JP2014066613A - Contact probe and contact profilometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact probe and a contact profilometer which can perform highly-accurate profile measurement by reducing the influence of floating of the probe from a measured object in association with vibration of the probe.SOLUTION: A contact probe used for a profilometer measures a profile of a measured object by scanning a surface of the measured object while contacting with the measured object and also by measuring a position of the contact probe itself. A space is provided inside the contact probe, and heavy bobs are movably arranged in the space.

Description

  The present invention relates to a shape measuring apparatus having an optical element such as a lens and a mirror, and a contact probe for measuring the surface shape of a mold for manufacturing the optical element. The present invention also relates to a contact probe that detects the displacement of the contact probe with a displacement sensor using light and measures the shape of the surface of the object to be measured.

  There is a shape measuring method using a shaft-like stylus called a probe as a shape measuring method for measuring the shape of an object to be measured having a three-dimensional structure such as a lens, a mirror or the surface of a mold or the coordinates of a specific part. This measurement method moves the probe along the surface of the object to be measured while pressing it against the surface of the object to be measured with a predetermined contact force, and measures the position of the probe and the posture of the probe from a predetermined origin. The shape of the object to be measured is measured based on the measured value.

  However, when the probe cannot keep contact with the object to be measured during shape measurement due to vibration or the like generated in the probe, the floating amount with respect to the object to be measured appears as a measurement error as it is. Therefore, how to perform shape measurement while maintaining contact between the probe and the object to be measured during shape measurement has been an important technical issue.

  Conventionally, in such a three-dimensional shape measurement method, a probe as disclosed in Patent Document 1 is known. In the probe described in Patent Document 1, the probe is suspended in the radial direction of the probe by an air bearing disposed in the housing, and is suspended by a leaf spring in the thrust direction. As a result, the probe is supported so as to be displaceable in the thrust direction, and a reaction force proportional to the displacement is generated by the leaf spring. In addition, a displacement gauge is arranged in the housing so that the displacement of the tip sphere on the side of the probe in contact with the object to be measured and the end opposite to the tip sphere is measured. The housing is mounted on the moving stage. ing.

  On the other hand, a spherical cylinder is provided with a spherical weight, upper and lower coil springs for pulling it up and down, and a polymer material that gives a frictional force to the weight. These dynamic weight, coil spring and polymer material constitute a dynamic vibration absorber for the probe body. When measuring the shape of the object to be measured, the shape of the object to be measured is measured by measuring the displacement of the probe and the housing by the displacement meter and the position of the housing when the object to be measured is scanned. It is.

  The probe that is scanned while contacting the object to be measured with a constant pressure must be vibrated in the thrust direction where the suspension rigidity is weak due to the impact generated by stick-slip or the like generated between the surface of the object to be measured and the tip sphere. There is. FIG. 4 shows the time change of the probe pressing obtained when the probe is scanned following the sphere. According to FIG. 4, it can be seen that the vibration increases as the surface inclination of the sphere increases. At this time, according to the method of Patent Document 1, the vibration in the thrust direction of the probe can be reduced by configuring an appropriate dynamic vibration absorber, and the probe with respect to the object to be measured can be measured during shape measurement. It has the feature that it is difficult to raise.

Japanese Patent Laid-Open No. 2004-61462

  The method disclosed in Patent Document 1 is an effective means for reducing the vibration of the probe that occurs during probe scanning and reducing the measurement error caused by the probe floating. However, in the method disclosed in Patent Document 1, a mechanism composed of a weight, a coil spring, and a friction element must be built in in order to configure a dynamic vibration absorber in the probe. In addition, the probe and the weight must be connected by a coil spring inside the probe, and it is extremely difficult to incorporate the same mechanism in the probe. Furthermore, when the probe is downsized so that the shape can be measured even in a narrow place, it is very difficult to mount the above-described dynamic vibration absorbing mechanism on the probe.

  The present invention has been made in view of the unsolved problems of the above-described conventional techniques. That is, the present invention provides a contact-type probe and a shape measuring apparatus including the same that can easily reduce a measurement error caused by floating due to probe vibration even in a shape measurement even if the probe is downsized. It is for the purpose.

  In order to achieve the above object, the invention according to the present application scans the surface of the object to be measured while bringing the contact probe into contact with the object to be measured, and measures the position of the contact probe. A contact probe for use in a shape measuring apparatus for measuring the shape of an object to be measured, wherein a space is provided in the contact probe, and a weight is movably disposed in the space. It is.

  Moreover, it is a contact type shape measuring apparatus provided with the said contact type probe.

  In the above configuration, when the probe scans and measures the shape of the object to be measured, an impact is transmitted to the weight when vibration occurs in the probe, so that the weight is separated from the probe, and the inside of the space is separated. I can move. At this time, the weight moves while taking the momentum of the probe, and as a result, the movement of the probe due to vibration is suppressed. Therefore, it is possible to reduce a measurement error due to lifting due to probe vibration.

  As described above, according to the invention of the present application, since a movable weight separated from the probe is enclosed in the probe, the measurement error due to the probe lifting due to vibration caused by stick-slip or the like is reduced. Can be reduced. Also, since only the weight must be built in the probe, it is simple and advantageous in terms of miniaturization.

It is a block diagram of the contact-type probe of one Embodiment of this invention. It is a block diagram of the contact-type shape measuring apparatus provided with the contact-type probe of one Embodiment of this invention. It is a frequency distribution of Zp change when the sphere is scanned with the probe of the present invention. It is a time change of the probe pushing amount when the sphere is scanned with the probe not according to the present invention.

  DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of a contact probe according to an embodiment of the present invention, which best represents the features of the present invention. In FIG. 1, reference numeral 1 denotes a contact type probe (hereinafter simply referred to as “probe”) that contacts the object to be measured 4 and measures the shape, and a plurality of thin metal leaf springs 17 with respect to the probe support base 18. Is suspended by. The probe 1 is configured to be movable only in the Z-axis direction by being supported by a plurality of leaf springs 17.

  This probe 1 includes a hollow cylindrical probe shaft 2 made of a highly rigid member such as alumina, a tip sphere 16 made of a ruby sphere, a target mirror 8 that becomes a target for measuring the displacement of the probe 1, It is composed of a hard alloy weight 3 and the like. The tip sphere 16 is provided at the lower end of the probe shaft 2 and contacts the object to be measured 4. On the other hand, the target mirror 8 is provided at the upper end of the probe shaft 2, and the displacement of the tip sphere 16 in the Z-axis direction can be obtained by measuring the displacement of the target mirror 8 in the Z-axis direction. A weight is movably disposed in a space defined in the probe 1 (in the space in the contact probe).

  When the probe 1 that slides in one axial direction traces the surface shape while contacting the object 4 to be measured with a constant force and scans the shape of the object 4 to be measured, depending on the shape of the object 4 to be measured, Vibrates as shown in FIG. On the other hand, in the present invention, the weight 3 in the hollow cylindrical probe shaft 2 moves in accordance with the vibration of the probe 1 and deprives the momentum of the probe 1, thereby reducing the vibration of the probe 1.

  With the single weight 3, once the momentum is taken away from the probe 1, the effect of taking away the momentum cannot be expected until it falls and contacts the probe 1 again. For this reason, dozens of weights 3 are enclosed in the probe shaft 2, and the effect of depriving the momentum of continuous vibration is exhibited. Further, the shape of the weight 3 enclosed in a plurality is a sphere having a small contact area in order to suppress the influence of mutual friction and ensure the mobility of the weight 3.

  Further, by arranging a plurality of weights, the mass per weight can be reduced, and minute vibrations can be dealt with. The weight once separated falls and transmits a force to the probe 1, but the direction of the force is the direction in which the probe 1 is pressed against the object 4 to be measured. For this reason, the movement of the weight causes the probe 1 to take away the force of lifting from the object 4 to be measured, and to press the probe 1 and the object 4 to be measured. Unlike the general positioning operation of the moving body, the effect of the present invention can be obtained by causing the force of the probe 1 to always press against the object to be measured present on one side.

  On the other hand, in order to ensure the mobility of the weight 3, an ellipsoidal shape may be used in order to prevent the weight 3 from taking a close-packed form. In this case, the major axis of the weight 3 can be made larger than half of the inner diameter of the space. Further, when the weight 3 is spherical, the diameter of the weight 3 can be made smaller than half the inner diameter of the space. Furthermore, in order to ensure the mobility of the weight 3, a surface coating having an effect of reducing a friction coefficient such as DLC (diamond-like carbon) or a fluorine compound may be applied to the surface of the weight 3.

  The number of weights 3 filled in the probe shaft 2 is selected so as to leave a space in the probe shaft 2 where the weights 3 are movable. At this time, in order to ensure the mobility of the weight 3, the relationship between the diameter of the weight 3 and the inner diameter of the probe shaft 2 is set so that the weight 3 is not inscribed in the inner diameter of the probe shaft 2 in the close-packed state. It is desirable to choose.

  Since the weight 3 is in contact with the probe 1 only by the gravity acting on the weight 3, if the gravity acting on the weight 3 can be reduced, the contact force with respect to the probe 1 can be reduced and more minute vibrations can be achieved. It is possible to have an inhibitory effect against the above. Therefore, by filling the probe shaft 2 with a liquid, buoyancy may be generated in the weight 3 and the contact force with respect to the probe 1 may be reduced.

  FIG. 2 is a configuration diagram of a contact-type shape measuring apparatus including a contact-type probe according to an embodiment of the present invention. In FIG. 2, a contact-type shape measuring device 50 is installed on the floor 23. First, the vibration isolation table 24 is provided on the floor 23, and the measurement base 26 is provided thereon. The vibration isolation table 24 can attenuate the vibration transmitted from the floor 23 to the measurement base 26, and can reduce measurement errors. The measurement base 26 fixes the object to be measured 4 and three reference mirrors that serve as position references, an X reference mirror 27, a Y reference mirror (not shown), and a Z reference mirror 29, and is a contact type. The shape measuring apparatus 50 measures the positions of points on the surface of the DUT 4 with respect to these three reference mirrors 27 and 29.

  The contact-type shape measuring device 50 scans the surface shape while bringing the probe 1 sliding in one axial direction into contact with the object 4 to be measured with a constant force, and the displacement of the probe 1 in the sliding direction is changed to the reference mirror 27, By detecting by 28 and 29, the surface shape of the surface of the object to be measured is measured.

  The measurement base 26 is a box-like structure, to which the DUT 4 is fixed, and an X reference mirror 27 that is a horizontal position reference, and a Y reference mirror (not shown) and a Z reference that is a vertical position reference. A mirror 29 is provided. Since these measurement base and reference mirror are used as a measurement reference, they are manufactured using a material having a small linear expansion coefficient, such as a low thermal expansion ceramic, a low thermal expansion cast iron, or a low thermal expansion glass. These reference mirrors serve as position references when the probe position is measured by the interferometer described above.

The displacement between the Z distance measuring small mirror 37 and the target mirror 8 provided on the probe support base 18 is Zp, and the displacement between the Z distance measuring small mirror 37 and the Z reference mirror 29 is Z1. Using these Zp and Z1,
Z = Zp + Z1
By doing so, the displacement Z in the Z direction of the probe 1 can be obtained. The distance between the two small X-distance measuring mirrors 42a and 42b is L1, and the distance from the lower X-distance measuring small mirror 42b to the tip sphere 16 is L2. For the X and Y directions, using the displacements X1 and X2 of these L1, L2, the X reference mirror 27, and the X distance measuring small mirrors 42a and 42b,
X = X1 + (X2-X1) * (L1 + L2) / L1
It can be asked. The same applies to the Y direction. Also, a Y-distance measuring small mirror (not shown) can be provided also in the Y direction.

  A slide for moving the probe will be described. The scanning axis base 30 provided on the gantry 25 is used as a stator, and an X axis slide 31 and an X axis motor 32 that are relatively movable in the X direction in the figure are provided on the scanning axis base 30. Further, a Y-axis slide 33 and a Y-axis motor 34 that are movable relative to the X-axis slide 31 in the Y direction are provided on the X-axis slide 31. Similarly, a Z-axis slide 35 and a Z-axis motor 36 that can move relative to the Y-axis slide 33 in the Z direction are provided on the Y-axis slide 33.

  By adopting such a configuration, the Z-axis slide 14 can be moved three-dimensionally in the XYZ directions. A probe support base 18 is fixed to the Z-axis slide 35, and the probe shaft 2 is elastically supported by a plate spring 17 fixed to the probe support base 18. The leaf spring 17 is composed of one or a plurality of thin metal plates. Accordingly, the probe 1 is supported so as to be movable in the Z-axis direction with respect to the probe support base 18.

  When scanning the probe, a scanning trajectory such as a raster trajectory is given from the host controller 40 on the XY plane, and the X-axis slide 31 and the Y-axis slide 33 are moved. The movement of the X axis and the Y axis at this time is position control in which the motor is driven by the position controller 38 and each slide is moved to a desired position. On the other hand, the Z-axis slide 35 is moved only by an operation by contact force control in which the contact force F that can be obtained by Zp is controlled to be constant by the contact force controller 39.

  With respect to the Z axis, the probe 1 is moved by the position control of the XY axis while controlling the contact force of the probe 1 with respect to the object 4 to be measured, so that the probe 1 can be scanned along the object 4 to be measured. In this state, the shape of the DUT 4 can be measured by recording the displacement X, Y, Z of the probe position with respect to the XYZ position reference obtained by the interferometer.

  FIG. 3 shows the frequency distribution of Zp change when the sphere is scanned with the probe of the present invention. FIG. 3B is a graph showing a change in Zp when the probe 1 actually scans a spherical object to be measured. The vertical axis is converted to Zp, and the horizontal axis is converted to frequency. Scanning is performed until the sphere tilts from 0 ° to 0 ° and reaches 60 ° on the opposite side. As a comparison, FIG. 3 (a) also shows the results using a probe without the weight 3.

  According to FIG. 3, it can be seen that the peak value of the amplitude of Zp in the case of the probe of the present invention is suppressed as compared with the case of using the comparative probe. On the other hand, in FIG. 4, not only the magnitude of vibration changes due to the difference in tilt of the object to be scanned, but also the vibration frequency changes. In particular, vibrations with a frequency of 300 Hz or less are increasing. In a dynamic vibration absorber as disclosed in Patent Document 1, the frequency that can be attenuated is determined by the built-in spring rigidity and the mass of the weight. Therefore, a vibration suppression effect can be expected for a wider frequency range. Therefore, it is considered advantageous for suppressing vibration from a vibration source that causes vibration in a wide frequency range due to impact, such as stick-slip.

  The present invention has the above-described configuration and operation, and it is possible to reduce measurement errors caused by probe floating and to perform high-precision measurement, which has a great industrial and scientific effect.

DESCRIPTION OF SYMBOLS 1 Probe 2 Probe shaft 3 Weight 4 Measured object 8 Target mirror 16 Tip ball 17 Leaf spring 18 Probe support base 23 Floor 24 Vibration isolator 25 Base 26 Measurement base 27 X reference mirror 29 Z reference mirror 30 Scan axis base 31 X Axis slide 32 X axis motor 33 Y axis slide 34 Y axis motor 35 Z axis slide 36 Z axis motor 37 Z distance measuring small mirror 38 Position controller 39 Contact force controller 40 Host controller 42a, 42b X distance measuring small mirror 50 Contact type shape measuring device

Claims (9)

A contact type used in a shape measuring apparatus for measuring the shape of the object to be measured by scanning the surface of the object to be measured while contacting the object to be measured with the contact type probe and measuring the position of the contact type probe. A probe,
A contact-type probe, wherein a space is provided in the contact-type probe, and a weight is movably disposed in the space.   The contact probe according to claim 1, wherein a plurality of the weights are arranged.   The contact probe according to claim 1, wherein the weight is a sphere.   The contact probe according to claim 1, wherein the weight is an ellipsoid.   The contact probe according to any one of claims 1 to 4, wherein the weight is surface-coated.   The contact probe according to claim 4, wherein a major axis of the weight is larger than half of an inner diameter of the space.   The contact probe according to any one of claims 1 to 5, wherein a diameter of the weight is smaller than half of an inner diameter of the space.   The contact probe according to claim 5, wherein the weight is coated with the surface by DLC or a fluorine compound.   The surface of the surface of the object to be measured is detected by scanning the surface shape of the contact probe that slides in one axial direction while contacting the object to be measured with a constant force, and detecting the displacement of the contact probe in the sliding direction. A contact-type shape measuring apparatus for measuring a shape, comprising the contact-type probe according to any one of claims 1 to 8.

Images