JP2012088149A - Squareness error calculation method for front face property measurement machine, and calibration jig - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a squareness error calculation method for a front face property measurement machine, which can easily and highly accurately calculate a squareness error by using a simple and inexpensive calibration jig, and to provide the calibration jig.SOLUTION: A calibration jig 60 where three reference spheres 62A-62C are arranged at right angles on a calibration plate 61 is arranged on a table 16, so as to obtain center coordinates of the three reference spheres by a contact type detector 20 (a first measurement process). Then, an intersection angle θ1 formed by two straight lines connecting the center coordinates is calculated (a first angle calculation process). Secondly, the calibration jig is rotated by 90 degrees on the same plane and arranged on the table, so as to obtain center coordinates of the three reference spheres by the contact type detector (a second measurement process). Then, an intersection angle θ2 formed by two straight lines connecting the center coordinates is calculated (a second angle calculation process). Finally, a squareness error between the movement direction of a Y-axis drive mechanism 17 and the movement direction of an X-axis drive mechanism 48 is calculated based on the intersection angles θ1, θ2 (a squareness error calculation process).

Description

  The present invention relates to a method for calculating the squareness error of a surface texture measuring instrument that measures the surface shape, surface roughness, and the like of an object to be measured, and a calibration jig used therefor.

  While the stylus is in contact with the surface of the object to be measured, the stylus is moved along the surface of the object to be measured. At this time, the displacement of the stylus caused by the surface shape and surface roughness of the object to be measured is detected. 2. Description of the Related Art A surface property measuring machine that measures surface properties such as a surface shape and surface roughness of an object to be measured from a stylus displacement is known (see, for example, Patent Document 1).

Conventionally, in this type of surface texture measuring instrument, a plurality of objects to be measured are automatically arranged, or the table on which the object is measured is moved by a stylus to measure several measurement surfaces. A table unit with a built-in drive mechanism that moves in a direction (Y-axis direction) perpendicular to the direction (X-axis direction) can be detachably and fixedly attached to the base of the surface texture measuring instrument Property measuring machines are also known.
In such a surface texture measuring device, if the measurement point in the horizontal plane is captured by changing the position in the X-axis direction and the position in the Y-axis direction, two-dimensional dimensions and shapes can be evaluated for the captured measurement point. Can do.

JP-A-5-87562

In the above-described surface texture measuring machine configured so that the table unit is detachable, a positioning rail is arranged on the base, the reference surface of the table unit is abutted against the positioning rail, and the X axis (stylus movement direction) and Y axis ( Positioning at right angles to the table movement direction).
However, this method has a large variation depending on the abutting method and the operator. For this reason, the perpendicularity when the table unit is once removed from the surface texture measuring machine and attached again changes greatly from the previous state.

  Therefore, each time the table unit is removed and attached, the perpendicularity measurement work between the XY axes is inevitably performed. For example, in the method of performing the perpendicularity measurement work using a right angle skewer and an electric micrometer, the right angle measurement work is performed. Expensive equipment such as a skewer and an electric micrometer is required, and it takes time to set up a right angle skewer and set an electric micrometer.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a squareness error calculation method and calibration jig for a surface texture measuring machine capable of easily and accurately calculating a squareness error using a simple and inexpensive calibration jig. There is to do.

  The perpendicularity error calculation method for a surface texture measuring machine according to the present invention includes a base, a table on which an object to be measured is placed, and a first drive mechanism that reciprocates the table in one direction in a horizontal plane. A table unit that is detachably and fixedly attached to the upper surface, a detector that has a stylus in contact with the surface of the object to be measured, and that detects the displacement of the stylus, and that the detector is moved in the direction of movement of the table. And a second drive mechanism that moves in a direction orthogonal to the surface. In the perpendicularity error calculation method of the surface texture measuring instrument that measures the shape or surface roughness of the object to be measured, three standards for obtaining the center from the outer shape A calibration jig in which elements are arranged at right angles to the calibration plate is arranged on the table, and the three reference elements are measured by the detector to determine the center coordinates of the three reference elements. 2 connecting the center coordinates of the reference element located at the corner of the right angle arrangement and the center coordinates of the other two reference elements among the center coordinates obtained in the first measurement process. The first angle calculating step for obtaining two straight lines and calculating the crossing angle θ1 of the two straight lines and the calibration jig are rotated on the same plane by 90 degrees and arranged on the table. A second measurement step of measuring the three reference elements to determine center coordinates of the three reference elements, and of the reference coordinates located at the corners of the right angle arrangement among the center coordinates obtained in the second measurement step; A second angle calculation step of obtaining two straight lines connecting the central coordinates and the central coordinates of the other two reference elements, and calculating an intersection angle θ2 of the two straight lines; and the intersection calculated in the first angle calculation step Calculated by the angle θ1 and the second angle calculation step. Characterized in that the crossing angle θ2 Prefecture and a squareness error calculation step of calculating the squareness error between the moving direction of the moving direction and the second driving mechanism of the first drive mechanism.

According to such a configuration, first, a calibration jig in which three reference elements whose centers are obtained from the outer shape are arranged at right angles to the calibration plate is arranged on the table, and the three reference elements are measured by the detector. The center coordinates of the three reference elements are obtained (first measurement step). Subsequently, out of the center coordinates thus obtained, two straight lines connecting the center coordinates of the reference element located at the corner of the right angle arrangement and the center coordinates of the other two reference elements are obtained. The intersection angle θ1 is calculated (first angle calculation step).
Next, the calibration jig is rotated 90 degrees in the same plane and placed on the table, and the three reference elements are measured by the detector to obtain the center coordinates of the three reference elements (second measurement step). . Subsequently, out of the center coordinates thus obtained, two straight lines connecting the center coordinates of the reference element located at the corner of the right angle arrangement and the center coordinates of the other two reference elements are obtained. The intersection angle θ2 is calculated (second angle calculation step).
Finally, the perpendicularity between the moving direction of the first drive mechanism and the moving direction of the second drive mechanism from the intersecting angle θ1 calculated in the first angle calculating step and the intersecting angle θ2 calculated in the second angle calculating step. An error is calculated (perpendicularity error calculation step).
Therefore, using a simple and inexpensive calibration jig in which three reference elements whose centers are obtained from the outer shape are arranged at right angles to the calibration plate, the movement direction of the first drive mechanism and the movement direction of the second drive mechanism are determined. Since the squareness error can be obtained, the squareness calibration can be performed easily and with high accuracy.

  The calibration jig of the present invention has a base, a table on which the object to be measured is placed, and a first drive mechanism that reciprocates the table in one direction in a horizontal plane, and is detachably fixed to the upper surface of the base. A table unit that can be mounted; a detector having a stylus that is in contact with the surface of the object to be measured; and a detector that detects the displacement of the stylus; and the detector in a direction perpendicular to the moving direction of the table. A calibration jig used in a perpendicularity error calculation method of a surface texture measuring machine for measuring the shape or surface roughness of the object to be measured, the calibration plate, and a calibration plate It is characterized by including three reference elements that are arranged at right angles to the plate and whose center is determined from the outer shape.

  According to the calibration jig having such a configuration, since it is configured to include a calibration plate and three reference elements that are arranged at right angles to the calibration plate and whose center is obtained from the outer shape, it is simple and inexpensive. Can be configured.

In the calibration jig according to the present invention, it is preferable that the reference element is constituted by a reference sphere.
According to such a configuration, it is only necessary to arrange three spheres at right angles on the calibration plate, so that the calibration jig can be easily manufactured.

The perspective view which shows the surface texture measuring machine which concerns on one Embodiment of this invention. The figure which shows the attachment structure of a base and a table unit in embodiment same as the above. The block diagram which shows a control apparatus and its peripheral mechanism in embodiment same as the above. The perspective view which shows the jig | tool for calibration in embodiment same as the above. The figure which shows a 1st measurement process in embodiment same as the above. The figure which shows a 2nd measurement process in embodiment same as the above. The figure which shows the calculation principle of a squareness error in embodiment same as the above.

<Description of surface texture measuring instrument (see FIGS. 1 to 3)>
As shown in FIGS. 1 to 3, the surface texture measuring instrument according to the present embodiment is detachably and fixedly attached to one side of the upper surface of the base 1 and the object to be measured is unidirectional in a horizontal plane. A Y-axis table unit 10 as a table unit to be moved (here, in the Y-axis direction), a contact detector 20 having a stylus 24 in contact with the surface of the object to be measured, and a surface image of the object to be measured. An image probe 30, a Z-axis drive means 40 and an X-axis drive means 46 for moving the contact detector 20 and the image probe 30 in the Z-axis direction and the X-axis direction orthogonal to the Y-axis direction, and The control apparatus 50 (refer FIG. 3) to control is provided.

  A mounting groove 2 having a reverse T-shaped cross section is formed along the X-axis direction at the center position in the front-rear direction of the base 1, and a positioning rail 3 having a rectangular cross section is positioned behind the mounting groove 2 in the X direction. It is mounted parallel to the axial direction.

The Y-axis table unit 10 includes a rectangular frame-shaped main body case 11, a table 16 that is supported in the main body case 11 so as to be movable in the Y-axis direction, and places an object to be measured on the upper surface thereof. And a Y-axis drive mechanism 17 as a first drive mechanism that moves in the direction.
The main body case 11 is formed with a reference surface 12 that abuts against the positioning rail 3 of the base 1 on the bottom surface, and uses a bolt 4 inserted into the mounting groove 2 on the side surface and a nut 5 that is screwed thereto. Thus, a flange portion 13 for fixing the main body case 11 to the base 1 is formed. An opening 14 is formed on the upper surface of the main body case 11 over the range of movement of the table 16, and a bellows-like cover 15 is attached to a gap between the opening 14 and the table 16.
The Y-axis drive mechanism 17 includes, for example, a motor 18 and a feed screw 19 that is rotationally driven by the motor 18 to move the table 16 forward and backward in the Y-axis direction.

The Z-axis driving means 40 includes a column 41 erected on the upper surface of the base 1, a Z slider 42 provided on the column 41 so as to be movable in the vertical direction (Z-axis direction), and the Z slider 42 in the vertical direction. And a Z-axis drive mechanism 43 that moves up and down.
The X-axis drive means 46 is provided on the Z slider 42 so as to be movable in the Y-axis direction and the direction orthogonal to the Z-axis direction (X-axis direction), and this X-slider 47 in the X-axis direction. An X-axis drive mechanism 48 as a second drive mechanism to be moved is included.
The Y-axis drive mechanism 43 and the Z-axis drive mechanism 48 are not shown in the figure, but include, for example, a ball screw shaft and a nut member that is screwed to the ball screw shaft and fixed to the movable member. It is constituted by a feed screw mechanism.

  The contact-type detector 20 includes a detector main body 21 that is suspended and supported by an X slider 47, an arm 25 that is swingably supported by the detector main body 21 and that has a stylus 24 at the tip, and a swing amount of the arm 25. It is comprised from the detection part (illustration omitted) which detects this.

The image probe 30 includes a cylindrical probe body 32 integrally connected to the X slider 47 together with the contact detector 20, and a probe head 33 supported downward at the tip of the probe body 32. Although not shown, the probe head 33 receives an object lens, an LED as a light source arranged on the outer periphery of the object lens, and reflected light from the object to be measured that has passed through the object lens, and displays an image of the object to be measured. Comprising a CCD sensor for imaging,

As shown in FIG. 3, the control device 50 includes an input device 51, a display device, in addition to the X-axis drive mechanism 48, the Y-axis drive mechanism 17, the Z-axis drive mechanism 43, the contact detector 20, and the image probe 30. 52 and a storage device 53 are connected.
The input device 51 is composed of, for example, a portable keyboard or joystick, and performs various operation commands and data input.
The display device 52 displays the image acquired by the image probe 30 and the shape and roughness data obtained by the contact detector 20.
The storage device 53 stores a program storage unit 54 that stores a measurement program and the like, a correction data storage unit 55 that stores correction data such as a squareness error, which will be described later, and image data and measurement data captured during measurement. A measurement data storage unit 56 and the like are provided.

  The control device 50 stores measurement data obtained by executing the measurement program in the measurement data storage unit 56, corrects the measurement data with the correction data stored in the correction data storage unit 55, and outputs the measurement data as a measurement value. In addition to the above, an edge detection function for detecting the edge of the object to be measured from the image of the object to be measured captured by the image probe 30, and the focal position of the objective lens on the surface in the height direction (Z-axis direction) of the object to be measured Is provided with an auto-focus function that detects the position of the object to be measured in the height direction from the amount of displacement by displacing the objective lens in the height direction so as to match.

<Description of calibration jig (see FIG. 4)>
The calibration jig 60 is a calibration jig used when calculating the squareness error between the movement direction of the Y-axis drive mechanism 17 and the movement direction of the X-axis drive mechanism 48 in the surface texture measuring instrument described above. The calibration plate 61 includes three reference spheres 62A, 62B, and 62C as reference elements disposed at right angles to the calibration plate 61.
The calibration plate 61 is made of a substantially square plate material having a predetermined thickness.
The three reference spheres 62 </ b> A, 62 </ b> B, and 62 </ b> C are embedded in three corners of the calibration plate 61 via a disk-shaped reference sphere mounting member 63. That is, the reference sphere mounting member 63 is calibrated so that the reference spheres 62A, 62B, and 62C are embedded so as to be partially exposed at the center of the reference sphere mounting member 63, and the three reference spheres 62A, 62B, and 62C are at right angles. The position of the plate 61 is adjusted and bonded and fixed.
Thereby, an angle (intersection angle) formed by a straight line connecting the center of the reference sphere 62A and the center of the reference sphere 62B and a straight line connecting the center of the reference sphere 62A and the center of the reference sphere 62C is a right angle. It is configured.

<Description of perpendicularity error calculation method (see FIGS. 5 to 7)>
In the surface texture measuring machine, the squareness error between the moving direction of the Y-axis driving mechanism 17 and the moving direction of the X-axis driving mechanism 48 is calculated as follows.
(A) First, after placing the calibration jig 60 on the table 16, the center coordinates of the three reference spheres 62A, 62B, 62C are obtained by the contact detector 20 (first measurement step).
As shown in FIG. 5, for each reference sphere 62A, 62B, 62C, the Y-axis drive is performed so that the stylus 24 of the contact detector 20 intersects the circular outlines of the reference spheres 62A, 62B, 62C. The mechanism 17 and the X-axis drive mechanism 48 are moved to acquire position data of at least three points of the circular outlines of the reference spheres 62A, 62B, and 62C, and a circle is applied to the acquired position data to obtain the center of the circle. The coordinates, that is, the center coordinates P1, P2, P3 of the reference spheres 62A, 62B, 62C are obtained.

(B) Subsequently, among the center coordinates P1 to P3 measured in the first measurement step, the center coordinates P1 of the reference sphere 62A located at the corners arranged at right angles and the center coordinates of the other two reference spheres 62B and 62C. Two straight lines connecting P2 and P3 are obtained, and an intersection angle between the two straight lines is calculated (first angle calculating step).
Specifically, a straight line L1 connecting the center coordinates P1 of the reference sphere 62A and the center coordinates P2 of the reference sphere 62B, and a straight line L2 connecting the center coordinates P1 of the reference sphere 62A and the center coordinates P3 of the reference sphere 62C are obtained. The intersection angle θ1 between the two straight lines L1 and L2 is calculated.

(C) Next, as shown in FIG. 6, the calibration jig 60 is arranged on the table 16 in a state of being rotated 90 degrees in the same plane, and three reference spheres 62 </ b> A, The center coordinates P4, P5, and P6 of 62B and 62C are obtained (second measurement step). The center coordinates P4, P5, and P6 of the reference spheres 62A, 62B, and 62C are obtained in the same manner as in the first measurement process.

(D) Subsequently, among the center coordinates P4, P5 and P6 measured in the second measurement step, the center coordinates P4 of the reference sphere 62A located at the corner of the right angle arrangement and the other two reference spheres 62B and 62C. Two straight lines connecting the central coordinates P5 and P6 are obtained, and an intersection angle θ2 between the two straight lines is calculated (second angle calculating step).
Specifically, a straight line L3 connecting the center coordinate P4 of the reference sphere 62A and the center coordinate P5 of the reference sphere 62A, and a straight line L4 connecting the center coordinate P4 of the reference sphere 62A and the center coordinate P6 of the reference sphere 62C are obtained. The intersection angle θ2 between the two straight lines L3 and L4 is calculated.

(E) Finally, based on the intersection angle θ1 calculated in the first angle calculation step and the intersection angle θ2 calculated in the second angle calculation step, the moving direction of the Y-axis drive mechanism 17 and the X-axis drive mechanism 48 A squareness error with respect to the moving direction is calculated (squareness error calculation step).
That is, the crossing angle θ1 calculated in the first angle calculation step and the crossing angle θ2 calculated in the second angle calculation step are the reference spheres 62A arranged in the calibration jig 60, as shown in FIG. Since there is a squareness error δ with respect to θ that does not change depending on the positions of 62B and 62C, the squareness error δ can be calculated from the following equation.

θ1 = θ−δ (1)
θ2 = θ + δ (2)
δ = (θ2−θ1) / 2 (3)

  When the squareness error δ calculated in this way is stored in the correction data storage unit 55, the control device 50 stores the measurement data obtained by executing the measurement program in the measurement data storage unit 56, and this measurement is performed. Since the data can be corrected with the correction data stored in the correction data storage unit 55 and output as a measured value, the squareness error between the movement direction of the Y-axis drive mechanism 17 and the movement direction of the X-axis drive mechanism 48 can be reduced. It can be corrected.

<Effect of embodiment>
According to the present embodiment, the movement direction of the Y-axis drive mechanism 17 and the movement of the X-axis drive mechanism 48 are performed using the calibration jig 60 in which the three reference spheres 62A, 62B, 62C are arranged at right angles to the calibration plate 61. Since the squareness error with respect to the direction can be calculated, if the measurement value is corrected using this squareness error as a correction value, the squareness can be calibrated easily and with high accuracy.

Therefore, even when the user himself removes and attaches the Y-axis table unit 10, the squareness accuracy between the moving direction of the Y-axis drive mechanism 17 and the moving direction of the X-axis drive mechanism 48 can be easily calibrated. Can be used in In particular, since the reliability of the combined accuracy of the Y-axis and the X-axis is improved, high-precision measurement can be expected even in oblique measurement.
Further, the calibration jig 60 is composed of the calibration plate 61 and the three reference spheres 62A, 62B, and 62C arranged at the corners of the calibration plate 61, so that it can be manufactured easily and inexpensively.

  In addition, since the image probe 30 is provided, measurement using the image probe 30 alone is also possible. For example, the line width and the hole diameter can be measured from the image acquired by the image probe 30, and the dimension (step size) of the objective lens in the optical axis direction is also measured using the autofocus function of the image probe 30. it can.

<Modification>
The present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

In the embodiment, the three reference spheres 62A, 62B, and 62C of the calibration jig 60 are measured by the contact detector 20, and the center coordinates of these reference spheres 62A, 62B, and 62C are calculated. The image probe 30 detects edges of at least three positions of the circular outlines of the reference spheres 62A, 62B, and 62C, and applies circles from these three positions to obtain the center coordinates of the circles, that is, the reference spheres 62A, 62B, and 62C. Alternatively, the center coordinates may be obtained.

  In the embodiment, the calibration jig 60 in which the three reference spheres 62A, 62B, and 62C are arranged at right angles on the calibration plate 61 is used. However, the present invention is not limited to this. For example, a configuration in which hemispherical reference elements are arranged may be used. Alternatively, a configuration in which concave spherical shaped depressions are formed at three corners of the calibration plate 61 may be used. In short, the present invention is not limited to the above embodiment as long as the center coordinates can be specified from the outer shape.

In the embodiment, the image probe 30 is provided. However, the image probe 30 may not be particularly provided.

  The present invention can be used for, for example, a surface roughness measuring machine and a shape measuring machine.

1 ... Base,
10 ... Y-axis table unit,
16 ... table,
17 ... Y-axis drive mechanism (first drive mechanism),
20 ... contact type detector,
48 ... X-axis drive mechanism (second drive mechanism),
60 ... Calibration jig,
61 ... Calibration plate,
62A-62C ... reference sphere (reference element),
P1 to P3, P4 to P6 ... center coordinates,
L1-L4 ... straight line,
θ1, θ2 ... crossing angle,
δ: Squareness error.

Claims (3)

A base, a table on which the object to be measured is placed, and a table unit having a first drive mechanism for reciprocating the table in one direction in a horizontal plane, and detachably and fixably attached to the upper surface of the base; A detector having a stylus in contact with the surface of the object to be measured and detecting the displacement of the stylus; and a second drive mechanism for moving the detector in a direction perpendicular to the moving direction of the table. In the method for calculating the perpendicularity error of a surface texture measuring machine that measures the shape or surface roughness of the object to be measured,
A calibration jig in which three reference elements whose centers are obtained from the outer shape are arranged at right angles to the calibration plate is arranged on the table, and the three reference elements are measured by the detector to measure the centers of the three reference elements. A first measuring step for obtaining coordinates;
Of the center coordinates obtained in the first measurement step, two straight lines connecting the center coordinates of the reference element located at the corner of the right angle arrangement and the center coordinates of the other two reference elements are obtained, and the two A first angle calculating step of calculating a crossing angle θ1 of the straight line;
A second measuring step in which the calibration jig is rotated 90 degrees in the same plane and arranged on the table, and the three reference elements are measured by the detector to obtain the center coordinates of the three reference elements; ,
Among the center coordinates obtained in the second measurement step, two straight lines connecting the center coordinates of the reference element located at the corner of the right angle arrangement and the center coordinates of the other two reference elements are obtained, and the two A second angle calculating step of calculating a crossing angle θ2 of the straight lines;
From the intersecting angle θ1 calculated in the first angle calculating step and the intersecting angle θ2 calculated in the second angle calculating step, there is a direct difference between the moving direction of the first drive mechanism and the moving direction of the second drive mechanism. A squareness error calculating step for calculating an angle error;
A method for calculating the squareness error of a surface texture measuring machine. A base, a table on which the object to be measured is placed, and a table unit having a first drive mechanism for reciprocating the table in one direction in a horizontal plane, and detachably and fixably attached to the upper surface of the base; A detector having a stylus in contact with the surface of the object to be measured and detecting the displacement of the stylus; and a second drive mechanism for moving the detector in a direction perpendicular to the moving direction of the table. A calibration jig used in a squareness error calculation method of a surface texture measuring machine for measuring the shape or surface roughness of the object to be measured,
A calibration plate;
It is arranged at right angles to the calibration plate and includes three reference elements whose center is obtained from the outer shape.
A calibration jig characterized by that. The calibration jig according to claim 2,
A calibration jig, wherein the reference element is constituted by a reference sphere.

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