Data processing: measuring – calibrating – or testing – Calibration or correction system – Position measurement
Reexamination Certificate
2002-10-04
2004-03-02
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Position measurement
C702S094000, C702S104000, C033S503000, C033S559000
Reexamination Certificate
active
06701267
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
A present invention relates to a method for calibrating a probe and a computer-readable medium therefore, and more relates to a method for calibrating error of a scanning probe measuring surface texture such as size, shape, waviness, roughness, etc. of a work by scanning or error of a touch signal probe, and to a computer-readable medium for the calibration method.
2. Description of the Related Art
There are known surface texture measuring machines for measuring a contour shape, roughness, waviness, etc. of a surface of a work, such as a coordinate measuring machine (Hereinafter, referred to CMM) for measuring the three-dimensional shape of a work, a contour shape measuring machine or vision measuring machine for measuring the two-dimensional contour shape of a work, a roundness measuring machine for measuring the roundness of a work, a surface roughness tester for measuring the waviness, roughness, etc. of a surface of a work, and so on. In most cases, each of these machines has a uniaxial or multiaxial guide mechanism for moving the work relatively to a contact type or non-contact type sensor.
The guide mechanism has a guide, a feed screw, and a nut thread-engaged with the feed screw. The guide mechanism moves a slider connected to the nut. In most cases, the movement of the slider is measured with a linear scale or the like.
The guide mechanism need not have a feed screw. That is, the guide mechanism may have a guide, and a slider, in which the displacement quantity of the slider moved manually is read by a linear scale or the like. Generally, at least one kind of sensor such as a probe or a CCD camera is attached to the slider. Probes used for these applications are classified into touch signal probes and scanning probes.
FIG. 6
shows an example of use of a scanning probe
118
attached to a forward end of a spindle
117
in CMM
100
.
The CMM
100
is configured as follows. A measuring table
112
is placed on a vibration isolating stand
111
so that an upper surface of the measuring table
112
forms a base plane coincident with a horizontal plane. A beam
114
extended in an X-axis direction is supported at upper ends of beam supports
113
a
and
113
b
erected from opposite side ends of the measuring table
112
. A lower end of the beam support
113
a
is driven in a Y-axis direction by a Y-axis drive mechanism
115
. A lower end of the beam support
113
b
is supported by an air bearing so that the beam support
113
b
can move in the Y-axis direction relatively to the measuring table
112
. The current position of the moved beam supports
113
a
and
113
b
is detected by a Y-axis scale
245
.
The beam
114
supports a column
116
extended in a vertical direction (Z-axis direction). The column
116
is driven along the beam
114
in the X-axis direction. The current position of the moved column
116
is detected by an X-axis scale
244
. The column
116
is provided with the spindle
117
so that the spindle
117
is driven along the column
116
in the Z-axis direction. The current position of the moved spindle
117
is detected by a Z-axis scale
246
.
The scanning probe
118
having a contact type stylus
119
and a contact ball
121
is attached to a lower end of the spindle
117
. The probe
118
measures a work placed on the measuring table
112
. For example, an optical linear scale or the like is used as each of the X-axis scale
244
, the Y-axis scale
245
and the Z-axis scale
246
.
Any kind of probe such as a contact type probe or a non-contact type probe is used as the probe. A touch signal probe which is a typical example of the contact type probe obtains the measurement position of the work by reading the values of various kinds of linear scales at the moment that the measurer comes into contact with the work.
JP-A-10-73429 is known as an example of the touch signal probe. The touch signal probe has a structure in which a measurer having a spherical contactor at its tip can be always restored to a home position by a seating mechanism. When the contactor comes into contact with a work, the measurer is displaced so as to depart from the seating mechanism and at the same time that electric contact is opened to output a touch signal.
The touch signal probe is basically provided to obtain the coordinates of a point on the work. To measure a plurality of points on the work, a measuring operation is required whenever one of the points is measured. When, for example, contour data of a work needs to be obtained densely, the total measurement time becomes long because a lot of positioning and measuring operations are required. As a result, the touch signal probe is influenced by the environmental change such as temperature change. Hence, the touch signal probe is not always adapted for high-accuracy measurement.
On the other hand, the scanning probe can measure the position of a work continuously. Hence, contour data can be obtained densely, speedily and easily because a plurality of points on the work can be measured. Hence, the scanning probe is hardly influenced by the environmental change, so that there is the possibility that the scanning probe performs high-accuracy measurement as a whole.
Such a scanning probe has been described in JP-A-5-256640. The probe is formed so that a stylus is supported through an X-axis slider, a Y-axis slider and a Z-axis slider which are movable in respective directions orthogonal to a pedestal.
Slide portions between the pedestal and the three sliders are supplied with compressed air to form air bearings. Hence, a frictionless guide mechanism is formed.
The guide mechanism further includes three sensors, that is, a Z-axis sensor for detecting the displacement of the Z-axis slider relative to the pedestal, a Y-axis sensor for detecting the displacement of the Y-axis slider relative to the Z-axis slider and an X-axis sensor for detecting the displacement of the X-axis slider relative to the Y-axis slider.
The three-dimensional displacement quantity of the stylus can be measured with the three sensors.
For example, an absolute optical linear scale is used as each of the sensors. When the scanning probe is moved relatively to a work in a direction of a surface of the work while the measure (hereinafter, referred to a stylus) of the scanning probe is kept in contact with the surface of the work, the stylus is displaced along the contour shape of the surface of the work. Hence, contour shape data of the work can be collected continuously.
In this case, the values of the linear scales measuring displacement of the drive mechanisms of the CMM are synthesized with the three sensor outputs from the scanning probe to thereby obtain the contour shape data. Incidentally, when the stylus is not in contact with the work, the ordinary stop positions (restored positions) of the X-axis slider, the Y-axis slider and the Z-axis slider in the scanning probe are set as the origin positions of the absolute sensors respectively.
As shown in
FIG. 6
which is a block diagram, an X-axis sensor
251
, a Y-axis sensor
252
and a Z-axis sensor
253
are built into the scanning probe
118
. The sensors
251
to
253
output the quantities of displacement of the scanning probe
118
in accordance with the displacement of the stylus
119
in the X-axis, Y-axis and Z-axis directions respectively.
A drive unit
260
has an X-axis drive circuit
261
for driving an X-axis drive mechanism
105
, a Y-axis drive circuit
262
for driving the Y-axis drive mechanism
115
, a Z-axis drive circuit
263
for driving a Z-axis drive mechanism
125
, an X-axis counter
264
for counting the output of the X-axis scale
244
, a Y-axis counter
265
for counting the output of the Y-axis scale
245
, a Z-axis counter
266
for counting the output of the Y-axis scale
246
, an X-axis P counter
267
for counting the output of the X-axis sensor
251
, a Y-axis P counter
268
for counting the output of the Y-axis sensor
252
, and a Z-axis P counter
269
for counting the output of the Z-axis sensor
253
. The respect
Noda Takashi
Sugita Kozo
Barlow John
Dougherty Anthony T.
Mitutoyo Corporation
Rankin, Hill Porter & Clark LLP
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