JPS6359444B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shape measuring instrument that enlarges and records the surface shape of an object to be measured by moving the object to be measured and the stylus relatively. This invention relates to a device that electrically corrects arc errors that occur when moving up and down while tracing.

The schematic structure of a conventional shape measuring instrument will be explained with reference to FIG. A column 3 is fixed upright on the measuring table 1, and an X-direction moving device 5 is attached to the column 3 by rotating a vertical movement handle 4.
is moved in the vertical direction. A reference plate 7 is horizontally provided in the X-direction moving device 5, and by rotating a screw 9 connected to a motor 8, a moving plate 11 is moved along the X direction on the reference plate 7 via a nut 10. drive. The amount of movement of the moving plate 11 in the X direction at this time is detected by the X direction detector 12, and its output becomes the X direction input of the XY recorder 13. The X-direction detection device 6 is connected to the moving plate 11 described above, and is therefore driven in the X-direction.

A lever 15 is rotatably supported on the Y-direction device 6 by a fulcrum 14, and the amount of displacement when a stylus 16 attached to the tip of the lever moves up and down following the shape of the object 2 to be measured. is Y direction detector 1
7, and its output is detected by X-Y recorder 1
3 Y direction input.

In such a conventional shape measuring instrument, the tip 18 of the stylus 16 and the fulcrum 14 of the lever 15 are connected.
The configuration is such that the center position of the Y-direction detector 17, that is, the zero level, is when X'-X'' is parallel to the upper surface of the reference plate 7 of the X-direction moving device 5. Needle tip 18 and fulcrum 1
If the measurement surface of the object to be measured 2 is placed approximately on the line connecting the points 4 and 4, measurements can be made with the smallest arc error caused by the rotation of the stylus tip 18 around the fulcrum 14, or the This is because this is a necessary condition when correcting arc errors using a mechanism.

However, with such a conventional device, when measuring the shape of a large object to be measured 2 as shown in FIG. 2, the Y-direction detection device 6 collides with the object to be measured 2, making measurement practically impossible. .

Conventionally, when measuring the shape of a large object, a long lever 15 is attached to match the length of the object as shown in Fig. 3, and the Y direction detection device 6 is driven in the X direction. It has been considered to perform measurements without hitting the object to be measured 2 even when the object is being measured.

However, in this conventional device, the entire measuring device is large, and the measuring table 1 must be made large accordingly, which is disadvantageous both in terms of space and economy. In addition, with this conventional device that uses a longer lever, the measuring force increases, and if the measuring force is balanced with a weight etc. to reduce the measuring force, the responsiveness of the detector deteriorates, and the lever becomes deflected, which causes measurement errors. As the sensitivity of the detector decreases, it is necessary to correct it with an electric circuit or change the fulcrum position.Since the amount of arc error changes, it is necessary to correct it mechanically or electrically, but it is not easy.
There were other drawbacks.

As another conventional method, a Y-direction detector with a large measurement range is made, the object to be measured 2 is positioned below the Y-direction detection device 6 as shown in FIG. 4, and the lever 15 is moved as shown by the dotted line. It is not inconceivable to take measurements at a large tilt. However, the arc error increases in proportion to the square of the displacement of the tip of the stylus. In other words, h is the displacement of the tip of the stylus,
If l is the lever length, generally the arc error δ is δ=
l−√ ² − ² , and by expanding this, approximately δ
It is calculated as = h ² /2·l. Therefore, when measuring using the conventional method described above, measurements are taken at both ends, which are part of the measurement range of the detector, and the arc error increases accordingly. The error after correction is also large. In addition, in this method, when the line connecting the tip of the stylus and the fulcrum is horizontal, the output of the Y-direction detector is zero, so if the lever 15 is tilted significantly and the measurement is made, there will be a large output on the negative side, and the shape signal will be They will be superimposed. Therefore, in order to record the shape so that it fits on the recording paper, operations such as applying an appropriate electrical bias voltage are required. Furthermore, this measuring method has various drawbacks, such as the fact that, depending on the shape of the object to be measured, the tip of the lever 15 may hit the object to be measured, making it impossible to measure because the lever 15 is tilted significantly.

This invention solves the above-mentioned drawbacks of the conventional device, and is configured so that the line connecting the stylus tip 18 and the fulcrum 14 is not parallel to the reference plate 7, that is, the stylus tip 18 is aligned with the X'-X'' line. By configuring the device to be positioned further down, it is possible to measure the shape of a large object to be measured as shown in Figure 2, and to draw an enlarged recording figure that corrects the X-direction error caused by such a configuration. The present invention provides a shape measuring instrument that makes it possible to

The present invention will be explained below with reference to the drawings. FIG. 5 is a partial explanatory diagram of the Y-direction detection device of the shape measuring instrument according to the present invention, where 20 is the object to be measured placed on the measuring table 1, and 21 is driven in the XX direction along the reference plane 22. 23 is a linear lever rotatably supported by a fulcrum 24;
5 is a stylus attached to the tip of the lever 23;
Reference numeral 6 denotes a Y-direction detector such as a differential transformer that measures the amount of displacement when the stylus 25 moves up and down following the shape of the object to be measured 20 via the lever 23.

As is clear from the figure, in the shape measuring instrument of the present invention, the tip of the stylus 25 is located below the fulcrum 24, and the straight line shown by the dashed line in the figure connecting the tip of the stylus 25 and the fulcrum 24 is The Y-direction detection device 21 is not parallel to the reference plane 22 and is configured so as not to collide with the object 20 to be measured.

The principle of the present invention will be explained with reference to FIGS. 5 and 6. FIG. 6 is an enlarged explanatory view of the lever 23 and stylus 25 portions of FIG. 5. In the figure, the fulcrum of the lever 23 is O, and the lever is placed parallel to the reference line direction XX. Hereinafter, a line parallel to X--X will be abbreviated as a horizontal line, and a line parallel to the Y-line that intersects at right angles to the X--X line will be abbreviated as a vertical line. Here, let the position of the tip of the stylus 25 at this time be P, and let J be the intersection of the vertical line passing through P and the horizontal line passing through O. When the tip of the stylus is at P, the Y-direction detector 26 is set to zero level.

Next, when the stylus tip is moved up and down h in the Y direction, let the moving points of the stylus tip be Q and R, draw the tangent to the trajectory circle of the stylus tip at point P, and subtract the transverse tangent from Q and R. , the intersection of the tangent and this transverse tangent is Q′,
Let it be R′. Also, the intersection points of the vertical line passing through Q and Q′ and the horizontal line passing through O are I and H, and the vertical line passing through P and R,
Let T be the intersection with the horizontal line passing through R'.

At this point, the lever pivots upward and the tip of the stylus
When it is at a point, the fulcrum is O, so IJ is the arc error (δ ₁ ) of the X value. On the other hand, when the lever turns downward and the tip of the stylus is at point R, TR is the arc error (δ ₂ ), δ ₁ is directed to the left in the drawing with respect to the vertical line passing through point P, and δ ₂ is When facing right, one side is (+) and the other side is (-). Here at the same angle h
Considering when it goes up and down, as shown in the figure, |δ ₂ |>
|δ ₁ |, and since the detector is at zero level at point P,
Its polarity is output in the opposite direction. Therefore, by determining the polarity of the output of the Y detector and adding or subtracting δ ₁ and δ ₂ , which are created by a separately provided circuit for calculating arc error, from the X value of the amount of movement in the X direction, the arc error should be obtained. It is. As one method for calculating the arc error, h ² /2·l is used approximately as described above.

However, in the conventional method, the tip of the stylus is located on the same horizontal line as the fulcrum O, and this is taken as the zero level, so the lever rotates up and down based on the state of zero arc error, so the fluctuation range of the arc error It is also considered small. On the other hand, when point P is located below as in the present invention, it is necessary to correct a relatively large error. Therefore, in the present invention, the calculation method has been changed from the conventional concept.

In FIG. 6, consider a case where the tip of the stylus is raised by h. If the true arc error component at this time is δ ₁ , then δ ₁ = IJ = JH − HI Here, if JH is the angular error component and HI is the second correction component ε ₁ , then above point P, δ ₁ = Upper angle error component (JH) −
ε ₁ Similarly, in the downward direction, δ ₂ = TR′ + R′R = Downward angular error component (TR′) + ε ₂ Here, ΔPQ′Q≡ΔPR′R, so SP: d = h: PU (PU = √ ² − ² ) ∴ SP=TR′=h·d/√ ² − ² That is, the positions of Q′ and R′ can be easily and accurately determined as quantities proportional to the amount of displacement d.

Next, consider second-order corrections ε ₁ and ε ₂ which are relatively small high-order errors. This can be determined using the following formula.

ε ₁ =PU+Q′Q−IO (IO=√ ² −(−) ² ) ε ₁ =√ ² − ² +h・d/√ ² − ² −√ ² −(−) ² ε ₂ =PU−TR′− RK (RK=√ ² −(+) ² ) ε ₂ =√ ² − ² −h・d/√ ² − ² −√ ² −(+) ² ε ₁ and ε ₂ are not the same size, but the sixth As is clear from the figure, they are approximately the same size.

In other words, the length of the lever now is l=350mm, d=
When calculated at 50 mm, the difference between ε ₁ and ε ₂ is 0.1 μm at h=5 mm,
When h=10mm, it is 1.2μm, and when h=20mm, it is 9.8μm. And since the magnification when recording with a normal shape measuring device is 10 times or less, the error on the recording paper is h = 20 mm.
It is less than 0.098 mm, and a difference of this degree can be ignored by a practical shape measuring instrument. Therefore, it can be seen that ε ₁ ≒ ε ₂ based on the absolute value of the displacement of the Y detector.

Therefore, using the conventionally known broken line function method,
A method is used to determine the second correction value ε for the Y detection amount. In other words, actually calculate ε for h,
An electronic calculation circuit is constructed by drawing a function curve, arranging a plurality of straight lines approximating it, and assuming that ε changes in a linear relationship with h within a specific range.

An embodiment for carrying out the above error correction method will be described with reference to FIG.

The Y signal from the Y detector 26 is directly input to the XY recorder 30, and as in the conventional system shown in FIG. Determine if it is below. In the case of the conventional method, a correction value is calculated in the upper correction circuit 32 or lower correction circuit 33 depending on whether the signal of the polarity discrimination circuit 31 is above or below the zero level, and the correction value is calculated with the X value signal in the calculation circuit 34. -Y recorder 3
It was recorded and displayed as 0. On the other hand, in the present invention, based on the determination made by the polarity determining circuit 31, a signal instructing to convert or not to convert the polarity of the output of the correction component calculation circuit shown below is issued. Here, the circuits 35 and 36 create the above-mentioned angular error component and secondary correction component from the Y signal, and send them to the arithmetic circuit 37 with or without reversing the polarity according to the command from the discrimination circuit. The data is subtracted, corrected, and entered into the recorder 30.

In addition, although the case where the tip of the stylus is located below the horizontal line passing through the fulcrum has been explained above, the stylus is rotated 180 degrees so that the tip is located above the fulcrum, and the pressure measurement is performed upward. It is also possible to measure the shape of the lower surface of the object to be measured. In this case, it would be better to think about it by reversing Fig. 6.

In addition, in the above implementation, the enlarged recording figure is
Although the description has been made regarding drawings on paper using a Y recorder, the present invention is not limited to this, and may also be recorded using an XY plotter or displayed on a cathode ray tube.

As described in detail above, according to the present invention, the shape measuring device has a structure in which the tip of the stylus is positioned below or above the lever fulcrum, and an error correction method is adopted to narrow the range of the shape of the object to be measured. It can be measured widely and accurately and quickly.
Furthermore, in the present invention, unlike conventional levers, there is no requirement that the tip end be located on the fulcrum line, so the structure of the lever can be simplified compared to conventional levers.

[Brief explanation of the drawing]

Figures 1, 2, 3, and 4 are explanatory diagrams of the conventional technology, Figure 5 is a partially omitted side view of the present invention, Figure 6 is an explanatory diagram of the principle of the present invention, and Figure 7 is the conventional diagram. FIG. 8 is a block diagram of the correction circuit of the present invention. 12... X direction displacement detector, 20... Measured object, 26... Y direction displacement detector, 23... Lever, 24... Fulcrum, 25... Stylus, 30... X-
Y recorder, 31... Polarity discrimination circuit, 35... Angle error correction circuit, 36... Secondary correction circuit, 37...
...Arithmetic circuit.

Claims (1)

[Claims] 1 In a device that moves the object to be measured and the stylus relatively in the X direction and measures the shape of the object's surface by moving the tip of the stylus up and down (Y direction), the tip of the stylus is moved in the X direction of the lever fulcrum. A stylus lever positioned below or above the direction line and this lever
The Y value of the tip point P when the direction matches is set to zero level, and from this state, the angular error component value calculated according to the Y value of the vertical movement of the tip and the secondary correction component value are outputted as Y. Add or subtract according to the polarity of the value and
A shape measuring device consisting of a circuit that corrects circular errors in detected values.