JP2012145550A - Inter-target absolute distance measurement method of tracking laser interference measuring apparatus and tracking laser interference measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure absolute distance with high accuracy even when distance between a rotation center of a mechanism of a tracking laser interference measurement device and a target is long only by adding a simple mechanism without utilizing a complicated device such as an absolute distance meter.SOLUTION: An inter-target absolute distance measurement method of a tracking laser interference measuring apparatus 10 includes a laser interferometer 13 which irradiates a target 31 with a laser beam and biaxial rotation mechanisms 11, 12 which change an emission direction of the laser interferometer 13, and controls the biaxial rotation mechanisms 11, 12 to make the laser interferometer 13 track the target 31, in which the laser interferometer 13 is arranged at a first position by a translation movement mechanism 14, the target 31 is captured with a laser beam 20 at the first position, next, the laser interferometer 13 is moved to a second position, the target 31 is captured with a laser beam 21 at the second position, a geometric operation for a triangle using a fixed position of the target 31, the first position and the second position as the apexes is performed, and an absolute distance L between the laser interferometer 13 at the first position and the target 31 is measured.

Description

  The present invention relates to a method for measuring an absolute distance between targets of a tracking laser interference measuring apparatus and a tracking laser interference measuring apparatus.

Conventionally, a tracking laser interference measuring apparatus is known as an apparatus that can track and measure the spatial position of a measurement object (see, for example, Patent Document 1).
The tracking type laser interference measuring apparatus uses a biaxial rotation mechanism for an azimuth angle on a horizontal reference plane and an elevation angle with respect to the reference plane so that the laser interferometer can be directed in an arbitrary direction in space. Then, the retroreflector that arbitrarily moves in the same space is tracked as a target, and the variation in the distance between the reference point at the rotation center of the rotation mechanism and the target is measured by laser interference.
According to such a tracking type laser interference measuring apparatus, the spatial position and the moving state of the measurement object can be measured by setting the target on the surface of the measurement object.

In a tracking laser interferometer, a retroreflector is used as a target in order to recursively reflect a laser beam from a laser interferometer.
The retroreflector is an optical component manufactured so that an input light beam and a reflected light beam are parallel to each other, and a typical one is a retro reflector.
The tracking type laser interference measuring apparatus includes a light beam position detector that monitors the amount of deviation (displacement in the direction perpendicular to the laser optical axis) between the emitted light beam and the light beam reflected by the target in order to realize the tracking operation. . Then, the amount of deviation generated by the movement of the target is detected from the output signal of the light beam position detector, and the biaxial rotation mechanism is operated according to the angle adjustment amount converted from the amount of deviation described above. Target tracking is achieved by controlling to zero.

JP 2007-057522 A JP 2007-309677 A JP 2009-229066 A

By the way, in the above-described target tracking operation, in the process of converting the positional deviation amount into the angle adjustment amount, the distance between the rotation center of the two-axis rotation mechanism of the tracking laser interference measurement device and the target is known. There must be.
As a method for measuring this distance, several proposals have been made, such as a method using an absolute distance meter and a method starting from a point whose distance is known in advance.
Patent Document 2 discloses a method of measuring this distance without requiring an additional device.
However, this method has a problem that when the dynamic range of the light beam position detector that monitors the amount of deviation of light beams is small, the distance becomes long and the accuracy of distance measurement decreases.
Patent Document 3 discloses a method of minimizing this accuracy drop by integrating the amount of change in control amount during tracking.
However, even with this method, there is a limit in accurately re-measuring the distance when the tracking is greatly deviated at a long distance.

  The main object of the present invention is when the distance between the rotation center of the mechanism of the tracking type laser interference measuring device and the target is long by adding a simple mechanism without using a complicated device such as an absolute distance meter. However, it is to provide an absolute distance measuring method between targets of a tracking laser interference measuring apparatus and a tracking laser interference measuring apparatus capable of measuring the absolute distance with high accuracy.

  An absolute distance measuring method between targets of a tracking type laser interference measuring apparatus of the present invention includes a laser interferometer that irradiates a target with laser light, and a biaxial rotating mechanism that changes an emission direction of the laser interferometer. A method for measuring an absolute distance between targets of a tracking type laser interferometer that controls an axis rotation mechanism to track the target with the laser interferometer, wherein a first position and a second position at which the laser interferometer can be disposed are Provided on the same measurement axis, the target is fixed at a position away from the measurement axis, the laser interferometer is arranged at a first position, the target is captured by a laser beam at the first position, and the laser interference The meter is moved to the second position, the target is captured by the laser beam at the second position, and the geometric calculation is performed on the triangle having the fixed position of the target, the first position, and the second position as vertices. , In the first position Characterized in that said measuring the absolute distance between the laser interferometer and the target that.

As specific geometric operations, the orientation of the laser interferometer directed to the target at the first position and the second position (the angle indicated by each axis of the biaxial rotation mechanism) and the distance between the first position and the second position If the above is understood, the absolute distance between the laser interferometer in the first position and the target can be obtained by specifying a triangle from these two angles and distances and calculating the length of each side by the sine theorem. it can.
At this time, it is not necessary to measure the distance of the target by laser interference at the first position and the second position, and it is not necessary to measure the reference point or continuously move from the first position to the second position. Therefore, at the first position and the second position, it is only necessary that the laser interferometer can be fixed, and two detachable support portions may be formed on the measurement axis. On the other hand, it may be moved continuously, or a moving mechanism such as a guide rail along the measurement axis may be provided.

  In the method for measuring the absolute distance between targets of the tracking laser interference measuring apparatus of the present invention, a third position different from the first position and the second position is provided on the measurement axis, and the target is laser-beamed at the second position. Then, the laser interferometer is moved to the third position, the target is captured by the laser beam at the third position, and the fixed position of the target, the first position, and the second position are set as vertices. It is desirable to perform a geometric calculation for a triangle having the fixed position of the target, the first position, and the third position as vertices together with the geometric calculation for the triangle.

By performing geometrical computation on the two triangles using such a third position, the laser interferometer in the first position can be obtained even if there is an inclination of the measurement axis with respect to the spatial coordinate system of the tracking type laser interference measuring apparatus. It is possible to accurately measure the absolute distance between the target and the target.
That is, the inclination of the measurement axis with respect to the spatial coordinate system of the tracking type laser interference measurement apparatus is expressed as an azimuth angle on a horizontal reference plane and an elevation angle with respect to the reference plane corresponding to the biaxial rotation mechanism. The azimuth angle and elevation angle of such a measurement axis can be brought close to zero by measurement and adjustment, respectively, but by performing geometric calculation on two triangles, the absolute distance can be calculated without being affected by the inclination of the measurement axis. It can be carried out.

In the method for measuring the absolute distance between targets of the tracking type laser interference measuring apparatus of the present invention, it is desirable that the first position is a measuring position of the laser interferometer in the tracking type laser interference measuring apparatus.
In such a configuration, the absolute distance of the first position obtained by the calculation can be used as it is as a measurement reference in the tracking type laser interference measuring apparatus.

  The tracking laser interferometer of the present invention includes a laser interferometer that irradiates a target with laser light, and a biaxial rotation mechanism that changes the emission direction of the laser interferometer, and controls the biaxial rotation mechanism. A tracking type laser interference measuring apparatus for tracking the target with the laser interferometer, wherein the laser interferometer and the biaxial rotation mechanism can be supported at a first position and a second position on the same measurement axis. It has a mechanism.

  In the present invention, the target can be captured by the laser interferometer while the laser interferometer and the biaxial rotation mechanism are supported at the first position and the second position, respectively. If the target can be captured at these two positions, the absolute distance between the laser interferometer at the first position and the target can be determined based on the method for measuring the absolute distance between targets of the tracking laser interference measuring apparatus of the present invention described above. Can be sought.

In the tracking laser interference measuring apparatus of the present invention,
Preferably, the laser interferometer has a guide rail extending along the measurement axis, and the laser interferometer is guided by the guide rail and is movable on the measurement axis.

  In the present invention, since the laser interferometer is continuously moved by the guide rail, operations such as attachment and detachment can be simplified, and posture accuracy can be maintained.

  According to the absolute distance measuring method between the targets of the tracking laser interference measuring apparatus of the present invention and the tracking laser interference measuring apparatus, a simple mechanism can be added without using a complicated apparatus such as an absolute distance meter. Even when the distance between the center of rotation of the tracking laser interference measurement device and the target is long, the absolute distance can be measured with high accuracy.

The perspective view which shows the apparatus structure of embodiment of this invention. The perspective view which shows operation | movement of the said embodiment. The schematic diagram which shows the 1st measurement in the said embodiment. The schematic diagram which shows the 2nd measurement in the said embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
〔Device configuration〕
In FIG. 1, a tracking laser interference measurement apparatus 10 according to the present embodiment measures a three-dimensional position while tracking the dynamic position of a target 31 supported so as to be arbitrarily movable in space. . The target 31 is supported via a head 30 by a moving mechanism (not shown) that can move in three dimensions with respect to the table 32. As a specific example of such a mechanism, for example, there is a machine tool in which the spindle moves three-dimensionally with respect to the table.
The target 31 is a retro reflector and is attached to the head 30. The target 31 may be another retroreflector.

The tracking laser interference measuring apparatus 10 includes biaxial rotating mechanisms 11 and 12 and a laser interferometer 13.
The first rotation mechanism 11 detects the current rotation angle (azimuth angle θ) with respect to the initial position by an internal encoder and outputs a signal.
The second rotation mechanism 12 is supported by the first rotation mechanism 11, detects the current rotation angle (elevation angle φ) with respect to the initial position by an internal encoder, and outputs a signal.

The laser interferometer 13 is supported by the second rotating mechanism 12, irradiates a laser beam toward a direction (azimuth angle θ, elevation angle φ) specified by the two rotating mechanisms 11, 12, and is retroreflected by the target 31. The laser beam 20 thus received is received, and the change in the distance between the rotation centers of the rotation mechanisms 11 and 12 (intersections of the respective rotation axes) and the target 31 is measured from the interference between the irradiated light and the reflected light.
These two-axis rotating mechanisms 11 and 12 and the laser interferometer 13 are controlled by an externally connected computer system (not shown) for control and measurement calculation. In particular, when the laser interferometer 13 is capturing the target 31, the target 31 is automatically tracked even when the target 31 moves. In addition, the computer system drives and controls the rotation mechanisms 11 and 12 and the laser interferometer 13, takes in necessary measurement values, executes calculation processing necessary for the shape processing, and moves the target 31 from the movement amount or the initial position. Measure the current position based on the accumulated travel.

The above is the basic function of the tracking laser interference measuring apparatus, and the existing configuration is used.
The tracking type laser interference measuring apparatus 10 has a translation mechanism 14 as a support mechanism, and the biaxial rotation mechanisms 11 and 12 and the laser interferometer 13 described above are supported by the translation mechanism 14, and the table 32 has a predetermined surface. Can be moved along the measurement axis.
The translation mechanism 14 may include a highly accurate guide rail that defines a measurement axis, a drive mechanism that can perform a highly accurate feed operation, and an encoder that detects the current position with high accuracy. Specifically, the translational movement mechanism 14 can be configured using a so-called linear stage or the like.

[First measurement]
In FIG. 2, the absolute distance L between the rotation center of the rotation mechanisms 11 and 12 and the target 31 in the tracking laser interference measurement apparatus 10 is measured as follows.
First, the target 31 is arranged at an arbitrary position in the space on the table 32, and the translation mechanism 14 is operated, so that the rotation mechanisms 11, 12 and the laser interferometer 13 are arranged at the first position (shown by dotted lines in FIG. 2). .
Next, the rotation mechanisms 11 and 12 and the laser interferometer 13 are actuated to shift the position of the reflected light beam from the target 31 and the outgoing light beam 20 from the laser interferometer 13, and the output of the optical position detector of the laser interferometer 13 is zero. The rotation mechanism is adjusted so as to become (capturing the target at the first position).

Subsequently, the translation mechanism 14 is operated to move the rotation mechanisms 11 and 12 and the laser interferometer 13 by a known distance l (shown by a solid line in FIG. 2). Then, the rotation mechanisms 11 and 12 are operated again, and the same adjustment is performed so that the positional deviation of the light beam 21 becomes zero (capture of the target at the second position).
Even if the rotation mechanisms 11 and 12 and the laser interferometer 13 are moved from the first position to the second position, the target 31 is not moved. Therefore, the laser beam 20 before the movement and the laser beam 21 after the movement are the target 31. V-shape intersecting at an angle α. The path of the laser beams 20 and 21 and the locus drawn by the rotation center of the rotation centers 11 and 12 when moved by the translation mechanism 14 constitute a triangle O ₀ O _T O ₁ (see FIG. 3). .

In FIG. 3, assuming that the translational distance 1 is known and the angles α, β, and γ of the vertices of the triangle O ₀ O _T O ₁ , if these angles can be measured, the distance L to be calculated is calculated by using the sine theorem. can do.

… (1)

In order to calculate equation (1), the angle α is first obtained. A unit vector directed from the rotation center of the mechanism toward the target is denoted by v ₀ , and a unit vector directed from the rotation center of the mechanism after translation to the target is denoted by v ₁ . If the azimuth angle θ and elevation angle φ output from the rotational position detector associated with the biaxial rotation mechanism of the tracking laser interference measuring apparatus 10 are displayed with subscripts indicating the first position and the second position, respectively, θ ₀ , φ ₀ , θ ₁ , and φ ₁ , and based on these, the vectors v ₀ and v ₁ can be expressed by the following equations, respectively.

… (2)

  The angle α can be calculated from the inner product using these values as follows.

… (3)

Therefore, the angle α and the distance l are obtained, and if the angle γ (or the angle β that can calculate the angle γ) can be obtained, the distance L can be calculated from the equation (1).
As described above, the angle γ or the angle β corresponds to the continuous direction (measurement axis) of the translation mechanism 14 and the laser beams 20 and 21 toward the target (unit vector v in the internal coordinate system of the tracking laser interference measurement apparatus 10). ₀ , v ₁ ). If the continuous direction of the translation mechanism 14 coincides with the X-axis line of the internal coordinate system of the tracking type laser interference measuring apparatus 10 described above, the distance L is obtained by the above-described expression (1).

By the way, in order to obtain the distance L only by the above-described equation (1), it is necessary that the continuous direction of the translational movement mechanism 14 and the X-axis line of the internal coordinate system of the tracking type laser interference measuring device 10 described above coincide. is necessary.
On the other hand, the absolute distance L can be measured regardless of the azimuth offset θ _f and the elevation offset φ _f by performing the following second measurement.

[Second measurement]
As the second measurement, the capture and calculation of the target 31 at the two positions described above are performed twice.
As shown in FIG. 4, in the second measurement, following the capture of the target 31 at the first position, the translation mechanism 14 causes the rotation mechanisms 11 and 12 and the laser interferometer 13 to be separated by a distance l _1. To capture the target 31 to form a _first triangle O ₀ O _T O ₁ . The first triangle O ₀ O _T O ₁ has an apex angle α ₁ and a base length l ₁ along the measurement axis.

Further, they are moved to a third position separated from the second position by a distance l ₂ , and the target 31 is similarly captured to form a second triangle O ₀ O _T O ₂ . The second triangle O ₀ O _T O ₂ has an apex angle (α ₁ + α ₂ ) and a base length along the measurement axis (l ₁ + l ₂ ).
The angles formed by the unit vectors v ₀ , v ₁ , v ₂ in the laser beam direction at the first to third positions and the measurement axis are angles β, γ ₁ , γ ₂ .

Here, the two triangular shapes O ₀ O _T O ₁ and O ₀ O _T O ₂ share a vertex O ₀ that forms an angle β with a side of the length L (absolute distance to be measured).
Therefore, when the sine theorem is applied to each triangle, the following two equations are obtained.

…(Four)

…(Five)

Among these, the two angles α ₁ and α ₂ and the distances l ₁ and l ₂ can be obtained by the first measurement procedure described above.
Further, since the sum of the interior angles of the triangle is expressed in radians, it is π, so the angles γ ₁ and γ ₂ can be transformed as follows using the angles α ₁ , α ₂ , and β.

… (6)

… (7)

  By combining these equations for L, Equation (8) and Equation (9) can be obtained from Equation (10).

… (8)

… (9)

…(Ten)

  In Equation (10), since the only unknown is β, terms including β are collectively transformed to obtain Equations (11) to (13).

… (11)

… (12)

…(13)

  The angle β can be calculated by transforming the equation (13) into the following equation (14).

…(14)

  Finally, if the angle β is substituted into the equation (6), the equation (15) for calculating the distance L is obtained. This is an equation equivalent to equation (1).

… (15)

According to the present embodiment described above, in the tracking type laser interferometer 10, the laser interferometer can be obtained by adding a simple mechanism such as the translation mechanism 14 without using a complicated device such as an absolute distance meter. The absolute distance L between the 13 rotation centers and the target 31 can be measured.
In addition, since the distance of the translation mechanism 14 necessary for estimating the angle used for the calculation can be increased, even when the absolute distance L between the rotation center of the laser interferometer 13 and the target 31 is long, it is highly accurate. The absolute distance L can be measured.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications and the like within a scope that can achieve the object of the present invention are included in the present invention.
For example, the translation mechanism 14 that is a support mechanism is not limited to the one using a device such as a linear stage, and may include another drive mechanism, a guide mechanism, and a position measurement mechanism, or the drive mechanism may be It may be manual.
Further, the support mechanism is not limited to a mechanism that moves along a continuous guide mechanism such as the translation mechanism 14, and for example, a plurality of holding mechanisms are arranged along the measurement axis, and one of the holding mechanisms is selected. The rotation mechanisms 11 and 12 and the laser interferometer 13 may be configured to take the first position and the second position.

  INDUSTRIAL APPLICABILITY The present invention can be used for a method for measuring the absolute distance between targets of a tracking laser interference measuring apparatus and a tracking laser interference measuring apparatus.

DESCRIPTION OF SYMBOLS 10 ... Tracking type laser interference measuring apparatus 11, 12 ... Rotation mechanism which is a biaxial rotation mechanism 13 ... Laser interferometer 14 ... Translation mechanism 20/21 ... Laser beam 30 ... Head 31 ... Target 32 ... Table

Claims (4)

A laser interferometer that irradiates a target with laser light, a biaxial rotating mechanism that changes the emission direction of the laser interferometer, and a tracking laser interference that controls the biaxial rotating mechanism and tracks the target with the laser interferometer A method for measuring an absolute distance between targets of a measuring device,
A first position and a second position where the laser interferometer can be disposed are provided on the same measurement axis,
Fixing the target at a position away from the measurement axis;
Placing the laser interferometer in a first position, capturing the target with laser light in the first position;
Moving the laser interferometer to a second position, capturing the target with a laser beam in the second position;
Performing a geometric operation on a triangle with the target fixed position, the first position and the second position as vertices;
An absolute distance measurement method between targets of a tracking type laser interference measuring apparatus, wherein an absolute distance between the laser interferometer at the first position and the target is measured. In the absolute distance measurement method between targets of the tracking type laser interference measuring device according to claim 1,
Providing a third position different from the first position and the second position on the measurement axis;
After capturing the target with laser light at the second position, the laser interferometer is moved to a third position, and the target is captured with laser light at the third position;
Geometries for triangles with the fixed position of the target, the first position and the second position as vertices and the triangles with the fixed position of the target, the first position and the third position as vertices A method for measuring an absolute distance between targets of a tracking type laser interference measuring apparatus characterized by performing a mathematical operation.   Tracking that includes a laser interferometer that irradiates a target with laser light and a biaxial rotating mechanism that changes the emission direction of the laser interferometer, and controls the biaxial rotating mechanism to track the target with the laser interferometer A laser interferometer, which has a support mechanism capable of supporting the laser interferometer and the biaxial rotation mechanism at a first position and a second position on the same measurement axis. Interference measurement device. In the tracking type laser interference measuring apparatus according to claim 3,
A tracking type laser interference measuring apparatus comprising a guide rail extending along the measurement axis, wherein the laser interferometer is guided by the guide rail and is movable on the measurement axis.