Control method of surface characteristic measuring apparatus

Abstract

A control method of surface characteristic measuring apparatus relatively displaces by a relative displacement mechanism, detects when the distal end of the stylus contacting the measurable surface, calculates an amount of relative displacement in the Z-axis direction between the measuring device and the measured object required for a measuring arm to be leveled after the distal end of the stylus contacts the measurable surface, calculates a displacement amount generated in the distal end of the stylus in an X-axis direction when the measuring device and the measured object are relatively displaced only by in the Z-axis direction; and levels the measuring arm by relatively displacing only by the measuring device and the measured object in the Z-axis direction by the relative displacement mechanism, and relatively displaces only by the measuring device and the measured object in the X-axis direction by the relative displacement mechanism at the same time.

Claims

1. A control method of a surface characteristic measuring apparatus, the surface characteristic measuring apparatus including: a measuring device that measures a surface characteristic of a measurable surface by profiling and scanning the measurable surface while in contact with the measurable surface of a measurable object; and a relative displacement mechanism that relatively displaces, three-dimensionally, the measuring device and the measurable object such that the measuring device scans and displaces along the measurable surface, the measuring device including: a measuring arm supported so as to be capable of performing a circular arc movement with a rotation axis as a fulcrum; a stylus provided to a distal end of the measuring arm; and a movement detector that detects displacement by the circular arc movement of the measuring arm, and with a vertical direction defined as a Z-axis direction and one direction orthogonal to the Z-axis direction defined as an X-axis direction, the control method of the surface characteristic measuring apparatus comprising: relatively displacing, by the relative displacement mechanism, the measuring device and the measurable object in the Z-axis direction such that the measuring device and the measurable surface approach each other; detecting when the distal end of the stylus is in contact with the measurable surface; calculating an amount ΔZ.sub.0 of relative displacement in the Z-axis direction of the measuring device and the measurable object that is required for the measuring arm to be leveled after the distal end of the stylus contacts the measurable surface; calculating a displacement amount ΔX.sub.0 in the X-axis direction generated in the distal end of the stylus when the measuring device and the measurable object are relatively displaced by ΔZ.sub.0 in the Z-axis direction; and leveling the measuring arm by relatively displacing the measuring device and the measurable object only by ΔZ.sub.0 in the Z-axis direction by the relative displacement mechanism, and relatively displacing the measuring device and the measurable object only by ΔX.sub.0 in the X-axis direction by the relative displacement mechanism at the same time.

2. The control method of the surface characteristic measuring apparatus according to claim 1, wherein: an axis parallel to the X axis and passing through the rotation axis is defined as a U axis, an axis parallel to the Z-axis and passing through the distal end of the stylus when the measuring arm is leveled is defined as a W axis, an intersection point of the U axis and the W axis is defined as a first principal point Q, the distal end of the stylus is defined as a second principal point D, a length H from the first principal point Q to the second principal point D is defined as a distal end projection length H, a length L from the rotation axis to the first principal point Q is defined as an arm length L, and wherein when a W coordinate value of the first principal point Q when the second principal point D comes into contact with the measurable surface is defined as Q.sub.w0, and the W coordinate value of the second principal point D is defined as D.sub.w0, the ΔZ.sub.0 is expressed as D.sub.w0+H, and the ΔX.sub.0 is obtained by the following formula: $\begin{array}{cc}\Delta X_0=\left(L-\sqrt{L^2-Q_{w0}^2}\right)-H.Math.\frac{Q_{w0}}{L}.& \left[\mathrm{Formula}4\right]\end{array}$

3. The control method of the surface characteristic measuring apparatus according to claim 2, further comprising temporarily stopping the relative displacement between the measuring device and the measurable surface when the detecting detects that the distal end of the stylus has contacted the measurable surface, the relative displacement between the measuring device and the measurable surface is temporarily stopped.

4. The control method of the surface characteristic measuring apparatus according to claim 1, further comprising temporarily stopping the relative displacement between the measuring device and the measurable surface when the detecting detects that the distal end of the stylus has contacted the measurable surface, the relative displacement between the measuring device and the measurable surface is temporarily stopped.

5. A control method of a surface characteristic measuring apparatus, wherein the surface characteristic measuring apparatus includes: a measuring device that measures a surface characteristic of a measurable surface by profiling and scanning the measurable surface while in contact with the measurable surface of a measurable object; and a relative displacement mechanism that relatively displaces, three-dimensionally, the measuring device and the measurable object such that the measuring device scans and displaces along the measurable surface, the measuring device includes: a measuring arm supported so as to be capable of performing a circular arc movement with a rotation axis as a fulcrum; a stylus provided to a distal end of the measuring arm; and a movement detector that detects displacement by the circular arc movement of the measuring arm, and with a vertical direction defined as a Z-axis direction and one direction orthogonal to the Z-axis direction defined as an X-axis direction, the control method of the surface characteristic measuring apparatus comprising: relatively displacing, by the relative displacement mechanism, the measuring device and the measurable object in the Z-axis direction such that the measuring device and the measurable surface approach each other; detecting when the distal end of the stylus is in contact with the measurable surface; continuing for a predetermined time the relative displacement of the measuring device and the measurable surface in the Z-axis direction after the distal end of the stylus contacts the measurable surface; calculating a displacement amount ΔX.sub.G in the X-axis direction generated in the distal end of the stylus during the predetermined time; and relatively displacing only by ΔX.sub.G the measuring device and the measurable object in the X-axis direction by the relative displacement mechanism while relatively displacing the measuring device and the measurable object in the Z-axis direction by the relative displacement mechanism.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

(2) FIG. 1 illustrates a surface characteristic measuring apparatus;

(3) FIG. 2 illustrates a configuration of an X-axis drive mechanism and a measuring device;

(4) FIG. 3 illustrates a measuring arm;

(5) FIGS. 4A and 4B illustrate a modification of the measuring arm;

(6) FIG. 5 is a functional block diagram of a control device;

(7) FIG. 6 is an explanatory diagram illustrating an auto-setting function;

(8) FIG. 7 illustrates an exemplary movement of the measuring arm when an auto-setting is performed;

(9) FIG. 8 is an explanatory diagram illustrating an issue when the auto-setting is performed;

(10) FIG. 9 is an explanatory diagram illustrating an issue when the auto-setting is performed;

(11) FIG. 10 provides an overview of the present embodiment;

(12) FIG. 11 provides an overview of the present embodiment;

(13) FIG. 12 is a flow chart describing a first embodiment;

(14) FIG. 13 is a flow chart describing a second embodiment; and

(15) FIG. 14 is a flow chart describing a second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(16) The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the forms of the present invention may be embodied in practice.

(17) An overview of the present embodiment is first described prior to describing specific embodiments. Please see FIG. 10. A driving amount of a Z-axis drive mechanism 250 necessary to level a measuring arm 272 after a stylus 273 comes in contact with a measured surface/measurable surface S is expressed by ΔZ.sub.0. ΔZ.sub.0 is equal to a descending amount of a forefront (distal) end D of the stylus 273 is descended from an initial position at a moment when a contact between the stylus 273 and a measured surface S is detected (refer to FIGS. 10 and 11). A position D.sub.w of the forefront end D of the stylus 273 is obtained from a tilted angle θ of the measuring arm detected by a W-direction movement detector 274. A position of the forefront end D of the stylus at a moment when the stylus 273 contacting the measured surface S is expressed by D.sub.w0. (In this example, D.sub.w0 is a negative number.) The driving amount ΔZ.sub.0 of the Z-axis drive mechanism 250 necessary to level a measuring arm 272 is expressed as:
ΔZ.sub.0=D.sub.w0+H
In this example, H is a length of the stylus 273.

(18) D.sub.w0 is obtained by a conversion formula using the tilted angle θ of the measuring arm 272 at the moment when the stylus 273 is in contact with the measured surface S and the length L from the rotation axis 272A of the measuring arm 272 to a first principal point Q (base end Q of the stylus 273). D.sub.w0=−(L sin θ.sub.0+H cos θ.sub.0) and ΔZ.sub.0 being a negative number express that the Z-axis drive mechanism 250 drives downward.

(19) Next, driving of the X-axis drive mechanism 260 is considered. A displacement in an X-axis direction is generated in a second principal point D (forefront end D of the stylus 273) by rotating the measuring arm 272 and the stylus 273 since the stylus 273 comes in contact with the measured surface S until the measuring arm 272 is leveled. First, a displacement in the X-axis direction generated in the first principal point Q (base end Q of the stylus 273) by the rotation of the measuring arm 272 is defined as ΔQ.sub.x0. Also, a displacement in the X-axis direction generated in the second principal point D (base end Q of the stylus 273) by the rotation of the measuring arm 273 is defined as ΔD.sub.x0. ΔQ.sub.x0 and D.sub.x0 are respectively obtained from the relationship illustrated in FIG. 11 and ΔX.sub.0 is obtained by adding both.

(20) $\begin{array}{cc}\begin{array}{c}\Delta X_0=\Delta Q_{x0}+\Delta D_{x0}\\ =\left(L-L\cos {\theta }_0\right)+H\sin {\theta }_0\end{array}& \left[\mathrm{Formula}1\right]\end{array}$

(21) Here, a position Q.sub.w0 of the first principal point Q (base end Q of the stylus 273) at the moment when the stylus 273 is in contact with the measured surface 273 is expressed by using the tilted angle θ of the measuring arm 272 at the moment when the stylus 273 is in contact with the measured surface S, and the length L (arm length Q) from the rotation axis 272A of the measuring arm 272 to the first principal point Q (base end Q of the stylus 273).
Q.sub.w0=−L sin θ.sub.0
Therefore, ΔX.sub.0 of the formula above can be modified as follows.

(22) $\begin{array}{cc}\begin{array}{c}\Delta X_0=\Delta Q_{x0}+\Delta D_{x0}\\ =\left(L-L\cos {\theta }_0\right)+H\sin {\theta }_0\\ =\left(L-L\sqrt{1-\frac{Q_{w0}^2}{L^2}}\right)+H.Math.\frac{.Math.Q_{w0}.Math.}{L}\\ =\left(L-\sqrt{L^2-Q_{w0}^2}\right)+H.Math.\frac{.Math.Q_{w0}.Math.}{L}\\ =\left(L-\sqrt{L^2-Q_{w0}^2}\right)-H.Math.\frac{Q_{w0}}{L}\end{array}& \left[\mathrm{Formula}2\right]\end{array}$

(23) Since Q.sub.w0 is a negative number, a mathematical sign before Q.sub.w0 is adjusted such that ΔX.sub.0 is a positive number.

(24) The Z slider 252 is displaced downward by ΔZ.sub.0 by the Z-axis drive mechanism 250 since the stylus 273 comes in contact with the measured surface S to the measuring arm 272 is leveled. During this time, a measuring device is simultaneously displaced by ΔX.sub.0 in the X direction by the X-axis drive mechanism. In other words, the measuring device is displaced and the auto-setting is performed not only in the Z direction but also in the X direction. As exemplified in FIG. 10, the auto-setting is completed without the second principal point D (forefront end D of the stylus 273) being displaced after the stylus 273 contacts the measured surface S.

(25) A description of embodiments of the present invention is given with reference to the drawings and to the reference numerals assigned to each component in the drawings.

First Embodiment

(26) FIG. 12 is a flow chart describing a first embodiment according to the present invention. The control operation is achieved by executing an auto-setting program stored in a memory 330 using a central controller 320, for example. In the auto-setting function, after the stylus 273 is arranged directly above a measuring start point, the Z slider 252 is slowly descended by the Z-axis drive mechanism 250 and the stylus 273 and a measured object/measurable object W come into contact. The contact between the stylus 273 and the measured object W is detected by 3 the W-direction movement detector 274 (ST110).

(27) When the contact between the stylus 273 and the measured object W is detected (ST110), at this time, descending the Z slider 252 is temporarily stopped (ST120). Then, a detection value θ.sub.0 of the W-direction movement detector 274 at the time is obtained (ST130). Further, using the detection value θ.sub.0, a W coordinate value Q.sub.w0 of the first principal point Q (base end Q of the stylus 273) and a W coordinate value D.sub.w0 of the second principal point D (forefront end D of the stylus 273) are calculated (ST130).

(28) When the measuring arm 272 is inclined from the horizontal position, the measuring arm 272 must be leveled by descending the Z slider 252. The measuring arm 272 is determined whether or not inclined. In this example, the determination whether the measuring arm 272 is inclined is performed by using the W coordinate value D.sub.w0 of the second principal point D (forefront end D of the stylus 273). In other words, a W coordinate value of the second principal point D (forefront end D of the stylus 273) when the measuring arm 272 is leveled is expressed as D.sub.w1 and a difference between the W coordinate value D.sub.w0 of the second principal point D (Forefront end D of the stylus) and this D.sub.w1 noted above is defined as an inclination index value ΔD.sub.w.
ΔD.sub.w=D.sub.w1−D.sub.w0
The inclination index value ΔD.sub.w is equivalent to the inclination of the measuring arm 272 in other words. When the inclination index value ΔD.sub.w exceeds ±1 micrometer (ST140: NO), the measuring arm 272 is determined to be inclined. Therefore, the measuring arm 272 must be leveled by further descending the Z slider 252.

(29) A descending amount ΔZ.sub.0 of the Z slider 252 necessary to level the measuring arm 272 is defined as ΔZ.sub.0. As described above, the descending amount ΔZ.sub.0 of the Z slider 252 that is necessary to level the measuring arm 272 is “D.sub.w0+H”, so ΔZ.sub.0=D.sub.w0+H is set (ST150).

(30) When the Z slider 252 is descended only by ΔZ.sub.0 till the measuring arm 272 is leveled, displacement in the X-axis direction generated in the second principal point D (forefront end D of the stylus 273) is defined as ΔX.sub.0. As described above,

(31) ΔX.sub.0 is ΔQ.sub.x0+ΔD.sub.x0=(L−L cos θ.sub.0+H sin θ.sub.0). When Q.sub.w0 is used, ΔX.sub.0 is expressed as below (ST160).

(32) $\begin{array}{cc}\begin{array}{c}\Delta X_0=\Delta Q_{x0}+\Delta D_{x0}\\ =\left(L-\sqrt{L^2-Q_{w0}^2}\right)-H.Math.\frac{Q_{w0}}{L}\end{array}& \left[\mathrm{Formula}3\right]\end{array}$

(33) Since ΔZ.sub.0 and ΔX.sub.0 are obtained in this way, the X slider 262 is displaced while the Z slider 252 is descended and the measuring arm 272 is leveled (ST170). In other words, the Z slider is descended only by ΔZ.sub.0 and the X slider 262 is displaced only by ΔX.sub.0. As exemplified in FIG. 10, the auto-setting is completed without the second principal point D (forefront end D of the stylus 273) being displaced after the stylus 273 contacts the measured surface S.

Second Embodiment

(34) A description of a second embodiment follows. The basic configuration of the second embodiment is similar to the first embodiment, however, in the second embodiment, while descending the Z slider, displacement of the X slider is compensated according to an actual descending amount of the Z slider. FIG. 13 is a flow chart describing a second embodiment. In the auto-setting function, after the stylus 273 is arranged directly above a measuring start point, the Z slider 252 is slowly descended by the Z-axis drive mechanism 250 and the stylus 273 and the measured object W come into contact. The contact between the stylus 273 and the measured object W is detected by the W-direction movement detector 274 (ST210).

(35) When the contact between the stylus 273 and the measured object W is detected (ST210), in the second embodiment, the Z slider 252 continues to descend (ST220). Simultaneously, when the contact between the stylus 273 and the measured object W is detected (ST210), a detection value θ.sub.0 of the W-direction movement detector 274 at the time is obtained (ST230). Then, the W coordinate value Q.sub.w0 of the first principal point Q (base end Q of the stylus 273) and the W coordinate value D.sub.w0 of the second principal point D (forefront end D of the stylus 273) are calculated. Further, in the second embodiment, ΔX.sub.0 is calculated using the detection value θ.sub.0 (ST230). In other words, when the Z slider 252 is temporarily descended (only by ΔZ.sub.0) from the current point in time until the measuring arm 272 is leveled, displacement ΔX.sub.0 in the X-axis direction generated in the second principal point D (forefront end D of the stylus 273) is obtained.

(36) Determination is made whether or not the inclination index value ΔD.sub.w exceeds ±1 micrometer, and when the inclination index value ΔD.sub.w exceeds ±1 micrometer (ST240: NO), the measuring arm 272 is determined to be inclined. In this case, the measuring arm 272 must be leveled by further descending the Z slider 252. Given this, a predetermined period of time (one second, for example) is counted (ST250). During this time, the Z slider continues to descend.

(37) After the predetermined period of time has elapsed, a detection value θ.sub.1 of the W-direction movement detector 274 is obtained again (ST260). Then, at this point, W coordinate value Q.sub.w1 of the first principal point Q (base end Q of the stylus 273) and W coordinate value D.sub.w1 of the second principal point D (forefront end D of the stylus 273) are calculated. Further, ΔX.sub.1 at this point is calculated using the detection value θ.sub.1 (ST260). In other words, when the Z slider 252 is temporarily descended (only by ΔZ.sub.1) from the current point in time until the measuring arm 272 is leveled, displacement ΔX.sub.1 in the X-axis direction generated in the second principal point D (forefront end D of the stylus 273) is obtained.

(38) The difference between the previous ΔX.sub.0 and the current ΔX.sub.1 after elapsing the predetermined period of time is defined as ΔX.sub.G (ST270).
ΔX.sub.G=ΔX.sub.0−ΔX.sub.1
This ΔX.sub.G refers to the displacement of the second principal point D (forefront end D of the slider 273) generated by descending the Z slider for a predetermined period of time. In ST280, the X slider 262 is displaced by ΔX.sub.G.

(39) The movement of the second principal point D (forefront end D of the stylus 273) generated by descending the Z slider 252 is canceled out by the displacement of the X slider, and therefore, the second principal point D (forefront end D of the stylus 273) hardly moves.

(40) Then, returning to the loop of the flow chart, the control loop (ST230-ST280) is repeated until the inclination index value ΔD.sub.w is in a range of ±1 micrometer (S240: YES). When the inclination index value ΔD.sub.w is in the range of ±1 micrometer (S240: YES), descending of the Z slider is halted (ST 290) and the auto-setting is completed. As exemplified in FIG. 10, the auto-setting is completed without the second principal point D (forefront end D of the stylus 273) being displaced after the stylus 273 contacts the measured surface S.

(41) There is a difference in drive speed between the Z-axis drive mechanism 250 and the X-axis drive mechanism 260 and synchronizing both movements is simply difficult. Therefore, in the first embodiment, when the speed of the Z-axis drive mechanism 250 is faster or slower than the speed of the X-axis drive mechanism 260, the displacement of the second principal point D (forefront end D of the stylus 273) may increase. In this regard, according to the second embodiment, since the adjustment cycle is repeated every predetermined time (ST230-ST280), the displacement of the second principal point D (forefront end D of the stylus 273) does not increase.

Third Embodiment

(42) A description of a third embodiment follows. The basic configuration of the third embodiment is common to the second embodiment, however, in the third embodiment, a coordinate value of a target position is provided for drive control of the X-axis drive mechanism. FIG. 14 is a flow chart describing a third embodiment. In the flow chart in FIG. 14, a corresponding step number (the lower two digits are the same and 200s is changed to 300s) given to a step performing the identical process with the flow chart in FIG. 13 (second embodiment), and a redundant description thereof is omitted. A description on dissimilar features from the second embodiment (FIG. 13) follows.

(43) In the flow chart in FIG. 14, when the Z slider 252 is descended and the contact between stylus 273 and the measured object W is detected (ST310), a detection value θ.sub.0 of the W-direction movement detector 274 at the time is obtained (ST330). Simultaneously, the detection value P.sub.X0 of an X-direction position detector 263 at the time is obtained (ST331). After this, descending the Z slider continues, and the difference between the previous ΔX.sub.0 and the ΔX.sub.1 after elapsing the predetermined period of time is obtained as ΔX.sub.G for every predetermined time (ST370).

(44) A target position X.sub.cp of the X-axis drive mechanism is obtained to drive the X slider by ΔX.sub.G. The target position X.sub.cp is a sum of P.sub.X0 obtained in ST331 and the previously noted ΔX.sub.G (ST371). The target position X.sub.cp is provided to the X-axis drive mechanism and the X slider is displaced to the target position X.sub.cp (ST381).

(45) Then, returning to the loop of the flow chart, the control loop (ST330-ST380) is repeated until the inclination index value ΔD.sub.w is in the range of ±1 micrometer (S340: YES). When the inclination index value ΔD.sub.w is in the range of ±1 micrometer (S340: YES), descending the Z slider is halted (ST390) and the auto-setting is completed. As exemplified in FIG. 10, the auto-setting is completed without the second principal point D (forefront end D of the stylus 273) being displaced after the stylus 273 contacts the measured surface S.

(46) In the second embodiment, the relative displacement is performed providing a drive pulse for a displacement amount ΔX.sub.G required for drive control of the X slider. In this case, when the control loop (ST230-ST280) is repeated, a cumulative error may be large. In this regard, in the third embodiment, the target position X.sub.cp is provided to drive control the X-axis drive mechanism, and therefore, a degree of positioning accuracy of the X slider is high.

(47) Moreover, the present invention is not limited to the embodiments described above, and may be modified as needed without departing from the scope of the present invention. In the embodiments described above, the stylus is installed facing downward and a description is provided which the measuring device is descended from top to bottom when the auto-setting is performed. On the contrary, there may be a case where the stylus is installed facing upward and the measuring device rising from bottom to top when the auto-setting is performed. (For example, a surface facing down may be measured). Even in this case, the present invention can be similarly applied.

(48) It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular structures, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

(49) The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.