JP2008268000A - Displacement measuring method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of measuring straightness (displacement in z direction) and at least either of pitching and rolling (inclination in rotation around x- and y-axes) simultaneously by a simple configuration. <P>SOLUTION: The device has a light outgoing means 10 for radiating the light led from a light source in two directions or more being different from each other on an object 50 to be measured and two light receiving means 30, 40 or more for receiving the light radiated by the light outgoing means 10, irradiated on the object 50 to be measured, and then reflected and measuring changes of light receiving position. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a displacement measuring method and apparatus, and more particularly to a z-direction displacement of a measurement object suitable for use in measuring a straightness error, a rotation error, etc., which are geometric motion errors with reproducibility of a moving mechanism. The present invention relates to a displacement measuring method and apparatus capable of simultaneously measuring a rotation angle around at least one of an x-axis and a y-axis.

  In recent years, as a “three-dimensional” measuring instrument, the resolution and accuracy of the measurement target in the z-axis direction (height direction) are higher than the resolution and accuracy of the measurement target in the x- and y-axis directions (horizontal two-axis directions). Many machines are put on the market. These are sometimes called “2.5-dimensional measuring machines” because the measurement range in the z-axis direction (height direction) of the measurement target is narrow. For such a measuring machine, there is also a device that installs a moving mechanism and expands the measurement range in the x and y axis directions of the measurement target. What is important for such a moving mechanism is that the straight error in the z-axis direction (also referred to as z-direction displacement) and pitching and rolling (rotational inclination about the x and y axes) when the moving mechanism moves in the x and y axis directions. (Also referred to as angle error) is smaller than the measurement resolution of the measuring instrument, or the error can be corrected.

  On the other hand, in general, the moving mechanism has an unintended motion error. The motion error includes a straightness error, a rotation (tilt) error (pitching, rolling, yawing), a linearity error, and an angle error between a plurality of axes (such as a squareness error). Since these errors are reproducible geometric motion errors, they can be corrected by measuring them efficiently.

  There are two methods for measuring the motion error, a contact type and a non-contact type. The contact type is highly reliable, but damages the measurement object. In particular, if measurement is performed with a highly accurate reference device installed in the moving mechanism, it is necessary to avoid repeated measurement. On the other hand, the non-contact type is preferable to the contact type because a measurement result with high reliability can be obtained when measuring in a well-controlled environment using a high-precision reference plane without damaging the measurement target. There are many cases.

  Therefore, a sensor that measures displacement or rotational tilt in a non-contact manner can be used to correct the error of the moving mechanism. For example, there are a capacitance type displacement sensor, an optical fiber sensor, an interferometer, an autocollimator and the like. In particular, Patent Documents 1 and 2 show a simple straightness measurement method that is non-contact type and can perform highly accurate straightness measurement without being affected by the accuracy of the guide surface of the scanning mechanism. Yes. Further, Patent Document 3 describes a displacement measuring apparatus that is non-contact type and has a function of setting the rotational inclination of a displacement measuring system to an inclination suitable for measurement. And also in patent document 4, the optical displacement measuring device by which the displacement amount and rotation inclination when a measuring object displaces is calculated | required by non-contact type is made | formed.

JP 2003-232625 A JP 2003-254747 A Japanese Patent Laid-Open No. 11-212416 JP-A-7-63510

  However, in general, capacitance displacement sensors, optical fiber sensors, interferometers, and the like are only subject to displacement. Therefore, in order to measure the rotational inclination of the measurement object, it is necessary to use a plurality of displacement sensors and obtain the difference from the displacement, which complicates the apparatus and measurement control. Some interferometers can be evaluated for rotational tilt by measuring the shape of the surface. However, the interferometer requires high speed due to the complexity of the mechanical phase shift and restrictions on the video rate of the CCD camera. Not suitable for measurement.

  In addition, the autocollimator is intended only for the rotation inclination, the measurement speed is slow, and many are not suitable for the purpose of simultaneously measuring the displacement.

  The inventions described in Patent Documents 1 and 2 are intended only for straightness (displacement), and a plurality of displacement sensors are used to measure the rotation inclination, so that the apparatus and measurement control are complicated. In the invention described in Patent Document 3, the rotation inclination is set to an inclination suitable for displacement measurement, and the rotation inclination cannot be measured simultaneously. The invention described in Patent Document 4 can simultaneously measure displacement and rotational tilt, but has a problem such as a structure such as a liquid crystal shutter for switching light irradiation to a measurement object and complicated control. Was.

  The present invention has been made to solve the above-described conventional problems, and has a simple configuration and at least one of straightness (displacement in the z direction) and pitching and rolling (rotational inclination about the x and y axes). It is an object of the present invention to provide an apparatus for simultaneously measuring the above.

  The present invention emits light guided from a light source in two or more directions different from each other on a measurement object, and measures the change in the light receiving position of a plurality of lights irradiated and reflected on the measurement object. The problem is solved by obtaining the displacement of the measurement object.

  By providing a reference plane on the measurement target, emitting light guided from the light source in two or more different directions on the reference plane, and measuring changes in the light receiving positions of the plurality of lights reflected on the reference plane The displacement of the measurement object can be obtained.

  Further, a calibration value can be collected in advance for the light reflecting surface, and the displacement measurement result of the measurement object can be corrected using the calibration value.

  Further, it is possible to measure the straightness error and at least one axis angle error in the direction perpendicular to the moving direction in the moving mechanism.

  The present invention also provides light emitting means for emitting light guided from a light source in two or more directions different from each other on the measurement object, and the light emitted by the light emission means is applied to the measurement object and reflected. A displacement measuring device comprising: two or more light receiving means capable of receiving the received light and measuring a change in the light receiving position.

  Further, the light guided from the light source is guided to the light emitting means from one possible emission port, and the light guided from the light source is a predetermined amount with respect to the normal line of the measurement target. The measurement object can be irradiated with an angle.

  Further, the light emitted from the light emitting means is irradiated in three or more directions to be measured, so that the straightness error and the biaxial angle error can be measured.

  The light emitting means may have an optical fiber having a cone-shaped tip.

  According to the present invention, it is possible to simultaneously measure the displacement and the rotational inclination of at least one axis with a simple configuration. For this reason, when used for correction of the moving mechanism, it is possible to efficiently measure the handling error. In addition, when the reference plane is provided on the measurement target, high-precision measurement is possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a displacement measuring apparatus capable of measuring a z-direction displacement and a rotational tilt around a y-axis according to the present embodiment, FIG. 2 is a cross-sectional view of a light emitting means of the present embodiment, and FIG. 3 is a z-direction. FIG. 4 is a diagram showing the principle of measuring displacement, FIG. 4 is a diagram showing the principle of measuring the rotational tilt around the y axis, and FIG. 5 is a schematic diagram when calibrating the moving mechanism according to this embodiment.

  First, the configuration of the present embodiment will be described in detail with reference to FIGS.

  In this embodiment, as shown in FIG. 1, a light emitting means 10, a first light receiving element 30 as one of light receiving means, a second light receiving element 40 as another light receiving means, and not shown. A signal processing unit.

The light emitting means 10 has one emitting port 20 and has a function of emitting light branched in two directions therefrom. Specifically, as shown in FIG. 2, for example, the light emitting means 10 includes an optical fiber 11 through which light is guided from a light source, first and second fiber folders 12 and 13, and first and second lens holders 14. , 15, first and second lenses 16, 17, and a housing 18. As shown in FIG. 2, the tip of the optical fiber 11 has a cone shape polished at a predetermined angle, and the guided light can be divided into two lights at the exit port 20. Then, the optical fiber 11 is fixed to the casing 18 by the first and second fiber folders 12 and 13, the first lens 16 is fixed by the first lens holder 14, and the second lens holder 15 The second lens 17 is fixed. The first lens 16 and the second lens 17 have the function of converting the two lights emitted from the emission port 20 of the optical fiber 11 into two parallel lights. At this time, it is desirable that the diameter of the parallel light beam is small. If it is small, the diameter of the received light becomes small, so that the displacement measuring device itself as well as the light receiving means 30 and 40 can be downsized. The two parallel lights are adjusted to coincide with the xz plane. Further, the bisector of the two lights is set as the z-axis, and the measurement target 50 is made to coincide with the x-axis orthogonal to the z-axis (θ ₁ = θ ₂ and the z-axis is the normal line of the measurement target 50), Displacement and rotational tilt are easily required.

  The first and second light receiving elements 30 and 40 are disposed at target positions with respect to the z axis, and for example, a photodiode having two or more divisions can be used.

  The signal processing unit has a storage unit therein and is connected to the first and second light receiving elements 30 and 40. Then, using the initial value of the storage unit, the signals detected by the first and second light receiving elements 30 and 40 are processed to obtain the z-direction displacement and the rotational inclination about the y-axis. Each value is stored in the storage unit. For example, when the light emitting means 10 and the light receiving means are fixed to the same housing, the signal processing unit controls the light source that supplies light to the light emitting means inside the housing, and the control of both means. By providing together with the means, it is possible to reduce the size.

  Thus, in this embodiment, it is possible to make the displacement measuring device simple and easy to downsize.

  Next, the operation of this embodiment will be described.

  As shown in FIG. 1, the light branched in two directions from the light emitting means 10 is reflected by different surfaces of the measurement object 50 and enters the first and second light receiving elements 30 and 40. The first and second light receiving elements 30 and 40 measure the change in the position of the light in the x-axis direction, and the signal processing unit determines the displacement of the measurement object 50 about the z-direction and the y-axis according to the measurement principle described later. Can be obtained simultaneously.

  At the time of manufacture of the present embodiment, a reference device that is sufficiently good for accuracy that requires flatness is set as the measurement object 50, and reflected at predetermined positions (x5, z5) and (x1, z1) shown in FIG. The first and second light receiving elements 30 and 40 are installed so that light can come. Hereinafter, this state is referred to as a “reference state”. In this “reference state”, since z2 = x3 = z4 = 0 in FIG. 1, assuming that z3 = L, x4 = R1, and z5 = F1, x5 is obtained as shown in Equation (1).

x5 = L * tanθ ₁ + F1 * tanθ ₁ (1)

  Next, the measurement principle for obtaining the z-direction displacement and the rotational tilt around the y-axis simultaneously will be described in detail.

  First, the displacement D1 when the measurement object 50 is displaced by H in the z direction is obtained using FIG. Then, it can express like Formula (2).

H = -D1 / 2 / tanθ ₁
D1 = -2 * H * tanθ ₁ (2)

  Next, the displacement D2 when the measurement object 50 is rotated by the angle α and tilted about the origin is obtained with reference to FIG. First, in order to consider the light that enters the first light receiving element 30, the coordinates of the reflection position on the measurement object 50 are set to (x41, z41). Then, each value can be expressed as the following equations (3) and (4) as a function of the rotational inclination α.

x41 = L * R1 / (L + R1 * tanα) = L * tanθ ₁ / (1 + tanα * tanθ ₁ (3)
z41 = L * R1 * tanα / (L + R1 * tanα)
= L * tanθ ₁ * tanα / (1 + tanα * tanθ ₁ ) (4)

  Since the reflection position on the measurement object 50 is different, the light reception position on the first light receiving element 30 is shifted from the “reference state”. The rotational inclination α can be obtained by measuring the deviation amount.

  The equation of the straight line of the reflected light can be expressed by equation (5).

z−z41 = tan (π / 2−θ ₁ + 2 * α) * (x−x41) (5)

  Since the value of z5 of the first light receiving element 30 is F1, when the displacement from the “reference state” in the x direction is D2, Expression (5) is expressed as Expression (6).

F1−z41 = tan (π / 2−θ ₁ + 2 * α) * (x5 + D2−x41) (6)

  Therefore, D2 is obtained as shown in Equation (7).

D2 = (F1-z41) / tan (π / 2-θ ₁ + 2 * α) -x5 + x41 (7)

近似できるため、式（７）は式（１１）のような近似式で表すことができる。 Therefore, by substituting the value of x5 in the equation (1) into the equation (7), the rotational inclination α can be obtained from the equations (3) and (4). At this time, when α is small, as in equations (8), (9), and (10),

Since it can be approximated, Expression (7) can be expressed by an approximate expression such as Expression (11).

  In this case, since it is assumed that α is small, Equation (11) can be approximated to Equation (12) to obtain D2.

  Using the values of D1 and D2 described above, the displacement of the measurement object 50 when the displacement in the z direction and the rotational tilt around the y axis occur simultaneously is obtained. At this time, the displacement M1 of the light receiving position obtained by the first light receiving element 30 is the sum of D1 and D2, and therefore, for M1, Equation (13) is obtained from Equation (2) and Equation (7).

M1 = (F1-z41) / tan (π / 2-θ ₁ + 2 * α) -x5 + x41-2 * H * tan θ ₁
(13)

  Using equation (12) after approximation of equation (7), equation (14) is obtained.

  At this time, if the above-described method for obtaining the displacement of the incident position of the light on the first light receiving element 30 is also applied to the light entering the second light receiving element 40, the light on the second light receiving element 40 is reflected. The displacement M2 of the incident position can be expressed by Expression (15).

Therefore, by calculating Equation (14) and Equation (15) as shown in Equation (16), the rotational inclination α and the z-direction displacement H about the y axis are obtained from the measured displacements of M1 and M2. Can do.

  In this way, by using the amount of change in the light receiving position obtained from the two light receiving means, it is possible to simultaneously obtain the z-direction displacement and the rotational inclination about the y axis.

  Next, a case where calibration is performed by measuring only the displacement in the z direction of the moving mechanism and the rotational inclination (pitching) about the y axis according to the present embodiment will be described in detail with reference to FIG. As shown in FIG. 5, the displacement measuring apparatus 1 of this embodiment is fixed to the apparatus support structure 2 fixed to the guide 5 of the moving mechanism. On the other hand, a reference plane 3 (for example, an optical flat) for reflecting the light emitted from the displacement measuring device 1 is provided on the table 4 of the moving mechanism that is the measurement target.

  With such a configuration, the table 4 of the moving mechanism is moved by a predetermined moving amount along the guide 5 of the moving mechanism, and the reflected light from the reference plane 3 is measured by the displacement measuring device 1 according to the present embodiment. Based on the above-described principle, it is possible to obtain the z-direction displacement and the rotational inclination about the y-axis corresponding to a predetermined movement amount.

  In this way, it is possible to efficiently and accurately obtain the z-direction displacement and the rotational tilt around the y-axis, which are the movement errors corresponding to the predetermined movement amount of the moving mechanism. In addition, by applying these motion errors as correction data to this moving mechanism, a highly accurate moving mechanism can be obtained very simply and inexpensively without using a large-scale and expensive high-accuracy moving mechanism. The same movement as that used can be realized.

  At this time, if the calibration value is collected in advance and stored in the storage unit in the signal processing unit before the reference plane 3 is prepared in the table 4 of the moving mechanism, for example, z is obtained with respect to a predetermined moving amount. After obtaining the directional displacement and the rotational inclination around the y-axis, the table 4 of the moving mechanism is calibrated with the calibration value of the reference plane 3 so that the displacement in the z-direction and the rotational inclination around the y-axis can be determined with higher accuracy. As a result, the movement control can be performed with higher accuracy.

  Next, a second embodiment of the present invention will be described. This embodiment is the same as the schematic configuration of the first embodiment shown in FIG. However, the light emitting means 10 has the configuration shown in FIG.

  For example, the light emitting means 10 includes first and second optical fibers 11a and 11b through which light is guided from a light source, and first and second optical fibers 11a and 11b that fix the first and second optical fibers 11a and 11b to the housing 18c, respectively. Two fiber folders 12a, 12b, 13a, 13b, first and second lens holders 14, 15, first and second lenses 16, 17, and a housing 18c. That is, it is composed of two optical fibers 11a and 11b, and is different from the first embodiment in that each is fixed to the housing 18c by the first and second fiber folders 12a, 12b, 13a, and 13b. It is. In the present embodiment, as shown in FIG. 6, the tips of the first and second optical fibers 11a and 11b can be realized by ordinary end face polishing, which is necessary for the optical fiber 11 of the first embodiment. Therefore, there is an advantage that the manufacturing is easier. In the present embodiment, the light exit 20 is a position where the two optical axes shown in FIG. 6 intersect. The other components are the same as the functions described in the first embodiment, and thus description thereof is omitted.

  Further, the operation principle and the application to the moving mechanism are the same, and thus the description thereof is omitted.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic configuration diagram of a displacement measuring apparatus capable of measuring the z-direction displacement and the rotation angles around the y-axis and the x-axis according to the present embodiment.

  As shown in FIG. 7, the configuration of the present embodiment includes a light emitting means 10d, a first light receiving element 30x on the x axis constituting the light receiving means, a second light receiving element 40x, and a first on the y axis. A light receiving element 30y and a second light receiving element 40y. That is, the two light receiving elements 30y and 40y are arranged on the y axis, which is different from the first embodiment. Further, the light emitting means 10d is different from the first embodiment in that parallel light is emitted not only in the x-axis direction but also in the y-axis direction. Since the functions are the same as those of other components, description thereof will be omitted.

  By adopting such a configuration, it is possible to simultaneously obtain the z-direction displacement and the rotation angles around the x-axis and the y-axis, which are not in the first embodiment, with high accuracy.

  Since the operation principle is the same, the description is omitted. In the case where the present embodiment is applied to the moving mechanism, it is possible to obtain the rotational inclination about the y-axis at the same time, so that the displacement in the z direction, which is the movement error corresponding to the predetermined moving amount of the moving mechanism. In addition, the rotational inclination around the x-axis and the y-axis can be obtained efficiently and accurately at the same time.

  In the present embodiment, in order to simultaneously measure the z-direction displacement and the rotation angles around the x-axis and the y-axis, four light receiving elements 30x, 30y, 40x, and 40y are placed on the X and Y axes. Arranged every 90 degrees with the exit port 20 as the center, four parallel lights were emitted from the light emitting means 10d in that direction, but three light receiving elements on the xy plane, for example, with the exit port 20 as the center Arranging at an interval of 120 degrees and emitting three parallel lights from the light emitting means in the direction also has the advantage of being simpler and smaller than the third embodiment, and has the same effect. It is possible to obtain. It goes without saying that such a configuration is also included in the present invention. Further, even when five or more parallel lights are emitted from the light emitting means and a light receiving means corresponding to the emitted light is provided, the same effect as the present embodiment can be obtained. Needless to say, it is included in the present invention.

  As described above, the first to third embodiments have been described. However, the light receiving element constituting the light receiving means is not limited to the photodiode. For example, the light spot position detecting element (PSD), CCD, or CMOS camera (especially high speed) Even a line type) is included in the present invention. Further, the present invention includes the case where the angles θ1 and θ2 of the light emitted from the light emitting means are not the same.

  The signal processing unit is not only provided in the same housing as the light emitting means and the light receiving means, but may be provided as a separate body, for example, in a general-purpose personal computer. Included in the invention.

  Further, in the principle of the present invention, it is also included in the present invention to obtain the rotation inclination and displacement by numerical calculation using a computer without using the approximate expressions (8), (9), and (10).

  In the calibration of the moving mechanism, if the reflected light from the table surface of the moving mechanism can make sufficient light incident on the light receiving means, the present invention also includes that the reference plane is not used. It is also included in the present invention that calibration values are collected in advance and the z-direction displacement and the rotational tilt about the x-axis and y-axis are corrected using the calibration values. Needless to say, the present invention also includes a case where the reference plane is provided on a measurement object other than the moving mechanism.

  Although the present invention is used only for the calibration of the moving mechanism, the present invention can also be used as a sensor for measuring the movement of the measurement object by roughly fixing the displacement measurement device of the present invention and the measurement object. include. For example, by using the present invention for a probe of a three-dimensional measuring machine, a touch probe or a scanning probe is obtained.

1 is a schematic configuration diagram of a displacement measuring apparatus capable of measuring a z-direction displacement and a rotational tilt around a y-axis according to the first embodiment of the present invention. Similarly, a sectional view of the light emitting means Measurement of displacement in the z direction Similarly, measurement principle diagram of rotational tilt around y-axis Schematic diagram when calibrating the moving mechanism Second Embodiment of the Present Invention Cross-sectional view of light emitting means according to this embodiment Third embodiment of the present invention Schematic configuration diagram of a displacement measuring apparatus capable of measuring the z-direction displacement and the rotation angles around both the y-axis and the x-axis according to this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Displacement measuring apparatus 2 ... Apparatus support structure 3 ... Reference plane 4 ... Table of moving mechanism 5 ... Guide of moving mechanism 10, 10c, 10d ... Light emitting means 20 ... Outlet port 30, 30x, 30y, 40, 40x, 40y ... light receiving element 50 ... measurement target

Claims (8)

The light guided from the light source is emitted in two or more different directions on the measurement target,
By measuring a change in the light receiving position of a plurality of light irradiated and reflected on the measurement object,
A displacement measuring method characterized by obtaining a displacement of the measuring object. A reference plane is provided on the measurement object,
Light emitted from a light source is emitted in two or more directions different from each other on the reference plane;
By measuring the change in the light receiving position of the plurality of lights reflected by the reference plane,
A displacement measuring method characterized by obtaining a displacement of the measuring object.   The displacement measurement method according to claim 1, wherein a calibration value is collected in advance for the light reflecting surface, and the displacement measurement result of the measurement target is corrected using the calibration value.   4. The displacement measuring method according to claim 1, wherein a straightness error and at least one axis angle error in a direction perpendicular to the moving direction in the moving mechanism can be measured. Light emitting means for emitting the light guided from the light source in two or more different directions on the measurement object;
Two or more light receiving means capable of measuring the change in the light receiving position by irradiating the measurement object with the light emitted by the light emitting means and receiving the reflected light;
A displacement measuring apparatus comprising: The light guided from the light source is guided to the light emitting means from an emission port that can be assumed as one,
6. The displacement measuring apparatus according to claim 5, wherein the light guided from the light source is applied to the measuring object at a predetermined angle with respect to the normal line of the measuring object.   7. The straightness error and the biaxial angle error can be measured by irradiating the light emitted from the light emitting means in three or more directions of the measurement target. 8. Displacement measuring device.   The displacement measuring device according to claim 5, wherein the light emitting means includes an optical fiber having a conical tip.

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