JPH08233688A - Eccentricity measuring device - Google Patents

Abstract

PURPOSE: To easily measure eccentricity of a quadratic aspheric surface by providing a holding adjusting mechanism to hold arid adjust a lens to be detected so that a focus of the quadratic aspheric surface is adjusted to an image forming point of a condenser lens, an interference measuring system, a rotary mechanism and an arithmetic unit. CONSTITUTION: A plane wave emitted from an interferometer main body 2 is introduced to a first Fizeau's lens 3, and is converted into a spherical wave. When an image forming point of the lens 3 and a first focus of a hyperboloid 1a are made to coincide with each other and are aligned with each other, a spherical wave diverged from the origin O is reflected by the hyperboloid 1a, and is again converted into a spherical wave. Since this spherical wave is equivalently diverged from a second focus of the hyperboloid 1a, when the center of a sphere of a turning-back mirror 4 is made to coincide with the second focus and these are aligned with each other, the spherical wave can be made perpendicularly incident on the mirror 4. Therefore, the spherical wave goes backward on a path coming just now, and a light flux reflected by a Fizeau' s surface 3a on a forward passage and a light flux passing through the Fizeau's surface 3a on a backward passage form interference fringes. As long as alignment is ideal, the interference fringes of the so-called 'all fringes' can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eccentricity measuring device for an aspherical lens.

[0002]

2. Description of the Related Art Generally, when measuring the eccentricity of a spherical lens with high accuracy, the lens is rotated by an outer diameter standard while the light is incident on the lens, and the reflected light from each surface of the lens shakes. The deviation between the center axis of the lens outer diameter and the lens optical axis (the straight line passing through the spherical center of each spherical surface), that is, the eccentricity was obtained by measuring

Further, when the outer diameter of the lens or the outer diameter of the lens holder is processed by a lathe type processing machine, the optical axis of the lens is similarly measured and matched with the rotation axis of the work. On the other hand, when measuring the eccentricity of an aspherical lens, the lens is similarly rotated and the deflection of the reflected light from each surface of the lens is measured to determine the center axis of the lens outer diameter and the lens reference axis (one surface side). Deviation between the "center of curvature of the central part of the aspherical surface" and the axis defined by the "center of curvature of the central part of the aspherical surface" or the "center of curvature of the spherical surface" on the two sides, and the lens reference axis and the aspherical surface axis I was looking for the inclination.

In the case of this conventional eccentricity measuring device utilizing rotation, since a highly accurate rotation mechanism is required, the lens to be inspected is held on the holder by, for example, vacuum suction,
The holder was rotated by the air spindle. Further, the outer diameter processing of the aspherical lens can be realized by the same idea as that of the spherical surface. As described above, the eccentricity measuring device using the rotation of the work has an advantage that it can be expanded to the outer diameter processing machine by adding an option.

[0005]

However, in the case of the conventional eccentricity measuring device utilizing rotation, when measuring the shake of the surface to be inspected, only partial surface information of the surface to be inspected is used. There wasn't. Therefore, if the surface accuracy of the surface to be inspected is poor,
There is a problem that accurate eccentricity measurement cannot be performed unless the surface information is input for correction.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide an eccentricity measuring device capable of measuring the eccentricity of a secondary aspherical lens by using the entire surface information of the aspherical surface. .

[0007]

In order to solve the above problems, the present invention provides an "interferometer main body, and a condenser lens for converting a plane wave emitted from the interferometer main body into a spherical wave.
From the secondary aspherical surface, there is provided a first holding adjustment mechanism for holding and adjusting the secondary aspherical surface forming the lens to be inspected so that the focal point of the secondary aspherical surface coincides with the image forming point of the condenser lens. A reflection mirror for reflecting a plane wave or a spherical wave that is reflected light of the second reflection mirror, and a second mirror for holding and adjusting the reflection mirror so that the reflection light from the reflection mirror re-images at the image formation point. Holding adjustment mechanism, an interference measurement system for performing interference measurement from the rear surface side of the lens to be inspected, and a moving mechanism for moving the interference measurement system in the measurement optical axis direction, or the measurement light to the lens to be inspected. An eccentricity measuring device including a rotating mechanism for rotating about an axis, an interferometer main body, and an arithmetic device for arithmetically processing measurement data of the interferometric measurement system ".

[0008]

In FIG. 1A, the lens 1 to be inspected has the secondary aspherical surface 1
secondary aspherical surface 1a when it is composed of a and spherical surface 1b
It is a principle view of an eccentricity measuring device for measuring the eccentricity of the spherical surface 1b with respect to. As an example of the quadratic aspherical surface, folding measurement is performed when the quadratic aspherical surface 1a is a hyperboloid. Although a Fizeau interferometer is used as the interferometer main body 2, a Twyman-Green interferometer or the like may be used.

In FIG. 1A, first, a plane wave (usually a He-Ne laser beam) emitted from the interferometer main body 2 is irradiated with a curvature of a first Fizeau lens 3 (a Fizeau surface 3a which is a final surface on the emission side). The lens is centered on the image forming point of the lens) and is converted into a spherical wave. Then, the spherical center of the spherical wave, that is, the imaging point of the first Fizeau lens (origin O) and the first focal point of the hyperboloid 1a are aligned and aligned, so that the spherical wave diverging from the origin O Is reflected by the hyperboloid 1a and converted into a spherical wave again. Since this spherical wave diverges equivalently from the second focus of the hyperboloid 1a,
By aligning the spherical center of the folding mirror 4 (designated as point A) with the second focal point, it is possible to make the spherical wave enter the folding mirror 4 vertically. Therefore, the spherical wave, which is this measurement light flux, returns to the path that has just arrived, and the light flux reflected by the Fizeau surface 3a on the forward path and the light flux that has transmitted through the Fizeau surface 3a on the return path form interference fringes. Become. In this state, if each optical surface has an ideal shape and the wavefront of the measurement light beam is in an aberration-free state, so-called "stripe monochromatic" interference fringes can be obtained as long as the alignment is performed ideally.

The lens 1 to be inspected and the folding mirror 4 are aligned by a holding adjustment mechanism (not shown) so that interference fringes are formed. Further, the spherical wave from the Fizeau surface 3a of the condenser lens (Fizeau lens) 3 is assumed to be in an ideal state, but when aberration occurs, a so-called high-precision reference surface is used as a reflector. “Ref subtraction” should be applied.

Further, the folding mirror 4 for secondary aspherical surface measurement
If there is a shape error in the above, or if the alignment is not in the ideal state, the correction is necessary. For example, the correction of the shape error of the folding mirror 4 is disclosed in “Folding interference measuring apparatus” of the present application and the simultaneous application, including the coordinate matching. Further, Japanese Patent Application No. 7-32579 discloses the alignment error correction.

The result of the alignment error correction needs to be fed back to the measurement of the aspherical axis. The following discussion is based on the above ideal state for the time being. In this case, the aspherical axis of the hyperboloid 1a is determined by the first Fizeau lens 3
It can be defined by a straight line connecting the ball center O of the Fizeau surface 3a and the ball center A of the folding mirror 4. At this time, a straight line O is drawn from the spherical center B of the "spherical surface 1b opposite to the aspherical surface 1a of the lens 1 to be tested".
The length and direction of the perpendicular drawn to A are defined as the amount of eccentricity of the aspherical lens.

FIG. 1 shows how to obtain the positions of the ball center A and the ball center B.
This will be described with reference to (a) and (b). In FIG. 1B, a second interferometer main body 10, a second Fizeau lens 6, and an interferometer measuring system for interferometric measurement from the back surface side of the lens 1 to be inspected are provided.
Further, although a holding adjustment mechanism (not shown) for holding and adjusting the second Fizeau lens is adopted, the plane wave from the first interferometer main body 2 may be crawled as shown in FIG. 4 described later.

First, the optical axis of the first interferometer body 2 and the optical axis of the second interferometer body 10 are substantially aligned with each other. This optical axis represents the direction of the plane wave, and is defined by the reference plane mirrors 2a and 10a provided inside each interferometer body. Furthermore, each Fizeau lens 3 and 6 has its own Fizeau surface 3
a and 6a are the reference plane mirrors 2a and 1 inside each interferometer body.
Each Fizeau lens is installed on this optical axis by aligning with 0a in the Twyman interference mode. The above alignment is performed to ensure that both interferometer measurements themselves are accurate.
The effect of these alignment errors on the accuracy of eccentricity measurement can be ignored.

At this time, the optical axis passing through the spherical center O of the Fizeau surface of the first Fizeau lens is changed to the final optical axis of the interferometer (hereinafter,
It is defined as "optical axis"). The alignment of the second Fizeau lens is positioned by causing the Fizeau surface of the first Fizeau lens to interfere with the Fizeau surface of the first Fizeau lens in a “striped color”. For this positioning, the second Fizeau lens may be shifted in the direction perpendicular to the optical axis, or may be tilted with respect to the optical axis.

Further, a moving mechanism (not shown) for moving the second Fizeau lens in the optical axis direction is adjusted and placed so as to be substantially parallel to the optical axis. Since the straightness (wobble) when the holding adjustment mechanism (not shown) moves on this moving axis greatly affects the measurement accuracy, it is essential to secure the straightness. Further, if sufficient straightness cannot be ensured with respect to the overall eccentricity measurement accuracy, it becomes necessary to optically detect the flutter and correct the position.
In FIG. 1, the movement axis and the optical axis are shown to match each other.

Under the above settings, the amount of deviation of the spherical center B of the "spherical surface opposite to the aspherical surface of the lens to be tested" with respect to the moving axis passing through the origin O is obtained as follows. That is, the second Fizeau lens 6 is moved in the optical axis direction, and is moved to a position where "interferometric measurement of the spherical surface opposite to the aspherical surface of the lens to be measured" is possible, and then the deviation amount is detected. To do. As a specific detecting means, a holding and adjusting mechanism (not shown) is so arranged that the Fizeau surface 6a of the second Fizeau lens 6 and the "spherical surface opposite to the aspherical surface of the lens to be inspected" 1b interfere with "a single stripe". Alternatively, the second Fizeau lens 6 may be aligned, and the alignment amount may be detected by a detection means such as a micrometer. In addition, when the deviation amount is small, it may be converted from the alignment error correction amount itself which is the interference measurement data from the back surface side of the lens 1 to be inspected.

The position of the spherical center A of the folded spherical mirror can be similarly obtained (at that time, the lens to be inspected needs to be removed). As described above, the positions of the spherical centers A and B with respect to the moving axis passing through the origin O are determined, and thus the eccentricity amount defined as described above is obtained.

[0019]

EXAMPLE The measurement example described in the operation is the first example of the present invention, and the image forming point of the first Fizeau lens, that is, the origin O is used to position the second Fizeau lens. It is possible. In other words, the "spherical surface opposite to the aspherical surface of the lens to be inspected", and the interference state between the folding mirror and the Fizeau surface of the second Fizeau lens are on the moving axis of the holding adjustment mechanism (not shown). This is a case where it can be realized within the moving range via imaging points such as points O, A, and B.

As the measuring device, means for detecting the deviation of the ball centers A and B from the optical axis (more precisely, the moving axis) is required. Although it depends on the eccentricity accuracy and the measurement NA (Numerical Aperture), it is desirable to use a piezo element as a positioning mechanism for alignment in order to measure a lens with a small eccentricity with high accuracy. Further, in order to calculate the eccentricity amount with high accuracy, a positional relationship between the points O, A, and B in the optical axis direction is also required, and therefore, a scale, or a moving distance detecting means (not shown) such as a laser length measuring device. )Is required. In ordinary measurement, it is sufficient to calculate the positional relationship between the points O, A, and B in the optical axis direction from the design value.

An arithmetic unit (not shown) has a function of preliminarily inputting information about the surface to be inspected, calculating and storing coefficients required for the arithmetic operation prior to measurement, and an interference fringe image pickup means (CCD camera) in the interferometer main body. ) Has the function of converting the image information from the optical path difference data into the optical path difference data, the function of analyzing the optical path difference data based on the coefficient to calculate the shape error of the surface to be inspected, and the function of displaying the measurement result. .

The lens 1, the folding mirror 4 and the second Fizeau lens 6 are aligned by a holding and adjusting mechanism (not shown) so that the reflected light from the surface to be inspected and the reference reference surface form interference fringes. Be seen. The alignment is performed while sending a signal from the interference fringe image pickup means to a monitor (not shown) and observing the interference fringes on the monitor. FIG. 2A is a first modification of the first embodiment of the present invention, which is a “spherical surface opposite to the aspherical surface of the lens to be tested” and / or a folding mirror and a second mirror. When the interference state with the Fizeau surface of the Fizeau lens is realized within the movement range on the movement axis of the holding adjustment mechanism (not shown), the second Fizeau lens is a diverging type (the light beam emitted from the Fizeau lens does not converge). In this case, it is impossible to position the second Fizeau lens via the origin O.

In this case, the positioning of the second Fizeau lens 61 must be performed in the Twyman interference mode with respect to the reference mirror 10a inside the interferometer main body, as in the case of the first Fizeau lens 3. This is just one means to adjust the axis of the Fizeau lens parallel to the optical axis,
For the axis alignment with respect to the origin O, for example, a method of utilizing cat's eye reflection on the Fizeau surface 61a as shown in FIG. 2B can be used.

The positioning accuracy of the second Fizeau lens 61 has a great effect on the overall eccentricity measurement accuracy, and at the same time, the high accuracy of the optical axis and the first Fizeau lens 3 which is not necessary in the first embodiment. Alignment is also necessary to ensure the accuracy of the overall eccentricity. Further, the second Fizeau lens is exchanged depending on whether the "spherical surface opposite to the aspherical surface of the lens to be inspected" interferes with "one stripe color" or when the interference is caused with the folding spherical mirror using "one stripe color". If necessary, it is necessary to suppress the positioning error due to replacement of the Fizeau lens.

FIG. 3A shows a second modification of the first embodiment of the present invention, in which the lens 11 to be inspected is composed of a parabolic surface 11a and a spherical surface 11b. In this case, since a plane is used as the folding mirror 41, it is essentially impossible to position the second Fizeau lens 6 via the origin O. Therefore, also in this case, since the folding mirror 41 must be aligned with respect to the optical axis, as shown in FIG. 3B in addition to the advance optical axis alignment described in the first modification. The second Fizeau lens needs to be replaced.

This is a replacement of the convergent or divergent second Fizeau lenses 6 and 61 with the flat second Fizeau lens 62, and in order to prevent the optical axis from being broken in advance, The plane type Fizeau lens 62 is preferably a plane parallel plate. At this time, three-beam interference (a plane parallel to the Fizeau surface,
In order to avoid interference of reflected light from the three surfaces, it is necessary to apply an antireflection film on the surface opposite to the Fizeau surface 62a.

Further, although the above-mentioned embodiment is an example of decentering measurement in the case of a test lens whose one surface is composed of a secondary aspherical surface, in the case of a test lens having a secondary aspherical surface on both sides, It is applicable as well. As a second embodiment of the present invention, as shown in FIG. 4, instead of moving the second Fizeau lens,
A device provided with a rotation mechanism for rotating the lens under test around the optical axis will be described.

In FIG. 4 (a), the hyperboloid 1a on one surface of the lens 1 to be inspected is measured by folding back in "one color of stripe". In this state, the spherical surface 1b on the back surface and the Fizeau surface 6a of the second Fizeau lens 6 for calibrating the interference measurement system from the back surface are
The second Fizeau lens 6 is aligned by a holding adjustment mechanism (not shown) so as to be in the “one-color stripe” state. In FIG. 4B, the lens 1 to be inspected is rotated by 180 degrees around the optical axis by using the rotation mechanism 9, and the hyperboloid 1a is similarly aligned again in the interference state of “stripe color”. At this time, when the interference fringe data on the back surface is analyzed without moving the second Fizeau lens 6, the obtained data shows an error of twice the desired eccentricity amount.

If the number of stripes is small, the interference fringes on the back surface can be analyzed with high precision by means such as fringe scanning. If fringe scanning is not possible due to too many stripes, use the so-called "point mode" of an interferometer or use an infrared interferometer to expand the dynamic range of eccentricity measurement. Can be dealt with. Further, in FIG. 4A, the interference measurement system from the back surface side does not necessarily have to be in the "one-color stripe" state. That is, unless the second Fizeau lens 6 is moved with respect to the interferometric measurement system on the secondary aspherical surface side, the desired eccentricity is similarly obtained from the subtraction of the two pieces of the interference fringe data shown in FIGS. An error twice the amount can be calculated.

FIG. 5 shows a third embodiment of the present invention, which is an apparatus for simultaneously measuring eccentricity and κ and R, which are power components of the secondary aspherical surface. Details are disclosed in "Interference measuring device", which is filed concurrently with the present application. A brief description will be given below. As a specific arrangement, one interferometer body 2
And four deflection mirrors 5 are combined to form a first deflection mirror 5a.
The measurement light flux is selected by inserting or removing. That is, when the first deflecting mirror 5a is not inserted, the measuring light beam is incident on the secondary aspherical surface 1a of the lens 1 under test through the first Fizeau lens 3 by the fourth deflecting mirror 5d. Enables fold-back interferometry of spherical surfaces. Further, when the first deflection mirror 5a is inserted, the measurement light beam enters from the back surface side of the lens 1 to be measured through the second Fizeau lens 6 by the second and third deflection mirrors 5b and 5c, and the lens to be measured is Enables interference measurement from the back side of 1.

It should be noted that it is possible to use two interferometer bodies so as to simultaneously measure from both front and back sides of the lens 1 to be tested. Further, the reason for performing the measurement from the back surface side of the lens 1 to be inspected using the second Fizeau lens 6 is that the folding mirror is accurately aligned, the focal length of the secondary aspheric surface other than the paraboloid is measured, and Is for use in center thickness measurement and the like.

In this embodiment, the second Fizeau lens 6
Is removed from the optical axis, and the corner cube 7b is installed on the optical axis on the back side of the lens 1 to be inspected. The measurement light of the laser length measuring device 7a passes through the opening provided in the second deflection mirror 5b as shown in FIG. 2 (a) and is incident on the corner cube 7b. Second Fizeau lens 6
A shutter mechanism 8 is provided immediately in front of the laser length-measuring device 7a in order to block the laser beam for length-measuring when the is used. However, this may be switching between insertion and removal of the second deflection mirror 5b. . Further, the insertion and removal of the opening and the mirror need not be limited to the second deflecting mirror 5b.

If the corner cube 7b is not installed on the optical axis, but a mechanism for measuring the length at at least two positions symmetrical with respect to the optical axis is adopted, and the average value is used to substitute the value on the optical axis. ,
It is possible to reduce the Abbe error without removing the second Fizeau lens 6. Now, Fig. 5 (b)
Then, the lens to be inspected 1 is moved to a position where the lens to be inspected 1 forms apex reflection with respect to the first Fizeau lens 3 by a moving mechanism (not shown). By moving at least one of the Fizeau lens 3 and the second Fizeau lens 6 and detecting the moving amount of the Fizeau lens by the detecting means 7.
The focal length of the next aspherical surface 1a may be measured. At this time, if the above-mentioned averaging method is adopted, the measurement length can be easily arranged even with the combination of the laser length measuring device 7a and the corner cube 7b.

In FIG. 2A, the optical axis of the interferometer body 2 coincides with the traveling direction of the laser light and is defined by the reference mirror 2a provided inside the interferometer body 2. The alignment of the first Fizeau lens 3 and the second Fizeau lens 6 is performed by causing the internal reference mirror 2a and the Fizeau surface of each Fizeau lens to interfere with each other by Twyman Green.

Regarding the accuracy of the moving axis of the moving mechanism (not shown) for moving the lens 1 to be inspected to the position of FIG. 1B in the optical axis direction, the accuracy of the moving axis of the second Fizeau lens 6 is the same as that of the second Fizeau lens 6. The same can be said. As a fourth embodiment of the present invention, although not shown, an example of eccentricity measurement when at least one surface of the lens to be inspected is a high-order aspherical surface (aspherical surface including a high-order aspherical surface component) is given. The measuring device has the same configuration as that of FIG. 1 or FIG. As the method for measuring the aspherical whole surface data, the method disclosed in “Folding interference device” of the present application and the simultaneous application may be applied.

As an example of the definition of the aspherical surface axis of the higher-order aspherical surface, the entire surface data once obtained is divided into annular zones so that there is no overlapping portion, and the optimal approximate spherical surface of each annular zone data is calculated. A method of defining from the point sequence of the ball center can be considered. The verification of the calculation method that uniquely calculates the aspherical surface axis from this sequence of points, when applied to the secondary aspherical surface, determines the degree of agreement with the secondary aspherical surface axis that is uniquely determined by the folding measurement of the secondary aspherical surface. It becomes possible by seeing.

As a fifth embodiment of the present invention, use of an infrared interferometer as the interferometer main body 2 of FIG. 1 can be considered. Also in this case, it is possible to deal with the secondary aspherical surface and the high-order aspherical surface. Further, there is an advantage that even if at least one surface of the lens to be inspected is a rough surface having a large surface roughness such as a ground surface, it is possible to deal with it. For example, when manufacturing a high-order aspherical lens with one surface having a high-order aspherical surface and one surface having a spherical surface, the polished spherical surface is aligned with a visible interferometer, and the aspherical surface during grinding is aligned with an infrared interferometer. Eccentricity can be easily measured. The same applies to both surfaces even if they are high-order aspherical surfaces and rough surfaces.

As a sixth embodiment of the present invention, a case where the eccentricity of an aspherical lens having at least one aspherical surface is measured by so-called "ref subtraction" with Ref, whose eccentricity is measured accurately in advance, as a reference. explain. First, by performing surface accuracy measurement on both sides of Ref with an interferometric measurement system,
The relative position of the interferometric measurement system in that measurement state is calibrated. After that, Ref is replaced with the lens under test without moving the interferometric measurement system, and the surface accuracy of both surfaces of the lens under test is measured.
The eccentricity of the test lens can be measured by specifying the positional relationship between both surfaces of the test lens.

In this case, in addition to the fact that a moving mechanism is not required, once the calibration by Ref is performed, the eccentricity of the lens to be inspected having the same shape can be easily measured. In addition to requiring accurate measurement of Ref, accurate alignment error correcting means as disclosed in Japanese Patent Application No. 7-32579 is indispensable in order to specify the accurate positional relationship. Become.

[0040]

As described above, when the eccentricity measuring device according to the present invention is adopted, the eccentricity of the secondary aspherical lens can be measured by using the entire surface information of the aspherical surface. Also, if the distance measurement on the optical axis of the secondary aspherical lens is also used,
It is also possible to measure the power component of the secondary aspherical surface.

Further, it becomes possible to easily deal with the eccentricity measurement of the secondary aspherical lens whose both surfaces are secondary aspherical surfaces.

[Brief description of drawings]

FIG. 1 shows a principle diagram according to the present invention, which is a first embodiment.

FIG. 2 shows a first modification of the first embodiment according to the present invention.

FIG. 3 shows a second modification of the first embodiment according to the present invention.

FIG. 4 shows a second embodiment according to the present invention.

FIG. 5 shows a third embodiment according to the present invention.

[Explanation of symbols]

 1 ... Lens to be tested 1a ... Surface to be tested (hyperboloid) 1b ... Spherical surface 2 ... First interferometer body 2a ... Internal reference mirror 3 ... First Fizeau lens (condensing lens) 3a ... Fizeau surface 4 ... Folding mirror 5 ... Deflection mirror 6 ... Second Fizeau lens (condensing lens) 7 ...・ Detecting means 7a ・ ・ ・ ・ Laser measuring device 7b ・ ・ ・ ・ Corner cube 8 ・ ・ ・ ・ Shutter 9 ・ ・ ・ ・ Rotating mechanism 10 ・ ・ ・ ・ Second interferometer body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeo Mihasatsuike Ike 3-3, Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (1)

[Claims] 1. An interferometer main body, a condensing lens for converting a plane wave emitted from the interferometer main body into a spherical wave, and a focal point of a secondary aspherical surface forming a lens to be inspected. A first holding and adjusting mechanism for holding and adjusting the lens to be inspected so as to match the imaging point; and a folding mirror for reflecting a plane wave or a spherical wave which is reflected light from the secondary aspherical surface. , A second holding adjustment mechanism for holding and adjusting the folding mirror so that the reflected light from the folding mirror is imaged again at the imaging point, and for measuring interference from the back side of the lens to be tested. An interferometer measuring system, a "moving mechanism for moving the interferometric measuring system in the measurement optical axis direction, or a rotating mechanism for rotating the lens under test around the measurement optical axis", the interferometer body, and For processing the measurement data of the interferometry system An eccentricity measuring device comprising an arithmetic device.