JPH02297010A - Length measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a length measuring device that can be used in general equipment that requires dimensional information, such as NC machine tools, machining centers, and other machine tools, as well as electron beam lithography devices. .

(Prior Art) Length measuring devices have been used in various fields where dimensional information is required, including length measurement of workpieces in machine tools.

Since various measurement errors occur during measurement, it is necessary to remove such errors in order to perform highly accurate measurements. Errors caused by measurements that violate Abbe's principle are one of them, and cause geometric errors.

The Atsube principle will be explained using FIGS. 6 and 7.

In FIG. 6, 601 is an object to be measured, and 602 is a standard scale, which are arranged on the same straight line.

603 and 604 are moving parts that move while keeping the relative distance at a constant value E. In the example shown in this figure, the moving unit 603 functions as a probe that comes into contact with the measurement point of the object to be measured.
04 has a function as a scale reader for the standard scale 602. The straight line connecting the moving parts 603 and 604 is at a small angle e with respect to the straight line connecting the workpiece 601 and the standard scale 602 due to the inclination of the table on which the workpiece 601 is placed.
Assume that the slope is only slanted.

In this case, the original measurement should be performed by the moving unit 605 shown by the broken line, but due to the inclination of the table, etc., the measurement is actually performed by the moving unit 604. Therefore, the measured value L2 has a measurement error of ΔL with respect to the true length Ll.

Here, it is expressed as ΔL=E(1−cosθ)=Ee2. Since e is a minute angle, ΔL is an extremely small value and can be ignored. Therefore, in measurements based on the above-mentioned Atsube's principle, errors that would affect the measured values do not occur.

On the other hand, if measurements are made that violate Atsube's principle, errors that cannot be ignored will occur. This will be explained with reference to FIG.

In FIG. 7, an object to be measured 601 and a standard measure 602 are arranged in parallel with a distance A between them. 603 and 604 are the object to be measured 601 and the standard measure 60 while keeping the relative distance at a constant value.
This is a moving part that moves along 2. In the example shown in this figure, the moving section 603 has a function as a probe that comes into contact with a measuring point of the object to be measured, and the moving section 604 has a function as a scale reader. Originally, the straight line connecting the moving parts 603 and 604 should be perpendicular to the standard scale 602, but
Due to the inclination of the table on which 01 is placed, etc., the object to be measured 6
01, it is assumed that the standard scale 602 is inclined by a minute angle of 0 with respect to the straight line connecting it.

In this case, although the original measurement should be performed by the moving unit 605 indicated by the broken line, the measurement is actually performed by the moving unit 604. Therefore, the measured value L2 has a measurement error of ΔL with respect to the true length Ll. Here, ΔL,
, AO, which results in a measurement error that cannot be ignored.

Therefore, in order to reduce measurement errors, the geometrical arrangement shown in FIG. 6, which follows Atsube's principle, is required instead of the arrangement shown in FIG. 7.

(Problems to be Solved by the Invention) However, if the object to be measured 601 and the standard measure 602 are arranged in a straight line as shown in FIG. In the case of measurement, there was a problem in that the measurement equipment was extremely large-scale.

Furthermore, if the measurement point on the object to be measured 601 and the corresponding measurement point on the standard scale 602 are far apart, and the ambient temperature is not uniform, the distance between them will vary depending on the location due to temperature fluctuations, causing measurement errors. There were also problems.

In order to eliminate these measurement errors, there is a length measuring device that removes the errors by multiplying the measured value by a predetermined correction coefficient. There was a problem in which it was difficult to deal with fluctuations because the fluctuation values were not constant.The present invention was created in view of the above problems, and uses a geometric arrangement that goes against Atsube's principle, and also reduces measurement errors caused by this. The purpose of the present invention is to provide a length measuring device that eliminates the influence of

(Means for Solving the Problems) The length measuring device of the present invention includes a moving part that moves on first and second axes parallel to the measurement axis, and a moving part that moves on the first and second axes. a detection unit that detects the amount of movement; and a calculation unit that uses the output signal of the detection unit to calculate the amount of movement of the detection unit on the measurement axis based on the distance between the measurement axis, a first axis, and a second axis. It is equipped with

(Function) By calculating the output signal of the detection unit corresponding to the amount of movement of the moving unit on the first and second axes using the measurement axis and the distance between the first and second axes, the Calculate the amount of movement of the detection unit.

(Example) FIG. 5 is a diagram showing the principle of the present invention.

In FIG. 5, an object to be measured 501 is placed parallel to the measurement axis, and a first standard 502 and a second standard 503 are each placed parallel to the measurement axis. Object to be measured 501
and the first standard scale 502 is the distance A, the first standard scale 502 and the second standard scale
The standard scales 503 are placed at a distance B.

Moreover, the moving parts 504, 505, and 506 are arranged on a straight line, and move in the measurement axis direction while maintaining this linear relationship.

The moving unit 504 functions as a probe, and the moving unit 505 functions as a probe.
．． 506 has a function as a scale reader. The moving unit 504 moves on the measurement axis. In an ideal state, the straight line connecting the moving parts 504.505.506 is perpendicular to the measurement axis, so the moving parts 505.506 are connected to the broken line 507.
Although it is located at position 508, it is actually at a position tilted by a minute angle of 0 due to the influence of the tilt of the table.

In this state, if the lengths measured by the moving parts 505 and 506 are L2 and La, respectively, then the object to be measured 5
Regarding the true length Ll of 01, the following relationship holds true: L1=L2+ΔL2 (1). Here, ΔL2=A-sinθ=A・(L2-La)/B (2
) can be expressed as

Therefore, from equations (1) and (2), the true length Ll is
l = L2 + A・(L2 La)/B=(1+
N [F])・L2- A-La7B (3
) is required.

Also, in equation (3), if A=H is set, Ll = 2L2- La
(4), and in the case of a laser interferometric length measuring device to be described later, measurement can be performed without special calculations.

FIG. 1 is a diagram showing a first embodiment of the present invention.

In FIG. 1, reference numerals 101, 102, and 103 are corner cubes, and the corner cubes 102 and 103 are arranged within the moving section 104 at a constant distance A.

The corner cube 103 is spaced a distance A from the measurement axis on which the object to be measured is placed. corner cube 102.1
03 acts as a moving part that moves parallel to the measurement axis. 1
05 is a polarizing beam splitter, which transmits one side of mutually polarized incident light at 90 degrees and reflects the other side. 106 is a quarter wavelength plate that polarizes the incident light by 45 degrees and outputs the polarized light. Further, 107 is a plane mirror.

The operation of the apparatus shown in FIG. 1 will be explained below.

In addition, in the figure, for convenience of explanation, solid lines and broken lines are used to make it appear as if the output is from two light sources, but in reality, the output is from a single light source, and the solid and broken lines are partially drawn. They overlap.

Laser light from a laser light source (not shown) enters polarizing beam splitter 105 . One polarized component light of the incident light passes through the polarization beam splitter 105 as measurement system light, and is polarized by 45 degrees by the quarter-wave plate 106, as shown by the solid line. After this polarized light is reflected by the corner cube 103, the quarter-wave plate 1
Polarized beam splitter 1
It is incident on 05. Since the light incident on the polarizing beam splitter 105 is polarized by a total of 90 degrees by the quarter-wave plate 106, it is reflected and incident on the corner cube 101. The light reflected by the corner cube 101 is reflected by the polarizing beam splitter 105, and then polarized at 45 degrees by the quarter-wave plate 106 again.
Reflection by corner cube 103, quarter wave plate 1
Polarizing beam splitter 1 through 45 degree polarization by 06
It is incident on 05. At this time, since the incident light from the laser light source passes through the quarter-wave plate 106 a total of four times,
The polarizing beam splitter 1
Pass through 05. This light is detected as output light by a photodetector (not shown).

On the other hand, the other polarized component light of the light incident on the polarizing beam splitter 105 from the laser light source is reflected as a reference system light as shown by the broken line, is reflected by the plane mirror 107 and the corner cube 102, and then is reflected by the plane mirror 107 again. reflected. The light reflected by plane mirror 107 is reflected by polarizing beam splitter 105 and detected by a photodetector.

As described above, the optical path lengths of the measurement system light and reference system light are calculated using the arrival time difference between the measurement system light and the reference system light detected by the detector, and the calculation process is performed in the calculation section based on equation (3). Then Ll is obtained.

In the case of this example, A=B, and the measurement system light makes two round trips and the reference system light makes one round trip, so the true measured value Ll (= 2L2-
La) is obtained.

FIG. 2 shows a second embodiment of the invention. The same parts as in FIG. 1 are given the same reference numerals. The difference from Figure 1 is that
The point is that a corner cube 201 and a plane mirror 202 are provided. By providing these, the optical path between the polarizing beam splitter 105 and the corner cube 102 and the optical path between the polarizing beam splitter 105 and the corner cube 103 are doubled compared to those in FIG. 1, improving measurement resolution. becomes possible. Measured values are obtained in the same manner as in FIG.

FIG. 3 shows a third embodiment of the invention. Figures 1 and 2
The same parts as those in the figure are given the same reference numerals. Figures 1 and 2
The difference from the diagram is that a corner cube 301, a polarizing beam splitter 302, and a quarter wavelength plate 303 are provided, as well as a plane mirror 304 as a moving part.

The measurement light indicated by the solid line is the polarizing beam splitter 105.4.
Quarter-wave plate 106, plane mirror 304, polarizing beam splitter 105, corner cube 101, quarter-wave plate 106, plane mirror 304, quarter-wave plate 106, polarizing beam splitter 105, plane mirror 202, corner cube 201, Polarizing beam splitter 105. Quarter wavelength plate 106, plane mirror 304. Quarter wavelength plate 106, polarizing beam splitter 105, corner cube 101, polarizing beam splitter 105. Quarter wavelength plate 106, plane mirror 304.4 The light passes through or is reflected in the order of the half-wave plate 106 and the polarizing beam splitter 105 and is output.

On the other hand, the reference light indicated by the broken line is the polarizing beam splitter 10.
5. Polarizing beam splitter 302. Quarter wavelength plate 30
3. Plane mirror 304. Quarter wavelength plate 303, polarizing beam splitter 302, corner cube 301, polarizing beam splitter 302. Quarter wavelength plate 303, plane mirror 3
04. Quarter wavelength plate 303, polarizing beam splitter 3
021, and the polarizing beam splitter 105, and are output after being passed through or reflected in this order.

Therefore, the optical path length can be increased and the measurement resolution can be improved. Note that the measured values are obtained in the same manner as in the case of FIG.

Although the above description has been made using an example of a laser interferometric length measuring device, the present invention can be similarly applied using a well-known digital scale such as an optical length measuring device or a magnetic length measuring device that utilizes moiré fringes.

FIG. 4 is a schematic diagram of a measuring device using a digital scale.

In FIG. 4, a movable part 403 movable in two directions is provided at the top of a measuring device main body 401.

A probe 402 is provided at the tip of the movable portion 403, and a detector 405 is provided at the base thereof.

The detector 405 and the main scale 404 provided on the measuring device main body 401 constitute a length measuring device that measures the amount of movement of the probe 402 in two axial directions.

On the other hand, a table 406 movable in the X direction, a moving part 408 connected to the table 406 and movable in the X direction, and a scale 407.
9 is provided. The distance between scales 407 and 409 is set to a predetermined value (B above).

When performing measurement using the measuring device configured as described above, first place the object to be measured (not shown) on the table 406, and move the movable part 403 downward until the probe 402 comes into contact with the object. probe 402 and scale 4.
07 Which distance A is measured? Next, set the table 406 to
direction to bring the probe 402 into contact with a desired measurement point on the object to be measured. The line along which the probe 402 moves relative to the table 406 is the measurement axis. At this time, the moving unit 408 moves together with the table 406, and the moving distances L2 and L3 are measured.

Based on the above measured values and known values, the length of the object to be measured is determined from the above equation (3) or equation (4).

In addition, when using a laser interferometric length measuring device, the moving unit 408 and scales 407 and 409 are
It can be replaced with the length measuring device shown in the figure.

At this time, the distance between the measurement optical path system and the reference optical path system corresponds to the distance B.

(Effect) By calculating the output signal of the detection unit corresponding to the amount of movement of the moving unit on the first and second axes using the measurement axis and the distance between the first and second axes, the Since the amount of movement of the detection unit is calculated, measurement errors that violate the principle of error do not occur, and highly accurate measurement is possible.

[Brief explanation of the drawing]

1 to 3 show first to third embodiments of the present invention, respectively;
FIG. 4 is a schematic diagram of a measuring device using the present invention, FIG. 5 is a diagram of the principle of the present invention, and FIGS. 6 and 7 are explanatory diagrams of Atsube's principle.

Claims (2)

[Claims] (1) a moving part that moves on first and second axes parallel to the measurement axis; a detection part that detects the amount of movement of the moving part on the first and second axes; and the measurement axis, the first A length measuring device comprising: a calculation unit that calculates the amount of movement of the moving unit on the measurement axis by calculating the output signal of the detection unit based on the distance between the axis and the second axis. (2) The length measuring device according to claim 1, further comprising a length measuring device that measures the distance between the first axis and the second axis.