JPH10332349A - Three-dimensional shape measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-dimensional shape measuring method by which precise three-dimensional shape data can be obtained in a single measurement without performing any preparatory measurement. SOLUTION: When a position output is taken from an optical displacement sensor 5, an X-axis table 1, a Y-axis table 2, and a C-axis rotational table 3, by which a horizontal position and a rotational position of an object 4 to be measured are positioned, are controlled so that a relative distance between the optical displacement sensor 5 and a measuring point on the object 4 to be measured is kept constant and so that a face including a light projection axis 13 and a light receiving axis 14 of the optical displacement sensor 5 orthogonally crosses a face including the light projection axis 13 and a normal vector for a face in the vicinity of the measuring point. In addition, as a Z-axis table 6 positioning the vertical position of the optical displacement sensor 5 is controlled, a proper relative positional relationship between the object 4 to be measured and the optical displacement sensor 5 is predicted on the basis of the data of an already measured measuring point in the vicinity of the measuring point, and then, controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a three-dimensional shape of an object to be measured by an optical displacement sensor, and more particularly to a method of measuring a three-dimensional object having a large surface undulation such as a dental prosthesis model. The present invention relates to a method for measuring a shape with high accuracy.

[0002]

2. Description of the Related Art As an apparatus for measuring a three-dimensional shape of an object to be measured, a light projecting unit for irradiating a laser beam to the object to be measured,
2. Description of the Related Art An optical displacement sensor including a light receiving unit that receives reflected light from an object to be measured has been conventionally used. This utilizes the fact that the position of the reflected light incident on the light receiving unit changes according to the position of the measurement point on the object to be measured, and obtains the distance to the measurement point based on the principle of triangulation.

[0003] Since this optical displacement sensor is not in contact with the object to be measured, it can perform relatively high-accuracy measurement without considering deformation of the object to be measured or correction of the contact. Although there is an advantage, there is also a problem that an unmeasurable portion occurs depending on the inclination of the surface including the measurement point of the object to be measured. That is, since the optical displacement sensor detects the distance by receiving the reflected light from the object to be measured, a sufficient amount of reflected light can be obtained at the light receiving section to secure the detection accuracy. Need to be done. However, if the laser beam emitted from the light projection part of the optical displacement sensor is incident on the surface of the measured object at a large angle instead of perpendicularly to the plane including the measurement point, most of the reflected light is of the optical type. The light is not incident on the light receiving portion of the displacement sensor, so that the optical displacement sensor cannot obtain reflected light enough to secure the detection accuracy. In particular, in the measurement of a three-dimensional shape of an object to be measured having a large surface undulation, such as a dental prosthesis model performed in the manufacture of a dental prosthesis, there is a high possibility that an unmeasurable portion will occur. Become.

To cope with this problem, Japanese Patent Laid-Open Publication No. Hei 8-233518 discloses a method of measuring an object to be measured and an optical displacement sensor based on an appropriate relative positional relationship. After measuring the dimensional shape, the main measurement is performed while controlling the object to be measured and the optical displacement sensor so as to have an appropriate relative positional relationship based on the preliminary measurement data. That is, even if an unmeasurable part occurs in the preliminary measurement, the inclination of the surface near the unmeasurable part is calculated from the three-dimensional shape data near the unmeasurable part obtained in the preliminary measurement, and this inclination is calculated. Of the optical axis of the optical displacement sensor with respect to the normal line of the surface of the measurement point in accordance with The position is calculated, and each drive shaft is controlled based on the calculation result. Thus, when an unmeasurable portion occurs, there is almost no need to perform a complicated operation of changing the position and angle of the object to be measured, mounting the object again on a measuring table, and measuring again.

[0005]

However, Japanese Patent Application Laid-open No.
The method of -233518 requires two measurements, a preliminary measurement and a main measurement, and has a problem that the measurement time is long.

According to the present invention, an appropriate relative positional relationship between an object to be measured and an optical displacement sensor is predicted from data in the vicinity of a measuring point and controlled without performing preliminary measurement.
It is an object of the present invention to provide a three-dimensional shape measuring method capable of obtaining accurate three-dimensional shape data in one measurement.

[0007]

In order to achieve the above object, according to the present invention, a main body base and a main body base are placed on the main body base and are movable in parallel to a mounting surface of the main body base. An X-axis table, a Y-axis table mounted on the X-axis table, and movable on the Y-axis table parallel to the installation surface of the main body base and movable perpendicular to the movable direction of the X-axis table. It has a rotation axis perpendicular to the installation surface of the main body base, and has a C-axis rotating table on which the object to be measured can be mounted, and is movable vertically to the installation surface of the main body base. An apparatus for measuring a three-dimensional shape of an object to be measured, comprising: a Z-axis table; and an optical displacement sensor provided on the Z-axis table and installed so that a light projecting axis is parallel to a movable direction of the Z-axis table. ,
When capturing the position output from the optical displacement sensor, the relative distance between the optical displacement sensor and the measurement point on the object to be measured becomes constant, and a surface including the light projecting axis and the light receiving axis of the optical displacement sensor, The X-axis table, the Y-axis table, the C-axis rotation table, and the Z-axis table are controlled so that the projection axis and the plane including the normal vector of the plane near the measurement point are orthogonal to each other. A three-dimensional shape measuring method is provided.

More specifically, all the contours of the object to be measured when the object to be measured as viewed from the optical displacement sensor is projected onto the XY plane while being centered on the rotation axis of the C-axis rotary table are all A first measurement circle is set to be included, has the same center as the first measurement circle inside the first measurement circle, and is preset with respect to a radius of the first measurement circle. The second to m-th measurement circles having a small radius are set for each of the radius pitches, and the measurement points are set for each of these m measurement circles at a preset angle pitch, and
For the measurement at each measurement point of the measurement circles from m to m, three measurement points that have already been measured near the current measurement point are specified, and a normal vector of a plane including these three points is calculated. The calculated normal vector is defined as the normal vector of the current measurement point, and the angle θ between the projection vector and the X axis when the normal vector of the current measurement point is projected on the XY plane is calculated.
Based on the angle θ between the projection vector and the X axis and the normal vector of the current measurement point, an X axis table, a Y axis table, C
The positioning operation of the axis rotation table and the Z axis table is performed. After the positioning operation is completed, the output of the optical displacement sensor at the current measurement point is detected, and based on the positions of the X axis table, the Y axis table, and the C axis rotation table. X of current measurement point
The coordinate value and the Y coordinate value are calculated, and the Z coordinate value of the current measurement point is calculated based on the position of the Z-axis table and the output of the optical displacement sensor.

[0009] With the above configuration, the measurement point to be measured from now on, that is, the current measurement point, first, the already measured measurement point 3 near the current measurement point.
The normal vector of the plane including the point is calculated, the calculated normal vector is set as the normal vector of the current measurement point, and the normal vector of the current measurement point is projected on the XY plane. The angle θ with the axis is calculated. Next, the X-axis table, the Y-axis table, the C-axis rotation table, and the Z-axis table are positioned based on the angle θ between the projection vector and the X axis and the normal vector of the current measurement point. Finally, after the positioning operation is completed, the output of the optical displacement sensor at the current measurement point is detected, and the X and Y coordinate values of the current measurement point are determined based on the positions of the X-axis table, Y-axis table, and C-axis rotation table. Is calculated, and the Z coordinate value of the current measurement point is calculated based on the position of the Z-axis table and the output of the optical displacement sensor. Therefore, preliminary measurement as in the prior art is unnecessary, and three measurements are required in one measurement.
The dimensional shape data can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an X-axis table 1 that is movable in parallel with the installation surface 31a is mounted on a main substrate 31. Further, on the X-axis table 1, the X-axis table 1 A Y-axis table 2 which is movable in parallel with and perpendicular to the movable direction of the X-axis table 1 is mounted. On the Y-axis table 2, a C-axis rotation table 3 having a rotation axis perpendicular to the installation surface 31a is mounted. A dental prosthesis model 4 as a measurement object can be attached.

Further, a column 32 is provided on the main body substrate 31, and the column 32 is provided with a Z-axis table 6 which is movable in a direction perpendicular to the installation surface 31a. An optical displacement sensor 5 for measuring the three-dimensional shape of the dental prosthesis model 4 as an object to be measured is mounted on the Z-axis table 6. Reference numeral 13 is set so as to be parallel to the movable direction of the Z-axis table 6.

The driving of each of the above drive shafts (X-axis table 1, Y-axis table 2, Z-axis table 6, and C-axis rotary table 3) requires high-precision positioning control. Use a motor or servo motor and control these numerically. The operation control of the actuator of each of these drive shafts and the optical displacement sensor 5 is performed by a control device (not shown). Each drive shaft is provided with an encoder (position detector), and the position of each drive shaft is transmitted to the control device as needed. With the above configuration, the relative positional relationship between the dental prosthesis model 4 as an object to be measured and the optical displacement sensor 5 is set by operating each drive shaft based on an operation program stored in the control device. Is done.

Next, a procedure for measuring a three-dimensional shape of the dental prosthesis model 4 as an object to be measured in the above-described measuring apparatus will be described. The projection of the dental prosthesis model 4 onto the XY plane (plane parallel to the installation surface 31a) as viewed from the light projection axis 13 of the optical displacement sensor 5 is as shown by the contour line 7 in FIG. Suppose that it became a shape. First, a first measurement circle 8 that completely includes the contour line 7 indicating the dental prosthesis model 4 is set around the rotation axis 33 of the C-axis rotation table 3, and the inside of the first measurement circle 8 is set. The measurement range. In setting the measurement circle 8, the radius of the measurement circle 8 may be specified by a numerical value, or may be selected from several types of patterns registered in advance.

Next, on the first measuring circle 8 such that the surface 15 including the light projecting axis 13 and the light receiving axis 14 of the optical displacement sensor 5 coincides with the tangential direction of the first measuring circle 8 indicating the measuring range. First
The measurement start point 8 'is set. This is a process performed for the purpose of ensuring the measurement accuracy so that the projection light irradiated along the light projection axis 13 is reflected on the surface of the measurement point and the reflected light is received along the light receiving axis 14. is there. Next, while rotating the C-axis counterclockwise at every preset angular pitch starting from the first measurement start point 8 ', the position of each drive axis at each pitch point on the first measurement circle 8 And the output of the optical displacement sensor 5 is detected. The value (angle) of the pitch of the C-axis is set to the value of n, assuming that 360 ° of rotation of the first measurement circle 8 is divided into n equal parts. As a result, n pieces of measurement data are obtained on the circumference of the first measurement circle 8.

In the control device, the X-axis table 1, Y
Based on the encoder outputs from the axis table 2 and the C axis rotation table 3, the X coordinate value and the Y coordinate value of the measurement point are calculated, and the encoder output of the Z axis table 6 and the output of the optical displacement sensor 5 are output. Based on this, the Z coordinate value of the measurement point is calculated. This is because the X coordinate value and the Y coordinate value in the three-dimensional shape of the dental prosthesis model 4 are obtained from the position of the X-axis table 1, the position of the Y-axis table 2, and the rotation angle of the C-axis rotation table 3, The Z coordinate value of the three-dimensional shape of the dental prosthesis model 4 is determined by the position of the Z-axis table 6 as the position of the optical displacement sensor 5 and the position of the optical displacement sensor 5.
This is obtained from the output of the optical displacement sensor 5 as the distance between the dental prosthesis model 4 and the distance. Regarding the measurement of the measurement points on the measurement circle 8, since the dental prosthesis model 4 does not exist on the measurement circle 8, the C-axis rotary table 3 operates at each angular pitch, but the X-axis table 1 and Y The axis table 2 and the Z-axis table 6 do not operate, and hold the position of the first measurement start point 8 '.

Next, as shown in FIG. 2, a point 9 'which is located inside the first measurement circle 8 by a predetermined distance (radial pitch) from the first measurement start point 8' is defined as a second point. Of the second measurement including the second measurement start point 9 '.
On the measurement circle 9, the same measurement as in the case of the first measurement circle 8 is performed. At this time, the position of the optical displacement sensor 5 at the time of measurement at the second measurement start point 9 ', that is, the position of the Z-axis table 6, is the same as that at the time of measurement at the first measurement start point 8'. However, when the second measurement start point 9 ′ is inside the contour line 7, that is, on the dental prosthesis model 4, the optical displacement sensor 5 is set to be within the measurable range of the optical displacement sensor 5. Is changed, that is, the position of the Z-axis table 6 is changed, thereby positioning the optical displacement sensor 5.

After the measurement at the second measurement start point 9 'has been completed, the C-axis is rotated counterclockwise at every preset pitch starting from the second measurement start point 9'.
The position of each drive shaft at each pitch point on the second measurement circle 9 and the output of the optical displacement sensor 5 are detected. At this time, the X-axis table 1 and the Y-axis table 2
It may be positioned in order along the circumference of the measurement circle 9 of
The Z-axis table 6 can be accurately measured by controlling the distance between the surface of the dental prosthesis model 4 and the optical displacement sensor 5 to be constant so as to be within the measurable range. To

As for the positional relationship between the optical displacement sensor 5 and the surface of the dental prosthesis model 4, as shown in FIG. 3, an area 18 near the measurement point on the surface of the dental prosthesis model 4 is used.
When the surface 15 including the light projecting axis 13 and the light receiving axis 14 of the optical displacement sensor 5 is
3 and a plane 17 including a normal vector 16 of an area 18 near the measurement point, and an optical displacement sensor 5 centered on an axis parallel to the light projecting axis 13 of the optical displacement sensor 5 so as to be orthogonal to each other.
By controlling the X-axis table 1, the Y-axis table 2, and the C-axis rotary table 3, the relative position of the dental prosthesis model 4 and the relative position of the dental prosthesis model 4 can be adjusted so that the reflected light There is no hiding behind the irregularities, and it is possible to measure with high accuracy.

This point will be described in more detail. For example, assuming that the point to be measured is located on a plane including three points for which data has already been acquired at nearby points, the height of the measurement point is obtained. , And the direction of the normal vector of the plane including the measurement point may be predicted to control each drive axis. Specifically, as shown in FIG. 4, in order to predict the Z coordinate of a point D in the vicinity and the direction of the normal vector from three points A, B, and C for which measurement data has already been acquired, a point D is 3
Assume that the coordinates of point A are (XI, YI, ZI), the coordinates of point B are (XJ, YJ, ZJ), and the coordinates of point C, assuming that they are on the same plane as plane 19 including points A, B, and C. Is (XK, YK, Z
K), assuming that the X and Y coordinates of the point D are XL and YL, respectively, the Z coordinate ZL of the point D can be obtained by equation (1). The normal vector at the point D is 3 points A,
Assuming that this is the same as the normal vector 20 of the plane formed by B and C, the angle θ formed by the projection vector 21 of this normal vector 20 onto the XY plane and the X axis is expressed by the following equation (2). Can be obtained by

[0020]

(Equation 1)

The angle θ formed by the Z coordinate ZL of the point D obtained by the equations (1) and (2) and the angle θ between the normal vector of the point D and the X axis of the projection vector 21 onto the XY plane. What is necessary is just to position the type displacement sensor 5 with respect to the dental prosthesis model 4 so that it may have the above-mentioned optimal positional relationship.

As described above, in the measurement at the measurement points on the first measurement circle 8, there is no unmeasurable measurement point because the dental prosthesis model 4 does not exist.
It is not necessary to perform a series of processes using measurement points for which data has been acquired, such as measurement at measurement points on the measurement circle 9 described above. A second measurement circle 9 including a second measurement start point 9 '
In the measurement at the upper measurement point, the data of the measurement point on the first measurement circle 8 which has already been measured is used.
A measurement point that cannot be measured due to the presence of the dental prosthesis model 4 must not be present on the first measurement circle 8.

After the measurement at the measurement point on the second measurement circle 9, as shown in FIG. 2, the second measurement circle is moved a predetermined distance (radius pitch) from the second measurement start point 9 '. 9
Is set as the third measurement start point, and the third measurement circle 1 including the third measurement start point 10 '
With respect to 0, the same measurement as in the case of the second measurement circle 9 is performed. Thereafter, by repeating the same measurement as in the case of the second measurement circle 9 up to the m-th measurement circle, three-dimensional shape data of the dental prosthesis model 4 can be obtained.

The embodiment of the present invention has been described above. With respect to the above equations (1) and (2), the Z coordinate ZL of the obtained point D and the XY of the normal vector of the point D are obtained.
In order to accurately determine the angle θ between the projection vector 21 and the X-axis on the plane, there must be three data-acquired points in the immediate vicinity of the point to be measured (current measurement point). In order to increase the density of the entire point, it is necessary to set the angle pitch of the measurement circle small (set a large number of equal parts n) or to set the interval of the measurement circles, that is, the radius pitch small.

Further, in the present embodiment, in the measurement in the measurement circles after the second measurement circle 9 except for the first measurement circle 8, the data of the measurement points which have already been measured is always used. In the measurement at a certain measurement point on the measurement circle after the second measurement circle 9, if sufficient reflected light is incident on the light receiving section of the optical displacement sensor 5, this measurement point has already been measured. Instead of using the data of the measurement points, the output of the optical displacement sensor 5 may be taken as it is, similarly to the measurement in the first measurement circle 8.

[0026]

According to the present invention, when the position output from the optical displacement sensor is taken in, the relative distance between the optical displacement sensor and the measurement point on the object to be measured becomes constant, and the position of the optical displacement sensor is reduced. The horizontal position and the rotational position of the object to be measured are positioned so that the plane including the projection axis and the reception axis and the plane including the normal vector of the plane near the projection axis and the measurement point are orthogonal to each other. The X-axis table, the Y-axis table, and the C-axis rotary table are controlled, and the Z-axis table for positioning the vertical position of the optical displacement sensor is controlled. By predicting and controlling an appropriate relative positional relationship from data in the vicinity of the measurement point, it is possible to perform three measurements in one measurement without performing a preliminary measurement.
Dimensional shape data can be obtained.

As a result, the measurement error of the optical displacement sensor can be reduced with almost no increase in the measurement time as compared with the case where only the main measurement is performed, and the reflected light can be reflected on the object to be measured. Accurate 3 without hiding behind
Dimensional shape data can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing an entire configuration of a measuring device for a dental prosthesis model 4 according to an embodiment of the present invention.

FIG. 2 is a view showing a contour line 7 showing a dental prosthesis model 4 and a measurement circle in one embodiment of the present invention.

FIG. 3 shows an area 1 near a measurement point on the surface of the optical displacement sensor 5 and the dental prosthesis model 4 in one embodiment of the present invention.
FIG. 8 is a diagram for explaining a positional relationship with the position No. 8;

FIG. 4 is a view for explaining prediction of a Z coordinate of a point D in the vicinity thereof and a direction of a normal vector thereof from three points A, B, and C for which measurement data has already been acquired in an embodiment of the present invention. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 X-axis table 2 Y-axis table 3 C-axis rotation table 4 Model for dental prosthesis (measurement object) 5 Optical displacement sensor 6 Z-axis table 7 Outline line of model 4 for dental prosthesis 8 First measurement circle 8 'First measurement start point 9 Second measurement circle 9' Second measurement start point 10 Third measurement circle 10 'Third measurement start point 13 Projection axis of optical displacement sensor 5 14 Optical displacement sensor 5 Light receiving axis 15 Surface including light projecting axis 13 and light receiving axis 14 16 Normal vector of region 18 17 Surface including light projecting axis 13 and normal vector 16 18 Near the measurement point on the surface of the dental prosthesis model 4 Area 19 Plane including three points A, B, and C for which measurement data has been acquired 20 Normal vector of plane 19 21 Projection vector of normal vector 31 Main body base 31a Installation surface of main body base 32 Column 33 Center of measurement circle (C Shaft rotation Bull of the axis of rotation)

Claims (2)

[Claims] An X-axis table mounted on the main body base and movable parallel to an installation surface of the main body base; and an X-axis table mounted on the X-axis table; A Y-axis table movable parallel to the installation surface of the main body base and orthogonal to the movable direction of the X-axis table; and mounted on the Y-axis table and perpendicular to the installation surface of the main body base. A C-axis rotary table having a rotating axis and capable of mounting an object to be measured; a Z-axis table movable vertically to an installation surface of the main body base; and a Z-axis table provided on the Z-axis table. And a three-dimensional shape measuring device for an object to be measured, comprising: an optical displacement sensor installed so that a light projecting axis is parallel to a movable direction of a Z-axis table; and a position output from the optical displacement sensor. When capturing The relative distance between the displacement sensor and the measurement point on the object to be measured is constant, and the method of measuring the surface including the light projecting axis and the light receiving axis of the optical displacement sensor and the surface near the light projecting axis and the measurement point A three-dimensional shape measuring method, wherein the X-axis table, the Y-axis table, the C-axis rotation table, and the Z-axis table are controlled so that a plane including a line vector is orthogonal to each other. 2. An X-axis table mounted on the main body base and movable in an X-axis direction parallel to an installation surface of the main body base, and mounted on the X-axis table. A Y-axis table parallel to the installation surface of the main body base and movable in the Y-axis direction orthogonal to the X-axis; and a table mounted on the Y-axis table for installation of the main body base. A C-axis rotary table having a rotation axis perpendicular to the surface and capable of mounting an object to be measured, and a Z-axis movable in a Z-axis direction perpendicular to the installation surface of the main body base A three-dimensional shape measuring device for an object to be measured, comprising: a table; and an optical displacement sensor provided on the Z-axis table and installed so that a projection axis is parallel to the Z-axis. Around the rotation axis of the table,
A first measurement circle is set so as to include all the contours of the measured object when the measured object viewed from the optical displacement sensor is projected on an XY plane, and the inside of the first measured circle is set. The second to m-th measurement circles having the same center as the first measurement circle and having smaller radii at every predetermined radius pitch with respect to the radius of the first measurement circle are set. For each of the m measurement circles, a measurement point is set for each preset angular pitch. For the measurement at each measurement point of the second to m-th measurement circles, the measurement circle is located near the current measurement point. Specifying three measurement points that have already been measured, calculating a normal vector of a plane including the three points, and using the calculated normal vector as a normal vector of the current measurement point, When the line vector is projected on the XY plane, the angle θ between the projected vector and the X axis is The X-axis table, the Y-axis table, the C-axis rotation table, and the Z-axis table are positioned based on the angle θ between the projection vector and the X-axis and the normal vector of the current measurement point. After the operation is completed, the output of the optical displacement sensor at the current measurement point is detected, and the X and Y coordinate values of the current measurement point are calculated based on the positions of the X-axis table, Y-axis table, and C-axis rotation table. And a method of calculating a Z-coordinate value of a current measurement point based on a position of the Z-axis table and an output of the optical displacement sensor.