U.S. patent application number 09/805935 was filed with the patent office on 2001-10-18 for surface texture measuring instrument, surface texture measuring method and stylus radius measuring instrument.
This patent application is currently assigned to MITUTOYO CORPORATION. Invention is credited to Takemura, Isamu.
Application Number | 20010029778 09/805935 |
Document ID | / |
Family ID | 18606026 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029778 |
Kind Code |
A1 |
Takemura, Isamu |
October 18, 2001 |
Surface texture measuring instrument, surface texture measuring
method and stylus radius measuring instrument
Abstract
A Stylus 1 is moved along the surface of a workpiece 20 and the
surface texture of the workpiece 20 is measured based on the
displacement of the stylus 1 in the Z direction. A spherical
reference gage of known radius is measured with the stylus 1 in
advance and radius values r of the tip sphere of the stylus 1 are
calculated according to angle by subtracting the radius R of the
reference gage from the measured values. The actual contour of
workpiece 20 is calculated by using the radius values r as the
correction data according to angle and subtracting the correction
values according to angle from the measured data obtained by
movement along the surface of workpiece 20.
Inventors: |
Takemura, Isamu; (Kure-shi,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
277 S. WASHINGTON STREET, SUITE 500
ALEXANDRIA
VA
22314
US
|
Assignee: |
MITUTOYO CORPORATION
|
Family ID: |
18606026 |
Appl. No.: |
09/805935 |
Filed: |
March 15, 2001 |
Current U.S.
Class: |
73/104 ;
73/105 |
Current CPC
Class: |
G01B 5/016 20130101;
G01B 5/28 20130101 |
Class at
Publication: |
73/104 ;
73/105 |
International
Class: |
B23Q 017/09; G01N
019/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2000 |
JP |
2000-090417 |
Claims
What is claimed is:
1. A surface texture measuring instrument for measuring a surface
texture of a workpiece, said instrument comprising: a stylus moving
along a surface of the workpiece; a measurement section for
measuring a displacement of the stylus; a memory section for
storing radius values according to angle of the stylus; a
correction section for correcting a measured value obtained in the
measurement section on the basis of the radius values of the stylus
stored in the memory section.
2. The surface texture measuring instrument according to claim 1,
comprising: a detection section for detecting an angle of
inclination of the stylus with respect to a Z direction, wherein
said correction section corrects the measured value on the bases of
the radius values and the angle of inclination of the stylus.
3. The surface texture measuring instrument according to claim 1,
comprising: a radius value calculation section for calculating the
radius values according to angle of the stylus on the basis of a
measured value of a reference gage of a known radius measured with
the stylus.
4. The surface texture measuring instrument according to claim 3,
wherein said radius value calculation section calculates the radius
values according to angle of the stylus on the basis of a
difference between the measured value of the reference gage and the
radius value of the reference gage.
5. The surface texture measuring instrument according to claim 3,
wherein the reference gage is one of spherical, cylindrical, and
knife-edge-shaped.
6. The surface texture measuring instrument according to claim 3,
comprising: a detection section for detecting an angle of
inclination of the stylus with respect to a Z direction, wherein
said radius value calculation section calculates the radius values
according to angle of the stylus on the basis of the measured value
of the reference gage and the angle of inclination of the
stylus.
7. The surface texture measuring instrument according to claim 1,
comprising: a rotatable arm for holding the stylus arcuately
movable; a detection section for detecting an angle of inclination
of the stylus with respect to a Z direction, wherein said
correction section corrects the measured value on the basis of the
radius value and the angle of inclination of the stylus.
8. The surface texture measuring instrument according to claim 3,
comprising: a rotable arm for holding the stylus arcuately movable;
a detection section for detecting an angle of inclination of the
stylus with respect to a Z direction, wherein said radius value
calculation section calculates the radius values according to angle
of the stylus on the basis of the measured value of the reference
gage and the angle of inclination of the stylus.
9. A method of measuring a surface texture of a workpiece, said
method comprising: measuring a displacement of a stylus while
moving the stylus along a surface of the workpiece; correcting a
measured value obtained in the measuring step by using a correction
value on the basis of radius values according to angle of the
stylus.
10. The method of measuring the surface texture of the workpiece
according to claim 9, comprising: measuring a reference gage of a
known radius with the stylus; calculating a difference between the
measured value of the reference gage and the radius value of the
reference gage as the correction value.
11. The method of measuring the surface texture of the workpiece
according to claim 10, wherein the reference gage is one of
spherical, cylindrical, and knife-edge-shaped.
12. The method of measuring the surface texture of the workpiece
according to claim 9, comprising: detecting an angle of inclination
of the stylus with respect to a Z direction, wherein in the
correction step, the measured value is corrected on the basis of
the radius values and the angle of inclination of the stylus.
13. The method of measuring the surface texture of the workpiece
according to claim 10, comprising: detecting an angle of
inclination of the stylus with respect to a Z direction, wherein in
the calculation step, the correction value is corrected on the
basis of the difference and the angle of inclination of the
stylus.
14. A stylus radius measuring instrument comprising: a stylus
moving along a surface of a reference gage of a known radius; a
measurement section for measuring a displacement of the stylus; a
radius value calculation section for calculating radius values
according to angle of the stylus on the basis of a measured value
obtained in the measurement section; a memory section for storing
the radius values according to angle of the stylus.
15. The stylus radius measuring instrument according to claim 14,
wherein said radius value calculation section calculates the radius
values according to angle of the stylus on the basis of the
measured value and the radius value of the reference gage.
16. The stylus radius measuring instrument according to claim 14,
wherein the reference gage is one of spherical, cylindrical, and
knife-edge-shaped.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a surface texture measuring
instrument and a surface texture measurement method, in which the
contour, surface roughness, surface waviness, etc., of a workpiece
is measured by moving a stylus along a surface of the workpiece, in
particular, relates to a technique for correcting the error due to
the tip shape of the stylus. The invention also relates to a stylus
radius measuring instrument.
[0003] 2. Description of the Related Art
[0004] Surface texture measuring instruments, in which a stylus is
made to contact a workpiece and moved along the workpiece surface
to measure the contour, surface roughness, surface waviness, etc.,
of the workpiece, have been known in the related art. Such surface
texture measuring instruments are used in the measurement of
machined parts, etc. With a surface texture measuring instrument,
when the stylus is moved in one direction (X axis) along the
workpiece surface by means of a motor, the stylus becomes displaced
in the vertical direction (Z direction) due to surface irregularity
of the workpiece surface. By measuring the displacement in the X
direction and the displacement in the Z direction, the contour,
surface roughness and surface waviness of the workpiece can be
measured.
[0005] However, since the cross-sectional shape of the tip-portion
of the stylus that comes in contact with the workpiece is not a
point but is of an arcuate shape of finite size, the locus
expressed by the Z-direction displacement of the stylus will not
coincide with the actual contour of the workpiece.
[0006] FIG. 8 illustrates the difference between the locus obtained
by measurement and the actual contour of a workpiece. In this
Figure, a stylus 1 is displaced in the X direction and is displaced
in the Z direction according to the surface texture of the
workpiece. As indicated by 100 in the Figure, the measured locus of
the workpiece that corresponds to the displacement of the stylus 1
is the locus of a predetermined reference point of the stylus 1
(approximately the central point of the arcuate portion of the
stylus tip) In the measured locus of the workpiece, an offset,
corresponding to the radius r of the tip arc of stylus 1, arises
with respect to the actual contour 200 of the workpiece. In the
case where the stylus is mounted to a rotatable arm and undergoes
arcuate movement, the locus 100 is obtained by correcting for the
arc error that accompanies this arcuate movement. Thus in order to
obtain the actual contour of the workpiece, the measured value was
offset by just the radius r of the tip arc of stylus 1.
[0007] However, the cross-sectional shape of the tip of stylus 1 is
not strictly circular but its radius value differs according to
position. Thus as the workpieces to be measured are made finer and
higher in accuracy, cases have arisen where the use of just the
representative value of the tip radius ras the offset in the
related art is inadequate for measurements of such high
accuracy.
SUMMARY OF THE INVENTION
[0008] The invention has been made in view of the above problem of
the related art. It is an object of the invention to provide a
surface texture measuring instrument and a surface texture
measuring method, in which the actual surface texture, such as the
contour, surface roughness, surface waviness, etc., of a workpiece
can be obtained at high accuracy by performing correction, based on
the cross-sectional shape of the tip of the stylus, of the measured
value obtained by measuring the displacement of the stylus in the Z
direction. It is another object of the invention to provide a
stylus radius measuring instrument.
[0009] In order to achieve the above object, a surface texture
measuring instrument according to the invention, in which a surface
texture of a workpiece is measured by moving a stylus along a
surface of the workpiece and measuring a displacement of the stylus
in the Z direction, comprises a memory section, which stores radius
values according to angle of the stylus that are obtained by
measuring a spherical, cylindrical, or knife-edge-shaped reference
gage of known radius with the stylus, and a correction section,
which corrects measured values based on the radius values of the
stylus stored in the memory section.
[0010] Here, in the case where the stylus is mounted on a rotatable
arm and undergoes arcuate movement, the surface texture measuring
instrument preferably comprises a detection section, which detects
an angle of inclination of the stylus with respect to the Z
direction, wherein the correction section corrects the measured
values based on the radius values and the angles of inclination of
the stylus.
[0011] The object van be also achieved by a surface texture
measuring instrument, in which a surface texture of a workpiece is
measured by moving a stylus along a surface of the workpiece and
measuring a displacement of the stylus in the Z direction,
comprising a radius value calculation section, which calculates
radius values according to angle of the stylus that are obtained by
measuring a spherical, cylindrical, or knife-edge-shaped reference
gage of known radius with the stylus, memory section, which stores
the radius values of the stylus, and a correction section, which
corrects measured values based on the radius values of the stylus
stored in the memory section.
[0012] Here, in the case where the stylus is mounted on a rotatable
arm and undergoes arcuate movement, the surface texture measuring
instrument preferably comprises a detection section, which detects
an angle of inclination of the stylus with respect to the Z
direction, wherein the radius calculation section calculates the
radius values based on the angles of inclination of the stylus, and
the correction section corrects the measured values based on the
radius values and the angles of inclination of the stylus.
[0013] Further, in order to achieve the above object, a surface
texture measurement method according to the invention, in which a
surface texture of a workpiece is measured by moving a stylus along
a surface of the workpiece and measuring a displacement of the
stylus in the Z direction, comprises a measurement step, in which
the workpiece is measured by the stylus, and a correction step, in
which measured values of the workpiece are corrected using
correction values. The correction value is the difference between
measured value according to angle that was obtained by measuring a
spherical, cylindrical, or knife-edge-shaped reference gage of
known radius with the stylus and the radius value of the reference
gage.
[0014] Here, in the case where the stylus is mounted on a rotatable
arm and undergoes arcuate movement, the measured value is
preferably corrected in the correction step by using the correction
values and angles of inclination of the stylus with respect to the
Z direction.
[0015] The object can be achieved by a surface texture measurement
method, in which the surface texture of a workpiece is measured by
moving a stylus along a surface of the workpiece and measuring a
displacement of the stylus in the Z direction, comprising a
measurement step, in which the workpiece is measured by the stylus,
a correction value calculation step, in which correction values are
calculated as the difference between measured values according to
angle that were obtained by measuring a spherical, cylindrical, or
knife-edge-shaped reference gage of known radius with the stylus
and the radius value of the reference gage, and a correction step,
in which measured values of the workpiece are corrected using the
correction values.
[0016] Here, in the case where the stylus is mounted on a rotatable
arm and undergoes arcuate movement, the correction values are
preferably corrected in the correction value calculation step by
using angles of inclination of the stylus with respect to the Z
direction, and the measured values are corrected in the correction
step by using the correction values and the angles of inclination
of the stylus.
[0017] As has been described above, with this invention, a
spherical, cylindrical, or knife-edge-shaped reference gage is
measured and the radius values according to angle of the stylus are
calculated from the measurement results of the reference gage. To
be more specific, radius values of the stylus are calculated by
subtracting the known radius values of the reference gage from the
measured values of the reference gage. The radius values according
to angle of the stylus indicate the deviation of the stylus from a
perfect circle, and by using these radius values as correction
values and correcting the measured values obtained by actual
measurement of a workpiece by the correction values according to
angle, the actual contour of the workpiece can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a layout block diagram of a surface texture
measuring instrument of an embodiment according to the
invention;
[0019] FIG. 2 is an overall process flowchart of the surface
texture measuring instrument of the embodiment according to the
invention;
[0020] FIG. 3 is a diagram explaining the manner of measurement of
a reference gage;
[0021] FIG. 4 is an explanatory diagram of the correction
values;
[0022] FIG. 5 is an explanatory diagram illustrating the method of
correction of the measured contour using the correction values;
[0023] FIG. 6 is an explanatory diagram illustrating the arcuate
movement of the arm;
[0024] FIGS. 7A-B are respectively explanatory diagrams
illustrating the inclination of a stylus 1 that accompanies the
arcuate movement of the arm;
[0025] FIG. 8 is an explanatory diagram illustrating the difference
between the workpiece contour and the measured contour;
[0026] FIG. 9 is a layout diagram of a measuring device of the type
with which the stylus moves only in the Z direction; and
[0027] FIG. 10 is a layout diagram of another measuring device of
the type with which the stylus moves only in the Z direction.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] Embodiments of this invention shall now be described with
reference to the drawings.
[0029] FIG. 1 is a layout diagram of a surface texture measuring
instrument of an embodiment. A stylus 1 is provided on the tip of
an arm 2 which undergoes arcuate movement about a rotation center
P. While the stylus 1 is made to contact the surface of a workpiece
20, a motor 5 is driven by commands from a CPU 31 to move stylus 1
in the X direction. The amount of movement in the X direction at
this time is detected by a displacement detector 4 and the detected
value is supplied to CPU 31. Also, the displacement of stylus 1 in
the Z direction (the vertical direction perpendicular to the X
direction) is detected by a displacement detector 3, and the
detected value is likewise supplied to CPU 31. The X direction and
Z direction detection valuesthataresuppliedtoCPU31arepaired-
andstoredasmeasured data (xi, zi) (i=1 to n; n is the number of
measurement points) in RAM 33. The measured data stored in RAM 33
are of values which are offset with respect to the actual contour
data of workpiece 20 by just the amounts corresponding to the shape
of the tip of stylus 1. The CPU31 therefore reads out these
measured data stored in RAM 33 and outputs these to display 34 upon
correction. The correction of the measured data is performed using
the correction data that are stored in advance in ROM 32 or RAM 33.
The correction data can be obtained by measuring a spherical,
cylindrical, or knife-edge-shaped reference gage of known radius
with stylus 1 prior to the measurement of workpiece 20. The shape
of stylus 1 to be used is not limited to a sphere, and the stylus
may be a single-angle stylus, double-angle stylus,
knife-edge-shaped stylus or other stylus of non-spherical shape as
long as the cross-sectional shape is arcuate.
[0030] FIG. 2 shows the overall process flowchart of the present
embodiment. First, prior to the measurement of workpiece 20, the
measurement of the reference gage is performed (S101). Here, a
spherical or cylindrical reference gage of a known radius R is used
as the reference gage. The condition that the reference gage should
satisfy is that the cross-sectional shape along the X direction in
which stylus 1 is moved is a circle (or semicircle) of a known
radius R. Obviously as long as the portion that comes in contact
with the stylus satisfies this condition, the overall shape of the
reference gage does not have to be spherical or cylindrical.
[0031] After measurement of the reference gage, the correction
value r for each angle, i.e., the radius of the tip sphere of
stylus 1 for the corresponding angle, is calculated by subtracting
the radius R of the reference gage from the measured value at the
corresponding measurement point (S102). The calculated correction
value r is then stored according to angle in ROM 32 or RAM 33
(S103).
[0032] The processes of S101 to S103 are the correction data
calculation processes, and these processes shall now be described
in more detail. FIG. 3 is a schematic diagram that shows the
condition where the reference gage is measured by stylus 1. The
radius R of the reference gage is known and measurement results are
obtained by moving stylus 1 along the surface of the reference
gage. In the Figure, the contour 400 measured by stylus 1 is
obtained at each angle for the actual contour 300 of the reference
gage. By then subtracting the known radius value R of the reference
gage from the measured values obtained for each angle, the
correction value r for each angle, i.e., the radius of the tip
sphere of stylus 1 is calculated. In the case where the stylus is
mounted to a rotatable arm and undergoes arcuate movement, this
locus 400 is obtained by correcting for the arc error that
accompanies this arcuate movement.
[0033] FIG. 4 shows an example of the correction values r according
to angle that are calculated in the above manner. The correction
values r are calculated according to the angles .theta. with
respect to a predetermined direction (Z direction). To be more
specific, the correction values, i.e., the radii r1, r2, r3, . . .
of stylus 1 are calculated according to the angles .theta.1,
.theta.2, .theta.3, . . . and are stored in ROM 32 or RAM 33.
Though in the case where the cross-sectional shape of the tip of
stylus 1 is a perfect circle, a fixed value r will be obtained
regardless of the angle .theta., since the cross-sectional shape of
the tip of stylus 1 is generally not a perfect circle as has been
mentioned above, the radius value r varies according to the angle
.theta.. The manner of variation is expressed as the correction
data as shown in FIG. 4. The correction values r can be stored in
such a table format in ROM 32 or RAM 33.
[0034] Returning now to FIG. 2, after calculating and storing the
correction values r according to angle, the workpiece 20 to be
measured is set at a prescribed position and stylus 1 is moved
along the surface of workpiece 20 to measure the surface texture of
workpiece 20 (S104). As has been mentioned above, the measured data
are stored in RAM 33. After storage of the measured data in RAM 33,
CPU 31 corrects the measured data using the correction values r
according to angle that are stored in ROM 32 or RAM 33 (S105).
[0035] FIG. 5 illustrates the method of correction using the
correction values r. As shown in this Figure, for the contour
(measured contour) 500 of the workpiece that is indicated by the
measured data, the angle .theta. between the Z direction and the
direction of correction of the stylus tip radius (in general, the
tangential direction) at an arbitrary point T of the measured
contour 500, is calculated for the point T. Then, the correction
value r for this angle .theta. is read out from the correction
value table that is stored in ROM 32 or RAM 33. The correction
value r that has been read out is then subtracted from measured
contour 500 to obtain the point Q. This point Q becomes the data
corresponding to the actual contour of workpiece 20. The corrected
data are then stored again in RAM 33. After the correction process
has been performed for all points of measured contour 500, the
corrected data are displayed on display 34. In the case where the
stylus is mounted to a rotatable arm and undergoes arcuate
movement, this locus 500 is obtained by correcting for the arc
error that accompanies this arcuate movement.
[0036] It is also preferable to calculate the data between the
correction data obtained at predetermined intervals, by linear
interpolation or curvilinear interpolation.
[0037] Also, in the process of obtaining the measured contour 400
obtained by measuring the reference gage, the points between the
measured points may be obtained by curvilinear interpolation using
Bezier curves or spline curves, etc., or by linear interpolation.
It is also preferable to smoothen the measured locus to eliminate
the influence of noise.
[0038] The processes of S101 to S103 may be performed separately
from the measurement of workpiece 20 or as continuous processes to
be performed prior to the measurement of workpiece 20. That is, the
measurement of workpiece 20 may be performed after storage of the
correction values in ROM 32 in advance. In the condition where the
correction values are not stored in the memory, the reference gage
may be measured and the correction values may be calculated based
on the known radius R and stored in the memory and thereafter,
measurement can be performed upon replacing the reference gage with
the workpiece.
[0039] By thus correcting the measured data of the workpiece based
on the correction values r according to angle that are obtained by
measurement of a reference gage, that is, based on the radii of the
tip sphere of stylus 1, the actual contour of workpiece 20 can be
calculated at high accuracy.
[0040] If in measuring a reference gage, the reference gage is
measured upon mounting the stylus 1 to a supporting part, which is
displaced only in the Z direction (that is, an arm that does not
undergo arcuate movement), instead of the measuring device shown in
FIG. 1, and the resulting correction values are stored in ROM 32 or
RAM 33, the use of the stored correction values for correcting the
measured values obtained by the measuring device shown in FIG. 1
may not be appropriate in some cases. This is because in the case
where stylus 1 is mounted to the tip of the arm 2, stylus 1 is not
displaced in the Z direction to be exact as has been mentioned
above but undergoes arcuate movement about rotation center P, and
the points at which the tip of stylus 1 contacts workpiece 20 also
vary based on the arcuate rotation angle .alpha. of arm 2.
[0041] The variation of the point of contact of stylus 1 in
accompaniment with the arcuate movement of arm 2 is shown
schematically in FIGS. 6 and 7A-B. As shown in FIG. 6, when arm 2
rotates by just .alpha. from the Z direction, the tip of stylus 1
also rotates by just .alpha. from the Z direction as shown in FIGS.
7A-B, and the apparent Z direction (Z' direction) as viewed from
the tip of stylus 1 inclines by just .alpha.. By this inclination,
the angle of contact with the surface of workpiece 20 becomes
displaced as well. Thus in correcting the measured values based on
the stored correction values (these are the correction values for a
inclination of 0), the inclination angle .alpha. must be taken into
consideration. To be more specific, it is preferable to correct the
measured value by reading out, from the correction table, not the
correction data corresponding to the angle .theta. shown in FIG. 5
but the correction data corresponding to the angle obtained by
subtracting just the inclination angle .alpha. from .theta., i.e.,
the angle .theta.'=.theta.-.alpha..
[0042] Since the influence of the inclination angle on the
correction value will be small in the case where the arcuate
movement of arm 2 is minute, that is, in the case where .alpha. is
minute, it is also preferable to make the correction using the
inclination angle a only when the rotation angle of arm 2 becomes
greater than or equal to a predetermined angle. The rotation angle
.alpha. of arm 2 can be obtained from the displacement in the
Z-axis direction and the rotation radius L of the arcuate movement
of arm 2 as: 1 = sin - 1 ( Z L )
[0043] or as 2 = cos - 1 ( L 2 - Z 2 L )
[0044] Or, .alpha. may also be detected using an angle sensor
provided on arm 2 or the vicinity of arm 2, and supplied to CPU 31.
In the case where a reference gage is measured using the measuring
device shown in FIG. 1, it is also preferable to perform such a
correction for the inclination angle as long as stylus 1 undergoes
arcuate movement during the measurement of workpiece 20.
[0045] The above-described correction based on the inclination
angle .alpha. is also preferably performed on the radius values in
the case where a reference gage is measured by the measuring device
shown in FIG. 1 (that is, in the case where the stylus undergoes
arcuate movement). That is, after calculating the radii r1, r2, . .
. for each of the angles .theta.1, .theta.2, . . . , the angle data
are stored in ROM 32 or RAM 33 upon performing the correction to
.theta.'=.theta.-.alpha.. Accurate radius values will then be
stored in the form of a table.
[0046] In the case where a workpiece 20 is to be measured not with
a measuring device such as shown in FIG. 1 but by a measuring
device, with which stylus 1 is mounted to a supporting part that is
displaced only in the Z direction as shown in FIG. 9, the
correction for inclination is obviously unnecessary since the
inclination .alpha. of a stylus 1 from the Z-axis direction does
not exist to start with. To describe the condition shown in FIG. 9
briefly, an arm 2 is supported on a linear driving device 52 which
is displaced in the Z direction, and the linear driving device 52
moves in the Z direction so that the measuring pressure obtained
from a measuring pressure sensor 50 (distortion sensor) provided on
the arm 2 will be kept constant at all times. The linear driving
device 52 also moves in the X direction by means of a motor 58, a
ball screw 60, and a nut 62, and the stylus 1 that is mounted to
the tip of arm 2 is thereby scanned along the surface of workpiece
20 in the X direction. A detector 66 is provided on the nut 62 and
the displacement of the stylus 1 in the X direction is detected by
reading a scale 64 with the detector 66. The linear driving device
52 is also provided with a detector 56, and the displacement of
stylus 1 in the Z direction is detected by reading a linear scale
54 with the detector 56. It can be understood that since the linear
driving device 52 displaces the arm 2 in the Z direction in a
manner such that the measuring pressure will always be constant,
the stylus 1 will be displaced only in the Z direction. The
measurement of workpiece 20 may also be made using a simpler
measuring device such as shown in FIG. 10. In FIG. 10, a stylus 1
is mounted to an arm 2, which is displaced only in the Z direction,
and arm 2 is moved in the X direction by means of a motor 58, a
ball screw 60, and a nut 62 to cause the surface of the workpiece
20 to be scanned by the stylus 1. With either of the measuring
devices shown in FIGS. 9 and 10, since the stylus 1 is displaced
only in the Z direction, the correction for arcuate movement is
unnecessary.
[0047] As has been described above, with this invention, since
correction data on the tip sphere of the stylus are obtained
according to angle by the use of a reference gage and the
measurement results are corrected using these correction data, the
surface texture of the workpiece can be measured at high
accuracy.
* * * * *