KR920010549B1 - 3D curved shape measuring method and device - Google Patents

Abstract

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Description

3D curved shape measuring method and device

1 is an explanatory diagram showing the measuring principle of the present invention.

2 is a conceptual diagram of a conventional light cutting method.

3A and 3B are explanatory diagrams showing a change in measurement accuracy due to a slope angle of a conventional light cutting method.

4 is a block diagram of a three-dimensional shape measuring apparatus according to an embodiment of the present invention.

5 is an explanatory diagram showing a measurement example of a slope shape.

6 is a block diagram showing details of the image combining circuit of FIG.

7 is a block diagram showing another example of a shape calculation circuit.

* Explanation of symbols for the main parts of the drawings

1: Reference plane 2: Measured object

3: slit light source 4: rotating mirror

5: power controller 6: motor

7: Rotation angle sensor 8: TV camera

9: Shape measuring device 10: Shape calculating circuit

11: Flood angle calculation circuit 12: Sequential controller

13: Image synthesis computation circuit 14: Height computation circuit

15: 3D shape memory 18: Maximum luminance image calculation unit

19: synthetic image calculation unit 21: memory address generation circuit

20: synchronous circuit 22: output control circuit

23: Maximum luminance image memory 24: A / D conversion circuit

27: switch circuit 28: synthetic image memory

The present invention relates to a method and apparatus for non-contact measurement of the shape of a three-dimensional curved surface.

Since the measurement of the three-dimensional curved shape can be considered in a wide range of applications such as three-dimensional CAD input, robot vision, or human body shape measurement for medical and garment design, various techniques have been proposed in the past.

Among them, a method known in general as a method of cutting light is described, for example, on pages 398 and 399 of the "Image Processing Guide (Shogoodo Shokai Co., Ltd.)" issued in Japan, as shown in FIG. When the slit light 53 from the slit light source 52 is irradiated to the object to be measured, the beam pattern of light formed on the object surface is observed when it is observed from a direction different from the irradiation direction. The method which pays attention to the phenomenon which corresponds to the cross-sectional shape in the slit light irradiation position of the measuring object 51 is the method widely used conventionally because of its simplicity, noncontact, and quantitative property.

In measuring the shape of the three-dimensional free curved surface using the cutting method of the present light, in FIG. 2, the slit light 53 is moved in the direction of the arrow 54 using a rotation mirror 58 or the like, and the light beam pattern Is observed by the television camera 55, and as a result of processing the obtained video signal, a light cut line (shape of a light pattern of light) in the screen is extracted 56 and a curved shape is constructed 57 by reconstructing it. .

As an optical system, a light spot scan is used instead of the slit light source 52 as a light source, and a high speed as known as a PSD (Position Sensitive Detector) sensor, instead of the television camera 55, as the imaging system. There is also a method of using the light spot position detection device of the present invention, but the basic principle is the same as that of FIG.

Although the above-described light cutting method has various advantages, the process of extracting the light cutting line in the screen is indispensable for detecting and specifying each point on the measured object. As shown, a problem occurs in measurement accuracy or reliability.

(1) Inferiority of the measured fineness and spatial resolution by the shape of the object to be measured:

In the light cutting method, as shown in FIG. 3A, the width of the light beam pattern on the surface of the object when the surface of the object to be measured 51 is at an angle close to the right angle with respect to the optical axis of the slit light 53. Since (w) is narrow, highly accurate measurement is possible. However, as shown in Fig. 3 (b), when the object to be measured becomes a slope at an angle parallel to the optical axis of the slit light 53, the width w of the light beam pattern on the object surface is widened and cut. As the uncertainty of the position at the time of line extraction increases, the precision deteriorates, and the amount of movement of the light beam pattern on the surface of the object when the slit light source 53 is moved increases, whereby the spatial measurement simultaneously degrades the resolution. do.

(2) Degradation of measurement reliability due to the surface reflectance of the object to be measured: In the light cutting method, it is assumed that the light beam pattern is sufficiently brighter than the surroundings in the process of extracting the light cutting lines in the screen. If the slope angle of the surface is acute on the optical axis of the slit light, and the reflected light intensity is low, there are some disadvantages in extracting the light cutting line, or a wrong detection of the completely different point occurs. Such a phenomenon occurs even when background light other than slit light exists at the time of measurement, and in either case, there is a limitation on the reliability of the measurement and a limitation on the application target measurement environment.

As such, the light cutting method has many application constraints such as shape, surface state, or measurement environment of the object to be measured due to some measurement problems caused by the light cutting line extraction process. Compared with its superiority, its use is limited and it has not been assembled until it has been widely used as a three-dimensional curved measuring device widely used.

The present invention has been made to solve the above-mentioned problems of the light cutting method, and a new method of coding the surface to be measured at a slit light transmission angle using slit light as a medium while using an optical system similar to the light cutting method. As a result, the object of the present invention is to obtain a method and apparatus for measuring a three-dimensional curved shape according to a new measuring principle that does not require any light cutting line extraction process.

The method for measuring a three-dimensional curved shape according to the present invention includes the steps of rotating scanning linear slit light over the entire surface of the object to be measured, measuring the slit light transmission angle, and imaging the surface to be measured. A process of synthesizing an image in which the slit light transmission angle at which the slit light passes or the corresponding value is the pixel value at each position of the target object surface corresponding to each pixel in the video signal screen; And further has a step of measuring a three-dimensional curved shape of the object to be measured in accordance with the above-described synthetic image.

Moreover, the three-dimensional curved shape measuring apparatus which concerns on this invention is a slit light transmitting means which transmits linear slit light to the surface to-be-measured, and a slit light transmitting means in the plane of a slit beam, and the straight line parallel to a reference plane with a rotation axis. Rotational scanning means for scanning the slit light over the entire surface of the surface to be measured, slit light transmission angle measuring means for measuring the light transmission angle of the slit light, and a surface to be measured different from the slit light transmission. It has a television camera that picks up from the direction. Furthermore, by processing the bidet signal from this television camera, the slit light angle measuring means measures the projection angle at which the slit light passes through the point at each position on the surface under measurement corresponding to each pixel in the screen. Image synthesizing means for synthesizing an image having an angle or an equivalent value thereof as the value of the pixel, and image computing means for calculating a three-dimensional curved shape of the object to be measured by arithmetic processing based on the synthesized image; have. The television camera is arranged to capture an object to be measured from a direction perpendicular to the reference plane.

In addition, the three-dimensional free-curved measuring device according to the present invention has a slit light transmission angle composite image θ (x, y) ((x obtained when the slit light is scanned on the surface to be measured. , y) is the horizontal range (x ₀ ) and the vertical displacement (z ₀ ) of the slit light center of rotation axis relative to the origin of the reference plane based on the three-dimensional shape f (x, y) of the surface to be measured use with,

The section image calculating means is provided on the basis of the expression f (x, y) = z _0- (x ₀ -x) tanθ (x, y).

In addition, the three-dimensional curved shape measuring device according to the present invention is characterized in that the slit light transmission angle composite image θ (x, y) obtained by the image synthesizing means when the slit light is scanned on the surface to be measured and the reference plane Rotating center of the slit light with respect to the origin of the reference plane based on the three-dimensional shape f (x, y) of the surface to be measured based on the synthesized image θ ₀ (x, y) obtained when the slit light is scanned. Using the horizontal displacement of the axis (x ₀ )

and image calculating means obtained on the basis of the formula f (x, y) = {tanθ ₀ (x, y) -tanθ (x, y)} (x ₀ -x). In addition, the three-dimensional free-form surface measuring apparatus according to the present invention has a slit light transmission angle composite image θ (x, y) obtained by image combining means when scanning slit light on the surface to be measured, and a reference plane. The three-dimensional shape f (x, y) of the surface to be measured is the origin of the reference plane based on the synthesized image θ ₀ (x, y) or the like obtained when the slit light is scanned with respect to. Using the vertical displacement (z ₀ ) of the central axis of rotation of the slit light relative to

An image calculating means obtained according to the equation is provided.

Further, the three-dimensional curved shape measuring device according to the present invention has a slit light transmission angle composite image θ (x, y) obtained by the image synthesizing means when scanning slit light on the surface to be measured and the reference plane. When the slit light is scanned, the synthesized image θ ₀ (x, y) obtained by the image synthesizing means, and furthermore, the distance d parallel to the reference plane (the side closer to the television + and the side falling −). Three-dimensional shape f (x, y) of the measurement target surface using a synthesized image θ ₁ (x, y) obtained by the image synthesizing means when scanning the slit light with respect to the second reference plane separated by of

An image calculating means obtained according to the equation is provided.

In the present invention, the moment when the slit light passes through the position of the object under measurement corresponding to each pixel in the screen by imaging with a television camera a state where the linear reflection pattern of the slit light moves on the object under measurement. A slit light transmission angle synthesized image having a slit light transmission angle of as the value of the pixel is created.

Then, the three-dimensional shape of the object to be measured is measured according to the composite image. Similarly with respect to the reference plane or the second reference plane, a synthetic image is created, and the three-dimensional shape of the object to be measured is measured using these synthetic images. In this case, some or all of the measurement constants are omitted.

Prior to the description of the embodiments of the present invention, the measuring principle of the present invention is first conceptually described according to FIG.

As shown in FIG. 1, the slit light 3a which is widened from the obliquely upward to the ground perpendicularly to the ground is transmitted to the surface of the measurement target object 2 placed on the reference plane 1, and the slit light 3a is, for example, The image is captured using the television camera 8, for example, directly from above the measurement target 2 while moving in the horizontal direction of the ground using the rotation meter 4. At this time, on the monitor television 8a connected to the television camera 8, the linear reflection pattern of the slit light on the object surface moves in the horizontal direction of the screen.

As described above, the linear image of the linear reflection pattern of the slit light 3a reflects the uneven information on the surface of the object. The three-dimensional shape of the object to be measured has been measured by extracting and reconstructing it.

In the present invention, each pixel in the screen corresponds to each pixel on the basis of the video signal output from the television camera 8 in which the linear reflection pattern of the slit light 3a moves on the object surface. An image is obtained in which the slit light transmission angle at the instant when the slit light passes through the position of the object surface is set to the pixel value.

The image thus synthesized is an image corresponding to an elevation angle when the value in each image looks at the center of rotation of the slit light of the rotation meter 4 from the position of the object surface corresponding to the pixel. Therefore, when the composite image is expressed as θ (x, y) using the coordinate system (x, y) of the corresponding object surface, the profile f (x, y) of the object surface is a simple element based on FIG. Based on the calculation of the load, it can be obtained from the following equation.

및

를 생략하는 방법이다. 즉, 기준면(1)에 있어서의 합성화상 θ₀(x,y)는 (1)식에서 f(x,y)이라고 놓음에 따라Now, as an application example of the present measuring principle, the following measuring method can also be easily considered. First, as the first application example, the above-described measurement is performed on the reference plane 1, and thus a parameter is obtained by using a synthesized image that can be obtained.

And

This is how to omit. That is, the composite image θ ₀ (x, y) on the reference plane 1 is set to f (x, y) in the formula (1).

Therefore, by eliminating z ₀ or x ₀ from Eq. (1), the object plane profile f (x, y) can be constructed in the following equation.

Further, as a second application example, the parameters x ₀ and z ₀ are obtained by using a synthesized image obtained by performing the above measurements with respect to two reference planes f (x, y) = 0 and f (x, y) = d. This is how to omit both sides.

That is, as the composite image θ ₁ (x, y) on the second reference plane is set to f (x, y) = d in the formula (1), the following equation can be obtained.

Therefore, by substituting the relationship between equations (2) and (5) into equation (1), x ₀ and z ₀ are eliminated, and f (x, y) is obtained by the following equation.

Now, in the present invention, the surface to be measured is coded by the slit light transmission angle, but as the means, it is not necessary to measure the slit light transmission angle directly, for example, the rotation angle of the rotation mirror or the same value as that means. Under the premise that the rotational angular velocity of the mirror is constant, the surface to be measured may be coded once, such as after the scanning start of the rotational mirror, and then converted into a slit light transmission angle by arithmetic processing. Furthermore, as seen from equations (1)-(6), the composite image θ (x, y) coded at the slit light transmission angle is tangent to tantang (x, y) in all subsequent shape operations. Since it is used in the form of y), instead of the slit light transmission angle at the time of initial image synthesis, the slit light transmission angle may be coded by tangent.

Next, an embodiment of the present invention will be described with reference to FIGS.

4 is a configuration diagram of the three-dimensional shape measuring apparatus according to the above-described embodiment. The object to be measured (2) is placed on the reference surface (1) on which the measurement is to be made. The slit light emitted from the slit light source 3 is reflected by the rotation mirror 4 and is projected obliquely upward on the object to be measured 2. The rotating mirror 4 is driven by the motor 6 controlled by the power controller 5 so that the slit light 3a scans the measurement target 2 on the reference plane 1 over the entire surface. At this time, the position (x ₀ , z ₀ ) with respect to the reference plane 1 on the rotation center side of the rotation mirror 4 shall be measured accurately. In addition, the angle with respect to the reference surface 1 of the rotation mirror 4 is configured to be detected by the rotation angle sensor 7 attached in conjunction with the axis of the motor 6, via the power controller (5). It is input to the shape measuring apparatus 8, and the slit light transmission angle (theta) of the visual angle with respect to the to-be-measured object 2 can be calculated. On the other hand, the surface of the object to be measured 2 is input to the shape measuring apparatus 9 with a video signal obtained by imaging with the television camera 8 arranged so that the optical axis is orthogonal to the reference plane 1. The shape measuring device 9 is divided into instructions and shape calculation circuits for the shape calculation circuit 10, the rotation angle sensor 11, and the power controller 5 as image calculation means for performing shape calculation by image synthesis. And a sequential controller 11 which performs arithmetic timing control with respect to 10). In the shape measurement, the shape measuring device 9 drives the motor 6 via the sequential controller 11 in accordance with a star art signal supplied from the outside to set the rotation mirror 4 to an initial position. . Then, rotation of the rotating mirror 4 is started, and scanning by the slit light 3a is started.

The shape calculating circuit 10 has an image synthesizing circuit 13 to be described later on its input section, and simultaneously processes the bidet signal input from the television camera 8 at the same time as the scanning of the slit light source 3 starts. During each scanning period of the slit light 3a, an image synthesis operation for reading out the light transmission angle at the moment when the slit light passes through the pixel for each pixel in the screen from the light transmission angle calculating circuit 11 and setting it as the value of the pixel. do. After completion of the composite image θ (x, y) calculation, the shape calculation circuit 10 uses the height calculation circuit 14 according to the instruction of the sequential controller 12, and according to the formula (1), the height profile f (x) and height), and the height profile data in which the movement data is stored in the three-dimensional shape memory 15 is appropriately transferred to the calculator and the CAD system in accordance with instructions from the upper calculator and the CAD system. In this embodiment, for example, as shown in FIG. 5, when measured with respect to the measurement target object 2 having a slope close to the transmission angle of the slit light, the slope of the slope is very close to the transmission angle of the slit light. When it comes to the position indicated by "1" in this figure, the entire slope becomes equally bright. However, if the angular coded composite image is calculated according to the equation (1), the measurement result can be obtained as shown. From this fact, it can be seen that a sufficiently good resolution can be obtained even for a shape having a surface close to the angle of the slit light.

Conventionally, it is difficult to extract light cutting lines from such an image as described above. When applying a light cutting method to such a slope, measurement accuracy and spatial resolution could not be expected together. In this embodiment, such a slope can also be measured at the measurement accuracy and spatial resolution of the non-width and sampling pitch of the slit light, and a sufficiently high resolution can be obtained even for a shape having a surface approximating the angle of the slit light.

6 is a configuration diagram showing an example of the image synthesis circuit 12 that is a component of the shape measuring device 9.

The image synthesizing circuit 12 processes a bidet signal input from the television camera 8 and calculates the luminance at the brightest moment for each pixel, and the maximum luminance image calculating unit 18 and the maximum luminance in time with each pixel. Is composed of a compound composition calculating unit 19 for performing an image synthesis operation in which the slit light transmission angle θ is the value of the pixel. The synchronization circuit 20 and the memory address generation circuit 21) and an output control circuit 22.

The maximum luminance calculating section 18 A / D outputs a video signal in accordance with a timing signal output from the synchronization circuit 20 centering on the maximum luminance image memory 23, which is a buffer memory for maximum luminance image operation. A / D conversion circuit 24 for converting and digitizing the maximum luminance image memory 25 for controlling the reading and writing of the address data of the maximum luminance image memory specified by the memory address generation circuit 21. Furthermore, it is comprised by the comparison circuit 26 and the switch circuit 27 which select and output the larger value by comparing the value of the corresponding pixel of the image input from a television camera with the image of a maximum luminance memory.

On the other hand, the synthesized image calculating unit 19 is composed mainly of the synthesized image memory 28 which stores the result of the synthesized image calculation, and is in accordance with the output signal of the comparison circuit 26 in the maximum luminance image calculating unit 18. Synthesized image memory having a function of writing the slit light transmission angle? Into the synthesized image memory 28 when the signal level inputted from? Is greater than the address appeal value of the corresponding maximum luminance image memory 23; The control circuit 29 is provided.

This circuit uses the A / D conversion circuit 24 to output a video signal input from a television camera by star art with the maximum luminance image memory 13 and the composite image memory 28 cleared at the start of computation. By comparing the value of the video signal with the value of the pixel of the maximum luminance image memory 13 corresponding to the position of the pixel while digitizing the image signal, the pixel of the maximum luminance image memory 13 only when the value of the video signal is larger. Has the function of updating the value of to the value of the video signal and writing the slit light transmission angle? At the corresponding pixel in the composite image.

In this way, the constant image described above is generated in the synthesized image memory 28 at the time of the time indicated by the operation control signal from the outside and as a result of the above calculation. The synthesized image thus calculated is transferred to the next calculation circuit via the output control circuit 22.

By the way, in the above embodiment, the equation (1) is calculated by the height calculation circuit 14, but as described above, in order to increase the calculation precision, z ₀ or x ₀ of the equation (1) can be omitted. . In this case, also for the reference plane 1, a synthesized image is obtained in the same manner as the object to be measured, and the synthesized image as the subject is measured as θ ₀ (x, y) as shown in FIG. θ (x, y) and the synthesized image of the reference plane θ ₀ (x, y) are stored in the object plane synthesizing memory 30 and the reference plane synthesizing memory 31, respectively, and then as the height computation circuit 14a (3). The three-dimensional shape is obtained by calculating the equation or equation (4). In addition, since the composite image of the reference plane 1 and the second reference plane may be created once, the first synthetic image created during the second and subsequent measurements may be used as it is. In addition, since the composite image of the reference plane 1 and the second reference plane has a simple configuration, an arithmetic function is added to the shape calculation circuit 10, and the virtual reference plane is calculated by equations (2) and (5). The composite image may be created and stored in the memories 31 and 32, respectively.

As described above, according to the present invention, the slit light transmission angle is obtained to obtain a three-dimensional shape according to the composite image of the coding target to be measured while using the same optical system as the light cutting method. Even when the slope has a shape close to the angle, the slope can be measured at the measurement accuracy and spatial resolution of the slit light beam and the sampling pitch of the slit light. A sufficiently high resolution is also obtained for the excited shape.

In addition, according to the present invention, the linear reflection pattern of the slit light moves on the measurement target surface with a television camera, and the slit light passes through the position of the object surface corresponding to the pixel for each pixel in the drawing. At one moment, the image synthesis operation is performed using the slit light transmission angle as the pixel value. However, the condition for obtaining the shape information accurately by establishing the image synthesis operation is that the brightness of each position on the object surface corresponding to each pixel is different. The only condition is that the slit light is maximized at the moment it passes through the position.

Thus, staining of the spatial surface reflectivity of the subject under test does not only affect the measurement. Even if there is light in the background, if the amount of light is constant in time and the brightness of the TV camera signal is not saturated enough, the brightness of each point on the surface of the object is also corrected at the moment when the slit light passes. It is possible to measure the surface reflectivity of and without being affected by background and light.

Furthermore, according to the present invention, since the composite image or the second composite image of the reference plane is prepared in the same manner as in the case of the object to be measured and the three-dimensional shape of the object to be measured is obtained using these composite images, the height profile is calculated. In this case, a part of the measurement constant can be omitted, so that the measurement accuracy can be increased.

Claims (7)

A process of rotationally scanning linear slit light over the entire surface of the object to be measured, a process of measuring the slit light transmission angle, and a target corresponding to each pixel in the screen of the video signal obtained by activating the surface to be measured A process of synthesizing an image having the slit light transmission angle at the instant when the slit light passes through the point at each point on the surface to be measured or a value corresponding thereto as the pixel value and the above-described synthesized image. A three-dimensional curved shape measuring method comprising the step of measuring a three-dimensional curved shape. A slit light transmitting means for transmitting a linear slit light to the surface to be measured, and a slit light transmitting means for rotating the slit light transmitting means using a straight line in which the slit light is in-plane and parallel to the reference plane, The slit light rotating scanning means for scanning, the slit light angle measuring means for measuring the projection angle of the slit light, the slit light transmitting means for imaging the surface to be measured are a television camera for imaging in different directions, and a video signal from the television camera. Is processed to read the transmission angle from the slit light angle measuring means at each position of the target object surface corresponding to each pixel in the screen, and the angle or the corresponding value is read. Image synthesizing means for synthesizing an image having a pixel value, and a three-dimensional curved shape to be measured by performing arithmetic processing on the basis of the synthesized image Measuring a three-dimensional measurement apparatus of the curved surface, characterized in that with an image operation means for. The apparatus for measuring a three-dimensional curved shape according to claim 2, wherein the television camera captures an object to be measured from a direction perpendicular to the reference plane. The slit light transmission angle composite image θ (x, y), ((x, y) according to claim 2, wherein the slit light transmission angle obtained by the image synthesizing means when the slit light is scanned on the surface to be measured is the reference plane (1). ), The surface to be measured is a three-dimensional shape f (x, y) and the axis of rotation of the slit light center relative to the origin of the reference plane (1) is a horizontal displacement (x ₀ ) and a vertical displacement (z ₀ ). And an image calculating means obtained according to the formula f (x, y) = z _0- (x ₀ -x) tanθ (x, y). The slit light transmission angle obtained by the image synthesizing means when the slit light is scanned on the surface to be measured, and when the slit is scanned with respect to the composite image θ (x, y) and the reference plane (1). On the basis of the synthesized image θ ₀ (x, y) obtained by the image synthesizing means, the horizontal of the slit-light rotational center axis with respect to the origin of the reference plane 1 based on the three-dimensional shape f (x, y) of the surface to be measured. And an image calculating means calculated using the displacement (x ₀ ) according to the formula (x, y) = {tanθ ₀ (x, y) -tanθ (x, y)} (x ₀ -x). Three-dimensional curved shape measuring device. The slit light transmission angle composite image θ (x, y) obtained by the image synthesizing means when the slit light is scanned on the surface to be measured, and when the slit light is scanned on the reference plane. On the basis of the synthesized image θ ₀ (x, y) obtained by the image synthesizing means, the three-dimensional shape f (x, y) of the surface to be measured is perpendicular to the origin of the slit light rotational axis relative to the origin of the reference plane (1). Using the displacement z ₀ ,

An apparatus for measuring a three-dimensional curved shape comprising an image calculating means obtained according to the equation. The slit light is scanned with respect to the slit light transmission angle composite image θ (x, y) and the reference plane (1) obtained when the slit light is scanned on the surface to be measured. And the distance d in parallel with the reference image 1 and the distance d (a side closer to the television camera, and a side farther away) from the composite image θ ₀ (x, y) obtained by the image synthesizing means. Using the synthesized image θ ₁ (x, y) obtained by the image synthesizing means when scanning the slit light with respect to the separated second reference plane, the three-dimensional shape f (x, y) of the measurement target surface is obtained.

An apparatus for measuring a three-dimensional curved shape, comprising an image calculating means obtained according to the equation.

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