JP2005106797A - Measuring device, system, and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring device which measures the displacement or the irregularity of an object surface with high accuracy. <P>SOLUTION: A reflection light from the measuring plane X of the object is divided into two light fluxes by a half mirror BS2, the light quantity is measured with a photodiode PD1 via a pinhole A1 and the photodiode PD2 via the pinhole A2. The pinhole A1 is set at a position which is located at more remote position than the position of the focal length f1 of an ocular L1 located before the half mirror BS2, and the pinhole A2 is set at the position which is located at closer position than the position of the focal length f1. So, the light receiving quantities S1, S2 of the photodiodes PD1, PD2 are increased and decreased corresponding to the displacement of the measuring plane X, respectively. The displacement of the measuring plane X can be obtained with a high accuracy corresponding to the light receiving quantities S1, S2, by performing the preliminary measurement of the change of the light receiving quantities S1, S2 due to the displacement. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a measuring apparatus, a measuring system, and a measuring method for measuring displacement of an object surface or unevenness of an object surface.

  As examples of a displacement sensor / displacement meter for measuring the displacement of the surface of an object, a laser focus displacement meter and a CCD (Charge Coupled Device) laser displacement sensor are known.

  The laser focus displacement meter measures displacement according to the following principle. First, a laser beam is irradiated from a light source, and is transmitted through an objective lens so as to be focused on a surface to be measured (hereinafter referred to as a measurement surface for simplicity). The reflected light from the measurement surface is guided to a different optical path from the incident light by the semi-transparent mirror, and is transmitted through the pinhole and received by the light receiving surface. Here, the reflected light is set to pass through the pinhole only when the light passing through the objective lens is focused on the measurement surface. In this case, if the reflected light passes through the pinhole, the amount of light received at the light receiving surface increases. The objective lens is moved up and down at a high speed with a tuning fork, and the change in the amount of received light according to the change in the position of the objective lens is measured. Depending on the position of the objective lens when the amount of received light is maximized, the distance to the measurement surface can be obtained using the focal length of the objective lens.

  The CCD laser displacement sensor is a method applying triangulation. Light from a light source (semiconductor laser) is condensed through a projection lens and irradiated onto the measurement surface. A part of the diffusely reflected light from the measurement surface is imaged on the CCD through the light receiving lens. From the movement of the spot according to the movement of the measurement surface, the distance to the measurement surface is accurately measured.

  Such a displacement sensor / displacement meter is manufactured, for example, by Keyence Corporation and put into practical use (see Non-Patent Document 1).

Further, for the purpose of examining the fundus of humans, Patent Documents 1 and 2 disclose a three-dimensional shape measuring apparatus that measures a three-dimensional shape using a laser.
Japanese Patent Laid-Open No. 1-1113605 (Publication date: May 2, 1989) Japanese Patent Laid-Open No. 5-71931 (Publication date: March 23, 1993) Keyence, 2004 General Catalog, pages 694 to 695

  However, the above-described configuration causes a problem that a sufficient measurement range cannot be obtained and sufficient accuracy may not be obtained.

  That is, the laser focus displacement meter adjusts the focal position by moving the objective lens in order to measure the displacement. For this reason, there exists a problem that a measurement range will be restrict | limited according to the movable range of the objective lens of about +/- 0.3 mm, for example.

  In addition, since the objective lens in the optical system is moved, it takes time to align the objective lens. For this reason, there is a problem that measurement in real time becomes difficult.

  In addition, since the CCD laser displacement sensor reads changes in the spot position on the CCD, the optical system becomes relatively complicated and there is a possibility that sufficient accuracy may not be obtained.

  In addition, the configurations described in Patent Documents 1 and 2 are intended for human fundus inspection, and when a worn surface that is a rough surface having irregularities is a measurement target, the data is relatively A large error may occur and sufficient accuracy may not be obtained.

  The present invention has been made in view of the above-described problems, and its purpose is to measure a displacement of an object or unevenness of the surface of the object with high accuracy and in real time within a sufficient measurement range, It is to provide a measurement system and a measurement method.

  In order to solve the above problems, a measuring apparatus according to the present invention is a measuring apparatus that measures the displacement of the measured surface of the object by detecting the reflected light from the measured surface of the object. A distributor for distributing the first optical path to a second optical path different from the first optical path, a first optical element for detecting the reflected light from the distributor via the first optical path, and a second optical path from the distributor. A second optical element that detects the reflected light through two optical paths, and an amount of light incident on the first optical element in accordance with a change in the reflected light from the object that accompanies a displacement of the measured surface of the object. And a light amount changing means for changing the amount of light incident on the second optical element so as to be different from the first optical element.

  In order to solve the above-described problems, the measuring apparatus according to the present invention is configured so that, in the above-described configuration, the light amount changing means is provided on the first light shielding member provided on the first optical path to the first optical element and the second optical element. A second light-shielding member provided on the second light path, and a collecting path provided on the optical path to the distributor of the reflected light for condensing the reflected light in the vicinity of the first light-shielding member and the second light-shielding member. And an optical member.

  In order to solve the above-described problem, the measuring apparatus according to the present invention is configured so that, in the above configuration, one of the first light-shielding member and the second light-shielding member, It arrange | positions in the near side rather than the focal position of a condensing member, and arrange | positions the other side in the far side rather than the said focal position of the said condensing member, It is characterized by the above-mentioned.

  In order to solve the above-described problem, the measuring apparatus according to the present invention has the above-described configuration, wherein the reflected light is limited by blocking a part of the reflected light in the optical path to the distributor of the reflected light. A third light shielding member is provided for guiding the remaining portion of the first light shielding member to the first light shielding member and the second light shielding member.

  In order to solve the above-described problems, the measurement system according to the present invention receives any of the above-described measurement apparatuses and outputs from the first optical element and the second optical element, and the displacement of the surface to be measured of the object. In accordance with the above, by measuring the amount of light received by the first optical element and the second optical element of the measuring device, a calculation for determining and storing in advance the relationship between the displacement of the measured surface of the object and the amount of received light And a device.

  In order to solve the above-described problem, the measurement system according to the present invention includes a friction force sensor that measures a friction force generated on the surface to be measured of the object in the above configuration, and the friction force sensor measures the friction measured. Force data is output to the calculation device.

  In order to solve the above-described problem, the measurement system according to the present invention includes an acceleration sensor that detects a component of the friction force measured by the friction force sensor in the configuration, and the acceleration sensor measures the friction. It is characterized in that data of force components is output to the calculation device.

  In order to solve the above problems, the measurement method according to the present invention is a measurement method for measuring the displacement of the measurement surface of the object by measuring the amount of reflected light from the measurement surface of the object. The reflected light from the surface to be measured is divided into a plurality of light beams, and the amount of reflected light is measured for each of the divided light beams, thereby measuring the displacement of the surface to be measured of the object.

  In order to solve the above-described problem, the measurement method according to the present invention is configured so that, in the above configuration, the reflected light from the measured surface of the object is non-uniform in intensity on the irradiated surface when the reflected light is irradiated. Then, the light beam is divided into the plurality of light fluxes after passing through an averaging means for reducing the above.

  As described above, the measuring apparatus according to the present invention distributes the reflected light to the first optical path and the second optical path different from the first optical path, and the above-described distributor via the first optical path from the distributor. A first optical element that detects reflected light; a second optical element that detects the reflected light from the distributor via a second optical path; and the reflected light from the object that accompanies displacement of the surface to be measured of the object. And a light amount changing means for changing the amount of light incident on the second optical element so as to change the amount of light incident on the first optical element. It is a configuration.

  The measurement apparatus measures the displacement of the surface to be measured of the object by detecting reflected light from the surface to be measured of the object. More specifically, the measuring device irradiates the surface to be measured of the object with light generated by a light emitting unit made of, for example, a laser via an objective lens having a predetermined focal length. Reflected light from the surface to be measured of the object is distributed to the first optical path and the second optical path by the distributor through the objective lens.

  In the first optical path, the light passing through the light amount changing means that changes the amount of light incident on the first optical element in accordance with the change in the reflected light from the measured surface of the object accompanying the displacement of the measured surface is the first light path. Incident on one optical element. Also in the second optical path, the light passing through the light amount changing means that changes the amount of light incident on the second optical element in accordance with the change in the reflected light from the measured surface of the object accompanying the displacement of the measured surface. , Enters the second optical element. Here, the first optical element and the second optical element are light receiving elements such as photodiodes, for example, and output an electrical signal corresponding to the amount of received light. The optical element is not limited to a photodiode.

  The light amount changing means is for changing the amount of light incident on the light receiving element, that is, the amount of light received by the light receiving element, according to the change in reflected light. In particular, the amounts of light received by the first and second light receiving elements are changed in accordance with changes in reflected light.

  The light quantity changing means can be configured using, for example, a lens and a pinhole. A lens having a predetermined focal length is disposed in the optical path, and a pinhole is disposed near the focal position of the lens. In this state, when a change in the reflected light according to the displacement of the surface to be measured occurs, the focal position of the reflected light after the change moves to a position before and after the focal position before the change. At the same time, at the position of the pinhole, the cross-sectional area of the reflected light beam increases or decreases according to the change in the reflected light. Therefore, if the size of the pinhole hole is appropriately set according to the cross-sectional shape of the reflected light beam, the amount of light received by the light receiving element via the pinhole changes appropriately according to the change in the reflected light. You can do that. The light amount changing means is not limited to the lens and the pinhole.

  Here, considering one light receiving element and the light quantity changing means therefor, as can be seen from the fact that a lens and a pinhole are cited as examples of the light quantity changing means, the displacement (size, direction) of the surface to be measured In some cases, the amount of light received by the optical element does not change despite the change in the reflected light from the object. Further, even if the amount of light received by the optical element changes, this change may not necessarily correspond one-on-one with the displacement (size, direction) of the surface to be measured.

  Therefore, as described above, the reflected light is separated into two light beams by the distributor, guided to the first optical path and the second optical path, and detected by the first optical element and the second optical element, respectively. When the surface to be measured of the object is displaced, the light amount changing means changes the amount of light received by the first optical element and changes the amount of light received by the second optical element so as to be different from the change of the amount of received light by the first optical element. . Therefore, with this configuration, for example, even when the change in the amount of received light according to the displacement of the surface to be measured does not occur in the first optical element, the change in the amount of light can occur in the second optical element. The same applies to the reverse case. In this way, a change in the amount of light can be obtained in at least one of the optical elements.

  Therefore, according to the above configuration, by appropriately providing the light amount changing means, the displacement (size, direction) of the surface to be measured of the object, and the change in the amount of received light in each of the first optical element and the second optical element, However, it is possible to correspond one-to-one. For this reason, for example, if the change in the amount of received light is measured in advance by experimentally displacing the surface to be measured of the object, and the relationship between the displacement of the surface to be measured and the change in the amount of received light is obtained, then the change in the amount of received light The displacement of the measured surface of the object can be obtained. Further, for example, if the reflected light is detected in the first light receiving element and the second light receiving element as described above while changing the position where the light emitting unit irradiates the surface to be measured, It is also possible to detect the displacement of the surface according to the position change, that is, the unevenness of the surface of the object.

  As described above, according to the measuring apparatus of the present invention, it is not necessary to move the objective lens or to adjust the focal position of the objective lens when measuring the displacement of the surface to be measured. For this reason, the measurement range is not limited according to the movable range of the objective lens. In addition, since no waiting time is required for adjusting the focal position of the objective lens, real-time measurement is possible. In addition, the measuring apparatus can obtain the displacement of the surface to be measured only by the amount of received light. For example, since it is not necessary to read the change of the spot position, the system configuration becomes simple and the apparatus can be easily manufactured. It becomes.

  The measuring apparatus uses light beams incident on the first light receiving element and the second light receiving element as equivalent signal light. Therefore, unlike the case where the amount of received light is detected using only one of the first light receiving element and the second light receiving element, the displacement (size, direction) of the measured surface of the object and the change in the amount of received light correspond one-to-one. Can be made. In addition, if the sum signal or difference signal of the obtained signals is generated using the amount of light received by the first light receiving element and the amount of light received by the second light receiving element, the detection accuracy is improved as compared with the case where only one is used. it can.

  As described above, in the measurement apparatus according to the present invention, in the above configuration, the light amount changing unit includes the first light shielding member provided on the first optical path to the first optical element, and the second to the second optical element. A second light shielding member provided on the optical path, and a light collecting member provided on the optical path to the distributor of the reflected light for condensing the reflected light in the vicinity of the first light shielding member and the second light shielding member. It is the structure containing.

  The first light-shielding member and the second light-shielding member (light-shielding member) are members for limiting and shielding a part of the incident light beam. The light shielding member is, for example, a pinhole. Note that the light shielding member may allow the incident light to pass through without any limitation depending on the beam cross-sectional shape of the incident light.

  The condensing member is a member that condenses incident light at a predetermined position (focal position). The condensing member is, for example, a lens.

  If the condensing member condenses the reflected light in the vicinity of the first light shielding member and the second light shielding member as in the above configuration, when the reflected light changes according to the displacement of the measured surface of the object, The amount of reflected light through the first light shielding member and the second light shielding member can be greatly changed. Therefore, the above-described measuring apparatus can be obtained by realizing the light amount changing means with this configuration.

  As described above, in the measurement apparatus according to the present invention, in the above configuration, one of the first light shielding member and the second light shielding member is used as the light collecting member in the optical path where the light collecting member collects the reflected light. It is the structure which arrange | positions the other side on the far side rather than the said focal position of the said condensing member, while arrange | positioning on the near side from this focal position.

  For example, it is assumed that the first light shielding member is disposed on the far side of the focal length and the second light shielding member is disposed on the near side of the focal length. At this time, the change in the amount of light received by the first light receiving element and the second light receiving element according to the displacement of the surface to be measured of the object increases and decreases in opposite directions as described below.

  That is, for example, when the measured surface of an object is displaced closer to the measuring device and the reflected light changes in accordance with this displacement, the reflected light is condensed at a position slightly further than the original focal position by the condensing member. Is done. At this time, in the first light-shielding member, the amount of light that is shielded is less than before the displacement, so the amount of light received by the first light-receiving element increases. On the other hand, in the second light-shielding member, it is considered that the cross-sectional shape of the beam becomes large, so that the amount of light received by the second light-receiving element decreases. Further, when the measured surface of the object is displaced to the side far from the measuring device, the amount of light received by the first light receiving element is decreased and the amount of light received by the second light receiving element is increased for the opposite reason.

  Therefore, the amount of change can be doubled by obtaining a difference signal for the electrical signal corresponding to the amount of light received by the first light receiving element and the second light receiving element, thereby improving the accuracy.

  Further, as described above, the measuring apparatus according to the present invention is configured so that, in the above configuration, the reflected light is limited by blocking a part of the reflected light in the optical path to the distributor of the reflected light. A third light shielding member is provided to guide the remaining part to the first light shielding member and the second light shielding member.

  A part of the reflected light from the measured surface of the object is blocked by the third light blocking member, and the remaining part is guided to the first light blocking member and the second light blocking member via the distributor. The reflected light is detected by the first optical element via the first light shielding member and detected by the second optical element via the second light shielding member.

  Here, the third light shielding member shields a part of the reflected light and allows only the remaining part to pass. When the reflected light has a variation in intensity in the beam cross section, the third light shielding member shields a part of the reflected light and allows only the remaining part to pass, whereby the variation in the beam intensity after passing through the third light shielding member can be reduced. That is, the third light shielding member functions as an averaging means that reduces non-uniformity of the beam intensity.

  As a result, it is possible to reduce variations in the intensity of reflected light guided to the first light shielding member and the second light shielding member. For this reason, even when there is an error in the attachment positions of the first light shielding member and the second light shielding member, the error in the light intensity incident on the first optical element and the second optical element can be reduced, and the measurement error can be reduced.

  For example, even when the surface to be measured of the object is a worn surface under friction, it is possible to reduce the measurement error by reducing the variation in beam intensity as described above.

  As described above, the measurement system according to the present invention receives any one of the above-described measurement devices and outputs from the first optical element and the second optical element, and responds to the displacement of the measured surface of the object. A calculation device for determining and storing the relationship between the displacement of the measured surface of the object and the received light amount in advance by measuring the received light amount in the first optical element and the second optical element of the measuring device; It is the composition which contains.

  In this way, by measuring the amount of light received by the first optical element and the second optical element of the measuring device in accordance with the displacement of the surface to be measured of the object, the calculation device previously determines the displacement of the surface to be measured and the amount of light received. The relationship is determined and memorized. As a result, when the amount of received light is obtained by the measurement device, the displacement of the measured surface of the object can be obtained from the relationship between the received light amount and the displacement of the measured surface by the calculation device, so that the displacement can be measured easily and in real time. Is possible.

  As described above, the measurement system according to the present invention includes a friction force sensor that measures the friction force generated on the surface to be measured of the object in the above configuration, and the friction force sensor measures the friction force data. Is output to the calculation device. Further, as described above, the measurement system according to the present invention includes, in the above configuration, an acceleration sensor that detects a component of the friction force measured by the friction force sensor, and the acceleration sensor measures the friction force measured by the acceleration sensor. This is a configuration for outputting the data of the constituent components of the above to the calculation device.

  As a result, a comprehensive tribological phenomenon can be observed by further measuring the frictional force and the components of the frictional force. Further, since the displacement of the measurement surface can be measured by the measurement device, the relationship between the friction force and the friction surface can be obtained.

  As described above, the measurement method according to the present invention divides the reflected light from the surface to be measured of the object into a plurality of light beams, and measures the amount of reflected light for each of the divided light beams. This is a configuration for measuring the displacement.

  As described above, if each light beam is detected as equivalent signal light, the displacement of the surface to be measured of the object can be measured using the respective reflected light amounts, so that it is not necessary to move the objective lens. For this reason, there is no limitation on the measurement range in accordance with the movable range of the objective lens, and since no waiting time for focus position adjustment is required, real-time measurement is possible.

  As described above, the measurement method according to the present invention reduces the intensity non-uniformity on the irradiated surface when the reflected light is irradiated from the measured surface of the object in the above configuration. And then splitting it into the plurality of light fluxes after passing through the averaging means.

  After the non-uniformity (intensity variation) of the intensity of the reflected light is reduced by the averaging means, it is divided into a plurality of light beams and the reflected light quantity is measured. For this reason, since the reflected light to be measured can be reduced in intensity variation, measurement errors can be reduced.

  The measuring apparatus according to the present invention divides the reflected light from the surface to be measured of the object into two light fluxes, and uses the light intensity of both of them equally, so that the sensitivity of the surface to be measured and the S / N ratio ( The signal-to-noise ratio) and, ultimately, the resolution can be improved over the conventional method.

[Embodiment 1]
An embodiment of the present invention will be described with reference to FIGS. 1 to 9 as follows.

  As shown in FIG. 1, the measurement system 1 of this embodiment includes a measurement device 2 and a personal computer (computer) (calculation device) 3. This measurement system 1 is a system for measuring unevenness of a surface to be measured (not shown) (hereinafter referred to as a measurement surface for simplicity). In the present embodiment, the measurement system 1 uses a surface that dynamically wears as a measurement surface, and measures the unevenness of the measurement surface in real time.

  As shown in FIG. 1, the measuring device 2 includes a control unit 4, a measuring unit 5, an amplifier 6, and an A / D (Analog / Digital) converter 7. The measuring device 2 transmits data measured on the surface unevenness of the measurement surface to the personal computer 3. The personal computer 3 creates and stores data of the measurement surface position D1 and the calibration curve D2 based on the data input from the measuring device 2, respectively.

  The control unit 4 of the measuring device 2 is for controlling the entire measuring device 2. The measurement unit 5 includes a laser 8, a light receiving unit 9, and an optical member 10. The measurement unit 5 outputs light from the laser 8 under the control of the control unit 4, irradiates the measurement surface via the optical member 10, and detects reflected light at the light receiving unit 9. The measuring unit 5 outputs an analog signal corresponding to the detected amount of received light to the amplifier 6.

  The amplifier 6 is a device that amplifies an analog signal, and amplifies the analog signal input from the light receiving unit 9 of the measuring unit 5 and outputs the amplified analog signal to the A / D converter 7. The A / D converter 7 converts an analog signal into a digital signal. The A / D converter 7 of the present embodiment converts the analog signal input from the amplifier 6 into a 12-bit digital signal and outputs it to the personal computer 3 connected to the measuring device 2.

  Here, the more detailed structure of the measurement part 5 of this embodiment is demonstrated based on FIG.

  The two photodiodes (light receiving elements) PD1 and PD2 shown in FIG. 2 correspond to the light receiving unit 9 of the measuring unit 5 shown in FIG. Further, the pinholes A1 and A2, the objective lens L0, the eyepiece lens L1, and the half mirrors (semi-transparent mirrors and beam splitters) BS1 and BS2 correspond to the optical member 10 shown in FIG. Note that the eyepiece L1 (light condensing member), the pinhole A1 (first light shielding member), and the pinhole A2 (second light shielding member) are connected to the photodiodes PD1 and PD2 according to changes in reflected light from the measurement surface X. It functions as a light amount changing means for changing the amount of incident light. The measurement unit 5 may include a movable unit (not shown) for moving the optical member 10. In this embodiment, this movable part is used, for example, for adjusting in advance the positions of the pinholes A1 and A2 of the optical member.

  The laser 8 of this embodiment is a He—Ne laser with a wavelength λ = 632.8 nm.

  Parallel laser light I is output from the laser 8 and passes through the half mirror BS1 and the objective lens L0 in this order, and enters the measurement surface X of the object. Here, the focal length of the objective lens L0 is f0, and the object is arranged so that the distance from the objective lens L0 to the measurement surface X is close to f0.

  The light reflected from the measurement surface X passes through the objective lens L0, is reflected by the half mirror BS1, and enters the eyepiece lens L1. The focal length of this eyepiece is f1. The light that has passed through the eyepiece lens L1 is divided into two light fluxes, a light flux directed toward the photodiode PD1 and a light flux directed toward the photodiode PD2, by the half mirror BS2. The light beam passing through the half mirror BS2 enters the photodiode PD1 through the pinhole A1 disposed at a position farther than the focal length f1 of the eyepiece lens L1. The light beam reflected by the half mirror BS2 enters the photodiode PD2 via the pinhole A2 disposed at a position closer to the focal length f1 of the eyepiece lens L1.

  Here, the change in the amount of incident light on the photodiodes PD1 and PD2 according to the surface irregularities of the measurement surface X will be described in more detail.

  As shown in FIG. 2, the laser light I collimated in parallel passes through the half mirror BS1 and is focused on the measurement plane X by the objective lens L0. Since the measurement surface is usually a rough surface, the laser beam I is reflected in all directions therefrom. Of these reflected lights, the reflected light incident on the objective lens L0 (focal length f0) is converted again into parallel light and transmitted upward, and is incident on the eyepiece lens L1 (focal length f1) by BS1. Focused on the focal plane of L1.

  In the present embodiment, as shown in FIG. 2, the light from the eyepiece lens L1 is separated and distributed into two light beams by inserting a half mirror BS2. The transmitted light in the half mirror BS2 is received by the photodiode PD1 far from the focal plane. The reflected light from the half mirror BS2 is received by the photodiode PD2 closer to the focal plane. In addition, pinholes A1 and A2 are arranged on the front surfaces of these light receiving elements (photodiodes PD1 and PD2), respectively.

  Further, the focal lengths f0 and f1, the size of the pinhole, the distances a1 and a2 from the pinhole to the light receiving element, etc. are all used for adjusting the optical system. In particular, the measurement sensitivity is adjusted using f0 and f1 and the size P of both pinholes. Further, a1 and a2 are used to equalize the light intensity incident on both light receiving elements at the reference measurement surface position. An example of these specific dimensions will be described later.

  The details of the change in the amount of light according to the movement of the measurement surface in such an optical system will be described with reference to FIGS.

  FIG. 3A shows a state in which the uneven measurement surface is a focal plane that coincides with the focal length f0 of the objective lens L0. It is assumed that the focal plane of the objective lens L0 is Δd = 0, and the measurement plane displacement Δd is positive when the measurement plane is located in a direction farther than that. Further, when Δd = 0, the size P of the pinholes A1 and A2, the position of the pinholes, etc. so that the light intensity reflected by the measurement surface and received by the photodiodes PD1 and PD2 is equal to each other. Adjust.

  In this state, when the measurement surface is up (Δd <0) and down (Δd> 0), the light intensity at each light receiving element increases or decreases in the opposite direction.

  For example, as shown in FIG. 3B, when the measurement surface is raised (Δd <0), the reflected light is incident on the objective lens L0 while being slightly diverged as compared with the parallel light as indicated by a dotted line. For this reason, when the light is subsequently focused by the eyepiece lens L1, it is not focused on the focal plane of the lens when Δd = 0 (the distance from the eyepiece lens L1 to f1), but is focused at a slightly distant position.

  Accordingly, at this time, the light is condensed in the pinhole A1 for the photodiode PD1 to be smaller than the original beam cross section. Here, since the beam cross section is adjusted to be larger than the pinhole A1 when Δd = 0, more light is emitted from the photodiode PD1 when Δd = 0 when the beam cross section is reduced in this way. Is incident on. Therefore, the light intensity S1 received by the photodiode PD1 when Δd <0 increases from the original intensity when Δd = 0. On the other hand, in the pinhole A2 on the photodiode PD2 side, the beam light diverges larger than the original beam cross section (Δd = 0), so that a considerable beam is shielded by the pinhole A2. For this reason, the light intensity S2 incident on the photodiode PD2 is smaller than when Δd = 0.

  Here, since a normal photodiode (light receiving element) has a light receiving area of an appropriate size, even if there is a change in the beam cross-sectional shape due to a change in the beam focal position as described above, the beam is eventually changed. All light is received. For this reason, when light is incident on the photodiode without passing through the pinhole, even if the beam focal position changes as described above, the amount of light received by the photodiode does not change.

  Therefore, if the pinholes A1 and A2 are provided as in the present embodiment, the beam light is blocked by the pinholes according to the change in the beam cross-sectional area, and the received light intensity changes greatly. By arranging the pinholes A1 and A2 in this way, a minute change in the cross-sectional area of the beam caused by the upper and lower sides of the measurement surface can be detected with high sensitivity. The pinholes A1 and A2 may have a diameter of about several hundred μm, for example. Further, as in the present embodiment, if pinholes A1 and A2 are respectively arranged before and after the focal plane so that changes in light intensity in the photodiodes PD1 and PD2 are opposite to each other, they will be described later. Thus, the measurement accuracy can be improved by using the difference signal of the signal obtained from the light intensity.

  Also, as shown in FIG. 3C, when the measurement surface is moved downward (Δd> 0), a state opposite to that in FIG. 3B occurs, and the light intensity in the photodiode PD1 is The light intensity in the photodiode PD2 increases and decreases. Note that, when the wear of the surface of the measurement surface is observed as in this embodiment, this corresponds to the case where the measurement surface moves downward.

  As described above with reference to FIGS. 3A to 3C, the relationship between the amount of received light and the amount of movement of the measurement surface is shown in FIG. A calibration curve as shown in (b) is obtained in the personal computer 3 as the calibration curve D2. If the data of the calibration curve D2 is stored in advance, the measurement surface movement amount can be obtained according to the amount of received light. Therefore, by moving the measurement position on the measurement surface, the surface unevenness can be measured, and the measurement surface position D1 as shown in FIG.

Here, with respect to the calibration curve shown in FIG. 4A described above, the normalized light quantity difference S when the light intensity signals in the photodiodes PD1 and PD2 are S1 and S2, that is, S = (S1-S2). / (S1 + S2) (1),
FIG. 5 (a) shows a calibration curve estimated to be obtained when using. In the present embodiment, this light amount difference S is used for quantitative measurement of the wear amount. Thus, the vertical movement of the measurement surface can be easily measured using the difference signal (light quantity difference S) between the light intensity signals S1 and S2 in the two photodiodes PD1 and PD2. Note that FIG. 5B shows a further enlarged view of the dotted line region Q shown in FIG. Due to the noise component of the entire system, the instantaneous output has a small finite width SN as shown in FIG. As the cause of the finite width SN, both the miscellaneous light component SNL and the electronic circuit noise component SNE of the A / D converter 7 and the amplifier 6 can be considered.

  Here, even if only one of the photodiodes (PD1 or PD2) is used, a piecewise linear relationship between the measurement surface movement amount Δd and the output (S1 or S2) is obtained. I can. That is, as Δd increases, S1 increases approximately linearly, and conversely, S2 decreases approximately linearly. However, as will be described below, it is advantageous in terms of measurement sensitivity to obtain a difference signal between the two using photodiodes (PD1 and PD2). In addition, the influence of extraneous light is reduced, and ultimately high-resolution measurement is possible.

Next, in order to examine the measurement sensitivity and resolution, in Equation (1), the respective changes with respect to the minute Δd are S1 → S10 + ΔS1, S2 → S20 + ΔS2, and S → S0 + ΔS. Here, S10, S20, S0, and the like indicate respective values when the measurement surface is on the focal plane of the lens L0 (Δd = 0). Actually, as described above, ΔS1 and ΔS2 have different signs. Furthermore, since S10 = S20 when setting the optical system, S0 = 0. Furthermore, since it is considered that ΔS1 + ΔS2≈0 in principle, the relationship of the following equation is obtained by substituting these changes into the equation (1).
ΔS = (ΔS1−ΔS2) / (S10 + S20) (2)
Here, the measurement sensitivity K by the measurement apparatus 2 of this embodiment is:
K = ΔS / Δd (3)
Defined by Since ΔS1 and ΔS2 always have different signs regardless of whether Δd is positive or negative, the magnitude of the signal ΔS is twice that of when only one of the signals is used. Since the conventional method is a method that uses only one of the signals S1 or S2, the sensitivity of this method is doubled compared to the conventional method.

Further, as will be described below, the influence on the miscellaneous light is reduced, and the resolution is eventually improved. That is, as described above, the noise component SN of the entire system can be both the miscellaneous light component SNL and the electronic circuit noise component SNE of the A / D converter 7 and the amplifier 6.
SN = SNL + SNE≈SNE (4)
Of these, SNL is the most problematic during optical measurement. In the case of this measurement method, the miscellaneous light is caused by the difference in reflectance on the measurement surface, which is separated into two light beams, so that it is equally incident on both light receiving elements and is not incident on each individual element. . In other words, ΔS1 and ΔS2 in the equation (2) are added in the same manner, and the influence on ΔS is completely eliminated, and only the noise component of the electronic circuit is obtained.

Next, the resolution κ (kappa) indicates the limit to how finely the displacement amount Δd can be measured. As is apparent from FIG. 5B, this is determined by the following equation from the noise component SN and the measurement sensitivity K. That is,
κ = SN / K≈SNE (Δd / ΔS) (5)
Is required. However, SN here is a noise component that is similarly normalized by (S10 + S20) since ΔS is normalized as shown in equation (2). Thus, in this method, the SNE is reduced and ΔS is doubled, so that κ is considerably small. In other words, a high resolution can be obtained.

  In the measurement system 1 described above, before actual measurement, the measurement surface X is first adjusted to an appropriate vertical position so that the light intensities (S1, S2) incident on the photodiodes PD1, PD2 become equal. To. Next, the measurement surface X is moved up and down to obtain the calibration curve D2.

  Finally, the calibration curve D2 is used to quantitatively measure the actual wear surface and cutting surface position, in other words, the wear amount and the cutting amount. In this case, for example, the measurement surface is always moved by placing an object on a turntable or the like. Alternatively, instead of moving the measurement surface, the laser light source may be moved to perform surface inspection of semiconductor elements, mechanical parts, and the like. In this measurement, the light intensity signals S1 and S2 from the photodiodes PD1 and PD2 of the measuring unit 5 are amplified by the amplifier 6 and further A / D converted by the A / D converter 7, and then the personal computer Output to 3. Various calculations are performed by the personal computer 3 to obtain a surface displacement (measurement surface position D1) and the like (amount of wear) from the calibration curve D2.

  Thus, since it is not necessary to move the objective lens L0 during actual measurement, the measurement range of the surface irregularities is not limited by the movement range of the objective lens L0. In the measuring apparatus 2 using a specific example of parameters to be described later, the measurement range within a certain appropriate resolution (κ = 2 μm) can be at least about ± 0.8 mm. Moreover, since the objective lens L0 does not need to be moved, the optical system is relatively simple and inexpensive.

  Next, prior to actual measurement by the above-described measurement system 1 and the observation system 11 described later, a simulation experiment using an example of commercially available optical system design software (Zemax) was performed in order to examine the performance of this measurement method.

  An example of results (output characteristics as a calibration curve) is shown in FIG. This shows the relationship of the standardized light output S with respect to the measurement surface displacement Δd, and the tendency is completely consistent with the expected diagram of FIG.

  The output characteristics include various optical element dimensions (pinhole diameter P, distances between pinholes and light receiving elements a1, a2) and lens characteristics (focal length f0 of objective lens L0, eyepiece L1) as shown in Table 1 below. Of the focal length f1).

In particular, regarding the sensitivity, the influence of the focal length f0 of the objective lens is large, and in the case of Case (a) in Table 1, the maximum sensitivity K = 2.46 mm within the range of −0.25 mm <Δd <0.25 mm. ^-1 is obtained.

  Next, in order to verify this simulation result, an example of a measurement result performed by the measurement system 1 is shown in FIG. This result completely coincides with the simulation result of FIG. 8, and from this, the validity of the simulation experiment was confirmed.

  The optical element dimensions in this case were set as shown in Table 2 below.

In this case, in Case (a) in Table 2, the maximum sensitivity K = 2.41 mm ⁻¹ was obtained within the range of −0.25 mm <Δd <0.25 mm. This value was almost the same as the sensitivity value K = ^2.46 mm ⁻¹ according to the simulation experiment result.

  As a parameter not described in Tables 1 and 2, the focal length f2 of the eyepiece is set to f2 = 50 mm. The half mirrors BS1 and BS2 are both complete semi-transparent mirrors, which are 50% transmitting and 50% reflecting.

The resolution κ of the measurement system 1 is about κ = −0.25 mm <Δd <0.25 mm because the noise component in FIGS. 5A and 5B is SN≈5.0 × 10 ^−3. It was 2 μm. Since the measurement system 1 uses the 12-bit A / D converter 7, the quantization error is about 2.4 × 10 ^−4, which is smaller than the above value and can be ignored.

[Example 1]
Next, an observation system 11 for observing a friction surface used in combination with the above-described measurement system 1 will be described with reference to FIG.

  The measurement system 1 and the observation system 11 described below are systems that quantitatively measure the amount of wear simultaneously with the observation of the wear surface during rotational wear, and should also be called a so-called tribo viewer. This makes it possible to perform quantitative measurement of the amount of wear and simultaneous observation of the worn surface, which has never been possible before, and can provide a new measurement method in the field of tribology. In addition, this testing machine can be a standard wear testing machine that can guarantee reliability and quantitativeness by eliminating the stopping of the testing machine and the removal error of the test piece. As described above, the measurement system 1 is suitable for the purpose of quantitative measurement of the surface unevenness with high sensitivity and in real time, and can also be applied to the wear amount measurement and the simultaneous observation of the wear state.

  As shown in FIG. 6, the observation system 11 includes an eddy current displacement measuring instrument 12, a trigger amplifier 13, a delay circuit 14, a trigger counter 15, a stroboscope 16, a stroboscope 17, a CCD camera 18, a video deck 19, and a TV monitor. 20 and a microphone 21.

  In this observation system 11, the surface unevenness of the measurement surface on the turntable 23 shown in FIG. 7 is photographed by the CCD camera 18, recorded by the video deck 19, and displayed by the TV monitor 20. Real-time observation is possible.

  The eddy current displacement measuring instrument 12 is a device that outputs a signal corresponding to the displacement. In the present embodiment, the eddy current displacement measuring instrument 12 detects the target 22 having a thickness of 5 mm arranged on the side surface of the turntable 23. More specifically, the eddy current displacement measuring instrument 12 is set to a distance within the measurable range defined in the specification of the eddy current displacement measuring instrument 12 only when the target 22 approaches the sensor head portion. The position of the sensor head is set. The eddy current displacement measuring instrument 12 outputs a mere constant voltage because it is outside the measurement range when the target 22 is not approaching.

  When the eddy current displacement measuring instrument 12 detects the target 22 in accordance with the rotational movement of the turntable 23, it changes the output signal. In response to the change in the output signal, the trigger amplifier 13 generates a trigger signal and inputs the trigger signal to the strobe 17 via the delay circuit 14, the trigger counter 15, and the stroboscope 16. The strobe 17 emits a micro flash and works with the CCD camera 18 to capture a still image of the friction surface.

  More specifically, in order to photograph (capture) the same friction surface with the CCD camera 18, a rectangular signal is generated by the eddy current displacement measuring instrument 12 having a response frequency of 15 kHz, and this is used as a trigger signal for photographing. Thereby, even if the rotation unevenness by the fluctuation | variation of a frictional force or the slight malfunction of a bearing arises, the same location can be observed every time.

  Note that the time from when the trigger signal is input to when the microflash emits light is about 5 μs, and the light emission time is about 4 μs, which is very short relative to the moving speed of the friction surface. For this reason, it is possible to acquire a still image. Since the still image is held until the next trigger signal is input, by recording it using video, the change of the friction surface at the same point for each slip can be changed smoothly as an animation. Can be observed.

  Further, the delay circuit 14 incorporated between the eddy current type displacement measuring instrument 12 and the stroboscope 16 delays the trigger signal, so that any place in the wear can be observed. In this case, a delay time can be set every 1 μs from 0 to 1 sec, and the signal transmission delay time is as short as 0.5 μs.

  As described above, real-time observation of the surface can be performed. The greatest feature of this method is that high-speed measurement, that is, real-time measurement is possible. Since this method measures the amount of change of the measurement surface from the light intensity of the photodiodes PD1 and PD2 as described above, the time required for measurement at a position on a certain measurement surface is determined only by the time for reading the intensity change. . The response of a normal silicon photodiode is extremely fast (less than μs). Therefore, the measurement time is determined only by the processing time including the amplifier 6 and the A / D converter 7. Since the time required for the intermediate processing is also about several μs to several tens of μs, it can be estimated that the measurement time is finally about several tens of μs. This corresponds to a measurement frequency of about several tens of kHz. Accordingly, if such a high-frequency oscillation pulse laser is used as continuous light or a light source, the frequency can be measured in real time.

  On the other hand, the “displacement measurement system by focusing method” described in Non-Patent Document 1 of the conventional method measures the amount while focusing on each measurement point (and therefore the surface), and has a high resolution (1 μm). ), However, requires time for alignment and is completely lacking in real time.

  As described above, the present invention relates to a method for measuring a wear amount and a cutting amount in real time, a device therefor, and a state observation device (tribo viewer) thereof. As described in the above-described embodiment, the system of the present embodiment (the present system) is an optical system that measures the wear amount and the cutting amount with high resolution in real time. The optical system to be called the heart of this system is a relatively simple system comprising a laser light source, two semi-transparent mirrors (beam splitters), two lenses, two light receiving elements such as silicon photodiodes, and two pinholes. . The measurement principle is that the reflected light from the measurement surface is divided into two light beams, and the light intensity of both is used to improve the sensitivity, S / N, and ultimately the resolution over the conventional method. The features of this system are real-time characteristics (measurement frequency: several tens of kHz) and high resolution (measurement resolution: 2 μm).

  On the other hand, a method for directly measuring the amount of surface wear and the amount of cutting with high resolution and in real time has not been known. For this reason, conventionally, the method of temporarily stopping the operation of the apparatus and measuring the surface offline has been adopted. On the other hand, the inventors of the present application (Honda et al.) Prototyped an apparatus that observes the wear state of the wear surface in real time by stroboscopic observation of the wear phenomenon during rotation in synchronization with the rotation. However, this was an observation of the state of the worn surface, and it was impossible to quantitatively measure the amount of wear.

[Embodiment 2]
Another embodiment of the present invention will be described with reference to FIGS.

  The triboviewer according to this embodiment includes a measurement system and an observation system. The measurement system of this embodiment has a configuration in which the measurement accuracy for a rough surface under friction is increased. The measurement system includes a friction force sensor and an acceleration sensor, and is configured to be able to measure further information related to friction in real time. In the following description, the same members as those in the first embodiment are denoted by the same reference numerals for the sake of simplicity, and description thereof is omitted.

  As shown in FIG. 10, the measurement system 1A of the present embodiment includes a pinhole (aperture, third light shielding member, averaging means) A3 in the measurement unit 5A in addition to the configuration of the measurement system 1 of the first embodiment. This is a configuration provided. With this configuration, as will be described later, even if the measurement surface is a rough surface in a friction state, it is possible to perform measurement with increased accuracy by reducing errors.

  The measurement system 11A further includes a frictional force sensor 30, an acceleration sensor 31, a dynamic strain meter 32, and a charge amplifier 33. More detailed information on the friction is measured in real time by these sensors.

  As shown in FIG. 11, the measurement system 1 </ b> A has a pinhole A <b> 3 in the middle of the optical path that reaches the distributor where the reflected light from the measurement surface (illuminated surface) X is distributed to the light receiving element (detector). It is the arranged configuration. The reflected light is guided to each light receiving element after passing through one pinhole A3. By arranging in this way, even when the wear surface is measured, the accuracy can be improved as follows.

  Here, first, the reason why an error may occur in the measurement of the worn surface will be described. When the irradiated surface of the object is a completely rough surface (a surface that is completely rough with respect to the wavelength of light), the intensity of the reflected light that is reflected by this irradiated surface and travels toward the objective lens is Or when a certain surface is irradiated, its intensity distribution becomes substantially uniform (constant). For this reason, as described in the first embodiment, sufficient accuracy can be obtained.

  On the other hand, when the irradiated surface of the object is a rough surface under friction, the irradiated surface has finer and irregular irregularities. That is, the object surface partially includes, for example, a reflective surface area that is perpendicular or inclined to the optical axis. The light reflected from such a surface to be irradiated may deviate from the isotropic intensity distribution on a complete rough surface, for example, as shown in FIG. 12 as a reflected light intensity distribution. Here, FIG. 12 shows an example of the intensity of the reflected light in a cross section perpendicular to the traveling direction of the reflected light, or the intensity when the reflected light is applied to a certain surface. For example, in the case of precision machining or hard metal surface wear with little wear, the reflection intensity deviates from such an isotropic intensity distribution in many cases. As for the material whose wear is to be measured as in the present embodiment, there are many materials that cause this kind of wear surface. This causes variations in intensity distribution across the beam cross section.

  When the reflection intensity from the irradiated surface X is not isotropic and not uniform, for example, the intensity distribution in the beam cross section is not constant at the position of the objective lens L0 shown in FIG. In this case, the intensity distribution is locally uneven with respect to the radial distance from the optical axis and the angle around the optical axis. For example, as shown in FIG. 12, the light intensity distribution is a function of the radius R from the beam optical axis. At this time, as described below, the signal intensity detected by the light receiving element, that is, the normalized signal intensity S may vary. In this case, it becomes difficult to measure with high accuracy, resulting in poor resolution.

  Further, when measurement is performed using laser light, in addition to the above-described variation in intensity distribution over the entire beam cross section, local intensity distribution variation due to speckles peculiar to the laser light occurs. This variation occurs very locally. For this reason, for example, when a portion of the light flux including variations in the laser beam is directed to the pinholes A1 and A2 via the same region on the half mirror BS2 shown in FIG. Even if it should be detected as the signal intensity through A2, it is difficult to actually pass both of the pinholes A1 and A2. For this reason, the error described below occurs.

  First, the reason why an error occurs due to the non-uniformity as described above will be described. For example, even if there is no pinhole A3, no error occurs if the intensity distribution of the reflected light incident on the surface of the pinhole A3 is constant. In this case, the pinholes A1 and A2 disposed in the optical path that passes through the position of the pinhole A3 and reaches both light receiving elements may be disposed at a position slightly deviated from the optical axis, for example. Strictly speaking, it is only necessary that the holes of the pinholes A1 and A2 are arranged in the cross section of the region where the laser beam is a beam.

  However, due to the non-uniformity as described above, when the beam intensity is not constant (uniform), the pinholes A1 and A2 on the front surfaces of both light receiving elements must be accurately aligned on the optical axis. Don't be. Here, for example, even if the intensity distribution is as shown in FIG. 12, since the same distribution light is distributed by the half mirror (semi-transmission mirror), the light of the same distribution is originally incident on both light receiving elements. Should do. That is, in practice, the same distribution is realized only when both pinholes A1 and A2 are accurately aligned on the optical axis, and the same result as in the case where the intensity distribution is constant can be obtained.

  That is, when the radius of the pinholes A1 and A2 is p and the radius of the cross section of the laser beam is RB, light having a radius in the range of −p to p shown in FIG. 12 enters the light receiving element. At this time, if both the pinholes A1 and A2 are not accurately aligned on the optical axis, the light incident on each light receiving element is different for each light receiving element. That is, when the position of the pinhole A1 or A2 is deviated from the optical axis by, for example, x, the pinhole is deviated by x from the optical axis corresponding to the origin of R = 0 in FIG. Is detected by the light receiving element through the pinhole. Since the magnitude and direction of such deviation differs for each pinhole, for example, a strong (weak) light intensity is detected in the light receiving element via one of the pinholes A1 and A2, and a weak (strong) light is detected in the other. Intensity may be detected.

  As described above, when the beam intensity is not uniform, for example, the positional deviation of the pinhole A1 or A2 causes an error in the signal intensity, which causes a variation in the signal intensity of the light receiving element.

  Therefore, in the measurement apparatus 1A of the present embodiment, as shown in FIG. 11, the measurement unit 5A further includes a pinhole A3. The pinhole A3 is disposed on the object side of the eyepiece lens L1, that is, on the optical path from the irradiated surface to the eyepiece lens L1 disposed in front of the half mirror BS2 as a light distributor.

  The radius of this pinhole A3 is RA. This pinhole A3 functions as a light shielding member that limits the laser beam radius of the reflected light, for example, in the range from −RB to RB shown in FIG. 12 to the range from −RA to RA. Here, 0 <RA <RB. According to the thus improved optical system (measurement unit 5A), only the intensity distribution light of the radius RA portion can be used with respect to the radius RB when there is no pinhole A3.

  Thus, using the pinhole A3, only a part of the beam with non-uniform intensity is extracted and led to the pinholes A1 and A2 arranged in front of the light receiving element. As a result, at the positions of the pinholes A1 and A2, variations in the intensity of light applied to the surfaces of the pinholes A1 and A2 can be reduced. For example, as shown in FIG. 12, in the case of a light beam whose intensity decreases as the radius increases, variation in intensity distribution can be limited within a predetermined range by appropriately selecting the radius RB of the pinhole A3. That is, the pinhole A3 functions as an averaging unit that reduces non-uniformity on the irradiated surface when irradiated with reflected light. For example, the size of the pinhole A3 should be reduced to such an extent that the light receiving element has sensitivity.

  As described above, by inserting the pinhole (aperture) A3, it is possible to reduce the measurement error, improve the measurement accuracy, and increase the resolution.

  Next, the error in the measurement system 1A described above is estimated, and it is confirmed that the error is actually reduced by the above-described configuration.

  First, in order to increase the resolution κ of the optical system of the measurement system 1A (decrease the resolution κ), as can be seen from the above equation (5), the measurement sensitivity K is increased or the noise component SN is decreased. There must be. The noise component is determined by the optical system and data processing system of the measurement system, and is inherently a problem different from sensitivity. Here, the sensitivity of this optical system is examined.

  The measurement sensitivity K is defined as a ratio ΔS / Δd of ΔS with respect to Δd, as in the above-described equation (3). For this reason, in order to increase the measurement sensitivity K, it may be considered to produce a signal intensity change ΔS as large as possible with respect to a minute change in d.

  Here, for the sake of simplicity, a part of the optical system of the measurement unit 5 shown in FIG. 2 in which the pinhole A3 is omitted is shown as an equivalent optical system in FIG. As shown in FIG. 13, the measurement point F0 is imaged by an objective lens L0 having a focal length f0. Further, the image point is newly considered as an object point of the eyepiece lens L1, and an image is formed again at the focal point F1 of the lens L1. In this case, the object distance of the lens L1 is −b0.

  In this configuration, the minute movement of the imaging point F1 from f1 to f1 + Δf1 with respect to the minute movement Δf0 of the object point F0 from f0 to f0 + Δf0 (Δf0 <0 in the illustrated case) is due to geometric optics. From the approximation, it is obtained as follows. The minute movement Δf0 is set to Δd in FIGS. 3 (a) to 3 (c).

First, from the imaging formula by the lens L0, the imaging distance b0 by this lens is
1 / (f0 + Δf0) + 1 / b0 = 1 / f0 (6)
Using Δf0 / f0 << 1 for
b0≈ (f0) ² / Δf0 (7)
Can be approximated.

Since this image point is formed again in the vicinity of the focal point F1 (f1 + Δf1) by the lens L1, the image formula by the lens L1 (in this case, the object distance of the lens L1 is −b0)
1 / (− b0) + 1 / (f1 + Δf1) = 1 / f1 (8)
And using Δf1 / f1 << 1,
b0 = − (f1) ² / Δf1,
Or
Δf1 = − (f1) ² / b0 (9)
Get.

Furthermore, substituting equation (7),
Δf1 = − (f1 / f0) ² Δf0 (10)
Get. The negative sign in this equation indicates that the increase / decrease relationship between Δf1 and Δf0 is opposite to the optical axis direction (Z-axis direction).

Next, consider a minute angle change Δθ0 (Δθ0> 0 in the case of illustration) corresponding to Δf0 caused by surface irregularities, for example. From simple geometry,
△ f0 sinθ0 ≒ ((f0) ² + (h0) ² ) ^1/2 (-△ θ0) (11)
Get. Here, if the relationship of sinθ0 = h0 / ((f0) ² + (h0) ² ) ^1/2 is used,
Δθ0 = − {h0 / ((f0) ² + (h0) ² )} Δf0 (12)
Get a relationship. Here, h0 is the aperture radius of the lens L0. The minus sign in this equation indicates that Δf0 and Δθ0 increase or decrease in the opposite direction.

Similarly, on the eyepiece L1 side,
−Δθ1 = {h1 / ((f1) ² + (h1) ² )} Δf1 (13)
It becomes. The negative sign in this equation indicates that the increase / decrease relationship between Δf1 and Δθ1 is in the opposite direction. H1 is the aperture radius of the lens L1.

Here, when the relationship of the equation (10) is used for the equation (13), the relationship of the following equation is obtained.
Δθ1 = h1 Δf0 / [(f0) ² {1+ (h1 / f1) ² }] (14)
Here, since normally (h1 / f1) ² << 1,
Δθ1 = (h1 / (f0) ² ) Δf0 (15)
It becomes.

  Next, the case where the reflected light is applied to the pinhole A1 or A2 after passing through the configuration shown in FIG. 11 will be described with reference to FIG. 14 as an equivalent optical system. The pinhole A4 shown in FIG. 14 corresponds to the pinhole A1 or A2. A description will be given of a change in the amount of light beam transmitted through the pinhole A4 in accordance with the change in the cross section of the laser beam cross section on the pinhole surface when the pinhole A4 is placed in front of the focal point. Note that the change in the laser beam is in accordance with the change in Δθ1 due to Δf0. In addition, here, for the sake of simplicity, the light intensity per unit cross-sectional area on the pinhole A4 surface is assumed to be constant.

First, let the radius of the pinhole A4 be p and the diameter be P. In addition, the beam radius on the pinhole surface of the laser beam focused on the focal point is r1. If the total amount of light transmitted through the eyepiece L1 is IT and the amount of light transmitted through the pinhole is IP,
IP = (p / r1) ² IT (16)
Get.

  Here, it is assumed that the position of the pinhole A4 is moved by q in the z-axis direction from the focal point F1. Here, if r1 is changed by Δr1 due to Δf1, r1 and Δr1 are obtained as follows from simple geometry with respect to FIG.

First, since r1 = (q / f1) h1,
r1 ten Δr1 = (q ten Δf1) h1 / (f1 ten Δf1)
= R1 (10 Δf1 / q) / (1 + Δf1 / f1)
≒ r1 (1 + △ f1 / q)
ΔΔr1 = h1 Δf1 / f1 (17)
It becomes. Note that the approximation here uses q << f1, which is a normal condition in the present optical system. Therefore, Δr1 is given by the following equation from equation (10).
Δr1 = − (hl f1 / (f0) ² ) Δf0 (18)
Further, when the pinhole is placed before and after the focal point, the amount of change in the amount of light from the IP due to Δr1 is assumed to be ΔIP2 and ΔIP1. At this time, first about IP2,
IP2 = IP + ΔIP2
= {P / (r1 + Δr1)} ² IT
= (P / r1) ² IT (1 + Δr1 / r1) ^-2
≈ IP (1-2Δr1 / r1)
Is obtained. Therefore,
ΔIP2 = −2 (Δr1 / r1) IP (19)
It becomes. If the equation (18) is used for the equation (19), the following equation is obtained.
ΔIP2 = 2 (f1 / f0) ² Δf0 IP / q (20)
Similarly, ΔIP1 when the pinhole is placed behind the focal plane by the same amount q (+ z-axis direction) is set as IP1 = IP + ΔIP1,
ΔIP1 = −2 (f1 / f0) ² Δf0 IP / q (21)
It becomes. Therefore, the standardized signal S according to the above equation (1) is obtained by the following equation using the equations (20) and (21). That is,
S = (S1-S2) / (S1 + S2)
= {-(IP + ΔIP1) + (IP + ΔIP2)} / {(IP + ΔIP1) + (IP + ΔIP2)}
= (-ΔIP1 + ΔIP2) / 2IP
= -2 (f1 / f0) ² (1 / q) Δf0 (22)
Thus, the normalized output S is directly proportional to Δf0, and the slope at that time (ie, sensitivity K) is
K = -2 (f1 / f0) ² (1 / q) (23)
It becomes. Sensitivity K is inversely proportional to q and proportional to (f1 / f0) ² . As described above, there is no room for improvement in the sensitivity once the optical system is determined.

  Next, as shown below, various verification experiments etc. were performed about (23), and the tendency was examined.

  Examples of the results of verifying the above theoretical examination by preliminary experiments are shown in FIGS. 17 is f1 = 70 mm and q = 3 mm, FIG. 18 is f1 = 70 mm and q = 6 mm, FIG. 19 is f1 = 50 mm and q = 3 mm, and FIG. 20 is f1 = 50 mm and q = 6 mm. Each case is shown. The points in the figure indicate the direction in which Δf0 is displaced in the ± direction in the experiment.

  The sensitivity according to the theoretical equation (23) for various values of f1 = 50 mm or 70 mm, q = 3 mm or 6 mm with f0 = 15 mm fixed is K (f1 = 70, q = 3) = − 14, respectively. .5, K (f1 = 70, q = 6) = − 7.3, K (f1 = 50, q = 3) = − 7.4, K (f1 = 50, q = 6) = − 3.7 The experimental sensitivities are -2.05, -1.46, -1.33, and -0.988, respectively, but the trends for f1 and q are completely consistent. Yes. The experimental sensitivity is considerably small because the assumption that “the light intensity at the pinhole surface is constant” is used in the derivation of equation (23), but this seems not to be true in the experiment. . The reason for this is thought to be that the irradiated surface is not perpendicular to the optical axis, the reflected light has directionality, and speckles peculiar to laser light.

  In addition, about the evaluation of an error, it demonstrates supplementarily about the resolution when a shift | offset | difference arises for every pinhole. The errors of the signal intensity IP1 and IP2 of both light receiving elements caused by the non-uniform distribution of the intensity of the reflected light and the pinhole A1 or A2 deviating from the optical axis are assumed to be εp1 and εp2, and the resulting error of the normalized signal S ( (Maximum error) is εs.

At this time,
S + εs
= {(IP1-IP2) + (| εp1 | + | εp2 |)} /
{(IP1 + IP2) + (| εp1 | + | εp2 |)}
≒ S {1+ (| εp1 | + | εp2 |) / (IP1-IP2)} ×
{1- (| εp1 | + | εp2 |) / (IP1 + IP2)}
≒ S {1- (| εp1 | + | εp2 |) / (IP1 + IP2) +
(| Εp1 | + | εp2 |) / (IP1-IP2)} (24)
It is.

Here, from (19) and (21), (| εp1 | + | εp2 |) / (IP1 + IP2) << (| εp1 | + | εp2 |) / (IP1-IP2) holds.
S + εs≈S {1+ (| εp1 | + | εp2 |) / (IP1-IP2)}
= S {1+ (| εp1 | + | εp2 |) / (ΔIP1-ΔIP2)}
(25)
It becomes. By substituting equations (20) and (21), the following relationship is obtained.
εs / S
= − (| Εp1 | + | εp2 |) / {4 (f1 / f0) ² IPΔf0 / q}
=-(1/4) {(| εp1 | + | εp2 |) / IP} (f0 / f1) ² (q / Δf0)
(26)
Thus, even if the error rate (| εp1 | + | εp2 |) / S is small, the pure signal component (ΔIP1-ΔIP2) = − {4 (f1 / f0) ² IPΔf0 / q} of both signals is In particular, it becomes smaller when Δf0 is near zero. For this reason, the error rate εs / S increases and the resolution deteriorates.

The resolution κ is given by the above equation (5). Therefore, if SN = εp1 + εp2 is substituted into equation (5),
κ = (εp1 + εp2) / K (27)
And is directly proportional to the error. Further, the error due to each pinhole contributes as a sum to the resolution κ of the entire system. Thus, in order to reduce κ, the error must be reduced. Here, as described above, the measurement system 1A of the present embodiment can reduce this error by adding the pinhole A3.

  Next, further characteristic points of the measurement system 1A will be described. As shown in FIG. 10, the measurement system 1 </ b> A includes a friction force sensor 30, an acceleration sensor 31, a dynamic strain meter 32, and a charge amplifier 33. FIG. 15 shows a configuration when this measurement system 1A is combined with the observation system described in the first embodiment.

  Data from the frictional force sensor 30 and the acceleration sensor 31 are output to the external personal computer 3 via the dynamic strain gauge 32 and the charge amplifier 33, respectively. In the personal computer 3, these data are stored in a storage unit (not shown) by a control unit (not shown) for each rotation of the turntable 23. The control unit of the personal computer 3 uses the data in the storage unit to extract the time change at the same location, for example, due to repeated friction by the turntable 23. The control unit of the personal computer 3 exhibits the above-described functions by reading and executing a program recorded in a recording medium such as a storage unit.

  The friction force sensor 30 is for measuring a friction force closely related to the wear behavior. The frictional force is indispensable information in the evaluation of tribological characteristics. The friction force sensor 30 of this embodiment is a strain gauge type friction force sensor.

More specifically, the strain gauge type friction force sensor as the friction force sensor 30 includes a leaf spring having four strain gauges attached thereto. When the strain is generated in the leaf spring by the frictional force, the strain is transmitted to the resistor (wire / foil) through the base of the strain gauge, and a resistance change corresponding to the generated strain is generated. Since the resistance change of the strain gauge is very small, it is converted into voltage using a Wheatstone bridge circuit as shown in FIG. When the strain gauge is connected to the dynamic strain measuring device, a Wheatstone bridge circuit is configured, and the input voltage of the bridge circuit is supplied from the dynamic strain measuring device, so that the strain amount can be measured as the output voltage. Before the experiment, the friction force can be known from the measured strain by obtaining the relationship between the strain and the force as a calibration curve in advance. The output voltage e of the Wheatstone bridge circuit is, for example, in the configuration shown in FIG. 16, where the resistance value of the strain gauge is R1, the values of other fixed resistors of the Wheatstone bridge circuit are R2 to R4, and the input voltage is E. ,
e = (R1 R3-R2 R4) E / {(R1 + R2) (R3 + R4)}
Given in.

  Here, for example, with respect to the frictional force closely related to the wear behavior, conventionally, an average frictional force per certain number of frictional repetitions has been measured. In this case, it was difficult to use this information for detailed analysis of the friction surface.

  On the other hand, according to the measurement system 1A configured as described above, even a change in friction force during one rotation of the disk test piece can be captured at a response frequency of 2.5 kHz, for example. Also, these data can be stored separately for each rotation from a predetermined starting point. As a result, it is possible to capture the time change of the same location with repeated friction.

  A trigger signal for strobe emission is input to the personal computer 3 from the trigger amplifier 13 of the observation system (observation system) 11 shown in FIG. The friction force and acceleration data input to the personal computer 3 by this trigger signal can be stored separately for each rotation of the disk specimen from a predetermined start point. The frictional force sensor outputs data to the dynamic strain meter 32, and the dynamic strain meter 32 amplifies the data and outputs it to the personal computer 3.

  The acceleration sensor 31 is for examining the constituent component of the frictional force. The acceleration sensor 31 of the present embodiment is a type of acceleration transducer that self-generates electric charges, and generates electric charges proportional to the applied acceleration, so that the acceleration value can be measured from the amount of electric charges. The charge amplifier 33 is used to convert and amplify the electric charge output from the acceleration sensor 31 into a voltage signal that can be easily processed.

  Here, the change in the frictional force measured by the above-described frictional force sensor 30 is a force necessary for sliding the two objects in the opposite directions. It also includes the power necessary to destroy. As described above, with the conventional measuring method, only an average frictional force per certain number of friction repetitions can be known. Moreover, it was not possible to investigate the constituent components of the frictional force and how it is related to the friction surface.

  Therefore, the acceleration sensor 31 is also used. The acceleration sensor 31 has a response frequency of 1 kHz. The acceleration sensor 31 is a biaxial acceleration sensor in the vertical direction and the horizontal direction. By using this acceleration sensor 31, each direction component output is obtained, and it is known in more detail whether the dominant factor of the frictional force is a large unevenness of the contact surface or a shear fracture of the material at the contact point. Can do.

  Moreover, since the change of the measurement surface can be obtained by the measuring apparatus 1A, it is possible to investigate how the frictional force and the friction surface are related.

  In the above-described embodiment, an example in which the pinhole A3 is disposed on the object side of the lens L1 in FIG. 11 is shown, but the present invention is not limited to this. For example, the pinhole A3 may be disposed between the lens L1 and the half mirror BS2. However, when the pinhole A3 is disposed between the lens L1 and the half mirror BS2, even if the pinhole A3 having the same diameter is used, the effect (removal) depends on the position of the placement and the focal length of the lens L1. Light) may be different.

  As described above, the measurement system 1A includes the friction force sensor 30 and the acceleration sensor 31, and can measure the friction force, the components of the friction force, and the relationship between the friction force and the friction surface. More specifically, during one rotation of the disk test piece on the turntable 23, the frictional force, vertical / horizontal acceleration, and changes in the friction surface can be simultaneously captured. Further, the measurement system 1 </ b> A outputs the measured data to the personal computer 3. Thereby, the data observed by the measurement system 1A can be stored separately for each rotation from the predetermined start point. By combining the measurement system 1A with the observation system 11, it is possible to observe and elucidate detailed tribological phenomena in real time. In this way, comprehensive tribological phenomena could be observed with the improved trib viewer.

  Here, the tribo-viewer composed of the measurement system 1 and the observation system 11 described in the first embodiment is developed with a focus on observing the transition process of the wear surface that changes every moment during the friction test in real time. It is a thing. Therefore, in the present embodiment, the idea is further advanced, and as shown in FIG. 15, the strain gauge type friction force sensor 30 and the acceleration sensor 31 are incorporated into the triboviewer so as to obtain multi-dimensional information. It is.

  In addition, the measurement system 1A in the present embodiment further reduces the measurement error by performing an averaging process as follows.

  Here, as in the measurement system 1A, when the wear phenomenon is a measurement object, there is a problem that a measurement error below to some extent cannot be avoided. Therefore, as another method for reducing the error, a method using averaging (n-time averaging) of a large number of data at a place where the irradiation position is slightly shifted can be considered.

Here, when the data includes random noise SN, if the measurement is performed n times and averaged, the influence of the noise due to the random noise becomes about SN / (n) ^1/2 . For this reason, the measurement error can be greatly reduced by averaging. When the wear surface is targeted, it is considered that the noise includes random noise SN, thereby reducing the measurement error.

As described above, the measurement system 1A / observation system 11 can perform high-speed measurement with a sampling frequency of about 10 kHz. Therefore, the measurement system 1A averages the data input by sampling every 25 data in the personal computer 3 to which data is input, and obtains new data. The data obtained in this way has an influence component of noise of about SN / 5 due to an average of 25 data. Since the measurement frequency at this time is the 10 ^4/25 = 400Hz, it is possible to measure for example 60Hz measurement of rotating body (3600 rpm) for each angle within 1 degree.

  As described above, the measurement system 1A improves measurement accuracy, reduces errors, and improves resolution by inserting a pinhole (opening) A3 or averaging data.

  Note that Patent Documents 1 and 2 described as the background art disclose a three-dimensional shape measuring apparatus for the purpose of examining the fundus of humans. This configuration is similar to the configuration described in the first embodiment of the present application. Here, it is considered that the human fundus is an almost perfect rough surface as an irradiated surface. For this reason, when such an object is used as the irradiated surface, it is expected that the measurement can be performed by the configuration described in the above publication.

  On the other hand, the object of the invention is completely different between the above-described background art and the present application. In the background art, the case where the irradiated surface is an incomplete rough surface is not taken into consideration. For this reason, when the wear state is observed with the configuration described in the above publication, the irradiated surface is an incomplete rough surface, and sufficient measurement accuracy cannot be obtained. In this way, a relatively large error occurs in the data, and it is expected that the initial resolution of several μm (measurement resolution: minimum measurable displacement) cannot be obtained.

  Therefore, as described above, an improved tribo viewer with an improved optical system that can obtain the same measurement resolution for wear measurement has been proposed.

  In addition, the conventional measurement method can only know the average friction force per certain number of friction repetitions, and it is possible to investigate the components of the friction force and how it is related to the friction surface. There wasn't.

  Therefore, as described above, the measurement system 1A that can measure the constituent components of the frictional force and how it relates to the friction surface has been proposed.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the embodiments can be obtained by appropriately combining technical means disclosed in the embodiments. The form is also included in the technical scope of the present invention.

  The specific embodiments or examples described above are merely to clarify the technical contents of the present invention, and the present invention is not limited to such specific examples and should not be interpreted in a narrow sense. Various modifications can be made within the scope of the claims, and the modified embodiments are also included in the technical scope of the present invention.

  The measurement apparatus according to the present invention not only detects the displacement of the surface of the object to be measured, but also highly sensitively detects the surface irregularities of the object by scanning at least one of the object and laser light, for example. And it can be measured in real time. For example, by scanning a laser beam or a measurement object, it is possible to measure the surface unevenness state of a semiconductor element, a machine part, or the like in real time.

  Moreover, since the unevenness | corrugation of the surface to wear can be detected as a surface unevenness | corrugation detection, it can be used for the real-time measuring method of wear amount and cutting amount. In addition, by combining with an observation device that observes a worn surface with a camera, quantitative measurement of the amount of wear and simultaneous observation of the wear surface are possible, which can be applied to a wear state observation device (tribo viewer). In addition, it is possible to provide a standard wear tester that can guarantee reliability and quantitativeness by eliminating the stoppage of the tester and the error of attaching / detaching the test piece. As described above, the present invention can be applied to the machine industry field to provide a method and apparatus for measuring the amount of wear and the amount of cutting with high resolution and in real time during operation.

  For example, if this measuring apparatus is used, a minute cutting amount can be measured online, and the value can be directly fed back to the next machining amount. For this reason, the precision processing which eliminated the error by the thermal expansion of a processing machine or a workpiece becomes possible. Therefore, it is not necessary to stop the machine for dimension measurement, and the processing time can be shortened and the cost can be reduced. In addition, it is conceivable to predict the replacement timing of the rotating shaft, rotating bearing, brake disc, etc. by detecting wear. In this case, not only the economic effect of making excessive replacement unnecessary, but also inadvertently. It is also possible to prevent accidents.

It is a block diagram which shows an example of the measurement system which concerns on this invention. It is a schematic sectional drawing which shows a part of measuring device contained in the said measuring system. (A) is a schematic cross-sectional view showing a part of the measurement apparatus, (b) is a schematic cross-sectional view of the part in a state different from (a), (c) is (a) and It is a schematic sectional drawing of the said part in the state different from (b). (A) is a graph which shows an example of the data of the measurement surface position obtained by the said measurement system, (b) is a graph which shows an example of the data of the calibration curve obtained by the said measurement system. (A) is a graph which shows the relationship between the movement of a measurement surface and a light quantity change estimated to be obtained by the said measurement system, (b) is a graph which expands and shows a part of (a). It is a schematic block diagram which shows the observation system used in combination with the said measurement system. It is a schematic perspective view which shows a part of said measurement system and the said observation system. It is a graph which shows an example of the calibration curve which linked | related the movement of the measurement surface, and the light quantity change obtained by the simulation experiment about the said measurement system. It is a graph which shows an example of the calibration curve which actually obtained by the said measurement system and related the movement of a measurement surface, and the light quantity change. It is a block diagram which shows the outline of an example of the measurement system which concerns on other embodiment of this invention. It is a schematic sectional drawing which shows a part of measuring device contained in the said measuring system. It is a schematic diagram which shows intensity distribution at the time of irradiating a laser beam in the said measuring apparatus. It is a schematic sectional drawing which shows another part of the said measuring apparatus. It is general | schematic sectional drawing which shows another part of the said measuring apparatus. It is a schematic perspective view which shows a part of said measurement system and an example of an observation system. It is a schematic circuit diagram which shows another part of the said measurement system. It is a graph which shows an example of the measurement result by the said measurement system. It is a graph which shows another example of the measurement result by the said measurement system. It is a graph which shows another example of the measurement result by the said measurement system. It is a graph which shows another example of the measurement result by the said measurement system.

Explanation of symbols

1, 1A measurement system 2, 2A measurement device 3 PC (calculation device)
5, 5A Measuring unit 8 Laser 9 Light receiving unit 10 Optical member 11 Observation system (observation system)
30 Friction Force Sensor 31 Acceleration Sensor 32 Dynamic Strain Meter 33 Charge Amplifier A1 Pinhole (first light shielding member)
A2 Pinhole (second light shielding member)
A3 pinhole (third light shielding member, averaging means)
BS1 half mirror BS2 half mirror (distributor)
D1 Measurement surface position D2 Calibration curve f1, f2 Focal length L0 Objective lens L1 Eyepiece (condensing member)
P Pinhole size PD1 Photodiode (first optical element)
PD2 photodiode (second optical element)
X Measuring surface (surface to be measured)

Claims (9)

In a measuring apparatus that measures the displacement of the measured surface of the object by detecting reflected light from the measured surface of the object,
A distributor for distributing the reflected light to a first optical path and a second optical path different from the first optical path;
A first optical element for detecting the reflected light from the distributor via a first optical path;
A second optical element for detecting the reflected light from the distributor via a second optical path;
The amount of light incident on the first optical element is changed in accordance with the change in the reflected light from the object accompanying the displacement of the measured surface of the object, and the first optical element is different from the first optical element. A measuring apparatus comprising: a light amount changing means for changing a light amount incident on the two optical elements. The light amount changing means is
A first light shielding member provided on the first optical path to the first optical element;
A second light shielding member provided on the second optical path to the second optical element;
A condensing member provided in an optical path to the distributor of the reflected light for condensing the reflected light in the vicinity of the first light shielding member and the second light shielding member. The measuring apparatus according to 1.   One of the first light-shielding member and the second light-shielding member is disposed on the near side of the focal position of the light collecting member in the optical path where the light collecting member collects the reflected light, and the other is placed on the light collecting member. The measuring apparatus according to claim 2, wherein the measuring apparatus is disposed on the far side of the focal position of the optical member.   A third light shield that guides the remaining portion of the reflected light to the first light shielding member and the second light shielding member by restricting a part of the reflected light to the optical path to the distributor of the reflected light. The measuring apparatus according to claim 2, wherein a member is provided. A measuring device according to any one of claims 1 to 3,
By receiving outputs from the first optical element and the second optical element, and measuring the amounts of received light in the first optical element and the second optical element of the measuring device according to the displacement of the surface to be measured of the object A measurement system comprising: a calculation device that previously determines and stores the relationship between the displacement of the measurement surface of the object and the amount of received light. Including a friction force sensor for measuring a friction force generated on a surface to be measured of the object,
6. The measurement system according to claim 5, wherein the friction force sensor outputs data of the measured friction force to the calculation device. An acceleration sensor for detecting a component of the friction force measured by the friction force sensor;
The measurement system according to claim 6, wherein the acceleration sensor outputs data of a component component of the measured frictional force to the calculation device. In the measurement method for measuring the displacement of the measurement surface of the object by measuring the amount of reflected light from the measurement surface of the object,
The reflected light from the measured surface of the object is divided into a plurality of light fluxes,
A measuring method, wherein the displacement of the measured surface of the object is measured by measuring the amount of reflected light for each of the divided light beams.   The reflected light from the surface to be measured of the object is divided into the plurality of light fluxes after passing through averaging means for reducing intensity non-uniformity on the irradiated surface when the reflected light is irradiated. The measuring method according to claim 8.

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