JPH1062136A - Method and device for shape measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the adjustment of the angle of a base to the orientation of gravity as desired with keeping the positional relationship between a shape measuring device and an object to be measured by providing a gravitational orientation detecting means and angle adjusting mechanism for the base on which the object to be measured and shape measuring device are mounted. SOLUTION: A vibration removing base 8, on which e.g. an interferometer 3 as a shape measuring device, an object to be measured 5, and e.g. a prism 7 as a gravitational direction detecting device are mounted, comprises legs 13, a pneumatic spring 11, surface plate 9, etc., and is provided on a floor 15. The pneumatic spring 11 may double as an angle adjusting mechanism of the surface plate 9 by adjusting the amount of air to fill. A piezo actuator e.g. may be also used as an angle adjusting mechanism. The prism 7 reflects light emitted from a theodolite 17 mounted on the base 19, and the orientation of gravity is detected from the displacement of light between emitted light and reflected light. By the above-mentioned arrangements, it is possible to set the angle of the orientation of measurement to gravity as desired and, with feedback control, it is possible to adjust automatically to an set angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape measuring method and a shape measuring apparatus suitable for performing a measurement with an optical axis of a measurement set at an arbitrary angle with respect to gravity, for example, in interference measurement.

[0002]

2. Description of the Related Art An example of interference measurement will be described. When an interference light is emitted in a direction perpendicular to the gravity and the measurement is performed with the test surface set up, usually, the rigidity of the lens or mirror according to the diameter of the test surface is adjusted to avoid deformation of the test surface due to gravity. thickness)
Is set. Furthermore, in order to avoid deformation due to holding (holding) of the test surface, attention was paid to the holding method.

[0003]

However, there are many cases where the thickness required to prevent deformation cannot be ensured, and the method of holding the surface is limited depending on the shape of the surface to be inspected. In this case, the amount of deformation of the test surface can be predicted by simulation (calculation by the finite element method) or the like, but the calculation may be insufficient. Also,
If the amount of deformation is predicted by simulation and corrected, it cannot be said that it is a true inspection. Regarding the deformation of the test surface due to gravity, the inclination of the test surface with respect to gravity during measurement is important, and depending on the relationship between the shape and thickness of the measurement object, deformation that cannot be ignored even with a tilt of several seconds. May also occur.

[0004] Even if an angle with respect to gravity can be set under certain conditions, a general anti-vibration table or the like tilts when a load is applied, so that the reproducibility of the angle in units of seconds can be obtained. There are few things.

Therefore, the present invention provides a measuring method and apparatus which can set the angle of the optical axis of the interferometer with respect to gravity, for example, vertically or horizontally, or arbitrarily, and can maintain the set angle and easily change it. The purpose is to provide. Further, it is another object of the present invention to provide a shape measuring method and a shape measuring device capable of strictly reproducing a use state of a measuring object and evaluating a shape.

[0006]

In order to solve the above-mentioned problems, a shape measuring method according to the present invention is a method for measuring the shape of an object based on the principle of interference or the like. The shape is measured after the posture of the measuring instrument and the object to be measured is arbitrarily adjusted with respect to the direction of gravity while holding.

Further, the shape measuring apparatus of the present invention comprises a base on which an object to be measured and a shape measuring instrument are mounted, a shape measuring instrument placed on the base, an angle adjusting mechanism of the base, a gravitational direction detecting means, The angle of the base with respect to the direction of gravity can be adjusted arbitrarily while maintaining the relative positional relationship between the measuring instrument and the object to be measured.

[0008] In the case of interferometer measurement, for example, by adjusting the angle of the anti-vibration table (base), the anti-vibration table can be set at an arbitrary angle with respect to gravity regardless of the level of the floor where the measuring instrument is installed. Can be set. However, at this time, it is necessary to detect the direction of gravity by some means. The angle may be adjusted by adjusting an air spring provided in the vibration isolation table or the like, or by using some other method (such as a piezo actuator).

As the means for detecting the direction of gravity, an equipment for construction such as a theodolite (level) may be used. When it is desired to detect the direction of gravity with higher accuracy, the reflection of the laser from a liquid surface such as mercury may be observed, or the liquid surface may be measured with an interferometer or the like.

However, as described above, for example, when a load is applied to the vibration isolation table or when the load fluctuates, before and after the load is applied (before and after the change), the angle with respect to the initially set gravity is set. Is not always reproduced. As a solution, the simplest method is to make the sensitivity of the air spring of the vibration isolation table more sensitive. However, in this case, the natural frequency of the anti-vibration table may be a problem. Therefore, the angle of the anti-vibration table with respect to gravity is always or appropriately detected, and based on the detected result, the angle adjustment mechanism attached to the apparatus is feedback-controlled to more reliably set an arbitrary set angle. It is possible to always maintain. Further, by applying the feedback, it is possible to easily change the set angle itself.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a side view showing a shape measuring apparatus according to one embodiment of the present invention. The shape measuring apparatus 1 of FIG. 1 is configured based on a vibration isolation table 8. That is, on the vibration isolation table 8,
The interferometer 3, the measurement object 5, and the prism 7 are placed. The interferometer 3 incorporates a laser oscillator, an interference optical system, an imaging optical system, and the like, which are interference light sources. The parallel light beam 4 that has exited the interferometer 3 is reflected on the surface 5a of the measurement object 5 and returns to the interferometer 3 to form interference fringes. The test surface 5 a is basically orthogonal to the light beam 4. The prism 7 will be described later.

The anti-vibration table 8 includes legs 13, an air spring 11, a surface plate 9, and the like, and is installed on a hard and stable floor 15. The air spring 11 is mounted on the legs 13 and supports the platen 9. The air spring 11 is a platen 9
Angle adjustment mechanism. By adjusting the amount of air to be charged into the air spring 11, the angle of the platen 9 can be set to 10 degrees.
Can be adjusted in seconds. The platen 9 is a rigid plate having high rigidity.

A prism 7 is mounted on the right end of the upper surface of the surface plate 9. The prism 7 has a very good perpendicularity between the lower surface and the reflection surface. Opposing the prism 7,
A theodolite (level) 17 is provided. Theodolite 17 is placed on another stand 19, not on the surface plate 9. The light that has exited the theodolite 17 strikes the prism 7 and is reflected back to the theodolite 17, where the difference between the emitted light and the reflected light is detected to detect the levelness of the prism 7 mounting surface.
1, the prism 7 and the theodolite 17 form a gravitational direction detecting unit. The detection accuracy of the theodolite 17 is as good as several seconds.

FIG. 2 is a side view of a shape measuring apparatus (two-stage type) according to another embodiment of the present invention. The difference between the shape measuring device of FIG. 2 and the shape measuring device of FIG. 1 is that an upper surface plate 23 and a piezo-actuator type angle adjusting mechanism 25 are installed on the vibration isolation table 8 (two-stage stacking type). ). A plurality of piezo actuators 25 are placed on the vibration isolation table 8, and the precise extension and contraction of the piezo actuators 25 enables precise control of the angle of the upper platen 23 with respect to the horizontal.

FIG. 3 is a side view of a shape measuring apparatus (feedback control type) according to another embodiment of the present invention. FIG.
The mechanical configuration of the shape measuring device is the same as that of the shape measuring device of FIG. However, a feedback circuit 33 is incorporated in the control mechanism, and the platen 2 detected by the gravity direction detecting means (prism 7, theodolite 17).
The angle with respect to the gravitational direction 3 is fed back to the angle adjusting mechanism 25 to adjust the angle of the surface plate 23 to an arbitrarily set angle. This feedback can be performed at all times or appropriately (when the load changes). The automatic adjustment of the angle may use the air spring 25 of the vibration isolation table 8.

FIG. 4 is a side view showing a shape measuring apparatus (liquid level detection type) according to another embodiment of the present invention. The difference between the shape measuring device of FIG. 4 and the shape measuring device of FIG. 3 is that the gravity direction detecting means is based on the liquid surface. That is, a container 51 is provided at the right end of the upper surface of the upper surface plate 23.
A liquid 49 such as mercury that has entered is placed. This liquid surface 49a is used as a reference plane orthogonal to the earth's gravity.

When detecting the direction of gravity, the swing mirror 43 between the interferometer 3 and the measuring object 5 is lowered (at the position indicated by the solid line), and the interference light beam 4 is bent upward (light beam 4 ').
The light is reflected 180 ° by the liquid surface 49a after being oriented by 5 and 47, and is returned to the interferometer 3 again by the mirrors 47, 45 and 43 to form interference fringes. The liquid surface 49a follows the direction perpendicular to the earth's gravity regardless of the inclination of the upper surface of the platen 23. Therefore, when the horizontality of the upper surface plate 23 changes, the angle of the liquid surface 49a with respect to the interference light beam 4 'changes, which can be detected.

FIG. 5 is a side view showing a shape measuring apparatus (object to be measured) according to another embodiment of the present invention. FIG.
2 differs from the shape measuring device of FIG. 2 in that the measuring object itself is used as a part of the gravitational direction detecting means. That is, the spherical lens 5 'of the measurement object
Is used as a reference plane in the direction of gravity. Here, a Fizeau lens 3a having a spherical reference surface 3b is attached to the tip of the interferometer 3, and the reference surface 3b and the spherical test surface 5a of the spherical lens 5 'interfere with each other.

When the back surface 5b of the test surface 5a is flat,
By directly measuring the back surface 5b with the theodolite 17, the angle of the test object 5 'with respect to the direction of gravity can be adjusted ignoring errors due to the components of the apparatus. However, although the eccentricity of the test object remains as an error, it can be dealt with by measuring the eccentricity by another method and feeding back its direction and angle.

[0020]

As described above, according to the present invention, in an interferometer measurement or the like, the angle relationship between the measurement optical axis direction and the gravity direction can be arbitrarily set, and the angle can be easily maintained and changed. It becomes possible. Further, by using the present measuring method and apparatus, it is possible to perform interferometer measurement on a liquid surface.

[Brief description of the drawings]

FIG. 1 is a side view showing a shape measuring apparatus according to one embodiment of the present invention.

FIG. 2 is a side view of a shape measuring apparatus (two-stage type) according to another embodiment of the present invention.

FIG. 3 is a side view of a shape measuring apparatus (feedback control type) according to another embodiment of the present invention.

FIG. 4 is a side view showing a shape measuring apparatus (liquid level reference type) according to another embodiment of the present invention.

FIG. 5 is a side view showing a shape measuring apparatus (measurement target reference type) according to another embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 shape measuring device 3 interferometer 3a Fizeau lens 3b reference surface 4 luminous flux 5 measurement object 5a test surface 5b back surface 7 prism 8 anti-vibration table 9 surface plate 11 air spring 13 legs 15 floor 17 theodolite 19 tables 21 shape measuring device 23 Top platen 25 Precision piezo actuator (angle adjustment mechanism) 31 Shape measuring device 33 Feedback circuit 41 Shape measuring device 43 Swing mirror 45 Mirror 47 Mirror 49 Liquid (mercury) 49a Surface

Claims (3)

[Claims] 1. A method for measuring the shape of an object based on the principle of interference or the like, wherein the attitude of the measuring instrument and the object to be measured with respect to the direction of gravity is maintained while maintaining the relative positional relationship between the measuring instrument and the object to be measured. A shape measuring method characterized by arbitrarily adjusting the shape and measuring the shape. 2. A base on which a measuring object and a shape measuring instrument are mounted, a shape measuring instrument placed on the base, an angle adjusting mechanism of the base, and a gravity direction detecting means; A shape measuring apparatus characterized in that the angle of the base with respect to the direction of gravity can be arbitrarily adjusted while maintaining the relative positional relationship between objects. 3. An arithmetic processing of the gravity direction detected by the gravity direction detecting means, and the arithmetic processing is fed back to the angle adjusting mechanism so that the base is always maintained at a constant angle with respect to the gravity direction. 3. The shape measuring device according to claim 2, further comprising a feedback circuit for changing the angle.