JP5154149B2 - 3D measurement probe - Google Patents

Description

  The present invention is a three-dimensional measurement probe that mainly measures the shape of an aspherical lens as an example of a measurement object with an ultra-high accuracy of the order of 0.01 micron. As an example, the measurement range is small and XYZ is small. 30mm x 30mm x 20mm, large one is mounted on an ultra-high precision CMM measuring 400mm x 400mm x 90mm, and the scanning angle of the measurement surface is an example of continuous scanning from 0 degree to a high inclination part of 75 degrees in any direction. As an example, the present invention relates to a three-dimensional measurement probe that can be measured with a low measurement force of 0.1 to 0.3 mN in the probe axial direction with almost no damage, and further, the shape of the aspheric lens or the like It relates to a three-dimensional measurement probe that can measure tilt eccentricity of the front and back surfaces by measuring from the top and bottom or from the left and right simultaneously. .

  An aspherical lens must be made with a high accuracy of 0.1 micron or less, and this accuracy cannot be achieved by processing alone. Therefore, an ultra-high-precision three-dimensional measuring machine with an accuracy of the order of 0.01 micron and a three-dimensional measuring probe attached thereto have been invented. The contents are described in Patent Documents 1 and 2 and the like. By measuring with this measuring machine and feeding back the measurement result to the processing, it became possible to make a mold for an aspheric lens with an accuracy of 0.1 micron or less.

  However, aspherical lenses used in recent digital cameras and large-capacity optical discs have become more and more accurate due to thinning, high image quality, wide angle, and high zoom magnification. Therefore, there is a demand for a probe that realizes higher accuracy. On the other hand, there is a need for a three-dimensional measurement probe that is hard to break and has a long life so that workers can easily and frequently use it on the factory floor.

  Furthermore, since the aspherical lens could conventionally only be measured from above, even if the shape of the upper surface of the aspherical lens could be measured, the positional relationship between the upper surface, the lower surface and the side surface could not be easily measured. I could not make a highly accurate lens. Therefore, there is a need for a three-dimensional measurement probe that can measure with high accuracy from the bottom or the side of an aspheric lens.

  A conventional three-dimensional shape measurement probe of an aspheric lens will be briefly described with reference to Patent Documents 1 and 2.

  FIG. 12 shows a three-dimensional measurement probe described in Patent Document 1. A small sliding shaft portion 306 fixed to the stylus 305 in contact with the measurement object S is movable in the Z-axis direction with respect to the small air bearing 307 and is suspended from the atomic force probe frame 303 by a leaf spring 350.

  A mirror 309 is attached to the small sliding shaft portion 306, and the light of the semiconductor laser 334 is condensed and reflected on the mirror 309 so that the displacement of the small sliding shaft portion 306 relative to the optical probe portion 302 is constant. The unit 302 and the atomic force probe frame 303 are integrally driven by a coil 313. Here, applying the servo so that the semiconductor laser beam 334 is focused on the surface of the mirror 309 is referred to as focus servo.

  Regarding the Z coordinate measurement of the measurement point, since the distance to the mirror 309 is directly measured by applying the oscillation frequency stabilizing laser Fz to the mirror 309 and causing the reflected light to interfere, even if there is an error in the focus servo. Although there is a slight variation in the measurement force, there is almost no measurement error.

  FIG. 13A shows the measurement probe described in Patent Document 2. Similar to Patent Document 1, the small sliding portion 316 is cylindrical, supported by a leaf spring 315, and a mirror 319 is attached.

  FIG. 13B shows the configuration of an ultra-high-precision coordinate measuring machine described in Patent Document 3 and suitable for mounting the probes of Patent Documents 1 and 2. The Ueishi Sadae 406 on which the oscillation frequency stabilizing laser 327 for measuring the XYZ coordinates, the length measuring optical system, the Z slide 311 and the optical probe 302 are moved in the XY axis directions by the XY axis stages 321 and 322, respectively. An X reference mirror 324, a Y reference mirror 325, and an upper Z reference mirror 326 fixed to a portal frame 407 fixed to the lower stone surface plate 323 are fixed on the lower stone surface plate 323, and the measurement point of the measurement object 401 is measured. By measuring the distance to these high plane mirrors (X, Y, Z reference mirrors 324, 325, 326) with an oscillation frequency stabilizing laser on the axis, the movement straightness of the XY axis stages 321 and 322 is 1 micron. Even in this order, the coordinate axis accuracy of the order of 10 nm, which is the flatness of the reference mirrors 324, 325, 326, is obtained.

  However, Patent Document 3 was written before the invention of the three-dimensional measurement probe named the atomic force probe of Patent Documents 1 and 2, and the probe has only the optical probe 312.

  14A to 14C show a contact probe described in Patent Document 4. FIG. Instead of the leaf spring, the small sliding shaft (probe shaft) 70 can be held in a non-contact manner by magnetism generated by a magnetic circuit composed of a permanent magnet 72 and an iron core 75. That is, the box-shaped yoke 71 surrounds the permanent magnet 72 and the iron core 75 fixed to the probe shaft 70, and constitutes a magnetic circuit.

Japanese Patent No. 3000819 (page 3, FIG. 1) JP 2006-78367 A (page 16, FIG. 8) Japanese Patent No. 3046635 (page 6, FIG. 1) Japanese Patent Laying-Open No. 2006-98060 (page 23, FIG. 2)

  The problems to be solved by the present invention are described below.

  First of all, the requirement of the probe for measuring with ultra-high accuracy is that the measuring force is as small as 0.1 to 0.3 mN (10 to 30 mgf). Is to respond quickly and the stylus at the tip of the probe does not tilt with respect to the lateral force.

  When the measurement force is large, the measurement surface is deformed, so that the measurement accuracy is lowered. In addition, wear of the stylus in contact with the measurement surface is accelerated. In order to follow the stylus on the measurement surface when the response of the probe is slow, the scanning speed of the stylus must be reduced, so the measurement time becomes longer, and data drift due to temperature changes during that time occurs. Measurement accuracy deteriorates and efficiency decreases. If the measurement surface is inclined, a lateral force is applied to the tip of the stylus. However, if the inclination angle of the measurement surface exceeds 45 degrees, the lateral force is larger than the moving direction of the probe. If the stylus is tilted, any probe described in the conventional example becomes a measurement error. Therefore, a guide having the highest possible rigidity is required so that the stylus does not tilt due to the lateral force applied to the tip of the stylus.

If the measuring force is F, the moving part mass is M, and the response acceleration of the stylus is a, Newtonian mechanics
F = Ma (1)
If the measuring force F is made as small as possible and the response acceleration a is made as large as possible, the mass of the movable part, that is, the mass M of the small sliding shaft part has to be made as small as possible. Further, in order to prevent the stylus from tilting with respect to a lateral force, a structure that can move without friction in the moving direction and that can achieve extremely high rigidity in a direction perpendicular to the moving direction is required.

  As a result of research and development over several years, the present inventor has developed a cylindrical micro air slide, and has realized a movable part mass of 0.2 g in the small sliding shaft part.

  Here, the meaning of the word “micro air slide” will be explained. The small sliding shaft moves in the small air bearing. The small sliding shaft and the small air bearing are collectively called “micro air slide”. The air slides that are usually on the market are small, but have a moving part mass of 100 grams. On the other hand, the micro air slide referred to here has a remarkably light and small movable part mass of 0.2 grams.

  In the ultra-high precision CMM, which is the technical field of the present invention, the Z-axis is used for the coil so that the displacement of the small sliding shaft that moves with a minute measuring force relative to the optical probe including the small air bearing becomes zero. It has a double structure of a large air slide that moves greatly by driving the entire probe part by passing an electric current.

  Assuming that the measuring force is 0.2 mN and the mass of the small sliding shaft is 0.2 gram, the response acceleration of the probe is 0.1 G from the above equation (1). Here, G is the gravitational acceleration. With this level of response acceleration, a smooth aspherical lens with a diameter of 30 mm or more can be measured at a maximum measurement speed of 10 mm per second, and even a lens of less than that can be measured at a maximum speed of 5 mm per second.

  Unless all of these conditions are satisfied, a three-dimensional measurement probe that measures the shape of the aspherical lens and the like with an ultra-high accuracy of the order of 0.01 microns cannot be obtained. Only conventional probes satisfying this requirement are described in Patent Documents 1 and 2.

  However, the probes described in Patent Documents 1 and 2 have a problem that a measurement object can be measured only from above. That is, as can be seen in FIG. 13A, the leaf spring 315 is only placed on the sphere 53 embedded in the upper end of the air bearing portion 317.

  Accordingly, when this probe is placed sideways, the leaf spring 315 is separated from the ball 53 and does not exhibit springiness, and when the probe is turned upside down, the micro air slide falls down. That is, since it is a structure suspended from the top, the measurement object can be measured only from the top downward. If it can only be measured from above, the probe cannot be measured from the top or bottom or from the left or right. This is the first problem of the conventional probes described in Patent Documents 1 and 2.

  If the leaf spring is bonded to the air bearing portion, measurement can be performed from the side or from the bottom. However, when an excessive measuring force is applied to the stylus 360 due to an erroneous operation or the like, the leaf spring is broken. For this reason, the leaf spring 315 cannot be bonded to the air bearing portion.

  Further, since the leaf spring 315 is extremely thin with a thickness of 10 microns, it has a problem that it is easily broken due to deformation for a long period of use. Since only a limited number of people can be repaired, there is a tendency to use a three-dimensional measurement probe that can be used only by a limited number of people in the measurement room. This is the second problem of the conventional probe described in Patent Documents 1 and 2.

  As a method for solving the above problem, it is conceivable that a magnetic circuit is used instead of the leaf spring, and the stylus is floated against gravity and has a weak spring constant in the Z-axis direction.

  In Patent Document 4, as shown in FIGS. 14A to 14C, the probe shaft 70 is held by the air bearing 77 on the housing 76 in a non-contact manner. The holder 74 at the upper part of the probe shaft 70 is configured to hold the probe shaft 70 in the vertical direction by a magnetic circuit including a permanent magnet 72 and an iron core 75 and a yoke 71 fixed to the housing 76.

  Such a magnetic circuit configuration has an advantage that since the stylus 78 is held in a completely non-contact manner, the accuracy is high, and a very thin leaf spring is not used, so that it is not easily broken.

  However, as a drawback, since the stylus 78 is held in a non-contact manner, there is no friction, and the stylus 78 is likely to vibrate due to disturbance. The object 81 and the stylus 78 are in contact at the time of measurement, and vibration is not easily generated in the stylus 78 due to the frictional force, but the stylus 78 is in a completely non-contact state at the time of non-measurement, and the stylus 78 is susceptible to vibration due to disturbance. The vibration at the time of non-measurement becomes a problem. Since the measurement object and the stylus 78 may become non-contact during measurement of a plurality of measurement objects, it is necessary to enable reading of the Z coordinate even when the measurement object is not in contact. Because there is. In Documents 1 and 2, vibration with an amplitude of 20 μm affects the reading of the Z coordinate. In addition, in order for the stylus 78 to stably shift from the non-contact state to the contact state with respect to the measurement object 81, it is necessary to suppress vibration at the time of non-contact. In particular, when the measurement object 81 is made of a soft material, the measurement object 81 may be damaged by an impact when the stylus 78 contacts.

  FIG. 5 shows a stylus when the stylus is moved from a contact state to a non-contact state with respect to an object to be measured using the magnetically levitated three-dimensional measurement probe when the vibration countermeasure according to the present invention is not taken. The state of vibration is shown. As shown in FIG. 5, the laser measurement for measuring the Z position of the stylus may become unstable due to vibration of 20 μm or more.

  The present invention solves the above-mentioned conventional problems, and in a three-dimensional measurement probe constituted by an air bearing and a magnetic circuit, the shape of an aspheric lens is measured with an ultra-high accuracy on the order of 0.01 microns, In other words, with a three-dimensional measuring probe using a micro air slide with a low measuring force of 0.1 to 0.3 mN and a rigid aspect ratio of 1000 times, the shape of the aspherical lens can be measured from above, from below, from the left and right sides. An object of the present invention is to provide a three-dimensional measurement probe that can be measured stably with low vibration.

  In order to achieve the above object, the present invention is configured as follows.

According to the first aspect of the present invention, a small sliding shaft provided with a stylus that contacts the surface of the object to be measured at one end and a pin made of a magnetic material at the other end;
A small air-bearing portion that is formed in a probe frame having a hole for fitting with the small-sliding shaft portion and having an air ejection portion that forms a film of compressed air in a gap with the small-sliding shaft portion When,
A magnet and a yoke attached to the end of the small air bearing portion form a magnetic circuit in a non-contact manner with the pin, thereby generating a magnetic force that prevents movement of the small sliding shaft portion in the Z-axis direction, which is the axial direction. Magnetic force generating means for generating,
A transparent plate is provided in the probe frame to make the air flow restricting space in which the magnetic force generating means in the probe frame is accommodated substantially closed, and a part of the closed space communicates with the outside of the probe frame. By providing an air flow restricting member having a small-diameter hole, the air flow in the air flow restricting space is restricted so that the damping ratio with respect to vibration of the small sliding shaft is 0.007 or more. A three-dimensional measurement probe is provided.

Further, according to the second aspect of the present invention, a displacement detection means for detecting a displacement in the Z-axis direction of the small sliding shaft portion with respect to the small air bearing portion;
A Z-axis stage for moving the small air bearing in the Z-axis direction;
The displacement in the Z-axis direction generated by the movement of the stylus in the Z-axis direction along the shape of the measurement object during shape measurement for moving the measurement object or the Z-axis stage in the XY-axis direction is substantially constant. The three-dimensional measurement probe according to the first aspect, further comprising a Z-axis stage driving device for driving the Z-axis stage is provided.

  According to the third aspect of the present invention, the displacement detecting means is fixed integrally with the mirror formed on the small sliding shaft portion, the small air bearing portion, and includes at least a semiconductor laser, a lens, and a photodetector. The included optical probe and laser light emitted from the semiconductor laser of the optical probe are irradiated to the mirror through the transparent plate through the lens, and reflected light from the mirror is received by the photodetector. The three-dimensional measurement probe according to the second aspect is configured to detect the displacement in the Z-axis direction from the output signal of the photodetector.

According to the fourth aspect of the present invention, an oscillation frequency stabilized laser that emits oscillation frequency stabilized laser light;
And means for irradiating the mirror with the oscillation frequency stabilized laser beam emitted from the oscillation frequency stabilized laser through the transparent plate, and measuring the Z coordinate of the mirror from the reflected light from the mirror. A three-dimensional measurement probe according to the third aspect is provided.

  According to a fifth aspect of the present invention, there is provided the three-dimensional measurement probe according to any one of the first to fourth aspects, wherein the Z-axis stage is configured by an air bearing.

  According to a sixth aspect of the present invention, there is provided the three-dimensional measurement probe according to any one of the first to fifth aspects, wherein the Z-axis stage driving means is composed of a coil and a magnetic circuit.

  According to the seventh aspect of the present invention, any one of the first to sixth embodiments wherein the movable part of the Z-axis stage is supported by a constant load spring comprising a spirally wound thin plate that generates a tension substantially equal to its weight. A three-dimensional measurement probe according to any one of the aspects is provided.

  According to an eighth aspect of the present invention, the air flow restricting member is a cap that closes an opening of a communication path in which a part of the air flow restricting space portion that is the closed space communicates with the outside of the probe frame, and The diameter of the small-diameter hole formed in the cap is 0.05 mm in order to make the damping ratio with respect to the vibration of the small sliding shaft part 0.007 or more and to make the pressure of the air flow restricting space part 400 Pa or less. The three-dimensional measurement probe according to the first aspect is provided as described above, wherein the number is less than 0.6 mm and the number thereof is 1 or more and 60 or less.

  According to a ninth aspect of the present invention, the air flow restricting member is a cap that closes an opening of a communication path in which a part of the air flow restricting space portion that is the closed space communicates with the outside of the probe frame, and In order to make the damping ratio with respect to vibration of the small sliding shaft part 0.007 or more and to make the pressure of the air flow restriction space part 400 Pa or less, a porous material is used instead of the small diameter hole. A three-dimensional measurement probe according to the first aspect is provided, which is configured to restrict the flow of air.

  As described above, according to the present invention, the movement in the axial direction is restricted in a non-contact manner by forming a magnetic circuit with a magnetic pin having a small movable part mass, a magnet attached to a small air bearing part, and a yoke. In the three-dimensional measurement probe that can perform the vibration of the small sliding shaft portion by restricting the air flow in the air flow restricting space portion of the portion where the magnetic force generating means is configured by the air flow restricting member. Energy loss sometimes occurs, and the vibration of the small sliding shaft can be attenuated, and the vibration of the small sliding shaft can be suppressed. Therefore, it is possible to suppress the vibration of the small sliding shaft portion when not in contact with the measurement object, thereby enabling stable measurement.

  As a result, a pair of the three-dimensional measurement probes are prepared and arranged on the front and back surfaces of an aspherical lens as an example of a measurement object, and the front and back surfaces of the aspherical lens are simultaneously measured. It becomes possible to measure stably with high accuracy. In the three-dimensional measurement probe, since the magnetic force that prevents movement in the Z-axis direction, which is the axial direction of the small sliding shaft portion, is generated by the magnetic force generating means, it is necessary to use a leaf spring. In addition, it is possible to realize a three-dimensional measurement probe with higher accuracy and less fragile even for long-term use. In addition, assembling and handling are easy, so if you use this probe, you can place it on a factory site from a measuring instrument that is used only by a limited number of people in the measurement room. Become.

  As a result, it is possible to improve the performance, quality, and production yield of lenses such as cameras that are becoming thinner and higher in image quality, and optical disks that are becoming larger in recording capacity.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment)
1A and 1B are sectional views of a three-dimensional measurement probe 2A according to an embodiment of the present invention. 1A and 1B show the same probe 2A, FIG. 1A shows the arrangement of the probe 2A when measuring the surface S of the measurement object 1 from above, and FIG. 1B shows the arrangement of the probe 2A when measuring the surface S of the measurement object 1 from below. Respectively. When the upper and lower surfaces S of the measurement object 1 are simultaneously measured, the probe 2A of FIG. 1A and the probe 2A of FIG. 1B may be brought into contact with the upper and lower surfaces S of the measurement object 1 simultaneously. Although not shown, the probe 2A can be disposed with respect to the measurement object 1 from the side (for example, both the left and right sides) or from an oblique direction. FIG. 2A is an explanatory diagram of a configuration including an optical probe portion on the upper side of the ultra-high-precision coordinate measuring machine to which the coordinate measuring probe 2A of FIG. 1A in the embodiment of the present invention can be attached. FIG. 2B shows a lower optical probe unit (same structure as the upper optical probe unit) to which the three-dimensional measurement probe 2A of FIG. 1B in the embodiment of the present invention can be attached. FIG. FIG. 3 is a schematic configuration explanatory diagram including the optical probe displacement detector 2 of the three-dimensional measurement probe in the embodiment.

  When the surface S of the measurement object 1 is measured from below, the measurement object holding member 98 of FIG. 4 is configured in, for example, a ring shape to hold the periphery of the measurement object 1, and the back surface other than the periphery of the measurement object 1 is the bottom. 1B, the probe 2A shown in FIG. 1B is arranged below the measurement object 1, and the lower probe 2A can be moved independently of the upper probe 2A. Both the front and back surfaces can be measured simultaneously from the top and bottom of the measurement object 1.

  The three-dimensional measurement probe 2A according to the present embodiment includes at least a cylindrical small sliding shaft portion 6 connected to the stylus 5, a small air bearing portion 7, and a magnetic force generation means 95, and further includes a probe 2A. And a large air slide functioning as an example of a Z-axis stage (from the Z-axis direction large air slide guide 35 and the large air slide movable unit 11). A large air slide configured 89 and a Z-axis direction driving device 43 functioning as an example of a Z-axis stage driving unit. That is, the probe 2A is fixed on the magnetic pin 20 and the magnetic pin 20 having a small movable portion mass attached to the small sliding shaft portion 6 integrally fixed to the stylus 5 of the cylindrical micro air slide. A magnetic circuit is formed by the mirror 9 (Z mirror), the magnets 29a and 29b attached to the probe frame 3 via the attachment ring 3r, and the yokes 8a, 8b-1, and 8b-2, and the rotation and axial directions are formed. By providing a Z-axis direction drive device 43 that generates a magnetic force that prevents movement in a non-contact manner and moves the entire Z-axis direction so that the displacement of the micro air slide becomes constant, measurement can be performed from below or from the side of the measurement object 1. Is.

  Here, the meaning of the word “micro air slide” will be explained. Although the small sliding shaft portion 6 moves in the small air bearing portion 7, the small sliding shaft portion 6 and the small air bearing portion 7 are collectively referred to as “micro air slide”. The air slides that are usually on the market are small, but have a moving part mass of 100 grams. On the other hand, the micro air slide referred to here has a remarkably light and small movable part mass of 0.2 grams.

  In the ultra-high-precision coordinate measuring machine that is the technical field of the present invention, the displacement of the small sliding shaft portion 6 moving with a minute measuring force relative to the optical probe portion 2 including the small air bearing portion 7 becomes zero. As described above, a large air slide 89 having a double structure is constructed in which a current is passed through the coil 13 to drive the entire probe unit and move it greatly.

  Assuming that the measuring force is 0.2 mN and the mass of the small sliding shaft is 0.2 gram, the response acceleration of the probe 2A is 0.1 G from the above equation (1). Here, G is the gravitational acceleration. With this level of response acceleration, a smooth aspherical lens with a diameter of 30 mm or more can be measured at a maximum measurement speed of 10 mm per second, and even a lens of less than that can be measured at a maximum speed of 5 mm per second.

  The reason why the micro air slide is cylindrical is that the maximum rigidity can be obtained with the minimum mass. An air slide can hold | maintain an axis | shaft with high rigidity by forming the film | membrane of a high air pressure of 2-4 atmospheres in a guide part. In the case of cylindrical micro air slides, even if the diameter is made as small as 4 mm or less, if the gap of the guide part is made narrow and accurate with a precision of 10 microns or less, the air flow rate will not be so large as to significantly reduce the air pressure of the injected air. A high-pneumatic membrane is formed and can have high rigidity.

  The small sliding shaft portion 6 of the micro air slide is supported by a spring-like member and moves about 10 microns in the Z direction with a measuring force of 0.2 mN, but the deviation when the same force is applied in the lateral direction is 10 Must be nanometer or less. In other words, the aspect ratio of the probe rigidity must be 1000 times. Thus, the measurement error when the tilt angle of the measurement surface is 45 degrees is 10 nm. This is the minimum stiffness required. This structure will be described later.

  The small sliding shaft 6 connected and fixed to the stylus 5 with the stylus tip sphere 61 in contact with the surface of the measurement object 1 is processed into a highly accurate cylindrical shape of submicron level, and this is 10 microns or less. Inside the hole 7g of the small air bearing 7 having the hole 7g processed with high precision in a form that fits in the gap, the small sliding shaft portion 6 is moved in the Z-axis direction (small sliding shaft by the compressed air film). It can slide without friction in the rotational direction (in the axial direction of the part 6).

  The small air bearing 7 has a recess extending in the axial direction at predetermined intervals in the circumferential direction, and has an annular recess that communicates with the recess and is disposed at the upper and lower ends in the axial direction. Since the probe frame 3 is assembled in close contact, the air reservoir 18 can be formed. Compressed air that is connected to a compressor (not shown) and fed from the compressor through the tube 48 shown in FIGS. 2A and 2B enters the air reservoir 18 and is formed in the small air bearing 7. A compressed air film is formed by being fed into the gap between the small sliding shaft portion 6 and the hole 7g of the small air bearing 7 through a minute hole of the air ejection port 4 functioning as the ejection portion. And a small slide with the air discharge port 10 which functions as an air ejection part formed in the small air bearing 7 at predetermined intervals through the radial direction so as to face the intermediate part of the small sliding shaft part 6 Air is discharged from the upper and lower end portions (tip portion and base end portion) of the shaft portion 6. Since the small air bearing 7 and the atomic force probe frame 3 are closely fixed, they are collectively called a small air bearing portion (small air bearing unit) 7A.

  Since the clearance between the small sliding shaft portion 6 and the small air bearing 7 is as narrow as 5 to 10 microns, a large number of circumferentially and axially arranged substantially equal intervals on the outer peripheral side surface of the small air bearing 7 Compressed air of 2 atm or more is supplied from a minute hole of the air ejection port 4, and the compressed air is released from the air discharge port 10 and the upper and lower end portions (the front end portion and the base end portion) of the small sliding shaft portion 6. By the time, a film having a pressure gradient of compressed air is formed in the gap.

  When a lateral force is applied to the stylus 5 due to the measurement force of the measurement surface S inclined of the measurement object 1, when the film thickness of the compressed air is about to change, that is, for example, when the film thickness becomes thin, the air hardly flows. The air pressure increases, and conversely, when the film thickness increases, air easily flows, and therefore the air pressure decreases, so that force is applied in the direction in which the air film thickness does not change. This is the principle that produces the rigidity of the air bearing.

  On the other hand, the other end of the small sliding shaft 6 (the end opposite to the stylus 5, the upper end in FIG. 1A and the lower end in FIG. 1B) is perpendicular to the axial direction of the small sliding shaft 6. The elongated magnetic pin 20 attached along the pair of yokes 8b-1, 8b-2 attached to the atomic force probe frame 3 via the attachment ring 3r and the yokes 8b-1, 8b- A pair of magnets 29a and 29b fixed to the end face on the stylus side and arranged opposite to each other and a ring-shaped yoke 8a form a magnetic circuit as described below. That is, in the mounting ring 3r, in advance, toward the side farther from the side closer to the other end of the small air bearing 7 (the end opposite to the stylus 5, the upper end in FIG. 1A, the lower end in FIG. 1B), A pair of yokes 8b-1, 8b-2, a pair of magnets 29a, 29b, and a ring-shaped yoke 8a are fixed. In this way, the mounting ring 3r in which the pair of yokes 8b-1 and 8b-2, the pair of magnets 29a and 29b, and the ring-shaped yoke 8a are fixed inside is attached to the small air bearing 7 of the atomic force probe frame 3. It is attached to a recess 3g provided on the end (end opposite to the stylus 5, upper end in FIG. 1A, lower end in FIG. 1B). As a result, the pair of yokes 8b-1 and 8b-2 are positioned so as to face the magnetic body pins 20 attached to the end portions of the small air bearings 7 with gaps G1 and G2 therebetween. Further, the pair of magnets 29a and 29b, the ring-shaped yoke 8a, and the pair of yokes 8b-1 and 8b-2 form a magnetic circuit in a non-contact manner with the magnetic pin 20, thereby making the cylindrical small slide. The magnetic force generating means 95 is configured to generate a magnetic force that prevents movement in the Z-axis direction that is the axial direction of the shaft portion 6 and the rotation direction around the Z-axis direction. If comprised in this way, the magnetic flux which generate | occur | produced from one magnet 29a will be one gap part G1 formed between one yoke 8b-1 and the one yoke 8b-1 and one end of the magnetic body pin 20. Through the magnetic pin 20, through the other gap 8 formed between the other end of the magnetic pin 20 and the other yoke 8 b-2, through the other yoke 8 b-2, The magnetic flux generated from the magnet 29b is applied, and the magnet returns to the one magnet 29a through the ring-shaped yoke 8a.

  Near the gaps G1, G2 between the magnetic pin 20 and the yokes 8b-1, 8b-2, the magnetic pin 20 and the yokes 8b-1, 8b-2 are thick in the axial direction and thin in the rotational direction. (As shown in FIGS. 2C to 2E, it has an inclined surface with a constant thickness in the axial direction and an inclined surface that gradually decreases in width as it goes from the center side to the periphery in the radial direction. By adopting such a shape, the displacement in the rotation direction is strongly suppressed, and the displacement in the axial direction is weakly suppressed. Further, as shown in FIGS. 2C to 2E, the shape of the gap between the magnetic pin 20 and the yokes 8b-1 and 8b-2 in the vicinity of the gaps G1 and G2 is changed from the magnetic pin 20 to the yoke 8b−. 1,8b-2 is thickened. As shown in FIGS. 2C to 2E, the magnetic pin 20 is placed such that the longitudinal axis direction thereof is along the vertical direction, and as shown in FIGS. 2C to 2E, the pin thickness is 0.5 mm, the yoke thickness is 1 mm, the rotational tip width is 0.2 mm, By setting the thickness to 5 mm, the small sliding shaft portion 6 is displaced in the axial direction by about 100 microns due to its own weight, and is in a state of being balanced with the magnetic force. Therefore, when the longitudinal axis direction of the magnetic pin 20 is set along the up-and-down direction, the small sliding shaft portion 6 is displaced in the axial direction by about 100 microns due to its own weight, and is in a state of being balanced with the magnetic force. When the longitudinal direction of the magnetic pin 20 is placed sideways along the lateral direction perpendicular to the vertical direction, the self-weight of the small sliding shaft portion 6 does not act in the lateral direction, so that the magnetic flux passes best. Balance in position.

Optical probe unit in FIGS. 2A and 2B the semiconductor laser beam _{F L} from (the optical probe displacement detecting unit) 2 of the probe casing 2a wavelength 780nm which is attached to the semiconductor laser 34, a lens 32 and a polarization prism 37 and the wavelength plate 33 , And is totally reflected by the dichroic mirror 15, enters the full aperture of the lens 14, and is squeezed and irradiated onto the mirror (Z mirror) 9 fixed on the magnetic pin 20 by the lens 14. Then, the reflected light from the mirror 9 is totally reflected by the dichroic mirror 15 and the polarizing prism 37, passes through the lens 38, is branched into two by the half mirror 39, and is placed before and after the two focal points. The light passes through the pinholes 40 and enters the two photodetectors 41. When the small sliding shaft portion 6 moves in the axial direction by the measuring force of 5 on the stylus, the focal position of the reflected light from the mirror 9 changes, so that the outputs from the two photodetectors 41 are the focus error signal detection portion 42. A Z-axis direction driving device 43 that functions as an example of a Z-axis stage driving device for driving the optical probe displacement detection unit 2 to advance and retreat along the Z-axis direction based on the focus error signal. The current is simultaneously applied to the left and right coils 13 on both sides of the movable portion (large air slide movable portion) 11 of the air slide 89, and the optical probe displacement detector 2 is advanced and retracted along the Z-axis direction so that the focus error signal becomes zero. To drive.

  More specifically, as shown in FIG. 3, each coil 13 has a gap portion of a magnetic circuit formed by a large yoke 12 and a large magnet 28 fixed to the upper stone surface plate 106 side by a bracket 86 or the like. Since current flows through G3, electromagnetic force is applied in the Z-axis direction. The pair of left and right coils 13 are connected to and integrated with a large air slide movable unit 11 that moves the entire optical probe displacement detection unit 2 in the Z axis direction with high straightness while being guided in the Z axis direction by a large air slide guide 35. It has become.

  The straightness of movement of the large air slide movable unit 11 is directly related to the measurement accuracy of the ultra-high-precision coordinate measuring machine. The reason will be explained. FIG. 4 shows an example of the overall configuration of an ultra-high precision coordinate measuring machine equipped with the optical probe 5 of the present embodiment.

In FIG. 4, an oscillation frequency stabilizing laser 27 as an example of an XYZ coordinate measuring laser beam generator for measuring XYZ coordinates, and a length measuring unit (receiver 105 for X axis direction, receiver 104 for Y axis direction, Z _1). An axial receiver 103, a Z ₂ axial receiver 102), a large air slide movable unit 11, and an optical probe displacement detector 2 are mounted on the upper stone surface plate 106. The upper stone surface plate 106 is formed by an XY axis stage 90 that functions as an XY axis direction moving device that moves the optical probe displacement detector 2 in the XY axis direction, that is, an XY axis by the X axis stage 21 and the Y axis stage 22. Move in the axial direction. On the lower stone surface plate 23, a measurement object holding member 98 for placing and holding the measurement object 1, an X reference mirror (X-axis direction reference mirror, hereinafter simply referred to as "X reference mirror") 24, and a Y reference mirror. (Y-axis direction reference mirror, hereinafter simply referred to as “Y-reference mirror”) 25, upper Z-reference mirror (Z-axis direction reference mirror, hereinafter simply referred to as “gate-type frame” 107 fixed to the lower stone surface plate 23) Are referred to as “Z-reference mirrors”) 26. In such a configuration, XYZ three high flatness reference mirrors 24 on the axis of the measurement point of the surface S of the measurement object 1 held by the measurement object holding member 98 with the light of the oscillation frequency stabilizing laser 27, By measuring the amount of displacement at a distance of 25 and 26 with the length measuring unit, even if the movement straightness of the XY axis stage 90 (X axis stage 21 and Y axis stage 22) is on the order of 1 micron, the reference mirror A coordinate axis accuracy of the order of 10 nm, which is a flatness of 24, 25, and 26, is obtained, but only the straightness of movement of an air slide 89 as an example of a Z-axis stage can be corrected by these reference mirrors 24, 25, and 26. Not done. For this reason, the movement straightness of the Z-axis stage is the coordinate axis accuracy.

  As shown in FIG. 3, a constant load spring in which the vicinity of the center of gravity of a Z-axis direction movable portion (large air slide movable portion 11) in an air slide 89 as an example of a Z-axis stage is opposed by winding a thin plate of a spring material. By supporting the weight of the movable portion in the Z-axis direction at 17, the spring constant can be made as small as possible and moved up and down with a light force. The coils 13 are also arranged symmetrically on the left and right of the optical probe displacement detector 2 so that the resultant force of the driving force by the left and right coils 13 is applied to the vicinity of the center of gravity of the optical probe displacement detector 2 so Deterioration can be prevented.

  FIG. 4 is a diagram of a configuration of an ultra-high accuracy CMM having a configuration similar to that of the ultra-high accuracy CMM described in Patent Document 3. When the atomic force probe frame 3 is inserted under the optical probe 2A of this ultra-high-precision coordinate measuring machine, the probe 2A according to the present embodiment of the present invention can be used. Can do. That is, as an example, the three-dimensional measuring probe 2A shown in FIGS. 1 to 3 can be configured as the Z-axis of the ultrahigh-precision three-dimensional measuring machine according to this embodiment of the present invention shown in FIG.

The measuring machine according to the present embodiment includes a control unit 88 that controls an ultra-high precision three-dimensional measurement operation. The controller 88 includes an XY-axis stage 90, that is, a driving device (not shown) of the X-axis stage 21, a driving device (not shown) of the Y-axis stage 22, a He-Ne oscillation frequency stabilizing laser 27, an X-axis direction receiver 105, a Y-axis direction receiver 104, a _{Z 1} axial direction receiver 103, a _{Z 2} axial direction receiver 102, an operation unit 87 as an example of a Z coordinate computing device, Z-axis direction driving apparatus having a focus servo mechanism 43 The super-high-precision three-dimensional measurement operation is controlled by being connected to the semiconductor laser 34, the photodetector 41, and the like and performing respective operation control.

4, the oscillation frequency stabilization laser (oscillation frequency stabilization HeNe laser) 27 is a stabilization whose oscillation frequency is calibrated by measuring the beat frequency with an iodine stabilized HeNe laser whose wavelength in vacuum is the world length standard. It is a laser. The iodine stabilized HeNe laser has an oscillation frequency of 473612214.8 MHz and an uncertainty of ± 1 × 10 ⁻⁹ (3σ) (from the JIS handbook). However, this is a large-scale device with an iodine absorption cell and cannot be installed in a measuring machine. Further, the processing accuracy / dimensions required in the industry are 10 ⁻⁴ to 10 ⁻⁵ even if high accuracy. That is, for example, an axis having a diameter of 10 mm is a high precision machining with a diameter accuracy of 1 to 0.1 microns, which is a measurement limit. In the measurement of the aspherical lens according to the present embodiment of the present invention, the required uncertainty is about ± 1 × 10 ⁻⁶ , and this is the target of the uncertainty of the XYZ coordinate measurement. Further, the wavelength in the air changes by 10 ⁻⁶ with a temperature variation of 1 ° C. or a 3% atmospheric pressure change. The measuring machine is used in the atmosphere. Therefore, there is no need to mount an iodine stabilized HeNe laser on the measuring device.

Therefore, without using an iodine absorption cell, the oscillation frequency is stabilized by the neon spectrum line which is the oscillation wavelength, the oscillation frequency is 473612.112 GHz ± 0.3 GHz, and the uncertainty is ± 5 × 10 ⁻⁸ (3σ). The compact oscillation frequency stabilized HeNe laser 27 was mounted on the measuring machine. This wavelength is traceable to the world length standard because of the comparative measurement of the iodine stabilized laser and the oscillation frequency. The XYZ coordinates are measured with this laser beam Fz.

The laser beam Fz emitted from the oscillation frequency stabilizing laser 27, for example, the X-axis direction, a Y-axis direction perpendicular to the X-axis direction, and Z ₁ axial direction orthogonal to the X-axis and Y-axis directions, X branches to the Z ₂ axial direction respectively orthogonal to the axial direction and the Y-axis direction, furthermore, the laser beam Fz which is branched in the respective directions is branched into measurement light and reference light, high flatness respective measurement light respectively The X reference mirror 24, the Y reference mirror 25, the Z reference mirror 26, and the Z mirror 9 are respectively applied to the length measuring unit, that is, the X axis direction receiver 105, the Y axis direction receiver 104, and Z _1. is incident in the axial direction receiver 103, _{Z 2} axial direction receiver 102, X reference mirror 24 to XYZ coordinates by interference, Y reference mirror 25, the plane of the Z reference mirror 26 It is possible to measure with the accuracy of. Here, the Y-axis direction is a direction orthogonal to the X-axis direction. A Z ₁ axial direction and Z ₂ axial direction, respectively, a Z-axis direction along perpendicular respectively to the X-axis and Y-axis directions. Note that the Z ₁ axis direction is the direction in which the laser beam Fz travels toward the Z reference mirror 26 in FIG. 4, and the Z ₂ axis direction is the mirror provided on the stylus 5 in FIG. 4 (Z mirror in FIG. 1A). This is the direction in which the laser beam Fz travels toward 9).

  The four laser beams Fz emitted from the oscillation frequency stabilizing laser 27 are used as follows. In order to form the four laser beams Fz emitted from the oscillation frequency stabilizing laser 27, four laser light sources may be arranged, or one or four or less laser light sources may be arranged. The laser light from the laser light source may be branched as described above to form a total of four laser lights Fz.

  The first laser beam Fz emitted from the oscillation frequency stabilizing laser 27 irradiates the reflection surface of the X reference mirror 24 (surface opposite to the measurement object 1) and is reflected by the reflection surface of the X reference mirror 24. The reflected light passes through an optical system and is received by an X coordinate measuring unit (X coordinate laser length measuring unit, ie, receiver for X axis direction) 105 as an example of an X coordinate measuring apparatus, and X is measured based on the received laser light. The X coordinate of the optical probe displacement detector 2 is measured by the axial receiver 105. Here, since the X reference mirror 24 is regarded as a perfect plane, measuring the X coordinate of the X reference mirror 24 is between the optical system fixed to the upper stone upper plate 106 and the reflection surface of the X reference mirror 24. This means that the amount of displacement of the distance is measured.

  Similarly, the second laser light Fz emitted from the oscillation frequency stabilizing laser 27 is applied to the Y reference mirror 25, and the reflected light reflected by the Y reference mirror 25 is used as a Y coordinate as an example of a Y coordinate measuring device. The measurement unit (Y-coordinate laser measuring unit, ie, Y-axis direction receiver) 104 receives the light, and the Y-axis direction receiver 104 measures the Y coordinate of the optical probe displacement detector 2 based on the received laser light. Since the Y reference mirror 25 is regarded as a perfect plane, measuring the Y coordinate measures the amount of displacement of the distance between the mirror (not shown) fixed to the upper stone upper board 106 and the reflecting surface of the Y reference mirror 25. It means to do.

On the other hand, the third laser beam Fz emitted from the oscillation frequency stabilizing laser 27 is irradiated on the Z mirror 9 and reflected light reflected by the Z mirror 9 is converted into the Z ₂ coordinate measuring device (Z coordinate measuring means). As an example, the Z ₂ coordinate measuring unit (Z ₂ coordinate laser length measuring unit, ie, Z ₂ axis direction receiver) 102 receives the light, and the Z ₂ coordinate of the Z mirror 9 is changed in the Z ₂ axis direction based on the received laser beam. Measurement is performed by the receiver 102. Measuring the Z ₂ coordinate is the reflection of the Z mirror 9 from the reflection surface of a reflection mirror (not shown) fixed to the upper stone upper plate 106 that reflects the third laser beam Fz so as to enter the Z mirror 9. This means measuring the amount of displacement of the distance to the surface.

The fourth laser beam Fz emitted from the oscillation frequency stabilizing laser 27 is reflected by the reflecting surface which is the lower surface of the Z reference mirror 26 after being reflected by the mirror fixed to the upper stone upper board 106, and is converted into Z A Z ₁ coordinate measuring unit 103 (Z ₁ coordinate laser measuring unit, ie, a receiver for Z ₁ axis direction) 103 as an example of a ₁ coordinate measuring apparatus, and receiving the Z ₁ axis direction receiver 103 based on the received laser light. To measure the Z ₁ coordinate of the optical probe displacement detector 2. Measuring the Z ₁ coordinate means that the fourth laser beam Fz is reflected so as to be incident on the reflecting surface of the Z reference mirror 26, and the Z reference mirror is reflected from the reflecting surface of the mirror fixed to the upper stone surface plate 106. This means that the amount of displacement of the distance to the reflecting surface 26 is measured.

That is, the Z coordinate is obtained by measuring the 2A laser beam Fz with the third and fourth laser beams Fz from the oscillation frequency stabilizing laser 27 as follows. 4 is transmitted through the dichroic mirror 15 from the optical system of the length measuring unit on the upper stone surface plate 106, and the Z ₂ coordinate is used for the Z ₂ axis direction by the laser beam Fz which is focused by the lens 14 and reflected by the Z mirror 9. Measurement is performed by the receiver 102. The movement straightness of the XY axis stage 90 is on the order of 1 micron, but the laser beam Fz is applied to the Z reference mirror 26 having a flatness of the order of 10 nanometers from the optical system of the measuring unit on the upper stone surface plate 106. The Z ₁ coordinate is measured by the receiver 103 for Z ₁ axis direction from the reflected light of the Z reference mirror 26. Then, the Z coordinate can be measured with the accuracy of the Z reference mirror 26 by calculating the (Z ₁ coordinate + Z ₂ coordinate) by the calculation unit 87 to obtain the Z coordinate.

  Before the measurement of the three-dimensional shape of the measurement object 1 is started, the upper and lower styluses 5 of the measurement object 1 are separated from the measurement surface S of the measurement object 1, and thus the above-described focus servo is not applied. Although not shown, the optical probe displacement detector 2 is provided with a position detector in the Z-axis direction, and a position signal from the position detector is attached to the operation unit of the measuring machine and manually driven by an operator. The optical probe displacement detector 2 is moved in the Z-axis direction by the Z-axis direction driving device 43 under the control of the controller 88 so that the position command value is changed by a dial (not shown) (in other words, in other words). For example, the Z-axis direction driving device 43 is driven based on the input information generated by the operator turning the manual driving dial, and the tip of the optical probe displacement detector 2 is 5 mm or less on the measurement surface S of the measurement object 1. Can be moved to a position closer to This is called “position servo”.

  When this position servo is applied, since no measuring force is applied to the stylus 5, the lens 14 is placed in advance with respect to the probe casing 2a so that the Z mirror 9 is about 10 microns away from the focus position. Adjust in the Z-axis direction.

At the start of measurement, the measuring object 1 is placed at a position several millimeters below the stylus 5 and the operator presses a focus start button (not shown) on the operation unit of the measuring machine, so that the manual driving dial (not shown) is placed on the dial. Release the manual drive based on this and switch to automatic control. Then, the optical probe displacement detector 2 is moved slowly toward the measurement surface S in the direction of the measurement surface S by the Z-axis direction driving device 43. When the stylus 5 detects the measuring surface S (the stylus 5 touches the measuring surface S of the measuring object 1), the mirror 9 by the measuring force of the stylus 5 moves in the focus direction of the semiconductor laser beam F _L, the mirror 9 is semiconductor The movement of the laser beam _{FL in} the focus direction is detected by the focus error signal detection unit 42 by the change of the focus error signal (in other words, the mirror 9 arrives near the focus position), and then the position servo is switched to the focus servo. The Z mirror 9 comes to the focus position. That is, the optical probe displacement detector 2 is moved by the Z-axis direction driving device 43 until the focus error signal becomes zero. This is the state where the focus servo is applied.

The semiconductor laser beam F _L is to sensitively detect a focus error signal, but to be incident on the opening one lens 14 cups as shown in 2A, HeNe stabilizing laser beam Fz for measurement Z coordinate narrower than the opening of the lens 14 Since the incident light is incident with the light beam diameter, the Z coordinate can be sufficiently measured from the reflected light even if the depth of focus is about 10 microns and the Z mirror 9 is located at the defocus position.

  Next, the setting of the measurement force and the reason will be described. A measuring force acting in the axial direction of the stylus 5 shown in FIG. Since the mirror 9 is brought to the focus position by the measurement force F, the measurement force F is constant regardless of the inclination of the measurement surface S. The measuring force F can be set by moving the lens 14 in FIG. 3 up and down.

  The measurement force acting in the direction perpendicular to the measurement surface S is F / cos θ. θ is the inclination angle of the measurement surface S. As shown in FIG. 2F, the stylus 5 is subjected to a lateral measurement force of (F / cos θ) sin θ. The lateral measuring force is 1.7 times F when θ is 60 degrees, and 3.7 times F when θ is 75 degrees.

  If the stylus 5 tilts sideways due to the lateral measurement force, a measurement error occurs. In order to make this as small as possible, it is better to make the measuring force as small as possible. The smaller the measuring force, the smaller the inclination of the stylus 5 and the smaller the measurement error.

  Further, since the stylus 5 is less worn when the measuring force is smaller, the stylus 5 lasts longer.

  Further, when a soft surface such as resin is measured with a sharp stylus having a tip radius of 2 microns, the measurement surface S is damaged or a measurement error due to deformation of the measurement surface occurs. The smaller the measurement force, the better. Based on experience, the measuring force that does not bother scratches and errors is 0.2 mN or less. In addition, when measuring with a stylus having a tip radius of 0.5 mm, there is no example of scratching even on a soft surface.

  Conversely, when measuring with a stylus having a tip radius of 0.5 mm, the surface dust is measured if the measuring force is small. If the measuring force is large, it will be scraped without measuring dust. In this respect, measurement is easier when the measuring force is larger.

  A probe with a small tip radius is difficult to measure dust, but it is difficult to make a tip with good sphericity. If the sphericity of the tip is poor, the measurement accuracy will deteriorate. For this, a true sphere can be measured in advance and corrected from the data, but this takes time.

  If the mass of the movable part is the same, the larger the measuring force, the faster the response, so the measurement can be performed quickly.

  In view of the above, there is an optimum measuring power given the current technical level. That is 0.1 mN to 0.3 mN. Therefore, the measuring force is set to a center value of 0.2 mN, and the adjustment of the position of the lens 14 enables adjustment within the range of 0.1 mN to 0.3 mN.

  The small sliding shaft portion 6 is designed to move about 10 microns with respect to the small air bearing 7 with a measuring force of 0.2 mN from a position lowered by about 100 microns due to its own weight. The probe 2A can also be placed sideways, in which case it is designed to move about 10 microns from the balanced position with a measuring force of 0.2 mN, although there is no movement due to its own weight.

  The reason why the focus servo is applied at a position where the small sliding shaft 6 has moved about 10 microns with a measuring force of 0.2 mN will be described.

  The measuring force of 0.2 mN is 0.02 gram weight for the mass of the small sliding shaft 6 including the stylus 5 is about 0.2 g, so that it moves by 10 microns with one tenth of the weight of the small sliding shaft 6. The focus servo will be applied at this position.

  Even if there is an error in the focus servo, the displacement of the distance to the same mirror 9 is measured by interference with the oscillation frequency stabilized HeNe laser beam Fz, so that it does not become a measurement error but only changes in the measuring force. It is.

As shown in FIGS. 2A and 2B, since the semiconductor laser light _FL is filled in the lens 14 so that the focus sensitivity is good, the numerical aperture (NA) is about 0.4, and the lens 14 and the mirror 9 The focus servo can be applied when the variation in the displacement of the distance is 1 micron or less. That is, the measurement object 1 or the large air slide 89 is moved by the XY axis stage 90 in the XY axis directions orthogonal to the Z axis direction and orthogonal to each other, and the stylus 5 follows the shape of the measurement object 1. When moving in the Z-axis direction, the large air slide 89 is driven by the Z-axis direction driving device 43 by applying a focus servo so that the displacement in the Z-axis direction becomes substantially constant. The variation of the measuring force at this time is 0.02 mN or less.

Oscillation frequency stabilizing HeNe laser beam Fz is such that the depth of focus, has put the semiconductor laser beam _{F L} of the light flux diameter of 1~2mm intact lens 14. Then, the depth of focus is about 20 microns, and the position of the mirror 9 is displaced by 10 microns when the stylus 5 is not in contact with the measurement surface S of the measurement object 1. However, laser measurement can be performed without any problem.

  Even when the stylus 5 is not in contact with the measurement surface S, when measuring a plurality of measurement objects 1 that cannot be measured by continuous scanning unless the Z coordinate can be measured, the Z coordinate is not stored, which is very inconvenient. For example, if the magnetic force is designed to have a weak elastic coefficient so that the small sliding shaft 6 moves 20 microns with a measuring force of 0.2 mN, the position of the mirror 9 is shifted by 20 microns when the stylus 5 leaves the measuring surface S, and the length measurement is performed. The focal depth of the HeNe laser beam Fz for use is lost, and the length measurement becomes unstable.

  For example, if the magnetic force is set to a strong elastic coefficient so that the small sliding shaft 6 moves 5 microns with a measuring force of 0.2 mN, the variation in the displacement amount of the distance between the lens 1 and the mirror 9 is similarly 1 micron or less. Even if the focus servo is applied, the fluctuation of the measuring force becomes large, and when the position of the lens 9 is adjusted so that the measuring force becomes 0.1 mN, the small sliding shaft portion 6 moves only 2.5 microns. Becomes unstable.

  The above is the reason why the small sliding shaft 6 is designed to move about 10 microns with a measuring force of 0.2 mN.

  In this embodiment, the Z-axis direction movable portion (large air slide movable portion) 11 is supported by a constant load spring 17. If the Z-axis is in the lateral direction, a constant load spring is not necessary.

In the three-dimensional measurement probe configured as described above, the small sliding shaft portion 6 integrated with the Z mirror 9 is configured to be completely non-contact, and therefore, when measurement is not performed, that is, the stylus 5 and the object to be measured. When the object to be measured 1 is not in contact, it is very easy to vibrate. The laser light passing through the lens 14 in FIG. 2 hits the Z mirror 9 and the Z ₂ axis is measured by the reflected light. However, if the mirror 9 vibrates greatly, laser reading will be affected. As an example, the vibration allowed by the mirror 9 is about 20 μm although it depends on the design of the optical system. A structure for reducing vibration during non-measurement will be described below.

  As shown in FIG. 1, the atomic force probe frame 3, the upper part of the small sliding shaft portion 6 and the small air bearing portion 7 inserted to the intermediate portion of the atomic force probe frame 3, magnets 29 a and 29 b, and a yoke The transparent plate 66 is placed on a part of the atomic force probe frame 3, that is, the ring-shaped yoke 8 a so that 8 a, 8 b-1, 8 b-2 and the magnetic pin 20 are accommodated in the closed space that is substantially closed. Secure to the top surface of the. The reason why the transparent plate 66 is used as the member used for making the closed space substantially closed is that the lasers 27 and 34 for measuring the Z position of the small sliding shaft portion 6 pass through the transparent plate 66 and pass through the small sliding shaft. This is because it hits the Z mirror 9 at the top of the portion 6.

  The function necessary for the transparent plate 66 is to transmit laser light straight, and the thickness needs to be thin in order to eliminate the influence of refraction and increase the transmittance. In this embodiment, as an example, a transparent plate 66 having a thickness of 0.5 mm is used. The diameter of the transparent plate 66 may be equal to or greater than the diameter of the laser beam (for example, 5 mm). For example, the diameter of the transparent plate 66 is larger than the diameter of the laser beam in order to seal the probe. As long as the material of the transparent plate 66 has a high transmittance, there is no problem with ordinary glass. As the transparent plate 66, the flatness of the glass surface is required (for example, about λ / 4) in order to transmit the laser light straight.

  Further, below the facing portion between the yokes 8b-1 and 8b-2 and the magnetic pin 20, the periphery of the upper end portion of the small sliding shaft portion 6, the upper end surface of the small air bearing portion 7, and the atomic force probe frame 3 are provided. The air flow restricting space portion 200 in which the magnetic force generating means 95 in the probe frame is housed is formed, and the opening portion of the communication passage 201 communicating with the air flow restricting space portion 200 ( A cap 65 as an example of an air flow restricting member having a small-diameter hole 64 is fixed to a part of the atomic force probe frame 3. Thereby, the air flow in the air flow restricting space 200 above the small sliding shaft 6 is restricted. When the small sliding shaft portion 6 vibrates, an air flow is generated in the air flow restricting space portion 200 above the small slide shaft portion 6, but by making the air flow restricting space portion 200 substantially closed, As a result, the flow is limited, energy loss occurs, and the vibration of the small sliding shaft portion 6 is attenuated.

  FIG. 9A is a diagram of a model of the three-dimensional measurement probe according to the embodiment of the present invention, and FIG. 9B is a diagram showing it by a spring, a damper, and a mass. FIG. 10 is a model diagram of an air damper introduced in Patent Document 1. According to this model, the damping coefficient of the air damper due to the small diameter hole 64 of the cap 65 in the air flow restriction space 200 is c, and the air spring constant is

とすると、前記減衰係数と空気バネ定数が、それぞれ、下記の式（１）及び（２）のように求められる。

Then, the damping coefficient and the air spring constant are obtained as in the following formulas (1) and (2), respectively.

ただし、上式（１）及び（２）で各変数は以下のように求められる。

However, each variable is calculated | required as follows by the said Formula (1) and (2).

：空気の比熱比（＝１．４）

: Specific heat ratio of air (= 1.4)

：角振動数

: Angular frequency

：振動数

:Frequency

：ピストン面積

: Piston area

：シリンダ下面からピストン底面までの高さ

: Height from cylinder bottom to piston bottom

：大気圧

:Atmospheric pressure

：大気の密度

: Air density

：図１０のモデルのピストンとシリンダ間の隙間とシリンダ下面のオリフィスのそれぞれの流量係数

: Flow rate coefficients of the gap between the piston and cylinder and the orifice on the bottom of the cylinder in the model of FIG.

：図１０のモデルの隙間とオリフィスのそれぞれの面積

: Each area of the gap and orifice of the model in FIG.

：図１０のモデルのピストンの振動振幅
ここで、流量係数

: Vibration amplitude of the piston in the model of FIG.

は、図１０のモデルの隙間、オリフィスをそれぞれ通過する空気の流量を決める流量係数で、実験、流体シミュレーションにより、求めることができるが、ここでは、管路抵抗の式により、計算した。
以上により、求められた減衰係数ｃ、バネ定数

Is a flow coefficient that determines the flow rate of air passing through the gap and the orifice of the model in FIG. 10 and can be obtained by experiment and fluid simulation, but here it is calculated by the equation of the pipe resistance.
From the above, the obtained damping coefficient c and spring constant

から、図９Ｂのモデルによる、運動方程式は下記のようになる。（振動のダンピング技術（社団法人 日本機械学会編）Ｐ.１５４ 表５．５参照）

Therefore, the equation of motion according to the model of FIG. 9B is as follows. (See Table 5.5 on page 154 for vibration damping technology (edited by the Japan Society of Mechanical Engineers))

ただし、

However,

：小摺動軸部６の質量（３００ｍｇ）

: Mass of small sliding shaft portion 6 (300 mg)

：小摺動軸部６をＺ軸方向に保持する磁力発生手段９５での磁気回路の復元力によるバネ定数 （２０．９Ｎ／ｍ）
図７は、前記（５）、（６）式をルンゲクッタギル法により、シミュレーションを行なった結果である。キャップ６５の小径穴６４の直径を変えたときの振動を比較した。三次元測定プローブ２Ａに、４２Ｈｚ（固有振動数）、１［ｇａｌ］の振動を加えたときの小摺動軸部６のＺ軸方向変位を縦軸、時間を横軸としている。この図７でわかるように、小径穴６４の直径を０．５０ｍｍから、０．３０ｍｍ、０．２０ｍｍ、０．１７ｍｍと小さくすると、減衰効果が大きく、振動が小さくなることがわかる。

: Spring constant (20.9 N / m) due to the restoring force of the magnetic circuit in the magnetic force generating means 95 that holds the small sliding shaft portion 6 in the Z-axis direction.
FIG. 7 shows the result of simulation of the above equations (5) and (6) by the Runge-Kuttagill method. The vibration when the diameter of the small diameter hole 64 of the cap 65 was changed was compared. The Z-axis direction displacement of the small sliding shaft portion 6 when a vibration of 42 Hz (natural frequency) and 1 [gal] is applied to the three-dimensional measurement probe 2A is the vertical axis, and time is the horizontal axis. As can be seen from FIG. 7, when the diameter of the small-diameter hole 64 is reduced from 0.50 mm to 0.30 mm, 0.20 mm, and 0.17 mm, the damping effect is large and the vibration is reduced.

  In order to stably measure the length in the Z-axis direction, the vibration must be 20 μm or less. However, as can be seen in FIG. 7, when the hole diameter of the small-diameter hole 64 is 0.3 mm or more, vibration is generated. It can be seen that this value is exceeded.

FIG. 8 shows the relationship between the damping ratio of this model and the vibration amplitude at the time of the above-mentioned excitation by fluid simulation. According to this, in order to reduce the vibration to 20 μm or less, the damping ratio ζ is 0.007 or more. You can see that
Here, the mass of the small sliding shaft 6

、磁気回路のバネ定数

, Spring constant of magnetic circuit

により、前記振動の振幅と、減衰係数の関係は変わるので、減衰比

Since the relationship between the amplitude of the vibration and the damping coefficient changes, the damping ratio

を用いて、

Using,

に依存せず、振動に対する減衰性能を以下のように規定している。

The damping performance against vibration is specified as follows.

ただし、実際の設備で使用するときに余裕をみる場合には、０．０１以上の減衰比とするのがより好ましい。

However, it is more preferable to set the attenuation ratio to 0.01 or more in order to allow a margin when used in actual equipment.

  Note that if the attenuation is excessively increased, the measuring force F may be excessively increased. In the above-described formula of the measuring force F, it is described that F = ma and the measuring force F is 0.2 mN or less, but strictly speaking, it is expressed as F = ma + cv + kx. Here, m: mass matrix, c: damping matrix, k: stiffness matrix, a: acceleration vector, v: velocity vector, x: displacement vector. Therefore, from this equation, as an example, in order to make the measuring force F 0.2 mN or less when a 0.1 G sine wave is applied as stylus acceleration, the damping ratio ζ needs to be 0.51 or less.

As described above, when the diameter of the small-diameter hole 64 is reduced, the damping performance is improved. However, when the diameter is too small, there is no air escape from the air outlet 4 for supplying the air of the small air bearing 7. The air pressure in the air flow restricting space 200 above the small sliding shaft 6 is increased. In the case of one example of this embodiment, when the pressure exceeds 400 Pa, the holding force of the magnetic circuit is exceeded, and the small sliding shaft 6 cannot be held. The conditions of the said Example are illustrated below. The small-diameter hole 64 has a diameter of 0.17 mm and has 12 holes. The diameter of the communication path 201 is 3 mm. The communication path 201 is integrated with the air flow restricting space 200, and what is important here is the volume of the integrated space. D _c and a portion in the h _p dimension of FIG. 10 corresponds to the space became the integral. As an example, the volume of this integrated space is 4.5 × 10 ⁻⁷ m ³ . The size of the atomic force probe frame 3 is about 30 mm in diameter. The size of the small sliding shaft 6 is 4 mm in diameter. With such a configuration, the pressure exceeds 400 Pa under the condition of the portion where “pressure difference is NG” in FIG. 11.

  FIG. 11 shows the damping coefficient when the diameter (hole diameter) of the small-diameter hole 64, the length (hole depth), and the number (number of holes) of the small-diameter holes 64 are changed, and the air above the small sliding shaft portion 6. The pressure in the flow restriction space 200 is shown in a table. According to this, for example, when the diameter of the small diameter hole 64 is 0.1 mm, the length of the small diameter hole 64 is 0.5 mm, and the number of the small diameter holes 64 is 30, the pressure becomes 455 Pa and cannot be used as a probe. . FIG. 11 can determine the optimum diameter, length, and number of holes including the processing cost. In the determination column in FIG. 11, conditions other than the column described as NG mean usable conditions.

  From FIG. 11, it is preferable that the diameter of the small-diameter hole 64 formed in the cap 65 is 0.05 mm or more and less than 0.6 mm. This is because if the diameter of the small-diameter hole is less than 0.05 mm, the pressure in the sealed portion of the probe 2A will increase, and it will not be possible to hold it magnetically. Therefore, it is necessary to increase the number of small-diameter holes 64 as the diameter of the small-diameter holes 64 is reduced. As an example, 60 small-diameter holes 64 may be provided as shown in FIG. Since it is not practical to open more than 60 small-diameter holes 64 having a diameter of 0.05 mm or less, the number thereof is set to 60 or less as an example.

  The minimum number of small diameter holes 64 is one. This is because, in FIG. 11, even when the diameter of the small diameter hole 64 is 0.5 mm, the attenuation coefficient can be set to a predetermined value.

  FIG. 11 shows that the attenuation coefficient does not become a predetermined value when the diameter of the small-diameter hole 64 is 0.6 mm and only one hole is opened. Therefore, if the diameter of the small-diameter hole 64 is 0.6 mm or more, the attenuation coefficient does not become a predetermined value. Therefore, the diameter of the small-diameter hole 64 is preferably less than 0.6 mm.

  As can be seen from FIG. 11, it can be seen that making more holes with smaller diameters can increase the damping coefficient and reduce the pressure difference, but this is disadvantageous in terms of processing cost. As a method for solving this, as another example of the air flow restricting member, instead of the cap 65 having the small-diameter hole 64, as another specific example of the small-diameter hole, a cap made of a porous material having a large number of micropores It is also possible to use.

  As described above, according to the present embodiment, the magnetic pin 20 having a small movable part mass, the magnets 29a and 29b attached to the small air bearing part 7, and the yokes 8a, 8b-1, and 8b-2 are used for the magnetic circuit. In the three-dimensional measurement probe 2A that can limit the movement in the axial direction in a non-contact manner, the air flow in the air flow restricting space 200 in the portion where the magnetic force generating means 95 is configured. Is restricted by a cap 65 having a small-diameter hole 64 as an example of an air flow restricting member, thereby causing energy loss when the small sliding shaft portion 6 vibrates, thereby attenuating the vibration of the small sliding shaft portion 6. Thus, the vibration of the small sliding shaft portion 6 can be suppressed. Therefore, the vibration of the small sliding shaft portion 6 when not in contact with the measurement object 1 can be suppressed, and stable measurement can be performed.

  As a result, a pair of the three-dimensional measurement probes 2A are prepared and arranged on the front and back surfaces of an aspheric lens as an example of the measurement object 1, and the front and back surfaces of the aspheric lens are measured simultaneously. It becomes possible to measure stably with ultra-high accuracy. In the three-dimensional measurement probe 2A, the magnetic force generation means 95 generates a magnetic force that prevents the small sliding shaft 6 from moving in the Z-axis direction, which is the axial direction. Therefore, it is possible to realize the three-dimensional measurement probe 2A with higher accuracy and less likely to be broken even after long-term use. Furthermore, assembly and handling become easy, so if you use this probe 2A, you can place it on a factory site and measure it easily from a measuring instrument used only by a limited number of people in the measurement room. It becomes.

  As a result, it is possible to improve the performance, quality, and production yield of lenses such as cameras that are becoming thinner and higher in image quality, and optical disks that are becoming larger in recording capacity.

  It is to be noted that, by appropriately combining any of the various embodiments, the effects possessed by them can be produced.

  The three-dimensional measurement probe of the present invention can measure the shape of the measurement surface of the measurement object from below or from the side with an ultra-high accuracy of the order of 0.01 microns, so that the front and rear surfaces (for example, the upper and lower surfaces) of the measurement object can be measured simultaneously. By measuring, the tilt eccentricity of the aspherical lens can be measured with extremely high accuracy. In addition, the probe itself is hard to break and has a long life, and it has the effect of being able to use the probe easily and frequently at the measurement site. This probe further improves the accuracy and production yield of aspherical lenses that cannot be made without measurement. It can be realized by use, and can contribute to performance improvement and cost reduction of products with built-in aspherical lenses, such as digital cameras, movies, mobile phones with cameras, and optical disks with increased capacity. In addition, the probe has a wide range of applications in research and development of medical equipment, automobile gears, nanotechnology and micromachines.

Sectional drawing of the three-dimensional measurement probe in embodiment of this invention Sectional drawing of the three-dimensional measurement probe in embodiment of this invention Structure explanatory drawing including the optical probe part on the upper side of the three-dimensional measurement probe in the embodiment of the present invention Configuration explanatory diagram including the lower optical probe portion of the three-dimensional measurement probe in the embodiment of the present invention The perspective view which is the principal part of the three-dimensional measuring probe in the said embodiment of this invention, Comprising: The relationship between a ring-shaped yoke and a magnetic body pin is shown The bottom view which is the principal part of the three-dimensional measuring probe in the said embodiment of this invention, and shows the relationship between the front-end | tip of the other yoke different from a ring-shaped yoke, and the front-end | tip of a magnetic body pin The side view which is the principal part of the three-dimensional measuring probe in the said embodiment of this invention, and shows the relationship between the front-end | tip of the other yoke different from a ring-shaped yoke, and the front-end | tip of a magnetic body pin. Explanatory drawing regarding the measuring force of the three-dimensional measuring probe in the embodiment of the present invention Configuration diagram of the Z-axis of the three-dimensional measurement probe in the embodiment of the present invention Configuration diagram of an ultra-high-precision coordinate measuring machine to which the coordinate measuring probe of the present invention described in Patent Document 3 can be attached In the three-dimensional measurement probe of the present invention, a graph showing vibration when no vibration countermeasure is taken The graph showing the vibration of the three-dimensional measurement probe of the present invention In the three-dimensional measurement probe of the present invention, a graph showing a comparison of vibration when the diameter of the small hole is changed In the three-dimensional measurement probe of the present invention, a graph showing the relationship between the diameter of the small hole and the attenuation coefficient Model diagram for briefly explaining the three-dimensional measurement probe of the present invention Model diagram for briefly explaining the three-dimensional measurement probe of the present invention Model of dynamic pressure air damper The figure which shows the table | surface which put together the attenuation performance by the difference in the small diameter hole in the three-dimensional measuring probe of this invention, and the difference in a pressure difference. Diagram of conventional three-dimensional measurement probe described in Patent Document 1 Diagram of conventional three-dimensional measurement probe described in Patent Document 2 Configuration diagram of the ultra-high accuracy CMM described in Patent Document 3 Configuration diagram of a conventional contact probe described in Patent Document 4 The bottom view which looked at the yoke and permanent magnet of the conventional contact-type probe described in patent document 4 from the bottom CC sectional view of FIG. 14B

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measured object 2 Optical probe displacement detection part 2A Optical probe 3 Atomic force probe frame 4 Air ejection opening 5 Stylus 6 Small sliding shaft part 7 Small air bearing 8a Ring-shaped yoke 8b-1, 8b-2 Yoke 9 Z Mirror 10 Air outlet 11 Large air slider movable part 12 Large yoke 13 Coil 14 Lens 15 Dichroic mirror 17 Constant load spring 18 Air reservoir 20 Magnetic body pin 21 X-axis stage 22 Y-axis stage 23 Lower stone surface plate 24 X reference mirror 25 Y reference mirror 26 Z reference mirror 27 He-Ne oscillation frequency stabilizing laser 28 Large magnets 29a, 29b Magnet 32 Lens 33 Wave plate 34 Semiconductor laser 35 Large air slide guide 38 Lens 39 Half mirror 40 Pinhole 41 Photo detector 42 Focus error signal detector 43 Z-axis drive device 48D Over tube 50 the leaf spring 53 spring receiving ball 61 stylus-tip sphere 64 small-diameter hole 65 cap 66 transparent plate 95 the magnetic force generating means 102 _{Z 2} Receiver 103 _{Z 1} Receiver 104 Y Receiver 105 X Receiver 106 upper millstone platen 200 air flow restricting space 201 communication path

Claims (9)

A small sliding shaft with a stylus in contact with the surface of the object to be measured at one end and a pin made of a magnetic material at the other end;
A small air-bearing portion that is formed in a probe frame having a hole for fitting with the small-sliding shaft portion and having an air ejection portion that forms a film of compressed air in a gap with the small-sliding shaft portion When,
A magnet and a yoke attached to the end of the small air bearing portion form a magnetic circuit in a non-contact manner with the pin, thereby generating a magnetic force that prevents movement of the small sliding shaft portion in the Z-axis direction, which is the axial direction. Magnetic force generating means for generating,
A transparent plate is provided in the probe frame to make the air flow restricting space in which the magnetic force generating means in the probe frame is accommodated substantially closed, and a part of the closed space communicates with the outside of the probe frame. By providing an air flow restricting member having a small-diameter hole, the air flow in the air flow restricting space is restricted so that the damping ratio with respect to vibration of the small sliding shaft is 0.007 or more. A three-dimensional measurement probe. A displacement detecting means for detecting a displacement in the Z-axis direction of the small sliding shaft portion with respect to the small air bearing portion;
A Z-axis stage for moving the small air bearing in the Z-axis direction;
The displacement in the Z-axis direction generated by the movement of the stylus in the Z-axis direction along the shape of the measurement object during shape measurement for moving the measurement object or the Z-axis stage in the XY-axis direction is substantially constant. The three-dimensional measurement probe according to claim 1, further comprising: a Z-axis stage driving device that drives the Z-axis stage.   The displacement detecting means includes a mirror formed on the small sliding shaft portion, an optical probe fixed integrally with the small air bearing portion and including at least a semiconductor laser, a lens, and a photodetector, Laser light emitted from the semiconductor laser is irradiated to the mirror through the transparent plate via the lens, and reflected light from the mirror is received by the photodetector, and the output signal of the photodetector detects the The three-dimensional measurement probe according to claim 2, wherein the three-dimensional measurement probe is configured to detect a displacement in the Z-axis direction. An oscillation frequency stabilized laser that emits an oscillation frequency stabilized laser beam;
Means for irradiating the mirror with the oscillation frequency stabilized laser beam emitted from the oscillation frequency stabilized laser through the transparent plate, and measuring the Z coordinate of the mirror from the reflected light from the mirror. Item 4. The three-dimensional measurement probe according to item 3.   The three-dimensional measurement probe according to any one of claims 1 to 4, wherein the Z-axis stage is configured by an air bearing.   The three-dimensional measurement probe according to claim 1, wherein the Z-axis stage driving unit includes a coil and a magnetic circuit.   The three-dimensional measurement according to any one of claims 1 to 6, wherein the movable part of the Z-axis stage is supported by a constant-load spring made of a spirally wound thin plate that generates a tension substantially equal to its weight. probe.   The air flow restricting member is a cap in which a part of the air flow restricting space portion, which is the closed space, closes an opening of a communication passage communicating with the outside of the probe frame, and is damped against vibration of the small sliding shaft portion. In order to make the ratio 0.007 or more and make the pressure of the air flow restriction space part 400 Pa or less, the diameter of the small-diameter hole formed in the cap is 0.05 mm or more and less than 0.6 mm, and the number The three-dimensional measurement probe according to claim 1, wherein the number is from 1 to 60.   The air flow restricting member is a cap in which a part of the air flow restricting space portion, which is the closed space, closes an opening of a communication passage communicating with the outside of the probe frame, and is damped against vibration of the small sliding shaft portion. In order to make the ratio 0.007 or more and make the pressure in the air flow restriction space part 400 Pa or less, the air flow is restricted using a porous material instead of the small diameter hole. The three-dimensional measurement probe according to claim 1, wherein:

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