JP2003194523A - Length measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a length measuring apparatus that can easily measure the length of an object to be measured with high accuracy in a short time. <P>SOLUTION: This length measuring apparatus measures the distance between the facing end faces 128a and 128b of the object 128 to be measured having an already known preliminary value. This apparatus is provided with first and second interfering means 144 and 150 having optical axes matched to the length measuring axis of the object 128 and arranged with a prescribed separating distance in between, and first and second observing means 148 and 154 which can observe the phase difference between interference light rays formed by the interfering means 144 and 150. This apparatus simultaneously performs the observation of reference and measuring interference fringes by means of the first observing means 148 and the observation of the reference and measuring interference fringes by means of the second observing means 154, and finds the distance between the end faces 128a and 128b of the object 128 based on the phase differences between the interference fringes observed by means of the observing means 148 and 154 and the preliminary value between the end faces 128a and 128b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a length measuring device, and more particularly to an improvement in the arrangement of optical system components of a length measuring device using a non-contact optical wave interferometer.

[0002]

2. Description of the Related Art Conventionally, end gauges such as block gauges are standard instruments with high accuracy used as a standard for measuring length, and when several pieces are closely attached to each other, for example, 1-1.
Since it is possible to create arbitrary dimensions in units of 0 μm,
For example, it is widely used as a length standard for factories.

For inspection of such a highly accurate gauge,
Higher precision is required, and for example, dimensions can be measured with high resolution and in a non-contact manner, and therefore, a length measuring device using a light wave interferometer is widely used. This is the phase of the fringes (fractional)
Must be obtained with high accuracy.

For this reason, conventionally, one end surface of the block gauge is first brought into close contact with the base plate surface, that is, ringing is performed. This is inserted into one optical path of the Michelson interferometer, and the light reflected by the other end of the block gauge and the surface of the base plate is superposed on the reference light to cause interference, and each interference fringe is observed. Then, from the phase difference of each interference fringe and the preliminary value between the opposite end faces of the block gauge,
I was measuring the dimensions of the block gauge.

However, if there is variation in this ringing, it causes a large error, and it is very troublesome to perform ringing without variation because it requires a highly skilled technique. For this reason, recently, attention has been paid to length measurement using a non-contact optical wave interferometer that can perform length measurement without using such ringing (Japanese Patent Application Laid-Open No. 8-271216).
Etc.).

FIG. 1 shows a length measuring apparatus using a general non-contact optical wave interferometer. That is, the length measuring device 10 shown in FIG.
Collimates the laser light from the light source 12 with the lens 14 to a required size. The laser light 15 is directed to the half mirror 16, and is divided by the half mirror 16 into laser light directed to the reference mirror 18 and laser light directed to the annular interferometer 20.

The laser light directed to the annular interferometer 20 is further divided into two by the half mirror 22. A part of this laser light is reflected by the reflection mirror 24 and the first shutter 2.
After being reflected at one end of the block gauge 28 via 6, the optical path returns to the same optical path as the outgoing direction. Alternatively, after the light is reflected by the other end of the block gauge 28 via the reflection mirror 30 and the second shutter 32, the same optical path as the going back is returned.

Further, the laser light passing through the side of the block gauge 28 returns to the half mirror 16 again. The half mirror 16 causes the laser light from the annular interferometer 20 and the laser light reflected by the reference mirror 18 to overlap and interfere with each other, and the interference light is observed as interference fringes on the screen 26.

Then, the size of the block gauge 28 is obtained based on the preliminary value between the opposite end faces of the block gauge and each phase difference (fractional number) of the interference fringes observed on the screen 26. The dimension L _B between the opposite end faces of the block gauge 28 can be expressed by the following mathematical formula.

L _B = (1/2) (2L ₃ −L ₂ −L ₁ ) = (λ / 2) {2N ₃ −N ₂ −N ₁ + (ε ₃ −ε ₂ ) + (ε ₃ − epsilon _1)} However, _{L 1:} half-mirror 22-first reflecting mirror 24 gauge block 28 back and forth optical path length of the end _{L 2:} reciprocating optical path length of the half mirror 22-second reflector 30- gauge block 28 and the other end L ₃ : Half mirror 22-first reflecting mirror 24-gauge 28
Side-second reflecting mirror 30-optical path length L ₁ of the half mirror 22: λ (N ₁ + ε ₁ ) L ₂ : λ (N ₂ + ε ₂ ) L ₃ : λ (N ₃ + ε ₃ ) λ: laser light 15 wavelength N _i: the natural number of the quotient when the optical path length L _i divided by the wavelength λ of the coherent light epsilon _i: fraction of the quotient when the optical path length L _i divided by the wavelength λ of the coherent light (phase)

Then, the phase differences (ε ₃ −ε ₂ ) and (ε
_The shutters 26 and 32 play a role of blocking the laser light 15 having the same area as the measurement surface of the block gauge 28 when measuring ( _3- ε ₁ ), and when measuring the phase difference (ε ₃ -ε ₂ ). , The first shutter 26 is closed and the second shutter 32 is opened.

On the other hand, when measuring the phase difference (ε ₃ −ε ₁ ), the first shutter 26 is opened and the second shutter 32 is closed. By switching the shutters 26 and 32 as described above, the phase difference (ε ₃ −ε ₂ ) and (ε ₃ −ε ₁ ) can be measured by 2 times.
Divide into times. Then, the dimension between the opposite end faces of the block cage 28 is obtained based on the preliminary value between the opposite end faces of the block gauge and each measured phase difference.

In the length measuring device 10 using such a non-contact optical wave interferometer, since it is not necessary to perform ringing, it is possible to eliminate a large error factor due to the variation of the ringing.

[0013]

However, even in the length measuring device using the non-contact optical wave interferometer as described above,
The measurement of one end and the measurement of the other end in the length measurement direction of the object to be measured must be performed twice by switching the shutter.

Therefore, if the non-contact optical wave interferometer as described above is used, the measuring time is long and the work is troublesome. Therefore, the measuring time, the workability and the observation of both sides of the object to be measured are performed. Since there is a time lag, there was room for improvement in being affected by the environmental changes that occurred during that time.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to provide a length measuring apparatus using a non-contact optical wave interferometer, which enables highly accurate length measurement in a short time and easily. Especially.

[0016]

In order to achieve the above object, a length measuring apparatus according to the present invention is a length measuring apparatus for measuring a dimension between opposed end faces of an object to be measured whose preliminary value is known. A first interference means and a second interference means, which have an optical axis that coincides with the length measurement axis of the object to be measured and are arranged at a predetermined separation distance, and the positions of the interference lights formed by the respective interference means. The first observation means and the second observation means capable of observing the phase difference are provided.

The first interfering means emits coherent light having a predetermined beam diameter and wavelength in the measuring direction of the object to be measured, and part of the coherent light is incident on one end of the object to be measured. The reflected light is returned, and the rest is passed by the side of the object to be measured and is incident on the second interference means.

The second interference means emits coherent light having the same beam diameter and wavelength as the coherent light in the measuring direction of the object to be measured, and part of the coherent light is directed to the other end of the object to be measured. The reflected light is made incident and returned, and the rest is made to pass through the side of the object to be measured and made incident on the first interference means.

The first interfering means obtains a reference interfering light by superposing the coherent light from the second interfering means which has passed by the side of the object to be measured and the first reference light which is the coherent light. ,
Further, the reflected light obtained by irradiating the one end of the object to be measured with the coherent light from the first interference means and the first reference light which is the coherent light are superposed to obtain the measured coherent light.

The second interference means obtains standard interference light by superimposing the coherent light from the first interference means and the second reference light, which is coherent light, which has passed by the side of the object to be measured. ,
Further, the reflected light obtained by irradiating the other end of the object to be measured with the coherent light from the second interference means and the second reference light, which is the coherent light, are superposed to obtain the measured coherent light.

The first observing means simultaneously observes the reference interference light and the measurement interference light obtained by the first interference means as interference fringes. The second observation means observes the reference interference light and the measurement interference light obtained by the second interference means as interference fringes simultaneously with the observation by the first observation means.

Then, the preliminary value between the end faces of the object to be measured facing each other, the phase difference between the reference interference fringes and the measurement interference fringes observed by the first observing means, and the second observing means are observed. It is characterized in that the dimension between the facing end faces of the object to be measured is obtained based on the phase difference between the reference interference fringes and the measured interference fringes.

Examples of the object to be measured used in the present invention include end gauges such as block gauges whose rough preliminary values are known.

In the present invention, one light irradiation means and one light splitting means are provided, and the one light irradiation means,
It is preferable that the first interfering means and the second interfering means constitute an annular interferometer.

Here, the light irradiation means emits coherent light having the predetermined beam diameter and the predetermined wavelength.

The light splitting means splits the coherent light from the light irradiating means into two, one split light is made incident on the first interference means, and the other split light is made to enter the second interference means. Make it incident.

Further, in the present invention, the optical path length from the light splitting means to the first interference means, one end of the object to be measured, and the first interference means is set to L ₁ , and the light splitting means to the second The interference means, the optical path length to the first interference means is L
₂ , the optical path length from the light splitting means to the second interference means, the other end of the object to be measured, and the second interference means is L ₃ , and the light splitting means to the first interference means and the second Assuming that the optical path length to the interference means is L ₄ , the dimension L _B between the facing end faces of the measured object can be expressed by the following mathematical formula.

L _B = λ / 2 {N ₄ −N ₃ + N ₂ −N ₁ + (ε
₄ −ε ₃ ) + (ε ₂ −ε ₁ )} where L ₁ : λ (N ₁ + ε ₁ ) L ₂ : λ (N ₂ + ε ₂ ) L ₃ : λ (N ₃ + ε ₃ ) L ₄ : λ (N ₄ + ε ₄ ) λ: wavelength N _{i of the} coherent light (i = 1 to 4): natural number ε _i (i = 1) of the quotient when the optical path length Li is divided by the wavelength λ of the coherent light 4): Fraction (phase) of the quotient when the optical path length Li is divided by the wavelength λ of the coherent light (ε ₂ −ε ₁ ): reference interference fringes observed by the first observation means and measurement interference Phase difference with fringe (ε ₄ −ε ₃ ): Phase difference between the reference interference fringe and the measurement interference fringe observed by the second observing means Further, in the present invention, a reading means and a computing means are provided. Is preferred.

Here, the reading means reads the phase difference of the interference fringes observed by each of the observing means.

The calculating means opposes the object to be measured based on the phase difference between the interference fringes obtained by the reading means and the preliminary value between the end faces of the object to be measured. Find the dimension between the end faces.

Further, in the present invention, the light source is
It is also preferable to emit a plurality of optical interference lights having different wavelengths and to provide an optical axis correcting means.

Here, the optical axis correction means is provided on the optical axis between the light splitting means and the interference means, and corrects the deviation of the optical axis according to the wavelength of the coherent light.

The optical interference light of a plurality of different wavelengths referred to herein includes, for example, laser light obtained by switching a plurality of lasers of different wavelengths, laser light obtained by changing the wavelength of a multi-wavelength laser, and the like.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a schematic configuration of a length measuring device according to an embodiment of the present invention.
In the present embodiment, an example will be described in which an end prototyping device such as a block gauge having a rectangular cross section is assumed as an object to be measured, and a dimension between opposing end surfaces of a block gauge having a known preliminary value is measured. Reference numeral 1 is given to a portion corresponding to the prior art.
00 is added and description is omitted.

The length measuring apparatus 110 shown in the figure has one light irradiation means 140 and a first half mirror (light splitting means) 142.
And a second half mirror (first interference means) 144 and a third half mirror that have an optical axis that coincides with the length measurement axis of the block gauge (measurement object) 128 and that are arranged at a predetermined distance. (Second interference means) 150 is provided.

A first screen (first observing means) 148 capable of observing the phase difference of the interference light formed by the second half mirror 144 and the third half mirror 150.
And a second screen (second observation means) 154.

Further, as shown in the figure, a first reference mirror (first interference means) 146 and a second reference mirror (second interference means) 1
52 is provided as an optical system constituent member.

As described above, by the first half mirror 142, the second half mirror 144, and the third half mirror 150,
An annular interferometer 120 is configured.

The light irradiation means includes a single wavelength laser (light source) 112, a collimator lens 114, and a reflecting mirror 15.
6 is provided. Then, the laser light (coherent light) having a predetermined wavelength λ emitted from the laser 112 is transmitted to the lens 11
The laser beam 115 is collimated to a required beam diameter by 4 and is incident on the first half mirror 142 as a laser beam 115 via a reflecting mirror 156.

The size of the beam diameter of the laser beam 115 is such that a part of the beam is incident on the end of the block gauge 128 and the rest passes through the side of the block gauge 128, and the second half mirror. It is larger than the measurement end surface of the block gauge 128 so that it can be incident on the 144 or the third half mirror 150.

The first half mirror 142 is a reflecting mirror 156.
The laser light 115 from is divided into a clockwise optical path and a counterclockwise optical path in the figure, and the respective divided lights are made incident on the interferometer 120 constructed in a ring shape.

That is, one split light is made incident on the second half mirror 144, and the other split light is made incident on the third half mirror 150.

The second half mirror 144 splits the laser light 115 from the first half mirror 142 into two,
One of them is emitted toward the right side in the drawing in the length measuring direction of the block gauge 128, and the other is incident on the first reference mirror 146. Block gauge 12 by the second half mirror 144
A part of the light emitted toward the right side in the drawing in the length measurement direction of 8 is incident on the left end surface 128 a of the block gauge 128. The remaining light is the one end 12 of the block gauge 128.
The light does not enter 8a, passes through the side thereof, and enters the third half mirror 150.

On the other hand, the other split light split by the first half mirror 142 enters the third half mirror 150. The third half mirror 150 divides the laser beam 115 from the first half mirror 142 into two, irradiates one of them to the left side in the drawing in the length measuring direction of the block gauge 128, and refers to the other of the two. It is incident on the mirror 152. A part of the light emitted toward the left side of the block gauge 128 in the drawing by the third half mirror 150 is part of the block gauge 12
8 is incident on the right end surface 128b. The remaining light passes through the right end surface 128b of the block gauge 128 without passing through it, and enters the second half mirror 144.
Then, on the first screen 148, the phase difference (ε ₂
−ε ₁ ) is observed.

That is, the light emitted toward the first reference mirror 146 by the second half mirror 144 is reflected by the first reference mirror 146 and returns to the second half mirror 144 again.

Therefore, in the second half mirror 144,
The laser beam (optical path L ₂ ) from the third half mirror 150 that has passed by the block gauge 128 and the first reference mirror 1
The laser light (first reference light) from 46 is overlapped and interfered. This first reference interference light is transmitted to the first screen 14
8 is observed as the first reference interference fringe. At the same time as this observation, the second half mirror 144 causes the second half mirror 144 to move the left end surface 128a of the block gauge 128.
The light (optical path L ₁ ) that is emitted toward the laser beam, is reflected by the left end surface 128a, and returns to the second half mirror 144 again, and the laser light (first reference light) from the first reference mirror 146 is superimposed. To interfere. The first measurement interference light is incident on the first screen 148 and is observed on the first screen 148 as first measurement interference fringes at the same time as the first reference interference fringes.

On the other hand, on the second screen 154, the phase difference (ε ₄ −ε ₃ ) is observed.

That is, the light emitted toward the second reference mirror 152 by the third half mirror 150 is reflected by the second reference mirror 152 and returns to the third half mirror 150 again.

Therefore, in the third half mirror 150,
The laser beam (optical path L ₄ ) from the second half mirror 144 that has passed by the side of the block gauge 128 and the second reference mirror 1
The reflected light (second reference light) from 52 is superimposed and interfered. The second reference interference light is incident on the second screen 154 and is observed on the second screen 154 as second reference interference fringes. At the same time as this observation, in the third half mirror 150, the light emitted toward the right end surface 128b of the block gauge 128 by the third half mirror 150, reflected by the right end surface 128b, and returned to the third half mirror 150 again. The (optical path L ₃ ) and the laser light (second reference light) from the second reference mirror 152 are superposed and interfered with each other. The second measurement interference light is incident on the second screen 154 and is observed on the second screen 154 as second measurement interference fringes at the same time as the second reference interference fringes.

As described above, in this embodiment, by arranging the respective optical system constituent members as described above, the reference interference fringes and the measurement interference fringes on the first screen 148 are observed and the reference interference fringes on the second screen 154 are observed. The interference fringes and the measurement interference fringes are observed at the same time.

By the way, in the conventional length measuring apparatus using the non-contact optical wave interferometer, it is necessary to perform the measurement of the left end face and the right end face of the block gauge in the length-measuring direction separately by switching the shutter. . However, if the measurement is performed twice in this way, the measurement takes time and is troublesome. Especially when measuring at different wavelengths,
This problem was particularly serious.

On the other hand, in the present embodiment, as described above, the interference fringes on the left end face 128a of the block gauge 128 are measured at one of the subsequent stages of the first half mirror 142.
A second half mirror 144, a first reference mirror 146, and a first screen 148 are provided. On the other side, a third half mirror 150, a second reference mirror 152, and a second screen 154 for measuring the interference fringes of the right end surface 128b of the block gauge 128 are provided.

Therefore, in this embodiment, the observation of the interference fringes on the first screen 148 and the observation of the interference fringes on the second screen 154 can be carried out simultaneously, so that the conventional non-contact optical wave interferometer is used. The number of measurements can be significantly reduced compared to a length measuring device. As a result, although ringing is not required and the accuracy is high, it is possible to significantly reduce the measurement time and improve the operability, which was extremely difficult with the conventional length measuring device using the non-contact interferometer. .

By observing both sides simultaneously,
The results measured on both sides are based on the same environment, and high-precision measurement can be performed without being affected by environmental changes during measurement.

Further, in the conventional length measuring device using the non-contact optical wave interferometer, it is impossible to prevent the interference between the clockwise light and the counterclockwise light of the annular interferometer due to a problem in the structure of the optical system. , Each measurement may not be performed properly. On the other hand, in the present embodiment, in the measurement of the clockwise light and the counterclockwise light of the annular interferometer, since the first interfering means and the second interfering means are completely separated, the interference of these lights Does not matter. As a result, the measurement can be performed more appropriately.

The size of the block gauge 128 will be described below based on the preliminary value of the block gauge and the interference fringes on the first screen and the second fringe observed on the same time period as described above. A method of obtaining L _B will be described.

That is, in this embodiment, the first reading means 170 is provided at the subsequent stage of the first screen 148. Then, the first reading unit 170 causes the first reference interference fringes 18 observed on the first screen 148 as shown in FIG.
4 and the first measurement interference fringe 186, the phase difference (b ₁ / a) is read, and the read result is the calculation means 1 of the computer 172.
The phase difference information (ε ₂ −ε ₁ ) is input to the measurement data storage unit 176.

Further, in this embodiment, the second screen 1
A second reading unit 178 is provided after 54. Then, the second reading unit 178 causes the second reference interference fringes 188 observed on the second screen 154 as shown in FIG.
And the phase difference (b ₂ / a) between the second measurement interference fringe 190 are read at the same time. The read result is input to the calculating means 174,
It is stored in the measurement data storage unit 176 as the phase difference information (ε ₄ −ε ₃ ) information.

Further, in this embodiment, the computer 17
2 includes a calculation information storage unit 180, which stores in advance information on the preliminary value of the block gauge, a program for performing the matching method described later, and the like. For example, the optical path length between the first half mirror 142 and the second half mirror 144 is a, the optical path length between the second half mirror 144 and the left end surface 128a of the block gauge 128 is b, the first half mirror 142 and the third half mirror 150. The optical path length between them is c, and the optical path length between the third half mirror 150 and the right end surface 128b of the block gauge 128 is d.

Then, the calculating means 174 stores information such as the preliminary value of the block gauge stored in the calculation information storage unit 180 and the phase difference information (ε ₄ −ε) stored in the measurement data storage unit 176. ₃ ) and (ε ₂ −ε ₁ ), the dimension L _B between the end faces of the block gauge 128 that face each other in the lengthwise direction is determined by using, for example, the matching method as follows.

That is, the optical path length between the first half mirror 142 and the second half mirror 144 is a, the optical path length between the second half mirror 144 and the left end face 128a of the block gauge 128 is b, and the first half mirror 142 and the first half mirror 142 are Letting c be the optical path length between the three half mirrors 150 and d be the optical path length between the third half mirror 150 and the right end surface 128b of the block gauge 128, the optical path lengths L _{1 to} L ₄ can be expressed as follows.

L ₁ = a + 2b (1) L ₂ = b + c + d + L _B (2) L ₃ = c + 2d (3) L ₄ = a + b + d + L _B (4) From the above formulas 1 and 2, L ₂ -L ₁ = ( b + c + d + L _B ) − (a + 2b) (5) From the above formulas 3 and 4, L ₄ −L ₃ = (a + b + d + L _B ) − (c + 2d) (6) From the above formulas 5 and 6, L ₂ −L ₁ + L ₄ −L _{3 = (a + 2b + c} + 2d + 2L B) - (a + 2b + c + 2d) = 2L B ... (7)

When this is deformed, the block gauge 128
Of the left end surface 128a and the right end surface 128 which face each other in the length measuring direction
The dimension L _B between b can be expressed by the following mathematical formula. L _B = 1/2 {(L ₂ −L ₁ ) + (L ₄ −L ₃ )} (8) where L ₁ : the first half mirror 142 to the second half mirror 144, the left end surface of the block gauge 128. 128
a, optical path L ₂ to second half mirror 144: first half mirror 142 to third half mirror 1
50, beside block gauge 128, second half mirror 1
Optical path L ₃ up to 44: first half mirror 142 to third half mirror 1
50, the right end surface 128b of the block gauge 128, the optical path _{L 4} to the third half mirror 150: second half mirror 1 from the first half mirror 142
44, beside block gauge 128, third half mirror 1
Optical path up to 50

Therefore, the optical paths L ₁ , L ₂ , L ₃ ,
The optical path length of L ₄ can be expressed by the following formula. L ₁ = λ (N ₁ + ε ₁ ) ... (9) L ₂ = λ (N ₂ + ε ₂ ) ... (10) L ₃ = λ (N ₃ + ε ₃ ) ... (11) L ₄ = λ (N ₄ + ε) ₄ ) (12) where λ: wavelengths N _{1 to} N ₄ of the laser light: natural numbers of quotients ε _{1 to} ε ₄ when dividing each optical path length L _i by the wavelength λ: each optical path length L _i Is the fraction (phase) of the quotient when λ is divided by the wavelength λ (ε ₂ −ε ₁ ): The shift (b ₁ / b ₁ ) of each interference fringe observed on the first screen 148 stored in the measurement data storage unit. Phase difference information (ε ₄ −ε ₃ ) obtained from a): deviation of each interference fringe observed on the second screen 154 (b ₂ stored in the measurement data storage unit)
/ A) Phase difference information obtained from

By substituting the expressions 9 to 12 into the expression 8, the following expression can be obtained. _{L B = (1/2) · (} L 4 -L 3 + L 2 -L 1) = (1/2) · {λ (N 4 + ε 4) -λ (N 3 + ε 3) + λ (N 2 + ε 2 ) −λ (N ₁ + ε ₁ )} = (λ / 2) · {N ₄ −N ₃ + N ₂ −N ₁ + (ε ₄ −ε ₃ ) + (ε ₂ −ε ₁ )} (13)

Therefore, the size L _B of the block gauge 128 is determined by the phase difference information (ε ₂ −ε ₁ ) obtained from each interference fringe observed on the first screen 148 and each interference observed on the second screen 154. The phase difference information (ε ₄ −ε ₃ ) obtained from the stripes, the known measurement wavelength λ, and the preliminary value of the block gauge are used to obtain the above Expression 13.

As described above, according to the length measuring apparatus 110 of the present embodiment, the interference between the clockwise light around the block gauge 128 and the counterclockwise light does not pose a problem, and the first screen can be used. The observation of the interference fringes and the observation on the second screen can be performed at the same time.

Therefore, the dimension and parallelism between both end faces of the block gauge can be measured in real time on the basis of each phase difference obtained from each interference fringe observed on each screen and the preliminary value of the block gauge. it can. As a result, in the measuring device using the non-contact optical wave interference system that does not require ringing, it is possible to improve workability and speed up the measuring time, which were extremely difficult in the past.

By observing both sides simultaneously,
The results measured on both sides are based on the same environment, and high-precision measurement can be performed without being affected by environmental changes during measurement.

Further, in the conventional length measuring device using the non-contact optical wave interferometer, it is not possible to prevent the interference between the clockwise light and the counterclockwise light of the annular interferometer due to a problem in the structure of the optical system. , Each measurement may not be performed properly. On the other hand, in the present embodiment, in the measurement of the clockwise light and the counterclockwise light of the annular interferometer, since the first interfering means and the second interfering means are completely separated, the interference of these lights Does not matter. As a result, the measurement can be performed more appropriately.

Further, since one laser beam 115 is divided into two by the one first half mirror 142 and is used for simultaneous measurement of the left end face and the right end face of the block gauge 128, the same conditions can be satisfied. Interfering light can be used for these simultaneous measurements.

By using the length measuring device using the non-contact optical wave interference system as in this embodiment, it is not necessary to ring the block gauge on the base plate.
Of course, highly accurate measurement can be performed.

It should be noted that the present invention is not limited to the above-mentioned structure, and various modifications can be made within the scope of the gist of the invention.

For example, in the above-mentioned configuration, an example in which the dimensions of a block gauge whose rough value such as a preliminary value is known is measured has been described, but the invention can be applied to any other object to be measured.

Further, in the above-mentioned configuration, an example in which one measured dimension is used has been described, but in addition, it can be applied to the measurement of the flatness of the end faces and the parallelism between the end faces from the interference fringes.

In the above configuration, an example of reading the interference fringes observed on the screen has been described. Generally, instead of the screen, a CCD camera or other photoelectric conversion means is used to read the interference fringes. Can be applied.

Further, in the above-mentioned configuration, the example in which the laser beam having a single wavelength is used for the length measurement has been described, but it is also preferable to use another wavelength for stable measurement. For example, a plurality of lasers having different wavelengths are switched to perform measurement. Alternatively, a multi-wavelength laser can be used.

In this case, the correction plate (optical axis correction means) 14 is provided between the first half mirror 142 and the third half mirror 150.
It is particularly preferable to provide 5.

At this time, it is also preferable to finely adjust the inclination of the reflecting surfaces of the reference mirrors 146 and 152 or to provide a similar correction plate before the reference mirrors 146 and 152 according to the wavelength of the laser light 115.

By performing measurement using a plurality of different wavelengths in this way, stable measurement can be performed as compared with the case where measurement is performed using only a single wavelength. Moreover, the correction plate 14 is provided between the first half mirror 142 and the third half mirror 150.
5, the reference mirror 14 is provided for each different wavelength.
It is not necessary to adjust the inclination of the reflecting surfaces of 6,152, and efficient measurement can be performed.

Further, in the above configuration, the phase difference (ε ₄ −ε ₃ ) + (ε ₂ −ε ₁ ) obtained from each interference fringe observed on the first screen and each interference fringe observed on the second screen. )
Of the reference mirror 152 (14) in order to determine the direction of
6), it is preferable to provide a fine movement mechanism 192 as shown in FIG. 4A or a fine movement mechanism 193 as shown in FIG.

The fine movement mechanism 192 shown in FIG. 9A includes a drive section 194, a drive circuit 196, and a computer 172. When an instruction from the computer 172 is given to the drive circuit 196, the drive circuit 196 causes the reference mirror 1 to operate.
The drive unit 1 is configured so that the 52 (146) can be finely moved in the optical axis direction, i direction in the figure, and positioned at a desired position.
Control the operation of 94.

The fine movement mechanism 193 shown in FIG. 11B is an optical wedge 198 installed in front of the reference mirror 152 (146).
A drive unit 202, a drive circuit 204, and a computer 172. When an instruction from the computer 172 is given to the drive circuit 204, the drive circuit 204
Controls the operation of the drive unit 202 so that the optical wedge 198 can be finely moved in the direction j in the drawing, which is a direction orthogonal to the optical axis, and positioned at a desired position.

A fine movement mechanism 192 as shown in FIG.
Alternatively, a fine movement mechanism 193 as shown in FIG.
Therefore, each interference fringe observed on the first screen and
Phase difference obtained from each interference fringe observed on two screens
(Ε_Four−ε_Three) + (Ε_Two−ε ₁) To determine the correct direction
be able to. Or from the obtained interference fringes
The flatness of can be accurately determined.

[0084]

As described above, according to the length measuring apparatus of the present invention, the first interference having the optical axis coinciding with the length measuring axis of the object to be measured and arranged at a predetermined distance. Means and a second interfering means, and a first observing means and a second observing means capable of observing the phase difference of the interference light respectively formed by the respective interfering means, and the reference interference fringes in the first observing means Since the observation of the measurement interference fringes and the observation of the reference interference fringes and the measurement interference fringes by the second observing means are performed at the same time, it is difficult to measure the high precision between the facing end faces of the object to be measured. The actual length measurement of can be performed easily in a short time. Also,
By observing both sides at the same time, the results measured on both sides are based on the same environment, and high-precision measurement can be performed without being affected by environmental changes during measurement. further,
In the present invention, of the light divided into two by one light splitting means, one is used for the measurement of the first interference means and the observation means, and the other is used for the measurement of the second interference means and the observation means, The length can be measured more appropriately. Further, in the present invention, the reading means for reading the phase difference of the interference fringes observed by each of the observation means, the phase difference of each read interference fringes, and the preliminary value between the opposite end faces of the measured object. On the basis of the above, by providing the calculating means for calculating the dimension between the end faces of the object to be measured, the length measurement can be easily obtained in a short time. Further, in the present invention, the light source is
The coherent light of a plurality of different wavelengths is emitted, and the optical axis correction means for correcting the deviation of the optical axis between the light splitting means and the interfering means is provided according to the wavelength of the coherent light. You can do it stably.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a schematic configuration of a general length measuring device.

FIG. 2 is an explanatory diagram of a schematic configuration of a length measuring device according to an embodiment of the present invention.

FIG. 3 is an example of a reference interference fringe and a measurement interference fringe observed by an observing unit of the length measuring apparatus according to the embodiment of the present invention.

FIG. 4 is a modification of the arrangement of the optical system constituent members of the length measuring device according to the embodiment of the present invention.

[Explanation of symbols]

110 length measuring device 112 Single wavelength laser (light irradiation means, light source) 114 Collimator lens (light irradiation means) 115 Laser light (coherent light) 128 block gauge (measurement object) 144 Second half mirror (first interference means) 145 Correction plate (optical axis correction means) 146 First reference mirror (first interference means) 148 First screen (first observation means) 150 Third half mirror (second interference means) 152 Second reference mirror (first interference means) 154 Second screen (second observation means) 170 First reading means 172 computer 174 computing means 176 Measurement data storage 178 Second reading means 180 Calculation information storage unit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Morimasa Ueda             1-20-1 Sakado, Takatsu-ku, Kawasaki City, Kanagawa Prefecture             Ceremony company Mitutoyo (72) Inventor Yutaka Kuriyama             1 stock at 430 Kamikoyokoba, Tsukuba, Ibaraki             Company Mitutoyo (72) Inventor Yuichiro Yokoyama             1 stock at 430 Kamikoyokoba, Tsukuba, Ibaraki             Company Mitutoyo F term (reference) 2F064 AA01 BB00 EE01 FF01 FF05                       FF06 FF08 GG22 HH03 HH08                 2F065 AA22 CC00 FF51 GG04 GG22                       GG23 HH03 HH13 LL00 LL04                       LL35

Claims (5)

[Claims] 1. A length measuring device for measuring a dimension between opposed end faces of an object to be measured whose preliminary value is known, which has an optical axis coincident with the length measuring axis of the object to be measured and has a predetermined separation distance. A first interfering means and a second interfering means arranged at, and a first observing means and a second observing means capable of observing the phase difference of the interference light formed by each of the interfering means, The first interference means emits coherent light having a predetermined beam diameter and wavelength in the length measuring direction of the object to be measured, makes part of the light incident on one end of the object to be measured, and returns reflected light. The rest of the light passes through the side of the object to be measured and is incident on the second interference means, and the second interference means measures coherent light having the same beam diameter and wavelength as the coherent light to the object to be measured. The light is emitted in the long direction, a part of the light is made incident on the other end of the DUT to return the reflected light, and Is passed through the side of the object to be measured and is incident on the first interference means, and the first interference means is coherent light from the second interference means that has passed through the side of the object to be measured, A reference interference light is obtained by superimposing the first reference light, which is a coherent light, and a reflected light obtained by irradiating one end of the measured object with the coherent light from the first interference means, A first reference light, which is an interference light, is superimposed to obtain a measurement interference light, and the second interference means is a coherent light from the first interference means that has passed by the side of the object to be measured, and a coherent light. A reference interference light is obtained by superimposing a second reference light, which is a light, and a coherent light from the second interference means is applied to the other end of the object to be measured, and the reflected light is obtained. A measurement interference light is obtained by superimposing a second reference light which is light, and the first observation means is a reference interference obtained by the first interference means. The light and the measurement interference light are simultaneously observed as interference fringes, and the second observation means is the reference interference light and the measurement interference light obtained by the second interference means as interference fringes, respectively, in the first observation means. Observing at the same time as the observation, the preliminary value between the end faces of the object to be measured facing each other, and the phase difference between the reference interference fringes and the measurement interference fringes observed by the first observing means, and the second observing means. A length measuring apparatus, wherein a dimension between end faces of the object to be measured facing each other is obtained based on a phase difference between an observed reference interference fringe and a measured interference fringe. 2. The length measuring apparatus according to claim 1, wherein one light irradiation unit that emits the coherent light having the predetermined beam diameter and wavelength, and the coherent light from the light irradiation unit are split into two. A light splitting means for causing one split light to enter the first interference means and another split light for the second interference means, the one light irradiation means, the first interference means And a second interferometer, which constitutes an annular interferometer. 3. The length measuring apparatus according to claim 2, wherein an optical path length from the light splitting means to the first interference means, one end of the object to be measured, and the first interference means is L ₁ , and the light splitting is performed. Let L ₂ be the optical path length from the means to the second interference means and the first interference means, and the optical path length from the light splitting means to the second interference means, the other end of the DUT, and the second interference means. It was a L _3, wherein the said light splitting means first interference means, when the optical path length to the second interference means to L _4, the dimension L _B between the end faces facing each of the object to be measured, the following equation A length measuring device that can be represented by. L _B = λ / 2 {N ₄ −N ₃ + N ₂ −N ₁ + (ε
₄ −ε ₃ ) + (ε ₂ −ε ₁ )} where L ₁ : λ (N ₁ + ε ₁ ) L ₂ : λ (N ₂ + ε ₂ ) L ₃ : λ (N ₃ + ε ₃ ) L ₄ : λ _{(N 4 + ε 4) λ} : wavelength _N i (i = 1~4) of the light: natural number quotient when the optical path length Li divided by the wavelength lambda of the coherent light ε _{i (i} = 1~4 ): Phase (ε ₂ −ε ₁ ) which is a fraction of the quotient when the optical path length Li is divided by the wavelength λ of the coherent light: Reference interference fringes and measurement interference fringes observed by the first observation means Phase difference (ε ₄ −ε ₃ ): the phase difference between the reference interference fringes observed by the second observation means and the measured interference fringes 4. The length measuring device according to claim 1, wherein the reading unit reads the phase difference of the interference fringes observed by the observation unit, and the interference fringes obtained by the reading unit. And a calculation means for calculating a dimension between the end faces of the object to be measured based on the phase difference between the end faces of the object to be measured and a preliminary value between the end faces of the object to be measured. apparatus. 5. The length measuring apparatus according to claim 1, wherein the light source emits a plurality of coherent light beams having different wavelengths, and is on an optical axis between the light splitting unit and the interference unit. A length measuring apparatus provided with an optical axis correcting means for correcting the deviation of the optical axis according to the wavelength of the coherent light.