JP2001324309A - Three-dimensional shape measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-dimensional shape measuring instrument capable of measuring two or more measured surfaces with high accuracy in a short time without causing 'a setting error' caused by setup changing work. SOLUTION: This instrument is structured to measure reference balls 9 in a noncontacting manner by using a measurement optical head 5 comprising an interferometer as a position measuring means for measuring the positions of the reference balls 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a lens, for example,
The present invention relates to a three-dimensional shape measuring apparatus that measures a surface of a measured surface of a measured object having a continuous curved surface shape such as a mirror or a mold with reference to three-dimensional coordinates. TECHNICAL FIELD The present invention relates to a three-dimensional shape determination device capable of measuring with high precision in a precise manner.

[0002]

2. Description of the Related Art For example, various shape measuring devices for accurately measuring the surface shape of optical elements such as lenses and mirrors used in cameras, video cameras, semiconductor manufacturing devices and the like have been proposed and developed. As the shape measuring device, for example, a base on which an object to be measured is set, a probe attached to a column provided on the base, and a three-dimensional slide for moving the probe three-dimensionally with respect to the object to be measured on the base What is known is provided with means.

In order to accurately measure an object to be measured by such a shape measuring apparatus, it is important to set the object to be measured at an accurate position on a base.
However, it is usually difficult to accurately position and set the DUT, and a certain amount of deviation (hereinafter referred to as “set error”) from a preset set position is difficult.
In many cases).

As a result, for example, a coordinate system when set with reference to a shape measuring device (hereinafter referred to as a “measurement device coordinate system”) and a coordinate system when set with reference to a surface to be measured of an object to be measured. (Hereinafter referred to as the “measurement object coordinate system”) does not match well, and even if the measurement can be accurately performed in the “measurement device coordinate system”, the measured value is represented by the following formula “measured value” There is a possibility that “set error” may be included as in “true shape value” + “set error”.

[0005] In addition, there is a possibility that an inherent error due to manufacturing may occur on the measured surface of the measured object. Therefore, even if the “design value” is subtracted from the “measurement value”, “measurement value” − “design value” = “true shape value” + “set error” − “design value” = “shape error” In addition, two types of errors, ie, “set error”, are included, and only the “shape error” cannot be measured alone.

Therefore, a shape measuring device and a method for measuring such a "shape error" are disclosed in Japanese Patent Application Laid-Open No. 11-17 / 1999.
The thing described in 3835 gazette is known.

In this shape measuring apparatus, as shown in FIG. 5, a shape of a measured object 1 'having one measured surface and three spherical surfaces 9' is measured. Specifically, three spherical surfaces 9 'indicating the mounting position of the object 1' are provided, and the center point of the spherical surface 9 'is measured by the contact-type probe 5A, thereby measuring in the "measurement device coordinate system". The position of the measured measurement point group is obtained. Then, in order to convert the position in the “measurement device coordinate system” to the coordinate position in the “measurement object coordinate system”, a so-called coordinate transformation matrix is obtained, and the position coordinates of the measurement point group are determined using the coordinate transformation matrix. Is to be converted.
By this coordinate conversion, the "set error" of the DUT 1 'is removed, and the "shape error" can be measured.

Moreover, in the shape measuring apparatus described in this publication, for example, the object to be measured 1 'has two or more surfaces to be measured,
When it is necessary to measure their relative positions with high precision, it is impossible to measure them without resetting such as reversing the surface to be measured (hereinafter referred to as setup change). Even with this method, highly accurate shape measurement can be performed on two or more surfaces to be measured. That is, in addition to the shape measurement on each surface to be measured, the three spheres 9 'are measured, and the measurement is performed using a new coordinate system based on the central coordinate position of these spheres 9'. The relative position between the surfaces is measured with high accuracy without being affected by the "set error" accompanying the setup change.

[0009]

By the way, in the shape measuring apparatus having such a configuration, every time the surface to be measured is measured by changing the setting of the object to be measured 1 ', three spherical surfaces 9' each time are measured. In this measurement, since the shape measurement is performed by tracing the probe 5A while actually making contact with the spherical surface 9 ', the measurement takes a relatively long time. ing.

In view of the above-mentioned drawbacks, the present invention can measure two or more surfaces to be measured in a short time and with high accuracy without causing a "set error" due to a setup change. It is an object of the present invention to provide a three-dimensional shape measuring device.

[0011]

According to the present invention, a stage on which a mounting portion having at least three or more spherical surfaces is set and a plurality of objects to be measured mounted on the mounting portion are provided. Measured surface measuring means for measuring the measured surface,
Position measuring means for measuring the spherical position at the time of measurement by the measured surface measuring means, and three-dimensional measuring means for changing a set state of the measured object on the stage and measuring a relative shape of a plurality of measured surfaces. In a shape measuring device, the measured surface measuring means and the position measuring means are provided separately and independently.

According to a second aspect of the present invention, in the first aspect of the present invention, the position measuring means and the measured surface measuring means are provided separately and independently or as both.

According to a third aspect of the present invention, in the first or second aspect of the invention, the position measuring means is configured to measure the spherical position by specular reflection wavefront measurement using an optical interferometer.

[0014] The invention described in claim 4 is the first or second invention.
In the invention described in (1), the measured surface measuring means is configured to perform the measurement by a non-contact surface trace by an optical means.

[0015] The invention according to claim 5 is the invention according to claims 1, 2,
In the invention described in any one of the fourth to ninth aspects, the measured surface measuring means is configured to perform a surface contact trace by mechanical means in addition to the optical means.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a three-dimensional shape measuring apparatus according to the present invention. In this three-dimensional shape measuring apparatus, an aspheric lens is provided on a stage on a base plate B via a work holder WH. The DUT 1 is set, and the shape of the spherical surface R1 of the aspherical lens and the work holder WH
The DUT 1 is turned over and the shape of the spherical surface R2
The eccentric state between the surfaces R1 and R2 is measured.

For this reason, this three-dimensional shape measuring apparatus includes:
A base platen B, a column C provided thereon, a light source 2,
AOM frequency shifter 3, polarization-maintaining optical fiber 4,
It comprises a measuring optical head 5, a signal processing system 6, a three-dimensional sliding means 7, and an interferometer 8.

The base table B has a Y table 7 which is a part of a three-dimensional slide means 7 described later and also serves as a stage.
B is provided slidably in the Y-axis direction. This Y
The table 7B is configured to slide along a guide shaft (not shown) provided in parallel with the Y-axis direction by a ball screw (not shown) rotated and driven by a motor 71B. On the Y table 7B, work holders WH, which are mounting portions of the DUT 1, are set, and reference spheres 9 are provided at three positions of the work holder WH.

The reference sphere 9 is provided in consideration of the fact that an error is likely to occur particularly when measuring the relative positional relationship between a plurality of surfaces to be measured. That is, specifically, for example, when measuring the shapes of the two spherical surfaces R1 and R2 of the aspherical lens, when the shape measurement of the spherical surface R1 is completed, the Y table 7 which is the stage of the base platen B is usually used.
The shape of the spherical surface R2 cannot be measured unless the aspheric lens is removed from B and the surface to be measured is inverted from the spherical surface R1 to the spherical surface R2. Therefore, when the aspherical lens is set on the stage again after inversion, the spherical surface R
There is a possibility that a relative displacement of the set position, that is, a “set error” may occur between the set state and the set state at the time of one measurement.
Therefore, by measuring the position of the reference sphere 9 before and after the inversion, the “set error” before and after the inversion of the DUT 1 is determined from the deviation value of the position data of the reference sphere 9 measured before and after the inversion.
Is indirectly measured.

A laser that emits coherent light is used for the light source 2 and is fixed to the column C.
The incident light is slightly changed in frequency (F1, F2) 2
The AOM frequency shifter 3 for converting the light into the
AOM driver 3
A (see FIG. 2).

The measuring optical head 5 serves as a measuring surface measuring means for measuring the measuring surface and a position measuring means for measuring the position of the spherical surface.
It is fixed to the Z table 7C on the table 7A, and is set so that the measurement optical axis of the laser light emitted toward the surface to be measured of the device under test 1 is parallel to the Z axis. And
As shown in FIG. 2, the measuring optical head 5 includes a collimator lens 51, a polarizing beam splitter 52, first and second quarter-wave plates 53A and 53B, a reference plane 54, and an objective lens. 55, a polarizing plate 56, a condenser lens 57, a half mirror 58, a CCD camera 59, and a photodetector 60.

The output of the photodetector 60 is input to a signal processing system 6, which includes a phase meter 61, a computer 62, and a servo driver 63. The output of the photodetector 60 is connected to the input of a phase meter 61. On the other hand, this phase meter 6
The input of 1 is connected to the output of the above-described AOM driver 3A, and the output of the phase meter 61 is connected to a computer 62. Further, a servo driver 63 is connected to an output of the computer 62, and is a part of a three-dimensional sliding means 7 described later and is a driving motor 71 for driving a Z table 7C that slides in the Z-axis direction.
Servo is applied to C.

The three-dimensional slide means 7 includes an X table 7
A, a Y table 7B, and a Z table 7C are provided, and motors each having a ball screw are provided as drive means for individually and precisely moving the tables independently. Of these, X table 7
A is configured to slide between the columns C along the X-axis direction by a ball screw 72A that is rotationally driven by a motor 71A attached to the column C. The Y table 7B is slid along the Y-axis direction by a ball screw (not shown) that is rotated by a motor 71B. Further, the Z table 7C is slid along the Z-axis direction on the X table 7A by a ball screw 72C that is rotationally driven by a motor 71C attached to the X table 7A.

The interferometer 8 includes a base plate B and the DUT 1
For accurately measuring the relative positional relationship between the three measuring objects and the measuring optical head 5 and the relative positional relationship between the DUT 1 and the measuring optical head 5 and the two bodies on a three-dimensional coordinate system, respectively. It is. Therefore, the interferometer 8 of this embodiment
Has an X interferometer 8A, a Y interferometer (not shown), and a Z interferometer 8C.
The distance from a reference plane mirror, which will be described later, is accurately measured by using the laser light emitted from the light source. That is, in these interferometers 8A to 8C, one laser beam emitted from the laser
The laser light is split into three light beams via the light source 2, and the separated laser light beams are guided to the respective interferometers 8A to 8C for use. Note that the X interferometer 8A and the Z interferometer 8C
Both are mounted on a Z table 7C provided on an X table 7A, while a Y interferometer (not shown) is mounted on a Y table 7B.

Among these interferometers, X interferometer 8A is
The laser beam is emitted in parallel with the X-axis direction, and a reference plane mirror 83A is fixed on the column C where the emitted laser beam travels. On the other hand, Y
Similarly to the X interferometer 8A, the interferometer 8B emits laser light parallel to the Y-axis direction toward a reference plane mirror provided on a column (not shown). Similarly, the Z interferometer 8C emits a laser beam parallel to the Z-axis direction, and a suitable member (not shown) fixed between columns C where the emitted laser beam travels is provided. , A reference plane mirror 83C is fixedly provided.

Therefore, with respect to the measuring optical head 5, the relative positional relationship in the X-axis direction with respect to the base platen B (also with respect to the DUT 1) is relative to the X interferometer 8A and in the Z-axis direction. The positional relationship can be measured from the Z interferometer 8C. On the other hand, for the DUT 1, the base plate B
(Similarly for the measurement optical head 5) in the Y-axis direction can be measured from the Y interferometer 8A.

By the way, in this three-dimensional shape measuring apparatus,
Base surface plate B to which reference plane mirrors 83A and 83C are attached
In the above, the positions of the DUT 1 provided on the Y table 7B and the measuring optical head 5 provided on the Z table 7C can be freely moved. That is, the DUT 1 can move freely on the XY plane, and the measuring optical head 5 can move freely on the XZ plane. Therefore, the relative positional relationship in the XYZ orthogonal coordinate system between the base platen B, the DUT 1 and the measuring optical head 5 in the moving relationship is determined by the interferometer 8 and the reference plane mirror 83. By using it, it is possible to measure with high accuracy.

Next, the operation principle of the measuring optical head 5 for measuring a plurality of measured surfaces R1 and R2 of the aspherical lens as the measured object 1 will be described.

Now, the laser beam emitted from the light source 2 is A
By the action of the OM frequency shifter 3, the light is converted into two lights having slightly different frequencies whose polarization directions are orthogonal to each other, and enters the polarization-maintaining optical fiber 4. The laser light incident on the polarization-maintaining optical fiber 4 propagates through the optical fiber 4 and is guided to the measuring optical head 5. That is, the laser light that has traveled in the optical fiber 4 emits two-frequency light from the emission end 4A while maintaining the polarization direction.

In the measuring optical head 5, the laser light emitted from the optical fiber 4 is divergent light, and becomes parallel light by the collimator lens 51 and enters the polarization beam splitter 52. One of the two-frequency light that has entered the polarization beam splitter 52 is reflected and travels to the reference plane 54 side, and the other light passes and travels to the DUT 1 side. Among them, the laser light traveling to the reference plane 54 side is converted into circularly polarized light by the quarter-wave plate 53A, and after being specularly reflected by the reference plane 54, is again returned to the quarter-wave plate 53A.
When transmitted through A, it is converted to linear deflection. Thereafter, returning to the polarization beam splitter 52, the quarter-wave plate 53
Because the polarization direction is rotated 90 degrees when transmitting through A,
This time, the light passes through the polarization beam splitter 52 and travels toward the photodetector 60.

On the other hand, the laser light traveling toward the DUT 1 is similarly converted into circularly polarized light by the quarter-wave plate 53B, and converged by the objective lens 55 as shown in FIG. As a result, a focal point is formed on the surface of the DUT 1 and the so-called cat's eye is reflected. Then, the laser light reflected by the cat's eye on the surface of the DUT 1 returns to the objective lens 55 and the quarter-wave plate 53B. And this quarter wave plate 5
The laser light converted from the circularly polarized light to the linearly polarized light in 3B returns to the polarizing beam splitter 52, but is output to the quarter-wave plate 53.
Since the polarization direction is rotated by 90 degrees in B, the light is reflected by the polarization beam splitter 52 and travels toward the photodetector 60 this time. Here, the objective lens 55
Has a numerical aperture (NA) such that the aperture angle is larger than the maximum surface inclination angle of the DUT 1, and light incident on the objective lens 55 is also filled in the full aperture. Has become.

In this way, the laser beams reflected by the reference plane 54 and the DUT 1 (surface to be measured) and traveling toward the photodetector 60 are interfered by the action of the polarizing plate 56 and cause the condenser lens 57 to move. The light passes through and enters the photodetector 60. The interference light incident on the photodetector 60 has a difference between the two frequencies (F1
−F2), and the photodetector 60 outputs a so-called beat signal to the signal processing system 6.

In the signal processing system 6, a phase meter 61 that inputs the beat signal has a measured beat signal (hereinafter referred to as a measurement signal) and a reference beat signal (hereinafter referred to as a reference signal).
If the phase difference with the reference beat signal is measured, the reference plane 5
It can be seen that the optical path length difference between the light directed to the side 4 and the light directed to the DUT 1 is changed.

Therefore, conversely, servo is applied so as to move and adjust the measuring optical head 5 along the Z-axis direction so that the phase (difference) is constant, and the object 1 and the measuring optical head 5 are connected to each other. Is read in another orthogonal coordinate system while changing the relative position in the XY plane orthogonal to the Z axis, the three-dimensional shape of the surface of the DUT 1 can be measured in principle. In this embodiment, a difference (F1-F2) between two drive frequencies is obtained from the AOM driver 3A through a mixer circuit (not shown) from the reference beat signal.

As described above, the DUT 1 and the measuring optical head 5 can be arbitrarily moved and measured in the rectangular coordinate system on the three-dimensional measuring device. Therefore, the signal from the measuring optical head 5 is used to move the Z-table 7C motor 7
If the X table 7A and the Y table 7B are moved along a predetermined pattern while applying a servo to 1C, and the Z position is read at each predetermined (X, Y) position, This means that the three-dimensional shape of the surface to be measured can be measured according to the principle.

Further, before or after the measurement of the surface to be measured, at least three spatial positions of the reference sphere 9 attached to the work holder WH are measured, so that these (three) reference spheres are measured. The spatial positions of the surfaces to be measured R1 and R2 based on the plane formed by the sphere 9 can be determined.

The position of the reference sphere 9 is measured as follows.

That is, as shown in FIG. 3B, when the alignment is performed so that the center of the reference sphere 9 and the focal point of the objective lens 55 coincide with each other, in FIG. The light reflected by the mirror 58 interferes with each other to form an interference fringe on the CCD camera 59, and generates a fringe pattern according to the "set error". However, in order to see the interference fringes, it is necessary to adjust the drive frequency in the AOM frequency shifter 3 so as not to generate a beat.

Next, if the interference fringe pattern is aligned so as to be one-color, the position is such that the focal position of the objective lens 55 and the center position of the reference sphere 9 coincide with each other. This corresponds to the fact that the center position of No. 9 could be measured. Similarly, this operation is performed for another reference sphere 9.
If the center positions of three or more reference spheres 9 are known, only one plane passing through these center positions is uniquely determined. As a result, the relative position of the measured surface R1 with respect to this plane can be determined.

Then, the workpiece 1 is moved to the work holder WH.
The setup is changed to set upside down, and this time, the measured surface R2 on the back side is measured, and by the method described above,
The position of the same reference sphere 9 is measured again.

Based on the data obtained by this measurement, it is possible to determine the plane defined by the reference sphere 9 determined by three or more and the spatial position of the measured surface R2 with respect to the plane. Here, since the plane defined by the reference sphere 9 does not change even when the surfaces to be measured R1 and R2 are measured, the measurement results of the relative positions of the surfaces to be measured R1 and R2 are obtained from these measurement results. Can be determined precisely. Normal,
In an aspheric lens, decentering is defined by a single lens,
This example shows that the surface shape and the eccentricity can be measured. Instead of aligning the interference fringe pattern, for example, the misalignment amount is calculated from the tilt and defocus components calculated by analyzing the interference fringe analysis method. If an analysis device (not shown) that can perform the measurement is added, automatic measurement is also possible.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description will not be repeated.

The three-dimensional shape measuring apparatus according to the second embodiment has substantially the same configuration as that of the first embodiment, but uses a non-contact type measuring device for measuring the reference sphere 9 instead of the measuring optical head 5. The difference is that the first probe 5A and the second probe 5B are provided separately and independently.

In the first probe 5A, in particular, when measuring the shape of a plurality of surfaces to be measured accompanied by setup change, the "set error" between the measured surfaces which may occur before and after the setup change is reduced. In order to measure in a short time and with high accuracy, the reference sphere 9 is measured, and a non-contact type is used. That is, the first probe 5A is configured to measure the position of the reference sphere 9 by specular reflection wavefront measurement using an optical interferometer. The first probe 5A
Then, in addition to the measurement of the reference sphere 9, the shape of the measurement surface of the measurement object 1 to be measured by the second probe 5B described below may be measured as necessary.

On the other hand, the second probe 5B is only for measuring the shape of the surface to be measured of the device under test 1, and is of a contact type which measures the shape while directly contacting the surface to be measured. Have been. The contact-type second probe 5B is indispensable especially when the surface to be measured is not an optical mirror surface or when measuring a surface having a very low reflectance. However, the application range can be greatly expanded as compared with the first embodiment.

Therefore, according to this embodiment, the contact-type second probe 5B is used together with the non-contact-type first probe 5A.
Therefore, the shape of the surface to be measured can be selected from the non-contact type first probe 5A and the contact type second probe 5B according to the properties of the surface to be measured. As a result, as described above, it is possible to measure the measured surface even when the measured surface is not an optical mirror surface or when the reflectance is extremely low. Moreover, at the same time, the non-contact type first probe 5A capable of high-speed measurement is used for the measurement of the reference sphere 9, so that the object to be measured can be measured efficiently.

[0048]

As described above, according to the present invention, the position measuring means is configured to measure the spherical position in a non-contact manner, and high-speed measurement is performed for the non-contact position measurement. It is possible. Therefore, according to the present invention,
The measurement of the spherical position not only prevents the occurrence of a "set error" due to the setup change, but also measures two or more surfaces to be measured in a short time and with high accuracy. It is possible to perform high-precision measurement work on multiple measurement surfaces of the measurement object,
The efficiency of measurement work can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a three-dimensional shape measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a measuring optical head and a signal processing system of the first embodiment.

3A is a main part optical path diagram when measuring an object to be measured by a measuring optical head, and FIG. 3B is a main part optical path diagram when measuring a reference sphere by the measuring optical head;

FIG. 4 is a schematic configuration diagram showing a three-dimensional shape measuring apparatus according to the first embodiment of the present invention.

FIG. 5 is a perspective view showing a conventional three-dimensional shape measuring apparatus.

[Explanation of symbols]

Reference Signs List 1 workpiece (workpiece) 2 light source (laser) 3 AOM frequency shifter 3A AOM driver 4 polarization plane preserving optical fiber 5 measuring optical head (measured surface measuring means, position measuring means) 5A first probe (non-contact type Measurement surface measuring means) 5B Second probe (contact type position measuring means) 51 Collimator lens 52 Polarizing beam splitter 53A Quarter wave plate 53B Quarter wave plate 54 Reference plane 55 Objective lens 56 Polarizing plate 57 Light condensing Lens 59 CCD camera 6 Signal processing system 60 Photodetector 61 Phase meter 62 Computer 63 Servo driver 7 Three-dimensional slide means 7A X table 71A Motor 72A Ball screw 7B Y table (stage) 71B Motor 7C Z table 71C Motor 72C Ball screw 8 Interferometer 8A X interferometer 8C Z interferometer 83A Reference plane mirror 83C Reference plane mirror 9 Reference sphere (spherical surface) B Base platen C Column WH Work holder (mounting part)

Continued on the front page F term (reference) 2F065 AA04 AA17 AA20 AA53 BB05 BB07 CC00 CC21 CC22 DD06 DD19 FF49 FF52 FF55 FF61 GG04 HH10 HH13 JJ01 JJ03 JJ05 JJ09 JJ26 LL00 LL02 LL04 LL12 LL12 LL33 LL12

Claims (5)

[Claims] 1. A stage for setting a mounting portion having at least three or more spherical surfaces, a measurement surface measuring means for measuring a plurality of measurement surfaces of a measurement object mounted on the mounting portion, and the measurement target Position measuring means for measuring the spherical position at the time of measurement by a plane measuring means, a three-dimensional shape measuring apparatus for changing a set state of an object to be measured on a stage and measuring a relative shape of a plurality of measured surfaces A three-dimensional shape measuring apparatus, wherein the position measuring means is configured to measure a spherical position in a non-contact manner. 2. The three-dimensional shape measuring apparatus according to claim 1, wherein the position measuring means and the measured surface measuring means are provided separately and independently or as both. 3. The three-dimensional shape measuring apparatus according to claim 1, wherein the position measuring means is configured to measure a spherical position by specular wavefront measurement using an optical interferometer. 4. The three-dimensional shape measuring apparatus according to claim 3, wherein the measured surface measuring means is configured to perform the surface non-contact tracing by optical means. 5. The apparatus according to claim 1, wherein the measured surface measuring means is configured to perform a surface contact trace by mechanical means in addition to the optical means. 3. The three-dimensional shape measuring apparatus according to 1.