JPS5841301A - Configuration measuring device - Google Patents

Abstract

PURPOSE:To perform highly accurate measurement, by a method wherein a supporting means which can elastically displace a spindle in an axial direction is supported by a supporting means which can be likewise displaced, and the first supporting means are displaced so that the measured pressure becomes a desired value in response to the displaced quantity of the spindle. CONSTITUTION:A spindle 11 is attached to a holding tool 13 through two parallel springs 12a and 12b so that it can be displaced in the axial direction of the spindle 11. The holding tool 13 is attached to a fixing member 15 through two parallel springs 14a and 14b so that it can be displaced in the axial direction of the spindle 11. A fixed plate spring 16 is provided at the intermediate part of the holding tool 13. The spindle 11 is displaced in the axial direction by the driving of a motor 19 through a rod 17 and the plate spring 16. The rotary angle of an encoder 20 is detected and the displaced quantity of the rod 17 is detected. Therefore the highly accurate measurement can be performed over a wide range without making the measuring pressure excessively large.

Description

[Detailed description of the invention] The present invention relates to a shape measuring instrument for measuring.

Various such shape measuring instruments are conventionally known, and for example, there is one using a measuring head as shown in FIG.

This probe is generally used as an electric micro, and consists of a spindle that is brought into contact with an object to be measured (not shown) and is fixed to the main body of the instrument via two parallel springs 2a and xb. A fixed member (not shown) is attached to the fixture 3, and the movable electrode holder fixed to the spindle 1 and the movable electrode 1 are provided in a fixed member (not shown) to have a displacement according to the surface shape of the object to be measured. Fixed part[! ! The surface shape of the object to be measured is measured by detecting changes in the oscillation frequency based on changes in capacitance between the two.

However, in the shape measuring instrument using the measuring head shown in Fig. 1, when the displacement of the spindle / is small, for example ±IO μm, the measurement pressure applied to the object by the spindle l is relatively small, but the displacement is small. When it exceeds lIIIa, the measurement pressure becomes considerably large and may damage the object to be measured. One possible way to solve this problem is to increase the dimensions of the parallel springs Ja, , and zb, or to decrease their spring constants, but in the former case, the entire measuring instrument would be large, and In the latter case, there is a problem that the mechanical response of the probe becomes poor. In other words, the natural frequency ν of the probe represents the mechanical response.

is the weight of spindle l, W = mg (m: mass, g:
acceleration of gravity), parallel spring Ja, and the spring constant of 2b is k, then ・=Up, pressure O! ! It is given by π. Here, in order to take the displacement amount of the spindle l up to 2 sieves and to suppress the measurement pressure to 3g or less, the spring constant k is set to k
= 5970. g 245oodyVcIW in C1l
However, in this way, the natural frequency ν.

is 'W=109 and ν. The frequency becomes medium Hz, and the mechanical response becomes extremely poor.

As described above, increasing the maximum displacement amount of the spindle l, that is, increasing the working distance or keeping the measured pressure low, and improving mechanical response have contradictory characteristics. Therefore, as shown in the first gJ, the spindle l is connected to two parallel springs Ja.

In the measuring head supported on the holder 3 fixed to the measuring instrument body via the rod b, on the one hand the spindle/
Although it is possible to minimize the inclination and wobbling of the motor, there is also the problem that the working distance cannot be maintained completely.

The purpose of the present invention is to solve the various problems mentioned above, and to provide a shape measuring instrument that has good mechanical response, can have a large working distance at a desired measurement pressure, and is appropriately configured to enable high-precision measurement. This is what I am trying to do.

The present invention provides a method for measuring the shape of the object by bringing the tip of the spindle into contact with the object to be measured, moving the two relative to each other, and detecting the amount of displacement of the spindle in the axial direction by a detection means. In the shape measuring instrument, the first supporting means elastically supports the spindle so as to be displaceable in the axial direction according to changes in the shape of the object to be measured, and the first supporting means is moved in the axial direction of the spindle. a second support means displaceably supported elastically on the fixed member; and a drive means for displacing the second support means in the axial direction of the spindle, the axis of the spindle being detected by the detection means. The first support means may be configured to be displaced via the drive means based on the amount of displacement in the direction so that the measurement pressure of the spindle against the object to be measured becomes a desired value. It is something to do.

The present invention will be described in detail below with reference to the drawings.

Figure m2 is a diagram showing the configuration of the main parts of the shape measuring instrument of the present invention. The spindle l/ has two parallel springs lJa, /
2b, it is attached to the holder 13 so as to be displaceable in the axial direction. For example, the shape of the parallel springs lλa and /b is circular,
Its center part is fixed to the spindle l/, and its peripheral part is fixed to the holder t3. The holder 13 is made up of two parallel springs/lIa
, /4 (b) is attached to the fixed member tS so as to be displaceable in the axial direction of the spindle //.These parallel springs /l
l5L, /4 (b holds spindle // A /J
For example, using a rectangular leaf spring having a sufficiently stronger spring constant than the parallel springs /Ja, /2b supported by the
The distance between /IIa and /Ilb is spring /2a and lcob
Make the distance sufficiently longer than the distance between A leaf spring 16 is provided in the middle between the spring /4'a and the spring b, with one end fixed to the holder 13 and extending parallel to the springs /4'a and /44b. The tip of the rod 17 is brought into contact with the other end of l≦. The rod 17 is screwed onto a support /I attached to a fixing member (not shown) so as to be displaceable in the axial direction of the spindle/l, and its rear end is connected to the output of a motor /'/ attached to a fixing member (not shown). Connected to the shaft and motor l
#jt is formed so that the holder t3 is displaced in the axial direction of the spindle l/ via the rod 17 and the leaf spring /J by driving the te. Further, a rotary encoder is connected to the output shaft of the motor 1 to detect the rotation angle of the motor 19 and the amount of displacement of the rod 17.

The means for detecting the amount of displacement in the axial direction of the spindle // is
As shown in FIG. 1, it is also possible to use an electrical detection means that detects the change in oscillation frequency due to a change in capacitance based on the displacement of the spindle, but in this example, a conventionally known Michelson interferometer or a Tokko Sho! ! The amount of displacement is optically detected using the length measuring interferometer proposed in Publication No. -2334/. For this purpose, a movable mirror 1 constituting a Michelson interferometer or a length measuring interferometer is attached to the rear end of the spindle l/.

In this example, the tip of the spindle / is brought into contact with the surface of the object to be measured n1, for example, a rotationally symmetrical aspherical lens, and this aspherical lens n is rotated in the α direction around its optical axis, and the center is centered around the approximate center of curvature. Rotate in the β direction from the vertical axis. Therefore, in this case, the spindle // will be displaced in the axial direction depending on the deviation of the aspherical lens n from a perfect spherical surface or the setting error.

FIG. 3 is a block diagram showing the configuration of an example of the drive control circuit of the shape measuring instrument shown in FIG. 2. The amount displayed by the interferometer counter 31 indicating the amount of displacement of the spindle l/ is converted into an analog amount by the D/A converter 3λ and is supplied to one input terminal of the differential amplifier 33. A predetermined reference voltage, which will be described later, is applied to the other input terminal of the differential amplifier 33 from the reference m-voltage generator 3V. Difference II The output of amplifier 33 is supplied to one input terminal of comparator 3j, and this comparator 3! The other input terminal of the rotary encoder corresponds to the rotation angle of the motor 1, that is, the displacement of the rod 17.
provides the output of The output of the comparator 3j is supplied to a seven-torque drive path 36, thereby driving and controlling the motor 19 so that the output of the rotary encoder becomes equal to the output of the differential multiplier 33.

The operation of an example of the shape measuring device shown in FIG. 1 and FIG. 3 will be described below. Suppose that the spindle l/ is displaced by a distance X1 in the direction of its axis, and the parallel spring /2a.

/2b spring constant, parallel spring /4Za, /4
If the spring constant of Zb is 2, then the spindle l/ha is 1
Since a measuring pressure of x = Pg is applied to the object to be measured n, and the same force is also applied to the parallel springs /Qa, /llb via the holder t3, the holder (l L, therefore the spindle l/ is kaX2 due to parallel spring /Fa, /Fb
It also receives a displacement equivalent to = Pg, and the total displacement mx of the spindle l/ is: 1 x = x engineering +
1) becomes 2.

Here, P is the desired measurement pressure that does not damage the object to be measured n.

The corresponding total displacement of spindle // is 1kXo, xo=po, <-; + -7) -1--
(2) Since 1 2 , the difference between the above equations (1) and (2), that is, X2 = X-Xo = (P-PO)9(y '' y )
--------('') Move the holder 13 to the spindle by a distance ax2' corresponding to 2 //
If the holder f of the spindle l/ is displaced in the axial direction of
The relative displacement amount with respect to 3 is always X. and always k
A desired measurement pressure of lXo=Po9 can be applied to the object to be measured n.

Therefore, in this embodiment, the above displacement amount X is applied from the reference TltEIE generator 31 shown in FIG. 3 to the other input terminal of the differential amplifier 33. By applying a reference voltage proportional to the differential amplifier 3
3, the difference between the reference voltage and the voltage proportional to the displacement amount X displayed on the interferometer counter 3/ is determined, and the motor 19 is driven and controlled via the motor drive circuit 36 so that this difference becomes zero. However, the rotary encoder is reset to zero at the start of measurement, and the proportionality constant between the displacement amount of the rod 17 and the displacement amount of the holder t3 is set appropriately.
The force of X'2 = k2 (X-Xo) is applied to the rod 17
and the leaf spring /≦ to the holder 13.

In this way, the amount of relative displacement of the spindle // with respect to the holder 13 can always be maintained at Xo, and therefore the measurement pressure of the spindle l/ with respect to the object to be measured n can be set in advance to a desirable P. can be maintained at g.

Also, since a small value of about 70 μm can be selected as Xo, if the measurement pressure at that time is /, then the parallel spring /
As 2a, /2b, the spring constant is ' = 10 : m '' 10 (dyn/
cm) later can be used, ν. == 160
The natural frequency of (H2) can be obtained. Therefore, extremely good mechanical response can be obtained.

Note that the present invention is not limited to the above-mentioned example, and can be modified or changed in many ways.

For example, in the above-described embodiment, the holder 13 is continuously displaced according to the displacement of the spindle l/, but the amount of displacement X of the spindle l/ is divided into several sections, and a corresponding one is assigned to each section. The holder 13 may be displaced stepwise within a range not exceeding the displacement amount X. In this way, even if the holder 13 is displaced via the leaf spring /6 within a range that does not exceed the displacement of the spindle //, 1411 will not affect the count value of the interferometer counter 3/. In other words, the amount of displacement of spindle l/ by parallel springs /Ja, /jb is X, and the accompanying parallel springs /l, /Il
If the displacement position of spindle l/ due to b is X2, the entire displacement jtX of spindle // is x=
(Xl), but here the parallel waves /≠a, /Qb
Therefore, the holder 13 should not exceed X +X, -X
. If it is displaced by , the parallel spring is /2a.

/2b displacement amount is X. So, parallel spring /2a, /
Jb and parallel spring/4! a , /4(only the amount of displacement shared by b changes, and the total amount of displacement is (x h + x
2-xo) +x. -X engineering + X2 does not change. Therefore, the count value of the interferometer counter 31 is not affected at all. In this way, when the displacement amount X of the spindle // is divided into several sections and the holder 13 is gradually displaced in a range not exceeding the displacement amount X corresponding to each section,
The amount of displacement of the spindle l/ with respect to the holder 13 also changes stepwise, and the measured pressure in each section can be relaxed to be approximately constant without becoming excessive. Note that in this case, some changes to the D/& converter 32 are required.

In addition, in FIG. 1, the rod 17 is displaced by a feed screw mechanism driven by the rotation of the motor 19, and thereby the holder t3 is displaced via the leaf spring lt.
It is also possible to modify 411 to displace the holder 13 by bending the plate spring l by the force of adsorption by a stone or the like, without using 7 or the motor 19. Further, in FIG. 2, the holder 13 is displaced via the leaf spring 16, but a rigid plate-like member may be used instead of the leaf spring 16, or such a leaf spring or The rod 17 may be brought into contact with the holder 13 and directly displaced without using a plate-like member. Furthermore, in Fig. 2, circular springs are used as the parallel springs /Ja, /2b, but rectangular springs can also be used in the same way as the parallel springs /Da, /2b. For /4Zb, a parallel spring can also be used. Similarly to /2&, /Jb, a circular spring can also be used.

As described above, in the present invention, the first support means that supports the spindle so as to be elastically displaceable in the axial direction,
The second support means supports the spindle so that it can be elastically displaced in the axial direction, and the first support means is displaced in accordance with the displacement lid of the spindle so that the measured pressure becomes a predetermined value. The movable lid of the spindle can be held for a sufficiently long time without increasing the measurement pressure, and highly accurate measurement can be performed without reducing mechanical response. Therefore, the shortcoming of short working distance in shape measuring instruments using parallel springs can be eliminated, and the object of the present invention can be effectively achieved.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of the main parts of a conventional shape measuring instrument, Figure 2 is a diagram showing the configuration of the main parts of the shape measuring instrument of the present invention, and Figure 3 is a diagram showing the shape measurement shown in Figure 2. FIG. 2 is a block diagram showing *t of an example of a drive control circuit for the device. //...Spindle, /ja, /Jb...Parallel spring, 13...Holder, /lI&, /4Zb...Parallel spring, /3...Fixing member, /Ni...Plate Spring, 17...
・Rod, /I...Support, /9...Motor,
...Rotary encoder, 1...Movable mirror, n...
・Measurement object, 3/...interferometer counter, 3λ...D
/& converter, 33... differential amplifier, 3q... reference voltage generator, 3S... comparator, 36... motor drive circuit.

Claims (1)

[Claims] L Shape measurement in which the tip of the spindle is brought into contact with the object to be measured and the two are moved relative to each other, and the amount of displacement in the axial direction of the spindle is detected by a detection means to measure the shape of the object to be measured. a first support means that elastically supports the spindle so as to be displaceable in the axial direction according to a change in the shape of the object to be measured; and a first support means that is movable in the axial direction of the spindle. a first support means elastically supported on a fixed member; and a drive means for displacing the first support means in the axial direction of the spindle, the displacement of the spindle in the axial direction detected by the detection means; The shape measuring device is characterized in that the first support means is configured to be displaced via the drive means so that the measurement pressure of the spindle against the object to be measured becomes a desired value based on the amount of measurement. .