JP2016211957A - Contactless distance measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contactless distance measurement method that allows a use of holography interference to accurately and efficiently measure a distance between a first object surface and second object surface plurally arrayed on a measurement object and mutually facing an opposite direction.SOLUTION: A contactless distance measurement method is configured to: prepare a reference object having a reference distance mo highly accurately measured (preparation step ST1); create reference holograms of a first object surface and second object surface due to first and second hologram optical system (reference hologram creation step ST2); measure positions of the first object surface and second object surface using the obtained reference hologram (reference actual measurement step ST3); calculate an amount of reference deviation δ from a difference between the obtained actually measured distance dD of the reference object and the reference distance mo thereof (reference deviation-amount measurement step ST4); actually measure a distance between the first object surface of a measuring object and the second object surface thereof (object actual measurement step ST5); and calculate a distance Mi between the first object surface of the measuring object and the second object surface thereof from the obtained actually measured distance dD of the reference object and amount of reference deviation δ (object distance correction step ST6).SELECTED DRAWING: Figure 8

Description

  The present invention relates to a non-contact distance measuring method, and relates to a method for measuring a distance between two surfaces having different directions with high accuracy without contact.

  Conventionally, a height master is used to set an accurate height, and a step gauge is used to obtain spatial correction data of a three-dimensional coordinate measuring machine. Each of these height masters and step gauges has a large number of rectangular parallelepiped block gauges, each of which is arranged so that each measurement surface (target surface to be used for measurement as an end measure) has a predetermined interval or a constant pitch. It is a vessel.

  In such a reference device, the position accuracy of each measurement surface is ensured by measuring the position of each measurement surface with high accuracy. In addition, if the position of the measurement surface can be accurately measured, the distance between the surface of one block gauge and the opposite surface (dimension of the block gauge), or the surface of any block gauge and the adjacent block gauge The distance from the surface (block gauge gap) can be measured.

As a method for measuring the position of the measurement surface of the reference device, a method in which a contact-type detector is brought into contact with each measurement surface of the reference device and the position of the detector is measured with a laser interferometer is used.
However, in a contact-type detector, errors due to environmental fluctuations such as temperature are inevitable. In particular, when there are a large number of measurement surfaces, it is necessary to repeat the contact operation with respect to each measurement surface, which increases the work time and further increases the error due to environmental fluctuations described above.
On the other hand, non-contact measurement is performed in which each measurement surface is directly irradiated with laser light.

However, in the measurement by the non-contact type laser interference, it is necessary to make the laser beam incident and reflected on the measurement surface obliquely with respect to a large number of measurement surfaces arranged. In addition, it is necessary to reliably arrange the measurement surface in a narrow positioning region where laser beam interference can be obtained, and an operation for accurately positioning each measurement surface with respect to the laser interferometer is necessary.
In other words, in order to perform non-contact position measurement using a laser interferometer for each of a large number of measurement surfaces arranged at a predetermined pitch such as a reference device, each measurement surface and the laser interferometer are provided. There is a need for a non-contact positioning device that accurately positions.

As such a non-contact positioning device, a non-contact positioning device using holographic interference has been developed (see Patent Document 1).
In Patent Document 1, laser light from a light source is divided into reference light and measurement light, and the measurement light is incident obliquely on an arrayed periodic measurement surface and reflected, and the reflected light is combined with the previous reference light. A hologram is generated and recorded. At the time of positioning, highly accurate positioning is realized by detecting the state where the recorded hologram and the actually generated hologram match in the same arrangement and selecting the position. ing.

As a similar non-contact positioning device, a non-contact positioning device using a white light source having a short coherence distance (coherence length) has been developed (see Patent Document 2).
Patent Document 2 utilizes the short coherence length of a general white light source, and positions the measurement surface when the optical path lengths of the reference light and the measurement light of the Michelson lightwave interferometer coincide.

Japanese Patent Publication No.54-34346 Japanese Patent No. 4057874

  In the positioning by the white light source interferometer of Patent Document 2 described above, since the coherence length of white light mixed with multiple wavelengths is extremely short, in order to obtain a positioning signal in the configuration of the Michelson interferometer, reference light is used. And the optical path length difference between the measurement light and the measurement light must be aligned within about 1 mm. Due to the severe adjustment of the optical path length, there is a problem that the degree of freedom and the application range of the arrangement of the optical components and the configuration of the interference optical system are extremely limited.

Patent Document 2 also discloses an example in which a block gauge surface of a step gauge is a measurement target surface. However, it is not an optical system that takes into account the influence of positioning errors due to subtle inclinations in the direction of the measurement surface of a block gauge set in a long step gauge.
Furthermore, in the positioning by the current white light source interferometer, the illumination on the positioning target surface is limited to the vertical direction, and the positioning of the rough surface is impossible, the measuring object is limited, and the above-described many measuring surfaces are limited. It is difficult to apply to repeated reference devices.

  In addition, in Patent Document 2, the laser interferometer for length measurement is arranged on a straight line in accordance with the Abbe's principle with respect to the long step gauge as a measurement target. In such a situation, the space occupied by the entire measurement system is required to be twice or more the length of the object to be measured, and temperature management during measurement becomes troublesome. In addition, since the Abbe principle is followed, the measurement points on the position detection surface of the long step gauge and the measurement points of the laser interferometer for length measurement are arranged in a space along the length measurement direction. For this reason, there is a problem that the reliability is inferior from the viewpoint of high-accuracy measurement due to the influence of temperature change and geometric measurement error.

In contrast to such positioning in Patent Document 2, the positioning in Patent Document 1 can avoid the problem in Patent Document 2 by performing positioning using holographic interference.
However, even if the positioning as in Patent Document 1 is adopted, for example, when the measurement surfaces to be measured are two surfaces having different directions such as the front surface and the rear surface of the block gauge, the positioning with respect to each is not easy. There was a problem.

That is, in the non-contact positioning device of Patent Document 1 described above, a light projecting device that causes measurement light to enter the measurement surface and a light receiving device that receives reflected light from the measurement surface are installed on both sides of the reference device. The
These light projecting device and light receiving device are installed as a pair with a reference device (its longitudinal axis) in between, and the measurement light is incident on the measurement surface obliquely or is reflected obliquely. Are received on the same side with respect to the measurement surface (crossing the longitudinal direction of the reference device).

According to such a configuration, the measurement surface of the reference device, for example, the front surface (front end side surface of the reference device) or the rear side (surface of the rear end side) of the block gauge arranged in the step gauge is sequentially measured. I can go.
However, when it is desired to measure both the front and rear surfaces of the block gauge, the pair of light projecting device and light receiving device as described above cannot be easily handled.

On the other hand, even with only a pair of light projecting device and light receiving device, for example, the front surface of each block gauge can be measured first, the step gauge can be replaced in the reverse direction, and the rear surface of each block gauge can be measured sequentially. Conceivable.
However, it is necessary to sequentially perform such two measurements, and in order to accurately relate the measurement data of the front side and the rear side, it is necessary to set a common measurement position in each measurement. Is also required.

On the other hand, by forming two types of optical paths that enter and reflect obliquely on the front and rear surfaces of the block gauge, there is a possibility that the front and rear surfaces can be measured with a single measurement operation.
In order to form such two types of optical paths, for example, it is conceivable that the directions of the light projecting device and the light receiving device are changed to either the front end direction or the rear end direction of the reference device for each operation.
However, when the light projecting device and the light receiving device are moved, the position and angle of the optical path for generating the hologram need to be adjusted again.
In particular, if the reference device has alternately opposite measurement surfaces, adjustment of the light projecting device and the light receiving device is required for each measurement surface to be sequentially positioned, which is difficult to adopt in practice.

Apart from this, it is conceivable to install two sets of a light projecting device and a light receiving device facing the front end of the reference device and a light projecting device and a light receiving device facing the rear end.
By using such two sets, it is only necessary to switch the set of the light projecting device and the light receiving device in accordance with the orientation of the measurement surface to be sequentially positioned, even if the reference device alternately repeats the measurement surface in the opposite direction. It is fully employable.

  However, when two sets of light projecting device and light receiving device are used in combination, it is difficult to completely match the measurement position or coordinate system of each optical system between the first set and the second set. In this case, it is necessary to consider the deviation amount of the two sets of optical systems.

  The problems mentioned above are not only due to the reference device in which many measurement surfaces are arranged at the desired pitch, but also to racks, screws, ball screws and similar surfaces where the tooth surfaces are arranged at the desired pitch. It is a problem common to measurement objects in which a large number of measurement target surfaces with different orientations are arranged, such as coils and other members arranged at a pitch of, and in that measurement on a large number of measurement target surfaces with different orientations is repeated, The complexity of each operation affects the overall work efficiency.

  An object of the present invention is to provide a non-contact distance capable of measuring the distance between the first and second target surfaces opposite to each other arranged in a plurality of measurement objects with high accuracy and efficiency using holographic interference. It is to provide a measurement method.

The non-contact distance measuring method of the present invention is a non-contact distance measuring method for measuring the distance between a first target surface and a second target surface that are opposite to each other formed on a measurement object in a non-contact manner. Have
As a preparatory step, a reference object that is used as a reference for the measurement object and whose reference distance between the first object surface and the second object surface is measured with high accuracy, and a detection surface that is arranged opposite to each other and each detection surface is provided. A non-contact distance measuring device having a first hologram optical system and a second hologram optical system arranged at a predetermined detection surface distance is prepared.
As a reference hologram production step, the reference object is mounted on the non-contact distance measuring device, the first object surface of the reference object is arranged on the detection surface of the first hologram optical system, and a first reference hologram is formed. The second reference hologram is produced by moving the reference object mounted on the non-contact distance measuring device and placing the second object surface of the reference object on the detection surface of the second hologram optical system. Make it.

As a reference actual measurement step, the reference object is mounted on the non-contact distance measuring device, the first object surface of the reference object is disposed on a detection surface of the first hologram optical system, and the first reference hologram and The position of the first target surface is measured by hologram interference of the reference object, the reference object mounted on the non-contact distance measuring device is moved, and the second target surface of the reference object is moved to the second hologram optical system. The position of the second target surface is measured by hologram interference with the second reference hologram, the measured positions of the first target surface and the second target surface, and the detection surface distance Is used to measure the measured distance between the first target surface and the second target surface of the reference target object.
As a reference deviation amount measuring step, a reference deviation amount is calculated from a difference between an actually measured distance of the reference object and the reference distance.

In the object measurement step, the measurement object is mounted on the non-contact distance measuring device, the first object surface of the measurement object is disposed on the detection surface of the first hologram optical system, and the first reference hologram The position of the first target surface is measured by the hologram interference with the non-contact distance measuring device, the measurement target mounted on the non-contact distance measuring device is moved, and the second target surface of the measurement target is moved to the second hologram optics. The position of the second target surface is measured by hologram interference with the second reference hologram, the position of the first target surface and the second target surface measured, and the detection surface An actual distance between the first target surface and the second target surface of the measurement object is measured by calculating the distance.
In the object distance correction step, the distance between the first object surface and the second object surface of the measurement object is calculated from the measured distance of the measurement object and the reference deviation amount.

In the present invention, it is possible to measure the distance between the first target surface and the second target surface of the measurement object by performing the preparation process and the reference hologram manufacturing process.
That is, the measured distance between the first target surface and the second target surface can be measured by performing the target object measuring step following the preparation step and the reference hologram manufacturing step.
However, in the calculation of the actual measurement distance here, the distance that is the original measurement result depends on the accuracy of the detection surface distance of the first hologram optical system and the second hologram optical system as numerical values and the measurement error factor in the object actual measurement process. There is a deviation amount.

On the other hand, in the present invention, in the reference actual measurement process, a reference object whose reference distance is measured with high accuracy is used, and for this reference object, a reference actual measurement process similar to the object actual measurement process, The reference deviation amount is calculated by performing the deviation amount measuring step in advance.
In other words, the actual measurement distance of the reference object can be obtained by performing the reference measurement process on the reference object. This measured distance includes the amount of deviation as described above. Here, by performing the reference deviation amount measurement step, the reference deviation amount can be calculated from the difference between the actual distance including the aforementioned deviation amount and the reference distance measured in advance with high accuracy.

The reference deviation amount thus obtained reflects an error factor that occurs in common in the reference actual measurement process and the object actual measurement process, and this reference deviation amount corresponds to the actual measurement distance obtained in the target actual measurement process. By adding this correction, it is possible to calculate an accurate distance that does not include the shift amount.
As described above, according to the non-contact distance measuring method of the present invention, positioning with respect to the first target surface and the second target surface, which are arranged in a plurality of positions on the positioning target object, is performed with high accuracy using holographic interference. It can be done efficiently.

In the non-contact distance measuring method of the present invention, the first hologram optical system and the second hologram optical system are common detection surfaces in which the detection surfaces are set to the same plane, and the detection surface distance is zero. It is desirable to be.
In the present invention, the detection surface distance of the first hologram optical system and the second hologram optical system is 0, and the calculation procedure can be omitted. Furthermore, the reference distance of the reference object can be used as it is as the movement distance of the reference object or the measurement object between the measurement by the first hologram optical system and the measurement by the second hologram optical system.

That is, the first target surface of the reference object or the measurement object is aligned with the common detection surface, the position is measured by the first hologram optical system, and then the reference object or the measurement object is moved by the reference distance. By this movement, the second target surface separated by the reference distance is alternately arranged at the position where the first target surface is located, that is, the common detection surface. Thereby, the second object surface of the reference object or the measurement object is arranged on the common detection surface, and the position can be detected by the second hologram optical system.
In this way, by using a common detection surface set on the same plane, movement between position measurements by the first hologram optical system and the second hologram optical system can be accurately and easily performed using a known reference distance. Can be done.

In addition, regarding the first hologram optical system and the second hologram optical system, it is structurally difficult to completely match each detection surface, and an error may occur due to handling each detection surface as the same surface. is there. However, in the present invention, an error caused by making the detection surfaces of the first and second hologram optical systems the same surface can be included as the above-described reference deviation amount.
Therefore, even if a common detection surface is used for the first hologram optical system and the second hologram optical system, the measurement result can be made highly accurate.

  In the non-contact distance measuring method of the present invention, the first hologram optical system and the second hologram optical system are configured such that the optical elements and the optical paths are symmetrically arranged with respect to the common detection surface, and are used as light sources, respectively. It is desirable to use the same laser light source.

  In the present invention as described above, the first hologram optical system and the second hologram optical system have symmetry, and the measurement conditions are uniform, so that the measurement of the first object surface and the second object surface measured by each is performed. Results can be equalized.

  According to the non-contact distance measuring method of the present invention, the distance between the first target surface and the second target surface that are arranged in a plurality of opposite directions on the measurement object is measured with high accuracy and efficiency using holographic interference. be able to.

The perspective view which shows the step gauge measuring apparatus of 1st Embodiment of this invention. The schematic diagram which shows the optical path of the laser interference length measuring machine of the said 1st Embodiment. The perspective view which shows the relationship between the reference surface or the measurement surface of the said 1st Embodiment, and a laser beam. FIG. 2 is a schematic plan view showing two hologram optical systems of the first embodiment. The schematic plan view which shows the measurement of the 1st object surface in the said 1st Embodiment. The schematic plan view which shows the measurement of the 2nd object surface in the said 1st Embodiment. The schematic diagram which shows the reference | standard deviation amount in the said 1st Embodiment. The flowchart which shows the measurement procedure in the said 1st Embodiment. The schematic diagram which shows the measurement operation | movement in the said 1st Embodiment. The perspective view which shows the step gauge measuring apparatus of 2nd Embodiment of this invention. The schematic diagram which shows the optical path of the laser interference length measuring machine of the said 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
1 to 9 show a first embodiment of the present invention.
In FIG. 1, in this embodiment, a step gauge measuring apparatus 1 having two hologram optical systems is used to measure a distance such as a pitch and a gap in a step gauge 2 that is a long reference device.

The step gauge 2 which is a measurement object has a large number of block gauges 2B formed in the same size by a long gauge holder 2H arranged along the longitudinal direction E of the step gauge 2 at regular intervals of a predetermined pitch. Is.
In the step gauge 2, each block gauge 2B has a first measurement surface 2F on one end side in the longitudinal direction E and a second measurement surface 2S on the opposite side.

  The first measurement surface 2 </ b> F and the second measurement surface 2 </ b> S are formed with a constant pitch between those on the same side. Further, the distance (the dimension in the longitudinal direction E) between the first measurement surface 2F and the second measurement surface 2S in each block gauge 2B and the distance between the first measurement surface 2F and the second measurement surface 2S facing each other adjacent to the block gauge 2B ( The gaps in the longitudinal direction E are also formed constant.

In the present embodiment, the step gauge measurement device 1 measures each position using the first measurement surface 2F and the second measurement surface 2S of each block gauge 2B as the first target surface and the second target surface, and the present invention. By performing the calculation based on the above, it is possible to accurately measure the pitch, size and gap of the block gauge 2B described above.
First, the step gauge measuring apparatus 1 of this embodiment will be described.

[Configuration of Step Gauge Measuring Device 1]
The step gauge measuring device 1 determines the position in the arrangement direction (longitudinal direction E of the gauge holder 2H) for each of the measurement surfaces 2F and 2S (one of them) as the first target surface and the second target surface. Each position in each block gauge 2B is measured. Then, the respective pitches of the measurement surfaces 2F and 2S (the arrangement pitch of the first measurement surface 2F and the arrangement pitch of the second measurement surface 2S) are measured from the measured positions.

In order to perform such measurement, the step gauge measuring device 1 includes a moving device 3, a measuring head 4, a head mechanism 5, a non-contact positioning device 6, a laser interference length measuring device 7, and a control device 8.
The control device 8 measures the pitch of the measurement surfaces 2F and 2S in the step gauge 2 by controlling the moving device 3, the head mechanism 5, the non-contact positioning device 6 and the laser interference length measuring device 7 in cooperation with each other. To do.

The moving device 3 includes a moving table 31 that holds the step gauge 2, a base table 32 that supports the moving table 31, and an installation table 33 on which a part of the laser interferometer 7 is installed.
The movable table 31 and the base table 32 are constituted by long members extending along the longitudinal direction E of the step gauge 2.

The base 32 is installed on a stable surface plate. A high-precision feed mechanism (not shown) using a ball screw or the like is installed between the base 32 and the mobile base 31, and the mobile base 31 is in the longitudinal direction E of the step gauge 2 with respect to the base 32. It can move along.
The installation table 33 is installed at an end of the movable table 31 and extends horizontally in a direction intersecting with the movable table 31. A light projecting unit 71 and a light receiving unit 72 (details will be described later) of the laser interference length measuring machine 7 are installed at the end of the installation table 33, respectively.

In the moving device 3, the step gauge 2 to be measured can be placed on the moving table 31, and the step gauge 2 can be moved to an arbitrary position in the longitudinal direction E by an operation command from the control device 8.
Specifically, in order to measure the distance from the measurement position of the step gauge 2 to each measurement surface 2F, 2S, each measurement surface 2F, 2S is sequentially placed at a predetermined target position with respect to the measurement head 4. The step gauge 2 is moved.

More specifically, the first measurement surface 2F, which is one measurement surface, is first positioned with respect to one block gauge 2B, the distance from the measurement position is measured by the laser interferometer length measuring machine 7, and then the opposite is performed. The second measurement surface 2S which is the side measurement surface is positioned, the distance from the measurement position (position in the step gauge 2) is measured, and these are sequentially recorded to calculate the pitch of each side.
The total moving amount of the moving device 3 (the maximum moving amount of the moving table 31 with respect to the base table 32) corresponds to the entire length of the step gauge 2.

The measuring head 4 is supported above the moving device 3 by a head mechanism 5.
The measuring head 4 has an inverted U-shaped plate 41, and the step gauge 2 placed on the moving device 3 can pass through the central recess of the plate 41.
On the plate 41, three reflecting mirrors 73, 74, and 75 (details will be described later) of the laser interferometer 7 are installed.

A flat H-shaped extension plate 42 is connected to the inverted U-shaped tip of the plate 41. The extension plate 42 on each side is provided with a light projecting device 61 and a light receiving device 62 (details will be described later) of the non-contact positioning device 6.
The light projecting device 61 and the light receiving device 62 are arranged in a pair so as to be parallel to the step gauge 2 placed on the moving device 3 and sandwich the step gauge 2 from both sides.

The head mechanism 5 supports the measuring head 4 above the moving device 3, and can move the measuring head 4 along the longitudinal direction E of the step gauge 2 when adjusting the non-contact positioning device 6.
At this time, the total movement amount of the head mechanism 5 is very small (about several mm). However, the support rigidity of the measuring head 4, that is, the holding ability of the position of the measuring head 4 is designed to be relatively high.

In the step gauge measuring apparatus 1 of the present embodiment, as described above, the positions of the measurement surfaces 2F and 2S in the step gauge 2 are sequentially measured using two hologram optical systems.
For this purpose, in the step gauge measuring device 1, the measurement surfaces 2 </ b> F and 2 </ b> S to be measured are aligned with the measuring head 4 by the non-contact positioning device 6, and the position of the measuring head 4 is measured by the laser interference length measuring device 7. To do.

  That is, the position of each measurement surface 2F, 2S in the step gauge 2 is indirectly adjusted with high accuracy by the laser interferometer 7 via the measurement head 4 equipped with the two hologram optical systems that perform the positioning function. taking measurement. By repeating this measurement for each measurement surface 2F, 2S of each block gauge 2B, the respective positions of the measurement surfaces 2F, 2S in the step gauge 2 are measured in a non-contact manner.

  In such a measurement, the step gauge 2 is moved by the moving device 3 in order to place the measurement surfaces 2F and 2S to be measured at the measurement position of the measurement head 4. Then, when the measurement surfaces 2F and 2S to be measured are moved and arranged at the measurement position of the measurement head 4, it is important that the relative positions are positioned with high accuracy.

Therefore, in this embodiment, the measurement surfaces 2F and 2S and the measurement head 4 are all measured surfaces while the step gauge 2 is moved by the moving device 3 using the non-contact positioning device 6 using the holographic interference of the measurement head 4. Positioning is performed with high accuracy so that 2F and 2S have the same conditions.
Hereinafter, the measurement procedure of the laser interferometer 7, the non-contact positioning device 6, and the step gauge 2 based on these measurement results will be sequentially described.

[Laser interferometer 7]
The laser interference length measuring machine 7 measures the position of the measurement head 4 with high accuracy in a state where the measurement surfaces 2F and 2S and the measurement head 4 are positioned under the same conditions by the non-contact positioning device 6. The position of the measurement surfaces 2F and 2S arranged in 2 is non-contact measured with high accuracy.

The laser interferometer 7 includes a laser beam projecting unit 71 and a light receiving unit 72, and also includes reflecting mirrors 73, 74, and 75 having three reflecting surfaces that form a right angle with each other.
The light projecting unit 71 and the light receiving unit 72 are respectively fixed to opposite ends of the installation table 33 of the moving device 3.

The three reflecting mirrors 73, 74, and 75 are fixed to the plate 41 of the measuring head 4, respectively, and change relative distances (length changes) with the light projecting unit 71 and the light receiving unit 72 that move together with the step gauge 2. When woken up, it functions as a reflector of the laser interferometer 7.
The reflecting mirrors 73 and 74 are disposed on the opposite sides with the moving device 3 interposed therebetween. The reflecting mirror 75 is disposed above the moving device 3 and on the central axis of the moving device 3.

The positions and postures of the light projecting unit 71, the light receiving unit 72, and the reflecting mirrors 73, 74, and 75 are adjusted so as to constitute the following optical path.
As shown in FIG. 2A and FIG. 2B, the laser light emitted from the light projecting unit 71 travels along the longitudinal direction E of the step gauge 2 placed on the moving device 3, and is reflected by the reflecting mirror. 73 is incident. The laser light reflected by the reflecting mirror 73 is incident on the reflecting mirror 75, further reflected and incident on the reflecting mirror 74. The laser beam reflected by the reflecting mirror 74 travels in the opposite direction along the longitudinal direction E of the step gauge 2 placed on the moving device 3 and is received by the light receiving unit 72.

In the laser interference length measuring machine 7 having such an optical path, the moving base 31 of the moving device 3 moves to move from the light projecting unit 71 to the reflecting mirror 73, which is a section along the longitudinal direction E of the step gauge 2. And the optical path length from the reflecting mirror 74 to the light receiving unit 72 changes.
Therefore, the measurement laser beam received by the light receiving unit 72 is caused to interfere with the reference laser beam sent directly from the light projecting unit 71 to the light receiving unit 72, thereby measuring the displacement of the moving table 31 and measuring the distance to the measurement head 4. Changes can be measured.

Further, the three reflecting mirrors 73, 74, and 75 can form an optical path that spans the step gauge 2 from one side to the opposite side.
That is, by arranging the reflecting mirror 75 higher than the reflecting mirrors 73 and 74 on both sides of the step gauge 2, the optical path from the light projecting unit 71 to the reflecting mirror 73 and the space from the reflecting mirror 74 to the light receiving unit 72 are arranged. These optical paths can be maintained at the heights of the block gauge 2B and the measurement surfaces 2F and 2S, which are the objects of length measurement.
With such a configuration, it is possible to suppress the occurrence of errors by bringing the measurement axis close to each other, and it is possible to eliminate measurement errors caused by a change in the posture of the step gauge 2, particularly pitching errors and yawing errors.

  Further, as shown in FIGS. 2A and 2B, the reflection positions of the reflecting mirrors 73, 74, and 75 are points A, B, and C, and the midpoint of the line segment that connects the point A and the point C Assuming that the point N is the same height as the point N of the measurement surfaces 2F and 2S (the measurement surface 2S is illustrated in FIG. 2) and the same axial line position as the longitudinal direction E of the step gauge 2 is a point M, a line segment AB and a line segment BC The sum of the lengths in the space is equal to the round-trip length of the line segment MN. This is based on the optophysical properties unique to right-angle trihedral mirrors, such as reflectors 73, 74, and 75.

As a result, the step gauge 2 can be straddled by the three reflecting mirrors 73, 74, 75 as described above, and an optical path equivalent to reflecting the laser beam at the point M on the measurement surfaces 2F, 2S (measurement surface) An optical path equivalent to the distance from the point M on 2F, 2S to the light projecting unit 71 or the light receiving unit 72 along the longitudinal direction E of the step gauge 2 can be secured.

[Optical system of non-contact positioning device 6]
As shown in FIG. 3, the non-contact positioning device 6 has two hologram optical systems HS1 and HS2 for measuring the positions of the first measurement surface 2F and the second measurement surface 2S of the step gauge 2.
In the first hologram optical system HS1, laser light LF is incident obliquely on the first measurement surface 2F of the step gauge 2, and the laser light LFS reflected by the first measurement surface 2F and reference light from the same light source (not shown) ) With holographic interference.
In the second hologram optical system HS2, laser light LS is incident on the second measurement surface 2S, and holographic interference is generated between the laser light LSS reflected by the second measurement surface 2S and reference light (not shown) from the same light source. Perform positioning.

Here, in the non-contact positioning device 6 of the present embodiment, a virtual detection surface D is set as a common detection surface for the first and second hologram optical systems HS1 and HS2.
The detection surface D is a plane orthogonal to the longitudinal direction E of the step gauge 2, and the position along the longitudinal direction E is a target position where the measurement surfaces 2F and 2S are to be positioned (predetermined position and measurement in the step gauge measuring device 1). A predetermined position).

In the present embodiment, the measurement surfaces 2F and 2S of the block gauges 2B are arranged on such a common detection surface D, the laser beams LF and LS for holographic interference are projected, and the height is increased based on the reflected light. Perform accurate positioning.
That is, as the first hologram optical system HS1, the first measurement surface 2F is aligned with the detection surface D, the laser beam LF on the side corresponding to the first measurement surface 2F is incident, and positioning by holographic interference is performed.
Further, as the second hologram optical system HS2, the second measurement surface 2S is aligned with the detection surface D, the laser beam LS on the side corresponding to the second measurement surface 2S is incident, and positioning by holographic interference is performed.

In the non-contact positioning device 6 of the present embodiment, the laser beams LF and LS are incident on the detection surface D from the opposite sides to the same position at the same angle.
Thus, by posting the laser beams LF and LS with the measurement surfaces 2F and 2S arranged on the detection surface D, the laser beams LFS and LSS reflected by the measurement surfaces 2F and 2S of the detection surface D are obtained. .
Further, in a state where the measurement surfaces 2F and 2S are not arranged, the laser beam LF passes through the detection surface D and travels on the same optical path as the laser beam LSS, and the laser beam LS passes through the detection surface D and the laser beam LFS. It is configured to travel along the same optical path (details will be described with reference to FIGS. 4 to 6).

  The non-contact positioning device 6 according to the present embodiment has a holographic interference with respect to the measurement surfaces 2F and 2S opposite to each other arranged on the detection surface D by the two optical systems having the optical path configuration shown in FIG. Expression positioning can be performed. The operation necessary to arrange the measurement surfaces 2F and 2S on the detection surface D is only to move the step gauge 2 by one length of the block gauge 2B.

[Device configuration of non-contact positioning device 6]
As described above, the non-contact positioning device 6 according to the present embodiment has a positioning target object (first measurement surface 2F and second measurement surface 2S) arranged in a predetermined arrangement direction (longitudinal direction E) ( The step gauge 2) is moved in the arrangement direction, and these measurement surfaces 2F and 2S are positioned at predetermined target positions (predetermined positions in the length measurement possible region of the laser interference length measuring instrument 7).

For this purpose, the non-contact positioning device 6 has a pair of light projecting device 61 and light receiving device 62 as described in FIG. 1, and these light projecting device 61 and light receiving device 62 are placed on the moving device 3. The step gauge 2 is arranged so as to be sandwiched from both sides.
Further, the non-contact positioning device 6 has a control device (also used as the control device 8 described above) that positions the step gauge 2 by using holographic interference obtained by the light projecting device 61 and the light receiving device 62.

FIG. 4 shows a light projecting device 61 and a light receiving device 62 of the non-contact positioning device 6.
The light projecting device 61 and the light receiving device 62 are arranged so as to sandwich the axis line in the longitudinal direction E of the step gauge 2.
On the axis of the step gauge 2 in the longitudinal direction E, the detection surface D that is the target position of the measurement surfaces 2F and 2S described above is set.
The detection surface D has a direction orthogonal to the longitudinal direction E, and is set so as to cross an intermediate position between the light projecting device 61 and the light receiving device 62.

  Each optical element (details will be described later) of the light projecting device 61 and the light receiving device 62 includes a first set 6F that is a main configuration of the first hologram optical system HS1, and a second set that is a main configuration of the second hologram optical system HS2. A pair with 6S is installed symmetrically across the detection surface D.

That is, one side of the detection surface D (the side where the first measurement surface 2F is formed by the block gauge 2B) is the first set 6F, and the other side (the second measurement surface 2S is formed by the block gauge 2B). The side) is the second set 6S, and the pair of the first set 6F and the second set 6S are the same elements arranged symmetrically.
Then, the first measurement surface 2F is positioned by the block gauge 2B by the elements of the first set 6F, and the second measurement surface 2S is positioned by the block gauge 2B by the elements of the second set 6S.
Next, each element of the light projecting device 61 and the light receiving device 62 will be described.

The light projecting device 61 includes a laser light source 610 that supplies a laser beam Lo, and a right-angle prism 611 that divides the supplied laser beam Lo. The laser light source 610 and the right-angle prism 611 are installed on the extension of the detection surface D.
A beam splitter 613 and a reflecting mirror 612 are disposed on the first set 6F side of the right-angle prism 611 (the side where the first measurement surface 2F in the block gauge 2B is present).
A beam splitter 614 and a reflecting mirror 615 are arranged on the second set 6S side of the right-angle prism 611 (the side where the second measurement surface 2S in the block gauge 2B is present).

These beam splitters 613 and 614 and reflecting mirrors 612 and 615 are arranged symmetrically with respect to the detection surface D.
On the light receiving device 62 side of the light projecting device 61, light projecting lenses 616, 617 and 618, 619 are arranged along the beam splitters 613, 614 and the reflecting mirrors 612, 615 described above.

The light receiving device 62 has a first generation surface P1 on the first set 6F side and a second generation surface P2 on the second set 6S side.
The first generation surface P <b> 1 is disposed to face the lens 616 of the light projecting device 61. On the extension of the axis extending from the lens 616 to the first generation surface P1, a recording medium 621 capable of recording a hologram, a lens 622, and an optical sensor 623 are installed.
The second generation surface P <b> 2 is disposed to face the lens 619 of the light projecting device 61. On the extension of the axis from the lens 619 to the second generation surface P2, a recording medium 624 capable of recording a hologram, a lens 625, and an optical sensor 626 are installed.

[Details of optical path configuration in non-contact positioning device 6]
4, in the non-contact positioning device 6 configured as described above, two optical paths (laser beams LF and LS in FIG. 3) are formed between the light projecting device 61 and the light receiving device 62.
In the light projecting device 61, the laser light Lo from the laser light source 610 is divided by the right-angle prism 611, and the divided laser lights L1 and L2 are opposite to each other on the same axis (the first set 6F direction and the second set 6S). Direction).

In the first set 6F, the laser beam L1 is incident on the beam splitter 613, and the reflected beam is the laser beam L1S and the transmitted beam is the laser beam L1R.
The laser beam L1R is reflected by the reflecting mirror 612, passes through the lens 616, is orthogonal to the longitudinal direction E, and is sent to the first generation surface P1 of the first set 6F.
The laser light L1S passes through the lens 617, obliquely intersects the detection surface D, and is sent to the second generation surface P2 of the second set 6S.

In the second set 6S, the laser beam L2 is incident on the beam splitter 614, and the reflected beam is the laser beam L2S and the transmitted beam is the laser beam L2R.
The laser beam L2R is reflected by the reflecting mirror 615, passes through the lens 619, is orthogonal to the longitudinal direction E, and is sent to the second generation surface P2 of the second set 6S.
The laser beam L2S passes through the lens 618 and obliquely intersects the detection surface D and is sent to the first generation surface P1 of the first set 6F.

  Therefore, in a state where the block gauge 2B is not disposed on the detection surface D, the laser beam L1R and the laser beam L2S transmitted through the detection surface D are incident on the first generation surface P1, and the second generation surface P2 is incident on the second generation surface P2. Then, the laser beam L2R and the laser beam L1S transmitted through the detection surface D are incident.

  If any one of the block gauges 2B of the step gauge 2 is arranged on the second set 6S side of the detection surface D and the first measurement surface 2F is arranged on the detection surface D as shown in FIG. The laser beam L1S is reflected by the first measurement surface 2F disposed on the detection surface D, and can function as the laser beam LF of FIG. 3 described above.

  Further, as shown in FIG. 6, if any one of the block gauges 2B of the step gauge 2 is disposed on the first set 6F side of the detection surface D and the second measurement surface 2S is disposed on the detection surface D, The laser light L2S is reflected by the second measurement surface 2S arranged on the detection surface D, and can function as the laser light LS of FIG. 3 described above.

  The laser light L1S reflected by the first measurement surface 2F (corresponding to the laser light LFS in FIG. 3) is incident on the first generation surface P1. At this time, the optical path of the reflected laser light L1S is projected from the lens 618 toward the first generation surface P1 in a state where the detection surface D does not have the block gauge 2B (see FIG. 4) and passes through the detection surface D. It becomes the same as the optical path of the laser beam L2S (which corresponds to the laser beam LS in FIG. 3).

  Further, the laser beam L2S reflected by the second measurement surface 2S (corresponding to the laser beam LSS in FIG. 3) is incident on the second generation surface P2. At this time, the optical path of the reflected laser light L2S is projected from the lens 617 toward the second generation surface P2 in a state where the detection surface D does not have the block gauge 2B (see FIG. 4) and passes through the detection surface D. The optical path of the laser beam L1S (corresponding to the laser beam LF in FIG. 3) is the same.

[Positioning operation by non-contact positioning device 6]
4, in the non-contact positioning device 6 described above, the first hologram H1 corresponding to the first measurement surface 2F of the block gauge 2B is generated on the first generation surface P1, and the block gauge 2B is generated on the second generation surface P2. A second hologram H2 corresponding to the second measurement surface 2S is generated.
Further, the first reference hologram RH1 used for comparison with the first hologram H1 is recorded on the recording medium 621 of the first set 6F, and the comparison with the second hologram H2 is performed on the recording medium 624 of the second set 6S. The second reference hologram RH2 used for the recording is recorded.

In the first reference hologram RH1, the block gauge 2B serving as a reference is installed on the non-contact positioning device 6, and the first measurement surface 2F is positioned with high accuracy on the detection surface D (see FIG. 5). 1st hologram H1 produced | generated on 1 production | generation surface P1 is recorded.
In the second reference hologram RH2, the reference block gauge 2B is installed on the non-contact positioning device 6 and the second measurement surface 2S is positioned on the detection surface D with high accuracy (see FIG. 6). 2 The second hologram H2 generated on the generation surface P2 is recorded.

  The first and second reference holograms RH1 and RH2 produced in this way are in a state where the first measurement surface 2F or the second measurement surface 2S of the block gauge 2B is positioned with high accuracy on the detection surface D, respectively. It will be a copy.

  Therefore, in the actual measurement of the block gauge 2B, when the current first hologram H1 (raw hologram) and the first reference hologram RH1 (freezing hologram) are completely overlapped, the first measurement surface 2F of the block gauge 2B is measured. Is positioned with high accuracy on the detection surface D of the measuring head 4. In this state, the current position of the first measurement surface 2F can be measured with high accuracy by measuring the position of the measurement head 4 with the laser interference length measuring machine 7.

  Similarly, in a state where the current second hologram H2 (raw hologram) and the second reference hologram RH2 (freezing hologram) are completely overlapped, the second measurement surface 2S of the block gauge 2B is the detection surface of the measurement head 4. D is positioned with high accuracy. In this state, the current position of the second measurement surface 2S can be measured with high accuracy by measuring the position of the measurement head 4 with the laser interference length measuring machine 7.

Such a positioning operation on the detection surface D is executed by the control device 8 (see FIG. 1) connected to the optical sensors 623 and 626 of the non-contact positioning device 6 in the actual measurement operation.
The control device 8 generates a first hologram H1 generated on the first generation surface P1 and a second hologram H2 generated on the second generation surface P2 based on the light intensity signals S1 and S2 from the optical sensors 623 and 626. To detect. Further, the positioning operation of the first measurement surface 2F using the first hologram H1 and the first reference hologram RH1 (see FIG. 5), and the second measurement surface 2S using the second hologram H2 and the second reference hologram RH2. The positioning operation (see FIG. 6) is executed.

[Details of positioning operation by non-contact positioning device 6]
As described above, when the reference holograms RH1 and RH2 are prepared on the recording media 621 and 624, the step gauge 2 can be positioned by the non-contact positioning device 6.

Positioning of the step gauge 2 by the non-contact positioning device 6 (high-precision positioning of the first measurement surface 2F and the second measurement surface 2S with respect to the detection surface D) is performed according to the following procedure.
First, as shown in FIG. 1, a step gauge 2 as a measurement object is attached to a moving device 3. Before and after the mounting, the above-described reference holograms RH1 and RH2 are prepared (prepared as described above or loaded with reference holograms RH1 and RH2 data from the outside).

Next, as shown in FIG. 5, the step gauge 2 is moved, and the first measurement surface 2F of the block gauge 2B is aligned with the detection surface D.
Then, in the first set 6F, the laser beams L1R and L1S are emitted from the lenses 616 and 617. The laser beam L1R is directly incident on the first generation surface P1, and the laser beam L1S is reflected by the first measurement surface 2F on the detection surface D and is incident on the first generation surface P1.

  On the first generation surface P1, the first hologram H1 is generated by the incident laser beams L1R and L1S. Therefore, in the recording medium 621, the first reference hologram RH1 and the first hologram H1 that are already produced are superimposed and detected by the optical sensor 623 through the lens 622.

  The optical sensor 623 detects the light intensity signal S1 reflecting the overlapping state of the first hologram H1 and the first reference hologram RH1. The intensity change of the light reflecting the superposition state is maximum at the moment when the superposition of the first hologram H1 and the first reference hologram RH1 is best matched when the step gauge 2 is moved while the moving device 3 is operated. It becomes. The moment is a positioning signal for the first measurement surface 2F of the block gauge 2B and is recognized by the control device 8.

  With such a function, the first measurement surface 2F is positioned with high accuracy with respect to the detection surface D. Therefore, by measuring the distance with the laser interference length measuring instrument 7 in this state, the position of the first measurement surface 2F of the block gauge 2B that is currently measured (the distance from the reference position of the laser interference length measuring instrument 7). ) Can be measured.

Subsequently, as shown in FIG. 6, the step gauge 2 is moved so that the second measurement surface 2S of the block gauge 2B is aligned with the detection surface D.
Then, in the second set 6S, the laser beams L2R and L2S are emitted from the lenses 619 and 618. The laser beam L2R is directly incident on the second generation surface P2, and the laser beam L2S is reflected by the second measurement surface 2S on the detection surface D and is incident on the second generation surface P2.

  On the second generation surface P2, the second hologram H2 is generated by the incident laser beams L2R and L2S. On the recording medium 624, the second reference hologram RH2 is reproduced. The second hologram H2 and the second reference hologram RH2 are superimposed and detected by the optical sensor 626 through the lens 625.

  The optical sensor 626 detects the light intensity signal S2 reflecting the overlapping state of the second hologram H2 and the second reference hologram RH2. The intensity change of the light reflecting the superposition state is maximum at the moment when the superposition of the second hologram H2 and the second reference hologram RH2 is best matched when the step gauge 2 is moved while operating the moving device 3. It becomes. The moment is a positioning signal for the second measurement surface 2S of the block gauge 2B and is recognized by the control device 8.

  With such a function, the second measurement surface 2S is positioned with high accuracy with respect to the detection surface D. Therefore, by measuring the distance with the laser interference length measuring device 7 in this state, the position of the second measurement surface 2S of the block gauge 2B currently being measured (the distance from the reference position of the laser interference length measuring device 7). ) Can be measured.

  By using the step gauge measuring apparatus 1 as described above, the position of the first measurement surface 2F and the second measurement surface 2S of each block gauge 2B in the step gauge 2 (distance from the reference position of the laser interferometer 7). Can be measured sequentially.

[Measurement procedure of step gauge 2]
As described above, from the positions of the first measurement surface 2F and the second measurement surface 2S of each block gauge 2B measured by the step gauge measurement device 1 of the present embodiment, the pitch, dimension, and size of each block gauge 2B in the step gauge 2 The gap can be measured.
Further, in the present embodiment, by measuring a reference deviation amount δ (see FIG. 7) of one block gauge 2B that is selected in advance based on the present invention, the first reference surface 2F (first The dimension and gap of each block gauge 2B related to both the target surface) and the second reference surface 2S (second target surface) can be measured with high accuracy.

If FIG. 7 demonstrates, the block gauge 2B used as one reference | standard will have the 1st reference plane 2F and the 2nd reference plane 2S, the distance of the longitudinal direction E, ie, the block gauge 2B used as a reference | standard, The dimension along the longitudinal direction E is the reference distance mo.
In order to measure the dimension (mo) of the block gauge 2B as a reference again, the position D1 of the first reference surface 2F is measured by the first optical system, and the position of the second reference surface 2S is measured by the second optical system. A method of measuring D2 and calculating a distance dD that is a difference between them can be adopted.

Here, it is assumed that the first optical system that measures the first reference surface 2F is the reference position 01, and the second optical system that measures the second reference surface 2S is the reference position 02.
In order for the distance dD to be the reference distance mo correctly, it is necessary that both reference positions 01 and 02 match. For this reason, the first and second optical systems are set so that the reference positions 01 and 02 coincide.
However, even if precise adjustment is performed, deviation of the reference positions 01 and 02 is unavoidable due to environmental factors. As a result, a deviation amount δ = 01-02 occurs in the coordinate system of the first and second optical systems.

The position D1 of the first reference surface 2F described above corresponds to the distance from the reference position 01, and the position D2 of the second reference surface 2S corresponds to the distance from the reference position 02. Here, the position D2 of the second reference plane 2S can be expressed as D2 = D1−mo−δ by using the reference distance mo and the shift amount δ of the block gauge 2B as a reference.
Therefore, if the reference distance mo, which is the correct dimension of the reference block gauge 2B, is known, the shift amount δ = D1-mo-D2 can be calculated from the positions D1 and D2.

If the shift amount δ (reference shift amount) of the first and second optical systems can be calculated, the positions D1 and D2 are measured by the first and second optical systems, so that the block gauge 2B The dimension mc = D1-D2-δ = dD-δ can be calculated, and the calculated dimension mc matches mo.
Thus, by measuring the reference deviation amount δ of the first and second optical systems, the dimensions, gaps, or pitches of the plurality of block gauges 2B can be accurately determined using two systems of optical systems. Be able to calculate.

  In order to consider such a reference deviation amount δ, in this embodiment, prior to the sequential measurement of the first measurement surface 2F and the second measurement surface 2S of each block gauge 2B in the step gauge 2, two systems of optical systems are used. A process for measuring the reference deviation amount δ resulting from is performed.

That is, as shown in the measurement procedure step of FIG. 8, the actual measurement procedure of this embodiment is as follows. First, the preparation step ST1, the reference hologram production step ST2, and the reference measurement step ST3 are performed on the reference block gauge 2B. Then, the reference deviation amount measuring step ST4 is executed.
Then, using the obtained reference deviation amount δ as a distance correction value, for each block gauge 2B in the step gauge 2, an object measurement step ST5, an object distance correction step ST6, and a calculation step ST7 that are actual measurements. Is repeatedly executed to realize highly accurate non-contact measurement of the step gauge 2.
Hereafter, each process in the measurement procedure of this embodiment is demonstrated with FIG. 8 and FIG.

In the preparation step ST1, a reference object serving as a reference for the plurality of block gauges 2B of the step gauge 2 as a measurement object is prepared.
Specifically, first, one block gauge 2B of the step gauge 2 is selected as a reference block gauge. Then, the reference distance mo (dimension along the longitudinal direction E) between the first reference surface 2F and the second reference surface 2S (first target surface and second target surface) of the selected block gauge 2B serving as a reference is selected. Measure with high accuracy in advance.
In this measurement, the above-described step gauge measuring device 1 may be used, or a measuring means other than the step gauge measuring device 1 may be used. Further, it may be a measurement of a master piece or the like corresponding to the block gauge 2B as a reference, which is different from the step gauge 2 which is a measurement object.

In the preparation step ST1 of the present embodiment, the above-described step gauge measuring device 1 is used as a non-contact distance measuring device having the first hologram optical system HS1 and the second hologram optical system HS2 arranged in opposite directions.
In the step gauge measuring apparatus 1 of the present embodiment, the first hologram optical system HS1 and the second hologram optical system HS2 are a common detection surface D, and the detection surface distance is zero.

  In the reference hologram manufacturing step ST2, the step gauge 2 is attached to the step gauge measuring device 1, and the first reference surface 2F and the second reference surface 2S of any one of the block gauges 2B as the reference object are aligned with the detection surface D, respectively. This is a step of producing a reference hologram for each.

  First, as shown in FIG. 5, the position of the step gauge 2 is measured while observing the measured value by the laser interference length measuring machine 7 so that the first reference surface 2F of the block gauge 2B serving as a reference can be accurately placed on the detection surface D. Adjust. Then, the hologram generated on the first generation surface P1 is recorded as the first reference hologram RH1 in a state where the first reference surface 2F is at an accurate position on the step gauge 2.

Subsequently, the step gauge 2 is moved along the longitudinal direction E by the dimension of the reference block gauge 2B.
Then, as shown in FIG. 6, the step gauge 2 while observing the measured value by the laser interference length measuring machine 7 so that the position of the second reference surface 2S of the reference block gauge 2B can be accurately placed on the detection surface D. Adjust the position.
A hologram generated on the second generation surface P2 is recorded as the second reference hologram RH2 in a state where the second reference surface 2S is at an accurate position on the step gauge 2.

  When the above preparation step ST1 and reference hologram production step ST2 are completed, a reference measurement step ST3 and a reference deviation amount measurement step ST4 are executed.

  In the reference actual measurement step ST3, the position of the first reference surface 2F, the position of the second reference surface 2S, and the distances of the reference block gauge 2B are actually measured with the step gauge 2 attached to the step gauge measuring device 1. It is a process.

First, as shown in FIG. 5, the first reference surface 2F of the block gauge 2B serving as a reference is arranged on the detection surface D. Then, the position of the first reference surface 2F is detected by the first hologram optical system HS1. At the same time, the measurement counter is actuated by a command from the control device 8 and the counting of interference fringes by the laser interference length measuring machine 7 is started.
9A, when the first reference surface 2F is on the detection surface D, the laser interferometer 7 measures the distance D1 from the reference position 01 of the first hologram optical system HS1, and this is This is a position D1 on the step gauge 2 of the first reference surface 2F of the block gauge 2B serving as a reference.

Subsequently, the second reference surface 2S of the block gauge 2B serving as a reference is arranged on the detection surface D as shown in FIG. Then, the position of the second reference surface 2S is detected by the second hologram optical system HS2. At the same time, the measurement counter is actuated by a command from the control device 8 and the counting of interference fringes by the laser interference length measuring machine 7 is stopped.
Accordingly, the reference distance mo of the reference block gauge 2B is actually measured as dD using the step gauge measuring apparatus 1.
9B, the reference block gauge 2B is moved along the longitudinal direction E by a distance T in order to place the second reference surface 2S on the detection surface D. By setting the distance T as the reference distance mo of the reference block gauge 2B that has been measured in advance, the second reference surface 2S of the reference block gauge 2B is arranged on the detection surface D.

When the second reference surface 2S is on the detection surface D, the laser interferometer 7 measures the distance D2 from the reference position 02 of the second hologram optical system HS2, and this is the second reference surface of the block gauge 2B that is the reference. It becomes the position D2 in the step gauge 2 of 2S.
In this embodiment, since the detection surface distance is 0, the measured distance dD = D1-D2 from the measured positions D1 and D2 from the first reference surface 2F to the second reference surface 2S of the reference block gauge 2B. Can be requested.

The reference deviation amount measuring step ST4 is a step of calculating the reference deviation amount δ from the difference between the measured distance dD of the reference block gauge 2B and the reference distance mo.
In the state of FIG. 9B described above, the reference position 01 ′ of the first hologram optical system HS1 is moved from the original reference position 01 by the distance T due to the movement of the distance T.
Here, the reference deviation amount δ described above is generated between the reference position 01 ′ of the first hologram optical system HS1 and the reference position 02 of the second hologram optical system HS2.
Therefore, the measured position D2 = D1−mo−δ, and the reference deviation amount δ = D1−D2−mo can be calculated.

Through the above-described steps ST1 to ST4, the reference deviation amount δ generated between the first hologram optical system HS1 and the second hologram optical system HS2 is measured.
Then, the following steps ST5 to ST7 are performed in order to sequentially measure the dimensions of the block gauges 2B of the step gauge 2, which is the original measurement object, using the measured reference deviation amount δ.

  Among these, the steps ST5 to ST6 related to each block gauge 2B are performed by, for example, individually selecting the block gauge 2B from one end side of the step gauge 2 that is a measurement object, and executing the steps ST5 to ST6 for the selected block gauge 2B. Can do. When all the block gauges 2B have been measured, the desired dimensions or gaps can be calculated in step ST7.

  The object measurement step ST5 is a step of measuring a distance while sequentially positioning the first measurement surface 2F and the second measurement surface 2S of each block gauge 2B of the step gauge 2 that is a measurement object.

First, as shown in FIG. 5, the first measurement surface 2F of the current block gauge 2B having the unknown dimension Mi selected as the measurement target is arranged on the detection surface D. Then, the position of the first measurement surface 2F is detected by the first hologram optical system HS1.
Similarly, in FIG. 9A, when the first measurement surface 2F is on the detection surface D, the distance L1 from the reference position 01 of the first hologram optical system HS1 is measured by the laser interference length measuring machine 7, This is the actual measurement position L1 of the step gauge 2 on the first measurement surface 2F of the current block gauge 2B.

Subsequently, as shown in FIG. 6, the second measurement surface 2 </ b> S of the current block gauge 2 </ b> B of the step gauge 2 that is the measurement object is arranged on the detection surface D. Then, the position of the second reference surface 2S is detected by the second hologram optical system HS2.
9B, in order to place the second measurement surface 2S on the detection surface D, the current block gauge 2B is moved along the longitudinal direction E by a distance T = Mi.

When the second reference surface 2S is on the detection surface D, the laser interferometer 7 measures the distance L2 from the reference position 02 of the second hologram optical system HS2, which is the second measurement surface 2S of the current block gauge 2B. The actual measurement position L2 in the step gauge 2 is.
In the present embodiment, since the detection surface distance is 0, the actual measurement distance dL = L1-L2 from the measured positions L1 and L2 to the second measurement surface 2S of the current block gauge 2B from the first measurement surface 2F. Can be sought.

  In the object distance correcting step ST6, the actual measured distance dL of the current block gauge 2B is corrected by the reference deviation amount δ, and the accurate distance dL− from the first measurement surface 2F to the second measurement surface 2S of the current block gauge 2B is corrected. This is a step of calculating δ. That is, in order to obtain the current dimension Mi of the block gauge 2B, dL−δ may be calculated. Since dL−δ = L1−L2−δ = Mi, the current dimension Mi of the block gauge 2B is obtained.

By repeating the above steps ST5 and ST6, the position L1 of the first measurement surface 2F, the position L2 of the second measurement surface 2S, the measured distance dL, and the dimension Mi = dL for all the block gauges 2B of the step gauge 2. -Δ is obtained.
The dimension Mi of each block gauge 2B in the step gauge 2 has already been obtained, but each pitch and gap are calculated in the next calculation step ST7.

In the calculation step ST7, the pitch of each block gauge 2B can be calculated by taking the difference sequentially with respect to the position L1 of the first measurement surface 2F of each block gauge 2B.
Further, the gap between two adjacent block gauges 2B can be calculated by subtracting the dimension Mi of each block gauge 2B from the calculated pitch of each block gauge 2B.

In the calculation step ST7, with respect to the gap between two adjacent block gauges 2B, from the position L2 of the second reference surface 2S of any block gauge 2B to the position of the first reference surface 2F of the adjacent block gauge 2B facing this. It can also be calculated by subtracting L1.
Furthermore, in the calculation step ST7, the statistical processing may be performed on the calculated dimensions Mi, pitch, and gap.

In this embodiment, the following effects can be obtained.
In the present embodiment, the first measurement surface 2F in each block gauge 2B of the step gauge 2 that is the measurement object is prepared by performing the preparation process ST1 and the reference hologram production process ST2 and then performing the object measurement process ST5. The positions L1 and L2 and the distance dL of the second measurement surface 2S (first target surface and second target surface) can be measured.

  Here, only by executing the object measurement step ST5 following the preparation step ST1 and the reference hologram production step ST2, the first hologram optical system HS1, the second hologram optical system HS2, and the measurement error factor in the object measurement step ST5 The amount of deviation occurs with respect to the distance that is the original measurement result.

On the other hand, in this embodiment, the reference deviation amount δ is calculated by performing the reference measurement step ST3 and the reference deviation amount measurement step ST4 similar to the object measurement step ST5 in advance.
That is, any one of the block gauges 2B of the step gauge 2 as a measurement object is set as a reference measurement object, and the reference distance mo measured with high accuracy is referred to, and the first reference surface 2F of the block gauge 2B serving as a reference is used. By executing the reference measurement step ST3 on the second reference surface 2S, the positions D1 and D2 of the reference object and the measurement distance dD are obtained. Then, the reference deviation amount δ can be calculated by performing the reference deviation amount measurement step ST4.

  The reference deviation amount δ thus obtained is common to the reference actual measurement step ST3 and the target actual measurement step ST5 due to the measurement error factors in the first hologram optical system HS1 and the second hologram optical system HS2 and the target actual measurement step ST5. Therefore, by correcting the measured distance dL obtained in the object measuring step ST5 by this reference deviation amount δ, an accurate distance that does not include the deviation amount ( The dimension Mi) can be calculated.

  As described above, according to the non-contact distance measuring method of the present embodiment, a plurality of first target surfaces and second target surfaces (first measurement surface 2F and second measurement surfaces) that are arranged in the step gauge 2 that is a measurement target and are opposite to each other. The position of the second measurement surface 2S) can be measured with high accuracy and efficiency using holographic interference.

In the present embodiment, the first holographic optical system HS1 and the second holographic optical system HS2 are common detection surfaces D in which the respective detection surfaces are set to the same plane.
For this reason, the distance between the detection surfaces of the first hologram optical system HS1 and the second hologram optical system HS2 is 0, and the calculation procedure can be omitted.

  Further, since the common detection surface D is used, in the reference actual measurement step ST3 and the object actual measurement step ST5, a block gauge 2B (between the measurement by the first hologram optical system HS1 and the measurement by the second hologram optical system HS2) As the movement distance T of the reference object or measurement object, the reference distance mo of the reference object can be used as it is.

Furthermore, in the present embodiment, the first hologram optical system HS1 and the second hologram optical system HS2 are arranged symmetrically with respect to the common detection surface D, and the same optical elements and optical paths are used as the light sources. The laser light source 610 is used.
For this reason, the first hologram optical system HS1 and the second hologram optical system HS2 have symmetry and the measurement conditions are equalized, whereby the measurement results of the optical systems HS1 and HS2 can be equalized.

[Second Embodiment]
10 and 11 show a second embodiment of the present invention.
In the first embodiment described above, in the laser interference length measuring machine 7 of the step gauge measuring apparatus 1, the light projecting unit 71, the light receiving unit 72, and the three reflecting mirrors 73, 74, and 75 are used.

  In the laser interference length measuring machine 7 according to the first embodiment, the optical path from the light projecting unit 71 to the reflecting mirror 73 and the optical path from the reflecting mirror 74 to the light receiving unit 72 are subject to length measurement. The height of the block gauge 2B and the measurement surface 2S is maintained. With such a configuration, the error can be suppressed by bringing the measurement axis close to each other, and the error based on the posture change of the step gauge 2, particularly yawing can be eliminated.

Further, the length of the optical path from the reflecting mirror 73 to the reflecting mirror 74 through the reflecting mirror 75 and the length of the reciprocating virtual optical path from the point N shown in FIG. 2 to the point M on the measuring surface 2S to be measured are shown. , Are set to match. Thereby, an optical path equivalent to reflecting the laser beam at the point M on the measurement surface 2S can be secured.
On the other hand, in the laser interferometer 7A of this embodiment, the light path configuration is simplified by using the light projecting unit 71, the light receiving unit 72, and the two reflecting mirrors 73 and 74.

  In FIG. 10, the laser interference length measuring machine 7 </ b> A is measured by the non-contact positioning device 6 with the measurement surfaces 2 </ b> F and 2 </ b> S (the first measurement surface 2 </ b> F and the second measurement surface) similarly to the laser interference length measuring device 7 of the first embodiment described above. Any one of the surfaces 2S) and the measuring head 4 are positioned under the same conditions, and the position of the measuring head 4 is measured with high accuracy, so that the dimensions, gaps, or gaps of the block gauges 2B arranged in the step gauge 2 The pitch can be measured with high accuracy.

The light projecting unit 71 and the light receiving unit 72 are installed at both ends of the installation table 33 of the moving device 3, and move together with the moving table 31 and the step gauge 2 held by the moving table 31. The light projecting unit 71 and the light receiving unit 72 are installed on the installation table 33, and are installed on the opposite side of the same distance across the movable table 31. With such an optical path configuration, even if a yawing error occurs in the moving device 3 and the step gauge 2 during length measurement, this can be canceled out.
The two reflecting mirrors 73 and 74 are respectively fixed to the measuring head 4 and allow relative distance changes between the light projecting unit 71 and the light receiving unit 72.

The reflecting mirrors 73 and 74 are respectively arranged on the opposite sides with the moving device 3 interposed therebetween.
At this time, the reflecting mirrors 73 and 74 are supported at a position higher than the step gauge 2, and are arranged so that the optical path between the reflecting mirrors 73 and 74 does not interfere with the block gauge 2B or the like.

  In addition, the light projecting unit 71 and the light receiving unit 72 are also mounted on the installation stand and fixed to a common substrate with the step gauge 2 at a height corresponding to the reflecting mirrors 73 and 74, and from the light projecting unit 71 to the reflecting mirror 73. The optical paths between the reflecting mirror 74 and the light receiving unit 72 are parallel to the longitudinal direction E of the step gauge 2 (the arrangement direction of the block gauges 2B).

The positions and postures of the light projecting unit 71, the light receiving unit 72, and the reflecting mirrors 73 and 74 are adjusted so as to form the following optical path.
As shown in FIGS. 11A and 11B, the laser light emitted from the light projecting unit 71 travels along the longitudinal direction E of the step gauge 2 held by the moving device 3, and the reflecting mirror 73. Is incident on. The laser light reflected by the reflecting mirror 73 changes its direction in the orthogonal direction and crosses the upper side of the step gauge 2 and enters the reflecting mirror 74. The laser light reflected by the reflecting mirror 74 travels in the opposite direction along the longitudinal direction E of the step gauge 2 held by the moving device 3 and is received by the light receiving unit 72.

  In the laser interference length measuring instrument 7A having such an optical path, the distance between the light projecting unit 71 and the reflecting mirror 73, which is a section along the longitudinal direction E of the step gauge 2, by the movement of the moving table described above and The optical path length from the reflecting mirror 74 to the light receiving unit 72 changes. Therefore, the measurement laser beam received by the light receiving unit 72 is caused to interfere with the reference laser beam sent directly from the light projecting unit 71 to the light receiving unit 72, thereby measuring the displacement of the moving table 31, and measuring the measurement head 4. The distance can be measured.

  Further, as shown in FIGS. 11A and 11B, the reflection positions of the reflecting mirrors 73 and 74 are point A and point C, and the midpoint of the line segment connecting point A and point C is point N, If the longitudinal direction E-axis line position of the step gauge 2 is the point M and the point N ′ at the same height as the measurement surfaces 2F and 2S (in FIG. 11, the measurement surface 2S is illustrated), the length of the line segment AN and the line segment NC Is 2D, and the reciprocation length of the line segment MN ′ is also 2D. This is based on the optical properties of right-angled mirrors such as the reflecting mirrors 73 and 74.

  Thus, using the two reflecting mirrors 73 and 74 as described above, an optical path equivalent to reflecting the laser beam at the point M on the measurement surfaces 2F and 2S (from the point M on the measurement surfaces 2F and 2S is stepped). An optical path equivalent to the distance to the light projecting unit 71 and the light receiving unit 72 along the longitudinal direction of the gauge 2 can be ensured.

  In the first embodiment described above, the step gauge 2 is straddled by the three reflecting mirrors 73, 74, 75, so that the optical path from the light projecting unit 71 to the reflecting mirror 73 and from the reflecting mirror 74 to the light receiving unit 72 are performed. Can be maintained at the heights of the block gauge 2B and the measurement surfaces 2F and 2S, which are the objects of length measurement, respectively, and the posture change, particularly the pitching error and yawing error of the step gauge 2 are eliminated. .

On the other hand, in this embodiment, yawing errors on the measurement surfaces 2F and 2S can be eliminated, but pitching errors may occur.
That is, in the present embodiment, the optical path between the light projecting unit 71 and the reflecting mirror 73 and the optical path between the reflecting mirror 74 and the light receiving unit 72 are set at positions higher than the step gauge 2, and therefore the measurement axis line May be offset by a height h, resulting in a pitching error.

However, with respect to the pitching error, the influence can be sufficiently eliminated by designing the offset amount of the height h to be small in advance and increasing the substrate rigidity of the entire apparatus including the moving apparatus 3.
Therefore, according to this embodiment, the same effect as that of the first embodiment described above can be obtained.

[Modification]
It should be noted that the present invention is not limited to the above-described embodiment, and modifications and the like within a scope that can achieve the object of the present invention are included in the present invention.
In each of the embodiments described above, the application object of the present invention is the step gauge measuring device 1, and in the step gauge 2 which is a long reference device, each of the first measurement surface 2F and the second measurement surface 2S of each block gauge 2B. The actual measurement positions L1 and L2 were measured with high accuracy, and the dimensions Mi and gaps of the respective block gauges 2B were calculated.

  However, in the present invention, in addition to a reference device in which a large number of pairs of measurement surfaces 2F and 2S are arranged at a desired pitch, such as a step gauge 2, for example, a large number of pairs of tooth surfaces are at a desired pitch. Measuring devices for measuring objects in which a large number of pairs of measuring surfaces are arranged, such as arranged racks, screws, ball screws, and many similar pairs of surfaces, coils and other members arranged at the desired pitch It can also be applied to.

  The present invention relates to a non-contact distance measuring method and can be used as a method for measuring a distance between two surfaces having different directions with high accuracy without contact.

1 ... Step gauge measuring device (non-contact distance measuring device)
2 ... Step gauge (object to be measured)
2B ... Block gauge (measurement object and reference object)
2F ... 1st reference surface or 1st measurement surface (1st object surface)
2H: Gauge holder 2S: Second reference surface or second measurement surface (second target surface)
DESCRIPTION OF SYMBOLS 3 ... Moving device 31 ... Moving stand 32 ... Base stand 33 ... Installation stand 4 ... Measurement head 41 ... Plate 42 ... Extension plate 5 ... Head mechanism 6 ... Non-contact positioning device 61 ... Projection device 610 ... Laser light source 611 ... Right angle prism 612... Reflecting mirrors 613 and 614... Beam splitter 615. Reflecting mirrors 616 to 619, 622 and 625... Lens 62 .. Photodetecting devices 621 and 624 .. Recording medium 623 and 626. , 7A ... Laser interferometer 71 ... Projection unit 72 ... Light receiving unit 73, 74, 75 ... Reflector 8 ... Control device D ... Detection surface D1 ... First reference surface measurement position D2 ... Second reference surface measurement Position dD: Actual distance T between the first reference surface and the second reference surface .... Moving distance L1 of the step gauge 2 .... Measurement position L2 on the first measurement surface ... Measurement position dL on the second measurement surface.・ ・First measuring surface and the actual distance E ... longitudinal direction between the second measuring surface (array direction)
H1 ... 1st hologram H2 ... 2nd hologram HS1 ... 1st hologram optical system HS2 ... 2nd hologram optical system Lo, L1, L2 ... Laser beam L1R, L2R ... Laser beam (reference beam)
L1S, L2S ... Laser light (signal light)
LF, LFS, LS, LSS... Laser beam mo... Reference dimension mc of reference block gauge 2B... Calculated reference dimension of block gauge 2B Mi... Calculated current block gauge 2B dimension P1. Generation surface P2 ... second generation surface RH1 ... first reference hologram RH2 ... second reference hologram S1, S2 ... light intensity signal ST1 ... preparation step ST2 ... reference hologram production step ST3 ... reference measurement step ST4 ... reference deviation amount measurement step ST5 ... Object measurement step ST6 ... Object distance correction step ST7 ... Calculation step δ ... Reference deviation amount

Claims (3)

A non-contact distance measuring method for measuring a distance between a first target surface and a second target surface opposite to each other formed on a measurement object in a non-contact manner,
As a preparatory step, a reference object that is used as a reference for the measurement object and whose reference distance between the first object surface and the second object surface is measured with high accuracy is disposed opposite to each other and each detection is performed Preparing a non-contact distance measuring device having a first hologram optical system and a second hologram optical system whose surfaces are arranged at a predetermined detection surface distance;
As a reference hologram production step, the reference object is mounted on the non-contact distance measuring device, the first object surface of the reference object is arranged on the detection surface of the first hologram optical system, and a first reference hologram is formed. The second reference hologram is produced by moving the reference object mounted on the non-contact distance measuring device and placing the second object surface of the reference object on the detection surface of the second hologram optical system. Made,
As a reference actual measurement step, the reference object is mounted on the non-contact distance measuring device, the first object surface of the reference object is disposed on a detection surface of the first hologram optical system, and the first reference hologram and The position of the first target surface is measured by hologram interference of the reference object, the reference object mounted on the non-contact distance measuring device is moved, and the second target surface of the reference object is moved to the second hologram optical system. The position of the second target surface is measured by hologram interference with the second reference hologram, the measured positions of the first target surface and the second target surface, and the detection surface distance By measuring the measured distance between the first target surface and the second target surface of the reference object,
As a reference deviation amount measuring step, a reference deviation amount is calculated from a difference between an actually measured distance of the reference object and the reference distance,
In the object measurement step, the measurement object is mounted on the non-contact distance measuring device, the first object surface of the measurement object is disposed on the detection surface of the first hologram optical system, and the first reference hologram The position of the first target surface is measured by the hologram interference with the non-contact distance measuring device, the measurement target mounted on the non-contact distance measuring device is moved, and the second target surface of the measurement target is moved to the second hologram optics. The position of the second target surface is measured by hologram interference with the second reference hologram, the position of the first target surface and the second target surface measured, and the detection surface By measuring the distance, the measured distance between the first target surface and the second target surface of the measurement object is measured,
Non-contact distance characterized in that, as the object distance correction step, the distance between the first object surface and the second object surface of the measurement object is calculated from the measured distance of the measurement object and a reference deviation amount. Measuring method. In the non-contact distance measuring method according to claim 1,
In the non-contact distance measuring method of the present invention, the first hologram optical system and the second hologram optical system are common detection surfaces in which the detection surfaces are set to the same plane, and the detection surface distance is zero. A non-contact distance measuring method, characterized in that: In the non-contact distance measuring method according to claim 2,
In the first hologram optical system and the second hologram optical system, the optical elements and the optical paths are arranged symmetrically with respect to the common detection surface, and the same laser light source is used as the light source. A characteristic non-contact distance measuring method.

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