JPH07167634A - Probe for measurement and displacement gage with the probe - Google Patents

Abstract

PURPOSE:To measure the shape of the internal surface of a cylindrical article to be measured having a small inside diameter with high accuracy. CONSTITUTION:A probe 50 for measurement is composed of a cylindrically formed main body 6 and a parabolic mirror 5 being installed at one end of the main body 6 and deflecting measuring beams passing through a cylinder and being changed into parallel luminous flux in the orthogonal direction while focusing beams so as to be focalized 7 in the direction of deflection. The probe 50 for measurement irradiates a surface to be measured with measuring beams while receiving reflected beam from the surface to be measured, and is used for a displacement gage for a shape measuring device measuring the shape of the article to be measured 13 in a non-contact manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is installed in a non-contact type shape measuring device for measuring the shape, waviness, roughness, etc. of an optical element with high accuracy and measures the distance to the surface to be measured of the optical element. The present invention relates to a measurement probe used for a displacement meter.

[0002]

2. Description of the Related Art Recently, in the field of observation and measurement, high resolution,
The demand for high precision is increasing. Therefore, high precision is also required for optical elements used in the optical systems of observation devices and measurement devices used in these fields.
Then, X-rays having a wavelength extremely shorter than that of visible light are used as light (electromagnetic waves) suitable for observing a sample with high resolution. However, X-rays hardly refract because X-rays have a refractive index of a substance close to 1, and optical elements (for example, lenses) that utilize refraction such as visible light cannot be used. Therefore, an optical element utilizing reflection is used, but even in that case, it is limited to an element which totally reflects in an oblique incidence arrangement in which X-rays are incident just on the reflection surface. Therefore, an X-ray optical element having a reflecting surface formed in a special shape is often used. As a type of such an X-ray optical element, for example, a Walter type optical element is known.
The Wolter type optical element uses a cylindrical inner surface with a small inner diameter as an optical surface (reflection surface), and the reflection surface is formed by two curved surfaces of a rotating hyperboloid and a rotating ellipsoid which are coaxially connected. There is.

By the way, an X-ray optical element used in an X-ray optical system is required to have a very high accuracy as compared with a general optical element because the wavelength of X-ray is short. Therefore, for these X-ray optical elements that require high accuracy, the shape of the reflecting surface (including undulations and roughness) must be measured with high accuracy in order to confirm that the shape after fabrication is as designed. Has become essential. A shape measuring device is used for measuring the shape. This shape measuring device has a displacement gauge equipped with a measuring probe, and measures the distance between a plurality of measurement points (measurement surface) and a reference point on an object to be measured (optical element) by the displacement meter. By going through, the shape of this measured object is obtained. The measurement probe is used to determine whether or not the measurement point of the object to be measured, a contact type measurement probe for contacting the measuring surface with a spherical or needle-shaped probe, or light reflected by the surface to be measured. An optical non-contact measuring probe using a defocusing method for detecting or an interferometer method is used. But,
Many of the X-ray optical elements are small, and for example, the above-mentioned Walter type X-ray optical element is usually manufactured with an inner diameter of about 5 to 15 mm. Therefore, if the inner surface of the cylinder is used as a reflecting surface as in this Wolter type X-ray optical element, a commonly used optical non-contact measurement probe cannot be inserted inside the cylinder because it is too large to measure the shape. Can not. Therefore, conventionally, as shown in FIG. 3, a contact-type measuring probe having an elongated arm 20 having a spherical measuring element 19 formed at its tip has been used. At the time of measurement, this arm 20 was inserted inside the cylindrical portion of the optical element 13 and the probe 19 at the tip was brought into contact with the inner surface of the optical element 13 to measure the shape of the reflective surface of the element.

[0004]

However, when an optical element is measured using the contact type measurement probe, the probe of the measurement probe and the optical surface (reflection surface) of the optical element come into contact with each other, and the optical surface is scratched. There was a phenomenon of getting stuck. For example,
In the X-ray optical element, a reflection film such as a nickel (Ni) coat is provided on the optical surface, but if the optical surface is scratched, the optical performance deteriorates and desired performance cannot be obtained. for that reason,
The shape of the reflecting surface was measured before the nickel coat was formed, and the quality of the shape was evaluated. However, even if the measurement result of the element before forming the reflection film is as designed, the shape may change due to the formation of the reflection film, and there is a problem that an accurate shape cannot be measured. It was

Further, since the measuring element is provided at the tip of the elongated arm, the rigidity of the measuring probe is weak, and the arm is deformed due to the contact pressure (measuring pressure) with the optical element, or the vibration transmitted from the surroundings causes There is also a problem that the measurement result is adversely affected. Furthermore, when it is necessary to rotate the optical element, such as when measuring the roundness, the measurement probe is pulled in the rotation direction due to the friction between the measurement probe and the measurement surface, which adversely affects the measurement accuracy. There was also a problem.

The present invention aims to solve such a problem.

[0007]

To achieve the above object, the present invention uses a displacement meter for measuring the distance to a measurement point of an object to be measured in a non-contact manner. A measuring probe for receiving reflected light from the measuring point is provided with a main body formed in a cylindrical shape, and a parallel luminous flux which is installed at one end of the main body and which has passed through the inside of the cylinder is orthogonalized. And a parabolic mirror for converging light so as to focus the light in the deflection direction.

[0008]

In the measuring probe of the present invention, the measuring light, which has been converted into a parallel light flux, is deflected by a parabolic mirror in a direction orthogonal to the parabolic mirror and is condensed so as to be focused in the deflecting direction.
Therefore, it is possible to satisfy both the deflection function of directing the measurement light to the measurement point of the element by the parabolic mirror and the light condensing function of condensing the measurement light on the measurement point. That is, if the measurement light is reflected with the position of the focal point as a measurement point, the measurement light converted into a parallel light flux entering the inside of the cylindrical optical element having a small inner diameter from the longitudinal direction ( It is reflected at the measurement point) and returns again as a parallel light beam. Therefore, the measuring probe of the displacement gauge can be composed of only the parabolic mirror and the main body holding the parabolic mirror. Compared with the case where the same optical system is configured by combining a plane mirror and a lens, the number of optical components is one, so the optical system is simple and compact. The parabolic mirror itself can be miniaturized so that it can be inserted into a cylinder having an inner diameter of about 5 to 15 mm like the above-mentioned Walter type X-ray optical element, and the probe itself can be miniaturized. is there. The size of the focal point of the parabolic mirror can be reduced to about several μm. Since the measuring probe of the present invention does not contact the measuring point of the object to be measured, it does not damage the optical surface (reflection surface) of the element when measuring the distance to the measuring point. Moreover, since the influence of disturbance such as vibration can be suppressed, the measurement accuracy is improved as compared with the conventional case.

[0009]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the present invention, showing the construction of a displacement gauge equipped with the measuring probe of the present invention. FIG. 2 is an enlarged view near the parabolic mirror 5 in FIG. The displacement meter of the present embodiment includes a light source 1 for emitting a laser beam converted into a parallel light flux, a polarization beam splitter 2 for splitting the laser beam into a measuring light 3a and a reference light 3b, an optical path of the measuring light 3a and the reference light 3b. Λ / 4 wave plates 4 respectively arranged in
A measurement probe 50 that irradiates the inner surface (measurement surface) of the optical element 13 with the measurement light 3a and receives reflected light from the measurement surface, a reference surface 9 that reflects the reference light 3b, and a reference by the polarization beam splitter 2. A detector 10 for detecting the interference light between the reflected light from the surface 9 and the reflected light from the surface to be measured, and a calculation means for obtaining the distance to the surface to be measured based on the detection result of the detector 10. And). The measurement probe 50 is composed of a main body 6 formed in the shape of a hollow pipe and a parabolic mirror 5 installed at one end of the main body 6. The parabolic mirror 5 was obtained by cutting aluminum plated with nickel with a diamond cutting tool and polishing the reflecting surface. During polishing, the surface roughness was adjusted to 0.1 μm or less. The diameter of the hollow portion of the main body 6 was 4 mm.

In the displacement meter having such a configuration, the measuring light beam generated from the light source 1 and converted into a parallel light beam is split by the polarization beam splitter 2 into a measuring light beam 3a and a reference light beam 3b. After passing through the λ / 4 wavelength plate 4, the measurement light 3a passes through the inside of the main body 6 of the measuring probe 50 and is incident on the reflecting surface of the parabolic mirror 5. Then, the light is reflected by the reflecting surface, bent at a right angle, and at the same time, the focal point 7 is formed and enters the inner surface (measurement surface) of the optical element 13. The measurement light 3a reflected by the surface 8 to be measured is
Once again, the parabolic mirror 5 makes a parallel light flux, returns to the original optical path, and enters the polarization beam splitter 2. The reference light 3 b split by the polarization beam splitter 2 returns to the original optical path after being reflected by the reference surface 9 and enters the polarization beam splitter 2. Since the measurement light 3a is transmitted through the split surface of the polarization beam splitter 2 and the reference light 3b is reflected by the split surface, both have the same optical path and cause interference. This interference light is detected by the detector 10. The calculation means obtains the distance to the measured surface 8 based on the detection result of the detector 10. Hereinafter, a plurality of measured points 8 are set on the reflective surface of the optical element 13, and the shape of the reflective surface of the element 13 is obtained from the result of measuring the distance to the measured point 8. The measuring light 3a has a focal point 7 on the surface 8 to be measured of the optical element 13.
It is advisable to provide a mechanism for detecting whether or not the cable is tied. This mechanism measures, for example, the intensity of the reflected light of the measurement light 3a,
The measuring probe 50 is shown in FIG. 2 so that its intensity is maximized.
It may be configured to move in the arrow A direction. Since the configuration of the displacement meter itself is the same as the conventional one, the description of the calculation process in the calculation means is omitted. Further, the process of obtaining the shape of the optical element 13 from the measurement result of this displacement meter is also similar to the conventional one, and therefore its explanation is omitted.

FIG. 4 is a schematic plan view showing the configuration of the shape measuring apparatus provided with the displacement gauge 11 having the configuration of FIG. This shape measuring apparatus includes an X-axis stage 12 having a displacement gauge 11 installed therein, a Z-axis stage 15 having a spindle spindle 14 having an object to be measured (optical element) 13 installed therein, an X-axis stage 12 and a Z-axis stage 15. Length measuring machine 1 for measuring position
6, encoder 1 mounted on the spindle 14
7. A controller (not shown) for driving the X-axis stage 12 and the Z-axis stage 15 and obtaining the shape of the object 13 to be measured from the measurement results of the displacement gauge 11, the length measuring machine 16, and the encoder 17. . The X-axis stage 12 and the Z-axis stage 15 are arranged at right angles, and their movement is such that the DUT 1
The two-dimensional shape of the object to be measured 13 is continuously measured by the displacement meter 11 under the control of the control means in accordance with the shape of No. 3. At that time, the spindle spindle 14 is rotated simultaneously with the movement of the X-axis stage 12 and the Z-axis stage 15,
The three-dimensional shape of the DUT 13 may be measured by the displacement meter 11. In addition, the X-axis stage 12 and the Z-axis stage 1
If the position of 5 is measured by the length measuring machine 16 and the rotation angle of the object to be measured 13 is measured by the encoder 17 incorporated in the spindle spindle 14, and it is synchronized with the measurement data of the displacement gauge 11, the accuracy is further improved. Accurate measurement data can be obtained.
In this case, the data of the displacement gauge 11 can be fed back to the control of the X-axis stage 12 so that the focal point 7 of the parabolic mirror 5 is always located on the measured surface 8. Also,
By changing the measurement range and the measurement interval when controlling the X-axis stage 12 and the Z-axis stage 15, it is possible to obtain not only the shape of the DUT 13 but also undulation and roughness data.

[0012]

As described above, according to the present invention, the inner surface shape of a cylindrical object having a small inner diameter can be measured with high accuracy. In addition, there is no risk of damaging the object to be measured. The measurement result obtained with the measurement probe of the present invention can be fed back not only as the confirmation of the shape accuracy of the optical element but also as the processing data used at the time of manufacturing, so that a highly accurate X-ray optical element can be obtained. It can also be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 is an enlarged view of the parabolic mirror section in FIG. 1.

FIG. 3 is a schematic view showing a conventional contact type measurement probe.

FIG. 4 is a schematic plan view showing a shape measuring device incorporating the measuring probe of the present invention.

[Explanation of symbols for main parts]

 1 Light Source 2 Polarization Beam Splitter 3a Measurement Light 3b Reference Light 4 λ / 4 Wave Plate 5 Parabolic Mirror 6 Main Body of Measurement Probe 7 Focus 8 Measured Surface 9 Reference Surface 10 Detector 11 Displacement Meter 12 X-axis Stage 13 Optics Element (measurement object) 14 Spindle spindle 15 Z-axis stage 16 Length measuring machine 17 Encoder 18 Contact type measurement probe 19 Measuring element 20 Arm 50 Measuring probe

Claims (2)

[Claims] 1. A measurement probe used in a displacement meter for measuring a distance to a measurement point of an object to be measured in a non-contact manner, which irradiates the measurement light with the measurement light and receives reflected light from the measurement point. In the above, a cylindrical main body and a parallel light flux measurement light that has been installed at one end of the main body and passed through the inside of the cylinder are deflected in a direction orthogonal to each other, and a focus is set in the deflection direction. A measuring probe having a parabolic mirror for converging and converging. 2. A splitting means for splitting the measurement light emitted from the light source, a reference surface for reflecting one of the split measurement lights, and the other split measurement light for irradiating the measurement surface with the measurement surface. Measuring probe for receiving the reflected light of, the interference means for interfering the reflected light from the reference surface and the reflected light from the measured surface, the light receiving means for detecting the interfering light, the detection result by the light receiving means In a non-contact type displacement gauge having a calculation means for obtaining the distance to the surface to be measured based on
A displacement gauge, wherein the measurement probe according to claim 1 is used as the measurement probe.