shape of the surface of the object to be measured by a shape measuring part 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light cutting method for irradiating a surface of an object to be measured with a laser beam, capturing an image of the reflected light with a camera, and measuring the surface shape of the object without contact. More particularly, the present invention relates to a shape measuring method capable of capturing a highly accurate reflected light image regardless of the surface state of an object to be measured.

[0002]

2. Description of the Related Art A non-contact three-dimensional shape measuring method for measuring a three-dimensional shape of an object without contacting the object is performed by irradiating a plate-like laser beam to the surface of the object to measure and reflecting an image of the reflected light. And processes the acquired reflected light image to measure the surface shape of the measured object. By repeating the above measurement while shifting the irradiation position of the plate-shaped laser light at a predetermined pitch, the three-dimensional shape of the object to be measured can be measured.

FIG. 1 is a principle diagram of a conventional non-contact three-dimensional shape measuring method. A plate-shaped laser slit light 3 emitted from a laser 2 is irradiated from above vertically onto the surface of the DUT 1 having the uneven shape shown in the figure. The laser slit light 3 is reflected or scattered on the surface of the DUT 1 to generate a laser light line 4 on the surface. This line 4
This shows the surface shape of the object to be measured, that is, the cross-sectional shape. Therefore, the cross-sectional shape can be measured in a contacted state by taking an image of the line 4 indicating the cross-sectional shape with the camera 5 installed diagonally above and using the image of the reflected light indicating the picked-up line 4.

As shown in FIG. 1, a laser 2 and a camera 5
Is integrally fixed by the holding member 6, stops at a plurality of positions, successively measures cross-sectional shapes at corresponding positions, and measures the three-dimensional shape of the surface of the DUT 1 from the plurality of cross-sectional shapes. Can be. The image of the line 4 captured by the camera 5 is converted into a multi-valued image by the multi-value conversion device 7 based on the luminance. Then, with respect to the multivalued image, the thinning device 8 generates an image in which the line 4 is thinned by a thinning process in which the position having the highest luminance is the position of the line 4. This thinned image is a shape line. Finally, shape measurement is performed according to this image,
The image and the measurement result are displayed on the display device 13.

FIG. 2 is a diagram showing an example of an image of a line 4 formed by a laser beam. In the examples of FIGS. 1 and 2, the surface of the DUT 1 is in a state where the intensity of the reflected light is weak at the convex portions of the unevenness, and the intensity of the reflected light is strong and spread at the concave portions. Therefore, the image 11 in FIG.
1a, a portion 11b having a slightly higher light intensity, and a portion 11c having a higher light intensity. In the protruding part, the image 11 is composed only of the weak light intensity region 11a, and in the concave part, the image 11 is composed of a part having a high light intensity to a part having a low light intensity.

[0006] As shown in a circle 12 in the figure, the image 11 is multi-valued in accordance with the luminance for each pixel, and the thinnest processing is performed to change the position having the highest luminance to the shape representative position (in the circle). The position represented by x) is obtained, and those shape representative positions are connected to obtain a thin line 10 indicated by a dashed line in FIG. The dashed line 10 is used as a thinned image as an image of a shape line representing the shape of the measured object.

[0007]

However, in the conventional method, since the image of the reflected light corresponding to the shape is captured by irradiating the laser light of a constant intensity, the color of the object to be measured can be improved.
Depending on the surface condition, the angle of the laser light or the surface with respect to the camera, the portion where the laser light 3 is strongly reflected on the surface and the reflected light enters the camera, and the portion where the reflected light is not so reflected or the reflected light does not enter the camera. Exists. For example, the black part of the DUT does not reflect much, the white part reflects much, the mirror surface has little reflection, and the rough surface scatters the reflected light and enters the camera. .

Therefore, when a laser beam having a constant intensity is irradiated, an area with a small amount of light is generated in the reflected light image so as to be hardly recognizable, or an area where the reflected light is too strong and the image becomes too thick occurs. I do. If the intensity of the laser beam is increased, an image that is too thick is obtained, and the accuracy of shape line detection is reduced due to thinning. If the intensity of the laser beam is decreased, the image itself disappears and the shape line cannot be detected. Further, in a portion where the reflected light is strong, a virtual image is generated due to the influence of secondary reflection or the like, which causes image noise and makes it impossible to detect a correct shape line.

As another problem, there is a case where an image cannot be obtained from a camera even if the intensity of the laser light is increased without substantially reflecting the irradiated laser light on the surface of the object to be measured. FIG. 3 shows that the object to be measured is a print roll 21.
It is a figure which shows the surface shape measurement in the case of. Printing roll 21 used for printing an alignment film on the substrate surface of a liquid crystal display panel
As shown in the enlarged view of the S portion, a plurality of frustum-shaped holes 22 are formed on the surface thereof. The volume of the hole 22 is related to the alignment film of the liquid crystal. By inspecting the volume of the hole 22, the quality of the print roll 21 is inspected.

In this case, a sheet-like laser beam 3 as shown in FIG. 1 is irradiated in a direction indicated by AA in the figure, and an image of the reflected light is captured by a camera, and the shape is formed by image processing. By obtaining an image indicating the above, the surface shape of the contacted object is measured. However, the hole 2 on the surface of the printing roll 21
2 is formed by driving a truncated cone-shaped tool into a nickel plating film (not shown) on the roll surface, so that a part of the surface of the hole becomes a mirror surface due to the so-called burnish effect. In such a mirror surface, scattering of laser light does not occur, and a shape line obtained from an image captured by a camera includes a part that is partially missing. For a mirror surface, even if the intensity of the laser light is increased, the reflected light is only concentrated and reflected in a certain direction,
It is difficult to capture with a camera.

An object of the present invention is to obtain an image of reflected light irrespective of the surface condition of an object to be measured,
It is an object of the present invention to provide a non-contact shape measurement method capable of accurately detecting the surface shape of an object to be measured.

Still another object of the present invention is to provide a shape measuring method capable of irradiating a laser beam and measuring a surface shape from an image of the reflected light even when the surface of the object to be measured hardly reflects the laser beam. May be provided.

[0013]

In order to achieve the above object, the present invention provides a method for measuring the same position on the surface of an object to be measured.
Irradiation is performed several times with the intensity of the laser light changed, and an image of the reflected light with respect to the laser light having the optimum intensity is captured according to the surface condition of the object to be measured. And measuring the surface shape. By doing so, highly accurate images can be obtained for all surfaces of the object to be measured, and the shapes of all surfaces can be accurately measured.

Further, in order to achieve the above object, the present invention provides a method for distributing organic or inorganic fine particles on the surface of an object to be measured when the surface of the object is a mirror surface with little scattering of laser beam reflection. The measurement is performed by increasing the scattering of the reflected light from the surface. For example, fine particles having a particle diameter of, for example, about 0.1 μm, such as a yellow toner used in electronic printing or the like, are uniformly dispersed on the surface, and the surface is irradiated with laser light. As a result, even if the surface is a mirror surface, the reflected light from the surface is appropriately scattered, so that an image having a sufficient amount of light can be captured from the camera.

[0015] To achieve the above object, the present invention provides:
In a shape measuring method of irradiating a laser beam to a surface of an object to measure an image of the reflected light with a camera and measuring a surface shape of the object to be measured, a laser beam having a first intensity is applied to the surface of the object to be measured. Obtaining a first image by the reflected light when illuminating a surface; and a second intensity greater than the first intensity in a region where the image of the reflected light is insufficient in the first image. Acquiring a second image based on the reflected light when the surface of the object is irradiated with the laser light, and interpolating the second image with the first image according to a synthesized image obtained by interpolating the second image. Measuring the surface shape of the object to be measured.

In order to achieve the above object, the present invention irradiates a laser beam to the surface of an object to be measured, captures an image of the reflected light with a camera, and measures the surface shape of the object to be measured. In the shape measuring method, ultrafine particles made of an organic or inorganic substance are dispersed on the surface of the object to be measured, and the surface of the object is irradiated with the laser light to capture an image of reflected light, and the image of the object to be measured is taken according to the image. It is characterized in that the surface shape is measured.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. However, such embodiments do not limit the technical scope of the present invention.

FIG. 4 is a configuration diagram of the shape measuring apparatus according to the first embodiment. The first embodiment is an example in which the intensity (light amount) of a laser beam is changed into two levels, “strong” and “weak”. As in the conventional example, a laser 2 that emits laser light, a camera 5 that captures an image of reflected light, a thinning device 8, a shape measuring device 9, and a display device 13 are provided. A switch SW1 for increasing or decreasing the intensity of the laser 2 and a switch SW2 for supplying an image signal captured by the camera to the two multi-level devices 7a and 7b are provided. Further, it has an image synthesizing unit 12 for synthesizing the image X2 when the light amount of the laser beam is large (high intensity) and the image X1 when the light amount is small (low intensity).

FIG. 5 is a flowchart of a shape measuring method according to the first embodiment. FIG. 6 is a diagram illustrating an image according to the first embodiment. In this example,
As shown in FIGS. 1 and 2, this is an example of measuring the surface shape of the DUT 1 having irregularities. The projection of the DUT 1 is, for example, mirror-finished and has less scattering of laser light reflection. Alternatively, the concave portion has a surface state in which the reflected light itself is small, and the concave portion has, for example, a mode in which laser light is appropriately reflected and scattered and the reflectance thereof is high.

As shown in the flow chart of FIG. 5, the switch SW1 is set to the "weak" side, the intensity (light amount) of the laser beam 3 is reduced, and the surface of the DUT 1 is irradiated with the reflected light. Is taken from the camera 5 and the first image X
1 is obtained (S1). This first image X1 is shown in FIG.
As shown in (1), the region R1, which has relatively large reflection,
In the regions R3 and R5, a relatively thin image having a constant luminance value is obtained. A region R2 with little reflection,
In R4, since the intensity of the reflected light is weak, the reflected light cannot be captured even in the minimum luminance range of the multi-level quantization device.
As shown in (1), no image exists. Therefore, the first image X1 acquired when the intensity of the laser beam is reduced becomes a discontinuous intermittent line. First image X
Whether or not 1 is an intermittent line is detected by the area determination unit 31, and the switches SW1 and SW2 are switched.

By switching the switch SW1 to the "strong" side,
The intensity (light amount) of the laser beam 3 is increased to irradiate the surface of the DUT 1 to obtain a second image X2 of the reflected light (S2). The second image X2 obtained at this time is shown in FIG.
As shown in (2), even in the regions R2 and R4, the luminance is equal to or higher than the minimum luminance range of the multi-level quantization device, and an image can be obtained in those regions. However, regions R1, R3, R5
In this case, the intensity (light amount) of the laser light is too high, and the multi-valued image is obtained as a thick image having a region from a high luminance region to a low luminance region.

The area determining section 31 calculates the first image X1
The regions R1, R3, and R5 where the image exists and the regions R2 and R4 where the image does not exist are determined. The result of this determination is the image synthesis unit 1
2 according to the result of the determination.
Then, the portions of the regions R1, R3, and R5 of the first image X1 are combined with the portions of the regions R2 and R4 of the second image X2.
That is, the image X2 in the regions R2 and R4 where no image exists is interpolated and synthesized with the first image X1. As shown in FIG. 6C, the combined image X1 + X2 is an image having an optimum luminance distribution or line width in all regions. Then, the synthesized image is supplied to the thinning device 8 as in the conventional case, and the shape line is extracted from the synthesized image. The extracted shape line is supplied to the shape measuring unit 9 and measured as the shape of the surface of the object to be measured, and the shape and the measurement result are displayed on the display device 13 (S3).

As described above, in the first embodiment, even when the surface of the object to be measured has a high reflectance area and a low reflectance area, the optimum laser light intensity can be obtained. As a result, it is possible to obtain a composite image having a narrow line width and an appropriate luminance distribution, so that a more accurate shape line can be obtained and an accurate measurement of the surface shape can be performed.

FIG. 7 is a flow chart of an improved shape measuring method according to the first embodiment. In this example, the same position on the object is irradiated with laser light while changing its intensity (light amount) from the first intensity to the n-th intensity so as to gradually increase the intensity, thereby obtaining respective images ( S10 to S13). Then, images corresponding to the respective intensities of the laser beams are appropriately combined.

More specifically, a first image corresponding to the first laser light intensity and a second image corresponding to the second laser light intensity in an area other than the first image acquisition area are synthesized,
Further, a third image corresponding to the third laser light intensity in an area other than the first and second image acquisition areas is interpolated and synthesized (S15). This combination is performed up to the n-th image corresponding to the n-th laser beam intensity or until the image can be obtained in all the regions (S16). As a result, an image corresponding to the laser light intensity that is optimal for the surface state of each region can be acquired and synthesized. Therefore, the shape line can be obtained with high accuracy by using the synthesized image,
Highly accurate shape measurement can be performed.

FIG. 8 is a diagram for explaining the second embodiment. FIG. 9 is a flowchart of a shape measuring method according to the second embodiment.

The second embodiment is directed to a printing roll 21 used for forming an alignment film of a liquid crystal display panel shown in the conventional example.
A description will be given by taking an example of the surface shape inspection of FIG. As shown in FIG. 8, a plate-like laser beam 3
And an image of the reflected light along the shape line formed on the surface is captured by the imaging camera 5 to obtain an image (S20). In this case, with respect to the shape of the surface shown in (a) in the figure, a part of the hole 22 on the surface is mirror-finished due to the Vanish effect, and the reflected light is not scattered and the camera 5 detects the reflected light. Can not. As a result, the obtained image has an image missing in a part of the area as shown in FIG.

If this image loss is detected (S2
1) The ultrafine particles are uniformly distributed on the surface of the object to be measured to make the surface state in which the laser light can be scattered (S22), and the image of the reflected light is obtained by irradiating the laser light again (S23). FIG.
As shown in the cross-sectional view of the DUT, the fine particles 27 are uniformly distributed on the surface of the DUT 21 so that the fine particles 27 are uniformly attached to the surface of the DUT 21, and the surface inside the hole 22 in the mirror state is formed. Can be changed to a state in which the reflected light of the laser light is scattered.

As a result, when the image of the reflected light is obtained by irradiating the laser light again, for example, a point group representing the contour of the missing shape line as shown in FIG. Will be added. Therefore, in the image processing device 8, the broken portion of the image is subjected to the interpolation processing to obtain a continuous image (S24). Finally, a thinning process is performed in the same manner as in the conventional example to extract a shape line composed of a thin line, and is used for shape measurement (S25).

The ultrafine particles to be distributed on the surface of the object to be measured are preferably, for example, organic fine particles of yellow toner used in electronic printing. The ultrafine particles of the organic substance for electronic printing have an average particle diameter of about 0.1 μm, and do not change the surface shape of the measured object. Such organic ultrafine particles for electronic printing are mixed with a volatile solvent such as alcohol or toluene or a petroleum-based dry solvent to sufficiently diffuse the fine particles. After that, the solvent in which the fine particles are diffused is dropped on the surface of the printing roll 21 and diffused by air pressure to volatilize or dry the solvent, whereby a uniform distribution of the fine particles can be formed on the surface of the measured object. . When laser light is applied to a surface where such fine particles are evenly distributed, the laser light is scattered by the ultrafine particles even if the surface is finished in a mirror-like shape, and a camera can capture any image. Become.

As the fine particles to be distributed on the surface of the object to be measured, in addition to the yellow toner, fine particles of an inorganic substance such as aluminum and fine particles of a ceramic such as alumina and silicon nitride can be used. However, an organic substance such as a yellow toner used for electronic printing is preferable to an inorganic substance because cleaning and removal can be performed relatively easily after measuring the shape of the measured object.

It is also possible to combine the above-described first embodiment and the second embodiment. That is, when there is an area where the image of the reflected light cannot be obtained on the surface of the object to be measured even by the shape measuring method shown in FIG. 7, fine particles are formed on the surface of the object to be measured according to the second embodiment. By irradiating the laser light with the highest intensity (light quantity) by distributing, it is possible to obtain an image of such an area. Therefore, by combining the first and second embodiments, a more flexible shape measuring method can be provided.

[0033]

As described above, according to the present invention, in the method of irradiating the surface of the object to be measured with laser light, acquiring an image of the reflected light, and obtaining the surface shape line by image processing, the intensity of the laser light ( Light amount) to acquire each image,
Since the shape line is obtained from the image obtained by synthesizing them, it is possible to perform more accurate shape measurement on the measured object having various surface states.

Further, even when the image of the reflected light cannot be captured when the surface of the object to be measured is a mirror surface, the image can be obtained by distributing the fine particles on the surface, and a wider range of the object to be measured can be obtained. It becomes possible to measure the surface shape of an object.

[Brief description of the drawings]

FIG. 1 is a principle diagram of a conventional non-contact three-dimensional shape measuring method.

FIG. 2 is a diagram showing an example of an image of a line 4 formed by a laser beam.

FIG. 3 is a diagram illustrating surface shape measurement when a measurement target is a printing roll 21;

FIG. 4 is a configuration diagram of a shape measuring device according to the first embodiment.

FIG. 5 is a flowchart of a shape measuring method according to the first embodiment.

FIG. 6 is a diagram illustrating an image according to the first embodiment.

FIG. 7 is a flowchart of a shape measuring method according to an improved example of the first embodiment.

FIG. 8 is a diagram for explaining a second embodiment.

FIG. 9 is a flowchart of a shape measuring method according to the second embodiment.

FIG. 10 is a cross-sectional view when fine particles are distributed on the surface of an object to be measured.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 object to be measured 2 laser 3 laser beam 4 image of shape line and reflected light 5 camera X1, X2 first and second images 27 fine particles

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Yoshihiro Nakayama Inventor 4-62 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Laboratory F-term (reference) 2F065 AA04 AA53 BB05 CC00 DD09 FF01 FF02 FF04 FF09 GG04 HH05 JJ03 JJ19 JJ26 NN02 QQ03 QQ31 QQ32 SS02 SS13

Claims (2)

[Claims] In a shape measuring method for irradiating a laser beam onto a surface of an object to be measured and capturing an image of the reflected light with a camera to measure the surface shape of the object to be measured, a laser beam having a first intensity is emitted. A step of acquiring a first image by the reflected light when irradiating the surface of the object to be measured; and in a region where the image of the reflected light is insufficient in the first image, the first intensity is higher than the first intensity. A step of acquiring a second image by the reflected light when the surface of the object to be measured is irradiated with a laser beam having a large second intensity; and interpolating the second image to the first image. Measuring the surface shape of the measured object according to the synthesized image. 2. A shape measuring method for irradiating a laser beam onto a surface of an object to be measured and capturing an image of the reflected light with a camera to measure the surface shape of the object to be measured. Or, a shape measuring method comprising: dispersing ultrafine particles made of an inorganic substance; irradiating the surface with the laser light to capture an image of the reflected light; and measuring the surface shape of the measured object according to the image. .