JP4956960B2 - 3D shape measuring apparatus and 3D shape measuring method - Google Patents

Description

  The present invention obtains three-dimensional shape data of a measurement object by irradiating a three-dimensional structure as a measurement object with laser light or the like and receiving reflected light from the measurement object at that time. The present invention relates to a shape measuring apparatus and a three-dimensional shape measuring method.

The measurement of the three-dimensional shape of the measurement target is performed by irradiating the measurement target with laser light and then receiving the reflected light of the measurement target with a light receiving sensor such as a CCD element. Measurement is generally performed.
For example, the three-dimensional shape of the measurement object can be measured by receiving light with a CCD element using a light cutting method.

  By the way, the measurement object is a tire, and the tread portion of the tire is used to check which position of the tire tread portion (position in the circumferential direction and width direction of the tire) is worn before and after use (running) of the tire. In addition, it is necessary to obtain a difference between measurement data before and after use of the tire. For this purpose, it is necessary to accurately align the position on the circumference of the tire tread portion and the position in the width direction of the tire.

As a positioning method when performing three-dimensional shape measurement, the following Patent Document 1 can be cited. In this document, in order to align the orientation of the plane of the measurement surface of the measurement object, three spheres are arranged on the plane so that the measurement object is sandwiched between them, and the sphere is measured. It is disclosed to measure with an object.
In this document, a measurement surface can be obtained from the center coordinates of spheres arranged in a plane, and it can be determined whether the measurement surface is inclined.

JP-A-11-344329

  However, in the toroidal shape measurement that has one side part-tread part-the other side part like a tire and has a rotating body shape, the tread part is seen from the front, and laser light is irradiated. Since it is necessary to irradiate the laser beam while seeing the part obliquely, when three spheres are arranged so as to sandwich the measurement object as disclosed in the above publication, at least one of the spheres is the measurement object. The laser beam cannot be measured behind the screen.

  Therefore, in order to solve the above problems, the present invention irradiates a three-dimensional structure, which is a measurement object, with a laser beam or the like, and receives the reflected light from the measurement object at that time, thereby measuring the measurement object. An object of the present invention is to provide a three-dimensional shape measuring apparatus and a three-dimensional shape measuring method capable of surely aligning and aligning a three-dimensional shape when acquiring three-dimensional shape data of an object.

In order to achieve the above object, the present invention has a rotating shaft fixedly three-dimensionally arranged in the measurement space, which is a measurement object rotatably arranged in the measurement space, and the rotation center axis. A three-dimensional shape measuring apparatus for measuring a three-dimensional shape of a three-dimensional structure of a rotating body that rotates with respect to the at least three spheres fixedly arranged three-dimensionally in the measurement space, In all the different combinations of the two spheres, the imaginary line segments when virtually connecting the centers of the two spheres do not intersect with the measurement object. Measuring the three-dimensional shape data of the reference solid object fixed in the vicinity and the reference solid object fixedly located in the measurement space, and the rotation target axis in the measurement space Around A measurement unit that measures and outputs the shape data of the three-dimensional shape of the rotating surface of the measurement object, and the reference data based on the shape data of the three-dimensional shape of the reference three-dimensional object output from the measurement unit. The position and orientation of the reference three-dimensional object in the measurement space determined by the at least three spheres of the three-dimensional object are defined so as to match the origin of the reference coordinate system and the direction of the coordinate axis predetermined in the measurement space. The coordinate transformation is calculated, and using the obtained coordinate transformation, the shape data of the three-dimensional shape of the measurement object output from the measurement unit is corrected, and the shape of the three-dimensional shape in the reference coordinate system is corrected. possess an arithmetic unit for converting the data, wherein the measurement unit, based on light-section method, the object to be measured to rotate moving the laser beam in the measurement space and A unit that simultaneously illuminates the sphere fixed in the measurement space, and simultaneously obtains and outputs shape data of each dimensional shape using an image signal generated from the reflected light at that time, surface provides a three-dimensional shape measurement device which is characterized that you have matte treatment is performed in order to suppress the specular reflection of the laser beam.

At this time, the arithmetic unit obtains the position coordinates of the centers of the at least three spheres, obtains the difference between the position coordinates and the target position coordinates of the centers of the at least three spheres, and the difference approaches zero. It is preferable that the coordinate transformation is defined as described above , and the shape data of the three-dimensional shape of the measurement object is transformed using this coordinate transformation.

The spheres preferably have different sizes.

Further, the term the rotating body direction in the lateral direction of the rotational center axis of the shape of the measurement object, the reference three-dimensional object is provided on either side of the lateral direction and the boundary of the rotary body shape It is preferable.

Furthermore, the present invention is a three-dimensional shape measuring method for measuring a three-dimensional shape of a three-dimensional structure having a rotating body that is a measurement object, and the three-dimensional structure having the rotating body shape that is the measurement object. The rotation center axis is fixedly three-dimensionally arranged in the measurement space, the measurement object is rotatably arranged in the measurement space, and at least three-dimensionally fixedly arranged in the measurement space. When a reference solid object including three spheres is virtually connected between the centers of the two spheres in all different combinations of the two spheres out of at least three spheres, the virtual line segment The reference three-dimensional object fixed in advance in the vicinity of the measurement object in the measurement space so as not to cross the measurement object and fixedly positioned in the measurement space when measuring a three-dimensional shape 3D shape And measuring the three-dimensional shape data of the rotating surface of the measurement object while rotating the measurement object around the rotation center axis in the measurement space, and measuring the reference The three-dimensional shape data of the three-dimensional object and the three-dimensional shape data of the measurement object are output, and the three-dimensional shape data of the reference three-dimensional object is output based on the output three-dimensional shape data of the reference three-dimensional object. Coordinate transformation that is defined by at least three spheres so that the position and orientation of the reference three-dimensional object in the measurement space matches the origin of the reference coordinate system and the orientation of the coordinate axes that are predetermined in the measurement space. Using the obtained coordinate transformation, the calculated three-dimensional shape data of the measurement object is corrected to obtain the three-dimensional shape data in the reference coordinate system. Is intended to conversion, the shape data of the three-dimensional shape of the measurement object and the spheres, based on light-section method, the measurement object rotates moving the laser beam in the measuring space and the measurement space In order to suppress the specular reflection of the laser beam, the surface of the sphere is obtained simultaneously by irradiating the fixed sphere at the same time and using the image signal generated from the reflected light at that time. There is provided a three-dimensional shape measuring method characterized in that a matte treatment is performed .

When modifying the shape data of a three-dimensional shape of the measurement object, the determined position coordinates of at least three center of the sphere, the difference between the position coordinates and the at least three spheres center of the target position coordinates seeking, defines the coordinate transformation as the difference approaches zero, it is preferable to convert the shape data of a three-dimensional shape of the measurement object by using the coordinate transformation.

  In the present invention, it is a three-dimensional object located in the measurement space, and at least three spheres are three-dimensionally arranged so that a virtual line segment when virtually connecting the centers of the spheres does not intersect the measurement object. Using a reference three-dimensional object fixed in the measurement space in the vicinity of the measurement object, three-dimensional shape data is output together with the measurement object located in the measurement space. For this reason, a coordinate transformation is used in which the position and orientation of the reference three-dimensional object in the measurement space determined by the sphere of the reference three-dimensional object are defined so as to match the origin of the reference coordinate system and the direction of the coordinate axes that are predetermined in the measurement space. Thus, the three-dimensional shape data of the measurement object can be corrected. Since the reference three-dimensional object outputs the three-dimensional shape data simultaneously with the measurement object, there is no case where the sphere is blocked by the measurement object and cannot be measured as in the past, and the direction and position of the three-dimensional shape of the measurement object. Matching can be ensured.

  Hereinafter, a three-dimensional shape measuring apparatus and a three-dimensional shape measuring method of the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a three-dimensional shape measuring apparatus according to the present invention.
A three-dimensional shape measuring apparatus 10 shown in FIG. 1 calculates three-dimensional shape data of a tire T when a three-dimensional shape of a pneumatic tire (hereinafter referred to as a tire) T is arranged according to a predetermined position and orientation. Recording and holding device.
The three-dimensional shape measuring apparatus 10 includes a reference three-dimensional object 20, a three-dimensional shape measuring unit 30, a computer 50, and a monitor 60 provided on one side in the width direction (left-right direction) of the tire T that is a three-dimensional structure. And is configured.

The reference three-dimensional object 20 is a three-dimensional object in which three spheres 21, 22, and 23 are three-dimensionally arranged in the measurement space and are fixed in the measurement space near the tire T. Further, the reference three-dimensional object 20 is arranged so that a virtual line segment when the centers of the spheres 21 and 22, the spheres 21 and 23, and the spheres 22 and 23 are virtually connected does not intersect the measurement object.
The reference three-dimensional object 20 is provided on the right side with the rotating tire T as a boundary when the direction of the rotation center axis of the rotating tire T is referred to as the left-right direction. Of course, it may be provided on the left side.
Specifically, the reference three-dimensional object 20 is configured such that the spheres 21, 22, and 23 are fixedly disposed in the measurement space via the rod 24 from the fixed support portion 70 that holds the shaft 60 that can rotate the tire T. Has been.
Note that the surfaces of the spheres 21, 22, and 23 are subjected to a matte treatment so as not to cause a specular reflection when irradiated with laser light described later.

The spheres 21, 22, and 23 are all spheres having the same size, but the spheres in the present invention may be different in size. This is because, in the three-dimensional shape data of a sphere described later, when specifying which sphere the data of a plurality of spheres can be identified by the size. Thereby, it is possible to automatically specify the sphere without making a mistake. Of course, the position of the sphere is fixed in the measurement space, and the approximate position of each sphere is known in advance. I can.
Regarding the arrangement of the spheres 21, 22, 23, any two of the spheres 21, 22, 23 need not be arranged on a plane perpendicular to the rotation center axis of the tire T. It is sufficient that at least the spheres 21, 22, and 23 are arranged three-dimensionally so as not to be arranged on a straight line.
In the present embodiment, the number of spheres is three, but may be three or more such as four or five.

The three-dimensional shape measurement unit 30 is a device that outputs three-dimensional shape data of the tire T and the reference three-dimensional object 20 located in the measurement space.
FIG. 2 is a diagram illustrating the configuration of the three-dimensional shape measurement unit 30.
The three-dimensional shape measurement unit 30 includes a CPU 31, a driver circuit 32, a laser diode 33, a galvano mirror 34, optical systems 35 and 36, a CCD element 37, an AD converter 38, a FIFO 39, a signal processor 40, and a frame memory 41. .
In the three-dimensional shape measurement unit 30, in response to a measurement start instruction from the computer 50, the CPU 31 generates a measurement start trigger signal and activates a clock generator (not shown) to generate a clock signal. This clock signal is supplied to the CCD element 37, AD converter 38, FIFO 39, and signal processor 40. On the other hand, by generating the trigger signal, the driver circuit 32 generates a laser light irradiation signal and supplies it to the laser diode 33. The laser diode 33 irradiates the laser beam by this, turns the laser beam into slit light, shakes the galvano mirror 34 that starts driving in accordance with the irradiation signal of the laser beam, and is irradiated through the optical system 35. A slit-shaped laser beam is scanned on the tire T and the reference three-dimensional object 20.

On the other hand, the reflected light of the laser beam focused through the optical system 36 is received by the CCD element 37, the generated image signal is converted into a digital signal by the AD converter 38, and the image signal is sequentially processed through the FIFO 39. This is supplied to the processor 40. The signal processor 40 incorporates a circuit that executes a known algorithm using a light cutting method, and is a part that generates three-dimensional shape data of the tire T and the reference three-dimensional object 20 from the supplied image signal. . This three-dimensional shape data is sequentially written in the frame memory 41 and is called up as necessary. A processing method for generating three-dimensional shape data from an image signal is an algorithm using a known light cutting method. The light cutting method is a method of irradiating a measuring object with slit light, photographing a band-like reflected light of the measuring object with a camera such as a CCD element, and obtaining three-dimensional shape data from an imaging position in the image. . The calculation at this time is performed based on the principle of triangulation.
The generated three-dimensional shape data of the tire T and the reference three-dimensional object 20 are supplied to the computer 50.
The three-dimensional shape measurement unit 30 is a device configured to perform the above-described operation.

  The computer 50 uses the three-dimensional shape data of the tire T and the reference three-dimensional object 20 so that the position and orientation of the reference three-dimensional object 20 matches the origin of the reference coordinate system and the direction of the coordinate axes that are predetermined in the measurement space. This is a part for defining the specified coordinate transformation and correcting the three-dimensional shape data of the tire T using this coordinate transformation. Such processing is performed by software processing that functions by starting a program on the computer 50.

  Specifically, first, the center position coordinates of the spheres 21, 22, and 23 are extracted from the supplied shape data. Since the positions of the spheres 21, 22, and 23 in the image are known in advance, the shape data of the surfaces of the spheres 21, 22, and 23 can be extracted, and the center position coordinates of each sphere are obtained from the extracted shape data.

  Next, as shown in FIG. 3 (a), the center positions of the spheres 21, 22, and 23 are set to the center positions of the predetermined virtual spheres 121, 122, and 123 as the target coordinates, and the center positions with respect to the target coordinates. Find the coordinate difference. The target coordinates at this time are determined so as to define the origin of the predetermined reference coordinate system and the direction of the coordinate axes, and by matching the center position coordinates of the spheres 21, 22, and 23 with the target coordinates, It is set to match the origin of the defined reference coordinate system and the direction of the coordinate axes.

  Next, using the obtained difference, an equation of coordinate transformation (movement transformation and rotation transformation) in which the center position coordinate of each sphere moves to a predetermined target coordinate is obtained. That is, a coordinate conversion formula is determined so that the difference approaches 0. Since each difference is represented by a three-dimensional vector as shown in FIG. 3B, there are a total of nine difference values. Using these nine values, the spheres 21, 22, and 23 A three-degree-of-freedom movement transformation and a two-degree-of-freedom rotational transformation are determined so that the virtual spheres 121, 122, 123 are moved and matched.

Using the coordinate conversion formula calculated in this way, the three-dimensional shape data of the tire T is coordinate-converted. Thereby, the rotation center axis of the tire T can be converted into a predetermined direction in the reference coordinate system.
Further, as shown in FIG. 4, the centroid G of the tire T obtained by using the coordinate-transformed three-dimensional shape data of the tire T is moved on the rotation center axis so that the position of the centroid G is previously set. The shape data of the tire T is corrected so as to come to a predetermined position.
Thus, three-dimensional shape data of the tire T processed so that the position and orientation of the tire T are aligned with the predetermined position and orientation are obtained.

  In this way, the reason why the position and orientation of the tire T are corrected so as to be aligned with the predetermined position and orientation is to prevent the position and orientation of the three-dimensional shape data of the tire T from being changed by measurement. In particular, in order to accurately know the wear form after use of the tire T, it is necessary to compare the shape of the tire T after wear with the shape of the tire T before use. For this reason, it is necessary to position and face two pieces of three-dimensional shape data acquired with a time of several weeks to several months with high accuracy.

FIG. 5A shows an example of a display screen displayed on the monitor 60 using a part of the shape data of the tire T obtained in this way. FIG. 5B shows the tread portion shape data obtained for the entire circumference of the tire T, and the amount of change (wear change) in the shape of the tread portion before and after use of the tire T is obtained. FIG. Of course, the position on the circumference of the tire T is also the result of a change in wear obtained by aligning the position on the same circumference before and after use and subtracting the three-dimensional shape data. According to this, it can be seen that uneven wear occurs in the left shoulder portion of the surface of the tread portion in FIG.
In the present invention, the three-dimensional shape of the tire T can be accurately determined by matching the position and orientation.

  In this way, the reference solid object 20 in which at least three spheres are three-dimensionally arranged and fixed in the vicinity of one side of the tire T is used, and the shape data of the tire T and the shape data of at least three or more spheres are obtained. Since they can be acquired at the same time, the shape data of the tire T can be converted so as to accurately match a predetermined position and orientation. In Patent Document 1, three spheres are arranged so as to surround a measurement object. For this reason, when measuring the three-dimensional shape of a three-dimensional structure such as the tire T, the three spheres cannot be measured by irradiating the three spheres with laser light.

Examples of the three-dimensional shape measurement unit 30 in the above embodiment include a non-contact three-dimensional digitizer VIVID9i (manufactured by Konica Minolta Co., Ltd.) using an optical cutting method. In the present invention, in addition to the light cutting method, a grating is projected from the projector onto the measurement object, and a deformed lattice image on the measurement object is photographed with a camera, and the grating pattern is photographed each time while shifting the grating pattern by a certain pitch, You may use the phase shift method etc. which acquire the data of the three-dimensional shape of a measurement object from a some image.
In the present invention, any method may be used as long as shape data representing the three-dimensional shape of the measurement object and the reference three-dimensional object can be arranged and measured in the same measurement space by the three-dimensional shape measurement unit.
The measurement object may be not only a tire but also a rotating body such as an automobile wheel or a turbine. In the case of a rotating body shape, it is preferable to perform coordinate conversion so that the rotation center axis is aligned with a preset direction. In this case, if a reference three-dimensional object is placed on one side of the measuring object having a rotating body shape and measured, Good.

  As described above, the three-dimensional shape measuring apparatus and the three-dimensional shape measuring method of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. Of course.

It is a schematic block diagram showing embodiment of the three-dimensional shape measuring apparatus in this invention. It is a figure explaining the structure of the three-dimensional shape measurement unit of the three-dimensional shape measuring apparatus shown in FIG. It is a figure explaining the coordinate transformation performed with the three-dimensional shape measuring apparatus shown in FIG. It is a figure explaining the correction of the position performed with the three-dimensional shape measuring apparatus shown in FIG. (A) is a figure which shows the example of the screen display of the three-dimensional shape data obtained with the three-dimensional shape measuring apparatus shown in FIG. 1, (b) was calculated | required using the three-dimensional shape measuring apparatus of this invention. It is a figure which shows the result of the partial wear of a tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 3D shape measuring apparatus 20 Reference | standard solid object 21, 22, 23 Sphere 30 3D shape measuring unit 50 Computer 60 Monitor

Claims (6)

A three-dimensional structure of a rotating body having a rotation axis fixedly arranged in three dimensions in the measurement space and rotating with respect to the rotation center axis, which is a measurement object arranged rotatably in the measurement space A three-dimensional shape measuring apparatus for measuring a three-dimensional shape of an object,
An imaginary line segment obtained by virtually connecting between the centers of the two spheres in all different combinations of the two spheres, and including at least three spheres fixedly arranged three-dimensionally in the measurement space A reference three-dimensional object fixed in the vicinity of the measurement object in the measurement space so that none of them intersect the measurement object;
The measurement object is measured while measuring the three-dimensional shape data of the reference three-dimensional object fixedly located in the measurement space and rotating the measurement object around the rotation center axis in the measurement space. A measurement unit for measuring and outputting the shape data of the three-dimensional shape of the rotating surface of
Based on the shape data of the three-dimensional shape of the reference three-dimensional object output from the measurement unit, the position and orientation of the reference three-dimensional object in the measurement space determined by the at least three spheres of the reference three-dimensional object are determined. , Calculating a coordinate transformation defined so as to match the origin and coordinate axis orientation of the reference coordinate system predetermined in the measurement space, and using the obtained coordinate transformation, the measurement output from the measurement unit by modifying the shape data of a three-dimensional shape of the object, it has a, a calculating unit which converts the shape data of a three-dimensional shape of the reference coordinate system,
The measurement unit irradiates the measurement object that rotates and moves in the measurement space and the sphere fixed in the measurement space at the same time based on the light cutting method, and generates from the reflected light at that time A unit that simultaneously obtains and outputs the shape data of each of the three-dimensional shapes using the image signals that have been obtained,
The surface of the sphere, three-dimensional shape measurement device which is characterized that you have matte treatment is performed in order to suppress the specular reflection of the laser beam.   The arithmetic unit obtains a position coordinate of the center of the at least three spheres, obtains a difference between the position coordinate and a target position coordinate of the center of the at least three spheres, so that the difference approaches 0 The three-dimensional shape measuring apparatus according to claim 1, wherein coordinate conversion is determined, and shape data of the three-dimensional shape of the measurement object is converted using the coordinate conversion. The three-dimensional shape measuring apparatus according to claim 1 or 2, wherein the spheres have different sizes. When the direction of the rotation center axis of the rotating object shape of the measurement object is referred to as a left-right direction, the reference three-dimensional object is provided on either side in the left-right direction with the rotating body shape as a boundary. Item 4. The three-dimensional shape measuring apparatus according to any one of Items 1 to 3 . A three-dimensional shape measurement method for measuring a three-dimensional shape of a three-dimensional structure of a rotating body that is a measurement object,
The rotation center axis of the three-dimensional structure of the rotating body that is the measurement object is three-dimensionally fixedly arranged in the measurement space, and the measurement object is rotatably arranged in the measurement space. ,
A reference three-dimensional object comprising at least three spheres fixedly arranged three-dimensionally in the measurement space is converted into a center of two spheres in all different combinations of two of the at least three spheres. Preliminarily fixed in the vicinity of the measurement object in the measurement space so that none of the virtual line segments when connecting the virtual space between the measurement object,
When measuring 3D shapes,
The measurement object is measured while measuring the three-dimensional shape data of the reference three-dimensional object fixedly located in the measurement space and rotating the measurement object around the rotation center axis in the measurement space. Measuring the shape data of the three-dimensional shape of the rotating surface, and outputting the measured three-dimensional shape data of the reference three-dimensional object and the three-dimensional shape data of the measurement object,
Based on the output three-dimensional shape data of the reference three-dimensional object, the position and orientation of the reference three-dimensional object in the measurement space determined by the at least three spheres of the reference three-dimensional object are the measurement space. The coordinate transformation defined so as to match the origin of the reference coordinate system and the coordinate axis defined in advance is calculated, and using the obtained coordinate transformation, the shape of the output three-dimensional shape of the measurement object The data is corrected and converted into shape data of a three-dimensional shape in the reference coordinate system ,
The shape data of the three-dimensional shape of the measurement object and the sphere is based on the measurement object that rotates and moves laser light in the measurement space and the sphere fixed in the measurement space based on a light cutting method. Irradiated at the same time and obtained simultaneously using the image signal generated from the reflected light at that time,
The method of measuring a three-dimensional shape , wherein the surface of the sphere has been subjected to a matte treatment to suppress specular reflection of the laser beam . When correcting the shape data of the three-dimensional shape of the measurement object, the position coordinates of the centers of the at least three spheres are obtained, and the difference between the position coordinates and the target position coordinates of the centers of the at least three spheres is calculated. 6. The three-dimensional shape measurement method according to claim 5, wherein the coordinate transformation is determined so that the difference approaches 0, and shape data of the three-dimensional shape of the measurement object is transformed using the coordinate transformation.

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