JP2010139306A - Measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detection device capable of positioning accurately the tip of an object on a target object surface, such as a processing tool on a processing surface. <P>SOLUTION: A light source light flux is focused on a desired position on the target object surface, and an intensity change of reflected light and a change of a beam direction distribution of a reflected light flux which are generated when bringing the object tip close to the focused point are detected, and the object is brought close to the target object surface with high resolution and positioned. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a measurement technique, and more particularly to a measurement apparatus that easily and accurately measures a tip position and a tip shape for positioning on a target object at a tip of a protrusion.

  Along with the increasing demand for improvement in machining accuracy, for example, improvement in the precision of the cutting start is required for the measurement of the relative position between the workpiece and the tool. Currently, in order to position the tip of a tool at a predetermined position of a workpiece, the tool tip is observed with a microscope. It is also known that the tip shape can be measured with an atomic force microscope if the tool tip can be positioned in a measurable region of the atomic force microscope. However, since the resolution of the tool position by microscopic observation is insufficient, it takes a long time to determine the relative position by trial and error.

  It has also been attempted to know the position origin of the tool tip by aligning the tool tip with the focal position of the light beam. In this positioning method using the focal point of the light beam, a method of measuring a change in the amount of light due to the blockage of the light beam by the tool tip near the focal point is employed.

  However, in the method using the focal position of the light beam, the positional relationship between the focal position, the coordinates on the machine tool, and the tool tip can be determined. There is a problem of not knowing. Also, when positioning at the focal point, it is not sufficient as positioning resolution to measure only the amount of light shielding by the tool tip.

  On the other hand, a method of measuring the tool tip position from a diffraction image of a light beam incident on a minute gap is also known. In this method of measuring a diffraction image, as shown in FIG. 4, a light beam PB is irradiated from a light source to a minute gap between a target object OB and a target object surface TP, and a diffraction image by the diffraction light is received by a light receiving element. For example, the change in the gap is evaluated from the relationship between the interval between the positive and negative first order diffraction images and the minute gap.

Patent Document 1 uses this principle to irradiate laser light emitted from a laser light source onto a slit having a predetermined width formed by the edge of a reference plate and the edge of a cutting tool. A technique has been disclosed in which the position of a bite is obtained by generating the light, receiving the diffracted light with an optical sensor, and measuring a light / dark pattern resulting from the difference in light intensity.
JP 05-272925 A

  However, in the prior art of Patent Document 1, since the light beam does not pass through the gap of the wavelength of the light beam (for example, 400 nm for blue-violet laser light) or less, the diffraction pattern of the transmitted light cannot be appropriately formed, and a minute gap is measured. There is a problem that is difficult. In addition, in the case of a convex shape with a sharp tip, there is also a problem that it is difficult to measure the gap because the generated diffraction pattern is not stable.

  In view of such a problem, the present invention detects not only the change in the amount of light in the light receiving device due to the reference light beam being blocked by the target tip, but also the change in the direction of the light beam in the reference light beam. An object is to provide an apparatus capable of detecting a position with high accuracy.

  The measuring apparatus according to the first aspect of the present invention includes a light source for converging a reference light beam that converges into a small dot or thin line at a position on a target object surface that approaches the tip of a convex portion, and a reflected light beam from the target object surface. A light receiving device that measures at least one of the light beam direction distribution of the reflected light beam, the average direction of all the light rays in the light beam, the intensity of the light beam, and the intensity distribution, and based on the output of the light receiving device, A distance between the target object surface and the tip of the convex portion is obtained.

  A measuring apparatus according to a second aspect of the present invention includes a light source for converging a reference light beam that converges in a small dot shape or a thin line shape on an opposite side surface of a film-like surface pressed against a convex tip, and an opposite side surface of the film-like surface. A light receiving device that measures at least one of the light beam direction distribution of the reflected light beam, the average direction of all the light rays in the light beam, the intensity of the light beam, and the intensity distribution, and outputs to the output of the light receiving device. Accordingly, the shape of the side surface opposite to the deformed film-like surface is obtained.

  According to the first aspect of the present invention, the light receiving device receives the reflected light beam from the target object surface, and the light beam direction distribution of the reflected light beam, the average direction of all the light beams in the light beam, the intensity and intensity distribution of the light beam. And measuring the distance between the target object surface and the tip of the convex portion with high accuracy based on the output of the light receiving device.

  Furthermore, the shape of the tip of the convex portion can be obtained based on the output of the light receiving device.

  According to the second aspect of the present invention, the light receiving device receives a reflected light beam from an opposite side surface of the film-like surface, and distributes the direction of the reflected light beam, the average direction of all the light rays in the light beam, and the intensity of the light beam. And a light-receiving device that measures at least one amount of the intensity distribution, and according to the output of the light-receiving device, the shape of the opposite side surface of the film-shaped surface can be obtained with high accuracy. If the deformation is a transfer of the shape of the tip of the convex portion, the shape of the tip of the convex portion can be obtained.

  The light receiving device preferably measures the angle of incident light using the relationship between the reflectance and the incident angle at the boundary surfaces having different refractive indexes.

  The light receiving device preferably measures an average direction of incident light and a direction distribution of incident light.

  The light receiving device is preferably an angle sensor that adopts the principle of a photoelectric autocollimator using a split photodiode.

  The light receiving device preferably has a plurality of light receiving portions.

  According to the present invention, a part or all of a reference light beam that converges and is reflected in a small dot or thin line at a predetermined point on a positioning target surface is affected by the tip of a target object and is a light beam. In order to detect that the traveling direction has been changed, not only the light quantity detection sensor but also the light beam direction measurement sensor is used.

  The present invention is also a thin plate in which a target surface serving as a positioning reference can be deformed, and a part or all of a reference light beam that converges and reflects into a small dot or thin line at a predetermined point on the target surface. In order to detect that the traveling direction of the light beam has been changed by being influenced by the tip of the target object that is pushed from the back side of the target surface, measurement is performed not only by the light amount detection sensor but also by the light beam direction measurement sensor. And

  The present invention is characterized in that the principle of angle detection in the light receiving device is an angle sensor adopting the principle of a photoelectric autocollimator using a divided photodiode.

  The present invention is also characterized in that the principle of angle detection in the light receiving device is an angle sensor that uses the relationship between the reflectance and the incident angle at the boundary surfaces having different refractive indexes.

  The present invention is also characterized in that the light receiving device comprises a plurality of light receiving portions.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A illustrates a workpiece surface (hereinafter referred to as a target object surface TP), which is an example of a tip of a convex portion (hereinafter referred to as a target object OB), using the measurement apparatus of the present invention. It is a figure which shows the state which measures both distance in the state made to approach. FIG.1 (b) is a figure which expands and shows the site | part shown by arrow IA.

  As shown in FIG. 1A, a holder (not shown) that can move in a three-dimensional direction symmetrically with respect to the target object plane TP, laser, etc. A light source luminous flux generation unit SBG composed of a light source LS and a lens LS and a light receiving device RS including a light receiving element (CCD or the like) capable of measuring the position and intensity of received light are held. The target object OB is held by another holder (not shown) that can move in the three-dimensional direction and can move independently. The laser light LB emitted from the light source LS becomes convergent light via the lens LS (converges into small dots or thin lines), and is condensed at a position where the tip of the target object OB faces the target object plane TP. The reflected light RB of the target object surface TP is incident on the light receiving element of the light receiving unit RS as divergent light.

  Here, it is assumed that the target object OB attached to a holder (not shown) is brought close to the target object plane TP as shown in FIG. When the target object OB is farther from the target object plane TP than the position indicated by the solid line in the figure, the laser beam LB that is convergent light is not blocked by the target object OB, and is thus incident on the light receiving element of the light receiving device RS. The reflected light RB has a light intensity distribution having a so-called Gaussian distribution. This is the initial state.

  On the other hand, when the target object OB approaches the target object plane TP from the position indicated by the solid line in the figure, a part of the laser light LB (the part indicated by the oblique line in FIG. 1B) is blocked by the target object OB. It becomes. The blocked laser light is reflected with almost no absorption if the target object OB is close to a mirror surface. A part of the reflected light returns to the light source LS side, and the rest of the reflected light is reflected on the target object surface TP, while the gap between the tip of the target object OB and the target object surface TP or the tip of the target object OB. It goes around the periphery, reaches the light receiving device RS side, and is detected by the light receiving element.

  At this time, the remaining laser light LB not blocked by the target object OB is reflected only by the target object surface TP and is incident on the light receiving element RS, so that the signal output from the light receiving element corresponds to the sum of the two. To be. That is, the sum of the reflected light RB incident on the light receiving element of the light receiving device RS has a light intensity distribution having an asymmetric shape that is biased toward the Gaussian distribution in the initial state (dotted line in FIG. 1B). reference). Since the shape of the light intensity distribution is uniquely determined according to the distance between the tip of the target object OB and the target object surface TP, the shape of the light intensity distribution and the shape of the target object OB are determined in advance through experiments or simulations. By obtaining the relationship between the distance between the tip and the target object surface TP, the actual distance can be obtained with high accuracy from the shape of the light intensity distribution. Note that the light intensity distribution of the reflected light can be changed according to the reflectance of the surface of the target object OB or the target object plane TP, but the reflectance is set as a parameter and the target object OB or target object plane TP actually used is set. Reflectivity should be applied.

  In the present embodiment, the disturbance due to the target object OB in the vicinity of the focal position of the laser beam LB is observed by the light receiving device RS, but the focus is on the target object plane TP that is a target for positioning the target object OB. In addition, by placing the focal position at a predetermined position on the target object plane TP, the positioning of the target object OB near the focal point becomes the three-dimensional positioning with respect to the target plane. If the object surface TP is the machining surface and the target object OB is the tool tip, the tool tip position can be positioned at a predetermined position on the machining surface with high accuracy. For example, it is said that it is difficult to optically measure such a minute gap because it cannot pass through a gap of the wavelength or less because of the characteristics of light. However, according to the present embodiment, even when the distance between the target object OB and the target object plane TP is equal to or less than the wavelength, there is light that travels around the tip of the target object OB and reaches the light receiving device RS. Therefore, by detecting the state, a minute distance between the target object OB and the target object surface TP can be measured with high accuracy. The intensity of the reflected light itself may be measured with a light receiving device.

  FIG. 2 is a diagram for explaining an example of the light receiving device RS of the present embodiment. Here, the direction of reflected light is obtained. In FIG. 2, the light source beam generation unit SBG is the same, and the light receiving device RS includes an objective lens OL, a prism PS having a refractive index different from that of air, a first light receiving unit RP1, and a second light receiving unit RP2. Have The reflected light RB from the target object surface TP is reflected by the objective lens OL, then enters the prism PS, a part of the light RB1 is reflected by the boundary surface DS, and the remaining light RB2 is refracted and transmitted. . A part of the light RB1 is detected by the first light receiving unit RP1, and the remaining light RB2 is detected by the second light receiving unit RP2. This functions as an angle sensor that detects the angle of the reflected light beam. The principle will be described.

  FIG. 7 shows an example of the relationship between the incident angle and the reflectance at the boundary surface between the high refractive index and the low refractive index. As shown in FIG. 7, light incident on the boundary surface at an angle greater than the critical angle is reflected by 100%. Using this property, when the diffused reflected light RB whose direction is to be measured in FIG. 2 is incident on the prism PS via the objective lens OL (in the example of FIG. The upper limit is about 8 degrees from the star angle to the critical angle, and it becomes narrower when considering the fluctuation width of the angle in the measurement range.) The incident angle of any ray in the luminous flux to the boundary surface is It is possible to realize a state in which the angle is not greater than the critical angle or less than the Brewster angle. Accordingly, each light beam in the light beam to be measured is branched with a reflectance corresponding to the direction. Further, the average incident angle of the entire light beam with respect to the boundary surface can be known from the difference between the reflected light amount (signal of the first light receiving unit RP1) and the transmitted light amount (signal of the second light receiving unit RP2) as the entire light beam. become able to.

  As described above, when the light is received through the boundary surface DS where the refractive index is changed as shown in FIG. 2, the sum of the outputs of the first light receiving unit RP1 and the second light receiving unit RP2 is obtained. Thus, the total amount of light reaching the light receiving portion can be determined, and the direction of the reflected light beam reaching the objective lens OL can be determined from the difference between the outputs of the first light receiving portion RP1 and the second light receiving portion RP2. Since the direction of this light beam is uniquely determined according to the distance between the tip of the target object OB and the target object surface TP, the direction of the light beam determines the direction between the tip of the target object OB and the target object surface TP. The distance can be obtained with high accuracy. The direction of the light ray can be selected by selecting the light receiving element used for the light receiving device RP, from the one that knows only the average one to the one that knows the direction distribution in detail. Can be obtained. Such a light receiving device RS functions as an angle sensor that adopts the principle of a photoelectric autocollimator that uses split photodiodes (RP1, RP2). Note that an average direction of all rays in the reflected light beam may be obtained by the light receiving device.

  According to the geometric optical theory, if the target object OB has a symmetrical shape with respect to the vertical axis and is on the focal point (condensing spot) with respect to the horizontal direction in the figure, the target object approaches the target point along the vertical direction. At this time, the laser beam LB that is reflected by the surface of the target object OB and changes its direction is generated symmetrically on the light source side and the light receiving device side. When the target object OB is brought close to the focal point along the vertical direction when it is deviated from the focal point in the horizontal direction, only one of the laser beam LB and the reflected light RB starts to be affected.

  As another embodiment, not only the optical axis of the light receiving device RS is aligned with the optical axis of the reflected light without the target object OB (referred to as the reference optical axis), but also the reflected light from the target object OB is different. By receiving light with a plurality of light receiving devices RS in the direction, it is possible to receive light in a direction that does not reach the light receiving device RS on the reference optical axis because it is affected by the target object. Position information can be obtained with high accuracy.

  In another embodiment shown in FIG. 8, the state of the two-dimensional branch and the subsequent detection branch is shown only by the central ray of the light beam. In FIG. 8, the prism inclined in the xz plane on the transmission side of the half prism HP that transmits incident light (reflected light RB) that has passed through the objective lens OL by 50% (z direction) and reflects 50% (x direction). A prism PS1 having a slope PSy is arranged, and a prism PS2 having a prism slope PSx inclined in the yz plane is arranged on the reflection side of the beam splitter BS. The prism slopes PSy and PSx are angle detection boundary surfaces in contact with air, which is a medium having a lower refractive index, and are in a relationship of being rotated by 90 degrees around the optical axis of the light beam before the division.

  Here, incident light whose direction is to be detected is incident on the beam splitter BS from below, and is then divided into z and x directions and directed to the prisms PS1 and PS2 (which constitute a boundary surface for detection branching), respectively. And Each light is incident on the prism inclined surfaces PSx and PSy (as boundary surfaces for detection branching) at a predetermined angle, and is divided into reflected light and transmitted light. At this time, the reflected light of the prism slope PSy is detected by the light receiving device RLD1y, and the transmitted light of the prism slope PSy is detected by the light receiving device RLD2y. The reflected light of the prism inclined surface PSx is detected by the light receiving device RLD1x, and the transmitted light of the prism inclined surface PSx is detected by the light receiving device RLD2x, and the light intensity is converted into a current by the light receiving element in the light receiving device. Thereafter, although not shown in the figure, the difference between the reflected light and the transmitted light on each slope is taken by the current-voltage conversion circuit and the differential arithmetic element, and this can be used to accurately measure the angle of the incident light beam. . Further, the prism PS1 is rotated around an axis parallel to the x axis so that the output of the differential arithmetic element becomes zero, the prism PS2 is rotated around an axis parallel to the y axis, and the origin of the light beam direction is set. Can be easily determined.

  FIG. 3 is a diagram for explaining an embodiment in which the shape of the tip of a convex portion such as the tip of a tool is measured using a film-like surface. When the film-like surface (or thin plate-like surface) EB is used as a target for positioning the target object OB, the change in the position of the tip of the target object OB is replaced with a minute deformation of the film-like surface EB, and the angle change of the minimum part Therefore, it is expected that the position of the tip can be detected with higher sensitivity than when the tip of the target object OB is directly observed to obtain the position. Further, if a light receiving device that measures the distribution of the light beam direction angle is used, the shape change before and after the wear, such as the tip of the cutting tool, can be evaluated.

  Here, the light source device and the light receiving device used in the above-described embodiment are used. As shown in FIG. 3, when the target object OB is brought into contact from the back side of the film-shaped surface EB and the film-shaped surface EB is pushed up, the tip shape of the target object OB is transferred to the surface of the film-shaped surface EB. A protruding portion PP is formed. Such deformation is preferably elastic deformation, but may be plastic deformation.

  In this state, a laser beam from a light source (not shown) is condensed on the protrusion PP on the surface of the film-like surface EB, and the light intensity distribution of the reflected light of the projection spot PS on the film-like surface EB at that time Alternatively, by measuring the direction distribution of the reflected light with the light receiving device RS, the shape of the protrusion PP, that is, the tip shape of the target object OB can be obtained with high accuracy.

  Note that when measurement is performed with the light receiving device while bringing the tip of the target object OB close to the film-shaped surface EB, the film-shaped surface EB starts to be deformed from the moment of contact with the back surface, and this reflects the reflected light beam from the focal point. Since it appears in the light beam direction distribution, the target object OB can be brought into contact with the back surface of the film with extremely high position resolution. The two-dimensional position in the plane direction with respect to the focal point can also be confirmed from the symmetry of the light beam direction distribution of the reflected light beam.

  FIG. 5 is a diagram showing an outline of a tip shape measuring apparatus in which a light source and a light receiving device are integrated, and shows a state where the tip of the target object OB is placed at a predetermined position. The light source and the light receiving device RS are the same as those in the above-described embodiment. Here, depending on the tip shape of the target object OB, the direction of the reflected light of the laser beam LB reflected on the surface of the target object OB changes, and the light beam direction distribution and the light intensity distribution obtained by the light receiving device RS change. Even if the accuracy of measuring the shape itself is not high, when a tool or the like wears and deforms with use, its tip is the same as the measurement position of the tip shape measuring device in FIG. When placed in a posture, the progress of wear of the tip can be determined from the measurement of the light direction distribution and the light intensity distribution.

  FIG. 6 shows an outline of a measuring apparatus for measuring the slit width. The light source and the light receiving device RS are the same as those in the above-described embodiment. Similarly, the direction of the reflected light of the laser light LB reflected in the slit ST changes depending on the width of the slit ST, and the light beam direction distribution and the light intensity distribution obtained by the light receiving device RS change. As shown in FIG. 6, in the apparatus that measures the light beam direction distribution and the light intensity distribution at the same time, the measurement of the width of the slit ST is more accurate than the conventional measurement of the intensity of the light beam or the measurement of the diffraction image. Is possible.

It is a figure which shows a mode when a light source light beam is focused on a target object surface, and a target object is brought close to the focal point. It is a figure which shows embodiment using the interface which a refractive index changes as an angle sensor of a light-receiving part. It is a figure explaining the change of the reflected light of the spot projected on the thin film with the front-end | tip position and shape of a target object. It is a figure which shows the mode of the generation | occurrence | production of the diffraction image in the clearance gap between a target object and a target object surface. It is a figure which shows the outline of the measuring device which detects the change of the target object front-end | tip shape. It is a figure which shows the outline of the measuring device which detects slit width. It is a figure which shows an example of the relationship between the incident angle and the reflectance in the interface surface of a high refractive index to a low refractive index. It is a figure which shows the example of the angle sensor which detects a light beam direction angle distribution two-dimensionally.

Explanation of symbols

OB target object
TP target object surface
SBG light source beam generator
SL light source
SB luminous flux
SOA light source luminous flux optical axis
RS receiver
ROA receiver optical axis
OL objective lens
DS Angle detection interface
RP1, RP2 light receiving part
EB Thin plate, membrane
PS projection spot
DB Diffracted beam
ID diffraction intensity distribution

Claims (7)

  A light source for converging a reference light beam that converges into a small dot or thin line to a position on the target object surface where the tip of the convex portion approaches, and a reflected light beam from the target object surface is received, and the light beam of the reflected light beam A light receiving device that measures at least one of a direction distribution, an average direction of all rays in the light beam, an intensity of the light beam, and an intensity distribution, and based on an output of the light receiving device, the target object surface and the tip of the convex portion A measuring device characterized by obtaining a distance of   The measuring device according to claim 1, wherein the shape of the tip of the convex portion is obtained based on the output of the light receiving device.   A reference light beam that converges into a small dot or thin line is converged on the opposite side of the film-like surface against which the tip of the convex portion is pressed, and a reflected light beam from the opposite side of the film-like surface is received and reflected. A light receiving device that measures at least one of the light beam direction distribution, the average direction of all the light rays in the light beam, the intensity of the light beam, and the intensity distribution; and, depending on the output of the light receiving device, A measuring apparatus characterized by obtaining a shape of an opposite side surface.   The measuring device according to claim 1, wherein the light receiving device measures an angle of incident light using a relationship between a reflectance at a boundary surface having a different refractive index and an incident angle.   The measuring device according to claim 4, wherein the light receiving device measures an average direction of incident light and a direction distribution of incident light.   The measuring device according to claim 1, wherein the light receiving device is an angle sensor adopting a principle of a photoelectric autocollimator using a divided photodiode.   The measuring device according to claim 1, wherein the light receiving device has a plurality of light receiving portions.

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