JP2012068208A - Shape measurement sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape measurement sensor for detecting a load to be imposed on the top end of a probe with high sensitivity regardless of the composition of the probe.SOLUTION: The shape measurement sensor for measuring the surface shape of an object to be detected includes: a probe 11 supported so as to slide in the self-axial direction for following up the surface shape of the object to be detected; a hydrostatic bearing 12 for supporting the probe to slide to the axial direction while supplying fluid to the probe; and an acceleration sensor 16 for detecting a load to be imposed on the top end of the probe by monitoring the change of the dynamic state of the fluid.

Description

  The present invention relates to a shape measurement sensor used for contact-type surface shape measurement, and more particularly to a shape measurement sensor that can suitably detect a load applied to a probe that contacts the surface of a test object.

  Conventionally, as a device for measuring the surface shape of an optical-related element such as a lens or a mold, a contact scanning measurement method in which a probe (stylus) is brought into contact with the surface of a test object such as an optical-related element to follow it. Is used as a contact type shape measuring sensor (hereinafter sometimes simply referred to as “shape measuring sensor”).

In the surface shape measurement using the shape measurement sensor, it is preferable that the probe tip can be smoothly scanned on the surface of the object to be measured, which is preferable.
However, in reality, friction occurs between the tip of the probe and the surface of the test object, so that a load due to frictional force is applied to the tip of the probe. If this load becomes too large, an excessive force is applied to the probe in the direction intersecting the axis, which lowers the measurement accuracy and also causes the probe to be damaged or damaged.

  In order to cope with this problem, in the surface shape measuring machine described in Patent Document 1, the load is increased by measuring the positional change of the mirror surface with a laser interferometer using the base end of the probe that does not contact the object as a mirror surface. An attempt is made to detect shake of the probe due to such a situation.

JP 2007-64670 A

  However, in the detection mechanism in the surface shape measuring instrument of Patent Document 1, when the probe has a high rigidity, the mirror surface at the base end is less likely to be displaced than the tip side, and laser interference is not required unless a considerable load is applied to the tip. The shake cannot be detected by the total. Therefore, there is a problem that it is difficult to detect a load that causes a minute blur or tilt at the tip of the probe.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a shape measuring sensor capable of detecting a load applied to the tip with high sensitivity regardless of the configuration of the probe.

  The present invention is a shape measurement sensor for measuring the surface shape of a test object, and is supported so as to be slidable in the axial direction of the test object, and the surface shape of the test object by sliding in the shaft method. A probe that follows the probe, a bearing that supports the probe so as to be slidable in the axial direction while supplying a fluid toward the probe, and a tip of the probe by monitoring a change in dynamics of the fluid And a load detection unit for detecting a load applied to the unit.

The load detection unit may be an acceleration sensor that monitors a change in the natural frequency of the probe accompanying a change in the dynamics of the fluid.
Further, at least one of the detection directions of the acceleration sensor may be set in parallel with the scanning direction of the probe.

  The load detection unit may be an acoustic sensor that monitors a change in sound pressure accompanying a change in fluid dynamics, or a mechanism that monitors a change in air volume or wind pressure accompanying a change in fluid dynamics. Also good.

  According to the shape measuring sensor of the present invention, the load applied to the tip can be detected with high sensitivity regardless of the configuration of the probe.

It is a figure which shows schematic structure of the shape measurement sensor of one Embodiment of this invention. It is a figure which shows the probe and static pressure bearing of the same shape measurement sensor in a partial cross section. It is a figure which shows the state in which the load was applied to the same probe. It is a figure which shows the outline | summary of the experiment using the same shape measurement sensor. It is a graph which shows the detected value of the acceleration sensor in the same experiment. It is a graph which shows the detected value of the electrostatic capacitance sensor in the same experiment.

  An embodiment of the present invention will be described with reference to FIGS. Unless otherwise specified, “front” and “back” refer to the negative and positive directions of the Z-axis shown in FIG. 1, respectively.

  FIG. 1 is a diagram illustrating an example of a shape measuring sensor 1 according to the present embodiment. The shape measuring sensor 1 measures the surface shape of a test object, and includes a stylus part 10 to which a probe 11 is attached, a test object holding part 20 on which the test object 100 is supported, and a stylus. The Y-axis drive mechanism 30 for moving the slave unit 10, the X-axis drive mechanism 40 for moving the test object holding unit 20, the overall operation control of the shape measuring sensor 1, and the processing of the acquired surface shape data And a personal computer 50 for performing the above.

The stylus part 10 includes a probe 11 that follows the surface shape of the test object by sliding in its own axis method, a hydrostatic bearing (bearing part) 12 through which the probe 11 is inserted, and a probe 11. And an inclination angle adjusting unit 13 for adjusting the inclination angle.
The probe 11 can be appropriately selected and used in a known configuration having a tip portion 11A in contact with the test object 100 and a substantially cylindrical shaft portion 11B having the tip portion 11A attached to the tip side. The hydrostatic bearing 12 is inserted into the hydrostatic bearing 12 so that it can slide smoothly. The hydrostatic bearing 12 is fixed on the base flat plate 14 so that the distal end portion 11A of the inserted probe 11 faces the front where the test object 100 is disposed. A displacement meter 15 for detecting the amount of displacement of the probe 11 is attached to the rear end side of the shaft portion 11B where the tip portion 11A is not attached.

  FIG. 2 is a diagram for explaining the structure of the probe 11 and the hydrostatic bearing 12, and shows the probe 11 as viewed from above the shape measuring sensor 1 (Y axis positive side shown in FIG. 1) and in a partial cross section. Yes. The hydrostatic bearing 12 has a substantially rectangular parallelepiped outer shape, and has a through hole 12A having a circular cross section in the radial direction. The shaft portion 11B of the probe 11 is inserted through the through hole 12A. A clearance of about several micrometers (μm) is secured between the inner surface of the through hole 12A and the outer peripheral surface of the shaft portion 11B on both sides in the radial direction of the through hole 12A.

  Further, an air supply line 12B is connected to the hydrostatic bearing 12, and a gas (fluid) such as air is supplied from a supply source (not shown). The supplied gas passes through a pipe line (not shown) formed in the hydrostatic bearing, and is a space between the through hole 12A and the shaft portion 11B from a large number of air supply holes (not shown) formed on the inner surface of the through hole 12A. Supplied as an air flow. By this air flow, the frictional force generated between the probe 11 and the hydrostatic bearing 12 is reduced, and the probe 11 is supported so as to be able to slide smoothly in the through hole 12A of the hydrostatic bearing 12.

  An acceleration sensor (load detection unit) 16 for detecting a load applied to the distal end portion 11 </ b> A of the probe 11 is attached to the hydrostatic bearing 12. As the acceleration sensor 16, a known sensor can be appropriately selected in consideration of sensitivity and the like. The acceleration sensor 16 is preferably installed such that the direction of acceleration to be detected (detection direction) is a direction that intersects the axis of the through-hole 12A, and the detection direction is orthogonal to the axis and the scanning direction of the probe 11 More preferably, it is installed so as to be in parallel with each other. In the shape measurement sensor 1, the scanning direction is a direction parallel to the X axis shown in FIG. 1, and thus the acceleration sensor 16 is attached to either side surface of the hydrostatic bearing 12 at both ends in the X axis direction.

  The tilt angle adjustment unit 13 includes a front fulcrum 13A and an expandable unit 13B that can be expanded and contracted in the Y-axis direction shown in FIG. 1, and causes the probe 11 to slide forward by changing the tilt angle of the probe 11. Then, the surface of the test object 100 is brought into contact. For example, a mechanism including a piezoelectric actuator or a screw and an angle adjusting member can be employed as the extendable portion 13B.

The specimen holding unit 20 includes a base 21 attached on the base 2 and a swinging part 22 attached to the base 21. The test object 100 is fixed to the swinging portion 22 and is disposed to face the probe 11. The oscillating part 22 is oscillatable with respect to the base 21, and by changing the positional relationship between the oscillating part 22 and the base 21, a test object attached to the oscillating part 22 as will be described later. The angle formed by 100 and the probe 11 can be changed.
In the present embodiment, the surface to be measured is a spherical object, but the shape of the surface to be measured is not particularly limited.

  The Y-axis drive mechanism 30 is provided between the stylus part 10 and the base 2 and moves in the Y-axis direction to maintain the inclination angle of the probe 11 set by the inclination angle adjustment part 13. The stylus part 10 can be moved up and down as it is. A displacement meter 31 for detecting the amount of movement of the Y-axis drive mechanism is provided behind the Y-axis drive mechanism 30.

  The X-axis drive mechanism 40 is provided between the base 21 of the test object holding unit 20 and the base 2 and moves in the X-axis direction so that the entire test object holding unit 20 is moved in the X-axis direction. Can be moved. In front of the X-axis drive mechanism 40, a displacement meter 41 for detecting the displacement of the specimen holding unit 20 in the X-axis direction is provided.

The personal computer 50 includes an input unit 51 that receives user input, instructions, and the like, and a display unit 52 that displays various types of information. The personal computer 50 is connected to the tilt angle adjusting unit 13, the swinging unit 22, the Y-axis drive mechanism 30, and the X-axis drive mechanism 40, and can control the operations of these mechanisms. Further, the personal computer 50 is also connected to each of the displacement meters 15, 31, and 41, receives these detection values, reconstructs them into a plurality of partial surface shape data of the test object 100, and each partial surface shape. A process of connecting the data and obtaining the surface shape data of the entire test object 100 is performed.
Further, although not shown, the personal computer 50 is also connected to the air supply line 12 </ b> B and the acceleration sensor 16. Gas supply to the hydrostatic bearing 12 is controlled by the personal computer 50, and the detection value of the acceleration sensor 16 is sent to the personal computer 50 as needed.

The operation at the time of use of the shape measuring sensor 1 having the above configuration will be described below.
First, the user supports and fixes the test object 100 on the swinging part 22 of the test object holding part 20 so that the surface on which the shape measurement is performed faces the stylus part 10. Next, the user operates the inclination angle adjusting unit 13 via the input unit 51 and moves the rear part of the base flat plate 14 upward while supplying gas to the hydrostatic bearing 12. Then, the base flat plate 14 is inclined with the fulcrum 13A as a fulcrum, and the probe 11 held by the hydrostatic bearing 12 slides smoothly in the hydrostatic bearing 12 by its own gravity. By sliding, the tip of the probe 11 moves forward and comes into contact with the surface of the test object 100 and stops.

  In this state, the personal computer 50 drives the X-axis drive mechanism 40 and the Y-axis drive mechanism 30 to move the test object 100 and the probe 11 relative to each other, thereby causing the probe 11 to scan the surface of the test object 100. . The scanning direction of the probe 11 is a direction parallel to the X axis, and the entire surface of the test object 100 is scanned while changing the height of the tip portion 11A by the Y axis driving mechanism 30. Detection values of the displacement meters 15, 31 and 41 are input to the personal computer 50. During the scanning of the probe 11, the dynamic state of the gas supplied into the through hole 12 </ b> A of the hydrostatic bearing 12 is constantly monitored by the acceleration sensor 16.

  When an excessive frictional force is generated between the test object 100 and the tip 11A of the probe 11 when scanning the test object 100 and the probe 11 relative to each other, as shown in FIG. The scanning movement of 11 </ b> A is hindered by the frictional force, and the probe 11 tilts within the hydrostatic bearing 12. Although the initial inclination is slight (FIG. 3 is exaggerated for easy understanding of the change), if this state is left as it is, the inclination of the probe 11 becomes gradually larger and excessively applied to the distal end portion 11A. This causes an abnormal state where the load is applied, causing damage to the tip 11A and the surface of the test object 100.

In the shape measuring sensor 1, when the probe 11 is tilted, the shape of the gap between the inner surface of the hydrostatic bearing 12 and the outer peripheral surface of the shaft portion 11B changes even if the tilt amount is very small. As indicated by arrows in FIG. 3, the dynamics of the airflow of the gas supplied from the air supply line 12B to the gap changes. When the dynamics of the airflow change, the natural frequencies of the probe 11 and the hydrostatic bearing 12 change, and the change is detected by the acceleration sensor 16. When the amount of change in the natural frequency exceeds a predetermined threshold, information such as a message or an image that alerts the user is displayed on the display unit 52 of the personal computer 50.
The user recognizes from the display on the display unit 52 that an excessive load is applied to the distal end portion 11A, and pauses the scanning of the probe 11 if necessary, or moves the probe 11 to a sharp tip, for example. And take measures such as exchanging with a diamond stylus or the like that does not easily cause friction with the specimen.

According to the shape measurement sensor 1 of the present embodiment, the acceleration sensor 16 has the inside of the through hole 12 </ b> A of the hydrostatic bearing 12 in accordance with the inclination of the probe 11 caused by the friction between the surface of the test object 100 and the tip 11 </ b> A of the probe 11. This is detected by monitoring the change in the dynamics of the gas flow supplied to the gas.
As described above, since there is only a clearance of about several μm between the shaft portion 11B and the through-hole 12A, even if the probe 11 is slightly tilted, the airflow dynamics greatly change.
Therefore, compared to monitoring the displacement amount of the proximal end of the probe, it is possible to remarkably improve the detection sensitivity of the load at the distal end portion accompanying the inclination of the probe. And by recognizing the load and taking the necessary action as soon as possible, the situation where the probe and the surface of the test object can be damaged can be suitably prevented, and an environment where the shape can be measured with high accuracy is preferable. Can be held in.

The inclination of the probe 11 is caused by an excessive frictional force generated when the test object 100 and the probe 11 are relatively moved, and greatly affects the scanning direction.
Therefore, the detection direction of the acceleration sensor 16 is preferably a direction intersecting the axis of the through hole 12A, and more preferably a direction parallel to the scanning direction of the probe 11. By doing so, the load detection sensitivity can be further improved. In addition, if a three-dimensional acceleration sensor is used, any one of the three axes satisfies the above-described conditions, and therefore, it is possible to perform detection with high sensitivity without having to strictly consider the installation direction.

  As described above, the shape measurement sensor 1 of the present embodiment has been described. However, in order to examine the detection sensitivity of the shape measurement sensor 1, an experiment was performed in comparison with a conventional detection mechanism, and the results are shown below.

  FIG. 4 is a diagram for explaining the outline of the experiment. In the shape measurement sensor 1 including the acceleration sensor 16, a capacitance sensor 60 for monitoring the amount of displacement is attached to the proximal end of the shaft portion 11 </ b> B of the probe 11. The capacitance sensor 60 detects the displacement of the probe 11 in the axial direction as indicated by reference numeral 60A in FIG. 4 and the displacement in the direction substantially orthogonal to the axis of the probe 11 as indicated by reference numeral 60B. Two types of arrangements were examined.

  Using the motor and the striking member (both not shown) at the predetermined portion P1 of the tip portion 11A, vibration is applied five times at a cycle of about 1 second, and the probe 11 is detected by the acceleration sensor 16 and the capacitance sensor 60. The natural frequency of was monitored.

  FIG. 5 shows the detection result of the acceleration sensor 16. In the graph, the waveform indicated by reference sign S1 is white noise generated by airflow in a state where no external force is applied to the probe 11. The arrow shown in the upper part of the graph is the timing at which the vibration is applied to the predetermined location P1, and it can be seen that the detection value of the acceleration sensor 16 has greatly changed to twice or more the value of white noise.

  FIG. 6 shows the detection result of the capacitance sensor 60. The waveform indicated by reference sign S <b> 2 in the graph is white noise in the capacitance sensor 60. In the capacitance sensor 60, the detected value did not change sharply with respect to the first vibration, but at other timings, each detected value is observed as a peak.

As can be seen from the fact that the scale of the vertical axis is different between FIG. 5 and FIG. 6, it is not possible to compare the sensitivity even if the detected values of the two are directly compared. Therefore, when the standard deviation is calculated for each of the two graph values, the acceleration sensor 16 has a value of about 0.5136, and the capacitance sensor 60 has a value of about 0.00375. The ratio (sensitivity) between the absolute value of the actually measured value and the standard deviation was 9.735 (= 5 / 0.5136) and 5.33 (= 0.02 / 0.00375), respectively. That is, compared to monitoring the displacement amount of the probe base end, the method of monitoring the dynamic change of the air flow inside the hydrostatic bearing 12 with the acceleration sensor is 9.735 / 5.33 = 1.83 times the sensitivity. It was shown to have
Regarding the capacitance sensor 60, the graph waveform of the detected value hardly changed between the arrangement of 60A and the arrangement of 60B, and the calculated sensitivity was the same.

  The shape measuring sensor of the present invention is used so that an abnormal state in which an excessive load is applied to the probe is automatically discriminated by, for example, the personal computer 50 and the warning information is displayed on the display unit 52 or the scanning of the probe is automatically stopped. In the case of configuring, in order to reliably prevent malfunction, it is preferable to set a threshold value that is about five times the standard deviation in the detection value of the load detection unit. In such a setting, the above abnormal state can be detected without any problem if the sensitivity is about the acceleration sensor 16, but the abnormal state may not be detected if the sensitivity is about the capacitance sensor 60. sell. In order to prevent this, the threshold value may be lowered. However, if the threshold value is lowered, false detection increases accordingly, which is not preferable. As described above, the shape measuring sensor according to the present invention includes the load detection unit that monitors the dynamics of the fluid in the bearing unit, so that the load applied to the tip of the probe and the occurrence of an abnormal state with sufficient sensitivity to withstand automatic discrimination. Can be detected.

Although one embodiment of the present invention has been described above, the technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the example in which the information is displayed on the display unit when the detection value of the acceleration sensor is equal to or greater than the predetermined threshold, or the example in which the probe scanning is automatically stopped has been described. Instead of this, the detection value of the acceleration sensor may be always displayed on the display unit so that the user can recognize and determine the abnormal state of the probe.

  Further, the mechanism of the load detection unit is not limited to the above-described acceleration sensor, and the mechanism of the fluid in the bearing unit may be monitored by another mechanism. For example, instead of an acceleration sensor, a sound pressure generated by an air pressure meter, an air flow meter, or the like that monitors the wind pressure or air volume at the end of the through hole of the hydrostatic bearing, or a gas supplied into the through hole is monitored. A mechanism such as an acoustic sensor may be used.

  Furthermore, the bearing portion that supports the probe is not limited to the above-described hydrostatic bearing, and may be, for example, a linear guide. In this case as well, the load applied to the tip of the probe can be detected with high sensitivity by monitoring the fluid dynamic change in the gap or the like existing between the probe and the rail.

  In addition, the above-described configurations can be appropriately combined without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Shape measuring sensor 11 Probe 11A Tip part 12 Hydrostatic bearing (bearing part)
16 Acceleration sensor (load detector)
100 specimen

Claims (5)

A shape measurement sensor for measuring the surface shape of a test object,
A probe that is slidably supported in its own axial direction and follows the surface shape of the test object by sliding in the axial method;
A bearing that supports the probe so as to be slidable in the axial direction while supplying fluid toward the probe;
A load detection unit that detects a load applied to a tip of the probe by monitoring a change in dynamics of the fluid;
A shape measuring sensor comprising:   The shape measurement sensor according to claim 1, wherein the load detection unit is an acceleration sensor that monitors a change in a natural frequency of the probe accompanying a change in dynamics of the fluid.   The shape measuring sensor according to claim 2, wherein at least one of detection directions of the acceleration sensor is set in parallel with a scanning direction of the probe.   The shape measurement sensor according to claim 1, wherein the load detection unit is an acoustic sensor that monitors a change in sound pressure accompanying a change in dynamics of the fluid.   The shape measurement sensor according to claim 1, wherein the load detection unit is a mechanism that monitors a change in an air volume or a wind pressure accompanying a change in dynamics of the fluid.

Images