WO2015093244A1

WO2015093244A1 - Measurement probe and shape measurement device

Info

Publication number: WO2015093244A1
Application number: PCT/JP2014/081192
Authority: WO
Inventors: 橋本　直樹; 俊一郎吉田; 誠司曽和; 克司渡邊; 章弘藤本
Original assignee: コニカミノルタ株式会社
Priority date: 2013-12-18
Filing date: 2014-11-26
Publication date: 2015-06-25

Abstract

Provided are a measurement probe and shape measurement device that use a technical concept not present in the prior art to make it possible to measure the shape of an object under measurement without tilting a probe. A measurement probe has: a probe part provided with a spherical surface to be brought into contact with an object under measurement; an X-axis guide for holding the probe part so as to be movable in an X-axis direction, a Y-axis guide for holding the probe part and X-axis guide so as to be movable in a Y-axis direction, and a Z-axis guide for holding the probe part, the X-axis guide, and the Y-axis guide so as to be movable in a Z-axis direction, where the Z-axis is made to roughly coincide with the gravitational acceleration direction and the X-axis direction and the Y-axis direction, which are perpendicular to each other, are made to be perpendicular to the Z-axis direction; an X-axis biasing mechanism for biasing the probe part toward an X-axis direction reference position, a Y-axis biasing mechanism for biasing the probe part and the X-axis guide toward a Y-axis direction reference position, and a Z-axis biasing mechanism for biasing, in a direction opposite from the gravitational acceleration direction, the probe part, the Y-axis guide, and the X-axis guide so as to bear a portion of the weight of the same; and a Y-axis sensor for detecting the position of the probe part in the Y-axis direction and an X-axis sensor for detecting the position of the probe part in the X-axis direction.

Description

Measuring probe and shape measuring device

The present invention relates to a measurement probe and a shape measuring apparatus suitable for measuring a three-dimensional shape of, for example, an optical element or its mold.

For example, as a technique for measuring the shape of a workpiece surface such as an optical element, a measuring probe having a stylus having a substantially spherical tip is brought into contact with the workpiece surface, and scanning (scanning) is performed along the surface, with an arbitrary pitch. Thus, a three-dimensional measurement technique is known in which the three-dimensional coordinate position of the stylus position is acquired and the discrete point cloud is used as the contour shape of the workpiece surface.

In general, a three-dimensional measuring apparatus that performs such a measurement generally has a measuring probe configured such that the stylus is movable only in the vertical direction with respect to the probe. In general, it is not suitable for measurement of a vertical plane parallel to the direction, and the measurable inclination angle is generally limited. Therefore, with this type of three-dimensional measuring apparatus, it is difficult to scan a surface shape with an angle exceeding 80 ° in the periphery, such as an optical surface close to a hemisphere of a high NA lens used in an optical pickup device. .

On the other hand, by tilting the stylus with respect to the probe as in Patent Document 1 and acquiring the amount of inclination by the inclination detecting means, it is possible to measure even on a wall surface having an inclination angle of 90 ° and to move in the vertical direction. A measuring device capable of measuring a horizontal plane has been developed.

JP 2010-286475 A

By the way, in order to measure an inclined surface with a stylus, it is generally necessary to elastically support the stylus, but the contact force of the stylus is to avoid deformation of the resin object to be measured. It is important to make it extremely small. For this purpose, it is desirable to make the support member for elastically supporting the stylus as low as possible. However, the technique of Patent Document 1 has the following problems.

First, as an adverse effect of lowering the rigidity of the support member, there is a problem that workability for replacing a damaged stylus is lowered. When using an optical element or the like as an object to be measured, it is preferable that the force to be applied from the stylus during measurement is extremely small in order to suppress deformation due to measurement. For this reason, the support member that supports the stylus is also of relatively low rigidity, and if an unexpected external force is applied to the support member, the support member may easily be deformed. In particular, when a member such as a leaf spring is used as the support member, if an unexpected external force is applied at the time of replacement of the stylus, plastic deformation may be caused and the performance of the probe may be impaired. On the other hand, there is a method in which the stylus is replaced with a lock member that prevents the stylus from being tilted more than expected, while the deformation of the support member is suppressed. Deteriorating.

Next, for example, when measuring the inclination of the stylus with an arbitrary pitch while scanning the circumference of the wall surface in a state where the stylus is in contact with the wall surface of the cylinder, it is supported by the elastic support member. A torsional force about the axis parallel to the vertical direction is generated on the stylus. This influence becomes larger as the rigidity of the support member that elastically supports the stylus becomes lower, resulting in a measurement error. Further, the configuration of the detecting means is difficult and complicated. Further, an element that determines the center of inclination of the stylus is necessary, and without it, lateral displacement of the stylus will occur. In that case, it is difficult to obtain an accurate stylus position only with the stylus inclination detecting means.

On the other hand, in Patent Document 1, the center of inclination is determined by using a needle-like projection and a conical groove as the means. However, when using means such as needle-like protrusions and conical grooves, the center of the tilt is generally stable, but the problem is that deterioration of measurement accuracy due to wear of needle-like protrusions and wear due to needle-shaped special notes and conical groove contact is inevitable. There is.

Furthermore, the tip of the stylus that comes into contact with the object to be measured is generally generally spherical. The reason for this is that if the shape measurement data of the non-measurement surface obtained and the position (posture) of the stylus are known, the radius of the tip spherical part is corrected to make the actual shape of the non-measurement surface highly accurate. It is because it is obtained. Further, referring to FIG. 1, the stylus PLB capable of measuring from the horizontal plane HP to the vertical plane VP of the object OBJ has secured a certain degree of rigidity above the spherical portion SP at the tip in consideration of deformation. In many cases, the shaft TS having an arbitrary length and a diameter smaller than the diameter of the spherical portion SP is provided. Furthermore, an axis FS having a diameter larger than the diameter of the tip spherical portion SP is provided above the shaft FS, and an attachment portion of the stylus PLB is often configured. The reason why the shaft TS having an arbitrary length and a smaller diameter than the spherical portion SP at the tip is necessary is to prevent the shaft TS from contacting the vertical surface VP prior to the spherical portion SP when measuring the vertical surface VP. It is.

However, in the case of a measuring apparatus that performs measurement by tilting the stylus as in Patent Document 1, there is a problem in that the shaft portion above the spherical portion comes into contact with the surface to be measured and approaches. For this reason, the shaft portion must have a small diameter in consideration of the inclination. Narrowing the shaft portion immediately leads to a decrease in the stiffness of the stylus and causes a measurement error. Therefore, in order to perform accurate measurement, it is necessary to shorten the length of the shaft portion. In other words, it can be said that the inclination becomes the limit of the depth that can be measured as it is.

Similarly, when measuring by tilting the stylus, a measurement method that scans (scans) while detecting the contact state of the stylus (touch measurement) or controlling and maintaining the contact state is common. It is. In any of these means, the contact amount (tilt amount) of the stylus must always be constant for highly accurate measurement. This is because the contact position of the tip spherical portion is different if the contact amount changes even if the same location is being measured. Normally, the spherical part at the tip of the stylus can be manufactured as a single unit with high accuracy with a sphericity of less than submicron if the diameter is on the order of 1 mm. Can be used as However, when the diameter of the tip sphere is on the order of less than 0.1 mm, it is difficult to bond to the shaft portion, and in general, the shaft portion and the spherical portion are often processed integrally. However, in the integral processing with the shaft portion, it is difficult to form a spherical portion having a sphericity of micron order. When the object to be measured is measured while tilting the stylus with inferior sphericity of the spherical part, the distance between the contact position and the center of the sphere changes each time the stylus tilt changes and the contact position changes. Measurement accuracy will be reduced. In addition, there is another problem that the accuracy required for the detection means and the control means to keep the inclination constant increases.

An object of the present invention has been made in view of the above-described problems, and a measurement probe and a shape measuring apparatus capable of measuring the shape of an object to be measured without inclining the stylus according to a technical idea different from the prior art. Is to provide.

In order to realize at least one of the above-described objects, a measurement probe reflecting one aspect of the present invention is a measurement probe used for obtaining three-dimensional coordinates of an arbitrary point on the surface of an object to be measured,
A stylus having a spherical surface to be in contact with the object to be measured;
When the Z-axis direction is substantially coincident with the gravitational acceleration direction and the X-axis direction and the Y-axis direction orthogonal to each other are defined as directions orthogonal to the Z-axis direction,
An X-axis guide that holds the stylus part movably in the X-axis direction, a Y-axis guide that holds the stylus part and the X-axis guide movably in the Y-axis direction, the stylus part, A Z-axis guide that holds the X-axis guide and the Y-axis guide movably in the Z-axis direction;
An X-axis biasing mechanism that biases the stylus part to a reference position in the X-axis direction; a Y-axis biasing mechanism that biases the stylus part and the X-axis guide to a reference position in the Y-axis direction; A Z-axis biasing mechanism that biases the stylus part, the Y-axis guide, and the X-axis guide in a direction opposite to the gravitational acceleration direction so as to load a part of its own weight;
A Y-axis sensor that detects a position of the stylus part in the Y-axis direction, and an X-axis sensor that detects a position of the stylus part in the X-axis direction.

The present inventors have found a technique for measuring the shape of the vertical surface of the object to be measured without inclining the stylus part, based on a technical idea different from the prior art. If the stylus part is not inclined as in the prior art, it is not necessary to use a shaft part with a diameter much smaller than the diameter of the spherical part as described above, and high sphericity of the stylus part can be secured even at a low cost. . In addition, if the shaft portion is thick, it is possible to suppress twisting of the stylus portion during scanning measurement of a cylindrical surface, and more accurate measurement is possible, and for example, the stylus to a deeper position of the object to be measured. Departments can be reached and measurement restrictions are relaxed. Furthermore, there is no need to support the stylus part with a low-rigid elastic material or the like, and the stylus part can be easily replaced.

Here, when measuring the shape of the vertical surface of the object to be measured without tilting the stylus part, a mechanism for guiding the stylus part in a horizontal direction while maintaining the posture of the stylus part (the Y-axis guide and The X-axis guide may be provided. However, a predetermined contact pressure cannot be secured to the stylus part and the object to be measured simply by providing a guide mechanism. Therefore, in the present invention, the X-axis biasing mechanism that biases the stylus part to the reference position in the X-axis direction, and the stylus part and the X-axis guide are biased to the reference position in the Y-axis direction. Y-axis urging mechanism, Z-axis urging mechanism for urging the stylus part, the Y-axis guide, and the X-axis guide in a direction opposite to the gravitational acceleration direction so as to load a part of its own weight Is provided. Thereby, it can always be made to contact with predetermined contact pressure, without making a stylus part incline to the perpendicular surface etc. of a to-be-measured object.

According to the present invention, it is possible to provide a measurement probe and a shape measuring apparatus capable of measuring the shape of an object to be measured without tilting the stylus according to a technical idea different from the prior art.

It is a figure which shows the stylus part vicinity of a prior art. It is a perspective view which shows the shape measuring apparatus of this embodiment. 1 is an exploded perspective view of a probe unit (measurement probe) 100. FIG. FIG. 4 is a part of a cross-sectional view cut along a plane indicated by line IV-IV in FIG. 3. FIG. 5 is an exploded perspective view showing the case 111 removed from the movable unit 110 and is shown together with the frame 101. 3 is an exploded perspective view of a movable unit 110. FIG. 3 is an exploded perspective view of a movable unit 110. FIG. FIG. 4 is an axial sectional view of a Y-axis slider 116 and a Y-axis hydrostatic bearing 117 in the assembled state. It is a figure which expands and shows the front-end | tip of the stylus part 125 in the state which moved the X-axis stage 17 and the Y-axis stage 18 to arbitrary positions.

Embodiments according to the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for carrying out the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples. Here, the Z-axis direction is a vertical direction, and the X-axis direction and the Y-axis direction are horizontal directions.

FIG. 2 is a perspective view showing the shape measuring apparatus of the present embodiment. In FIG. 2, a pair of pillars 11 are erected on the surface plate 10. The beam member 12 extends horizontally so as to connect the upper ends of the pair of columns 11. A Z-axis stage 15 is provided in the center of the beam member 12 via a holder 13. The Z-axis stage 15 is configured such that a probe unit (measuring probe) 100 with a stylus protruding downward can be moved in the Z-axis direction with respect to the surface plate 10. A mirror MZ is provided on the upper surface of the probe unit 100. Further, a laser length measuring device (Z-axis sensor) LZ provided on the holder 13 is opposed to the mirror MZ, and passes through the spherical center of the stylus part described later. The Z-axis direction displacement amount of the probe unit 100 relative to the fixed holder 13 can be measured at a position on the axis along the vertical direction (Z-axis measurement unit).

On the surface plate 10, an X-axis stage 17 movable in the X-axis direction and a Y-axis stage 18 movable in the Y-axis direction are stacked, and the mounting surface on the uppermost surface thereof. The object to be measured OBJ placed on 19 can be displaced independently in the X-axis direction and the Y-axis direction. Further, the mounting surface 19 is provided with a mirror MX facing the X-axis direction and a mirror MY facing the Y-axis direction. A laser length measuring device LX provided on the surface plate 10 faces the mirror MX, and a laser length measuring device LY provided on the surface plate 10 faces the mirror MY. The X-axis direction displacement amount and the Y-axis direction displacement amount of the mounting surface 19 can be measured.

FIG. 3 is an exploded perspective view of the probe unit 100. FIG. 4 is a part of a cross-sectional view taken along the line IV-IV in FIG. As shown in FIG. 3, the probe unit 100 includes a frame 101 fixed to the Z-axis stage 15 and a movable unit 110 accommodated in the frame 101. The frame 101 has a rectangular tube shape, and its lower end is closed by a lower plate 102 having an opening 102a.

The movable unit 110 has a case 111 housed in the frame 101 and movable in the Z-axis direction. The case 111 has a rectangular tube shape, and its lower end is closed by a lower plate 112, and its upper end is closed by an upper plate 113 on which a mirror MZ is placed. On the side wall of the case 111, a stepped portion 111a is formed with the upper portion protruding. On the other hand, as shown in FIG. 4, a step 101a is formed on the inner periphery of the side wall of the frame 101 corresponding to the step 111a, and an opening 101b connecting the air introduction connector 103 is formed below the step 101a. Has been. Below the opening 101b, the gap between the frame 101 and the case 111 is narrow. The frame 101 and the case 111 constitute a Z-axis guide.

When air is introduced between the frame 101 and the case 111 below the stepped portion 101a from the air pressure source (not shown) through the connector 103 and the opening 101b with the case 111 inserted into the frame 101, the air is It functions to expand upward by applying air pressure between the

opposed step portions

111a and 101a. As a result, most of the weight of the movable unit 110 can be supported with respect to the frame 101. However, when a load that cannot be supported remains, another case is used to supplement the case with the frame 101 using a spring or the like. It is also possible to bias 111 upward, and the contact pressure of the stylus part described later can be kept within a predetermined range. The connector 103, the opening 101b, and the

step portions

111a and 101a constitute a Z-axis direction urging mechanism.

As shown in FIG. 3, the frame 101 has notches 101c to 101e formed on the side surfaces.

FIG. 5 is an exploded perspective view of the movable unit 110 with the case 111 removed and shown together with the frame 101. The lower plate 112 that closes the lower end of the case 111 in the movable unit 110 has an opening 112a. The case 111 has notches 111b to 111d and an opening 111f formed on the side surface.

6 and 7 are exploded perspective views of the movable unit 110, but the case 111 is omitted. A Y-axis sensor 115 and a prismatic Y-axis slider 116 are attached to a support plate 114 extending downward from the lower surface of the upper plate 113 of the case 111 side by side. The central axis of the Y-axis sensor 115 is arranged so as to be parallel to the vertical axis of the Y-axis slider 116.

Although formed entirely of a porous member, a rectangular cylindrical Y-axis hydrostatic bearing 117 which is sealed except for the inner peripheral surface surrounds the Y-axis slider 116 with a gap of several μm interposed on the inner peripheral surface. It is attached in this way. A connector 118 is provided to supply air into the Y-axis hydrostatic bearing 117. Air introduced into the Y-axis hydrostatic bearing 117 from the air pressure source (not shown) through the connector 118 is discharged from the porous inner peripheral surface with uniform pressure, and the Y-axis slider 116 is in a non-contact state. Thus, it is held so as to be relatively movable in the Y-axis direction. The Y axis slider 116 and the Y axis hydrostatic bearing 117 constitute a Y axis guide.

FIG. 8 is a sectional view in the axial direction of the Y-axis slider 116 and the Y-axis hydrostatic bearing 117 in the assembled state. As shown in FIG. 8, a magnet MG1 is arranged on the upper surface of the Y-axis slider 116 so that N poles are arranged on both sides of the S pole. On the other hand, on the inner peripheral surface of the Y-axis hydrostatic bearing 117, a magnet MG2 is arranged so that the S poles are arranged on both sides of the N pole. The Y-axis slider 116 and the Y-axis hydrostatic bearing 117 are stably stopped at the position (reference position) shown in FIG. 8 by the attractive force acting between the S pole and the N pole of the magnets MG1 and MG2. On the other hand, if the Y-axis hydrostatic bearing 117 is displaced in the left-right direction in FIG. It has come to be.
Magnets MG1 and MG2 constitute a Y-axis direction biasing mechanism.

In FIG. 7, a Y-axis sensor 115, which is a capacitance sensor, measures the distance to a point PY where the central axis intersects the end surface of the Y-axis hydrostatic bearing 117, and transmits it to the CPU. . When a point PY, which is a measurement unit of the Y-axis sensor 115, is projected in the Y-axis direction, it intersects with a vertical axis passing through the spherical center of a stylus unit 125 described later.

An X-axis sensor 120 and a prismatic X-axis slider 121 are mounted side by side on a support plate 119 attached to the side surface of the hydrostatic bearing 117 and extending downward. The central axis of the X-axis sensor 120 is arranged in parallel with the central axis of the X-axis slider 121 and overlapping in the vertical direction.

Although formed entirely of a porous member, a rectangular tube-shaped X-axis hydrostatic bearing 122 which is sealed except for the inner peripheral surface surrounds the X-axis slider 121 with a gap of several μm interposed on the inner peripheral surface. It is attached in this way. A connector 123 is provided to supply air into the X-axis hydrostatic bearing 122. Air introduced into the X-axis hydrostatic bearing 122 from the pneumatic source (not shown) through the connector 123 is discharged from the porous inner peripheral surface with uniform pressure, and the X-axis slider 121 is in a non-contact state. Thus, it is held so as to be relatively movable in the X-axis direction. The X axis slider 121 and the X axis hydrostatic bearing 122 constitute an X axis guide.

A pair of magnets similar to those shown in FIG. 8 are arranged as an X-axis direction biasing mechanism between the X-axis slider 121 and the X-axis hydrostatic bearing 122 in the assembled state. The X-axis hydrostatic bearing 122 is biased toward the reference position with respect to the X-axis slider 121. As the Y-axis direction biasing mechanism and the X-axis direction biasing mechanism, the movable portion may be biased to the reference position using a pair of springs.

The X-axis sensor 120, which is a capacitance sensor, measures the distance to the point PX where the central axis intersects the end surface of the X-axis hydrostatic bearing 122, and transmits it to the CPU. When a point PX, which is a measurement part of the X-axis sensor 120, is projected in the X-axis direction, it intersects with a vertical axis passing through the spherical center of a stylus part 125 described later. The plate member 126 attached to the X-axis hydrostatic bearing 122 at the end opposite to the support plate 119 functions as a stopper that restricts relative movement between the X-axis hydrostatic bearing 122 and the X-axis slider 121. To do.

Here, the Y-axis sensor 115 is exposed to the outside through the notch 111d of the case 111 and the notch 101e of the frame 101, and does not interfere with the case 111 or the frame 101 even if the stylus part is displaced. . Further, the connector 118 is exposed to the outside through the notch 111c of the case 111 and the notch 101d of the frame 101, and does not interfere with the case 111 or the frame 101 even if the stylus part is displaced. Further, the connector 123 is exposed to the outside through the opening 111f of the case 111 and the notch 101c of the frame 101, and does not interfere with the case 111 or the frame 101 even if the stylus part is displaced. Further, the X-axis sensor 120 is exposed to the outside through the notch 111b of the case 111 and the notch 101c of the frame 101, and does not interfere with the case 111 or the frame 101 even if the stylus part is displaced.

A holding plate 124 is fixed to the lower surface of the X-axis hydrostatic bearing 122. A stylus portion 125 is attached to the holding plate 124 so as to extend downward, and protrudes downward through an opening 112a of the case 111 and an opening 102a of the frame 101 provided for avoiding interference. As a specific configuration, the stylus portion 125 extends from a main body 125b whose upper end is screwed to the tip of a root portion 124a formed to protrude from the center of the lower surface of the holding plate 124, and a conical lower end of the main body 125b. It consists of a thin-shaft tip portion 125c. A spherical portion 125d is formed at the tip of the tip portion 125c. The main body 125b and the front end portion 125c are manufactured separately from the spherical body portion 125d, and both can be integrated by adhesion. Alternatively, when the diameter of the spherical portion 125d is relatively small, the main body 125b and the tip portion 125c and the spherical portion 125d may be integrally formed. When the distal end portion 125c is deformed or damaged, it can be easily replaced by removing the main body 125b from the root portion 124a. Note that the diameter of the tip portion 125c is 70% or more of the diameter of the spherical portion 125d, but less than 100%. Further, output signals of sensors that detect the movement amounts of the X-axis stage 17 and the Y-axis stage 18 and the movement amounts of the stylus part 125 in the X-axis direction, the Y-axis direction, and the Z-axis direction are input to the CPU.

Next, the measurement operation of this embodiment will be described. First, air is introduced between the frame 101 and the case 111 from a pneumatic source (not shown) via the connector 103 and the opening 101b, so that the case 111 receives a force directed upward in the vertical direction with respect to the frame 101. Further, air is introduced into the Y-axis hydrostatic bearing 117 from the air pressure source (not shown) via the connector 118, so that the Y-axis hydrostatic bearing 117 is not in contact with the Y-axis slider 116 in the Y-axis direction. It is held so that it can be moved relatively. Further, air is introduced into the X-axis hydrostatic bearing 122 from the air pressure source (not shown) via the connector 123, so that the X-axis hydrostatic bearing 122 is not in contact with the X-axis slider 121 in the X-axis direction. It is held so that it can be moved relatively. That is, the stylus part 125 can move arbitrarily in the three-dimensional directions of the Z-axis direction, the Y-axis direction, and the X-axis direction by applying a light external force while maintaining a posture extending in the vertical direction. It has become. The stylus portion 125 is urged by a magnetic force so as to return to the reference position (origin) in the X-axis direction and the Y-axis direction by an X-axis urging mechanism including a magnet (not shown) and a Y-axis urging mechanism. ing. Therefore, a strong biasing force is generated as the stylus part 125 moves away from the reference position. However, since the displacement amount of the stylus part 125 can be detected at the time of measurement, the CPU prevents the displacement amount from becoming excessive. It is preferable to control the contact pressure of the stylus part 125 at the time of measurement to be 0.098 mN to 0.98 mN by appropriately driving the X-axis stage 17 and the Y-axis stage 18 by the above signal.

Here, the Z-axis stage 15, the X-axis stage 17, and the Y-axis stage 18 are driven, for example, the sphere part 125 d of the stylus part 125 is brought into contact with one of the objects to be measured OBJ. Then, the X-axis stage 17 (or Y-axis stage 18) is driven, and the CPU reads the three-dimensional information of the stylus part 125 intermittently (touch method) or continuously (scan method).

FIG. 9 is an enlarged view showing the tip of the stylus part 125 in a state where the X-axis stage 17 and the Y-axis stage 18 are moved to arbitrary positions. Here, it is assumed that the movement amount of the X-axis stage 17 read by the laser length measuring device LX is X1, and the movement amount of the Y-axis stage 18 read by the laser length measuring device LY is Y1. This amount corresponds to the amount of movement of the object to be measured OBJ relative to the surface plate 10, but is different from the relative amount of movement of the stylus part 125. The reason is that if the surface of the measurement object OBJ with which the stylus part 125 abuts is inclined in an arbitrary direction, the stylus part 125 receives the reaction force RF from the surface of the measurement object OBJ and moves slightly. Because it does. The reaction force RF is decomposed into a Z-axis direction component Rz, a Y-axis direction component Ry, and an X-axis direction component Rx. Obviously, when the spherical portion 125d is located at the apex of the object OBJ, both the Y-axis direction component Ry and the X-axis direction component Rx are zero.

Since the Y-axis hydrostatic bearing 117 is pressed against the Y-axis slider 116 based on the decomposed Y-axis direction component Ry, the stylus 125 moves from the reference position to the Y-axis stage 18 along the moving direction of the Y-axis stage 18. Since the movement amount y is moved in the axial direction (y is a negative value when moving in the reverse direction), the movement amount Y of the Y-axis stage 18 is corrected accordingly. This movement amount y can be detected by the Y-axis sensor 115. On the other hand, since the X-axis hydrostatic bearing 122 is pressed against the X-axis slider 121 based on the decomposed X-axis direction component Rx, the stylus part 125 is moved to the reference position along the moving direction of the X-axis stage 17. Therefore, the movement amount X of the X-axis stage 17 is corrected by that amount. This movement amount x can be detected by the X-axis sensor 120. The amount of movement of the stylus 125 in the Z-axis direction is the reading Z1 itself of the laser length measuring device LZ.

From the above, the center of the spherical part 125d of the stylus part 125 is located at the coordinates (X1-x, Y1-y, Z1). By considering the radius of the spherical portion 125d, the three-dimensional coordinates of the surface of the object OBJ with which the spherical portion 125d is in contact can be obtained. By connecting the obtained three-dimensional coordinate groups, the entire surface shape of the object to be measured OBJ can be obtained. When the measurement is completed and the spherical part 125d is separated from the object to be measured, the stylus part 125 returns to the reference position.

According to the present embodiment, since the Y-axis urging mechanism that urges the stylus part 125 to the reference position in the Y-axis direction is provided, when the spherical body part 125d comes into contact with the surface of the object OBJ, Since a predetermined pressing force is applied in the Y-axis direction and an X-axis urging mechanism for urging the stylus part 125 to the reference position in the X-axis direction is provided, the spherical portion 125d is formed on the surface of the object OBJ. When abutting, a predetermined pressing force can be applied in the X-axis direction, so that even if the inclined surface is close to the vertical surface of the object to be measured OBJ, the spherical portion 125d does not leave during measurement and is stable. Thus, highly accurate shape measurement becomes possible.

Hereinafter, preferred embodiments will be described together.

In the measurement probe, the stylus part preferably has an axis having a diameter of 70% or more and less than 100% of the diameter of the spherical surface. Thereby, the rigidity of the stylus part can be increased, and precise measurement can be performed up to a deeper position of the object to be measured. In addition, it is more preferable in the diameter of the said stylus part being 75% or more of the diameter of the said spherical surface.

Further, it is preferable that at least one of the Y-axis sensor and the X-axis sensor is a non-contact type. Thereby, the influence of the detection on a measurement can be suppressed.

Further, it is preferable that when the measurement point of the Y-axis sensor is projected in the Y-axis direction, it intersects with a vertical axis passing through the spherical center of the stylus part.

Moreover, it is preferable that when the measurement point of the X-axis sensor is projected in the X-axis direction, it intersects with a vertical axis passing through the spherical center of the stylus part.

The shape measuring apparatus includes the above-described measurement probe, a Z-axis stage that moves in the Z-axis direction while holding the measurement probe, and the object to be measured mounted on the X-axis direction and the Y-axis direction independently. An XY stage that moves.

In the shape measuring apparatus, it is preferable to arrange a Z-axis sensor on a vertical axis passing through the spherical center of the stylus part. As a result, Abbe error can be reduced and precise measurement can be performed.

“The Z-axis direction substantially coincides with the gravitational acceleration direction” includes the case where the Z-axis direction and the gravitational acceleration direction completely coincide with each other and the case where the Z-axis direction is tilted within 10 ° with respect to the gravitational acceleration direction.

The Y-axis sensor preferably measures the displacement of a movable part that moves together with the Z-axis guide and the stylus part with respect to the fixed part of the Y-axis guide. The X-axis sensor preferably measures the displacement of a movable part that moves together with the Y-axis guide, the Z-axis guide, and the stylus part with respect to the fixed part of the X-axis guide.

The Z-axis sensor includes a length measuring mirror attached above the movable part of the Z-axis guide that supports the stylus part, a laser displacement meter attached to the measuring device in a state independent of the probe, and the like. By obtaining the displacement of the length measuring mirror from above the Z-axis guide, the displacement in the Z-axis direction can be obtained. Further, it is preferable that a length measuring mirror is disposed on a vertical axis passing through substantially the center of the movable portion of the Y-axis direction guide and the X-axis guide.

At least one of the Y-axis biasing mechanism and the Z-axis biasing mechanism is disposed between a fixed portion and a movable portion of each axis guide, and the movable portion is moved to a reference position with respect to the fixed portion by a spring. A permanent magnet or air pressure generating means is preferable.

The Z-axis biasing mechanism is preferably a compression spring that is placed between the fixed portion and the movable portion of the Z-axis guide and biases the movable portion in a direction opposite to the direction of gravity acceleration. Due to the elastic force of the compression spring, it is possible to generate a force that pushes up the movable part of the Z-axis guide together with the stylus part.

The Z-axis urging mechanism is preferably a permanent magnet that is placed between the fixed part and the movable part of the Z-axis guide and urges the movable part in the direction opposite to the gravitational acceleration direction. The force of pushing up the movable part of the Z-axis guide together with the stylus part can be generated by the magnetic force of the permanent magnet.

The Z-axis urging mechanism is preferably an air pressure generating means that is placed between the fixed portion and the movable portion of the Z-axis guide and urges the movable portion in a direction opposite to the gravitational acceleration direction. The air pressure generated by the air pressure generating means can generate a force that pushes up the movable part of the Z-axis guide together with the stylus part.

As an example of the air pressure generating means, a part of an arbitrary surface of the movable portion of the Z-axis guide is cut out to form a surface having an arbitrary area toward the lower surface in the vertical direction, and the fixed portion of the Z-axis guide By supplying the compressed air from the above, it is possible to generate a force that pushes the vertically movable portion upward by the compressed air. The upward levitation force due to the compressed air can be adjusted by adjusting the pressure of the compressed air supplied by controlling a valve provided in the compressed air piping supplied from the compressed air source by voltage control or the like. Precise levitation control is possible. Two or more examples of the above Z-axis biasing mechanism can be used in combination. By using a spring and air pressure together, vibration can be suppressed and damping can be effectively performed.

Note that a sensor for detecting the contact pressure of the stylus part may be provided separately to control the air pressure or the like so as to maintain the contact pressure substantially constant. In this case, it is preferable to smooth the sensor signal by passing it through a vibration suppression filter or the like.

It is preferable that at least one of the Y-axis guide and the X-axis guide is a static pressure guide using compressed air. When the static pressure guide is provided in the X-axis guide, the X-axis cylindrical member (movable part of the X-axis guide) whose inner surface that supports the stylus portion so as to be movable is porous, and the Y-axis guide It can be formed from an X-axis slide member (fixed part of the X-axis guide) connected to the movable part and surrounded by the X-axis tube member. By supplying compressed air from the outside to the inside of the X-axis cylinder member, the compressed air is discharged from the porous inner peripheral surface of the X-axis cylinder member with a uniform pressure. It can be supported so as to be movable with low friction in the direction. The X-axis cylinder member and the X-axis slide member may be in an opposite relationship.

The static pressure guide provided in the Y-axis guide includes a Y-axis cylindrical member (movable part of the Y-axis guide) having an inner surface that supports the fixed part of the X-axis guide so as to be movable, and the Z-axis guide. A Y-axis slide member (fixed portion of the Y-axis guide) connected to the movable portion of the shaft guide and surrounded by the Y-axis cylindrical member can be formed. By supplying compressed air to the inside of the Y-axis cylinder member from the outside, the compressed air is discharged from the porous inner peripheral surface of the Y-axis cylinder member with a uniform pressure. It can be supported so as to be movable with low friction in the direction. The Y-axis cylinder member and the Y-axis slide member may have an opposite relationship. It is desirable to provide an oil mist filter in the compressed air piping supplied for the hydrostatic bearing to suppress the ingress of oil.

The Z-axis guide can also be configured by a Z-axis stage provided in the shape measuring apparatus. In this case, the frame constitutes the fixed part of the Z-axis guide, and the Z-axis stage constitutes the movable part.

As described above, it is possible to realize a horizontal scanning probe capable of moving the stylus part along two axes orthogonal to each other on a horizontal plane.

Further, by applying a magnetic repulsive force or a magnetic attractive force between the movable part and the fixed part to at least one of the Y-axis guide and the X-axis guide, the movable part is moved with low friction with respect to the fixed part. A magnetic bearing that can be supported may be used. In such a case, the contact pressure can be easily controlled by generating the magnetic force with an electromagnet. A hydrostatic bearing and a magnetic bearing may be used in combination.

Further, by applying an elastic force between the movable part and the fixed part to at least one of the Y-axis guide and the X-axis guide, the movable part is supported to be movable with low friction with respect to the fixed part. An elastic spring that can be used may be used.

Further, the shape measuring device is not limited to the touch type but may be a scan type.

The present invention is not limited to the embodiments described in the present specification, and includes other embodiments and modifications based on the embodiments and technical ideas described in the present specification. It is obvious to

DESCRIPTION OF SYMBOLS 10 Surface plate 11 Column 12 Beam member 13 Holder 15 Z-axis stage 17 X-axis stage 18 Y-axis stage 19 Mounting surface 100 Probe unit (measurement probe)
101 Frame 101a Step 101b Opening 101c-101e Notch 102 Lower plate 102a Opening 103 Connector 110 Movable unit 111 Case 111a Step 111b-111d Notch 111f Opening 112 Lower plate 112a Opening 113 Upper plate 114 Support plate 115 Y axis sensor 116 Y axis Slider 117 Y-axis hydrostatic bearing 118 Connector 119 Support plate 120 X-axis sensor 121 X-axis slider 122 X-axis hydrostatic bearing 123 Connector 126 Plate member 124 Holding plate 124a Root part 125 Contact point part 125b Body 125c Tip part 125d Spherical part LX Laser length measuring device LY Laser length measuring device LZ Laser length measuring device MG1, MG2 Magnetism Stone MX Mirror MY Mirror MZ Mirror OBJ DUT

Claims

A measurement probe used for obtaining the three-dimensional coordinates of an arbitrary point on the surface of the object to be measured,
A stylus having a spherical surface to be in contact with the object to be measured;
When the Z-axis direction is substantially coincident with the gravitational acceleration direction and the X-axis direction and the Y-axis direction orthogonal to each other are defined as directions orthogonal to the Z-axis direction,
An X-axis guide that holds the stylus part movably in the X-axis direction, a Y-axis guide that holds the stylus part and the X-axis guide movably in the Y-axis direction, the stylus part, A Z-axis guide that holds the X-axis guide and the Y-axis guide movably in the Z-axis direction;
An X-axis biasing mechanism that biases the stylus part to a reference position in the X-axis direction; a Y-axis biasing mechanism that biases the stylus part and the X-axis guide to a reference position in the Y-axis direction; A Z-axis biasing mechanism that biases the stylus part, the Y-axis guide, and the X-axis guide in a direction opposite to the gravitational acceleration direction so as to load a part of its own weight;
A measurement probe comprising: a Y-axis sensor that detects a position of the stylus part in the Y-axis direction; and an X-axis sensor that detects a position of the stylus part in the X-axis direction.
The measurement probe according to claim 1, wherein the stylus portion has an axis having a diameter of 70% or more and less than 100% of the diameter of the spherical surface.
3. The measurement probe according to claim 1, wherein at least one of the Y-axis sensor and the X-axis sensor is a non-contact type.
The measurement probe according to any one of claims 1 to 3, wherein when the measurement point of the Y-axis sensor is projected in the Y-axis direction, the measurement probe intersects with a vertical axis passing through the spherical center of the stylus part.
The measurement probe according to any one of claims 1 to 4, wherein when the measurement point of the X-axis sensor is projected in the X-axis direction, the measurement probe intersects with a vertical axis passing through the spherical center of the stylus part.
The measurement probe according to any one of claims 1 to 5, a Z-axis stage that moves in the Z-axis direction while holding the measurement probe, and an X-axis direction and a Y-axis on which the object to be measured is placed And a XY stage that moves independently in a direction.
The shape measuring device according to claim 6, wherein a Z-axis sensor is arranged on a vertical axis passing through a spherical center of the stylus part.